Magnetic Resonance Imaging (MRI)

CMS NCA document | source_status=Closed | review_type=2nd Recon | public_comment_open=False | document_id=CAG-00399R2

The Centers for Medicare & Medicaid Services (CMS) has determined that the evidence is not adequate to conclude that the use of magnetic resonance imaging (MRI) improves health outcomes for Medicare beneficiaries with implanted permanent pacemakers (PMs) or implantable cardioverter defibrillators (ICDs), and thus we determine that it is not reasonable and necessary under §1862(a)(1)(A) of the Social Security Act (the Act). Therefore, subject to one exception, we will retain the current general contraindications at Chapter 1, Section 220.2.C.1 in the NCD Manual. CMS believes that the evidence is promising although not yet convincing that MRI will improve patient health outcomes if certain safeguards are in place to ensure that the exposure of the device to an MRI environment adversely affects neither the interpretation of the MRI result nor the proper functioning of the implanted device itself. We believe that specific precautions (listed below) could maximize benefits of MRI exposure for beneficiaries enrolled in clinical studies designed to assess the utility and safety of MRI exposure. Therefore, CMS determines that MRI will be covered by Medicare when studied in a clinical study under § 1862(a)(1)(E) (consistent with § 1142 of the Act) if the study meets the criteria in each of the three paragraphs below. The approved prospective clinical study must, with appropriate methodology, address one or more aspects of the following questions: Do results of MRI in PM/ICD beneficiaries with implanted cardiac devices affect physician decision making related to: Clinical management strategy (e.g., in oncology, toward palliative or curative care); Planning of treatment interventions; or Prevention of unneeded diagnostic studies or interventions, or preventable exposures? Do results of MRI in PM/ICD beneficiaries with implanted cardiac devices affect patient outcomes related to: Survival; Quality of life; or Adverse events during and after MR scanning? In addition, the prospective clinical study of MRI must include safety criteria for all participants. Such required safety measures for such studies, as further explained in guidance documents from professional societies (e.g., Kanal et al., 2007; Levine et al., 2007), must include but are not limited to: MRI should be done on a case-by-case and site-by-site basis. MRI scan sequences, field intensity, and field(s) of exposure should be selected to minimize risk to the patient while gaining needed diagnostic information for diagnosis or for managing therapy. MRI scanning should be done only if the site is staffed with individuals with the appropriate radiology and cardiology knowledge and expertise on hand. Implanted device patients who are candidates for recruitment for an MRI clinical study should be advised that life-threatening arrhythmias might occur during MRI and serious device malfunction might occur, requiring replacement of the device. Radiology and cardiology personnel and a fully stocked crash cart be readily available throughout the procedure in case a significant arrhythmia develops during the examination that does not terminate with the cessation of the MR study. The cardiologist should be familiar with the patient’s arrhythmia history and the implanted device. A programmer that can be used to adjust the device as necessary should be readily available. All such patients should be actively monitored for cardiac and respiratory function throughout the examination. At a minimum, ECG and pulse oximetry should be used. Visual and verbal contact with the patient must be maintained throughout the MRI scan. The patient should be instructed to alert the MRI staff on hand to any unusual sensations, pains, or to any problems. At the conclusion of the examination, the cardiologist should examine the device to confirm that the function is consistent with its preexamination state. Follow-up should include a check of the patient’s device at a time remote (1–6 weeks) after the scan to confirm appropriate function. If the implanted device manufacturer has indicated additional safety precautions appropriate for safe MRI performance, these must be included in the study protocol. The clinical study must adhere to the following standards of scientific integrity and relevance to the Medicare population. The principal purpose of the research study is to test whether a particular intervention potentially improves the participants’ health outcomes. The research study is well supported by available scientific and medical information or it is intended to clarify or establish the health outcomes of interventions already in common clinical use. The research study does not unjustifiably duplicate existing studies. The research study design is appropriate to answer the research question being asked in the study. The research study is sponsored by an organization or individual capable of executing the proposed study successfully. The research study is in compliance with all applicable Federal regulations concerning the protection of human subjects found at 45 CFR Part 46. If a study is regulated by the Food and Drug Administration (FDA), it must be in compliance with 21 CFR Parts 50 and 56. All aspects of the research study are conducted according to appropriate standards of scientific integrity (see http://www.icmje.org ). The research study has a written protocol that clearly addresses, or incorporates by reference, the standards listed here as Medicare requirements for coverage with evidence development (CED). The clinical research study is not designed to exclusively test toxicity or disease pathophysiology in healthy individuals. Trials of all medical technologies measuring therapeutic outcomes as one of the objectives meet this standard only if the disease or condition being studied is life threatening as defined in 21 CFR § 312.81(a) and the patient has no other viable treatment options. The clinical research study is registered on the ClinicalTrials.gov website by the principal sponsor/investigator prior to the enrollment of the first study subject. The research study protocol specifies the method and timing of public release of all prespecified outcomes to be measured including release of outcomes if outcomes are negative or study is terminated early. The results must be made public within 24 months of the end of data collection. If a report is planned to be published in a peer reviewed journal, then that initial release may be an abstract that meets the requirements of the International Committee of Medical Journal Editors ( http://www.icmje.org ). However a full report of the outcomes must be made public no later than three (3) years after the end of data collection. The research study protocol must explicitly discuss subpopulations affected by the treatment under investigation, particularly traditionally underrepresented groups in clinical studies, how the inclusion and exclusion criteria effect enrollment of these populations, and a plan for the retention and reporting of said populations on the trial. If the inclusion and exclusion criteria are expected to have a negative effect on the recruitment or retention of underrepresented populations, the protocol must discuss why these criteria are necessary. The research study protocol explicitly discusses how the results are or are not expected to be generalizable to the Medicare population to infer whether Medicare patients may benefit from the intervention. Separate discussions in the protocol may be necessary for populations eligible for Medicare due to age, disability or Medicaid eligibility. Consistent with section 1142 of the Act, the Agency for Healthcare Research and Quality (AHRQ) supports clinical research studies that CMS determines meet the above-listed standards and address the above-listed research questions.

Decision Memo: To: Administrative File CAG-00399R2 From: Louis B. Jacques, MD Director, Coverage and Analysis Group Tamara Syrek Jensen, JD Deputy Director, Coverage and Analysis Group James Rollins, MD, PhD Director, Division of Items and Devices Brijet Burton, MPP, MS, PA-C Lead Analyst, Division of Items and Devices Sarah Meisenberg Analyst, Division of Items and Devices Leslye Fitterman, PhD Epidemiologist, Analyst, Division of Items and Devices Rosemarie Hakim, PhD Epidemiologist, Division of Operations and Information Management Jeffrey C. Roche, MD, MPH Medical Officer, Division of Items and Devices Subject: Final Decision Memorandum of Magnetic Resonance Imaging Date: February 24, 2011 I. Final Decision: The Centers for Medicare & Medicaid Services (CMS) has determined that the evidence is not adequate to conclude that the use of magnetic resonance imaging (MRI) improves health outcomes for Medicare beneficiaries with implanted permanent pacemakers (PMs) or implantable cardioverter defibrillators (ICDs), and thus we determine that it is not reasonable and necessary under §1862(a)(1)(A) of the Social Security Act (the Act). Therefore, subject to one exception, we will retain the current general contraindications at Chapter 1, Section 220.2.C.1 in the NCD Manual. CMS believes that the evidence is promising although not yet convincing that MRI will improve patient health outcomes if certain safeguards are in place to ensure that the exposure of the device to an MRI environment adversely affects neither the interpretation of the MRI result nor the proper functioning of the implanted device itself. We believe that specific precautions (listed below) could maximize benefits of MRI exposure for beneficiaries enrolled in clinical studies designed to assess the utility and safety of MRI exposure. Therefore, CMS determines that MRI will be covered by Medicare when studied in a clinical study under § 1862(a)(1)(E) (consistent with § 1142 of the Act) if the study meets the criteria in each of the three paragraphs below. The approved prospective clinical study must, with appropriate methodology, address one or more aspects of the following questions: Do results of MRI in PM/ICD beneficiaries with implanted cardiac devices affect physician decision making related to: Clinical management strategy (e.g., in oncology, toward palliative or curative care); Planning of treatment interventions; or Prevention of unneeded diagnostic studies or interventions, or preventable exposures? Do results of MRI in PM/ICD beneficiaries with implanted cardiac devices affect patient outcomes related to: Survival; Quality of life; or Adverse events during and after MR scanning? In addition, the prospective clinical study of MRI must include safety criteria for all participants. Such required safety measures for such studies, as further explained in guidance documents from professional societies (e.g., Kanal et al., 2007; Levine et al., 2007), must include but are not limited to: MRI should be done on a case-by-case and site-by-site basis. MRI scan sequences, field intensity, and field(s) of exposure should be selected to minimize risk to the patient while gaining needed diagnostic information for diagnosis or for managing therapy. MRI scanning should be done only if the site is staffed with individuals with the appropriate radiology and cardiology knowledge and expertise on hand. Implanted device patients who are candidates for recruitment for an MRI clinical study should be advised that life-threatening arrhythmias might occur during MRI and serious device malfunction might occur, requiring replacement of the device. Radiology and cardiology personnel and a fully stocked crash cart be readily available throughout the procedure in case a significant arrhythmia develops during the examination that does not terminate with the cessation of the MR study. The cardiologist should be familiar with the patient’s arrhythmia history and the implanted device. A programmer that can be used to adjust the device as necessary should be readily available. All such patients should be actively monitored for cardiac and respiratory function throughout the examination. At a minimum, ECG and pulse oximetry should be used. Visual and verbal contact with the patient must be maintained throughout the MRI scan. The patient should be instructed to alert the MRI staff on hand to any unusual sensations, pains, or to any problems. At the conclusion of the examination, the cardiologist should examine the device to confirm that the function is consistent with its preexamination state. Follow-up should include a check of the patient’s device at a time remote (1–6 weeks) after the scan to confirm appropriate function. If the implanted device manufacturer has indicated additional safety precautions appropriate for safe MRI performance, these must be included in the study protocol. The clinical study must adhere to the following standards of scientific integrity and relevance to the Medicare population. The principal purpose of the research study is to test whether a particular intervention potentially improves the participants’ health outcomes. The research study is well supported by available scientific and medical information or it is intended to clarify or establish the health outcomes of interventions already in common clinical use. The research study does not unjustifiably duplicate existing studies. The research study design is appropriate to answer the research question being asked in the study. The research study is sponsored by an organization or individual capable of executing the proposed study successfully. The research study is in compliance with all applicable Federal regulations concerning the protection of human subjects found at 45 CFR Part 46. If a study is regulated by the Food and Drug Administration (FDA), it must be in compliance with 21 CFR Parts 50 and 56. All aspects of the research study are conducted according to appropriate standards of scientific integrity (see http://www.icmje.org ). The research study has a written protocol that clearly addresses, or incorporates by reference, the standards listed here as Medicare requirements for coverage with evidence development (CED). The clinical research study is not designed to exclusively test toxicity or disease pathophysiology in healthy individuals. Trials of all medical technologies measuring therapeutic outcomes as one of the objectives meet this standard only if the disease or condition being studied is life threatening as defined in 21 CFR § 312.81(a) and the patient has no other viable treatment options. The clinical research study is registered on the ClinicalTrials.gov website by the principal sponsor/investigator prior to the enrollment of the first study subject. The research study protocol specifies the method and timing of public release of all prespecified outcomes to be measured including release of outcomes if outcomes are negative or study is terminated early. The results must be made public within 24 months of the end of data collection. If a report is planned to be published in a peer reviewed journal, then that initial release may be an abstract that meets the requirements of the International Committee of Medical Journal Editors ( http://www.icmje.org ). However a full report of the outcomes must be made public no later than three (3) years after the end of data collection. The research study protocol must explicitly discuss subpopulations affected by the treatment under investigation, particularly traditionally underrepresented groups in clinical studies, how the inclusion and exclusion criteria effect enrollment of these populations, and a plan for the retention and reporting of said populations on the trial. If the inclusion and exclusion criteria are expected to have a negative effect on the recruitment or retention of underrepresented populations, the protocol must discuss why these criteria are necessary. The research study protocol explicitly discusses how the results are or are not expected to be generalizable to the Medicare population to infer whether Medicare patients may benefit from the intervention. Separate discussions in the protocol may be necessary for populations eligible for Medicare due to age, disability or Medicaid eligibility. Consistent with section 1142 of the Act, the Agency for Healthcare Research and Quality (AHRQ) supports clinical research studies that CMS determines meet the above-listed standards and address the above-listed research questions. II. Background Information As noted in prior NCDs on this topic, an MRI “(formerly known as nuclear magnetic resonance imaging - NMRI) is a noninvasive method of graphically representing the distribution of water and other hydrogen-rich molecules in the human body.” MRI is a diagnostic imaging modality that is capable of demonstrating a wide variety of soft-tissue lesions with contrast resolution equal or superior to CT scanning in various parts of the body. Among its advantages are the absence of ionizing radiation and the ability to achieve high levels of tissue contrast resolution without injected iodinated radiological contrast agents. However, MRI exposes the patient to strong magnetic fields which may cause the movement or heating of implanted medical devices that are ferromagnetic (e.g. surgical clips) or that have ferromagnetic components (e.g. pacemakers, prostheses.) The American College of Radiology (ACR’s) guidance document on safe MR Practices (Kanal 2007) explicitly speaks to the need to address the possibility that the patient may have ferromagnetic foreign bodies or implants. Authors have described the effects of intense and high-frequency magnetic fields on ferromagnetic or conducting objects. For example, a review of pacemaker malfunction (Hayes and Vlietstra, 1993) notes that “… exposure to MRI causes pacemakers to revert to an asynchronous mode (in which impulse generation by the pacemaker occurs at a fixed rate, independent of underlying cardiac activity). This effect can be avoided only in PMs in which the magnet response can be programmed ‘off’.” The review’s authors suggested use of other techniques to allow safe MR scanning of non-PM-dependent patients. These authors also note that “… [i]f the body area to be imaged is in close proximity to the pacemaker site, the pacemaker-induced artifact on MRI may obscure the images.” A later review article (Schoenfeld, 2007) states that “…(p)otential interactions (of PMs) with MRI include pacing inhibition, inappropriate ICD discharges, rapid pacing, mechanical pull and rotation of the device, and device reprogramming,” and suggests strategies to improve safety of MR scanning for patients with PMs and ICDs: “…Certain strategies to minimize complications have been suggested, including the use of less powerful MRI machines; imaging limited to extremities (i.e., remote from the implanted device); careful reprogramming of the intracardiac device, including asynchronous modes and maximal pacing output; selection of appropriate spin sequences; limitation of MRI to patients who are not pacemaker dependent; and careful, continuous periprocedure monitoring.” III. History of Medicare Coverage Section 220.2 of Chapter 1 of the Medicare National Coverage Determination (NCD) Manual provides coverage of MRI for a number of clinical indications. Coverage is limited to MRI instruments that have received FDA premarket approval, and such units must be operated within the parameters specified by the approval. In addition (and as noted by the requester), payment for an MRI examination is not currently covered by Medicare if certain contraindications are present. These include cardiac PMs (as indicated in the following section of the Medicare NCD Manual, Chapter 1, Section 220.2.C.1, as downloaded by CMS staff on November 2, 2010): C. Contraindications and Nationally Non-Covered Indications 1. Contraindications "The MRI is not covered when the following patient-specific contraindications are present: It is not covered for patients with cardiac pacemakers or with metallic clips on vascular aneurysms. MRI during a viable pregnancy is also contraindicated at this time. The danger inherent in bringing ferromagnetic materials within range of MRI units generally constrains the use of MRI on acutely ill patients requiring life support systems and monitoring devices that employ ferromagnetic materials. … (Source: Medicare On-line NCD Manual, available at www.cms.hhs.gov ). Specific conditions for Medicare coverage of MRI, including deletion of prior contraindications, have changed during the past 25 years. In November 1985, CMS first set forth the conditions under which MRI may be covered. Subsequent policy revisions in 1988, 1991, and 1994 provided MRI coverage under Medicare for additional conditions. Currently covered indications for MRI include examination of the head, central nervous system, and spine. MRI can also assist in the differential diagnosis of mediastinal and retroperitoneal masses, including abnormalities of the large vessels such as aneurysms and dissections. MRI may also be used to detect and stage pelvic and retroperitoneal neoplasms and to evaluate disorders of cancellous bone and soft tissues. MRI may also be covered to diagnose disc disease without regard to whether radiological imaging has been tried first to diagnose the problem. Most recently, a 2009 NCD removed a contraindication from 220.2.C.2 concerning blood flow measurement. Other uses of MRI for which CMS has not specifically indicated national coverage are under local contractor discretion. A. Current Request for Reconsideration CMS received a letter dated June 25, 2010 from Dr. Robert J. Russo, MD, PhD, FACC, Scripps Clinic, LaJolla, California requesting reconsideration of Section 220.2’s contraindications for MRI. The requester asked that the current Medicare coverage for MRI be changed, both to remove a contraindication for patients who undergo MRI and who had implanted PMs, as well as to provide Medicare coverage for patients who undergo MRI and who had implanted ICDs, if (1) a clinically-indicated MRI is performed as part of a prospective clinical study designed to determine the risk of the procedure, and (2) the study is conducted after an IDE has been approved by FDA for a device involved in the proposed research. The requester’s concerns can be summarized as follows. Millions of patients in the United States currently have implanted pacemakers or other devices. The estimated lifetime risk of requiring an MRI is 50-75% (Requester’s reference #4). Medicare currently contraindicates coverage of MRI in patients with implanted pacemakers. In the absence of Medicare coverage, beneficiaries for whom MRI is the most appropriate diagnostic imaging modality may be denied access to MRI. Absent an exception to the existing contraindication to MRI coverage in patients with implanted pacemakers, clinical trials to determine safety may be infeasible. B. Benefit Category Medicare is a defined benefit program. An item or service must fall within a benefit category as a prerequisite to Medicare coverage §1812 (Scope of Part A); §1832 (Scope of Part B) and §1861(s) (Definition of Medical and Other Health Services) of the Act. Magnetic resonance imaging is considered to be within the following benefit category: other diagnostic tests §1861(s)(3). Medicare regulations at 42 CFR 410.32(a) state in part, that "…diagnostic tests must be ordered by the physician who is treating the beneficiary, that is, the physician who furnishes a consultation or treats a beneficiary for a specific medical problem and who uses the results in the management of the beneficiary’s specific medical problem." Thus, except where other uses have been explicitly authorized by statute, Medicare does not cover MRI for routine screening or surveillance. IV. Timeline of Recent Activities Date Action June 28, 2010 The request letter and list of references was sent by Dr. Russo to CMS. CMS posts a tracking sheet and opens a National Coverage Reconsideration to determine if there is sufficient evidence to change the policy. The initial 30-day public comment period begins. July 28, 2010 Initial public comment period ended. CMS received a total of 3 comments. December 1, 2010 CMS posts the proposed decision memorandum for 30 days of public comment period. December 31, 2010 The public comment period on the proposed decision memo closes with five public comments received. V. FDA Status Wenote that the FDA status of the MRI scanner was not a specific issue raised by the requester. FDA approved the first pacemaker (Medtronic Revo MRI SureScan TM Pacing System) for use during certain MRI exams on February 8, 2011. This approval came after the public comment period, required by section 1862(l) of the Act, and was too late for CMS to adequately review the evidence to address coverage for MRI for patients that may obtain this device. VI. General Methodological Principles When making NCDs, CMS normally evaluates relevant clinical evidence to determine whether or not the evidence is of sufficient quality to support a finding that an item or service falling within a benefit category is reasonable and necessary for the diagnosis or treatment of illness or injury or to improve the functioning of a malformed body member. The critical appraisal of the evidence enables us to determine to what degree we are confident that: 1) the specific assessment questions can be answered conclusively; and 2) the intervention will improve health outcomes for beneficiaries. An improved health outcome is one of several considerations in determining whether an item or service is reasonable and necessary. Public commenters sometimes cite the published clinical evidence and provide CMS with useful information. Public comments that provide information based on unpublished evidence, such as the results of individual practitioners or patients, are less rigorous and, therefore, less useful for making a coverage determination. CMS uses the initial comment period to inform the public of its proposed decision. CMS responds in detail to the public comments that were received in response to the proposed decision when it issues the final decision memorandum. VII. Evidence Below is a summary of the evidence we reviewed. CMS may consider published articles submitted by the requester either as sources of evidence, or for background and general information. Though we reconsidered MRI in 2009, the underlying questions are different in this reconsideration and thus we are considering a broader body of evidence this time. A. Introduction A review article (Nazarian and Halperin 2009) summarizes the findings of eight clinical studies, published from 1996 - 2006, of effects of clinical MR scans in patients with PMs or ICDs. A total of 31 patients with ICDs and 261 patients with PMs underwent MR scanning with field strengths from 0.5 to 2.0 T. It was noted that: some electrical characteristics of the PM or ICD may change after MR scans; PM reprogramming was needed in less than 2% of patients in one study; and occasional device-associated artifacts were noted on MRI images. Some studies used special ‘safety’ protocols to avoid MR scan interference with device function, as well as close patient monitoring during the scan. Any of these effects of MRI on an implanted cardiac device might affect the patient’s health outcomes, especially among patients who depend on the device to monitor and (if needed) correct an aberrant heart rhythm, e.g., to recognize and stop ventricular fibrillation (VF), an extremely serious arrhythmia. The American Heart Association (AHA) (Levine 2007) recognized the challenges of safe MR scanning in patients with implanted electrically active cardiac devices and/or with ferromagnetic foreign bodies or implants, among others. In addition to the risk of MR scanning to change PM or ICD function, the presence of metallic implanted devices can affect the accuracy of MR images. The Nazarian and Halperin 2009 article mentions reports of several types of such artifacts, including image distortion, signal voids or bright areas, and poor fat suppression. According to these authors, such image artifacts are more pronounced in certain types of MR examinations, including inversion recovery and steady-state free precession sequences. Such misleading artifacts may, in certain imaging applications such as cardiac MRI, suggest scarring or other tissue abnormalities, and lead to misinterpretation. However, according to these authors, such artifacts can be reduced by advance planning, patient positioning and scan processing adjustments. We opened this NCA to review the evidence on the use of MRI in patients who have implanted PM or ICD devices. This NCA does not focus on the use of MRI for any particular indication, i.e., for any specific disease(s) or condition(s). B. Discussion of Evidence Reviewed 1. Questions In assessing the evidence regarding this topic, CMS formulated two questions similar to those used in prior decisions relating to this topic area (for example, in the decision memorandum regarding the initial reconsideration for MRI, CAG-00399R (September 2009)). Q1. Is there adequate evidence to conclude that MRI performed for clinically appropriate imaging indications informs the diagnosis or clinical management decisions in patients with implanted PMs or ICDs? Q2. Is there adequate evidence to conclude that MRI performed for clinically appropriate imaging indications improves health outcomes in patients with implanted PMs or ICDs? We recognize that improvements in health outcomes may arise from changes in physician management of the patient’s condition, brought about through thoughtful consideration of the results of diagnostic testing. We also searched for indications in qualifying clinical studies of safety concerns or adverse events in participants with implanted devices undergoing MRI. We considered this prudent in view of known adverse events to which subjects might be vulnerable. As has been done in other decisions, CMS considered the evidence in the hierarchical framework of Fryback and Thornbury (1991) where Level 2 addresses diagnostic accuracy, sensitivity, and specificity of the test; Level 3 focuses on whether the information produces change in the physician's diagnostic thinking; Level 4 concerns the effect on the patient management plan and Level 5 measures the effect of the diagnostic information on patient outcomes. 2. External Technology Assessments CMS did not request an external technology assessment (TA) on this issue. 3. Internal Technology Assessment Articles submitted by the requestor: Prospective Case Series Del Ojo JL, Moya F, Villalba J, et al. Is magnetic resonance imaging safe in cardiac pacemaker recipients? Pacing & Clinical Electrophysiology. Apr 2005; 28(4): 274-278. The stated purpose of this prospective case series study was to evaluate the safety of MRI. Participants included 13 subjects (10 males and 3 females), ranging in age from 59 to 79 years, with a median age of 71 years. Inclusion criteria were: patients had to have an implanted PM (Affinity ™ DR model 5330 PMs (St. Jude Medical) connected to a Tendril ™ model 1388 leads (St. Jude Medical)), and a clinical indication for MRI. Among these thirteen patients, the indications for PM implantation included sinus node disease (n = 7) and atrioventricular block (n=6). Prior to MRI, all patients displayed a stable spontaneous rhythm and were not considered PM-dependent. The study’s three objectives were to (1) reassess risks of performing an MR scan in PM patients; (2) compare pacing functions before and after the exposure to the MR environment; and (3) monitor the development of possible adverse effects. During MR scanning, stimulation and sensing polarity were programming to bipolar for each PM. Sensor, magnet and AutoCapture TM functions were programmed off, and other PM functions were allowed to remain enabled if originally enabled in that patient’s device. Outcomes of interest included both (1) pre- to post-MR scan changes in electrical characteristics of PM; and (2) occurrence of any adverse events during or after MRI in patients with PM, based on post-MR interviews with patients and on post-MR interrogation of the PM. Results of the study revealed the absence of PM inhibition, asynchronous pacing, or inappropriately rapid pacing. Each patient underwent thoracic MRI at 2.0 T. Eight patients also underwent head (n = 3); cervical spine (n = 2); neck (n = 2); and lumbar spine (n = 1) scanning in addition to the thoracic MR scan. During the study, no patient reported discomfort, heat, or motion sensation at the PM implant site. And based on post-MR scan interrogation of the PM function, there were no significant differences in the sensing, stimulation, AutoCapture™ threshold, and lead impedance measurements before and after MR scans. The authors concluded that performing 2.0 T-MR scans in patients with Affinity™ DR model 5330 PM connected to a Tendril™ model 1388 lead is safe. Gimbel JR, Johnson D, Levine PA, et al. Safe performance of MRI on five patients with permanent cardiac PMs. Pacing Clin Electrophysiol 1996; 19(6): 913-9. The purpose of this prospective case series study was to evaluate a strategy to allow safe MR scan in patients with implanted PMs. Five patients, whose age and gender information were not provided, all had implanted PMs of different models from a single manufacturer (Pacesetter, Sylmar, CA). Patients were eligible for the study if their physician had ordered an MR scan, for: brain or pituitary scan (n = 2); cervical disk (n = 1); heart valve (n = 1); or “CIA” (n = 1). One participant was described as ‘PM dependent,’ a condition defined as having an escape rhythm that was hemodynamically unstable. During the MR scan, patients were monitored using electrocardiogram (ECG) signals (n = 3), pulse oximetry (n=1), or by verbal contact with a nurse stationed nearby. A ‘heavy dressing’ was applied over the PM implant pocket in four patients, at the discretion of the attending physician, in order to minimize the torque effect for patient comfort. The study was designed to also include a post-MR scan, in which the PM was interrogated and device reprogramming would be performed at the discretion of the attending physician. Follow-up at three months post-MR scan would also be performed to assess capture and sensing thresholds. Results of the study revealed that MR scans were conducted at between 0.35 – 1.5 T. When questioned about any sensations noted during the MR scan one patient noted that her “heart stopped beating toward the end of the scan.” No twisting or heating sensations or any other unusual symptoms were reported during or immediately after MR scans. Pre-MR scan, the PM was interrogated. No changes occurred to the programmed or measured parameters of the devices tested. Pacing and sensing thresholds remained the same as those recorded before the MR scan. In the only patient for whom the device’s event record was available, normal pacemaker function was noted during the scan. MR image results from four out of five patients were described as ‘excellent.’ However, in one case, artifact from the PM ‘compromised’ the MR image for evaluating the patient’s cardiac valve. The authors concluded that “(w)hen appropriate strategies are used our experience suggests that MRI may be performed, when necessary, with an acceptable risk / benefit ratio to the patient.” Naehle CP, Strach K, Thomas D, et al. Magnetic Resonance Imaging at 1.5-T in Patients With Implantable Cardioverter-Defibrillators. J Am Coll Cardiol 2009; 54: 549–55. The purpose of this prospective case series was to evaluate a strategy for safe performance of MR scanning at 1.5 T. The study included 18 patients who had been implanted with ICDs for at least three months prior to enrolling in the study. The patients’ mean age was 61.8 years (range: 35-84 years); gender information was not provided. Inclusion criteria included: (1) urgent need for an MRI examination; (2) presence of an ICD system, with at least six months’ estimated battery life; (3) pacing lead impedances 200 to 2,000 ohms; (4) shock lead impedance 10 to 80 ohms; (5) stable pacing parameters: pacing capture threshold < 2.5 V at a pulse duration of 0.4 ms; sensing > 5 mV; and (6) a minimum of three months since ICD and lead implantation. Exclusion criteria included: (1) unstable angina; (2) myocardial infarction or cardiothoracic surgery within the previous three months; (3) pacemaker dependency (defined as an intrinsic heart rate less than 50 beats/min); (4) presence of MRI incompatible bioimplants or other MRI incompatible materials, or presence of abandoned leads. The manufacturers of the implanted ICDs in these patients were: Medtronic (n = 8); Guidant (n = 4); Biotronik (n = 3); and other (n = 3). The protocol evaluated consisted of reprogramming of ICD pre-MR scan, as per protocol; 1.5 T MR scan; patient symptom report during MR scan; pre- and post-scan sampling of patient troponin level; pre- and post-scan ICD interrogation; ICD reprogramming post-MR to baseline; and three month follow-up. Results of the study revealed absence of any of the following: MR scan termination; patient-reported sensations; heart rate or rhythm variations or arrhythmias; or electrical reset of ICDs. For troponin levels, there was no significant pre- to post-MR scan change by Student’s T test, and there was no elevation above the indicated upper limit of the reference interval (i.e., 0.1 ng/mL). Finally, two parameters were reported to change significantly (by the Wilcoxon signed rank test) in the pre-MR scan to post-MR scan comparisons: (1) mean battery voltage (“3.86 +/- 1.48 Volts (‘V’) pre-MR to 3.83 +/- 1.48 V post-MR”); and (2) mean capacitor charging time (from 11.2 +/- 4.9 seconds pre-MR scan to 9.5 +/- 4.28 seconds post-MR scan) (all from Table 4)). The authors concluded that “MRI of non–pacemaker-dependent ICD patients can be performed with an acceptable risk/benefit ratio under controlled conditions by taking both MRI- and pacemaker-related precautions.” Nazarian S, Bluemke DA, Lardo AC, et al. Clinical Utility and Safety of a Protocol for Noncardiac and Cardiac MRI of Patients With PMs and ICDs at 1.5 Tesla. Circulation. 2006; 114: 1277-84. In this prospective case series involving 55 patients, the authors assessed the immediate and long-term safety of MRI protocol for patients with permanent PM or ICD and the diagnostic yield of MRI in this setting. Thirty-one of the 55 patients had an implanted PM (with 12 of the 31 PM-dependent) and 24 of the 55 had an implanted ICD. Age and gender information about participants was not provided. Inclusion criteria included any clinical indication for MRI with no acceptable imaging alternative and an implanted cardiac device if the PM or ICD had been found to be safe by previous in vitro phantom and in vivo animal testing. Exclusion criteria were patients with device implantation less than six weeks before MRI and patients with nontransvenous epicardial leads, no fixation (such as superior vena cava coil), or abandoned leads. The 55 enrollees underwent a total of 68 MR scans. The main outcomes of interest included: changes in electrical characteristics of PMs, ICDs and ability of MR scan images to answer clinical questions pertaining to diagnostic yield. All patients underwent at least one MR scan with safety protocol and concurrent monitoring. For each scan, pre- and post-scan interrogations of implanted devices and long-term follow-up were performed. In addition, images from MR scans were reviewed. Results of the study revealed: (1) no symptoms consistent with device movement, torque, or heating were reported during MRI examinations; (2) no inappropriate inhibition of pacing was observed during MRI. In ten patients with permanent PMs without magnet-mode programming capability, reed switch activation by the static magnetic field of MR scanning led to transient asynchronous pacing at the device-specific magnet rate (85 pulses/minute), which ceased on patient positioning in the magnet bore; (3) no unexpected or rapid activation of pacing was observed during MR scanning; (4) all devices were functioning appropriately after MR scans, and no changes in device programming were observed; (5) twenty-nine of the participants had chronic device interrogation with median follow-up time of 99 days. No significant differences in device parameters were found at follow-up; and (6) answers to clinical questions were successfully determined in 27 of 29 (93%) thoracic MR scans, and in all 39 (100%) non-thoracic MR scans. The authors concluded that “…MRI can be performed safely in patients with certain permanent pacemaker or ICD systems. When proper precautions are taken, MRI of the region that contains the device is not associated with increased risk. This ability may significantly impact clinical decision making in appropriate patients...” The authors also commented that (1) transient reed switch activation, a part of normal device function, has minimal to no clinical consequences; and that (2) no cardiac devices had (as of 2006) achieved industry or FDA clearance for MR scanning compatibility, and catastrophic complications have been reported. Sommer T, Naehle CP, Yang A, et al. Strategy for Safe Performance of Extrathoracic MRI at 1.5 Tesla in the Presence of Cardiac PMs in Non–PM-Dependent Patients: A Prospective Study With 115 Examinations. Circulation. 2006 Sep 19; 114: 1285-92. The purpose of this prospective consecutive case series study is to evaluate a strategy for safe performance of extra-thoracic MRI in non-PM-dependent patients with cardiac PMs. After reviewing potential candidates, only 82 subjects met the inclusion/exclusion criteria. They underwent a total of 115 MR scans at 1.5 T. Patients’ mean age was 66.9 years (range 4 – 89 years); 53 males (65%) and 29 females (35%) participated. Inclusion criteria for the study included the presence of a cardiac PM and an urgent clinical need for MRI. Exclusion criteria were PM-dependent patients and those patients requiring examination of the thoracic region, as well as presence of MR scan-incompatible bioimplants or other materials. Various models of Medtronic PMs, and various models of atrial and ventricular leads from a variety of manufacturers (Medtronic, Guidant, Biotronik, St. Jude Medical, etc.) were implanted in participants. All PMs were reprogrammed before MR scanning based on pre-scan pulse: if heart rate was < 60 bpm, the asynchronous mode was programmed to avoid MR–induced inhibition; if heart rate was > 60 bpm, sense-only mode was used to avoid MR-induced competitive pacing and potential proarrhythmia. During the MR scan, audio contact was established via an intercom system, and patients were asked to inform the investigator immediately of any torque or heating sensation, palpitations, dizziness, pain, or other unusual symptoms during imaging. An electrophysiologist and full resuscitation equipment were present during all examinations. Patients were monitored with ECG and pulse oximetry. To minimize radiofrequency-related lead heating, the specific absorption rate was limited to 1.5 W/kg. PMs were interrogated immediately before and after the MR scan and after three months, including measurement of pacing capture threshold (PCT) and serum troponin I levels. Results of the study revealed: (1) all MR scans were completed safely; (2) inhibition of pacemaker output or induction of arrhythmias was not observed; (3) PCT increased significantly from pre- to post-MR scan (P = 0.017). In two of 195 leads, an increase in PCT was only detected at follow-up; (4) in four of 114 examinations, troponin increased from a normal baseline value to above normal after MR scan. In one case (troponin pre-MR scan 0.02 ng/mL, post-MR scan 0.16 ng/mL), this increase was associated with a ‘significant’ increase in PCT. The authors suggested that this increase in one patient might indicate myocardial injury; and (5) after MR scan, six patients died at a mean interval of 58 days (range 42 to 81 days) after MR scan. All deaths were related to the underlying disease (melanoma with cerebralmetastases, pancreatic carcinoma, and brain tumors (n=4). None of the six deaths were classified as pacemaker or MR scan related. The authors concluded that extrathoracic MR scan of non–PM-dependent patients can be performed with an acceptable risk-benefit ratio under controlled conditions and by taking both MR- and PM-related precautions. Case Series Gimbel JR, Bailey SM, Tchou PJ, et al. (Gimbel 2005) Strategies for the Safe MRI of PM-Dependent Patients. Pacing Clin Electrophysiol. 2005; 28:1041–6. In this case series, the authors’ objective was to determine if strategies used to safely scan non-PM-dependent patients could be applied to facilitate safe MRI of PM-dependent patients. The authors defined pacemaker-dependence as the absence of an underlying escape rate below the lowest programmed rate of the device. Ten PM-dependent patients underwent eleven MR scans. Age and gender information were not provided. The protocol stipulated that patients could not undergo MRI until six weeks after PM implantation. PMs implanted in these ten patients included: Pacesetter (n=5); Medtronic (n=5), with PM leads from various manufacturers. During MR scanning, the study’s protocol for safety included: (1) screening, reprogramming and monitoring strategies were used to facilitate MR scan; (2) continuous pulse oximetry as well as electrocardiogram (EKG) monitoring was used to monitor the patients during the MR scans; (3) an electro-physiologist was present throughout each study; and (4) the electro-physiologist and the MR technologist remained in voice contact with the patient during each procedure. All patients in this study had MR scans limited to the head and neck using a transmit receive head coil on a Siemens 1.5 Tesla Vision whole-body MR machine. This head coil limits “…direct RF exposure to the IPG and its leads in the chest.” Results of the study revealed: (1) all MR scans proceeded uneventfully. No difficulties in post-MR scan telemetry or interrogation were seen and no post-MR scan programming changes were noted; (2) no patient experienced arrhythmia or symptoms during or immediately after MR scan; (3) PM battery status remained unchanged; (4) no patient experienced post-MR scan change in sensing thresholds; and (5) three of ten patients showed no change in the atrial or ventricular pacing thresholds when the pre-MR scan values were compared to the immediate post-MR scan values and the three month follow-up values. The seven of the remaining ten patients showed a rise or fall of 0.5 V in their chamber pacing threshold values when the pre-MRI, post-MRI, and three month follow-up values were compared. In addition, all MR imaging studies produced diagnostic studies for the clinical question presented by the referring physicians. The authors stated that “… [n]o clinically significant artifacts attributable to the pacemaker were identified within the field-of-view of the MR study.” The authors concluded that “… (L)ike non-PM-dependent patients, MR scanning might be performed in PM-dependent patients if appropriate PM reprogramming, patient monitoring and MR scanning techniques are implemented.” Gimbel JR, Kanal E, Schwartz KM, et al.. Outcome of MRI in Selected Patients with Implantable Cardioverter Defibrillators (ICDs). Pacing Clin Electrophysiol. 2005; 28: 270–3. In this case series, the authors studied seven patients with implanted ICDs and with medical reasons for MR scans, to determine if simple strategies used to safely scan PM patients could also be applied to ICD patients. Gender and age information about participants was not provided. Manufacturers of the seven implanted ICDs included Medtronic (n = 6) and Cardiac PaceMakers, Inc. (n = 1). Clinical indications for MR scans included suspected posterior fossa or pituitary tumor (n = 2); suspected brain metastases (n = 2); or other brain lesion or symptom (n =3 ). Reprogramming and monitoring strategies were used to facilitate MRI. Results of the study indicated that the seven patients underwent eight MR scans (one patient underwent pre- and post-op scan for a pituitary tumor). In six of seven patients, during cranial MRI under continuous monitoring, no arrhythmias were noted, and no symptoms such as palpitations, tugging, or warmth were reported during the scan itself. In one of the patients one potentially serious adverse event occurred during a lumbar spine MR scan. The subject reported “painless involuntary muscle reaction like twitching several times” of his left upper pectoral region and upper extremity during the MR scan. This sensation stopped as the MR scan ended, and did not recur. This patient’s device underwent a “Power On Reset” (POR) during MR scan. Post-MR scan communication with the device was unimpaired and all pacing, sensing, impedances, battery voltages, and charge times remained identical to the values obtained pre-MR scan. The manufacturer concluded that “the cause of the POR was due to a microprocessor instruction error and/or memory error,” based on a personal communication with a reliability engineer employed by the manufacturer. Follow-up interrogation data at one month post-MR scan was available on six of seven patients. One patient expired ten days post-MR scanning from complications of metastatic lung cancer—metastatic brain lesions were seen only on MRI. No ICD dysfunction was noted prior to the patient’s demise. At one month, the six ICDs available for analysis showed no change in pacing, sensing, impedance, battery voltage, or charge time parameters. The authors concluded that “Scanning of ICD patients might be performed if appropriate re-programming and monitoring is implemented.” Martin ET, Coman JA, Shellock FG, et al. MRI and Cardiac PM Safety at 1.5-Tesla. J Am Coll Cardiol 2004; 43: 1315–24. In this mixed prospective-retrospective consecutive case series, the authors studied 54 patients with previously implanted PMs to determine if patients with PMs could safely undergo MRI at 1.5-Tesla. Each patient had a clinical indication for MR scan. PM-dependent patients were excluded from study participation. Excluding a scan for one patient in whom the PM was implanted at ‘end-of-life,’ performance of MR for the 61 other scans was evaluated. Gender and age information on participants was not provided. Seven of the 54 patients were included in the study prior to IRB approval of the study protocol and are included in the study analysis. Implanted PMs were the products of four different manufacturers, and each PM was interrogated immediately prior to MR scanning. MR scans (including MR angiography (MRA)) were performed at 1.5 Tesla. The types of MR scans included cardiac, vascular, and general MRI. No limitations were placed on the type or duration of the MRI procedure, PM, or lead models, nor proximity of the imaged anatomy relative to the PM. During MR scans, patients were continuously monitored, and afterwards, PMs were interrogated. ‘Any change’ and ‘any significant change’ in pacing thresholds after MR were the outcomes of interest, and were reported as dichotomous variables as ‘yes/no.’ (‘Any change’ was determined in patients with any measurable difference in either an atrial or ventricular lead; ‘any significant change’ was determined with measurable differences exceeding 1 voltage or pulse width increment or decrement.) Also, changes in other electrical characteristics of PMs, including initial programming and lead impedances, as well as artifacts on MR images, were studied. Results of the study revealed: (1) no episodes of loss of capture or changes in lead impedances or battery voltages were noted after MR scans; (2) no damage to pacemaker circuits or movement of the pulse generator was observed; (3) no serious adverse events occurred. However, two patients reported ‘mild and transient’ symptoms; vibration (n = 1) and palpitations (n=1) coinciding “with inhibition of the pacing lead.” Termination of MR procedure was not required in either case; (4) forty (37%) of 107 (48 atrial and 59 ventricular) leads underwent changes, whereas ten (9.4%) leads underwent a significant change; (5) two of 107 (1.9%) leads required a change in programmed output; and (6) threshold changes were unrelated to cardiac chamber, anatomical location, peak SAR, and time from lead implant to the MRI examination. The authors concluded that safety was demonstrated in this series of patients with pacemakers at 1.5 T. They also discussed the clinical significance of the PM threshold changes observed. “Significant changes were infrequent … The energy increases that were needed to accommodate the rise in thresholds were minor and did not impair the safe performance of the pulse generators. Despite the labeling of these changes as significant, they were of no clinical consequence.” The authors also noted that electro-magnetically induced noise, noted on telemetry, was monitored closely because it resembled serious cardiac arrhythmias. Naehle CP, Volkert Z, Daniel T, et al. (Naehle et al., 2009B) Evaluation of Cumulative Effects of MR Imaging on Pacemaker Systems at 1.5 Tesla. Pacing Clin Electro-physiol. 2009; 32:1526–35. In this retrospective case series, the authors evaluated possible cumulative effects of repeated MRI examinations on pacemaker systems in patients with cardiac pacemakers. The study population included 47 patients with PMs who underwent two or more MR examinations at 1.5 T in any anatomical region. These patients underwent a total of 171 MR scans, a median of two MR scans per patient; three patients underwent 12, 13, and 18 MR scans. Ages and gender information were not provided. Inclusion criteria included: (1) an urgent need for MRI; (2) stable physical PM parameters (estimated remaining battery lifetime > six months, LIs 200 to 2,000 ohms); (3) stable pacing parameters (PCT < .5 V at pulse duration of 0.4 ms, sensing > mV); and (4) three or more months since PM and lead implantation. Exclusion criteria included: (1) absolute PM dependence (intrinsic heart rate less than 40 bpm); (2) presence of MRI-incompatible bioimplants or other MRI incompatible materials; and (3) history of ventricular tachycardia or VF. PMs from eight manufacturers had been implanted in the 47 study participants. Patients underwent different types of MR scans, including brain (n = 108); lumbar spine (n = 27); and other anatomical regions (n=38). To minimize the risk for RF related heating, the specific absorption rate was limited to 1.5 W/kg, and the scanning sequences were modified as necessary. Pacemakers were interrogated before and after MR scanning, and after 3 months; pacing captured threshold, lead impedance, while battery voltage were measured. PM electrical characteristics (e.g., pacing capture threshold) were compared using linear regression analysis for changes with the number of MR scans, and with time. Results of the study revealed: (1) atrial pacing capture thresholds (PCT), both pre- and post-MR PCTs and PCT on three-month follow-up decreased by less than .01 volt (V) (C.I. -0.0193 to -0.0001) with increasing number of MR scans. None of the 37 patients with an atrial pacing lead had a change in PCT of 1.0 V or more; (2) based on data from 43 patients with ventricular pacing leads, both pre- and post-MRI and three-month follow-up, there was a small (-0.01 to -0.02 V) decrease in ventricular PCT with increasing MR scans. None of these 43 patients had a change in ventricular PCT of 1.0 V or more; (3) lead impedance (LI) was not changed significantly based on number of MR scans. None of the patients’ atrial or ventricular LI exceeded expected limits (200 – 2000 ohms); and (4) battery voltages (BV) showed a small but significant decrease as a function of number of MR scans received. In pre-MR, post-MR and follow-up the changes in BV were about 0.001 V/MR scan. However, these changes were less than the accuracy of the measurement. Also, mean BV decreased by 0.01V/year. The authors concluded that no clinically relevant, cumulative changes in PCT, LI, or BV could be detected in PM patients who underwent two or more MRI examinations. The authors suggested that further clinical studies of cumulative effects would be valuable. Single Case Report Naehle CP, Sommer T, Meyer C, et al. (Naehle 2006) “Strategy for Safe Performance of Magnetic Resonance Imaging on a Patient with ICD.” Pacing Clin Electrophysiol 2006; 29: 113–6. In this case report, the authors reported that an MR scan was performed on a 33 year old male patient with an ICD due to suspected recurrence of astrocytoma. The authors intended to demonstrate that full function of the ICD system was verified after imaging. Prior to MR scan, the ICD was interrogated for electrical characteristics, and a serum troponin level was drawn from the patient. An MR scan was performed at 1.5 T, with imaging and hardware protocols modified to minimize radiofrequency power deposition to the ICD device, a Biotronik Lexos VR ICD. During the MR scan, the patient was asked to report any sensations or symptoms. A complete ICD evaluation, to include electrical characteristics of ICD, measurement of sensing pacing capture thresholds (PCT), lead impedance, and battery voltage, would be performed immediately before and after the procedure, three days after and six weeks after the procedure. Also, post-scan serum troponin levels, and impact of MR results on patient’s therapy were assessed. The study results revealed the following: (1) the patient underwent the MR scan safely and without any discomfort, such as heating sensation or movement of the device.