Journal of the Practice of Cardiovascular Sciences

CURRICULUM IN CARDIOLOGY - JOURNAL CLUB
Year
: 2018  |  Volume : 4  |  Issue : 1  |  Page : 37--40

Safety of magnetic resonance imaging in patients with cardiac devices


Nitin Kumar Parashar1, Mumun Sinha2, Neeraj Parakh3,  
1 Department of Cardiology, All India Institute of Medical Sciences, New Delhi, India
2 Department of Cardiac Radiology, All India Institute of Medical Sciences, New Delhi, India
3 Department of Cardiology, Cardiothoracic Sciences Centre, All India Institute of Medical Sciences, New Delhi, India

Correspondence Address:
Dr. Neeraj Parakh
Department of Cardiology, Cardiothoracic Sciences Centre, All India Institute of Medical Sciences, New Delhi - 110 029
India




How to cite this article:
Parashar NK, Sinha M, Parakh N. Safety of magnetic resonance imaging in patients with cardiac devices.J Pract Cardiovasc Sci 2018;4:37-40


How to cite this URL:
Parashar NK, Sinha M, Parakh N. Safety of magnetic resonance imaging in patients with cardiac devices. J Pract Cardiovasc Sci [serial online] 2018 [cited 2021 May 17 ];4:37-40
Available from: https://www.j-pcs.org/text.asp?2018/4/1/37/231924


Full Text

Article: Russo RJ, Costa HS, Silva PD, et al. Assessing the risks associated with MRI in patients with a pacemaker or defibrillator. N Engl J Med. 2017;376(8):755.764.

 Introduction



Many patients with cardiac pacemakers or implantable cardioverter-defibrillator (ICD) subsequently have an indication of magnetic resonance imaging (MRI)[1]MRI in these patients is generally denied due to potentially dangerous interactions between these intracardiac devices and magnetic fields and radiofrequency energy used in MRI studiesThe interaction between the intracardiac device and MRI occurs due to three essential components of an MRI which are a static magnetic field, gradient magnetic field, and radiofrequency energy [Table 1][2]Due to these potential hazards, some modifications were done in cardiac devices so that MRI can be performed safely on these devices.[3],[4] These devices were called MRI conditional devices, and others were termed legacy or conventional or nonMRI conditional devicesThe main modifications in MRI conditional devices include a reduction in ferromagnetic components, replacement of reed switch by hall sensor, change in lead coil design and insulation, and change in filter circuitry to prevent damage to the internal power supply and dedicated pacemaker programming to prevent inappropriate pacemaker inhibition. These MRI conditional devices were introduced in 2008 for the first timeHowever, the vast majority of pacemaker and ICD systems in current use are not MRI conditional devices. Presence of the conventional intracardiac device is a standard contraindication for against the use of MRISmaller studies have reported safety of MRI in patients with a legacy pacemaker or ICD. A recent larger study evaluated only nonthoracic examinations and revealed the safety of MRI in these patients.[5]{Table 1}

 Methods



This was large, prospective study to evaluate the safety of MRI protocol in patients with a legacy pacemaker or ICD systemsThe study was funded by Johns Hopkins University and the National Institutes of HealthPatient selection: Candidates who had an ICD or a pacemaker and a clinical indication for MRIEnrolled during the period from February 2003 to January 2015.

Exclusion criteria

Patients who had undergone lead implantation within the previous 4 weeksIf the patient had permanent surgical epicardial leads or permanent nonfunctional leadsIf they were pacing-dependent and had an ICD without asynchronous pacing capability.

 Device Interrogation and Programming



An asynchronous pacing mode was programmed for pacing-dependent patients to avoid inappropriate inhibition of pacing resulting from the detection of electromagnetic interferenceIn contrast, an inhibited pacing mode was used for patients without pacing dependence to avoid inappropriate pacing resulting from the tracking of electromagnetic interferenceTachyarrhythmia monitoring and therapies were deactivated in ICD devices to avoid the delivery of unwarranted therapiesAfter completion of the MRI, the devices were reprogrammed to the original settings. Long-term follow-up interrogation at 6 months was recommendedImaging was performed with the use of MRI scanners with the commonly used magnetic field strength of 1.5 tesla (Magnetom Avanto and Magnetom Aera, Siemens)Symptoms, such as pain, warmth, and palpitations, were monitored with the use of an in-room speaker systemBlood pressure (BP), measured noninvasively, was assessed every 3 minContinuous electrocardiographic monitoring was performed.

 Outcome Assessment



Study outcome assessments included adverse events and changes in device parameters.

Anticipated adverse events in the device

Generator failurePower-on reset (PoR) – In which device settings are reset automatically to a backup mode as if the power to the device had been shutoff and then turned-on againChanges in pacing threshold or sensing that require system revision or programming changesBattery depletionCardiac arrhythmiaInhibition of pacingInappropriate delivery of antitachycardia pacing or shockPatient-reported events such as discomfort, pain, a warm sensation in the location of the device, and palpitations.

Device parameters

P-wave amplitudeRight ventricular and left ventricular R-wave amplitudeAtrial, left ventricular, and right ventricular lead impedanceAtrial, right ventricular, and left ventricular capture thresholdBattery voltage.

Change in device parameters

Given the expected variation in lead parameters on repeat measurement, percentage changes from baseline were categorized as follows:No change (≤20% change)Expected change (>20%–50% change)Notable change (>50% change).

Statistical analysis

Continuous variables are summarized as medians and interquartile ranges, and discrete variables as absolute numbers and percentagesThe associations between changes in device parameters that occurred either immediately after the MRI or at long-term follow-up were assessed with the use of the nonparametric k-sample test on the median (unordered groups) or a nonparametric test for trend (ordered groups).

 Results



A total of 2103 MRI examinations was performed in 1509 patients, 880 (58%) of whom had a pacemaker, and 629 (42%) of whom had an ICDOf the 1509 patients, 137 (9%) were pacing dependent (22 of whom had an ICD with asynchronous programming mode capability)This study included patients underwent thoracic MRI examination also (n = 257, 12%)A total of 1189 of the 1509 patients (79%) underwent a single MRI examinationThe repeat MRI examination was performed in 320 patients (21%); about 18 patients underwent six or more examinationsPoR occurred during a total of nine MRI examinations (0.4% of the examinations) in eight patients (0.5% of patients). Six out of these eight patients completed MRI study successfully, and MRI examination in two patients was terminated prematurelyNone of the patients who had a transient event of PoR had device dysfunction at long-term follow-upThe most common notable change in device parameters (>50% change from baseline) immediately after MRI was a decrease in P-wave amplitude, which occurred in 1% of the patientsAt long-term follow-up (results of which were available for 63% of the patients), the most common notable changes from baseline were decreases in P-wave amplitude (in 4% of the patients), increases in atrial capture threshold (4%), increases in the right ventricular capture threshold (4%), and increases in the left ventricular capture threshold (3%)Premature atrial and ventricular beats and occasional nonsustained episodes of ventricular tachycardia, as well as an episode of paroxysmal atrial fibrillation, were observed. However, no arrhythmias were temporally associated with MRI sequence initiation, rhythmicity, or termination.

 Discussion



As the study protocol, asynchronous pacing mode was used for pacing-dependent patients and inhibited pacing mode was used for pacing independent patients and tachyarrhythmia monitoring and shock therapy were terminated in ICD patientsThe most important event that was found to be attributable to MRI was the occurrence of PoR in approximately 1 in 200 examinations [Table 2]During the events of PoR, the device is susceptible to inhibition of pacing output and activation of antitachycardia therapies [6]Of the nine MRI examinations in which events of PoR occurred, one examination was associated with mild physical symptoms, one (which occurred near the end of the battery life of the device) resulted in an inability to reprogram the device and in the consequent replacement of the device, and one was associated with transient inhibition of pacingThe observed changes in device parameters (lead sensing, impedances, and capture thresholds) were not clinically significant and did not require device revision or reprogrammingPrevious reports had suggested that MRI of the thorax may present a greater risk of safety issues than MRI of nonthoracic regions owing to the greater power deposition over the region containing the deviceHowever, the current larger study, in which the follow-up period was longer, does not suggest any association between the region of imaging and detrimental changes in device parametersA recently published study by Padmanabhan et al. showed that brain MRI in patients with pacemaker or ICD does not carry increased mortality risk as compared with brain computed tomography.[7]{Table 2}

Positive points of the study

This study showed that MRI studies are safe in cardiac devices patientsLegacy intracardiac devices are generally considered unsafe for the MRI studies. However, no definite evidence has been provided for the same. The present study refuted this hypothesis by revealing safety of MRI in legacy intracardiac devicesThis study included the patients having both pacemakers and ICDsA significant number of patients underwent thoracic MRI studies also. These patients were excluded in the previous studiesPacing-dependent patients require extra care and monitoring during MRI studies; however, MRI can be done in these patients also.

Limitations of this study

This study is a single-center studyThe authors were unable to obtain long-term follow-up of a large number of patients (n = 302, 20%)Device technology is constantly in evolution. Hence, results should not be generalized to older or newer generation devicesAll the MRIs were performed at 1.5 tesla strength in this study. Further studies will be required to reveal safety of MRI at three-tesla strength in the patients having intracardiac devices.

 Conclusion



Both thoracic and extrathoracic 1.5 T MRI studies can be carried out safely in patients with legacy pacemakers/ICD (non-MRI conditional devices) with the following conditions:The presence of trained nurse/doctorImmediate availability of an electrophysiologistUnder the proper supervision and monitoring (Electrocardiogram, BP, Pulse rate, and O2 saturation) with the availability of external pacing backup.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.

References

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