LAUSR

In their article ‘‘2020 MR Safety for Cardiac Devices: An Update for Radiologists,’’ Lebel et al. review the current literature on cardiac magnetic resonance (CMR) in patients with cardiovascular implantable electronic devices (CIEDs) while providing a framework on how to safely image these patients. They share their experience with performing CMR on CIED patients with specific emphasis on safety and work-flow. With the growing number of patients with CIEDs and the increasing utility of CMR, we have also experienced an increased demand for CMR in patients with CIEDs. We started clinically scanning patients with CIEDs in 2016 and have scanned approximately 800 patients with both conditional and nonconditional CIEDs. Approximately 20% of these were CMRs. Similar to Lebel et al., we have found that CMR can be safely performed in patients with CIEDs if there is an established imaging program and standardized workflow. Our work flow leading up to the day of the examination is similar with a complete pre-MRI assessment which includes gathering the appropriate information for the specific CIED, performing additional risk assessment, and ensuring that the indication is appropriate. Expanding on the workflow described by Lebel et al., on the day of the exam we adhere to a well-coordinated multidisciplinary standardized workflow. For conditional devices, a timeout is performed by our ACLS nurse in MRI Zone II with the patient, MRI technologist, EP nurse/ACLS Nurse, physicist, and devices specialist. Our physicist states the scanning parameters (SAR limits) and the protocol is reviewed with the MR technologist. In Zone II, the MRI compatible monitoring system is connected and vital signs are recorded. The device specialist interrogates the device and sets it into scan mode. An ACLS-trained nurse is present to monitor the patient throughout the exam and the device specialist returns at the end to reset the CIED. Our protocol on the day of the exam for nonconditional devices differs as a radiologist is present to consent the patient acknowledging that the device is not FDA approved for use in an MRI environment. Furthermore, for nonconditional devices the entire exam is not only monitored by the ACLS nurse, but also the EP nurse, device specialist, and radiologist. An EP cardiologist is available on site if needed. With this workflow we have been able to safely perform CMRs on patients with CIEDs and have had no adverse events. Where our experience differs from Lebel et al. is with the success rate of performing diagnostic quality CMRs. We define success as the ability to answer the clinical question without significant limitations. The authors reported that only 1% of their studies were nondiagnostic. Others have reported a 90% diagnostic rate for thoracic and cardiac MRIs in patients with CIEDs. We have found that our success rate is closer to 8590%. Our success rate varies by indication and location of the device. Similar to Lebel et al., we have found that thinner patients and those with left-sided devices have a higher likelihood of having substantial artifact on their study. The anterior septal myocardium can be particularly difficult to evaluate due to image artifact from the device and leads. Depending on the indication of the study, there are several techniques that we can employ to help improve image quality. Our most common request for CMR is for evaluation of infiltrative cardiomyopathy. In this case CMR is the reference standard and we make every attempt possible to perform such examinations. It is essential to visualize the entirety of the left ventricular myocardium without artifact from the CIED. We share similar techniques to Lebel et al, when dealing with device artifact. If artifact is encountered, the patient’s left arm is positioned above the ahead which helps move the device and metallic artifact to a location superior to that of the heart. We also recommend using gradient echo cine images as they reduce metallic artifact relative to steady-state free precession. In order to improve our post contrast images, we anticipate the use of a wideband late gadolinium enhance sequence. This will be particularly helpful in our practice not only for infiltrative cardiomyopathy, but also for patients with ventricular tachycardia presenting for evaluation of myocardial scarring prior to an ablation procedure who often have implantable cardioverter-defibrillators in place. Evaluating congenital heart disease (CHD) is the second most common indication in our practice for CMR. These