Long awaited results of the MagnaSafe study regarding the safety of MRIs in patients with implantable devices were published in February. The MagnaSafe study established a multi-center prospective registry for patients undergoing MRI scans despite their having an implanted device not deemed safe for MRI scanning by the FDA.
The HCM Risk–SCD Score
In 2014, the European Society of Cardiology (ESC) introduced a numerical predictor (the “HCM Risk–SCD score”) to assist physicians in identifying those patients at highest risk for sudden cardiac death who would benefit from the implantation of a prophylactic implantable cardioverter-defibrillator.
Using an algorithm generated by the answers to a series of questions, the tool estimates the 5-year risk of sudden cardiac arrest for any particular patient. You can find the tool online here.
Two posters presented at this weekend’s Heart Rhythm Society meeting in Chicago show that patients who have abandoned pacemaker or ICD leads may safely undergo MRI exams.
These posters follow the earlier MagnaSafe study which demonstrated the safety of MRI for patients with pacemakers and ICDs, but which excluded patients with abandoned leads from the findings.
The first, by researchers at Mayo Clinic, included 57 patients with 63 abandoned leads who underwent 70 MRI exams in a 1.5 Tesla machine. The authors saw no clinical problems and no device malfunction following the scans.
The researchers also monitored blood troponin levels in 35 of the patients following the scans and did not see any elevation which could indicate distress to the heart from the scan.
The second poster, from the University of Pennsylvania, involved 24 patients with abandoned leads who underwent 34 MRI exams. The results of this study also failed to demonstrate any clinical problems or patient discomfort resulting from the MRI scans.
With any luck, everyone will soon be able to obtain an MRI and will not be denied due to any kind of implantable cardiac device.
For an account of my personal experiences seeking MRI with an ICD, read this.
A study published this week by HCM researchers in Canada found that double mutations in patients with hypertrophic cardiomyopathy are much less common than previously thought. In particular, researchers found that except for those with double mutations in the gene MYBPC3, there is not much data to support the finding that there is a worse clinical course for those patients who have double HCM mutations.
Hence, in the absence of extraordinary circumstances, such as two MYBPC3 mutations, the researchers caution that double mutations should not be the sole justification for the insertion of an implantable defibrillator.
The study looked at patients >18 years of age who underwent genetic testing at the Toronto General Hospital between January 2005 and June 2016. Out of a sample of 1411 patients, 9% of those who were gene-positive patients had 2 genes, but only in 1 case (0.4%) were both genes classified as those known to cause HCM.
In addition to looking at their own patients, the researchers also re-examined data from previously published studies. Similarly, they found when they re-analyzed the data that only 0.4% of the 8% of patients previously found to have double mutations in fact carried multiple pathogenic mutations.
The long awaited results from the Magna-Safe study were published today in the New England Journal of Medicine, and it was good news for pacer and implantable cardioverter–defibrillator (ICD) patients! When proper precautions have been taken, MRIs were found to be safe in patients implanted with certain older pacemakers or ICDs.
In order to study the safety of scanning these patients, doctors set up a prospective registry for patients undergoing MRI in scanners with a magnetic field strength of 1.5 tesla who were scanned despite having a non-MR conditional device (i.e. a device which had not been deemed safe for MRI scanning by the FDA).
MRIs were performed on 1000 patients with pacemakers and 500 patients with ICDs and the results of the study showed that as long as appropriate patient selection and safety protocols were followed, patients had no problems with the MRI scans.
This is indeed good news for those of us with older devices who may be in need of MRI scans. To read about my own experiences and investigation of this issue, read my previous blog entry YES WE SCAN! ICDs and MRIs.
A recent retrospective study of patients at Minneapolis Heart Institute and Tufts Medical Center published in the Journal of the American College of Cardiology found that HCM patients who also had left ventricular apical aneurysms were at increased risk of sudden cardiac death and stroke. However, with increased surveillance and appropriate treatment, including the implantation of a implantable defibrillator, radiofrequency ablation and/or anti-coagulation, as appropriate, the authors suggest that the increased risk can be neutralized.
A summary of this article can be found here.
The U.S. Food and Drug Administration today issued a safety advisory regarding St. Jude Medical implantable cardiac devices used in conjunction with St. Jude’s proprietary Merlin @home Transmitter.
According to the advisory, these devices could potentially be vulnerable to hacking. However, only a highly skilled hacker would be sophisticated enough to exploit the vulnerability. Such unwarranted interference could conceivably cause premature battery depletion or unnecessary shocks.
A software patch has been developed for the Merlin @home monitor designed to address the issue and to reduce the risk of hacking. The update is now available and will be applied automatically to the Merlin monitor.
***Patients only need to make sure their Merlin@home Transmitter remains plugged in and connected in order to receive the software patch.***
Short-selling firm Muddy Waters first went public with this information in August, believing that it might cause a pending $25 billion acquisition of St. Jude Medical by Abbott Laboratories to fall apart. However, the deal closed last week despite the issue.
Why MRI is Important:
Magnetic Resonance Imaging, or MRI, is one of the most important tools of modern medicine. MRIs can be used to evaluate almost every kind of medical issue, from brain tumors to twisted ankles. They provide clear images, and in some instances, also provide superior visualization. Because they do not expose the imaging subject to radiation, they are generally preferred over CT scans, even when the two scans would reveal the same information.
MRI in HCM:
In the last several years, MRI has also become an important tool in the evaluation of hypertrophic cardiomyopathy (HCM). The images resulting from MRI have proven superior in visualizing the size and structure of the heart and, when used with a contrast agent, MRIs are able to show the extent of scarring in the HCM heart.
MRI Hasn’t Been an Option for Many of Us:
MRI has been unavailable to those of us who have an implantable defibrillator or ICD to in order to protect us from sudden cardiac arrest. Until recently, having an ICD was an absolute contraindication to MRI. Newer MRI-safe ICD systems have been in use for the last few years, but that still leaves in place the contraindication for those of us who have older ICD units in place. That problem is that older lead systems that were implanted along with old, non-MR compatible generators may be incompatible with the newer MR compatible technology, and it may not be possible to simply hook up these old leads to a new MRI compatible generator. And, it is not as easy as you might think to extract old leads. Scar tissue grows around these leads, making their removal an intricate and dangerous procedure that is best done only in carefully controlled circumstances by highly specialized physicians. Continue reading “Yes We Scan! ICDs and MRIs”
St. Jude Medical announced today that as many as 400,000 of its Fortify, Fortify Assura, Quadra Assura, Unify, Unify Assura and Unify Quadra implantable cardiac defibrillator (ICD) and cardiac resynchronization therapy defibrillator (CRT-D) devices manufactured prior to May 23, 2015 are subject to a recall notice due to a risk of premature battery depletion which may render the device unable to deliver a life saving shock.
According to the FDA, the patients most at risk are those who require lifesaving shocks and those who are pacemaker dependent.
The problem has so far resulted in two deaths.
Patients with these devices should contact their physicians for advice about how to proceed, and should seek immediate medical attention if they hear a low-battery alert from their Merlin monitoring device. Continue reading “St. Jude Medical ICD Recall”
According to a recent study published in JACC: Clinical Electrophysiology, previously abandoned pacemaker and implantable defibrillator leads which have been capped off and left behind following replacement were harder to extract later. These abandoned leads also made it more difficult to treat device infections.
When interviewed about the significance of these study results, several physicians knowledgeable in the field further emphasized that lead removal requires special skill and equipment not typical for the average physician who implants cardiac devices. Hence, patients facing a potential lead extraction should consider their options carefully and seek care from a specialist in lead extraction.