How To Handle ICD If Patient’s Heart Function Improves?

Alan Cheng, MD, FACC, FAHA, FHRS Associate Professor of Medicine Associate Professor of Pediatrics Director, Arrhythmia Device Service Johns Hopkins University School of Medicine Baltimore, MD 21287MedicalResearch.com Interview with:
Alan Cheng, MD, FACC, FAHA, FHRS
Associate Professor of Medicine and Pediatrics
Director, Arrhythmia Device Service
Johns Hopkins University School of Medicine
Baltimore, MD

Medical Research: What is the background for this study? What are the main findings?

Dr. Cheng: Sudden cardiac death (SCD) has been the most common way in which people in the United States die. While it’s hard to accurately identify who is a higher risk for SCD, we have learned from a number of studies over the past 30-40 years that people with significant reductions in their heart function (measured as the ejection fraction (EF)) is one group of individuals at high risk for Sudden cardiac death. In fact, the current American College of Cardiology and American Heart Association guidelines state that people with an EF below 35% are at high enough risk for Sudden cardiac death that these patients should undergo implantation of an implantable cardioverter defibrillator (or ICD for short), a device capable of monitoring the heart 24/7 and shocking the heart out of any arrhythmias that could lead to Sudden cardiac death. The data they cite for this recommendation are so compelling that they currently recommend implanting ICDs in patients not only among those who already experienced an Sudden cardiac death event, but also those who have not. Implanting an ICD to prevent Sudden cardiac death before they have had Sudden cardiac death is known as primary prevention and this accounts for about 70-80% of all ICD implants in the United States.

While the EF is the best metric out there to determine if a patient should get an ICD, it has its limitations. Because of these limitations, we have been interested for a long time in better understanding how the EF and other metrics affect a patient’s risk for Sudden cardiac death.

In this study, we followed 538 patients who were recipients of a primary prevention ICD who underwent repeat assessment of their EF during followup in order to determine if changes in their EF over time altered their risk for ICD shocks for ventricular arrhythmias or death. Over a median of almost 5 years of followup, we found that 40% of the cohort had improvements in their EF. And when the EF does improve, the risk goes down for ICD shocks for ventricular arrhythmias as well as for death.

Medical Research: What should clinicians and patients take away from your report?

Dr. Cheng: Since changes in Ejection Fraction can affect a patient’s risk for ICD shocks and death, it is important that patients and their doctors are doing everything possible to maximize the chances of EF improvement or at the very least avoid a worsening of the EF. Heart failure medications are the most important interventions in trying to accomplish this and therefore, it is important that patients and their doctors are constantly looking at ways to maximize and optimize their heart failure medication regimen.

Medical Research: What recommendations do you have for future research as a result of this study?

Dr. Cheng: In most patients, getting an ICD was based on the fact that the EF was <35%. One natural question from this study is whether patients with ICDs who later show improvement in their heart function to >35% and whose ICDs are due for a generator exchange (because the battery is expiring) benefit from having their generators replaced. This is a very important question that many patients and their doctors are facing. Our study may seem to suggest that a generator exchange is not necessary, but it’s important to point out that while we found that the risk of ICD shocks goes down when the EF improves, the risk was not zero. I think it’s premature to say that patients with improvements in their EF >35% no longer need a generator exchange. Our data doesn’t support this assertion and larger studies will be needed to confirm our findings and further tease out who can and cannot avoid a generator exchange.

Citation:

Zhang Y, Guallar E, Blasco-Colmenares E, et al. Changes in Follow-Up Left Ventricular Ejection Fraction Associated With Outcomes in Primary Prevention Implantable Cardioverter-Defibrillator and Cardiac Resynchronization Therapy Device Recipients. J Am Coll Cardiol. 2015;66(5):524-531. doi:10.1016/j.jacc.2015.05.057.

 

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Alan Cheng, MD, FACC, FAHA, FHRS (2015). How To Handle ICD If Patient’s Heart Function Improves? MedicalResearch.com

Last Updated on July 31, 2015 by Marie Benz MD FAAD