One in 4 patients with defibrillators experiences boost in heart function over time

July 27, 2015

A Johns Hopkins-led study of outcomes among 1,200 people with implanted defibrillators -- devices intended to prevent sudden cardiac death from abnormal heart rhythms -- shows that within a few years of implantation, one in four experienced improvements in heart function substantial enough to put them over the clinical threshold that qualified them to get a defibrillator in the first place.

A report on the study, published in the Aug. 4 issue of the Journal of the American College of Cardiology, reveals these patients had markedly lower risk of dying and were far less likely to suffer arrhythmia-terminating device shocks, suggesting their hearts had grown less prone to developing lethal rhythms.

All of the patients in the study had received defibrillators because of declining heart function -- a condition that puts them at high risk for lethal rhythm disturbances -- but none of them had experienced an actual cardiac arrest. Such pre-emptive defibrillator placement is known as primary prevention and is distinct from implantation of devices in cardiac arrest survivors with a history of dangerous rhythm anomalies, an approach known as secondary prevention.

The investigators attribute the improvement in heart function primarily to the concurrent use of heart failure medications that enhance the heart's ability to pump and, in a small portion of patients, to the concurrent use of a special pacemaker that synchronizes the contraction of the heart's chambers. The team says the real surprise was not the fact that patients got better, but rather how many did.

Because the number of rhythm-restoring device shocks never reached zero among those with improved heart function, researchers say arrhythmia risk was not completely eliminated and patients may continue to derive at least some protection from defibrillators even as their hearts become less susceptible to fatal rhythms. But because defibrillators can also cause serious complications, the risk-benefit ratio does shift substantially in people whose heart function improves dramatically, the researchers say.

"Our results highlight an urgent need to refine the risk-benefit assessment in people repeatedly, over the course of their treatment, and not just at the time of device implantation," says senior investigator Alan Cheng, M.D., a cardiac electrophysiologist and an associate professor of medicine at the Johns Hopkins University School of Medicine.

"Determining if patients with defibrillators whose hearts get better over time may be better off without the device is just as important as determining who needs a defibrillator in the first place," he says.

Implanted defibrillators detect and correct arrhythmias that cause cardiac arrest, but they can also misfire, delivering startling, painful, unnecessary and, at times, dangerous shocks. And because placing the device inside the chest is an invasive and complex procedure, the investigators say, there is risk of blood vessel damage and dangerous heart valve infections.

Predicting which patients are most at risk for a cardiac arrest and stand to benefit most from a defibrillator is often tricky and invariably involves some guesswork, researchers add.

Long-standing clinical guidelines from the American College of Cardiology and the American Heart Association call for all people with heart failure whose hearts' ejection fraction is below 35 percent to receive a device if they are able to undergo the implantation.

"Heart function below 35 percent is the current standard guiding device placement. But our study shows in one-quarter of people with defibrillators, heart function, over time, goes above that threshold, suggesting that a person's risk for arrhythmia is not static. Monitoring such fluctuations is essential to optimize the clinical management of these patients," Cheng says.

For the study, researchers enrolled and followed nearly 1,200 people, ages 18 to 80, who received defibrillators at four heart centers in the United States between 2003 and 2013 and who were followed for an average of five years. A portion of the group, 538 (45 percent), underwent at least one heart function re-assessment after initial device placement.

The patients' heart function was evaluated by measuring how well their left ventricles -- the heart's main pumping chamber -- propelled blood to the rest of the body. Of the 538 patients, 40 percent experienced improved heart function defined as increased left ventricular ejection fraction. In one-quarter of patients, left ventricular performance increased above 35 percent, the threshold that defines severely compromised heart function and calls for defibrillator placement. These patients had a 33 percent lower risk of dying and a 30 percent lower risk of appropriate device shocks, compared with patients whose heart function remained unchanged.

The investigators say the fact that fewer than half of all patients in the study had their heart function re-assessed prior to their regularly scheduled device replacement points to the need for better ongoing monitoring.

"Heart failure patients need regular follow-up with a general cardiologist or a heart failure specialist because clearly heart function can change over time, and because new therapies are being developed that may change their prognosis and treatment," Cheng says.

More than half a million cardiac arrests occur each year in the United States, according to the American Heart Association. The odds for those who suffer cardiac arrest outside the hospital are bleak -- less than 10 percent survive -- and those who do often come out of it with serious neurologic damage.

Researchers estimate that between 8,000 and 10,000 defibrillators are implanted in the United States every month, and the cost of the procedure and device can range between $15,000 and $25,000.
-end-
Other investigators involved in the study included Yiyi Zhang, Eliseo Guallar, Elena Blasco-Colmenares, Barbara Butcher, Sanaz Norgard, Victor Nauffal, Joseph Marine and Gordon Tomaselli of Johns Hopkins.

Investigators from other institutions included Zayd Eldadah of Washington Hospital Center, Timm Dickfeld of the University of Maryland and Kenneth Ellenbogen of the Virginia Commonwealth University School of Medicine.

The work was by funded by the National Institutes of Health under grants R01 HL091062, RC1 HL099892 and R01 HL103946, with additional support from the Donald W. Reynolds Foundation.

Johns Hopkins Medicine

Related Heart Failure Articles from Brightsurf:

Top Science Tip Sheet on heart failure, heart muscle cells, heart attack and atrial fibrillation results
Newly discovered pathway may have potential for treating heart failure - New research model helps predict heart muscle cells' impact on heart function after injury - New mass spectrometry approach generates libraries of glycans in human heart tissue - Understanding heart damage after heart attack and treatment may provide clues for prevention - Understanding atrial fibrillation's effects on heart cells may help find treatments - New research may lead to therapy for heart failure caused by ICI cancer medication

Machining the heart: New predictor for helping to beat chronic heart failure
Researchers from Kanazawa University have used machine learning to predict which classes of chronic heart failure patients are most likely to experience heart failure death, and which are most likely to develop an arrhythmic death or sudden cardiac death.

Heart attacks, heart failure, stroke: COVID-19's dangerous cardiovascular complications
A new guide from emergency medicine doctors details the potentially deadly cardiovascular complications COVID-19 can cause.

Autoimmunity-associated heart dilation tied to heart-failure risk in type 1 diabetes
In people with type 1 diabetes without known cardiovascular disease, the presence of autoantibodies against heart muscle proteins was associated with cardiac magnetic resonance (CMR) imaging evidence of increased volume of the left ventricle (the heart's main pumping chamber), increased muscle mass, and reduced pumping function (ejection fraction), features that are associated with higher risk of failure in the general population

Transcendental Meditation prevents abnormal enlargement of the heart, reduces chronic heart failure
A randomized controlled study recently published in the Hypertension issue of Ethnicity & Disease found the Transcendental Meditation (TM) technique helps prevent abnormal enlargement of the heart compared to health education (HE) controls.

Beta blocker use identified as hospitalization risk factor in 'stiff heart' heart failure
A new study links the use of beta-blockers to heart failure hospitalizations among those with the common 'stiff heart' heart failure subtype.

Type 2 diabetes may affect heart structure and increase complications and death among heart failure patients of Asian ethnicity
The combination of heart failure and Type 2 diabetes can lead to structural changes in the heart, poorer quality of life and increased risk of death, according to a multi-country study in Asia.

Preventive drug therapy may increase right-sided heart failure risk in patients who receive heart devices
Patients treated preemptively with drugs to reduce the risk of right-sided heart failure after heart device implantation may experience the opposite effect and develop heart failure and post-operative bleeding more often than patients not receiving the drugs.

How the enzyme lipoxygenase drives heart failure after heart attacks
Heart failure after a heart attack is a global epidemic leading to heart failure pathology.

Novel heart pump shows superior outcomes in advanced heart failure
Severely ill patients with advanced heart failure who received a novel heart pump -- the HeartMate 3 left ventricular assist device (LVAD) -- suffered significantly fewer strokes, pump-related blood clots and bleeding episodes after two years, compared with similar patients who received an older, more established pump, according to research presented at the American College of Cardiology's 68th Annual Scientific Session.

Read More: Heart Failure News and Heart Failure Current Events
Brightsurf.com is a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for sites to earn advertising fees by advertising and linking to Amazon.com.