New Device Restores Normal Heartbeat

Sudden cardiac arrest risk may drop with implanted defibrillator to treat dangerous heart rhythms

(RxWiki News) For some with an abnormal heartbeat, an implanted device can restore a normal rhythm and prevent the heart from stopping. The device delivers a shock that can put the heart back on track.

Many individuals have experienced mild arrhythmia where the heart temporarily races, pounds or feels like it has skipped a beat.

If the irregular heartbeat becomes severe enough to cause fainting or the heart to stop pumping properly, a small battery-powered device called an implanted cardioverter defibrillator (ICD) can be placed inside the body to monitor the heart's activity and provide impulses that can prevent sudden cardiac arrest. 

While a traditional ICD requires placing wires inside the heart or on its surface, a new type of ICD may restore a healthy beat without touching the heart, according to a new study.

"Ask a doctor about an implantable cardiac defibrillator to treat arrhythmia."

Martin Burke, DO (doctor of osteopathic medicine), a professor of medicine and director of the Heart Rhythm Center at the University of Chicago, served as senior author of this study testing a new subcutaneous implantable cardiac defibrillator (S-ICD® System).

Subcutaneous means the device is placed under the skin with a lead inserted along the left side of the breastbone. It is strategically placed to sense and defibrillate the heart (stop the arrhythmia) without any components having to touch the heart.

Doctors do not need to use X-ray guidance to implant the S-ICD, and scientists say that concerns are fewer regarding broken lead wires, vessel damage, vessel infection and scarring that makes traditional device removal difficult.

Dr. Burke told dailyRx News, "Inserting a subcutaneous electrode is simpler and more predictable than inserting an electrode in the heart where many turns and care must be taken to avoid perforating the heart wall and/or damaging the heart valve. These important anatomic areas are avoided as is the potential trauma to them making the long term implant safer."

In this study, 314 patients, with an average age of 52, had the S-ICD implanted.

During an average 11-month follow-up, 21 patients experienced 38 episodes of ventricular fibrillation or ventricular tachycardia.

Ventricular fibrillation is a life-threatening arrhythmia caused by fast, uncoordinated fluttering of the ventricles, or lower chambers of the heart. Ventricle tachycardia is also an arrhythmia characterized by a fast heartbeat.

The upper chambers of the heart are called the atria. These chambers can experience arrhythmia as well, but ventricle arrhythmia is often more severe in interrupting the heart’s ability to supply blood to the body. "The S-ICD has not been studied to detect atrial signals rather concentrating on ventricular or lower chamber signals as these signals are easier to detect," said Dr. Burke.

Ventricle arrhythmias can lead to sudden cardiac death, which accounts for about 300,000 deaths annually in the US, according to the National Institutes of Health. About 75 to 80 percent of sudden cardiac deaths are due to ventricular fibrillation.

The Texas Heart Institute Heart Information Center says that tachycardia is usually corrected with very small electrical impulses, but fibrillation may require a "shock” that can feel like a sudden jolt or thump to the chest.

In this investigation, Dr. Burke and his team reported that the S-ICD successfully restored a normal heartbeat to all patients who developed a ventricular arrhythmia.

The study authors noted, however, that 41 patients (13 percent) received shocks that were not needed because they weren’t preceded by a dangerous heart rhythm.

Overall, the results surpassed the benchmarks used by the US Food and Drug Administration (FDA) for evaluating the safety and effectiveness of the new device.

Compared with the FDA goal of 79 percent, just under 100 percent of S-ICD patients were free of complications 180 days following implantation.

Also, when the S-ICD System was tested on an abnormal rhythm that was purposely induced, it was 100 percent effective in detecting and reversing ventricular fibrillation, exceeding the FDA goal by 12 percent.

Participants will continue to be followed to measure the effectiveness of the device over time. The new device has been available in Europe and New Zealand since 2009. The FDA approved it in 2012.

Scientists wrote that patients with certain types of pacemakers, and those with symptoms related to a slow heartbeat, should not use an S-ICD. Those expected to benefit from the device include patients on dialysis and those with birth defects related to the heart.

"The ideal candidate for the subcutaneous ICD would include patients who pass the pre-implant electrical screening process and have no blood vessel access to the heart or those born without enough heart chambers to accommodate an electrode into the heart," said Dr. Burke in an interview with dailyRx News. "Other obvious groups are patients who have had or are at high risk of blood infection with a chronic electrode in the blood vessel and heart."

Research comparing a traditional ICD with the S-ICD is underway.

When it comes to cost, Dr. Burke told dailyRx News that the subcutaneous ICD system is about 10 to 15 percent more expensive than a comparable traditional ICD system.

"There is less supply of the device due to its limited manufacture, and the 10 years of research and development leading to FDA approval last year was expensive," he said. "The cost savings related to a safer and less morbid entirely subcutaneous device system is part of on-going study with data not available to date. The durability of the implant materials and implant site will likely make complications of long-term implant and battery replacement less, thereby justifying the higher cost."

This study was published on August 26 in the American Heart Association journal Circulation. The study was funded by Cameron Health Inc. and then by Boston Scientific Corporation following its acquisition of Cameron Health Inc.

Review Date: 
August 23, 2013