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VU first to offer new implantable defibrillator

Mar. 20, 2014, 8:39 AM

The components for the new subcutaneous implantable defibrillator are implanted just under the skin — the generator on the side of the chest and the electrode next to the breastbone.

Vanderbilt is the first hospital in Tennessee to use a new subcutaneous implantable defibrillator (S-ICD) to treat patients at risk for sudden cardiac arrest.

The S-ICD system from Boston Scientific is designed to provide the same protection as traditional ICDs, which work by delivering a life-saving electrical shock to the heart.

This newer system sits just below the skin without the need for thin, insulated wires — known as leads — to be placed into the heart itself. This leaves the heart and blood vessels untouched, providing an alternative approach for patients and physicians.

Sharon Shen, M.D.

“It’s in a very stable location. The wire itself doesn’t have to move because it’s not inside the heart. It is less prone to lead fractures or types of lead problems such as endocarditis or device infections. Having this reside outside the vascular system would help avoid those complications,” said Sharon Shen, M.D., who implanted the first adult S-ICD in a 55-year-old patient with diabetes.

Sudden cardiac arrest is an abrupt loss of heart function. Most episodes are caused by the rapid or chaotic activity of the heart, known as ventricular tachycardia or ventricular fibrillation.

The S-ICD system has a pulse generator, which powers the system, monitors heart activity, and delivers a shock if needed, and an electrode, which enables the device to sense the cardiac rhythm and serves as a pathway for shock delivery when necessary.

Both components are implanted just under the skin — the generator at the side of the chest, and the electrode beside the breastbone. Implantation can be done using only anatomical landmarks, which removes the need for fluoroscopy (an X-ray procedure that is required for standard leads to be placed in the heart).

“The subcutaneous ICD is a good option for patients with limited vascular access and those who’ve had complications from transvenous defibrillators,” Shen said. “The heart beats 30 million to 40 million times a year, so after a while, the wires can break down and fail in transvenous ICDs.”

The U.S. Food and Drug Administration granted regulatory approval for the S-ICD System in September 2012. To date, more than 2,000 devices have been implanted in patients around the world. Vanderbilt is one of only two hospitals in the state to offer it. Frank Fish, M.D., implanted the first pediatric SICD at the Monroe Carell Jr. Children’s Hospital at Vanderbilt.

Shen, an electrophysiologist (EP), came to the Vanderbilt Heart and Vascular institute in September from Northwestern University, where she earned her medical degree and did her residency, and cardiology and EP fellowships.

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