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Hopkins Pulse - A Less Invasive Cardioverter Defibrillator

Hopkins Pulse Spring 2015

A Less Invasive Cardioverter Defibrillator

Date: June 9, 2015

Electrophysiologist Alan Cheng
Electrophysiologist Alan Cheng

For people who have a dangerous irregular heartbeat and are at high risk of sudden cardiac arrest, an implanted cardioverter defibrillator can be lifesaving. Even so, the device has an Achilles’ heel: the possibility of infection or a break in the wire or electrodes going to the heart.

But Johns Hopkins electrophysiologist Alan Cheng is now providing another option to selected patients: a defibrillator whose wires are placed just under the skin instead of into cardiac vessels or the heart itself.

“The device senses off the lead placed under the surface of the chest,” says Cheng. “The main advantage is that patients will not face the risk of difficult lead extractions in the future, but there are some drawbacks.”

The battery needs to be replaced after about four years. The device is also about twice as large as a traditional implanted cardioverter defibrillator, so not all patients — especially those who are very thin — are eligible. In addition, because the detection algorithm uses an electrocardiogram sensed through the wire under the skin, certain patients may not qualify for the device due to their particular condition.

While it can be used for rapid heartbeat conditions like ventricular tachycardia or ventricular fibrillation, it does not have standard pacing support for patients with slower-than-normal heart rates. Nevertheless, it is a good option for some people with limited vascular access or other issues placing them at high risk for bloodborne infections.

The implantation requires the patient to have general anesthesia but not fluoroscopy imaging. The device’s pulse generator is placed right below the armpit. Then, an electrode on the device is tunneled across the heart above the rib cage and is attached to the connective tissue beneath the skin.

Cheng says time will tell how effective the new device will be. “We have 30 years of experience with the traditional implantable cardioverter defibrillator versus about one year with the new one,” says Cheng. But, he adds, it does hold promise for patients who are good candidates.