Wednesday, May 17, 2006

"Leadless" ICD - Has it's time come?

There was interesting information from the "leadless" ICD front reported by Andrew A. Grace, MD, PhD from Papworth Hospital NHS Trust, Cambridge, United Kingdom at the Heart Rhythm Society Meeting in Boston, MA today:

First of all, the device is not "leadless." Rather, there are no leads placed inside blood vessels with this defibrillator, produced by Cameron Health, Inc. The device does have a lead that is tunneled beneath the skin from the upper left chest beneath just below the level of the clavicle to the level of about the breast, then tunneled laterally to the side of the chest beneath the arm. The device uses the subcutaneous lead to sense the heart rhythm and can detect rapid arrhythmias from the surface EKG created between the lead electrode and the can of the device. It's maximum shocking output is 80 joules (about 2 1/2 times existing devices). It requires no xray system to implant the device and took about 12-15 minutes on average for experienced operators to install in an operating room setting. If the ability to convert the rhythm from ventricular fibrillation to normal rhythm was excessive, a conventional defibrillator lead placed inside the blood vessel could be attached.

53 patients were studied the the information provided. The average defibrillation threshold without any internal lead was 36 joules. No inappropriate shocks occurred, even when there was an aggressive attempt to induce sensing of muscular potentials with vigorous arm movement.

It's only drawback: there was no backup pacing provided by the device, so if the rhythm is converted from ventricular fibrillation to asystole (no heart beats... and this CAN happen), then the patient still might not survive. Nonetheless, the implications for decreasing physician reimbursement for electrophysiologists (since now any surgeon could implant these) and what this will do to pressure existing device companies to drop their prices once the device reaches the mainstream US market for primary prevention of life-threatening arrhythmias, remains to be seen.


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