Subcutaneous ICD Shows Safety, Efficacy in Early Study


BOSTON — A subcutaneously placed implantable defibrillator that doesn't use a transvenous lead showed safety and efficacy in initial clinical testing in 55 patients followed for 30 days.

The subcutaneous implantable cardioverter defibrillator (S-ICD) detected 100% of ventricular episodes during the study and had a fibrillation conversion efficacy of more than 98%, comparable to those of conventional ICDs, Dr. Ian G. Crozier said at the Heart Rhythm Society's annual meeting. The S-ICD also involves an easy and low-risk implantation without need for fluoroscopy that may reduce the risk barrier and make ICD therapy a more acceptable option for certain patients and their physicians.

The new device “is innovative and potentially very important,” said Dr. Richard L. Page, head of the division of cardiology at the University of Washington in Seattle. “Being able to put in an ICD that does not require fluoroscopy or vascular access has remarkable potential for the future,” he said in an interview. Avoiding vascular access means that patients “won't be as prone to intravascular infection as they are with conventional pacemakers and defibrillators.”

The S-ICD is made by Cameron Health, and has taken 8 years to develop, said Dr. Crozier, a cardiac electrophysiologist at Christchurch Hospital, New Zealand. Cameron Health sponsored the study. Dr. Crozier said that his financial relationship with the company is limited to research grants and fellow support. Dr. Page said that he had no financial relationships to disclose.

The device is 69 cc in volume, weighs 145 g, and can deliver a shock of up to 80 j. It is believed to have a longevity of 5 years. It is placed through an incision at the sixth rib, over the heart's apex, and is positioned using anatomic landmarks. The three electrodes are drawn through to their locations under the skin with a tunneling tool.

The 55 patients had conventional indications for an ICD. The study excluded patients who also required pacing because the device does not have pacing capability. It also excluded patients with a left ventricular ejection fraction of 30% or less. The patient's average age was 56, 80% were men, and their average LVEF was 34%. The testing protocol was successfully completed in 53 patients, with 52 (98%) passing conversion efficacy testing. The device detected all 137 ventricular fibrillation episodes during testing and emitted a shock an average of 14 seconds after each episode began, Dr. Crozier reported.

Five adverse events occurred during placement and follow-up, four of which were device related. In two cases, device malfunctions were resolved by reprogramming. The other two cases required repositioning of the leads.

The S-ICD is especially suitable for younger patients who need an ICD because they face the greatest risk from long-term placement of transvenous leads, Dr. Crozier said in an interview.

'An ICD that does not require fluoroscopy or vascular access has remarkable potential for the future.' DR. CROZIER

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