Subcutaneous implantable cardioverter-defibrillator.

or nearly 3 decades, the implantable cardioverter-defibrillator (ICD) has been available to patients who survived life-threatening rapid heart rhythms or are at risk of experiencing them. The ICD comprises a device generator coupled with a defibrillation lead. Traditional ICDs are implanted under the skin with the generator positioned beneath the collar bone. The defibrilla-tion lead is inserted through the veins in the chest that course to the heart, permitting direct attachment to the inside of the heart, specifically the right ventricle. Figure (A) shows an x-ray of an ICD and leads. The subcutaneous ICD (SICD) is a novel defibrillator developed over the past decade that has become available to patients in the United States this year. The SICD provides an alternative option for patients whose physicians are recommending an ICD. Manufactured by Boston Scientific, Inc, a company that makes and sells ICDs, the SICD consists of an ICD generator and a defibrillation lead, similar to a traditional ICD. However, the defibrillation lead remains completely outside the chest cavity. Figure (B) shows an x-ray of the SICD. The SICD is implanted under the left breast, and the lead is placed under the skin along the left side of the breastbone. Early experience with the SICD has shown that it can terminate life-threatening rapid heart rhythms within seconds of their detection. Patients who are candidates for an ICD should understand the differences between a traditional ICD and the SICD. The greatest advantage of the SICD is that the lead does not course through the central veins in the chest, nor is it attached to the tissue within the heart chambers. Patients who opt for an SICD avoid the need for possible lead removal, or extraction, from the central veins and heart cavity. Lead extraction is recommended in cases of lead infections , fractures, or other mechanical problems that prevent safe and effective ICD shock therapies. Although extraction remains an infrequent necessity among implantation patients, it is associated with significant risks, including death. A comparison of the SICD to a traditional ICD follows. The SICD device is substantially larger because it requires a larger battery to deliver stronger shocks during life-threatening rapid rhythms. A higher shock energy is necessary because the SICD system shocks the heart entirely from outside the chest wall. A substantial number of patients requiring an ICD also require protection from slow heart rates (pacemaker therapy) or may benefit from …