ICD's and Pacemakers
Automatic Implantable Defibrillators (AICD) OR Implantable Cardioverter Defibrillators (ICD)
Through risk stratification we can better identify those at high risk for sudden cardiac arrest, SCA, from HCM. Those HCM patients clearly at high-risk for sudden death may be candidates for an implantable cardioverter-defibrillator (ICD), a sophisticated device which is permanently implanted internally and is capable of sensing potentially lethal arrhythmias and then introducing a shock to terminate these arrhythmias and restore normal heart rhythm . At the same time, an ECG recording is generated directly by the device to precisely document the event. Recently, there has been much more experience with, and interest in, employing the ICD therapy increasing frequency in high-risk HCM patients with genetic heart diseases (such as HCM), including in children.
The ICD represents a major innovation for HCM, as it is capable of favorably changing the clinical course of HCM for many patients by preventing sudden death. In the largest study to date, the ICD automatically and appropriately intervened, aborting potentially lethal arrhythmias in individual high-risk patients at a rate of 5% per year (>40% in 10 years, if extrapolated over time). This rate of discharge was highest if the ICD was placed because of a prior cardiac arrest (11% per year), but was also substantial in those patients for whom the device was implanted for one or more of the HCM risk factors… and without a prior major clinical event (about 4% per year). Most of those patients for whom the ICD is life-saving are young and without significant symptoms.
Current technology utilizes ATP (anti-tachycardia pacing) which has the ability to pace the heart out of bad rhythms before a shock is required.
Also, over the last few years, ICDs have become smaller and much easier to implant in unobtrusive positions on the chest, requiring in most instances only an overnight hospital stay without major surgery. The generator (containing the battery) is now, on average, 2 ½ x 2 inches in circumference and less than ½ inch thick, and fits just below the clavicle. ICD leads are now introduced into the heart chamber through the veins, avoiding major surgery.
S-ICD’s are now available, trials are underway to assess there effectiveness in HCM. The S-ICD System uses a subcutaneous electrode and analyzes the heart rhythm – rather than individual beats – to effectively sense, discriminate, and convert VT/VF. the S-ICD System provides a new solution to provide therapy from SCA, without touching the heart. The generator is implanted outside of the rib cage and the lead is tunneled up the center of the chest. These devices to not have the ability to provide ATP.
The choice to implant an ICD is one that must be thought out carefully as it is not without risk or significant lifetime implications. Patients must think about how the device will impact their quality of life, both positively and negatively, what impact the device may have in career choices, how they would respond in the event of a recall or product advisory, and their responsibility to maintain the device, replace it and communicate with their physician and device manufacturer.
Pacemakers are devices implanted in the upper chest with wires running through the veins and placed in the heart. Pacemakers offer electrical impulses to your heart telling it when and how to beat. Pacemakers have been on the market for many years and are highly reliable technology. Some patients with HCM may have developed heart block or have episodes of bradycardia (slow heart rate) which may require a pacemaker to be implanted. In 2009 most patients requiring pacing in HCM will be offered a combination pacemaker/ICD an all in one unit with 2 leads.
The use of dual chamber pacemakers, DDD, for the relief of obstruction, has been a source of some controversy in the medical community. In the mid 1980s it was proposed that dual chambered pacing would relieve obstruction, eliminate most symptoms and thin the walls of the heart. This did not prove to be entirely true. In large multi- center studies (M-Pathy and PIC) we have learned that DDD pacing can reduce obstruction. However, the heart walls do not thin and symptomatic improvements have been reported to be minimal at best for many patients. The studies available suggest that a 50% decrease in gradient is probable; therefore, many patients would still be in the surgical range after pacing. Questions still remain as to the long term effect of DDD pacing. Previously, pacemakers were almost entirely implanted in older members of the population and concerns over the 30 + year effects on the heart have not been addressed. Pacing for outflow obstruction should be entered into with caution.
The use of pacemakers to combat heart block or bradycardia has been very effective and is standard practice.
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