CMS has posted a new technology assessment for implantable cardioverter-defibrillators (ICDs) addressing the evidence for use of ICDs for “primary prevention” of sudden cardiac death (SCD)—prevention of SCD in patients who have not yet experienced a sustained ventricular tachyarrhythmia, but who have risk factors for it. The researchers at Tufts Evidence-based Practice Center, working under contract to the Agency for Healthcare Research and Quality (AHRQ), examined data from MEDLINE and the Cochrane Central Trials Registry to investigate three key questions:
What were the comparative differences in survivorship between patients who received:
- ICD versus no ICD;
- ICD with anti-tachycardia pacing (ATP) versus ICD alone; and
- ICD with cardiac resynchronization therapy (CRT-D) versus ICD alone?
- What were the rates of early and late adverse events and inappropriate shocks after ICD implantation?
- What were the eligibility criteria and evaluation methods for patients included in comparative studies and what was the average risk of SCD for patients in the control groups?
According to the report, strong evidence supports the effectiveness of ICD therapy for primary prevention of SCD, versus no ICD therapy, to reduce all-cause mortality and SCD in patients with reduced left ventricular ejection fraction and ischemic or nonischemic cardiomyopathy beyond the immediate post-MI or coronary revascularization periods. Researchers found that for every 6.2 to 22 ICDs implanted (depending on the study), 1 death was prevented within 3 to 7 years (again, depending on the study). Between 2 to 3 and 11 ICDs were needed to prevent one arrhythmic death.
Researchers did not find statistically significant differences for all-cause mortality or SCD across subgroups by age, sex, and other patient characteristics. The report suggests, however, that ICDs may be more effective for patients with more distant coronary revascularization as compared with recent surgery. In contrast to studies of patients with more distant MIs, studies of patients with recent MIs (within 31 or 40 days) showed no reduction in all-cause mortality. Researchers concluded that there is insufficient evidence regarding the relative effect on all-cause mortality among patients who receive CRT-D compared to those who receive ICD alone.
According to the report, in-hospital adverse events are infrequent, with approximately 3 percent of ICD patients experiencing an early adverse event and approximately 1 percent experiencing a serious early adverse event. Evidence suggests that up to one-fifth of ICD patients (3 to 21 percent) receive an inappropriate shock from the ICD during the first 1 to 5 years.