Although clinical trials have established the ICD as the best currently available therapy to prevent sudden cardiac death in patients with heart failure, some uncertainties remain regarding preventive use of ICDs in patients seen in clinical practice of patients enrolled in randomized clinical trials of prophylactic (preventive) ICDs, the median left ventricular ejection fraction (LVEF; the percentage of blood that is pumped out of a filled ventricle as a result of a heartbeat) is well below 30 percent. Because a large number of prophylactic ICDs in the United States are implanted in patients with an LVEF between 30 percent and 35 percent, understanding outcomes associated with the ICDs in such patients is important. The Centers for Medicare & Medicaid Services have designated these patients as an important subgroup for whom more data on ICD effectiveness are needed, according to background information in the article.
Sana M. Al-Khatib, M.D., MH.S., of the Duke University Medical Center, Durham, N.C., and colleagues compared survival in Medicare beneficiaries in the National Cardiovascular Data Registry ICD registry with an LVEF between 30 percent and 35 percent who received an ICD during a heart failure hospitalization with similar patients in the Get With The Guidelines-Heart Failure database with no ICD. The analysis was repeated in patients with an LVEF less than 30 percent.
There were no significant differences in the baseline characteristics of the matched groups (n = 408 for both groups). At 1 year, 24.5 percent of ICD patients died vs 24.9 percent of non-ICD patients. At 3 years, 51.4 percent of the ICD patients died, compared with 55.0 percent of the non-ICD patients, a significantly lower risk of death among patients with an LVEF between 30 percent and 35 percent who received an ICD. Presence of an ICD also was associated with better survival in patients with an LVEF less than 30 percent (3-year mortality rates: 45.0 percent vs 57.6 percent).
The authors write that although the difference in absolute risk by 3 years was not large (3.6 percent), it was significant and close in magnitude to what was observed in other clinical trials of prophylactic ICDs. "These results support guidelines' recommendations to implant a prophylactic ICD in eligible patients with an LVEF of 35 percent or less."