Comparing the largest registry of implantable cardioverter-defibrillator (ICD) implants in the United States with 2 primary prevention randomized clinical trials, researchers found that patients who met certain criteria and who received a primary prevention ICD in clinical practice had survival that was not significantly different from patients who received an ICD in the clinical trials, findings that support the continued use of primary prevention ICDs in similar patients seen in clinical practice, according to a study in the January 2 issue of JAMA.
“The implantable cardioverter-defibrillator is a highly effective therapy for preventing sudden cardiac death in patients with heart failure. However, the outcomes of this therapy in routine clinical practice are largely uncertain. Because randomized clinical trials generally enroll patients with fewer comorbidities [other illnesses] and are usually conducted in highly controlled and monitored settings, the results of the primary prevention ICD trials may not be generalizable to routine clinical practice,” according to background information in the article. The authors add that whether these findings “are generalizable to clinical practice needs to be investigated, especially given the cost and potential complications associated with this device, such as infection and lead and device failure.”
Sana M. Al-Khatib, M.D., M.H.S., of the Duke Clinical Research Institute, Durham, N.C., and colleagues conducted a study to determine whether a difference in survival exists between trial-eligible patients who receive a primary prevention ICD as documented in a large national registry and similar patients who received an ICD in the 2 largest primary prevention clinical trials, MADIT-II (n = 742) and SCD-HeFT (n = 829). The study consisted of a retrospective analysis of data for patients enrolled in the National Cardiovascular Data Registry ICD Registry between January 1, 2006, and December 31, 2007, meeting the MADIT-II criteria (2,464 propensity score-matched patients) or the SCD-HeFT criteria (3,352 propensity score-matched patients). Mortality data for the registry patients were collected through December 31, 2009. The median (midpoint) follow-up time in MADIT-II, SCD-HeFT, and the ICD Registry was 19.5, 46.1, and 35.2 months, respectively. Patients receiving ICDs in clinical practice were significantly older and had more comorbidities than patients enrolled in the clinical trials.
After analysis of the data, the authors found no significant difference in survival between MADIT-II-like patients in the ICD Registry and MADIT-II patients randomized to receive an ICD (2-year mortality rates: 13.9 percent vs. 15.6 percent). Also, the survival of MADIT-II-like patients in the ICD Registry was significantly better than the survival of MADIT-II patients randomized to receive medical therapy (2-year mortality rates: 13.9 percent vs. 22 percent).
There was also no significant survival difference between SCD-HeFT-like patients in the ICD Registry and patients randomized to receive ICD therapy in SCD-HeFT (3-year mortality rates: 17.3 percent vs. 17.4 percent). The survival of SCD-HeFT-like patients in the ICD Registry was significantly better than the survival of SCD-HeFT patients randomized to placebo (3-year mortality rates: 17.3 percent vs. 22.4 percent).
“Importantly, the generalizability of these results held even after limiting the analyses to patients 65 years and older,” the researchers write.
The authors note that prior work in other fields has demonstrated that it is often challenging to generalize the findings from randomized clinical trials to clinical practice. “Patients enrolled in randomized clinical trials of primary prevention ICD therapy were monitored carefully over the course of the trials, and physicians who implanted and followed those devices were highly experienced. This level of care may not occur in real-world, practice.”
“... it is reasonable to question whether the results of the trials can be expected in clinical practice. Through propensity score matching and adjustment for differences between registry patients and patients enrolled in the clinical trials, our matched sample became similar to patients enrolled in the clinical trials. This enabled us to address the concern that the care of patients in the highly controlled and monitored setting of clinical trials compromises the external validity of the results.”