ACC: CRT-D therapy, how beneficial is it?
NEW ORLEANS—Can early interventions with cardiac resynchronization  therapy plus defibrillation (CRT-D) really improve outcomes? This is the question N.A. Mark Estes, director of the cardiac arrhythmia center at Tufts New England Medical Center, Boston, set out to answer during a plenary session April 4 at the American College of Cardiology scientific sessions.

“CRT-D improves echo parameters, symptoms, hospitalization and mortality in NYHA Class III or IV patients at that advanced end of the spectrum who have left ventricular systolic dysfunction, sinus rhythm and a prolonged QRS duration,” Estes offered.

Estes said that 18 “robust” randomized trials over the last decade back up these results and conclusively show similar patterns and trends.

In fact, overall, the trials have shown that CRT can lead to a 22 percent relative risk reduction in all-cause mortality and a 37 percent reduction in overall heart failure (HF) hospitalizations. These results were on top of both medical and ICD therapy.

Additionally, Estes said that NYHA Class II patients realized a relative risk reduction of 17 percent for mortality and 29 percent for HF hospitalization when CRT was used.

However, Estes noted that there was “poor correlations between the 17 most frequently used definitions of CRT response.” And in a previous trial, researchers found that 95 percent of people would respond by one factor, however, using different criteria in a different trial, 95 of people would have been nonresponders.

“We have really advanced the science [CRT] by using endpoints of all-cause mortality, HF hospitalizations and reverse remodeling,” Estes noted. He offered that these three factors are what should be looked at as valid endpoints for assessing outcomes in patients with less advanced HF Class I and Class II, and in some trials, Class III patients.

However, Estes did offer that randomized clinical trials (RCTs) may overestimate the benefit of CRT while underestimating the risk due to patient selection. In addition, he offered that CRT has not yet been proven to be effective in atrial fibrillation (AF) patients, and said that results from RCTs may not be reproducible in clinical practice.

Estes said that there is no uniform definition of CRT response. And while CRT has been approved for NYHA Class I HF patients and those with ejection fractions of less than 35 percent in Europe, the FDA has approved CRT for Class II non-ischemic patients with ejection fractions greater than 30—these decisions are based off the results of the MADIT-CRT trial.

Additionally, Estes said that previous studies have shown that women see twice the benefit as men with CRT therapy and non-ischemic patients and those with left bundle branch block (LBBB) saw more of a benefit.

And while certain patients may fair better with CRT, Estes offered that the therapy may not improve quality of life and functional outcomes like a six-minute walk. However, he did offer that early intervention with CRT does significantly improve outcomes such as those mentioned above.

Estes concluded that larger, prospective clinical trials must be undertaken to evaluate CRT in certain patient subsets.