Longer-duration QRS with LBBB may have better CRT outcomes

The use of cardiac resynchronization therapy (CRT) may not be a one-size-fits-all option for heart failure and left ventricular dysfunction patients. A study published in the Aug. 14 issue of JAMA found that undergoing CRT debrillator (CRT-D) implantation with a QRS duration of 150 milliseconds (ms) or greater and left bundle-branch block (LBBB) is associated with better outcomes than undergoing CRT-D with a shorter QRS duration or no LBBB.

The participants were all 65 years old or older and had a CRT-D implantation between April 2006 and December 2009, resulting in a cohort of 24,169 participants. They were all enrolled in fee-for-service Medicare. As outcomes, the researchers assessed all-cause mortality, all-cause readmission, cardiac-related readmission and complications. Participants were followed for three years.

“The unadjusted rate and adjusted risk of both three-year mortality and of one-year all-cause readmission were lowest among patients with LBBB and QRS duration of 150 ms or greater,” wrote the authors, led by Pamela N. Peterson, MD, MSPH, of Denver Health Medical Center in Colorado.

Three-year mortality among patients with LBBB and QRS duration of 150 ms or greater was 20.9 percent. For patients with a QRS between 120 and 149 ms and LBBB, it was 26.5 percent. Among non-LBBB and shorter-duration QRS patients, the mortality rate was 32.2 percent. Readmission rates for the three groups, respectively, were 38.6 percent, 44.8 percent and 45.7 percent.

The only complication observed was a greater risk of infection at three years among patients with no LBBB and a shorter QRS compared with those with LBBB and a longer QRS.

“The observed outcomes of patients with LBBB and a wide QRS duration are particularly notable, given that both LBBB and prolonged QRS duration have been shown to be independent predictors of mortality among patients with left ventricular systolic dysfunction without CRT,” they explained. “Because CRT addresses dyssynchrony, it is not surprising that LBBB and wide QRS duration in CRT recipients were associated with a lower risk of mortality.”

Their findings, they added, support the American College of Cardiology/American Heart Association/Heart Rhythm Society guidelines for device-based therapy of cardiac rhythm abnormalities that recommend CRT in certain patients based on QRS morphology and duration.

“Identification of patients likely to benefit from CRT is particularly important, because CRT defibrillator implantation is expensive, invasive, and associated with important procedural risks.”