Patients with heart failure often have intraventricular conduction delays (such as bundle branch blocks), which cause the ventricles to contract dyssynchronously, in an inefficient manner. This is the rationale behind the implantation of biventricular pacing devices to restore synchrony.
The effect of cardiac resynchronization on morbidity and mortality in heart failure, in this week’s NEJM, looked at biventricular pacing plus medical therapy (409 patients) vs. medical therapy alone (404 patients) in patients with class III or IV heart failure.
Patients in the European multicenter CARE-HF study had a QRS interval of at least 150 msec, or 120-149 msec plus echocardiographic evidence of ventricular dyssynchrony, in addition to heart failure and sinus rhythm. Enrolled patients were then randomized to implantation of a device or no implantation, in a non-blinded fashion.
After mean follow-up of 2.5 years, the number of deaths (mainly cardiovascular) in the device group was significantly lower (20% vs. 30%).
Patients who were hospitalized for worsening heart failure comprised 18% of the device group vs. 33% of the non-device group.
Ejection fraction and indices of symptom status were also improved in the device group.
These results were fairly consistent across a number of subgroups, and the improvements occurred rather gradually and progressively over time.
An editorial by Jarcho points out that device implantation is not always easy, since pacing of the left atrium via the coronary sinus is technically a bit tricky. He also points out that this study looked at the benefit of bi-ventricular pacing without ICD placement. There is a suggestion that bi-V pacing may reduce the additional benefit of ICD placement, but it is unlikely that this hypothesis will be tested by a clinical trial, so most patients will end up with a dual-purpose device.
Areas of uncertainty remain its role in patients with atrial fibrillation, and the utility of basing the criteria for device implantation on echocardiographic indices of ventricular dyssynchrony.