Some patients treated with cardiac resynchronization therapy-defibrillators (CRT-Ds) may qualify for pacemaker mode. After long-term improvements were seen with some patients, researchers posited that when left ventricular ejection fraction (LVEF) normalizes and it’s time to change the batteries, it may also be time to flip the switch from D to P.
Physicians followed patients from the MADIT-CRT (Multicenter Automatic Defibrillator Implantation Trial with Cardiac Resynchronization Therapy) study, going beyond the original 12 months through a mean of 2.2 years. Patients who had echocardiograms at baseline and 12 months were included.
Martin H. Ruwald, MD, PhD, of the Heart Research Follow-up Program at the University of Rochester Medical Center in New York, and colleagues monitored three groups: patients with LVEF of 30 percent or less, LVEF of 36-to-50 percent and LVEF of greater than 50 percent.
Patients were monitored for appropriate implantable cardioverter device (ICD) therapy for ventricular tachyarrythmia, heart failure or death and inappropriate ICD therapy. Appropriate therapy occurred in 14.5 percent of patients. Heart failure or death occurred in 14 percent of patients and 10 percent experienced inappropriate ICD therapy. Risks, however, decreased with improved LVEF function.
Over the course of the study, 79 percent of patients improved LVEF to the 36-to-50 percent range. While improvements to risk of ventricular tachyarrhythmias were seen in all groups, 7.3 percent of patients achieved LVEF normalization of more than 50 percent.
Further, they found that patients who reached normalization met several of six criteria: being female, no prior MI, left bundle branch block QRS morphology, a baseline LVEF of less than 30 percent, at baseline LV end-systolic volume of 170 mL or less and a baseline left atrial volume of 45 ml/m 2 or less.
Patients with LVEF normalization with all six criteria exhibited no ventricular tachyarrhythmias. Those patients whose LVEF had normalized also experienced very low risk of heart failure or death. However, they remained at high risk for inappropriate shock.
“A synthesis of these results provide evidence that patients with CRT-D devices who achieve LVEF normalization could be considered for CRT-P therapy at the time of generator replacement if no VTA(s) [ventricular tachyarrhythmias] have occurred,” Ruwald et al wrote.
However, they did caution that the study averaged fewer years in length than the average device lasts and further understanding of long-term impacts and benefits may need to be considered. Also, they noted, CRT-P may be more appropriate for some patients from the start, if they have a nonischemic myocardiopathy, small atrial and ventricular volumes, no prior ventricular arrhythmias, are female, and are in the LVEF range of 30-to-35 percent.
This study was published online Oct. 9 in Circulation.