Many MADIT-CRT Patients Had PVC Cardiomyopathy Possibly Responsive to Ablation

Pam Harrison

March 02, 2015

ROCHESTER, NY — About a third of patients with nonischemic disease in a major cardiac resynchronization therapy (CRT) trial had cardiomyopathy related to premature ventricular contractions (PVCs) that might have been amenable to catheter ablation or other non-CRT therapy, suggests a recent report in the Annals of Noninvasive Electrocardiology[1]. Those PVCs had been found to originate from the right ventricular outflow tract (RVOT) and in many cases were considered related to patients' nonsustained ventricular tachycardia (NSVT).

Often the cause of  nonischemic cardiomyopathy (NICM) isn't well characterized in individuals, "so when we see a high PVC burden from a very specific site, it raises the question whether or not it could be a PVC-induced cardiomyopathy," Dr Mehmet K Aktas (University of Rochester Medical Center, NY) told heartwire .

"That's what we saw here: in patients with NICM, a good number of them have PVCs likely originating from the RVOT, and we might then ask, if we control these PVCs either through medicines or through catheter ablation, could we impact the substrate and maybe improve the cardiomyopathy? So this was the exciting part of this study," said Aktas, lead author of the analysis based on patients from the MADIT- CRT trial.

A total of 146 patients enrolled in the multicenter trial were found to have >5000 PVCs on 24-hour Holter monitoring. Patients were categorized based on their likely site of PVC origin: the RVOT, left ventricular outflow tract (LVOT), sinus of Valsalva, or non–outflow tracts. Those with non–outflow-tract PVCs numbered 75, or 51% of the cohort.

The primary end point of the analysis was a heart-failure event or death, while secondary end points included VT/ventricular fibrillation (VF) and the combined end point of VT/VF or death by outflow-tract vs non–outflow-tract PVC site. There were no significant differences in any of the comparisons.

Hazard Ratio (95% CI) for Outcomes in Patients With Outflow-Tract vs Non–Outflow-Tract PVCs in MADIT-CRT, Multivariate Analysis

End point Hazard ratio 95% CI P
HF or death 1.4 0.7–2.8 0.3
VT/VF 1.0 0.6–1.8 1.0
VT/VF or death 0.9 0.5–1.6 0.7

The median total PVC count was slightly higher, at 8950 per 24 hours in NICM patients, compared with 8807 per 24 hours in ischemic cardiomyopathy patients. Patients with NICM were, however, more likely to experience PVCs originating from the RVOT, whereas non–outflow-tract PVCs were more commonly seen in patients with ischemic cardiomyopathy. As the authors observe, nearly one-third of patients in both ischemic cardiomyopathy and NICM groups had NSVT with a morphology matching the predominant PVC.

Frequent PVCs can lead to ventricular dyssynchrony and be a nonischemic cause of cardiomyopathy, and "in such patients, successful PVC ablation has been shown to improve LV function, and in some cases complete recovery of LV function has been reported," write Aktas and his colleagues.

"Interestingly, nearly one-third of patients in both groups [in the current analysis] had NSVT with a morphology matching the predominant PVC, and this may have implications when trying to decide on whether ablation of these PVC sites may improve a patient's VT burden."

MADIT-CRT was supported by Boston Scientific; no financial relationships were reported.

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