Reduced biventricular pacing: What is the mechanism and how to manage it?

Abstract

A 43-year-old male with a history of dilatedcardiomyopathy and a cardiac resynchronization therapy(CRT) defibrillator (Unify Quadra; St. Jude MedicalInc., St. Paul, MN, USA) implanted 5 years earlierfor primary prevention presented at the cardiac rhythmand device clinic for regular follow-up. Device interrogationshowed normal parameters (Table 1). The devicewas programmed in DDD mode at 60 ppm with sensedand paced atrioventricular (AV) delays of 120 millisecondsand 150 milliseconds, respectively. Biventricularpacing was at 50%. The patient’s clinical and echocardiographicsituation had not improved since CRT implantation.The echocardiogram revealed a severely dilatedleft ventricle with an ejection fraction of 20%. Thedevice diagnostic summary showed 48% prematureventricular complexes (PVCs), inhibiting biventricularpacing (Fig. 1). However, there were no PVCs observedduring device interrogation. What are the next steps?What caused the reduced biventricular pacing, and whatcircumstances should be considered in this case?