VVI pacing with normal QRS duration and ventricular function: MOST trial findings relevant to leadless pacemakers

BACKGROUND Leadless pacemakers (LPs) provide ventricular pacing without the risks associated with transvenous leads and device pockets. LPs are appealing for patients who need pacing, but do not need defibrillator or cardiac resynchronization therapy. Most implanted LPs provide right ventricular pacing without atrioventricular synchrony (VVIR mode). The Mode Selection Trial in Sinus Node Dysfunction (MOST) showed similar outcomes in patients randomized to dual-chamber (DDDR) versus ventricular pacing (VVIR). We compared outcomes by pacing mode in LP-eligible patients from MOST. METHODS Patients enrolled in the MOST study with an left ventricular ejection fraction (LVEF) >35%, QRS duration (QRSd)