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



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.


Patients enrolled in the MOST study with an left ventricular ejection fraction (LVEF) >35%, QRS duration (QRSd) <120 ms and no history of ventricular arrhythmias or prior implantable cardioverter defibrillators were included (LP-eligible population). Cox proportional hazards models were used to test the association between pacing mode and death, stroke or heart failure (HF) hospitalization and atrial fibrillation (AF).


Of the 2010 patients enrolled in MOST, 1284 patients (64%) met inclusion criteria. Baseline characteristics were well balanced across included patients randomized to DDDR (N = 630) and VVIR (N = 654). Over 4 years of follow-up, there was no association between pacing mode and death, stroke or HF hospitalization (VVIR HR 1.28 [0.92-1.75]). VVIR pacing was associated with higher risk of AF (HR 1.32 [1.08-1.61], P = .007), particularly in patients with no history of AF (HR 2.38 [1.52-3.85], P < .001).


In patients without reduced LVEF or prolonged QRSd who would be eligible for LP, DDDR, and VVIR pacing demonstrated similar rates of death, stroke or HF hospitalization; however, VVIR pacing significantly increased the risk of AF development.





Published Version (Please cite this version)


Publication Info

Loring, Zak, Rebecca North, Anne S Hellkamp, Brett D Atwater, Camille G Frazier-Mills, Kevin P Jackson, Sean D Pokorney, Gervasio A Lamas, et al. (2020). VVI pacing with normal QRS duration and ventricular function: MOST trial findings relevant to leadless pacemakers. Pacing and clinical electrophysiology : PACE, 43(12). pp. 1461–1466. 10.1111/pace.14100 Retrieved from https://hdl.handle.net/10161/30479.

This is constructed from limited available data and may be imprecise. To cite this article, please review & use the official citation provided by the journal.



Zak Loring

Assistant Professor of Medicine

I am a cardiac electrophysiologist specializing in the treatment of heart rhythm disorders and management of cardiac implantable electronic devices (CIEDs). My research utilizes signal processing of electrocardiographic data and novel analytic techniques to better phenotype patients and identify those for whom interventional electrophysiology procedures may be most beneficial. This includes predicting which patients with left bundle branch block may benefit from early cardiac resynchronization therapy or conduction system pacing. I also analyze population level data to identify patients at high risk for adverse sequelae of rhythm disorders who may benefit from early intervention.


Rebecca North

Biostatistician III

Camille Genise Frazier

Professor of Medicine

Kevin Patrick Jackson

Associate Professor of Medicine

Research interests include:
- optimization of device timing for Cardiac Resynchronzation Therapy (CRT)
- novel cardiac imaging technologies for CRT
- catheter ablation versus anti-arrhythmic drug for treatment of atrial fibrillation.


Sean Pokorney

Assistant Professor of Medicine

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