LAUSR

Introduction Pseudo-pacemaker syndrome due to a prolonged PR interval is a recognized entity that can lead to poor exercise tolerance related to atrioventricular (AV) dyssynchrony. This can manifest echocardiographically with diastolic mitral regurgitation (MR). Implantation of a dualchamber pacemaker with shorter programmed AV delay may improve AV synchrony, symptoms, and exercise tolerance. Traditionally, a dual-chamber pacemaker with a right atrial lead and right ventricular (RV) lead has been used; however, RV pacing causes interventricular dyssynchrony and, over the long term, can cause pacing-induced cardiomyopathy. His bundle pacing (HBP) more closely mimics physiological AV conduction, but HBP is sometimes limited because of the lower success rate and higher mean thresholds and may often require longer pulse widths in comparison to RV pacing. The reported success rate for HBP is in the range of 80%–90% in clinical trials, with a mean threshold of 1.2–2.0 V. We present an interesting case of a patient with a markedly prolonged PR interval after AV nodal reentrant tachycardia ablation leading to AV dyssynchrony, diastolic MR, and exercise intolerance who was treated with subvalvular HBP with excellent pacing thresholds and improved exercise tolerance.