Left bundle branch area pacing in atrial fibrotic cardiomyopathy manifesting as atrial standstill: two case reports and mechanistic insights

Atrial standstill (AS) is a rare arrhythmogenic disorder characterized by the complete absence of atrial electrical and mechanical activity, most commonly resulting from atrial fibrotic cardiomyopathy (AFC). Optimal management remains challenging, particularly when selecting an appropriate pacing strategy. Left bundle branch area pacing (LBBaP) provides physiological ventricular activation; however, its role in patients with AS is not well established. We report two patients managed with tailored LBBaP. Case 1: A 41-year-old female with biatrial electrical silence confirmed by 3D electroanatomic mapping received a single-chamber LBBaP pacemaker (implant-paced LVAT 71.97 ms; QRS narrowed from 124 to 93 ms). Case 2: A 36-year-old male, underwent dual-chamber pacing with an atrial septal lead and an LBBaP. After pacing, the pulmonary arterial systolic pressure decreased from 44 mmHg (native rhythm) to 27 mmHg. AS management requires a thorough electrophysiological study to characterize the atrial substrate, which directly dictates the pacing strategy. Diffuse fibrosis necessitates single-chamber LBBaP to ensure ventricular synchrony, whereas localized viability allows dual-chamber pacing to restore atrioventricular synchrony. Anticoagulation is mandatory owing to the high thromboembolic risk, irrespective of the pacing mode. AS management requires a substrate-guided approach. LBBaP represents a physiologically aligned alternative to conventional RVP; however, head-to-head comparative evidence is required. Atrial lead implantation is feasible in cases of localized viable tissue. Anticoagulation is mandatory regardless of the pacing mode.