Left Bundle Branch Area Pacing in Repaired Tetralogy of Fallot Evaluated by Advanced Echo Parameters.

BACKGROUND: Adults with repaired tetralogy of Fallot (rTOF) frequently develop right bundle branch block (RBBB)-related dyssynchrony and progressive heart failure. The role of left bundle branch area pacing (LBBAP) in this population remains limited. CASE SUMMARY: A 60-year-old man with rTOF presented with monomorphic ventricular tachycardia and worsening heart failure despite being on an optimal medical therapy. After cardioversion, electrocardiography demonstrated sinus rhythm with RBBB and left anterior fascicular block (QRS = 166 ms), while echocardiography revealed biventricular dysfunction with significant mechanical dyssynchrony. A dual-chamber implantable cardioverter-defibrillator with LBBAP was implanted. At 3-month follow-up, QRS duration narrowed, functional status improved, and echocardiographic indices of left and right ventricular systolic function, strain, and myocardial work improved. DISCUSSION: This case suggests that LBBAP may be associated with improved electrical and mechanical synchrony in cases of rTOF with RBBB. TAKE-HOME MESSAGES: LBBAP may represent a promising physiologic resynchronization strategy in selected adults with congenital heart disease and RBBB. Advanced echocardiography can quantify serial changes in ventricular function and mechanics after pacing.