Abstract 4362838: Dynamic Left Ventricular Outflow Tract Obstruction in a Patient Post Transcatheter Aortic Valve Replacement Induced by Left Bundle Branch Area Pacing Following Atrioventricular Junction Ablation

Description of Case: An 81-year old-female with paroxysmal atrial fibrillation (AF) and severe aortic stenosis presented with AF with rapid ventricular response and volume overload. She had undergone an uncomplicated transcatheter aortic valve replacement (TAVR) 14 days prior with post procedure echocardiogram (TTE) demonstrating ejection fraction greater than 70%, a mean gradient across the TAVR valve of 11 mmHg, and mild mitral regurgitation (MR). Management included diuresis, rate control, and a failed cardioversion. TEE at the time of cardioversion, while tachycardic, demonstrated systolic anterior motion of the mitral valve (SAM) but no gradient across the aortic valve. She underwent atrioventricular (AV) junction ablation and placement of a left bundle branch area pacing (LBBAP) lead. Immediately post-procedure, she developed acute dyspnea and a new systolic murmur. Right heart catheterization revealed pulmonary artery pressure 90/30 mmHg and wedge pressure 39 mmHg with a prominent v-wave, and cardiac index of 1.6 L/min/m 2 . A simultaneous LV-AO pressure tracing demonstrated a gradient of 52 mmHg. TTE revealed a late-peaking doppler signal across the aortic valve with a peak velocity of 4 m/s, SAM, and severe MR. An Impella CP was placed for circulatory support. TTE revealed the LBBAP lead was adjacent to a 1.8 cm basal septal bulge (Figure 1). The next day, a transvenous RV apical pacing lead was placed, and simulatenous LV-AO pressure tracing revealed a peak-to-peak gradient of 45 mmHg during LBBAP, which immediately decreased to 5 mmHg with RV apical pacing (Figure 2). This led to a decrease in MR from severe to mild. Given the dynamic nature of the obstruction, alcohol septal ablation was performed. The Impella CP was removed and vasopressors were weaned. A permanent RV apical lead was added and used for pacing. The patient remained hemodynamically stable and was discharged to rehabilitation. Discussion: This case highlights a report of dynamic left ventricular outflow tract (LVOT) obstruction precipitated by LBBAP in a patient post-TAVR who previously did not have evidence of LVOT obstruction. Previously, RV apical pacing was a seldom used treatment for obstructive hypertrophic cardiomyopathy. Changing the pacing location to RV apical pacing instantly resolved the LVOT obstruction highlighting the need to be wary of pacing strategies in post TAVR patients who may have septal hypertrophy and may be at risk of LVOT obstruction secondary to LBBAP.