Introduction: The dyssynchronous electrical activation of the ventricles may worsen underlying aortic stenosis. Left bundle branch pacing (LBBP) via a transventricular septal approach could be an alternative physiological pacing modality for patients with atrioventricular block (AVB), allowing the preservation of left ventricle synchronization and a decrease in left ventricular end-systolic volume.
Case report: We report the case of a 77-year-old woman admitted for lower limb edema, easy fatigue and orthopnea. Her cardiological history included chronic heart failure with preserved ejection fraction, chronic coronary syndrome and severe aortic stenosis treated with coronary artery bypass grafting (CABG) and surgical aortic valve replacement (SAVR). Subsequently, transcatheter valve-in-valve aortic valve implantation (TAVI) was performed due to prosthetic aortic valve stenosis.
The admission EKG revealed bigeminal sinus rhythm, first-degree AVB and left bundle branch block (LBBB). Close EKG monitoring during hospitalization revealed 2:1 AVB. The color-Doppler echocardiogram revealed preserved ejection fraction (EF 55%) and mild to moderate mitral steno-insufficiency. Doppler study indicated variability in the transvalvular aortic gradient. When evaluated on the beat following atrioventricular block, a pattern of severe aortic stenosis emerged (Vmax 4.15 m/s; Gmax/Gmed 68/41 mmHg), while the subsequent conducted beat exhibited a spectrum consistent with moderate aortic stenosis (Vmax 3.91 m/s; Gmax/Gmed 61/33 mmHg).
Considering the conduction disorder and the history of left bundle branch block, it was decided to perform cardiac resynchronization therapy using left bundle branch pacing with a dual-chamber pacemaker (Biotronik Edora 8 DR). After device implantation, the EKG revealed an electrically induced rhythm with left anterior hemiblock-like (LAHB) morphology. A follow-up echocardiogram showed a reduction in transvalvular aortic gradient (Vmax 3.52 m/s; Gmax/Gmed 49/25 mmHg), indicating improvement of the aortic stenosis.
Conclusion: In atrioventricular block, anomalous electrical conduction causes an increase in left ventricular end-systolic volume, resulting in a condition of hyperflow through the ventricular outflow tract. Left bundle branch pacing, by resynchronizing atrioventricular and biventricular activity, ensures adequate diastolic filling and reduces the aortic transvalvular gradient, thereby improving aortic stenosis and clinical conditions.
