Role of His-Bundle Pacing: Reliability and Potential to Avoid Ventricular Dyssynchrony

Increasing clinical evidence shows that conventional right ventricular pacing is detrimental to left ventricular function. Recent studies in canines [1] showed that right ventricular apical (RVA) pacing causes abnormal contraction patterns due to abnormal activation of the left ventricle during RVA pacing compared to normal sinus rhythm. Moreover, these studies gave evidence that sustained RVA pacing is associated with histological and structural changes that cause left ventricular function to deteriorate. In humans, short- and long-term studies [2, 3] have confirmed the adverse effects of RVA pacing. A theoretical pacing system that could preserve the normal Purkinje activation should be considered the ideal pacing approach, because the ventricular dyssynchrony would be prevented and the normal activation pattern maintained. However, the traditional pacing tools do not allow an easy approach to the His bundle, and therefore few clinical reports of this pacing mode exist in the literature. Deshmukh et al. [4, 5] reported the results of direct His-bundle pacing (DHBP) in patients with chronic heart failure and atrial fibrillation who were candidates for ablate-and-pace strategy because of a rapid and pharmacologically uncontrolled ventricular rate. According to Deshmukh et al., the criteria for verification of the DHBP were the following: (1) recording of His bundle potential with the permanent pacing lead; (2) pace-ventricular interval equal to His-ventricular interval ± 15 ms; (3) paced QRS morphology and duration equal to the intrinsic QRS in all 12 ECG leads. Twelve out of 18 patients in the first study and 39 out of 54 patients in the second study were successfully paced. In a long-term follow-up (42 months) the