Left ventricular approach for recording His bundle potential in man

The electrical potentials of the His bundle (HB) were recorded from the left ventricular endocardial surface in 28 patients ranging from 16 to 63 yr of age. In 14 of the patients, the left bundle branch (LB) potentials were also obtained. Placement of a bipolar electrode catheter tip toward the interventricular septum, right at and also 1 to 2 cm below the aortic valve, resulted in stable recordings of both potentials in successive cardiac cycles even at performing atrial or HB pacing from the right heart. The following intervals were measured in milliseconds (msec): P A, A H, H, H V, LB, and LB V. The average values in 12 patients (average age 26 ± 7 yr and average heart rate 90 ± 16 beats per min) with normal AV conduction were as follows: P A 28 ± 7, A H 76 ± 16, H 19 ± 3 and H V 45 ± 6 msec. The average values for LB and LB V in 10 of these 12 patients were 15 ± 3 and 25 ± 3 msec respectively. Validation of the His bundle electrogram (HBE) from the left ventricular endocardial surface was based on simultaneous recordings of the intracardiac electrograms from left and right sides of the heart in 18 patients. The individual average values for the intervals obtained from both sides of the heart in these patients were statistically not different, except that the H potential was slightly longer in duration from the left heart (P = 0.05). Among these, 16 showed simultaneous onset of the H potentials, and the LB V and RB V conduction times from comparable points were almost the same. Indications for the left sided electrophysiologic studies include the following situations: inability to record H from the right side of the heart; giant right atrium; and possibly during atrial fibrillation.