Relationship between the most proximal His bundle and the morphology of intracavitary pressure curves

A precise localization of the most proximal His bundle (HB) is useful both for diagnostic and for therapeutic purposes, allowing the modification of atrioventricular (AV) nodal conduction. For selective diagnosis a bipolar lead is utilized; for therapy, a unipolar lead. The aim of the present study was to determine the relationship between the most proximal HB and the morphology of intracavitary pressure curves. In 15 patients (aged 64 +/- 10 years), both bipolar and unipolar H-V intervals were continuously recorded while gradually withdrawing the catheter, which detected the pressure at its tip, from the right ventricle to the atrium. The longest bipolar H-V was 55.5 +/- 13 ms and the shortest 44.5 +/- 11 ms (P less than 0.001); the longest unipolar H-V was 56.5 +/- 14 ms and the shortest 46.2 +/- 11 ms (P less than 0.001). During unipolar recording, H deflection was present in all patients at the same time as ventricular, transvalvular and atrial pressure curves; during bipolar recording, the H electrogram was not present in only one patient concomitantly with the atrial curve. During bipolar recording, the atrial H-V interval was greater than transvalvular H-V in nine patients (mean differences: 6 +/- 2 ms) and they were equal in five; with unipolar recording the atrial H-V interval was greater than transvalvular H-V in 13 patients (mean difference: 8 +/- 6 ms) and they were equal in two. In all patients, the H wave amplitude diminished from the transvalvular area to the atrial one.(ABSTRACT TRUNCATED AT 250 WORDS)