Effects of an interpolated premature ventricular contraction on the AV conduction of the subsequent premature atrial depolarization. An apparent facilitation.

Nodal conduction is usually studied by tracing the H1 H2 on function of A1 A2 curves. If one interpolates a PVC before A1, there is a decrease in H1 H2. This might be explained by an A1 H1 interval lengthening (delta A1 H1). This study was done on 14 consecutive patients in whom a PVC can be interpolated (blocked at the A-V junction). In the majority of these patients, there is a downward and a right hand shift in the curve after an interpolated PVC. On other hand, the curves representing the sum H1 H2 + delta A1 H1 on function of A1 A2 were shifted upward and to the right in 12 of the 14 patients. This indicates inhibition which manifests itself not only by an ERP increase but also by an A2 H2 increase.