Characteristics and coexistence of two forms of ventricular echo phenomena.

During the scanning of paced basic ventricular cycle lengths (V1V1) with extrastimulus method (V2) two forms of ventricular echo phenomena (Ve) were recognized. The Ve resulting from A-V nodal re-entry (VeAVN) occurred in 12 of 45 patients, from re-entry in the His-Purkinje system (Ve-HPS) in 20 of 45 patients, and simultaneous dual re-entry (Ve-AVN and Ve-HPS) occurred in five of 45 patients. The Ve-AVN (1) appeared at longer V1V2 intervals, (2) was dependent on retrograde A-V nodal conduction delay, (3) had normal QRS complexes and H-V intervals, and (4) did not occur when V2 blocked in the A-V node.

Electrophysiologic effects of procainamide in subtherapeutic to therapeutic doses on human atrioventricular conduction system.

The effects of single intravenous infusions of 50 to 400 mg of procainamide on the functional properties of the atrioventricular (A-V) conduction system were studied in 36 patients and correlated with plasma concentrations. A 50 mg dose of procainamide resulted in a plasma concentration of less than 1.0 mug/ml and produced no electrophysiologic changes.

Time dependent changes in the functional properties of the atrioventricular conduction system in man.

Time dependent changes in the electrophysiological properties of the atrioventricular conducting system (AVCS) were determined at two or more cycle lengths (CL) in 22 patients using bundle of His (H) electrograms, incremental atrial pacing and atrial extrastimulus method. The atrioventricular (A-H interval) and intraventricular (H-V interval) conduction times and refractory periods (RP) of the atrium, the A-V node (AVN) and His-Purkinje system (HPS) were measured during the control period, and repeat measurements were made after a 30 minute interval in eight patients (group A), after a 60 minute interval in nine (group B) and after 30 and 60 minute intervals in five (group C). No statistically significant changes from control values were seen after 30 and 60 minute intervals in any group in sinus rate, A-V nodal conduction time and the onset of A-V nodal Wenckebach block.

A comparative analysis of antegrade and retrograde conduction patterns in man.

Patterns of antegrade and retrograde conduction and refractory periods were studied using His bundle electrogram recordings, incremental atrial and ventricular pacing and the extrastimulus technique. In 36/50 patients antegrade conduction was "better" than retrograde conduction (group I), as evidenced by a) onset of retrograde atrioventricular (A-V) nodal Wenckebach phenomenon at a slower rate compared to the antegrade counterpart (25 patients: group IA) or b) no ventriculo-atrial conduction at all ventricular paced rates (11 pts: group IB). The site of retrograde block in group IB patients was the A-V node.

Sinus node re-entrant tachycardia in man.

Sinus node re-entry (SNR) usually appears as a single beat. Tachycardias (SNRT) consistent with sustained SNR were seen in six patients and were initiated by premature stimulation of the high right atrium (six patients) and coronary sinus (four patients), and after continuous pacing from the high right atrium (four patients) or right ventricle (one patient) at rates of 130 to 200 per minute. During SNRT: (1) atrial beats exhibited a high-to-low atrial activation sequence, (2) the P-waves were similar in morphology to P-waves during sinus rhythm, and (3) re-entry in the A-V node or at the site of stimulation could be excluded.