Arrival of excitation at high right atrium, low right atrium, His bundle, right ventricular outflow tract (RVOT) and posterosuperior wall of the left ventricle (PSLV) was recorded during intermittent premature right ventricular apical stimulation at progressively shorter coupling intervals in 3 patients. Whereas driven impulses showed a superior and leftward axis orientation with a predominantly negative deflection in lead V1, premature impulses delivered soon after the end of the effective refractory periods produced, in Cases 1 and 2 a predominantly upright deflection in V1. This occurred because the RVOT and the right ventricular wall were activated before the PSLV. In Cases 1 and 3, there was a part of the cycle during which premature impulses reached the recording ventricular electrodes with less delay than driven impulses. The duration of the corresponding ventricular complexes was shorter than that of driven impulses. These changes were not attributed to intraventricular supernormal conduction velocity, but to inhomogeneity of excitability related changes in the conduction pathways occurring during the end of the period of incomplete recovery. In all 3 cases the shortest retrograde H1 H2 interval was significantly longer than the shortest RVOT1 RVOT2 and PSLV1 PSLV2 intervals. It is concluded that the physiological properties of the Purkinje myocardial junction (peripheral 'gate') determined the retrograde (H1 H2) conduction intervals and that those of the tissues distal to the 'gate' were responsible for both 'subnormal' and 'supernormal' intraventricular conduction patterns.
|Title of host publication||EUR.J.CARDIOL.|
|Number of pages||8|
|State||Published - Dec 1 1973|
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