A Study of Arrival of Excitation at Selected Ventricular Sites during Human Bundle Branch Block Using Close Bipolar Catheter Electrodes

Abstract

<h2> </h2> One mm apart bipolar catheter electrodes were used to study the arrival of excitation at the right ventricular apex (RVA), right ventricular outflow tract (RVOT) and posterosuperior wall of the left ventricle (PSLV) during high right atrial, as well as during ventricular, pacing. In absence of bundle branch block the RVA appeared to have been activated by the impulse descending through the right branch (V-RVA intervals ranging between 15 and 30 msec). The short interval elapsing between inscription of RVA and RVOT electrograms (range 10 to 20 msec) suggested that propagation from apex to outflow tract did not occur in a linear fashion, as when these sites were stimulated directly (60 to 80 msec). Arrival of excitation at the explored right ventricular endocardial sites was delayed when "complete" right bundle branch block was present (V-RVA intervals between 50 and 60 msec). The corresponding endocardial electrograms were inscribed significantly before depolarization of the free right ventricular wall was completed. During "complete" left bundle branch block activation of the posterosuperior wall of the left ventricle was significantly prolonged (120 to 130 msec as compared with the normal range of 50 to 60 msec). The delay in activation of the blocked ventricle (50 to 70 msec) after homolateral "complete" bundle branch block was twice as long as in canine hearts.