Circulatory dynamics and the effects of respiration during ventricular asystole in dogs with complete heart block.

• The need for a clearer understanding of the physiological changes accompanying acute ventricular asystole in complete heart block (Stokes-Adams syndrome) is especially important in view of the significant advances made in the therapy of this disorder.~ In addition, simulating this condition in the laboratory provides a unique approach to the study of eardiorespiratory dynamics and their interrelationships. The difficulty in obtaining a suitable preparation and the acute nature of ventricular asystole probably account for the scarcity of reports in this area. Erlanger et al. succeeded in producing chronic complete heart block in dogs in 1910. I n 1955, Starzl et al.' ° described a surgical approach for severing the atrioventricular (A-V) bundle and studied the cardiovascular changes occurring during acute and chronic heart block. The period of acute ventricular asystole was not studied. Dowling et al." observed the pressure changes in the right ventricle, pulmonary artery, and femoral artery during relatively short periods of asystole in two human subjects. The present study was undertaken to investigate the following during prolonged ventricular asystole: (1) physiology of independent atrial activity; (2) pressure-flow