Relation of the Difference in Pressure Across the Mitral Valve to the Amplitude of the First Heart Sound in Dogs With Atrioventricular Block

¹ From the Section of Physiology, Mayo Clinic and Mayo Foundation, Rochester, Minnesota

Measurements of the left atrial and ventricular pressure pulse in dogs with complete atrioventricular (AV) heart block revealed positive and negative differences in pressure across the mitral valve which were associated with high and low amplitudes of the first heart sound, respectively. Congestive heart failure, infusions and bleeding altered the duration of the negative difference in pressure and the amplitude of the first heart sound during atrial diastole. High and low amplitudes of the first heart sound are coincident with the opened and closed AV valves, respectively. The position of the valve leaflets at the onset of ventricular excitation seems to affect the rise of the ventricular pressure.