Extrasystoles with a fully compensated pause were experimentally induced in dogs for analysis of their effects on myocardial contractility and hemodynam-ics. The first postextrasystolic beat showed improved hemodynamic measurements exceeding the respective values of the pre-extrasystolic beat of the basic rhythm, making some compensation for extrasystole-induced depression of hemodynamics, which was progressively enhanced as the coupling time be-came shorter. The coupling time, the site of origin, and even the frequency of the extrasystole did not affect the rate of compensation, which averaged 60%. It was confirmed that hemodynamics in extrasystoles was mainly affected by two independent factors; the blood volume in the ventricle at the onset of ventricular contraction with the resultant STARLING'S effect, and ventricular contractility for individual beats, the latter of which depends upon myocardial contractility and the sequence of ventricular contraction. Postextrasystolic potentiation was regarded as the positive inotropic effect of the premature activation on the myocardium in postextrasystolic beats.
The intensity distribution of systolic murmur on chest surface was examined on 7 patients with ventricular septal defect. The frequencies of 79, 100, 200, 400 and 800cps were investigated. On the chest surface the equal intensity contour lines of the systolic murmur in ventricular septal defect were of approximately concentric circles centering around the point of maximum intensity of the murmur for each frequency.On the frequencies of 79, 100, 200 and 400cps, the relationships between the relative intensity in decibels of the murmur and the distance from the point of maximum intensity of the murmur were inversely proportional. Andthe apparent dampings per cm. of distance were from 0.4 to 1.8dB/cm. for 100cps, 0.4 to 2.0dB/cm. for 200cps and from 0.7 to 3.3 dB/cm. for 400cps. On the frequency of 800cps, the apparent damping become smaller according as the distance from the point of maximum intensity increased, in 4 of 7 cases. The apparent viscous damping obtained from the present data was generally smaller than the viscous damping of the sound during the transmission over chest surface.
