Key result
Ectopic ventricular contractions without atrial systole delay the first heart sound vs. normal contractions.
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Phasic right atrial and ventricular pressures and heart sounds were simultaneously recorded from dogs with normal and ectopic ventricular contractions. Heart sounds and electrocardiograms were recorded from humans. The first heart sound is significantly delayed in the absence of atrial systole. The time between onset of the ventricular pressure rise due to ventricular contraction and the beginning of the first heart sound is minimal at normal A S -V S intervals. These findings support the view that normally the A-V valves are closed or nearly closed before ventricular systole. In ectopic ventricular beats the A-V valves are closed from an open position by ventricular contraction.
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Little et al. (1954) studied Normal and Ectopic Ventricular Contractions. Ectopic ventricular contractions vs. Normal ventricular contractions was evaluated on Timing of the first heart sound. Ectopic ventricular contractions without atrial systole significantly delay the first heart sound compared to normal contractions, indicating A-V valves are closed from an open position.
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