The Effect of Atrial Systole on Right Ventricular Stroke Output in Man

摘要

The effect of correct synchrony between atrial and ventricular contraction in achieving optimal stroke output by the heart is not clearly defined in man because of the lack of an accurate method for measuring beat-by-beat changes in stroke volume. We have therefore made such measurements using the N2O-plethysmograph method for recording instantaneous pulmonary capillary blood flow. Integration of the N2O pulsations permits beat-by-beat measurements of right ventricular stroke volume. Two model groups of subjects were studied whose ventricular rates were constant but in whom the P-R interval varied widely; group A, healthy subjects with congenital complete atrioventricular dissociation; and group B, patients with complete atrioventricular dissociation due to myocardial disease. In group A, 40% augmentation in stroke output by the heart took place when the P-R interval was optimally timed late in ventricular diastole. In group B, atrioventricular synergy produced only 13% augmentation. Changes in pulmonary venous compliance due to elevation of the left atrial pressure in the group B subjects with myocardial disease led to major alterations in lung capillary blood flow as a consequence of the changes in pulmonary venous outflow impedance so imposed. (Author)