The contribution of atrial contraction to right heart function before and after right ventriculotomy. Experimental and clinical observations.
Effective atrial contraction was abolished by simultaneous atrial and ventricular (A-V) pacing in an acute canine preparation. At constant cardiac output, aortic pressure, and heart rate, only a small rise (1.4 mm. Hg) in mean right atrial pressure was observed before vertical right ventriculotomy, but a larger rise (9.5 mm Hg) occurred after ventriculotomy (p less than 0.01). Right heart failure with tricuspid regurgitation was induced after ventriculotomy by volume overload and A-V pacing. Restoration of atrial contraction (sequential A-V pacing) eliminated regurgitation and lowered average mean right atrial pressure from 22 to 4 mm. Hg (p less than 0.001). After right ventriculotomy, loss of atrial contraction at a constant right atrial pressure resulted in a 42 per cent reduction in cardiac output. In 8 patients who had had right ventriculotomies, abolition of effective atrial contraction by A-V pacing caused an average reduction in cardiac output of 22 per cent, whereas cardiac output fell only 5 per cent in 5 control patients (p less than 0.01).
D000818:Animals; D016275:Atrial Function; D001794:Blood Pressure; D002302:Cardiac Output; D002986:Clinical Trials as Topic; D004285:Dogs; D006321:Heart / Q000502:physiology*; D006333:Heart Failure / Q000503:physiopathology; D006339:Heart Rate; D006345:Heart Septal Defects, Ventricular / Q000601:surgery; D006352:Heart Ventricles / Q000601:surgery*; D006801:Humans; D008722:Methods; D009200:Myocardial Contraction; D010138:Pacemaker, Artificial