Factors Influencing Stroke Volume: A Cinefluorographic Study of Angiocardiography

Abstract

Cinefluorographic films during angiocardiography provide a series of silhouettes of the individual chambers of the dog''s heart. Planimetric measurements of the projected area of the ventricular chambers on successive frames of the motion picture film (15 frames/sec.) indicate changes in ventricular size during successive cardiac cycles. From simultaneous recordings of intracardiac pressure and intrathoracic pressure, the effective filling pressure of the ventricles was detd. During many cardiac cycles, the diastolic size increased when the effective filling pressure was decreased. This has been attributed to a change in "distensibility" (diastolic size per unit of effective filling pressure) of the ventricular wall. Epinephrine, injected with the contrast media, produced marked changes in the pattern of both diastolic filling and "distensibility,"" particularly during the presystolic interval. Changes in stroke volume were apparently accomplished by increased early diastolic filling, increased presystolic filling during atrial contraction, and (3) increased systolic ejection.