Abstract
Abstract
The Langendorff perfused heart is studied in a closed system with (i) automatic regulations to maintain constancy of the perfusion column (Krebs-Henseleit + 0.5% albumin or 25–30% washed erythrocyte suspension), (ii) continuous recording of rate, coronary flow, and supravalvular aortic pressure. A microcomputer with software interface is used for storage treatment and on-line analysis of the recorded variables. In 38 preparations perfused with Krebs-Henseleit, minimal diastolic (61.2 ± 2.8 mm Hg) is significantly below and peak systolic (98.7 ± 3.6 mm Hg) significantly above perfusion pressure (80 mm Hg). Pressure difference between minimal diastolic and peak systolic (ΔP) is 37.5 ± 1.8 mm Hg. Increases in perfusion pressure will be associated with increases of coronary flow and ΔP, which is also increased by isoprenaline administration. Oxygen consumption decreased by 76% when perfusion pressure was lowered from 80 to 60 mm Hg in hearts perfused with a 30% erythrocyte suspension. All of these experimental results were interpreted as indicating that ΔP measured in this system resulted from an ejected volume (x acceleration) from the heart. The ejected volume corresponds to a valvular leak caused by the rigid nature of the system which is devoid of aortic compliance. ΔP may be considered an index of left ventricular performance, an indication that the Langendorff preparation studied under the present conditions is a working heart. A 100-μ1 volume constant infusion syringe for time administration of cardioactive drugs may be inserted at the base of the perfusion column to obtain dose-response effects.
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