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ZusammenfassungAm Modell eines isolierten, isovolumisch arbeitenden Hundeherzens wurde der Einfluß des Koronarperfusionsdruckes (CPP) auf die DruckVolumenbeziehung und die Kontraktilität des linken Ventrikels untersucht. In 30 Experimenten erfolgte für vier konstante CPP (60, 90, 120, 150 mm Hg) die Konstruktion diastolischer und systolischer Funktionskurven durch stufenweise Änderung des Volumens im linken Ventrikel (LW). Der Einfluß des CPP auf den kontraktilen Zustand des Herzens konnte mit Hilfe von 6 verschiedenen Kontraktilitätsindices (Vce, Vmax, dP/dtmax/IP, dP/dtmax/Pmax, t-(dP/dtmax) d(dP/dt)/dP) bei konstanten Perfusionsdrucken von 60, 90 und 120 mm Hg analysiert werden. Mit zunehmendem CPP kommt es bei unverän-dertem kontraktilem Zustand zu einer Verschiebung der Funktionskurven im Druck-Volumendiagramm nach links und oben, d.h. bei gleichem LW werden höhere Drucke erzeugt.The Influence of Coronary Perfusion Pressure on the Pressure-volume Relationship and Contractility of the Left Ventricle The influence of coronary perfusion pressure (CPP) on the pressure-volume relationship and the contractile state of the left ventricle has been studied using the model of an isolated, isovolumically beating heart. CPP and left ventricular volume (LVV) were adjustable. In 30 dog experiments diastolic and systolic left ventricular function curves were constructed for 4 constant levels of CPP (60, 90, 120, 150 mm Hg) by stepwise change of LW. In order to determine the influence of CPP on the contractile state of the myocardium 6 indices (Vce, Vmax, dP/dtmax/IP, dP/dtmax/Pmax, t-(dP/dtmax) d(dP/dt)/dP) were computed. With increasing CPP LV-performance increased, the function curves were. shifted to the left and into higher pressure-ranges, while contractility was not affected. It is conducted, that this effect of rising CPP is brought about by a concomitant increase of coronary blood flow, intracoronary blood volume and mural volume, which induces a stretch in initial fiber length and subsequently more forceful contraction without influencing the contractile state of the heart.Frühere Untersuchungen an isolierten isovolumisch arbeitenden Hundeherzen haben gezeigt, daß eine Änderung des koronaren Perfusionsdruckes (CPP) bei konstantem linksventrikulärem Volumen (LW) eine gleichgerichtete Änderung linksventrikulärer Funktionskurven hervorruft (7).

Contractile function, high-energy phosphate stores and tissular water, Na and K contents were investigated in order to study the specific effect of hypothermia in heart preservation. Isolated dog hearts were perfused with fresh oxygenated blood from a support animal. Experimental conditions were: (a) 30-min normothermia; (b) 3-hour normothermia; (c) 2-hour hypothermia (13°C) between normothermic periods. Ventricular function curves were drawn in isovolumic conditions during the normothermic periods. Enzymatic determinations of tissular PC, ATP, ADP, and AMP were performed on serial samples (20–60 mg) obtained by a drill biopsy technique. High-energy phosphate stores were not modified by hypothermia. After the hypothermic episode the mechanical function of the heart was impaired, and the water, Na and K contents were definitely modified.

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