Course of pressure in isovolumetric relaxation of the left ventricle in man during rest and under acute pressure load

• Published in: Zeitschrift für Kardiologie Vol. 64; no. 5; p. 444
• Main Authors: Eschmann, P, Krayenbühl, H P, Rutishauser, W
• Format: Journal Article
• Language: German
• Published: Germany 01.05.1975
• Subjects: Atropine; Cardiac Output; Heart - physiology; Heart Ventricles; Humans; Manometry; Propranolol; Relaxation; Rest
• ISSN: 0300-5860

Isovolumic relaxation of the left ventricle was investigated in man at rest and during pressure loading with methoxamine after blocking the autonomous nervous system with propranolol and atropine. Pressure course at rest and under methoxamine showed two distinct phases: first pressure fell steeply, then a gradual decrease of pressure course occurred without abrupt changes in slope. During pressure loading P and dP/dt increased markedly while the quotient (dP/dt)/P as a measure of contractile element velocity decreased. It was demonstrated that (dP/dt)/P during the second phase of relaxation did not show a plateau (no exponential pressure decay) but a "shoulder". If isovolumic ventricular pressure decay corresponds to isometric relaxation it can be stated that lengthening velocity of contractile elements increases gradually during the second phase of relaxation. The conclusions derived from isolated papillary muscle experiments would therefore not correspond to intact ventricle in man.