Acute effects of angiotensin II on myocardial performance

Background: Specific angiotensin II (Ang II) receptors exist in many organs including peripheral blood vessels, cardiac myocytes and the central nervo us system. This suggests multiple sites of actions for Ang II throughout th e cardiovascular system. Cardiac effects of Ang II are not completely under stood, though its prominent vasoconstrictor actions are well described. Thi s study was designed to assess left ventricular function during administrat ion of Ang II using relatively load-independent methods in a whole-animal m odel. Methods: Ang H was infused in incremental doses (0-200 mug . h(-1)) in anae sthetised instrumented pigs (n=10). Cardiac systolic and diastolic function were evaluated by analysis of the left ventricular pressure-volume relatio nship. Results: Heart rate (HR), mean arterial pressure (MAP) and systemic vascula r resistance (SVR) increased dose-dependently with Ang II, while cardiac ou tput (CO) remained unchanged. Systolic function indices, end-systolic elast ance (E-es) and pre-load recruitable stroke work (PRSW), demonstrated dose- dependent increases. The diastolic function parameter tau (T) did not chang e with increasing Ang H dose. Conclusion: Ang H infusion caused increases in contractility indices in ana esthetised pigs in the doses used in this study. The mechanisms for these s ystolic function effects may be a direct myocardial effect or modulated thr ough changes in autonomic nervous system activity.