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 nervous system. This suggests multiple sites of actions for Ang II throughout the cardiovascular system. Cardiac effects of Ang II are not completely understood, though its prominent vasoconstrictor actions are well described. This study was designed to assess left ventricular function during administration of Ang II using relatively load-independent methods in a whole-animal model.


METHODS
Ang II was infused in incremental doses (0-200 microg x h(-1)) in anaesthetised instrumented pigs (n=10). Cardiac systolic and diastolic function were evaluated by analysis of the left ventricular pressure-volume relationship.


RESULTS
Heart rate (HR), mean arterial pressure (MAP) and systemic vascular resistance (SVR) increased dose-dependently with Ang II, while cardiac output (CO) remained unchanged. Systolic function indices, end-systolic elastance (Ees) and preload recruitable stroke work (PRSW), demonstrated dose-dependent increases. The diastolic function parameter tau (tau) did not change with increasing Ang II dose.


CONCLUSIONS
Ang II infusion caused increases in contractility indices in anaesthetised pigs in the doses used in this study. The mechanisms for these systolic function effects may be a direct myocardial effect or modulated through changes in autonomic nervous system activity.
Broomé
M
M
Dept of Surgical and Perioperative Science, Anaesthesiology and Intensive Care, Umeå University Hospital, Umeå, Sweden. michaael.broome.us@vll.se
Haney
M
M
Häggmark
S
S
Johansson
G
G
Aneman
A
A
Biber
B
B
D000804:Angiotensin II / Q000494:pharmacology*; D000818:Animals; D001794:Blood Pressure / Q000187:drug effects; D002316:Cardiotonic Agents / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D005260:Female; D006339:Heart Rate / Q000187:drug effects; D006439:Hemodynamics / Q000187:drug effects; D006728:Hormones / Q000097:blood; D007262:Infusions, Intravenous; D009200:Myocardial Contraction / Q000187:drug effects*; D013552:Swine; D014662:Vasoconstrictor Agents / Q000494:pharmacology*
D002316:Cardiotonic Agents; D006728:Hormones; D014662:Vasoconstrictor Agents; D000804:Angiotensin II