Hyperdynamic circulation in portal hypertension: a comparative model of arterio-venous fistula

Complications of portal hypertension remain perplexing physiologic phenomen a in the understanding of shunt hemodynamics with multiple theories, Hyperd ynamic circulation was also found in sepsis, chronic anemia and arterio-ven ous (A-V) fistula which relate to an increase in nitric oxide. We hypothesi ze that portosystemic collaterals may mimic an A-V fistula in which the hig h-pressure portal blood connects with the lower pressure systemic venous ci rculation. Although these collaterals decompress the portal circulation, a number of secondary hemodynamic phenomena occur which increase portal blood flow and tend to counteract the portal hypotensive effect of the portosyst emic shunt. The consequent increases in cardiac output and portal blood flo w perfuse the compromised liver. As portal blood flow increases, collateral flow increases and is nearly totally shunted in the systemic circulation. This shunt may eventually introduce a vicious cycle of hyperdynamic circula tion into a compromised host. Ultimately, high-output cardiac failure occur s, leading to cirrhotic cardiomyopathy. (C) 2000 Harcourt Publishers Ltd.