Portal hypertension induces neuroendocrine activation and a hyperkinetic circulation state. This study investigated the consequences of portal hypertension on heart structure and function. Intrahepatic portal hypertension was induced in male Sprague-Dawley rats by chronic bile duct ligation (CBDL). Six weeks later, CBDL rats showed higher plasma angiotensin-II and endothelin-1 (P < .01), 56% reduction in peripheral resistance and 73% reduction in pulmonary resistance (P < .01), 87% increase in cardiac index and 30% increase in heart weight (P < .01), and increased myocardial nitric oxide (NO) synthesis. In CBDL rats, macroscopic analysis demonstrated a 30% (P < .01) increase in cross-sectional area of the left ventricular (LV) wall without changes in the LV cavity or in the right ventricle (RV). Histomorphometric analysis revealed increased cell width (12%, P < .01) of cardiomyocytes from the LV of CBDL rats, but no differences in myocardial collagen content. Myocytes isolated from the LV were wider (12%) and longer (8%) than right ventricular myocytes (P < .01) in CBDL rats but not in controls. CBDL rats showed an increased expression of ANF and CK-B genes (P < .01). Isolated perfused CBDL hearts showed pressure/end-diastolic pressure curves and response to isoproterenol identical to sham hearts, although generated wall tension was reduced because of the increased wall thickness. Coronary resistance was markedly reduced. This reduction was abolished by inhibition of NO synthesis with N-nitro-L-arginine. Expression of eNOS was increased in CBDL hearts. In conclusion, portal hypertension associated to biliary cirrhosis induces marked LV hypertrophy and increased myocardial NO synthesis without detectable fibrosis or functional impairment. This observation could be relevant to patients with cirrhosis. (HEPATOLOGY 2003;38:589-598.) H yperdynamic circulation is a common feature in human and experimental portal hypertension, with or without cirrhosis. This is also called hyperdynamic circulatory syndrome and is the consequence of splanchnic and systemic vasodilatation, manifested by increased heart rate, cardiac output, and regional blood flow with decreased mean arterial pressure and systemic vascular resistance (SVR). 1 The mechanism of systemic and splanchnic vasodilatation is multifactorial. Many studies have suggested a prominent role for increased biosynthesis of nitric oxide (NO), 2 which is due to increased endothelial nitric oxide synthase (eNOS) activity. 3,4 It has been shown that NO inhibition attenuates the hyperdynamic circulation observed in portal hypertensive rats. 5,6 Other studies have shown an increased splanchnic production of carbon monoxide in portal hypertension 7 as well as an increased release of splanchnic vasodilatory peptides, such as glucagon. 8,9 Vasoconstrictor systems are also up-regulated, probably as a counter-regulatory response to the hyperdynamic state. 10 Sympathetic nervous and renin-angiotensin aldosterone systems are enhanced, and the plasma levels of vasopressin and endot...