1 Cardiac contractility in cirrhosis is normal at baseline but hyporesponsive to stimuli, a phenomenon known as 'cirrhotic cardiomyopathy'. The pathogenesis remains unclear. Endocannabinoids are vasoactive, but have not previously been examined in the cirrhotic heart. We therefore aimed to systematically clarify a possible role of endocannabinoids in the pathogenesis of cirrhotic cardiomyopathy. 2 Cirrhosis was induced in Sprague-Dawley rats by bile duct ligation; controls underwent a sham operation. At 4 weeks after operation, isolated left ventricular papillary muscle contractility was studied.3 Dose-response curve for a b-adrenergic agonist isoproterenol was constructed in the presence and absence of a CB-1 antagonist AM251 (1 mM). Cirrhotic muscles had a blunted response to isoproterenol, which was completely restored by AM251. 4 Dose-response curves to anandamide, and CB-1 and CB-2 protein and mRNA expression in Western blot and reverse transcriptase-polymerase chain reaction experiments were not significantly different between cirrhotic and sham muscles. 5 Force-frequency relationship studies were performed in cirrhotic and normal muscles. At higher frequencies, anandamide reuptake blockers (VDM11 and AM404) significantly enhanced muscle relaxation in cirrhotic muscles, but not in controls. This effect was completely blocked by AM251 and pertussis toxin, whereas tetrodotoxin partially reversed it. 6 Taken together, these results indicate a pathogenic role for increased local (neuronal) production of endocannabinoids, mediated by a G i -protein-dependent CB-1-responsive pathway in cirrhotic cardiomyopathy. The increased tachycardia-stress-induced release of endocannabinoids may help explain why contractility is normal at baseline but attenuated with stress.

Liver cirrhosis is associated with several cardiovascular disturbances. These disturbances include hyperdynamic systemic circulation, manifested by an increased cardiac output and decreased peripheral vascular resistance and arterial pressure. Despite the baseline increase in cardiac output, cardiac function in patients with cirrhosis is abnormal in several respects. Patients show attenuated systolic and diastolic contractile responses to stress stimuli, electrophysiological repolarization changes, including prolonged QT interval, and enlargement or hypertrophy of cardiac chambers. This constellation of cardiac abnormalities is termed cirrhotic cardiomyopathy. It has been suggested that cirrhotic cardiomyopathy has a role in the pathogenesis of cardiac dysfunction and even overt heart failure after transjugular intrahepatic portosystemic shunt placement, major surgery and liver transplantation. Cardiac dysfunction contributes to morbidity and mortality after liver transplantation, even in many patients who have no prior history of cardiac disease. Depressed cardiac contractility contributes to the pathogenesis of hepatorenal syndrome, especially in patients with spontaneous bacterial peritonitis. Pathogenic mechanisms underlying cirrhotic cardiomyopathy include cardiomyocyte-membrane biophysical changes, attenuation of the stimulatory beta-adrenergic system and overactivity of negative inotropic systems mediated via cyclic GMP. The clinical features, general diagnostic criteria, pathogenesis and treatment of cirrhotic cardiomyopathy are discussed in this review.

Cardiovascular abnormalities accompany both portal hypertension and cirrhosis. These consist of hyperdynamic circulation, defined as reduced mean arterial pressure and systemic vascular resistance, and increased cardiac output. Despite the baseline increased cardiac output, ventricular inotropic and chronotropic responses to stimuli are blunted, a condition known as cirrhotic cardiomyopathy. Both conditions may play an initiating or aggravating pathogenic role in many of the complications of liver failure or portal hypertension including ascites, variceal bleeding, hepatorenal syndrome and increased postoperative mortality after major surgery or liver transplantation. This review briefly examines the major mechanisms that may underlie these cardiovascular abnormalities, concentrating on nitric oxide, endogenous cannabinoids, central neural activation and adrenergic receptor changes. Future work should address the complex interrelationships between these systems.

Background and purpose: Hyperdynamic circulation and mesenteric hyperaemia are found in cirrhosis. To delineate the role of endocannabinoids in these changes, we examined the cardiovascular effects of anandamide, AM251 (CB 1 antagonist), AM630 (CB 2 antagonist) and capsazepine (VR1 antagonist), in a rat model of cirrhosis. Experimental approach: Cirrhosis was induced by bile duct ligation. Controls underwent sham operation. Four weeks later, diameters of mesenteric arteriole and venule (intravital microscopy), arterial pressure, cardiac output, systemic vascular resistance and superior mesenteric artery (SMA) flow were measured after anandamide, AM251 (with or without anandamide), AM630 and capsazepine administration. CB 1 , CB 2 and VR1 receptor expression in SMA was assessed by western blot and RT-PCR. Key results: Anandamide increased mesenteric vessel diameter and flow, and cardiac output in cirrhotic rats, but did not affect controls. Anandamide induced a triphasic arterial pressure response in controls, but this pattern differed markedly in cirrhotic rats. Pre-administration of AM251 blocked the effects of anandamide. AM251 (without anandamide) increased arterial pressure and systemic vascular resistance, constricted mesenteric arterioles, decreased SMA flow and changed cardiac output in a time-dependent fashion in cirrhotic rats. Capsazepine decreased cardiac output and mesenteric arteriolar diameter and flow, and increased systemic vascular resistance in cirrhotic rats, but lacked effect in controls. Expression of CB 1 and VR1 receptor proteins were increased in cirrhotic rats. AM630 did not affect any cardiovascular parameter in either group. Conclusions and implications: These data suggest that endocannabinoids contribute to hyperdynamic circulation and mesenteric hyperaemia in cirrhosis, via CB 1 -and VR1-mediated mechanisms.

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