The hemodynamic effects of AT-112, an analog of ketanserin, in portal hypertensive rats

5-Hydroxytryptamine receptors in the human cardiovascular system

The human cardiovascular system is exposed to plasma 5-hydroxytryptamine (5-HT, serotonin), usually released from platelets. 5-HT can produce harmful acute and chronic effects. The acute cardiac effects of 5-HT consist of tachycardia (preceded on occasion by a brief reflex bradycardia), increased atrial contractility and production of atrial arrhythmias. Acute inotropic, lusitropic and arrhythmic effects of 5-HT on human ventricle become conspicuous after inhibition of phosphodiesterase (PDE) activity. Human cardiostimulation is mediated through 5-HT4 receptors. Atrial and ventricular PDE3 activity exerts a protective role against potentially harmful cardiostimulation. Chronic exposure to high levels of 5-HT (from metastatic carcinoid tumours), the anorectic drug fenfluramine and its metabolites, as well as the ecstasy drug 3,4-methylenedioxymethamphetamine (MDMA) and its metabolite 3,4-methylenedioxyamphetamine (MDA) are associated with proliferative disease and thickening of cardiac valves, mediated through 5-HT2B receptors. 5-HT2B receptors have an obligatory physiological role in murine cardiac embryology but whether this happens in humans requires research. Congenital heart block (CHB) is, on occasion, associated with autoantibodies against 5-HT4 receptors. Acute vascular constriction by 5-HT is usually shared by 5-HT1B and 5-HT2A receptors, except in intracranial arteries which constrict only through 5-HT1B receptors. Both 5-HT1B and 5-HT2A receptors can mediate coronary artery spasm but only 5-HT1B receptors appear involved in coronary spasm of patients treated with triptans or with Prinzmetal angina. 5-HT2A receptors constrict the portal venous system including oesophageal collaterals in cirrhosis. Chronic exposure to 5-HT can contribute to pulmonary hypertension through activation of constrictor 5-HT1B receptors and proliferative 5-HT2B receptors, and possibly through direct intracellular effects.

Drug treatment for bleeding oesophageal varices

At the time of diagnosis of cirrhosis, varices are present in about 60% of decompensated and 30% of compensated patients. The risk factors for the first episode of variceal bleeding in cirrhotic patients are the severity of liver dysfunction, a large size of the varices and the presence of endoscopic red colour signs, but only a third of patients who suffer variceal haemorrhage demonstrate the above risk factors. The only treatment that does not require sophisticated equipment or the skills of a specialist, and is immediately available, is vasoactive drug therapy. Hence, drug therapy should be considered to be the initial treatment of choice and can be administered while the patient is transferred to hospital, as has been done in one recent study. Moreover, drug therapy is no longer considered to be only a 'stop-gap' therapy until definitive endoscopic therapy is performed. Several recent trials have reported an efficacy similar to that of emergency sclerotherapy in the control of variceal bleeding. Furthermore, recent evidence suggests that those patients with high variceal or portal pressure are likely to continue to bleed or re-bleed early, implying that prolonged therapy lowering the portal pressure over several days may be the optimal treatment. Pharmacological treatment with beta-blockers is safe, effective and the standard long-term treatment for the prevention of recurrence of variceal bleeding. The combination of beta-blockers with isosorbide-5-mononitrate needs further testing in randomized controlled trials. The use of haemodynamic targets for the reduction of the HVPG response needs further study, and surrogate markers of the pressure response need evaluation. Ligation has recently been compared with beta-blockers for primary prophylaxis, but there is as yet no good evidence to recommend banding for primary prophylaxis if beta-blockers can be given.