Effects of epoprostenol and sildenafil on right ventricular function in hypoxic volunteers: a tissue Doppler imaging study
This study was carried out to investigate the possible contribution of endogenous prostaglandin (PG) production to failure of contractile recovery following reperfusion of hypoperfused isolated rat hearts. A 90% reduction in coronary flow rate for 60 min resulted in a time-dependent depression of contractile force and an elevation in resting tension. Reperfusion produced a slight (approximately 11%) recovery of contractile force, whereas resting tension remained elevated. Reperfusion was a potent stimulus for PG (as assessed by 6 keto-PGF1 alpha) release and resulted in levels that were significantly higher than those observed prior to ischemia. When PG synthesis was inhibited by the nonsteroidal anti-inflammatory drugs ibuprofen, indomethacin, or acetylsalicylic acid (ASA), recovery of ventricular contractility on reperfusion was significantly higher than that seen in the absence of drugs. Ibuprofen was the most effective, producing an average recovery of 70% (P less than 0.05 from control). Indomethacin and ASA produced approximately a 40% (P less than 0.05) and 35% (P less than 0.05) recovery of contractile force, respectively. The improved recovery in contractility was significantly depressed by the addition of low concentrations of prostacyclin (PGI2) and PGF2 alpha, whereas PGE2 and 6 keto-PGF1 alpha, the hydrolysis product of PGI2, were ineffective. The effects on resting tension were inconsistent. PG release during reperfusion was unrelated either to the length of the initial period of reduced coronary flow or the degree of contractile recovery; it was attenuated either by a reduction in or by an elevation of Ca concentration. These results indicate that endogenous PGs mediate, at least in part, reperfusion-associated failure of ventricular function.