Inotropic Effects of Prostacyclins on the Right Ventricle Are Abolished in Isolated Rat Hearts With Right-Ventricular Hypertrophy and Failure.

BACKGROUND

Prostacyclin mimetics are vasodilatory agents used in the treatment of pulmonary arterial hypertension. The direct effects of prostanoids on right-ventricular (RV) function are unknown. We aimed to investigate the direct effects of prostacyclin mimetics on RV function in hearts with and without RV hypertrophy and failure.

METHODS

Wistar rats were subjected to pulmonary trunk banding to induce compensated RV hypertrophy (n = 32) or manifest RV failure (n = 32). Rats without banding served as healthy controls (n = 30). The hearts were excised and perfused in a Langendorff system and subjected to iloprost, treprostinil, epoprostenol, or MRE-269 in increasing concentrations. The effect on RV function was evaluated using a balloon-tipped catheter inserted into the right ventricle.

RESULTS

In control hearts, iloprost, treprostinil, and MRE-269 improved RV function. The effect was, however, absent in hearts with RV hypertrophy and failure. Treprostinil and MRE-269 even impaired RV function in hearts with manifest RV failure.

CONCLUSIONS

Iloprost, treprostinil, and MRE-269 improved RV function in the healthy rat heart. RV hypertrophy abolished the positive inotropic effect, and in the failing right ventricle, MRE-269 and treprostinil impaired RV function. This may be related to changes in prostanoid receptor expression and reduced coronary flow reserve in the hypertrophic and failing right ventricle.