Study of the acute effect of AR-L 115 BS, a new positive-inotropic agent in patients with exercise-induced heart failure.

Invasive cardiac measurements were performed at rest and during exercise after i.v. infection of 0.7 mg/kg 2-[(2-methoxy-4-methylsulfinyl)phenyl]-1H-imidazo[4,5-b]pyridine (AR-L 115 BS) in 10 patients with heart failure in NYHA class II and III of various origins. At rest AR-L 115 BS increased the cardiac index by 0.74 l/min/m2 (p less than 0.01) and the heart rate by 10 beats/min (p less than 0.01). Mean arterial pressure and pressures in the pulmonary artery and in the pulmonary capillary bed were not changed significantly. Stroke work index remained unchanged. At the highest comparable workload AR-L 115 BS reduced the pulmonary capillary wedge pressure by 7 mm Hg (p less than 0.001) and the mean pulmonary arterial pressure by 8 mm Hg (p less than 0.001). The other parameters measured did not change significantly. In most of the patients there was a reduction in the pulmonary capillary pressure in parallel with a slight increase in the stroke work index, indicating an improvement in left ventricular pump function. Four patients reported bright vision immediately after injection which lasted for several hours in 1 patient and for about 5 min in the others. One patient developed muscle tremor which lasted for several hours. The results suggest that AR-L 115 BS exerts a vasodilating action on the capacitance vessels and a positive-inotropic effect on the heart.