Cardiac stimulation during ritodrine hydrochloride tocolytic therapy.

The effect of ritodrine hydrochloride tocolytic therapy on left ventricular size and performance was studied during pregnancy by M-mode echocardiography. Ritodrine therapy increased heart rate, calculated stroke volume, ejection fraction, and cardiac output. Left ventricular end-diastolic dimension and systemic arterial pressure were unchanged. Left ventricular velocity of circumferential fiber shortening was markedly augmented. Ritodrine, as currently used for tocolytic therapy, has potent inotropic and chronotropic effects on the maternal heart. These effects suggest that ritodrine tocolytic therapy should be used with caution in patients with latent or manifest heart disease.