Detection of cardiac events by continuous electrocardiogram monitoring during ritodrine infusion.

Cardiac events in 30 patients in preterm labor on ritodrine therapy were examined continuously on a Holter monitor. Unsuspected events, such as persistent severe tachycardia, premature ventricular contractions, and supraventricular premature contractions, were observed. These events did not occur more frequently in patients with cardiac symptoms. None of these changes were observed by standard monitoring methods. Continued beta-mimetic stimulation in the presence of these events may lead to the serious cardiopulmonary complications that have been reported during ritodrine infusion.