Different response of left ventricular dimensions to nitroglycerin in patients with artificial pacemaker. A possible significance of reflex tachycardia for the reduction of LV cavity after nitroglycerin.

The effects of nitroglycerin (NTG) on cardiac function can be evaluated by echocardiography. In this paper, we discuss the effects of NTG on cardiac function in two groups of subjects, one with artificial pacemakers implanted with a fixed heart rate, and the other examined as the control group. Left ventricular dimension was obtained in the standard manner using the electronic sector scanning system of Toshiba SSH-11A. Left ventricular end-diastolic and end-systolic dimensions (Dd and Ds) were obtained in each case and the ejection fraction was calculated. After the sublingual administration of NTG (0.6 mg), the blood pressure decreased in both groups. The ventricular rate was fixed in the pacemaker group but increased significantly in the control group. Dd and Ds were found to decrease only in the control group. The ejection fraction showed an increase in the majority of the control group but remained unchanged in the pacemaker group. Heart rate change therefore may play a role in dimensional change and pumping function of heart after NTG.