Modification of pacing-induced alterations in diastolic properties of the regional myocardium by nifedipine in patients with coronary artery disease.

The effects of nifedipine on regional dysfunction during pacing-induced ischemia were studied in eight patients with coronary artery disease. Single-plane left ventriculograms were obtained using a high-fidelity micromanometer-tipped catheter in the control and post-pacing periods both before and after pretreatment with nifedipine. All patients developed typical anginal pain during pacing tachycardia before but not after pretreatment with nifedipine. After pacing, left ventricular end-diastolic pressure (EDP) increased from 10 +/- 5 (SD) mmHg to 23 +/- 9 mmHg (P less than 0.01) with enlargement of the end-diastolic volume (EDV). The ejection fraction (EF) was reduced from 66 +/- 10% to 54 +/- 13% (P less than 0.05). With nifedipine, a post-pacing increase in EDP was markedly attenuated together with a 17% reduction in left ventricular systolic pressure (P less than 0.05). The regional myocardial function was expressed by a radial coordinate system with its origin at the center of gravity of the end-diastolic contour. Two representative radial grids for normal and ischemic segments were selected. In the normal segment, the end-diastolic length (EDL) was augmented by 14% (from 26.1 +/- 5.2 mm to 29.7 +/- 6.1 mm, P less than 0.01) associated with a 23% increase in stroke excursion (P less than 0.05) with pacing stress. In the ischemic segments, EDL remained unchanged in the post-pacing beat but stroke excursion was significantly reduced (from 11.4 +/- 5.2 mm to 4.3 +/- 1.8 mm, P less than 0.01).(ABSTRACT TRUNCATED AT 250 WORDS)