Three-dimensional analysis of regional myocardial function in response to nitroglycerin in patients with coronary...

Biplane cineventriculography was performed at rest and after sublingual nitroglycerin in 13 patients with coronary artery disease. In six patients (responders), there was a significant increase in ejection fraction [40 +/- 5 to 52 +/- 4% (p less than 0.001)], while in the other seven (nonresponders), there was no alteration in ejection fraction. To evaluate the extent of regional myocardial response to nitroglycerin, the contractile pattern of the regional myocardium over the entire ventricular surface was analyzed using a computer-generated three-dimensional model. The spatial coordinates that define the elliptic ventricular surface on a given horizontal plane cross section of the chamber were determined by four counter values in the two orthogonal silhouettes. Then, 32 points at equal angles around the center of gravity of the end-diastolic cavity were generated to form the border image. Repetition of this process for 16 successive cross sections allowed for reconstruction of the ventricular surface by the sequence of 32 X 16 (512) points. The regional wall motion was expressed as the percent change of the radial length, drawn from the center of gravity to each surface point. There was significant heterogeneity in regional response to nitroglycerin. In the responders, the normally contracting area was significantly increased (from 16.5 +/- 16.0 to 36.2 +/- 14.9% of the total surface area, p less than 0.001), largely mediated by the greater improvement in segmental shortening of each graded contractile pattern relative to its deterioration. In the nonresponders, a lessening of the severe dysfunction of the given area was associated with significant deterioration of segmental shortening of the other normally contracting area (49.1 +/- 19.7% of the area with a contractile pattern of grade 5 had deteriorated, p less than 0.05). Thus, the ratio of the area with respective graded segmental shortening was virtually unchanged. These differences in response of the ischemic ventricle to nitroglycerin appeared to be related to the development of adequate coronary collateral vessels as well as to an interaction of changes in preload and afterload.