Coronary artery stenosis provokes non-uniformity of two-dimensional deformation in the anterior wall of the feline left ventricle

Abstract

The effect of coronary stenosis on the uniformity of local left ventricular contraction was studied in 11 open-chest cats. Coronary artery stenosis was established by controlled constriction of a shunt line from the right subclavian artery to the left main coronary artery. Two pairs of ultrasonic crystals were placed in the midwall of the anterior left ventricular wall; one pair, circumferential (Circ), aligned with midwall and subepicardial fibres; the other, longitudinal (Long), aligned with subendocardial fibres. Three steps of coronary perfusion pressure (poststenotic) were studied; open shunt line (140 +/- 4 mmHg), light stenosis (94 +/- 2 mmHg), and severe stenosis (70 +/- 3 mmHg). Subendocardial tissue blood flow showed the most pronounced reduction (from 1.87 +/- 0.11 to 1.43 +/- 0.10 and 0.86 +/- 0.12 ml min-1 g-1, respectively) with coronary stenosis whereas subepicardial flow remained unchanged. Maximal systolic shortening deteriorated for both segments. However, it was most pronounced for longitudinal segments. Duration of shortening decreased in longitudinal segments during severe stenosis to 62% of duration with open shunt (P less than 0.05), but was unchanged in circumferential segments. Long/Circ ratio of maximal systolic shortening declined by 50% (P less than 0.05) with reduction of coronary perfusion pressure. The reduced uniformity of segment shortening, caused by a marked reduction of longitudinal segment shortening, may support the notion that the longitudinal segment reflects performance of subendocardial fibres. This study demonstrates local non-uniformity of two-dimensional deformation during coronary artery stenosis and subendocardial hypoperfusion.