Relationship between changes in regional myocardial contraction and energy metabolism following coronary flow reduction.

Abstract

To investigate the relationship between mechanical and metabolic deterioration in the ischemic myocardium following a decrease of coronary blood flow, the patterns of regional myocardial contraction and myocardial adenosine triphosphate (ATP) content were analyzed simultaneously in canine left ventricles with constriction of the left anterior descending coronary artery (LAD). The patterns of contraction in the ischemic region were monitored by means of ultrasonic dimension gauges implanted in the endocardial surface and were classified into 5 types; Type 0 = normal, Type I = late systolic lengthening, Type II = early and late systolic lengthening with end diastolic length elongation, Type III = systolic bulge with early diastolic shortening, and Type IV = holosystolic bulge. Type I developed in 6/8 dogs with 1-49% LAD flow reduction, Type II in 6/8 dogs with 50-74% reduction, and Types III and IV in all dogs with 75-100% reduction. The myocardial ATP content (microM/Gm tissue) at the sites of the patterns of myocardial contraction measurement was analyzed. No differences in ATP content were noted between Type 0 and Type I (3.70 +/- 0.51 vs. 3.60 +/- 0.36). In contrast, the ATP content in Type II was significantly reduced (2.94 +/- 0.20) compared to Type I (p less than 0.005). In Types III + IV with systolic bulge, the ATP reductions were severer (2.59 +/- 0.36) than in Type II (p less than 0.05). In conclusion, it can be said that as the LAD flow reduction advanced, the patterns of myocardial contraction were transformed from Type 0 to Type IV with accompanying ATP reductions.