Relation between coronary "steel" and contractile function at rest in collateral-dependent myocardium of humans with ischemic heart disease

Background-We tested the hypothesis that rest asynergy in collateral-depend ent myocardium correlates with coronary steal. Methods and Results-PET with [N-13]ammonia measured myocardial blood flow a nd flow reserve in 15 patients with symptomatic chronic ischemic heart dise ase. Coronary angiography assessed stenosis severity and collateral blood s upply. Echocardiography or contrast ventriculography evaluated regional wal l motion. Collateral-dependent segments with normal flow at rest and suppli ed by coronary vessels having less than or equal to 50% diameter stenosis w ere studied. Steal was defined as a decline in myocardial blood flow with a denosine greater than or equal to 0.15 mL.min(-1).g(-1) versus rest. Blood now at rest in asynergic, collateral-dependent segments with steal (1.15+/- 0.35 mL.min(-1).g(-1)) exceeded (P<0.0001) that of asynergic segments witho ut steal (0.81+/-0.24) and those with normal contraction (0.77+/-0.18). Alt hough the flow reserve ratio of segments with normal contraction (1.8+/-0.8 ) exceeded that of asynergic ones with (0.5+/-0.1) or without (1.3+/-0.4) s teal, overlap was great. Correlation between basal contraction and flow res erve ratio in collateral-dependent myocardium was significant but weak (r=0 .45, P<0.001). However, segments demonstrating "steal" with adenosine manif ested asynergy in 22 of 23 collateral-dependent segments versus 24 of 39 no nsteal segments (chi(2)=7.10, P<0.01). Conclusions-Although myocardial flow reserve in collateral-dependent segmen ts with normal contraction exceeded that of asynergic segments, overlap was great. However, in patients with angina or congestive heart failure, left ventricular segments demonstrating steal with adenosine almost always exhib it asynergy at rest. Thus, coronary steal may play an important role in the pathogenesis of chronic contractile impairment at rest, whereas simple red uction of flow reserve may be less important in selected patients.