RESIDUAL CORONARY RESERVE IDENTIFIES SEGMENTAL VIABILITY IN PATIENTS WITH WALL-MOTION ABNORMALITIES

Objectives. The aim of this study was to determine whether the presenc e of residual coronary reserve can in itself identify viable segments. Background. Experimental data suggest that despite hypoperfusion at r est, viable myocardium may exhibit persistence of coronary reserve. Pr eliminary observations in patients show that in basally dyssynergic ar eas, a residual vasodilator capability is present despite hypoperfusio n at rest and that a flow-mediated increase in regional wall motion id entifies residual viability. Methods. Fourteen patients with evidence of previous myocardial infarction, infarct-related single-vessel coron ary artery disease and impaired regional ventricular function at rest underwent positron emission viability imaging by fluorine-18 deoxygluc ose. In addition, blood bow at rest and vasodilator capability were re gionally evaluated in all patients by means of nitrogen-13 ammonia. Re sults. Of a total of 252 segments, 133 were dyssynergic at rest. Of th ese 133 segments, 60 (group 1) showed normal metabolic activity and on ly mild reduction in myocardial blood flow. The other 73 segments show ed a marked reduction in how of these, 25 (group 2, viable) had persis tent metabolic activity, whereas 48 (group 3, necrotic) did not. Despi te similar levels of hypoperfusion at rest, group 2 segments showed a preserved coronary reserve that was virtually absent in necrotic segme nts (2.6 +/- 1.3 vs. 1.3 +/- 0.5, p < 0.01). This value was similar to that observed in viable group I segments (2.5 +/- 1.6, p = NS). Concl usions. In addition to characterizing myocardium at risk, imaging of c oronary flow at baseline and after dipyridamole by positron emission t omography provides helpful information on myocardial viability that ma y integrate the ''static'' viability information obtained with the bas eline flow/metabolic approach.