STUNNED MYOCARDIUM AFTER THROMBOLYTIC TREATMENT - IDENTIFICATION BY DOBUTAMINE ECHOCARDIOGRAPHY AND ROLE OF THE RESIDUAL STENOSIS IN THE INFARCTION ARTERY

The aim of this study was to identify post-thrombolysis stunned myocar dium using low dose (10 mu g/kg/min) dobutamine echocardiography, and to elucidate the role of the residual stenosis in the infarction arter y in wall motion recovery. Forty-seven consecutive patients treated wi th thrombolytic agents for a first non-complicated myocardial infarcti on were included. An early dobutamine echocardiogram was performed 7 /- 2 days after thrombolysis to calculate a wall motion score index at baseline and with dobutamine. A late resting echocardiogram 36 +/- 7 days and a coronariography 41 +/- 8 days after thrombolysis were also performed. In 12 patients no baseline regional dysfunction was observe d in the early echocardiogram (Group I), whereas 35 patients (Group II ) presented regional dysfunction which improved with dobutamine in 11 cases (Group IIA), but not in 24 (Group IIB). Maximum creatine kinase peak was smaller in Group I (458 +/- 162, P less than or equal to 0.01 ) and in Group IIA (931 +/- 593, P less than or equal to 0.05) than in Group IIB (1547 +/- 886). Late resting echocardiogram was performed i n 44 patients: all 12 from Group I, 10 from Group IIA and 22 from Grou p IIB; all patients from Group I persisted with normal wall motion, wh ile the baseline score index improved in seven patients (70%) from Gro up IIA vs. three patients (14%) from Group IIB (P less than or equal t o 0.01). Quantitative angiographic parameters in the infarction artery failed to differentiate the subgroup of patients in whom wall motion improved in the late echocardiogram. By simple regression, smaller cre atine kinase peak (P less than or equal to 0.05) and a positive respon se to dobutamine in the early echocardiogram (P less than or equal to 0.001) correlated with wall motion recovery, but the minimum lumen dia meter in the infarction artery did not correlate; by multiple logistic regression, only a positive response to dobutamine in the early echoc ardiogram independently predicted late wall motion improvement (P less than or equal to 0.001). Conclusions: (1) Low dose dobutamine echocar diography early after thrombolytic treatment identifies dysfunctional myocardium with potential late spontaneous improvement (stunned myocar dium). (2) Myocardial stunning tends to occur in small infarctions. (3 ) Late wall motion improvement can occur despite severe residual steno sis in the infarction artery.