Stunned myocardium after thrombolytic treatment. Identification by dobutamine echocardiography and role of the residual stenosis in the infarction artery

Abstract

The aim of this study was to identify post-thrombolysis stunned myocardium using low dose (10 μg/kg/min) dobutamine echocardiography, and to elucidate the role of the residual stenosis in the infarction artery in wall motion recovery. Forty-seven consecutive patients treated with thrombolytic agents for a first non-complicated myocardial infarction 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 observed 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 ≤ 0.01) and in Group IIA (931 ± 593, P ≤ 0.05) than in Group IIB (1547 ± 886). Late resting echocardiogram was performed in 44 patients: all 12 from Group I, 10 from Group IIA and 22 from Group IIB; all patients from Group I persisted with normal wall motion, while the baseline score index improved in seven patients (70%) from Group IIA vs. three patients (14%) from Group IIB ( P ≤ 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 creatine kinase peak ( P ≤ 0.05) and a positive response to dobutamine in the early echocardiogram ( P ≤ 0.001) correlated with wall motion recovery, but the minimum lumen diameter in the infarction artery did not correlate; by multiple logistic regression, only a positive response to dobutamine in the early echocardiogram independently predicted late wall motion improvement ( P ≤ 0.001). Conclusions: (1) Low dose dobutamine echocardiography early after thrombolytic treatment identifies dysfunctional myocardium with potential late spontaneous improvement (stunned myocardium). (2) Myocardial stunning tends to occur in small infarctions. (3) Late wall motion improvement can occur despite severe residual stenosis in the infarction artery.