Severity and response of chest pain during thrombolytic therapy for acute myocardial infarction: a useful indicator of myocardial salvage and infarct size

Division of Cardiovascular Diseases and Internal Medicine, Mayo Clinic, Rochester, Minnesota 55905.

OBJECTIVES. The purpose of this study was to determine noninvasively whether chest pain severity is predictive of the amount of myocardium at risk and whether the response of pain during thrombolysis is associated with myocardial salvage during acute myocardial infarction. BACKGROUND. The perception of chest pain and response to reperfusion therapy during acute myocardial infarction may provide important information for treatment benefit. Previous studies have been limited by the inability to measure myocardium at risk and myocardial salvage. METHODS. Sixty-two patients with acute myocardial infarction received an injection of technetium-99m sestamibi before thrombolysis and again at hospital discharge. Tomographic imaging was performed 1 to 6 h later. Myocardium at risk, infarct size and absolute myocardial salvage were derived from these images using previously described techniques and were expressed as a percent of the left ventricle. Salvage index was calculated by dividing myocardial salvage by the myocardium at risk. Chest pain severity was graded before thrombolysis as none, mild, moderate or severe. Chest pain response during thrombolytic therapy was graded as none, partial or completely resolved. RESULTS. There was no association between chest pain severity and myocardium at risk, but there was a weak trend toward greater myocardial salvage and salvage index (p = 0.09 and p = 0.12, respectively) for patients with more severe symptoms. Patients without chest pain at the start of thrombolysis still demonstrated significant salvage (11 +/- 11% of the left ventricle, p = 0.009). There was a significant association between chest pain response to therapy and both myocardial salvage (p = 0.03) and salvage index (p = 0.01). By multivariate analysis, chest pain severity and response of chest pain during thrombolysis were significant independent predictors of myocardial salvage, salvage index and infarct size. Thrombolysis was most effective in the 20 patients (32%) with moderate or severe chest pain and complete resolution of symptoms during thrombolysis (salvage of 79% to 89% of the area at risk). In the remaining 32 patients with chest pain, salvage of the area at risk was only 32%. CONCLUSIONS. These findings suggest that the assessment of chest pain before and after thrombolytic therapy is a readily available, useful indicator of the efficacy of the therapy.

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