An appraisal of dipyridamole thallium imaging-detected ischemia in Chinese following acute myocardial infarction.

BACKGROUND

The detection of objective myocardial ischemia is an important work-up of risk stratification for survivors of acute myocardial infarction (MI). Intravenous dipyridamole thallium scintigraphy was used to identify the prevalence and prognostic value of silent myocardial ischemia (SI) at the early stage in patients after MI.

METHODS

Ninety patients (male/female = 87/3; aged from 36 to 70 years) who succumbed to an episode of MI was recruited in this prospective study. Thallium imaging with reversible or combined defect was defined as presence of SI (Group I), while those with fixed defects or normal images were defined as absence of SI (Group II). Correlation between the patterns of thallium images for postinfarct ischemia and the angiographic lesions was investigated. Also, versatile clinical variables and indexes of adverse cardiac events: unstable angina, CHF, reinfarction, ventricular tachyarrhythmia and sudden death, were evaluated for their influence on patients' prognosis. The average follow-up was 11.6 months.

RESULTS

There were 61 patients in the Group I as compared with 29 patients in the Group II. The difference of Killip functional classification between Group I and Group II patients was not significant (1.33 +/- 0.72 versus 1.07 +/- 0.59). Adverse cardiac event occurred in 30% (27/90) of the patients during follow-up. Cardiac death occurred in 6 cases (7%) and were distributed evenly (3 versus 3) in both groups. Group I patients showed a higher number of nonfatal reinfarctions (8 versus 5) and had more cases of percutaneous coronary angioplasty (11 versus 8) than Group II patients. Only two cases in Group I underwent bypass graft surgery. There was no statistic difference among four patterns of thallium image in the cumulative event-free survival curve. Prior history of CHF, prior MI and higher score index of proximal arterial stenosis were the three significant prognostic predictors for late cardiac events.

CONCLUSIONS

Dipyridamole thallium imaging-detected SI was frequently seen in the Chinese patients following AMI. It was less valuable than prior histories of CHF, prior MI and higher index of proximal arterial stenosis scores in predicting the short-term unfavorable cardiac events in these patients. A large scale analysis and longer follow-up might be required to more accurately determine the role of this exam for the Chinese victims of myocardial infarction.