[Thallium-dipyridamole in acute myocardial infarction treated by thrombolysis: diagnostic and prognostic value]

The management of patients who received thrombolytic therapy for acute myocardial infarction is still controversial. It is not clear if the strategies usually followed after myocardial infarction for risk stratification have the same value when applied to patients treated with thrombolysis.

To assess the diagnostic and prognostic value of dipyridamole thallium-201 scintigraphy in the "thrombolytic era", we studied 110 consecutive patients younger than 75 recovering from first uncomplicated acute myocardial infarction treated with thrombolytic agents. Patients with early angina, recurrent acute myocardial infarction, heart failure, life-threatening arrhythmias, non Q wave myocardial infarction were excluded. Ninety patients were treated with streptokinase, 14 with rtPA, 6 with APSAC: All patients underwent dipyridamole thallium scintigraphy with standard dose and coronary angiography before discharge (10-20 days). Ninety-nine patients underwent exercise test. All patients were followed-up for 22 +/- 9 months (range 8-42). Perfusion abnormalities were classified as reversible (totally or partially) defects or persistent defects and within or outside the infarct zone.

Fifty-eight patients developed anterior and 52 inferior acute myocardial infarction. Coronary angiography showed single vessel coronary artery disease in 66 patients, multivessel disease in 34, and normal coronary arteries or sub-critical stenosis in 10. No major complications (death, myocardial infarction, threatening arrhythmias, prolonged severe hypotension) occurred after dipyridamole infusion. Sixty-two patients had reversible perfusion defects at thallium scanning (34 within the infarct zone, 21 within and outside the infarct zone, 7 outside); 38 patients had persistent defects; 10 patients had a normal scintigraphic pattern. The diagnostic value of homozonal perfusion reversible defects for identifying a patent infarct-related vessel was poor (sensitivity 69.7%, specificity 64.7%). The diagnostic values of the same scintigraphic pattern improved in detecting patent infarct-related artery with residual critical stenosis (sensibility 75.4%, specificity 77.3%); in all the false positive cases (reversible defects within the infarct zone and occluded infarct-related artery) a good collateral flow was present. The sensitivity of reversible defects outside the infarct zone in detecting multivessel disease was 64.7% vs 56.3% of exercise test; the specificity was 92% vs 64%; the positive predictive value 78.6% vs 44%; the negative predictive value 85.3% vs 74.5%; the diagnostic accuracy 83.6% vs 61.4%. During the follow-up 2 deaths, 7 recurrent myocardial infarction, 1 sustained ventricular tachycardia, 1 heart failure, 13 recurrence of unstable angina and 9 revascularization procedures occurred among patients with reversible defects (either within or outside the infarct zone) at thallium scanning. One recurrent myocardial infarction, 4 recurrence of unstable angina and 2 revascularization procedures were the events among patients with persistent defects or normal scintigraphic pattern (p < 0.001). Ischemic events occurred with similar frequency in patients with reversible perfusion defects within the outside the infarct zone (55% vs 50%, NS).

Dipyridamole thallium-201 scintigraphy performed after uncomplicated myocardial infarction treated with thrombolytic agents is a valuable diagnostic tool in identifying viable jeopardized myocardium within the infarct zone perfused by a patent but critically narrowed vessel; it shows better diagnostic accuracy in detecting multivessel disease than does the exercise test and is able to identify a subset of patients at risk for future ischemic events after thrombolytic therapy.