Unstable coronary artery disease : non-invasive indicators of severity of coronary lesions and the effects of thrombolysis
Abstract: Non-invasive indicators of severity of coronary lesions and the effects of thrombolysis were evaluated in 205 men, 38 to 70 years of age with unstable coronary aticty disease (CAD)- i.e. unstable angina or non-Q wave myocardial infarction - admitted to the coronary care units in nine hospitals. The patients were randomised to double-blind and placebo-controlled treatment with an intravenous infusion of recombinant tissue-type plasminogen activator (tt-PA) in addition to aspirin, heparin and betablockade. A symptom-limited exercise test was performed before discharge in 190 patients and a second exercise test, combined with thallium-201 SPECT, was performed after one month in 170 patients. Coronary angiography was performed in 199 patients after one month when also exercise echocardiography and 48 hours ambulatory ST-recording were performed in 65 and 95 patients respectively. The non-invasive tests were compared to each other and to coronary angiography in order to elucidate the best method to identify patients with severe coronary lesions -defined as three vessel disease, left main stenosis or proximal left anterior descending artery stenosis as part of two vessel disease.Thrombolytic treatment with rt-PA did not reduce the incidence of death, myocardial infarction or urgent revascularisation early or during one year follow-up. Myocardial ischemia, defined as death, myocardial infarction, revascularisation because of refractory angina or signs of ischemia at an exercise test, was reduced by treatment with rt-PA both at discharge, 53%compared to 70% (p=0.02), and after one month, 61% compared to 80% (p=0.005) respectively. No severe side-effects of rt-PA occurred.Stepwise multiple regression analysis showed that ST -depression and low maximal work load were the most important exercise variables for identification of severe coronary lesions. Using a combination of these parameters, the sensitivity and specificity for identification of severe coronary lesions were respectively 77% and 70%. More sophisticated methods of evaluating the ECG reaction during exercise were not diagnostically superior to the simple identification of ST-depression of > 0.1 m V.In patients with ST -depression at ambulatory monitoring, 79% demonstrated lhe same finding at the exercise test. A "high risk exercise test response" defined as either ST-depression in:?. 3 leads or ST -depression in 1 - 2 leads with a maximal work load below the 60th percentile or a maximal work load below the 30th percentile regardless of the ECG reaction during exercise, occurred in 82%, while ST -depression at ambulatory monitoring was observed only in 41% of the patients with severe coronary lesions (p<O.OOI).A combination of thallium-201 SPECT and ECG at exercise testing identified 82% of the patients with severe coronary lesions with a specificity of 63%. Furthermore, thallium-201 SPECT identified more patients with isolated proximal left anterior descending artery stenosis than the exercise test alone.Wall motion abnormalities at exercise echocardiography were seen in 53 patients (81 %) at rest and perfusion defects at thallium-201 SPECT in 57 patients (88%) in the rest images. New or worsening of wall motion abnormalities were seen in 55 patients (180 segments) either seated at peak exercise or recumbent after exercise whereas 43 patients (105 segments) had reversible or partially reversible thallium-201 SPECT scintigraphic defects (p=0.02). The segmental agreement between wall motion abnormalities and scintigraphic defects was low (58%). Theadditional value of exercise echocardiography to the exercise test was greatest in patients with one vessel disease.Based on the present and other studies, thrombolysis can not be recommended as a routine therapy in unstable CAD. An early exercise test is safe and contributes to the identification of patients with severe coronary lesions who might benefit from revascularisation. Thallium-201SPECT and exercise echocardiography one month after an episode of unstable CAD have additional value to an ordinary exercise test for the identification or exclusion of severe coronary lesions, while ST -recording has no additional value.
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