Background: The aim of this study was to define the diagnostic accuracy and the prognostic significance of stress electrocardiography (ECG) and of thallium-201 single-photon emission computed tomography (SPECT) in determining the incidence of coronary artery disease (CAD) in an elderly population.
Methods: A selected series of 132 patients (90 males, mean age 72.4 years; 42 females, mean age 68.2 years) hospitalized because of cardiac events associated with suspected CAD, underwent stress ECG and thallium-201 testing; as endpoints we considered the heart rate and the appearance of clinical symptoms or ST segment depression. Patients unable to develop an adequate exercise workload, were tested with dipyridamole. All patients also underwent coronary angiography following the stress test. One hundred and twenty-four patients had a mean follow-up of 2 years. Endpoints included subsequent coronary events or new serious disease. The sensitivity, specificity, diagnostic accuracy, and positive and negative predictive values of both ECG and of thallium-201 SPECT were calculated.
Results: ECG findings were positive in 102 patients and coronary angiography confirmed the presence of CAD in 92 of them; ECG findings were negative in 30 patients, but only 14 were free from obstructive coronary lesions. Thallium-201 SPECT findings were positive in 112 patients (coronary angiograms confirmed CAD in 101) and negative in 20 patients (in 13 of whom angiography confirmed the absence of disease). The sensitivity of the stress tests was quite good: 85.1% for ECG and 93.5% for thallium-201 SPECT; conversely, the specificity of ECG was superior to that of SPECT (58.3 vs 54.1%). The sensitivity of both techniques was superior in males than in females and seemed to correlate with the extent of CAD.
Conclusions: The diagnostic accuracy of thallium-201 SPECT was 86.3% whereas that of ECG was 80.3%. Considering the overall cardiac events, the predictive value of SPECT was superior to that of ECG both in terms of the positive value (54 vs 51%, p = NS) and, more importantly, in terms of the negative value (84 vs 62%, p < 0.03). In fact, patients with normal thallium images were at low risk for future cardiac events.