Long term prognosis in patients with normal exercise thallium-201 scans: A five-year followup study

While a normal exercise thallium-201 scan does not exclude coronary artery disease, it may offer important prognostic potential. To determine the long term prognosis in patients with normal thallium scans, the authors studied 118 consecutive patients (80 males, 38 females; age 50 +- 10 years, mean +- 1SD) referred to their laboratory in 1979 for exercise thallium imaging, whose scans were judged by 3 experienced observers to be normal. All patients were successfully followed for 5 years. Based on Diamond-Forrester criteria of age, sex and type of chest pain, the pretest likelihood of coronary artery disease in this group was 41 +- 24%. The indications for thallium scan included typical angina in 18, atypical angina in 72, and an abnormal exercise ECG in 18. Eighty patients reached 85% of their predicted maximum heart rate. Of 22 patients subsequently undergoing coronary angiography, 8 (36%) had significant coronary artery disease (>50% luminal narrowing). On followup, there was no death in this group. However, there were 5 non-fatal cardiac events (4%) including one myocardial infarction and 4 cases of unstable angina (necessitating coronary bypass surgery in 3 patients), occurring an average of 3.1 +- 2.4 years after the initial scan. These 5 patients with events all had 2 or more risk factors for coronary artery disease, and 4 of 5 patients exercised inadequately to less than 85% of their predicted maximum heart rate. The authors conclude that the long term prognostic value of a normal thallium scan is excellent with a cardiac event rate of <.9% per year and no mortality. This is compatible with the cardiac event rate in a comparable normal U.S. population of the same age group