Prognostic Value of a Treadmill Exercise Score in Symptomatic Patients With Nonspecific ST-T Abnormalities on Resting ECG
- Jennifer M. F. Kwok, MB, ChB;
- Todd D. Miller, MD;
- Timothy F. Christian, MD;
- David O. Hodge, MS;
- Raymond J. Gibbons, MD
- Author Affiliations: Division of Cardiovascular Diseases and Department of Internal Medicine (Drs Kwok, Miller, Christian, and Gibbons) and Department of Biostatistics (Mr Hodge), Mayo Clinic and Mayo Foundation, Rochester, Minn; and Medical Department, Princess Margaret Hospital, Lai Chi Kok, Kowloon, Hong Kong (Dr Kwok).
Abstract
Context Exercise testing of patients with ST-T abnormalities on the resting electrocardiogram (ECG) is problematic because in the presence of pre-existing ST-T abnormalities, the exercise test is less specific for the diagnosis of coronary artery disease. The prognostic capability of the Duke treadmill score in patients with ST-T abnormalities vs those with normal findings on resting ECG has, to our knowledge, not been evaluated.
Objective To compare the prognostic accuracy of the Duke treadmill score in patients with nonspecific ST-T abnormalities vs those with normal results on resting ECG.
Design Inception cohort study with 7 years of follow-up.
Setting Nuclear cardiology laboratory of a US referral center.
Patients All symptomatic patients who underwent exercise thallium testing between 1989 and 1991, 939 of whom had nonspecific ST-T abnormalities and 1466 of whom had normal findings on resting ECG. Exclusion criteria included congenital, valvular, or cardiomyopathic heart disease; prior coronary artery revascularization; resting ECG with secondary ST-T abnormalities; or missing data.
Main Outcome Measures Rates of overall mortality and cardiac death for subjects classified by Duke treadmill score risk group.
Results For the end point cardiac death, 7-year survival in the study population in the low-, intermediate-, and high-risk groups was 97%, 92%, and 76%, respectively (P<.001). Compared with the control group, the study group had lower 7-year survival (94% vs 98%; P<.001), fewer low-risk patients (426 [45%] vs 811 [55%]; P<.001) with worse 7-year survival (97% vs 99%; P=.008), and more high-risk patients (49 [5%] vs 34 [2%];P<.001) with a nonsignificant trend toward worse 7-year survival (76% vs 93%; P=.36).
Conclusions The Duke treadmill score can effectively risk-stratify patients with ST-T abnormalities on the resting ECG. In classified risk categories, patients with ST-T abnormalities have a worse prognosis than those with normal results on resting ECG.
