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Prognostic value of a treadmill exercise score in symptomatic patients with nonspecific ST-T abnormalities on resting
J M Kwok1, T D Miller, T F Christian
1Department of Internal Medicine, Mayo Clinic and Mayo Foundation, Rochester, Minn 55905, USA.
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.