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Long-term mortality with multiple treadmill exercise test abnormalities: comparison between patients with and without
Bilal Aijaz1, Luciano Babuin, Ray W Squires
1Department of Internal Medicine, Mayo Clinic, Rochester, MN 55905, USA. aijaz.bilal@mayo.edu
Insights
Multiple exercise test abnormalities predict mortality risk. Two or more abnormal results in patients without cardiovascular disease (CVD) may indicate a similar long-term mortality risk as those with known CVD.
Area of Science:
- Cardiology
- Preventive Medicine
- Exercise Physiology
Background:
- Poor exercise capacity, abnormal heart rate response, and ECG abnormalities on treadmill tests are independent mortality predictors.
- The combined prognostic value of these three variables was assessed in patients with and without known cardiovascular disease (CVD).
Purpose of the Study:
- To compare the combined relationship of exercise capacity, heart rate response, and ECG abnormalities with all-cause mortality.
- To determine if multiple exercise test abnormalities signify a "CVD risk equivalent" in individuals without diagnosed CVD.
Main Methods:
- Analysis of 10,897 patients referred for treadmill exercise testing (1986-1991), with a 16-year average follow-up.
- Abnormalities defined as exercise capacity <74%, heart rate reserve <68 bpm, or ST depression ≥1 mm.
- Cox proportional hazards regression used to assess mortality risk based on 0, 1, 2, or 3 abnormal exercise test findings.
Main Results:
- Poor exercise capacity and limited heart rate reserve increased mortality risk in both CVD and no-CVD groups (P < .0001).
- Abnormal exercise ECGs predicted mortality only in the no-CVD group (P < .0001).
- Patients without CVD and ≥2 abnormalities showed a similar age-adjusted mortality risk (HR 1.01) as those with CVD but normal tests.
Conclusions:
- A combined assessment of multiple exercise test variables confirms their prognostic significance.
- The presence of two or more exercise test abnormalities may represent a "CVD risk equivalent" in patients without known cardiovascular disease.
Background:
Poor exercise capacity, abnormal heart rate responses, and electrocardiographic abnormalities during treadmill exercise testing independently predict mortality. The combined relationship of these 3 variables to determine the incremental increase in mortality was compared in groups with and without known cardiovascular disease (CVD).
Methods:
Patients referred for treadmill exercise testing during 1986 to 1991 were included. Exercise capacity <74% (of age- and gender-predicted value), heart rate reserve of <68 beat/min, and horizontal or down-sloping ST depression of > or =1 mm were considered abnormal. Cox proportional hazards regression was used to determine all-cause mortality (average follow-up of 16 years) based on the number of exercise test abnormalities (0, 1, 2, or all 3).
Results:
Among 10,897 patients, 20.9% (n = 2,277) had CVD. Poor exercise capacity and limited heart rate reserve were associated with increased risk of mortality (P < .0001) in both groups; however, abnormal exercise electrocardiogram was associated with an increased risk of mortality in the no-CVD group only (P < .0001). A graded increase in mortality was observed with increase in number of abnormal exercise test results in both groups. Patients without CVD having 2 or 3 abnormal exercise test results had a similar age-adjusted risk of long-term mortality as those with CVD but normal exercise test results, with a hazard ratio comparing these groups = 1.01 (95% CI 0.79-1.28).
Conclusions:
The combinatorial approach validates the prognostic significance of multiple exercise test variables. The presence of > or =2 exercise test abnormalities may constitute a "CVD risk equivalent" in patients without CVD.
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