Abstract 2604: Hemoglobin is a Predictor of Exercise Testing Performance and Exercise-Induced Ischemia
Background: While hemoglobin is a known predictor of cardiovascular (CV) death following acute myocardial infarction, little is known about its effect on clinical exercise test performance. We hypothesized that subjects with low hemoglobin would have poor exercise capacity and would be more likely to exhibit exercise-induced ischemia.
Methods: Clinical variables, laboratory values, exercise treadmill data, and event data were obtained for 1,959 subjects referred for exercise treadmill testing for clinical reasons between 1996 to 2003. Stepwise multivariable regression analysis was performed to determine which variables predicted exercise performance. P-values<0.05 were considered significant.
Results: Our population had a mean age of 57±12 years, 95% were male, 16% had diabetes, 51% had hypertension, 35% had hypercholesterolemia, and 66% had a history of smoking. Male patients with hemoglobin gm/dl <13 (n=161) achieved lower METs than male patients with hemoglobin>=13 gm/dl (n=1637) (6.4±0.2 vs 8.7±0.1, p<0.0001). Significantly more male patients with hemoglobin<13 had ST depression than patients with a hemoglobin>=13 (15.5% vs 8.6%, p<0.004). In stepwise multivariable regression analysis, hemoglobin (p<0.0001) significantly predicted exercise performance (METs), along with age, BMI, activity status, pack-years of smoking, WBC count, typical angina, claudication, COPD, and CHF. Hemoglobin level predicted exercise-induced ST depression, along with age, typical angina and administration of statins, digoxin or nitrates.
Conclusion: Hemoglobin level is a powerful predictor of exercise performance and the occurrence of ST segment depression during exercise testing. Lowered levels of hemoglobin are associated with impaired exercise performance and exercise-induced ischemia.