Factors influencing estimated oxygen uptake during exercise testing soon after myocardial infarction

To determine the extent to which oxygen uptake (VO₂) estimated from exercise testing in healthy adults is applicable to patients tested soon after myocardial infarction, v?O₂ was measured during symptom-limited treadmill testing 3 and 11 weeks after the acute event. Twenty-two men (Group I) underwent treadmill testing using a “standard” modified Balke protocol (3 miles/h [80 m/min] with 2.5 percent increments in grade every 3 minutes) 3 and 11 weeks after infarction. Twenty-five clinically similar men (Group II) underwent treadmill testing using a standard protocol at 3 weeks but an “accelerated” protocol (3 miles/h with 5 percent increments in grade every 3 minutes) at 11 weeks. Measured and estimated values of peak v?O₂ were nearly identical for both groups of patients performing the standard protocol at 3 weeks (mean ± standard deviation 20.5 ± 4.7 versus 20.4 ± 6.1 and 22.1 ± 4.1 versus 22.5 ± 4.5 ml/kg per min for Groups I and II, respectively). Measured and estimated values of peak v?O₂ were also similar for patients completing the standard protocol at 11 weeks (26.3 ± 7.6 versus 26.7 ± 6.9 ml/kg per min). In contrast, estimated values of peak v?O₂ were significantly higher than measured values in patients completing the accelerated protocol at 11 weeks (30.8 ± 4.3 versus 27.7 ± 5.0 ml/kg per min (probability [p] = 0.001). Holding onto the treadmill handrails significantly increased estimated peak v?O₂ (32.7 to 37.9 ml/kg per min) but did not affect measured peak v?O₂ (32.1 to 31.8 ml/kg per min). These results indicate that v?O₂ for patients performing treadmill exercise testing after myocardial infarction can be estimated from data derived from healthy adults so long as the exercise intensity is increased slowly and holding onto the handrails is avoided.