Onset of Intolerance Symptoms during Exercise Testing Is a Reproducible Threshold for Evaluation of Cardiac Function

Twenty-one male patients with a history of myocardial infarction underwent bicycle cardiopulmonary exercise testing. The onset of leg pain or dyspnea, which reflects anaerobic metabolism, was termed anaerobic exercise symptom threshold (AEST). Our aims were (1) to evaluate the temporal relationship between AEST and the ventilatory anaerobic threshold (VAT) and (2) to determine whether heart rate, rate-pressure product, exercise time, and the ventilatory parameters at AEST are reproducible and correlate with the same parameters at VAT. AEST overlapped VAT in 4 patients and lagged behind VAT in 15. AEST never preceded VAT. The mean exercise time at VAT was 4.1 +/- 1.2 min and at AEST 5.6 +/- 1.6 min (p < 0.0001); the mean heart rate was 97 +/- 10 and 107 +/- 12, respectively (p < 0.001). The mean values of the rate-pressure product and the oxygen consumption at AEST were significantly higher than at VAT. The correlation coefficient ranged from r = 0.74 to r = 0.93. Fifteen patients were examined twice within 1 month; the above parameters were reproducible at AEST, VAT, and peak exercise. In conclusion, AEST, which is easily recorded during bicycle exercise testing, is useful as a reference point for evaluation and follow-up of the cardiac aerobic function.