Overshoot phenomenon of oxygen uptake during recovery from maximal exercise in patients with previous myocardial infarction

Abstract

The overshoot in oxygen uptake ( V̇ O2 overshoot) during recovery from maximal exercise is thought to reflect an overshoot in cardiac output. We investigated whether this phenomenon is related to cardiopulmonary function during exercise in cardiac patients. A total of 201 consecutive patients with previous myocardial infarction underwent cardiopulmonary exercise testing (CPX). An apparent V̇ O2 overshoot during the recovery from CPX (6.5 ± 8.1% increase relative to the peak V̇ O2) was observed in ten patients. A comparison of patients with the V̇ O 2 overshoot to those without the V̇ O2 overshoot revealed that the former had a significantly lower left ventricular ejection fraction (40.1 ± 19.1 vs. 55. 2 ± 14.9%, respectively, p = 0.002) and larger left ventricular diastolic and systolic dimensions. Patients with the V̇ O2 overshoot also had a significantly lower peak V̇ O2 (13.1 ± 6.1 vs. 18.1 ± 4.5 ml/min/kg, p < 0.001), lower Δ V̇ O2/ΔWR (work rate) (6.6 ± 3.8 vs. 9.5 ± 1.7 mL/min/W, p < 0.0001), and a higher V̇ E (minute ventilation)/ V̇ CO2 (carbon dioxide output) slope (45.0 ± 18.6 vs. 32.6 ± 6.6, p < 0.0001) than those without the overshoot. A V̇ O2 overshoot during recovery from maximal exercise was found in 5% of patients with previous myocardial infarction. This condition, which suggests a transient mismatch between cardiac contractility and afterload reduction, was found to be related to impaired cardiopulmonary function during exercise. © 2009 The Physiological Society of Japan and Springer.