Relationships between Anaerobic Threshold and Exercise Hemodynamic Pattern in Patients with Previous Myocardial Infarction

Abstract

In 78 male class I and II NYHA patients with previous myocardial infarction, the relationships between ventilatory anaerobic threshold levels and hemodynamic patterns during a maximal symptom-limited stress test in the supine position were studied. Among the 36 patients with abnormal exercise wedge values, 11 showed an anaerobic threshold (AT) < 35% of the maximal predicted VO₂(mpVO₂) (group A) and 23 showed an AT of 36–50% mpVO₂ (group B). In 2 patients, the AT was > 50% mpVO₂- Among the 42 patients with normal exercise wedge pressure, 13 showed an AT of 36–50% mpVO₂ (group C), whereas in 29 patients, the AT was > 50% mpVO₂ (group D). The mean value of AT in group A was significantly lower than in group B (8.6 ± 0.7 vs. 11.7 ± 0.5 ml/kg·min; p < 0.05). No difference was found in the mean of the AT between groups B and C, while the mean value of AT in group D was significantly higher than in group C (16.9 ± 0.4 vs. 12.9 ± 0.6 ml/kg·min; p < 0.005). No significant differences between groups C and D were found in the invasive and noninvasive parameters considered. Groups C and D were statistically different from groups A and B for pulmonary capillary pressures, total pulmonary resistances, stroke indexes, heart rates, arteriovenous O₂ differences, total systemic resistances and lactate concentrations. Total pulmonary resistances and heart rates were statistically higher and stroke indexes were statistically lower in group A than in group B. In conclusion: (1) patients with normal exercise wedge values show a higher AT than patients with abnormal exercise wedge values. (2) Patients with normal exercise hemodynamic patterns classified according to their AT show no difference in hemodynamics; in these patients the level of AT seems to be related to peripheral determinants. (3) Patients with abnormal exercise hemodynamic patterns classified according to their AT level show different hemodynamics and different responses in ventricular function; in these patients the level of AT seems to be related to the cardiac impairment.