SHIFT TO THE RIGHT OF LACTATE THRESHOLD IN CHRONIC HEART FAILURE PATIENTS

PURPOSE: Studies of lactate levels during exercise in chronic heart (CHF) patients show conflicting results. This study investigated blood lactate levels during incremental exhaustive cycle ergometer exercise and the subsequent recovery in CHF patients. METHODS: In 15 male CHF patients (age: 59 ± 5 years, NYHA class II, LVEF 32.5 ± 4.6%; meanSD) and 15 controls(age: 48 ± 5 years) blood lactate levels during incremental exhaustive cycle ergometer exercise and the subsequent recovery were investigated. Every 3 minutes arterialised blood samples were collected. RESULT: Aerobic power and lactate levels at maximal exercise were lower in the patients than in controls (maximum workload (Wmax): 160 ± 29 and 212 ± 31 Watt; peak VO2: 21 ± 4 and 28 ± 5 mL/kg/min; maximal lactate: 9.8 ± 2.7 and 12.0 ± 3.5 mmol/L respectively; p < 0.05). However, both the lactate accumulation pattern relative to exercise intensity (%Wmax) and the pattern during the recovery were comparable for the two groups. Lactate threshold (LT) related to exercise intensity (%Wmax) was higher in the patients (77 ± 6 versus 73 ± 5%; p < 0.05). This phenomenon was more obvious in those patients whose peak VO2 was lower than the groups' median (i.e. 20mL/kg/min). CONCLSION: Although the overall lactate response to exercise in CHF patients is similar to that of controls, the shift of LT to the right with decreasing aerobic power is paradoxical. It may indicate that CHF patients are more sensitive to lactate accumulation than healthy controls and develop a stronger sensation of fatigue and that this sensitivity increases with severity of the disease.