Anaerobic metabolism in hypertensive patients during exercise stress test

An impaired maximal vasodilating capacity has been reported in hypertensives. This study aimed to assess whether mild hypertensives depend on anaerobic metabolism more than do normal subjects during the exercise stress test. The oxygen uptake (VO2) and carbon dioxide output (VCO2) were measured at the anaerobic threshold (AT) and at peak exercise (VO2p and VCO2p) during the cardiopulmonary exercise test by breath-by-breath expiratory gas analysis in 21 mild hypertensives and 19 age-matched normotensives. AT was reached earlier in hypertensives than in normotensives, but with similar VO2 uptake, VCO2 output, and VCO2/VO2 ratio. At peak exercise, however, hypertensives showed lower VO2p than controls (29 +/- 5 v 33 +/- 5 mL VO2/kg/min, (P < .03) but similar VCO2p (36 +/- 6 v 39 +/- 6 mL VCO2/kg/min, P = .19). As a result, the slope of carbon dioxide output increase versus oxygen uptake after anaerobic threshold was steeper in hypertensives than in controls (P < .002). The higher CO2 production per unit of O2 in hypertensives as compared with controls seems to reflect a greater involvement of the anaerobic metabolism to supplement energy output.