981-49 Post Exercise Expired Gas Analysis in Patients with Dilated Cardiomyopathy

Abstract

In normal subjects, after a maximal exercise, oxygen consumption (VO 2 ) declines exponentially towards baseline value. Few studies have examined the kinetics of VO 2 after exercise in patients with dilated csrdiomyopathy (DCM). We studied the kinetics of post exercise VO 2 in 167 cardiopulmonary exercise tests performed in 153 ambulatory patients with DCM and in 45 controls. Patients and controls performed the same exercise (bicycle:l0 watts/min, Medical Graphic analyzer). Mean left ventricular ejection fraction was 29.8 ± 12% (mean ± SD). The VO2-time relationship was fitted to a monoexponential curve for the determination of the time constant of recovery (tRec). We calculated the ratio between total VO 2 during exercise and during recovery (RVO 2 , area under VO 2 curves), the half recovery time of peak VO 2 (½pVO 2 ), the post exercise anaerobic time (PEAT: time during recovery necessary for the respiratory exchange ratio (VCO 2 /VO 2 ) to become <1) and the ratio between exercise duration and PEAT (RPEAT). Patients were divided in 3 subgroups according to their peak VO 2 (>15, >10 and ≤10 ml/min/kg). Result: Contro >15 >10 ≤10 p n 45 88 53 26 Duration exercise s 1299 ± 375 844 ± 171 619 ± 114 445 ± 111 <0.0001 Peak VO 2 ml/min 2641 ± 893 1515 ± 362 995 ± 166 637 ± 176 <0.0001 Peak VCO 2 /VO 2 1.24 ± 0.11 1.26 ± 0.12 1.26 ± 0.12 1.28 ± 0.13 NS RVO 2 5.61 ± 2.48 2.9 ± 0.9 1.97 ± 0.63 1.41 ± 0.65 <0.0001 ½pVO 2 s 70.4 ± 29.4 105 ± 43.4 136 ± 57.7 173 ± 71.8 <0.0001 PEATs 428 ± 147 516 ± 166 535 ± 165 544 ± 208 <0.01 RPEAT 35 ± 189 178 ± 0.61 1.26 ± 0.45 0.97 ± 0.54 <0.0001 tRec s 80.3 ± 26.3 128 ± 120 142 ± 733 204 ± 158 <0.0001 In multiple regression analysis, the parameter most closely correlated with peak VO 2 was the RPEAT (F = 127, P < 0.0001). No relation was found between age or ejection fraction and post exercise parameters. In conclusion, recovery of VO 2 is delayed in patients with DCM and is related to the degree of exercise impairment. Post exercise parameters are a novel marker for exercise intolerance.