[Changes in cardiac output during exercise in patients with hypertrophic cardiomyopathy: the study of these...

In order to investigate the relation between exercise intolerance and cardiac output (CO) increase during exercise in patients with hypertrophic cardiomyopathy (HCM), submaximal treadmill exercise (Sheffield protocol) with simultaneous measurement of CO and oxygen uptake (VO2) by acetylene rebreathing method were performed in twelve patients with HCM who had no demonstrable left ventricular outflow obstruction and fifteen control men. The measurements were made at rest, during exercise and recovery. 1) At rest cardiac index (CI) in patients with HCM was significantly less than in control subjects but the difference was small (HCM: 1.9 +/- 0.35 l/min/m2 vs control: 2.2 +/- 0.38, p less than 0.05), and was almost the same during light exercise (stage 1-3), but clearly increased during middle to submaximal stages (stage 4 and 5) (stage 5: 4.5 +/- 1.25 vs 8.0 +/- 1.30, p less than 0.01). 2) Heart rate was not different in both groups at rest, during exercise and recovery, which was considered to explain that the difference of CI was derived from that of stroke index (SI). 3) The change of VO2 showed the same tendency as that of CI. The difference increased considerably during the middle to submaximal stages (Stage 5: 15.3 +/- 1.42 ml/min/kg vs 25.4 +/- 4.42, p less than 0.01). 4) During recovery, CI and VO2 in patients with HCM indicated a delay of beginning to decrease toward the rest level, compared with control subjects. 5) VO2 was closely related to CI (r = 0.90, p less than 0.01).(ABSTRACT TRUNCATED AT 250 WORDS)