We measured erythrocyte creatine in 92 HCM patients. Twelve patients had left ventricular outflow tract obstruction (LVOTO), 4 had midventricular obstruction (MVO), and the remaining 76 were non-obstructive. Erythrocyte creatine levels ranged from 0.92 to 4.36 μmol/g hemoglobin. Higher levels of erythrocyte creatine were associated with higher IVPG (r = 0.437, p < 0.001). If erythrocyte creatine levels are high (≥1.8 μmol/g hemoglobin), subclinical hemolysis is considered to be present. Half of LVOTO patients and no MVO patients showed high erythrocyte creatine levels. Although non-obstructive patients did not show significant intraventricular obstruction at rest, some showed high erythrocyte creatine levels. When LVOT-PG was measured during the strain phase of the Valsalva maneuver in 20 non-obstructive patients, 7 of those 20 patients showed LVOTO. In the 20 patients, there was no relation between erythrocyte creatine levels and LVOT-PG before the Valsalva maneuver (r = 0.125, p = 0.600), whereas there was a significant correlation between erythrocyte creatine and LVOT-PG provoked by the Valsalva maneuver (r = 0.695, p = 0.001).
There is biochemical evidence of subclinical hemolysis in patients with HCM, and this hemolysis seems to be associated with LVOTO provoked by daily physical activities.