Two-peaked increase of serum myosin heavy chain-α after triathlon suggests heart muscle cell death.

Objective: It has been suggested that the mechanism behind cardiac troponin elevation after strenuous exercise is passage through a cell membrane with changed permeability rather than myocardial cell death. We hypothesised that an increase of cardiac specific myosin heavy chain-alpha (MHC-α; 224 kDa compared with cardiac troponin T's (cTnT) 37 kDa) could hardly be explained by passage through a cell membrane.

Methods: Blood samples were collected from 56 athletes (15 female, age 42.5±9.7, range 24-70 years) before, directly after and on days 1-8 after an Ironman. Biomarkers (C reactive protein (CRP), cTnT, creatine kinase (CK), MHC-α, myoglobin (MG), creatinine (C) and N-terminal prohormone of brain natriuretic peptide (NT-proBNP) were measured.

Results: The course of MHC-α concentration (µg/L) was 1.33±0.53 (before), 2.57±0.78 (directly after), 1.51±0.53 (day 1), 2.74±0.55 (day 4) and 1.83±0.76 (day 6). Other biomarkers showed a one-peaked increase with maximal values either directly after the race or at day 1: cTnT 76 ± 80 ng/L (12-440; reference<15), NT-proBNP 776±684 ng/L (92-4700; ref.<300), CK 68±55 µkat/L (5-280; ref.<1.9), MG 2088±2350 µg/L (130-17 000; ref.<72) and creatinine 100±20 µmol/L (74-161; ref.<100), CRP 49±23 mg/L (15-119; ref.<5).

Conclusion: MHC-α exhibited a two-peaked increase which could represent a first release from the cytosolic pool and later from cell necrosis. This is the first investigation of MHC-α plasma concentration after exercise.