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Cardiac troponin I: a potential marker of exercise intolerance in patients with moderate heart failure.

BACKGROUND
In severe heart failure, increased values of cardiac troponins have been detected during decompensation. In this study, we investigated whether an increase of cardiac troponin I can be observed after symptom-limited exercise and after an exercise training session in patients with moderate heart failure.


METHODS
Twenty-seven patients with moderate heart failure (New York Heart Association II-III, ejection fraction 31% +/- 8%) were compared with 9 patients with mild heart failure and 10 subjects without heart failure. They underwent a symptom-limited exercise test and a bicycle exercise training session at >80% of maximal heart rate over 20 to 30 minutes. Plasma cTnI levels were measured at baseline, after symptom-limited exercise (hourly for 5 hours), and after training (4 and 10 hours).


RESULTS
Patients with moderate heart failure showed an increase of cTnI from 37 +/- 49 pg/mL to 73 +/- 59 pg/mL (P <.001) after symptom-limited exercise. Four patients with moderate and 1 with mild heart failure and normal cTnI values at rest showed an increase of cTnI above 100 pg/mL after acute exercise but not after training. Subjects without heart failure had lower cTnI levels at rest and significantly lower values after symptom-limited exercise and training (P <.05 for each).


CONCLUSION
Patients with symptomatic heart failure reveal an increase of cTnI after symptom-limited exercise at levels that indicate minor myocardial damage. The prognostic impact of this finding should, therefore, be further investigated.