Exercise above the ischemic threshold and serum markers of myocardial injury.
BACKGROUND
Current guidelines for exercise training in coronary patients state that in the presence of exercise-induced ischemia, the heart rate during exercise should be at least 10 beats/min below the heart rate associated with an ST segment depression of 1 mm or greater. For patients with a relatively low ischemic threshold, this recommendation does not allow for a sufficient training stimulus.


OBJECTIVE
To document the effects of a single session of exercise above the ischemic threshold on biochemical markers of myocardial injury in stable coronary patients with exercise-induced ischemia. Because creatine kinase (CK) and its MB isoenzyme (CK-MB) can both increase after exercise because of skeletal muscle injury, troponin T was also measured.


METHODS
Twenty-one patients with documented coronary artery disease underwent two 20 min exercise sessions. The intensity of the first exercise training session was fixed at a heart rate below the ischemic threshold (ie, approximately 10 beats/min lower than the heart rate associated with the appearance of an ST segment depression of 1 mm or greater). The intensity of the second exercise session was fixed at a heart rate above the ischemic threshold.


RESULTS
Blood test measurements at baseline, 6 h after and 24 h after the exercise sessions did not show any increase in total CK, CK-MB or troponin. The value of all measurements remained well below the lower limits associated with myocardial damage.


CONCLUSIONS
A 20 min period of exercise above the ischemic threshold did not result in myocardial necrosis.
Juneau
Martin
M
Department of Medicine, Montreal Heart Institute, Montreal, Canada. martine.juneau@icm-mhi.org
Roy
Nathalie
N
Nigam
Anil
A
Tardif
Jean Claude
JC
Larivée
Lucie
L
D015415:Biomarkers / Q000097:blood; D003324:Coronary Artery Disease / Q000097:blood / Q000503:physiopathology / Q000534:rehabilitation*; D003402:Creatine Kinase / Q000097:blood*; D052279:Creatine Kinase, MB Form / Q000097:blood*; D004562:Electrocardiography; D005080:Exercise Test / Q000379:methods*; D005081:Exercise Therapy / Q000379:methods*; D017079:Exercise Tolerance / Q000502:physiology*; D005500:Follow-Up Studies; D006339:Heart Rate / Q000502:physiology; D006801:Humans; D008297:Male; D008875:Middle Aged; D011379:Prognosis; D020107:Troponin T / Q000097:blood*
D015415:Biomarkers; D020107:Troponin T; D003402:Creatine Kinase; D052279:Creatine Kinase, MB Form