The effect of exercise and heart rate on fibrinolytic activity

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Abstract
The effect of heart rate on plasma fibrinolytic activity was investigated in nine patients with dual chamber cardiac pacemakers before and after 10 min of stimulated tachycardia to 123 beats/min. The results were compared to seven volunteers who performed submaximal exercise to 90% target heart rate and to five of the seven who underwent a second period of exercise to a heart rate of 120 beats/min. During submaximal exercise (mean heart rate 152 beats/min) the median ECLT fell from 248 min (interquartile range 147.5–305) to 90 (55–202) P < 0.01 and t-PA:Ag increased from 6.1 ng/ml (3.92–7.95) to 9.3 (8.45–12.7), P< 0.025. PAI and PAI-l:Ag fell from 12.0 IU/ml (5.85–15.5) to 4.1 (1.85–11.67), P P < 0.01 respectively. A lower level of exercise to 120 beats/min resulted in a reduction in ECLT from 215 min (167.5–228.5) to 135 (116–154), P = 0.05 and an increase in t-PA:Ag from 4 ng/ml (3.07–4.45) to 5.0 (3.3–5.22) P< 0.05. PAI and PAM:Ag fell from 7.6 IU/ml (3.27–8.5) to 7.1 (2.77–7‘.4) and from 7.7 ng/ml (6.0–7.92) to 6.4 (4.8–7.3) respectively but these changes were not statistically significant. In contrast, pacemaker stimulated tachycardia (mean 123 beats/ min) resulted in no significant changes in ECLT 225 min (161–272) vs 200 (156–303), tPA:Ag 7.7 ng/ml (4.05–8.27) vs 8.5 (4.82–8.95), PAI 18.2 IU/ml (12.2–33.1) vs 19.4 (12.85–33.9) and PAI-l:Ag 17.9 ng/ml (4.47–33.3) vs 18.8 (5.42–31.27). The results indicate that changes in heart rate do not contribute to the increase in fibrinolytic activity associated with exercise.

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