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International Journal of Bioelectromagnetism Vol. 5, No. 1, p. 18, 2003. |
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www.ijbem.org |
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The Heart-Rate Recovery May be Influenced by
Beatriz M Ayub Ferreira, Paulo
J Moffa, Andréa Falcão, Augusto Uchida, Paulo Camargo Jr, Pascual Pereyra, Paulo
R Soares, Whady A Hueb, Jose AF Ramires Heart Institute (InCor), University of São Paulo Medical School - Brazil Abstract. The warm-up phenomenon,
observed after the second of two sequential exercise tests, is characterized
by an increased of both time to ischemia and ischemic threshold, and the last
one is probably related to a ischemic preconditioning. In the other hand, the
heart-rate recovery immediately after exercise, which may be a reflection of
decreased vagal activity, is a powerful predictor of overall mortality. This
study aimed to investigate the effects of ischemic preconditioning on the heart-rate
recovery during the first minute after graded exercise.
Methods. Twenty patients with chronic stable angina pectoris were enrolled and all were off treatment. They underwent two consecutive treadmill exercise tests according to the Bruce protocol with recovery period between the tests of 30 min to re-establish baseline conditions. The value for the recovery of heart rate was defined as the reduction in the heart rate from the peak exercise to the rate one minute after the cessation of exercise. Results. The heart rate and the rate-pressure product at 1.0mm ST-segment depression significantly increased during the second exercise test compared to the first (121.3 + 16.5 vs. 127.3 + 15.3 beats/min, p<0.001, and 216.7 + 43.1 vs. 232.1 + 43.0 beats mmHg.102/min, p<0.001); the time to 1.0 mm ST-segment depression during the second exercise test was greater than that during the first test, too (225.0 + 112.5 vs. 267.0 + 122.3 s, p=0.006).The median heart rate recovery increased significantly during the second test compared to the first (25.4+13.5 vs. 29.4 + 15.0 beats/min, p=0.02). Conclusion. The main findings of this study are an improvement of the ischemic threshold in the second test probably related to ischemic preconditioning and an improvement of the heart-rate recovery. Although there isn’t a clear explanation of this relation, it is clear that ischemic preconditioning represents a powerful protective phenomenon and the better heart rate recovery in the second compared to the first test may be an expression of this phenomenon.
© International Society for Bioelectromagnetism
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