Correspondence
Recovery of Heart Rate after Exercise
N Engl J Med 2000; 342:662-663March 2, 2000
- Article
To the Editor:
In their article on heart-rate recovery after exercise as a predictor of mortality (Oct. 28 issue),1 Cole et al. did not clearly define the “cessation” of exercise in their study, since there was a cool-down period that included exercise. Did they mean the cessation of exercise according to the Bruce protocol or the cessation of the cool-down period (which was at least two minutes long)? Obviously, this distinction makes a large difference in the interpretation of their data. I interpret “cessation” to mean the end of all exercise and the placement of patients in a resting position. It would also be helpful for the authors to let readers know whether the patients were seated or supine at the cessation of exercise.
1 ReferencesSammy Gammenthaler, M.D.
Sadler Clinic, Conroe, TX 773041
Cole CR ,Blackstone EH ,Pashkow FJ ,Snader CE ,Lauer MS . Heart-rate recovery immediately after exercise as a predictor of mortality. N Engl J Med 1999;341:1351-1357
Full Text | Web of Science | Medline
To the Editor:
Cole et al. reported that heart rate immediately after exercise is a strong predictor of all-cause mortality (adjusted relative risk, 2.0; 95 percent confidence interval, 1.5 to 2.7). In contrast, resting heart rate did not have any predictive power for mortality even when tested by univariable analysis (unadjusted relative risk, 0.9; 95 percent confidence interval, 0.8 to 1.0). The latter finding is surprising, since most leading epidemiologic studies have demonstrated that the resting heart rate is a powerful risk factor for cardiovascular and total mortality, irrespective of age.1-4 Moreover, in several studies, resting heart rate emerged as the traditional factor most strongly associated with the risk of death after adjustment for many possible confounders.1,3 Cole et al. hypothesized that the mechanism by which impaired heart-rate recovery confers an increased risk of death is a decrease in vagal activity. A similar mechanism has been suggested to explain the increase in risk associated with resting tachycardia.
4 ReferencesPaolo Palatini, M.D.
University of Padua, 35128 Padua, Italy1
Goldberg RJ ,Larson M ,Levy D . Factors associated with survival to 75 years of age in middle-aged men and women: the Framingham Study. Arch Intern Med 1996;156:505-509
CrossRef | Web of Science | Medline2
Gillum RF ,Makuc DM ,Feldman JJ . Pulse rate, coronary heart disease, and death: the NHANES I Epidemiologic Follow-up Study. Am Heart J 1991;121:172-177
CrossRef | Web of Science | Medline3
Palatini P . Need for a revision of the normal limits of resting heart rate. Hypertension 1999;33:622-625
Web of Science | Medline4
Palatini P ,Casiglia E ,Julius S ,Pessina AC . High heart rate: a risk factor for cardiovascular death in elderly men. Arch Intern Med 1999;159:585-592
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To the Editor:
Cole et al. reported that a small decrease in heart rate (≤12 beats per minute) during the first minute after graded exercise was a powerful predictor of overall mortality. Between 1967 and 1972, in the Paris Prospective Study I,1 6101 working men (42 to 53 years old) who were free of known cardiovascular disease and had no symptoms underwent a standardized submaximal-exercise test on a bicycle. Their mean (±SD) heart rate at the end of exercise was 167±16 beats per minute (96±9 percent of the predicted maximal heart rate). During 25 years of follow-up, there were 1635 deaths (27 percent of the subjects) from all causes. A low value for heart-rate recovery during the first minute after exercise was predictive of overall mortality when considered as a continuous variable (P< 0.02). When the value for heart-rate recovery dropped below 10 beats per minute (which corresponded in our study to the 10th percentile of its distribution) and after adjustment (by Cox analysis) was made for age, resting heart rate, heart-rate increase during exercise, duration of exercise, positivity of the exercise test (in 271 subjects), smoking status, and diabetes, a low value for heart-rate recovery remained associated with increased overall mortality (relative risk, 1.20; 95 percent confidence interval, 1.04 to 1.39; P<0.01). We also looked for a decrease in heart rate between the end of exercise and each minute between the second through the eighth minutes, and the results were nearly identical to those obtained during the first minute only. Moreover, adjustment for blood-pressure levels before and during exercise did not change the results.
Our results, obtained with roughly similar methods but in a subgroup of subjects very different from those described by Cole et al., extend their results to a broader population and are further evidence of the suspected role of decreased vagal activity2-4 as an independent predictor of the risk of premature death, a predictor that may be detectable in a routine exercise test.
4 ReferencesXavier Jouven, M.D.
Hôpital Boucicaut, 75015 Paris, FrancePierre Ducimetière, Ph.D.
INSERM Unité 258, 94807 Villejuif, France1
Filipovsky J ,Ducimetiere P ,Safar ME . Prognostic significance of exercise blood pressure and heart rate in middle-aged men. Hypertension 1992;20:333-339
Web of Science | Medline2
Lauer MS ,Okin PM ,Larson MG ,Evans JC ,Levy D . Impaired heart rate response to graded exercise: prognostic implications of chronotropic incompetence in the Framingham Heart Study. Circulation 1996;93:1520-1526
Web of Science | Medline3
La Rovere MT ,Bigger JT Jr ,Marcus FI ,Mortara A ,Schwartz PJ . Baroreflex sensitivity and heart-rate variability in prediction of total cardiac mortality after myocardial infarction. Lancet 1998;351:478-484
CrossRef | Web of Science | Medline4
Imai K ,Sato H ,Hori M , et al. Vagally mediated heart rate recovery after exercise is accelerated in athletes but blunted in patients with chronic heart failure. J Am Coll Cardiol 1994;24:1529-1535
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Author/Editor Response
The authors reply:
To the Editor: Gammenthaler asks exactly how heart-rate recovery was calculated. We took the difference between the heart rate at peak exercise and the heart rate one minute later, which was one minute after the beginning of the cool-down period. At that time, the patients were upright and were walking at a speed of 2.4 km (1.5 miles) per hour and a grade of 2.5 percent.
Palatini notes that in univariable analysis, resting heart rate was not associated with mortality, a finding that is at odds with the results of population-based studies. Although when considered by itself the resting heart rate was not predictive of risk, after adjustment for age and sex it was predictive (adjusted hazard ratio per increase of 1 SD [14 beats per minute], 1.29; 95 percent confidence interval, 1.13 to 1.48; P<0.001). After further adjustment for heart-rate recovery, however, the association was weakened (adjusted hazard ratio, 1.14; 95 percent confidence interval, 0.99 to 1.30; P=0.07); when heart rate during exercise was also considered, the association was eliminated (adjusted hazard ratio, 0.97; 95 percent confidence interval, 0.85 to 1.12; P=0.67). This is not surprising, since changes in heart rate during exercise and recovery may reflect underlying autonomic dysfunction more precisely than resting heart rate.
We are grateful to Jouven and Ducimetière for sharing their findings from the Paris Prospective Study I cohort. Their observation that heart-rate recovery was an independent predictor of mortality in a population very different from ours provides further evidence of the prognostic power of easily obtained measures of autonomic nervous system function recorded during routine exercise testing.
Michael S. Lauer, M.D.
Christopher R. Cole, M.D.
Cleveland Clinic Foundation, Cleveland, OH 44195- Citing Articles (2)
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