What is chronotropic

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If you find something abusive or that does not comply with our terms or guidelines please flag it as inappropriate. Advanced search. Skip to main content Thank you for visiting nature. Download PDF. Abstract POSITIVE chronotropic effects induced by increased concentration of calcium ions have been reported by a number of authors in isolated 1,2 and non-isolated 3—5 mammalian hearts.

References 1 Feinberg, H. Google Scholar 4 Hoff, H. Google Scholar 7 Weidmann, S. Google Scholar 13 Bertler, A. View author publications. Rights and permissions Reprints and Permissions. Copy to clipboard. Kohlhardt , D. Voth , K. TRIP on Chronotropic. Ongoing Trials on Chronotropic at Clinical Trials.

Trial results on Chronotropic. Clinical Trials on Chronotropic at Google. FDA on Chronotropic. CDC on Chronotropic. Books on Chronotropic. Chronotropic in the news. Be alerted to news on Chronotropic. News trends on Chronotropic. Blogs on Chronotropic. Definitions of Chronotropic. Patient resources on Chronotropic. Discussion groups on Chronotropic. Patient Handouts on Chronotropic. Directions to Hospitals Treating Chronotropic.

Risk calculators and risk factors for Chronotropic. Symptoms of Chronotropic. Diagnostic studies for Chronotropic. Treatment of Chronotropic. CME Programs on Chronotropic. In general, RR intervals during recovery are non-stationary time series, which trend will have influences on heart rate variability indexes. Thus, we employed heart rate variability indexes calculated by frequency-domain methods. Tulppo et al.

Wilcoxon matched pairs signed ranks test was used to analyse heart rate variability indexes within each group. Of patients, 72 were diagnosed as having CI and the remaining as not having CI. The two groups were well matched with respect to baseline characteristics, except that the current smoking was more common in patients with CI Table 1.

Exercise capacity and heart rate during exercise testing were lower in patients with CI than in those without CI. In patients with CI, CI, chronotropic incompetence. All indexes of heart rate variability before exercise were similar in patients with CI and without CI Figure 1. After exercise, LF component and HF component decreased in both groups. These results were not altered even in a subgroup analysis in which the different incidence of smoking was taken into account Figure 3.

Changes in low-frequency component, high-frequency component, and coefficient of component variance from at rest to after exercise in patients with and without chronotropic incompetence.

Percentage changes in low-frequency component, high-frequency component, and coefficient of component variance from at rest to after exercise in patients with and without chronotropic incompetence. Percentage changes in low-frequency component, high-frequency component, and coefficient of component variance from at rest to after exercise in subgroups of smoker and non-smoker. The vagal activity is recognized to be a major contributor to HF component.

In the study using treadmill exercise and autonomic blockades, early contributor to heart rate recovery after peak exercise was sympathetic withdrawal, with vagal reactivation behaving later. In the present study, however, heart rate after exercise was lower in patients with CI despite an increased sympathetic activation.

It is tempting, therefore, to consider that there may have been a pathological condition in which sympathetic activation was not well translated into the functional response, i. One of the pathophysiological conditions may be post-synaptic desensitization of the beta-adrenergic receptor pathway in the sinoatrial node. Frequent activation of sympathetic nerves will cause the down-regulation of beta-adrenergic receptors, leading to post-synaptic desensitization.

Further study will be needed to estimate the post-synaptic sensitivity of the beta-adrenergic receptor in relation to CI. In the present study, cigarette smoking was more common in patients with CI.

Lauer and co-workers 33 , 34 reported a similar result that CI was associated with smoking in a healthy, population-based cohort.

The mechanism linking smoking to CI remains unclear, but there may also underlie the post-synaptic desensitization of the beta-adrenergic receptor pathway. Cryer et al. Furthermore, smoking cessation has been reported to be associated with lower heart rate and improved autonomic function as assessed by heart rate variability in volunteer subjects.

However, this speculation seems to be less tenable with our results demonstrating that similar autonomic dysfunction was observed in patients with CI irrespective of smoking. Compensatory vagal hyperactivity has been proposed to be another possible physiological mechanism of CI. In addition, CI has been reported to be associated with left ventricular dilation and hypertrophy.

Sick sinus syndrome is a possible mechanism of CI, but none of our patients had clinical evidence of sinus node dysfunction, although electrophysiological examination of sinus node function was not performed in our patients. The prevalence of CI was higher in the present study than in previous studies. The present study did not include a stress test using pharmacological autonomic nerve blockades.

Our data suggest that the main cause of CI in patients without structural heart disease is pathophysiological conditions in which sympathetic activation is not well translated into heart rate increase.

Further study will be needed to determine the post-synaptic sensitivity of the beta-adrenergic receptor pathway in relation to CI. Google Scholar. Google Preview. Oxford University Press is a department of the University of Oxford. It furthers the University's objective of excellence in research, scholarship, and education by publishing worldwide.

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