Hysteresis in the Human RR‐QT Relationship During Exercise and Recovery

Sarma, J. S. M.; Venkataraman, Shreyas; Samant, Dinesh R.; Gadgil, Uday

doi:10.1111/j.1540-8159.1987.tb04510.x

Cited by 75 publications

(52 citation statements)

References 13 publications

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“…It is well recognized that there is a physiological delay in the adaptation of repolarization durations to changing heart rates. 19 It has been shown that the properties and balance of the repolarizing inward sodium and outward potassium channels of ventricular myocardial cell membranes and the metabolic processes surrounding them play an important role in this process. 20 Acute ischemia results in an acidosis-and anoxia-induced depression of membrane excitability and delayed recovery of excitability.…”

Section: Discussionmentioning

confidence: 99%

Impact of Infarct-Related Artery Flow on QT Dynamicity in Patients Undergoing Direct Percutaneous Coronary Intervention for Acute Myocardial Infarction

Bonnemeier

Wiegand²,

Bode³

et al. 2003

Circulation

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Background-Complete coronary artery reperfusion in acute myocardial infarction (AMI) has been shown to significantly improve survival. Electrical stability may be the decisive mechanism for this beneficial effect. Because electrical stability is largely dependent on ventricular repolarization, we sought to determine the impact of a modern reperfusion strategy (ie, direct percutaneous coronary intervention [PCI]) on QT dynamicity in AMI and examined its association with infarct-related artery flow. Methods and Results-We prospectively investigated QT dynamicity in 128 patients undergoing direct PCI for a first AMI. Slopes and correlation coefficients of the linear QT/RR regression were determined in the time interval before reperfusion, within the initial hour after reperfusion, and within the remaining recording period from Holter ECG recordings, which were initiated on admission. Subgroup analysis based on TIMI 3 (nϭ100) and TIMI 2 (nϭ28) flow after PCI revealed no significant differences in QT/RR slope before PCI (0.145Ϯ0.12 versus 0.160Ϯ0.19, PϭNS). After PCI, QT/RR slopes increased only in the TIMI 2 subgroup (PϽ0.05). In TIMI 2 patients, QT/RR slopes were significantly steeper in the hour after PCI and in the remaining recording period, respectively (0.

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Section: Discussionmentioning

confidence: 99%

Impact of Infarct-Related Artery Flow on QT Dynamicity in Patients Undergoing Direct Percutaneous Coronary Intervention for Acute Myocardial Infarction

Bonnemeier

Wiegand²,

Bode³

et al. 2003

Circulation

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“…Furthermore, ECG quality during the recovery period is better than during exercise. Finally, hysteresis in the QT-RR relationship between exercise and recovery has been reported and could therefore affect the findings (47). We have recently shown that the hysteresis phenomenon is mediated by the different autonomic balance noted in exercise and recovery (25).…”

Section: Discussionmentioning

confidence: 99%

Autonomic effects on QT-RR interval dynamics after exercise

Sundaram¹,

Carnethon²,

Polito³

et al. 2008

American Journal of Physiology-Heart and Circulatory Physiology

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This study was designed to assess autonomic effects on the QT interval during recovery from exercise. Exercise is associated with an acute increased risk of sudden cardiac death. Evidence of impaired parasympathetic activity, such as low heart rate variability and heart rate recovery, and an increased QT interval are also associated with increased mortality. However, there is no clear pathophysiological link among these findings. Bicycle exercise testing was performed serially in 33 healthy volunteers (19 men; ages, 54 Ϯ 7 yr) under four conditions: 1) baseline, 2) ␤-adrenergic blockade-intravenous propranolol (0.2 mg/kg) administered during exercise, 3) parasympathetic blockade-intravenous atropine (0.04 mg/kg) administered during exercise, and 4) double blockade with propranolol and atropine. ECGs were obtained every minute in recovery for 10 min and then at the 15th and 20th min, from which the QT and RR intervals were measured. Linear regression analyses were used to assess the individual QT-RR relationships for each subject for each condition. Relative to baseline, the QT-RR relationship with parasympathetic blockade was shifted to the left and had a steeper slope. In contrast, the QT-RR relationship with ␤-adrenergic blockade was shifted to the right and had a less steep slope. The baseline and double-blockade QT-RR relationships were in the middle and essentially superimposable. There was a negative relationship between QT-RR slope and heart rate or RR interval recoveries, but it was significant only for the 1-and 2-min RR interval recoveries with low R 2 values of 0.124 and 0.114. The main parasympathetic effect in the postexercise recovery period is to counteract the sympathetically mediated QT prolongation. These data support the concept that parasympathetic tone may provide a natural antiarrhythmic effect during this time.parasympathetic; heart rate recovery; QT interval THE PATHOPHYSIOLOGY of sudden cardiac death is not completely understood. A variety of epidemiologic findings has provided key insights into the potential roles of ventricular repolarization, autonomic tone, and exercise. Although exercise has overall salutary effects, it has been shown that the risk of sudden death is increased dramatically during and immediately after exercise (3, 36) compared with sedentary periods. Although there are several possible mechanisms for this marked increased risk of sudden cardiac death, including the induction of myocardial ischemia, it may be related to the acute changes in autonomic tone that accompany exercise. The prognostic significance of abnormalities of autonomic tone has been established in multiple studies that have evaluated autonomic control of the heart rate predominantly at rest or during daily activities. These studies have linked diminished parasympathetic control with increased mortality (8,21,24,26,39,41). Finally, population studies have linked the QT interval on a 12-lead electrocardiogram (ECG) with an increased risk of ventricular arrhythmias and sudden death both in patients wit...

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“…In the light of a possibly increased arrhythmia risk during recovery, we hypothesized that DOR might be augmented during the recovery phase, with respect to actual exercise. Here we present the preliminary results of a study in which we sought to further establish the concept of electrophysiological hysteresis [2] in the setting of maximal exercise tests.…”

Section: Introductionmentioning

confidence: 99%