Cycle length dependence of human action potential duration in vivo. Effects of single extrastimuli, sudden sustained rate acceleration and deceleration, and different steady-state frequencies.

Abstract

Using a new method for long-term recording of monophasic action potentials from the human heart, we studied in 17 patients the effects on ventricular action potential duration (APD) of three clinically pertinent cycle length perturbations:(1) single extrastimuli, (2) abrupt sustained rate acceleration and deceleration, and (3) different steady-state cycle lengths. Results were: (a) APD after single extrastimuli at progressively longer cycle lengths were related to the extrastimulus cycle length with a biphasic electrical restitution curve which after an initial steep rise and a subsequent transient descent rose again more gradually to a plateau at cycle lengths above 800-1,000 ms. (b) After a sustained step decrease in cycle length, the first APD shortened abruptly while final steadystate adaptation required up to several minutes. The transition between the rapid and slow phase of APD change was characterized by a variable alternans of APD which correlated inversely with the preceding diastolic interval. (c) In the steady state, APD correlated linearly with cycle length, increasing an average of 23 ms per 100 ms cycle length increase (r = 0.995). The divergence between steady-state and non-steady-state APD, and the slowness of steady-state adaptation, are important factors to be considered in clinical electrophysiologic studies and in rate correction algorithms of APD or QT intervals, respectively.

Coupling of ventricular action potential duration and local strain patterns during reverse remodeling in responders and nonresponders to cardiac resynchronization therapy

“…This is based on original work by Franz et al showing that adaptation to rate change approximates an asymptote by 2 minutes for a wide range of cycle length perturbations. 17 This is also the case for patients with atrial fibrillation as we ourselves confirmed in a more recent study. 18 The 30-second LV UEG recordings were analyzed off-line using a custom software script within MATLAB (MathWorks, Massachusetts, USA) to derive the ARI.…”

Longitudinal changes in QT interval variability and rate adaptation in pregnancies with normal and abnormal uterine perfusion

“…16 The latter was proposed to be modulated by catecholamines, where sympathetic Initial measurement (weeks) activation results in an acceleration of the rate-adaptation through stimulation of Na + -K + pumps. 17 The shortened QT/HR hysteresis lag observed during pregnancy might therefore be caused by increased sympathetic outflow to the ventricles that normalized within 3 days postpartum.…”

Control of rapid heart rate changes for electrocardiographic analysis: implications for thorough QT studies

“…The initial adaptation (around 50%) of QT change occurs the order of a 50 to 60 s time frame, the terminal adaptation lasting above 2 min. 4,15,18 Less is known about QT hysteresis during physiologic HR fluctuation not associated with atrial pacing or acute exercise. In a recent study, Pueyo et al showed that the hysteresis phenomenon was different among subjects and was also influenced by amiodarone.…”

“…3 The main electrophysiologic property of ventricular repolarization is inversely related to heart rate (HR). 4,5 To compare QT intervals within and between subjects, numerous solutions have been proposed to take this phenomenon into account. The so-called "universal-correction" formulae have been shown to over-or undercorrect the QT interval potentially when HR changes.…”

“…Following an abrupt change in HR, the QT adaptation is not immediate but is achieved within a 3-min time frame, although most QT adaptations occur over the first minute. 4,14,15 From a theoretical point of view, QT interval measurement performed just after a sudden HR change would lead to a potential error in the estimation of QT duration. Thus, the rate correction of QT interval duration based on the single preceding RR interval may introduce a potential confounding factor whatever the strategy used to correct QT interval.…”