Circadian changes in heart rate turbulence parameters

HRT assessment reviewed: a systematic review of heart rate turbulence methodology

Heart rate turbulence (HRT) is a biphasic reaction to a ventricular premature contraction (VPC) mainly mediated by the baroreflex. It can be used for risk stratification in different disease patterns. Despite existing standards there is a lot of variation in terms of measuring and calculating HRT, which complicates research and application.

OBJECTIVE

This systematic review outlines and evaluates the methodological spectrum of HRT research, especially filtering criteria, parameter calculation and thresholds.

APPROACH

The analysis includes all research papers written in English that have been published before 12.10.2018, are listed on PubMed and involve calculation of HRT parameter values.

MAIN RESULTS

HRT assessment is still being performed in various ways and important specifications of the methodology are not given in many articles. Nevertheless, some suggestions regarding HRT methodology can be made: a normalised turbulence slope should be used to uncouple the parameter from heart rate and frequency of extrasystoles. Filtering criteria as formerly reviewed in the guidelines should be met and mentioned. The minimal number of VPC snippets (VPCSs) as well as new cut-off values for different risks need to be further evaluated. Most importantly, the exact and complete methodology must be described to ensure reproducibility and comparability.

SIGNIFICANCE

Methodical variation hinders comparability of research and medical application. Our continuing questions help to further standardise the measurement and calculation of HRT and increase its value for medical risk stratification.

Assessment of heart rate turbulence in hypertensive patients: rationale, perspectives, and insight into autonomic nervous system dysfunction

Background:

Heart rhythm turbulence is classically impaired in patients with previous myocardial infarction and congestive heart failure and is poorly investigated in patients with essential hypertension.

Objective:

To evaluate heart rhythm turbulence parameters (turbulence onset, (TO); turbulence slope, (TS) in a series of hypertensive patients while gaining insight into autonomic nervous system dysfunction.

Setting and Design:

University hospital, cross-sectional monocentric study.

Materials and Methods:

Heart rhythm turbulence was assessed in 50 hypertensive (case group) and 40 normotensive patients (control group).

Results:

TO and TS were found independently correlated with hypertension. The mean TO was found at -1.64% ± 2.85% in the normotensive patients compared to 1.21% ± 1.95% in the hypertensive patients; the mean TS was found at 4.29 ± 3.18 ms/RR in the normotensive patients compared to 2.27 ± 0.93 ms/RR in the hypertensive patients. Hypertension has a predictive value on heart rhythm turbulence impairment (OR 4.99, 95% CI 1.28-19.41, P = 0.02). Insights into the role of autonomic nervous system dysfunction for the management of hypertensive patients and prevention of malignant ventricular arrhythmia are presented and discussed with regard to heart rhythm turbulence.

Conclusion:

Essential hypertension is correlated with blunted heart rhythm turbulence parameters.

Circadian Patterns of Heart Rate Turbulence, Heart Rate Variability and Their Relationship

Background

Heart rate variability (HRV) is an established tool for studying cardiac autonomic activity over time, while heart rate turbulence (HRT) is a recent method used to assess autonomic dysfunction. However, there are different autonomic tones at different times of a day. This study aimed to examine the effect of circadian change of autonomic tone on heart rate turbulence and variability, and determine any relationship between them based on circadian variations.

Methods

Twenty-four-hour Holter recordings from 35 subjects with structurally normal heart were done, and HRV and HRT parameters of turbulence onset (TO) and turbulence slope (TS) were calculated. The 24-hour circadian patterns of these parameters and correlation analysis between them were performed.

Results

There were conspicuous diurnal oscillations in TS and HRV parameters, with less prominent variation in TO. TS and high frequency power (HF) shared the similar oscillation patterns in a day. Comparing HRT and HRV based on circadian variation, TS showed positive correlations with HF and low frequency power (LF) to a reasonable degree, while there was an inverse correlation between TS and LF/HF.

Conclusions

Circadian change of TS values throughout the day is more prominent than TO. It also presents as an autonomic activity more than TO. The relationships between HRV and HRT persist independently on the time of a day.

Insulin resistance and circadian rhythm of cardiac autonomic modulation

Background

Insulin resistance (IR) has been associated with cardiovascular diseases (CVD). Heart rate variability (HRV), an index of cardiac autonomic modulation (CAM), is also associated with CVD mortality and CVD morbidity. Currently, there are limited data about the impairment of IR on the circadian pattern of CAM. Therefore, we conducted this investigation to exam the association between IR and the circadian oscillations of CAM in a community-dwelling middle-aged sample.

Method

Homeostasis models of IR (HOMA-IR), insulin, and glucose were used to assess IR. CAM was measured by HRV analysis from a 24-hour electrocardiogram. Two stage modeling was used in the analysis. In stage one, for each individual we fit a cosine periodic model based on the 48 segments of HRV data. We obtained three individual-level cosine parameters that quantity the circadian pattern: mean (M), measures the overall average of a HRV index; amplitude (Â), measures the amplitude of the oscillation of a HRV index; and acrophase time (θ), measures the timing of the highest oscillation. At the second stage, we used a random-effects-meta-analysis to summarize the effects of IR variables on the three circadian parameters of HRV indices obtained in stage one of the analysis.

Results

In persons without type diabetes, the multivariate adjusted β (SE) of log HOMA-IR and M variable for HRV were -0.251 (0.093), -0.245 (0.078), -0.19 (0.06), -4.89 (1.76), -3.35 (1.31), and 2.14 (0.995), for log HF, log LF, log VLF, SDNN, RMSSD and HR, respectively (all P < 0.05). None of the IR variables were significantly associated with  or θ of the HRV indices. However, in eight type 2 diabetics, the magnitude of effect due to higher HOMA-IR on M, Â, and θ are much larger.

Conclusion

Elevated IR, among non-diabetics significantly impairs the overall mean levels of CAM. However, the  or θ of CAM were not significantly affected by IR, suggesting that the circadian mechanisms of CAM are not impaired. However, among persons with type 2 diabetes, a group clinically has more severe form of IR, the adverse effects of increased IR on all three HRV circadian parameters are much larger.

Heart rate turbulence: standards of measurement, physiological interpretation, and clinical use: International Society for Holter and Noninvasive Electrophysiology Consensus

This consensus statement has been compiled on behalf of the International Society for Holter and Noninvasive Electrophysiology. It reviews the topic of heart rate turbulence (HRT) and concentrates on technologies for measurement, physiologic background and interpretation, and clinical use of HRT. It also lists suggestions for future research. The phenomenon of HRT refers to sinus rhythm cycle-length perturbations after isolated premature ventricular complexes. The physiologic pattern of HRT consists of brief heart rate acceleration (quantified by the so-called turbulence onset) followed by more gradual heart rate deceleration (quantified by the so-called turbulence slope) before the rate returns to a pre-ectopic level. Available physiologic investigations confirm that the initial heart rate acceleration is triggered by transient vagal inhibition in response to the missed baroreflex afferent input caused by hemodynamically inefficient ventricular contraction. A sympathetically mediated overshoot of arterial pressure is responsible for the subsequent heart rate deceleration through vagal recruitment. Hence, the HRT pattern is blunted in patients with reduced baroreflex. The HRT pattern is influenced by a number of factors, provocations, treatments, and pathologies reviewed in this consensus. As HRT measurement provides an indirect assessment of baroreflex, it is useful in those clinical situations that benefit from baroreflex evaluation. The HRT evaluation has thus been found appropriate in risk stratification after acute myocardial infarction, risk prediction, and monitoring of disease progression in heart failure, as well as in several other pathologies.

Heart rate turbulence denoising using support vector machines

Heart rate turbulence (HRT) is a transient acceleration and subsequent deceleration of the heart rate after a premature ventricular complex (PVC), and it has been shown to be a strong risk stratification criterion in patients with cardiac disease. In order to reduce the noise level of the HRT signal, conventional measurements of HRT use a patient-averaged template of post-PVC tachogram (PPT), hence providing with long-term HRT indexes. We hypothesize that the reduction of the noise level at each isolated PPT, using signal processing techniques, will allow us to estimate short-term HRT indexes. Accordingly, its application could be extended to patients with reduced number of available PPT. In this paper, several HRT denoising procedures are proposed and tested, with special attention to support vector machine (SVM) estimation, as this is a robust algorithm that allows us to deal with few available time samples in the PPT. Pacing-stimulated HRT during electrophysiological study are used as a low-noise gold standard. Measurements in a 24-h Holter patient database reveal a significant reduction in the bias and the variance of HRT measurements. We conclude that SVM denoising yields short-term HRT measurements and improves the signal-to-noise level of long-term HRT measurements.

Demonstration of circadian rhythm in heart rate turbulence using novel application of correlator functions

BACKGROUND

Demonstration of a circadian rhythm in two parameters of heart rate turbulence--turbulence onset (TO) and turbulence slope (TS)--has been difficult.

OBJECTIVE

The aim of this study was to devise a new method for detecting circadian rhythm in noisy data and to apply it to selected Holter recordings from two postmyocardial infarction databases: Cardiac Arrhythmia Suppression Trial (CAST, n = 684) and Innovative Stratification of Arrhythmic Risk (ISAR, n = 327).

METHODS

For each patient, TS and TO were calculated for each hour with >4 ventricular premature contractions (VPCs). An autocorrelation function Corr(Deltat) = <TS(t) TS(t + Deltat)> then was calculated and averaged over all patients. Positive Corr(Deltat) indicates that TS at a given hour and Deltat hours later are similar. TO was treated likewise. Simulations and mathematical analysis showed that a circadian rhythm required Corr(Deltat) to have a U-shape consisting of positive values near Deltat = 0 and 23 and negative values for intermediate Deltat. Significant deviation of Corr(Deltat) from the correlator function of pure noise was evaluated as a Chi-square value.

RESULTS

Circadian patterns were not apparent in hourly averages of TS and TO plotted against clock time, which had large error bars. However, their correlator functions produced Chi-square values of approximately 10 in CAST (both P <.0001) and approximately 3 in ISAR (both P <.0001), indicating the presence of circadian rhythmicity.

CONCLUSION

Correlator functions may be a powerful tool for detecting the presence of circadian rhythms in noisy data, even with recordings limited to 24 hours.

Risk stratification for arrhythmic death after myocardial infarction: Current perspective and future direction

The number of patients eligible for implantable cardioverter defibrillator implantation is large and growing. Results of the Multicenter Automatic Defibrillator Implantation Trial-II, Comparison of Medical Therapy, Pacing, and Defibrillation in Heart Failure trial, and Sudden Cardiac Death in Heart Failure Trial will have a major impact on health care expenditure and economics in all countries. Therefore, one of the most important challenges in today's cardiology is finding more specific and accurate risk stratification strategies (rather than simply ejection fraction) for primary prevention of sudden cardiac death in patients who have suffered myocardial infarction. We hereby reviewed the existing data on potential risk stratifiers and assessed their impact on every day decision making and patient selection for ICD implantation.

Circadian periodicity of heart rate variability in hospitalized angor patients

The relationship between unstable angor (angina) and circadian periodicity of heart rate variability (HRV) was explored in a group of patients hospitalized in a coronary care unit (CCU). Patients were classified as normal (whose symptoms had non-cardiovascular origin, n=8), moderate angor (n=13) and severe angor (n=11). A fourth group of ambulatory healthy volunteers (n=12) was included. Individual 24 h Holter records were analyzed, mean RR and standard deviation of RR (SDNN) being obtained from 1 h-length windows. For frequency domain analysis, 5 min-length windows were employed. The spectral components analyzed were total power (spectral power between 0.01 and 0.5 Hz), low frequency power (LF: power between 0.04 and 0.15 Hz), and high frequency power (HF: power between 0.15 and 0.4 Hz). In addition, LF to HF areas ratio (L/H) was computed. Mesor, amplitude and acrophase for every 24 h rhythm were calculated by cosinor analysis. As compared to ambulatory controls, admission to the CCU diminished amplitude and phase-delayed the circadian oscillation of most HRV parameters, except for SDNN. Moderate angor patients showed decreased amplitude of RR and L/H and augmented amplitude of SDNN when compared to normal hospitalized subjects. A phase delay of about 1.5 h for RR intervals and a phase advance of 3.5-6 h for LFA and SDNN were found in the moderate angor group when compared to normal. Amplitude of 24 h variation of total power decreased in severely angor patients and the circadian oscillation of HF (an indicator of vagal control on the heart) became free running. A phase delay of 2.5 h in SDNN acrophase was found in severely affected patients when compared to moderate. The results indicate that severity of unstable angor correlates with desynchronization of parasympathetic control of heart rate.