Heart rate turbulence as risk-predictor after myocardial infarction

Comparability of Heart Rate Turbulence Methodology: 15 Intervals Suffice to Calculate Turbulence Slope – A Methodological Analysis Using PhysioNet Data of 1074 Patients

Heart rate turbulence (HRT) is a characteristic heart rate pattern triggered by a ventricular premature contraction (VPC). It can be used to assess autonomic function and health risk for various conditions, e.g., coronary artery disease or cardiomyopathy. While comparability is essential for scientific analysis, especially for research focusing on clinical application, the methodology of HRT still varies widely in the literature. Particularly, the ECG measurement and parameter calculation of HRT differs, including the calculation of turbulence slope (TS). In this article, we focus on common variations in the number of intervals after the VPC that are used to calculate TS (#TSRR) posing two questions: 1) Does a change in #TSRR introduce noticeable changes in HRT parameter values and classification? and 2) Do larger values of turbulence timing (TT) enabled by a larger #TSRR still represent distinct HRT? We compiled a free-access data set of 1,080 annotated long-term ECGs provided by Physionet. HRT parameter values and risk classes were determined both with #TSRR 15 and 20. A standard local tachogram was created by averaging the tachograms of only the files with the best heart rate variability values. The shape of this standard VPC sequence was compared to all VPC sequences grouped by their TT value using dynamic time warping (DTW) in order to identify HRT shapes. When calculated with different #TSRR, our results show only a little difference between the number of files with enough valid VPC sequences to calculate HRT (<1%) and files with different risk classes (5 and 6% for HRT0-2 and HRTA-C, respectively). In the DTW analysis, the difference between averaged sequences with a specific TT and the standard sequence increased with increasing TT. Our analysis suggests that HRT occurs in the early intervals after the VPC and TS calculated from late intervals reflects common heart rate variability rather than a distinct response to the VPC. Even though the differences in classification are marginal, this can lead to problems in clinical application and scientific research. Therefore, we recommend uniformly using #TSRR 15 in HRT analysis.

Heart Rate Variability May Predict the Severity of Appendicitis: A Cross-Sectional Study

OBJECTIVE

To evaluate the role of heart rate variability (HRV) in predicting pre-operative severity of appendicitis.

METHODS

In this cross-sectional study, 171 cases of acute appendicitis who underwent appendectomy were enrolled. Pre-anesthetic pulse rate of included patients were documented while the severity of appendicitis was determined by intra-operative evidences reported by two independent surgeons. Demographic characteristics, laboratory variables, and Alvarado criteria were recorded.

RESULTS

The mean age of patients was 28.75±4.21 years; 54% were men. HRV negatively associated the severity of appendix inflammation. A positive association was found between HRV and omental wrapping and Alvarado score (p<0.01). The receiver operating characteristic (ROC) curve analysis demonstrated that HRV could differentiate simple and complicated appendicitis with a sensitivity of 78.5% and specificity of 97.2%.

CONCLUSION

The present findings revealed that HRV may predict the pre-operative severity of appendicitis and help differentiate simple and complicated appendicitis.

Evaluation of cardiovascular autonomic dysfunction according to heart rate turbulence and variability in patients with relapsing remitting multiple sclerosis

Background/aim

Multiple sclerosis (MS) is an autoimmune disease characterized by neurodegeneration or demyelination; the relapsing–remitting phase of MS is characterized by acute exacerbation of disease activity. The most commonly used noninvasive approach to assess autonomic function is the determination of heart rate turbulence (HRT) and heart rate variability (HRV). The aim of this study was to evaluate the presence of cardiovascular autonomic dysfunction using HRT and HRV parameters determined via 24-h Holter ECG monitoring in patients with relapsing–remitting MS without known heart disease.

Materials and methods

The study included 26 patients diagnosed with relapsing–remitting MS and 22 age- and sex-matched healthy controls. HRT and HRV parameters were analyzed via 24-h Holter ECG monitoring. Magnetic resonance imaging findings were reevaluated to identify any demyelinating lesions in the brain stem.

Results

The HRV parameters of SDNNI (mean of the standard deviations of all normal sinus RR intervals in all 5-min segments), rMSSD (root–mean–square successive difference), and sNN50 (percentage of successive normal sinus RR intervals >50 ms) were significantly lower in the MS group than in the control group (P < 0.05).

Conclusion

This study revealed that the patients with MS had reduced HRV; this was demonstrated by dysfunction with regard to parasympathetic and sympathetic parameters in HRV analysis.

Obstructive Sleep Apnea as a Predictor of Abnormal Heart Rate Turbulence

Obstructive sleep apnea (OSA) causes dysfunction of the autonomic nervous system, but the exact mechanism has not been fully understood. The aim of this study was to analyse the relationship between the incidence and severity of OSA and heart rate turbulence (HRT). Seventy one patients with clinical suspicion of OSA were qualified to participate in the study. All participants took part in a survey and were subjected to laboratory tests, 24-hour electrocardiogram (ECG) Holter monitoring with HRT analysis and polysomnography. The group with OSA manifested significantly higher turbulence onset (TO) and lower turbulence slope (TS) as compared to the group without OSA. Older age, diabetes, hypertension and higher apnea/hypopnea index (AHI) were found to be independent risk factors for increased TO, whereas older age, higher body mass index (BMI), higher blood glucose levels, hypertension and higher AHI were independent risk factors for TS reduction. The AHI ≥65 criterion indicates abnormal HRT in patients with OSA with 94.9% sensitivity and 50.0% specificity, which gives a prediction accuracy of 85.7%. In summary, OSA should be considered as a predictor of abnormal HRT.

Exposure to antenatal corticosteroids and reduced respiratory sinus arrhythmia in adult survivors of extremely low birth weight

Purpose/aim: Antenatal corticosteroid (ACS) therapy has dramatically increased survival rates among extremely low birth weight (ELBW) infants. However, the long-term effects of ACS on autonomic nervous system function have not been explored. Using the world's oldest longitudinally followed cohort of ELBW infants we compared respiratory sinus arrhythmia (RSA) among ELBW survivors whose mothers received ACS (ELBW-S), those who did not (ELBW-NS) and normal birth weight (NBW) controls in their 20 and 30 s. Methods: Resting electrocardiogram (ECG) was recorded from ELBW-S (n = 28), ELBW-NS (n = 36), and matched NBW controls (n = 79) at 22-26 and 29-36 years. Resting RSA was compared across groups via analyses of covariance (ANCOVA), adjusting for sex, medication use, postnatal steroid exposure and the presence of chronic health conditions. RSA was also compared across assessments for each group. Results: At 29-36 years, resting RSA in ELBW-S was significantly lower than in NBW controls. RSA in the ELBW-NS group was intermediate between ELBW-S and NBW groups. Although the ELBW-S group also showed nominally reduced RSA compared to NBW controls at the 22-26-year visit, this difference was not statistically significant. Conclusions: ELBW survivors exposed to ACS had lower RSA than NBW controls during their 30 s, suggestive of a decline in parasympathetic input to heart. ELBW survivors who received ACS may be particularly vulnerable to cardiovascular problems in later life.

Heart Rate Turbulence Is a Powerful Predictor of Cardiac Death and Ventricular Arrhythmias in Postmyocardial Infarction and Heart Failure Patients: A Systematic Review and Meta-Analysis

BACKGROUND

Heart rate turbulence (HRT) has been proposed as a candidate marker of altered autonomic tone, and some studies showed its prognostic value for both cardiac death (CD) and sudden death. Nevertheless, HRT is not currently used in the clinical practice.

METHODS AND RESULTS

We performed a systematic review and meta-analysis of the predictive value of HRT for the end points of total mortality, CD, and fatal and nonfatal ventricular arrhythmias in postacute myocardial infarction and heart failure patients. MEDLINE and The Cochrane Library databases were systematically searched to identify studies, which analyzed the predictive value of abnormal HRT for the defined end points. Twenty studies (25 cohorts: 12 832 patients) were identified by the systematic review, and 15 studies (20 cohorts: 11 499 patients) were included in the meta-analyses. Abnormal HRT was a predictive marker for all the end points in heart failure patients and more markedly in postacute myocardial infarction patients, where 9 out of the 10 cohorts had an ejection fraction >30%. In postacute myocardial infarction patients, HRT had pooled risk ratios of 3.53 (95% confidence interval [CI], 2.54-4.90), 4.82 (95% CI, 3.12-7.45), and 4.48 (95% CI, 3.04-6.60), and positive likelihood ratios of 3.5 (95% CI, 2.6-4.8), 4.1 (95% CI, 3.0-5.7), and 2.7 (95% CI, 2.2-3.3) for total mortality, CD, and arrhythmic events, respectively. The combination of abnormal HRT and T-wave alternans (5 cohorts: 1516 patients) increased the predictive power for CD and arrhythmic events.

CONCLUSIONS

HRT is a powerful predictor of both CD and arrhythmic events, particularly in postacute myocardial infarction patients with ejection fraction >30%. HRT power increases in combination with T-wave alternans analysis.

Association of Heart Rate Turbulence With Arrhythmia Susceptibility and Heart Disease in Mice

INTRODUCTION

Recent studies have demonstrated the feasibility of measuring heart rate turbulence (HRT) as a marker of baroreflex function in healthy mice. The aim of this investigation was to measure HRT in a mouse model with induced structural heart defects and to determine if there were threshold values of HRT for inducible ventricular tachycardias (VTs).

METHODS AND RESULTS

HRT was measured during electrophysiological investigations 2 weeks after transverse aortic constriction (TAC, n = 13) or myocardial cryoinfarction (MCI, n = 14). Sham-operated mice served as controls (n = 8 for TAC controls and n = 9 for MCI controls). Mice with heart disease lacked an early acceleration (turbulence onset [TO]) in heart rate after extrastimulus pacing (heart disease: 0.39% [0.19%-0.59%] vs. all controls: -0.04% [-0.25-0.19%]; P < 0.01). At a cutoff value of >0.25%, TO could be used to classify mice with induced heart disease with a sensitivity of 64.0% and specificity of 88.2% (P < 0.01) but did not identify mice at higher risk of induced VTs. Animals that were susceptible to VTs (n = 8) had lower values for turbulence slope (TS) compared with noninducible mice (6.2 milliseconds/beat [3.1-9.5 milliseconds/beat] vs. 10.1 milliseconds/beat [7.2-14.2 milliseconds/beat]; P = 0.03). TS <7.8 milliseconds/beat identified mice with inducible VTs with a sensitivity of 75.0% and specificity of 75.8% (P = 0.02).

CONCLUSION

Measurement of HRT is feasible in mouse models with induced structural heart disease. More abnormal values for TO were found in the presence of structural heart disease but did not predict susceptibility to VTs. Decreased TS was associated with VTs induced by programmed stimulation.

Prognostic value of heart rate turbulence for risk assessment in patients with unstable angina and non-ST elevation myocardial infarction

Background

We sought to examine the prognostic value of heart rate turbulence derived from electrocardiographic recordings initiated in the emergency department for patients with non-ST elevation myocardial infarction (NSTEMI) or unstable angina.

Methods

Twenty-four-hour Holter recordings were started in patients with cardiac symptoms approximately 45 minutes after arrival in the emergency department. Patients subsequently diagnosed with NSTEMI or unstable angina who had recordings with ≥18 hours of sinus rhythm and sufficient data to compute Thrombolysis In Myocardial Infarction (TIMI) risk scores were chosen for analysis (n = 166). Endpoints were emergent re-entry to the cardiac emergency department and/or death at 30 days and one year.

Results

In Cox regression models, heart rate turbulence and TIMI risk scores together were significant predictors of 30-day (model chi square 13.200, P = 0.001, C-statistic 0.725) and one-year (model chi square 31.160, P < 0.001, C-statistic 0.695) endpoints, outperforming either measure alone.

Conclusion

Measurement of heart rate turbulence, initiated upon arrival at the emergency department, may provide additional incremental value in the risk assessment for patients with NSTEMI or unstable angina.