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

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.

Alterations in heart rate variability are associated with abnormal myocardial perfusion

BACKGROUND

Abnormalities in the autonomic nervous system may occur in ischemic heart disease, but the mechanisms by which they are linked are not fully defined. The risk of cardiac events is increased during morning hours. Studying the contributions of autonomic mechanisms may yield insights into risk stratification and treatment. We hypothesize that autonomic dysfunction, measured by decreased heart rate variability (HRV), associates with abnormal stress myocardial perfusion imaging (MPI).

METHODS

We performed a cross-sectional study of the association between abnormal myocardial stress perfusion with HRV using 276 middle-aged veteran twins without known ischemic heart disease. The primary independent variable was cardiac autonomic regulation measured with 24-hour electrocardiogram (ECG) monitoring, using linear and non-linear (multipole density, or Dyx) HRV metrics. The primary outcome was abnormal perfusion (>5% affected myocardium) during adenosine stress on [13N]-ammonia myocardial perfusion imaging with positron emission tomography.

RESULTS

The mean (SD) age was 53 (3) years and 55 (20%) had abnormal perfusion. HRV (by Dyx) was reduced during morning hours in subjects with abnormal perfusion. At 7 AM, each standard deviation (SD) decrease in Dyx was associated a 4.8 (95% CI, 1.5 - 15.8) odds ratio (OR) for abnormal MPI. With Dyx < 2.0, the 7 AM OR for abnormal MPI was 11.8 (95% CI, 1.2 - 111.4).

CONCLUSIONS

Autonomic dysfunction, measured by non-linear HRV in the morning hours, was associated with an increased OR of abnormal MPI. These results suggest a potentially important role of ECG-based biomarkers in risk stratification for individuals with suspected ischemic heart disease.

Residual heart rate variability measures can better differentiate patients with acute myocardial infarction from patients with patent coronary artery

Purpose

It has been shown that the power spectral density (PSD) of heart rate variability (HRV) can be decomposed into a power-law function and a residual PSD (rPSD) with a more prominent high-frequency component than that in traditional PSD. This study investigated whether the residual HRV (rHRV) measures can better discriminate patients with acute myocardial infarction (AMI) from patients with patent coronary artery (PCA) than traditional HRV measures.

Materials and methods

The rHRV and HRV measures of 48 patients with AMI and 69 patients with PCA were compared.

Results

The high-frequency power of rHRV spectrum was significantly enhanced while the low-frequency and very low-frequency powers of rHRV spectrum were significantly suppressed, as compared to their corresponding traditional HRV spectrum in both groups of patients. The normalized residual high-frequency power (nrHFP = residual high-frequency power/residual total power) was significantly greater than the corresponding normalized high-frequency power in both groups of patients. Between-groups comparison showed that the nrHFP in AMI patients was significantly smaller than that in PCA patients. Receiver operating characteristic curve analysis showed that the nrHFP or nrHFP + normalized residual very low-frequency power (residual very low-frequency power/rTP) had better discrimination capability than the corresponding HRV measures for predicting AMI.

Conclusions

Compared with traditional HRV measures, the rHRV measures can slightly better differentiate AMI patients from PCA patients, especially the nrHFP or nrHFP + normalized residual very low-frequency power.

Heart rate variability in patients with systemic lupus erythematosus: a systematic review and methodological considerations

Aim The aim of this review was to summarize current knowledge about the scientific findings and potential clinical utility of heart rate variability measures in patients with systemic lupus erythematosus. Methods PubMed, Embase and Scopus databases were searched for the terms associated with systemic lupus erythematosus and heart rate variability, including controlled vocabulary, when appropriate. Articles published in English and available in full text were considered. Finally, 11 publications were selected, according to the systematic review protocol and were analyzed. Results In general, heart rate variability, measured in the time and frequency domains, was reported to be decreased in patients with systemic lupus erythematosus compared with controls. In some systemic lupus erythematosus studies, heart rate variability was found to correlate with inflammatory markers and albumin levels. A novel heart rate variability measure, heart rate turbulence onset, was shown to be increased, while heart rate turbulence slope was decreased in systemic lupus erythematosus patients. Reports of associations of changes in heart rate variability parameters with increasing systemic lupus erythematosus activity were inconsistent, showing decreasing heart rate variability or no relationship. However, the low/high frequency ratio was, in some studies, reported to increase with increasing disease activity or to be inversely correlated with albumin levels. Conclusions Patients with systemic lupus erythematosus have abnormal heart rate variability, which reflects cardiac autonomic dysfunction and may be related to inflammatory cytokines but not necessarily to disease activity. Thus measurement of heart rate variability could be a useful clinical tool for monitoring autonomic dysfunction in systemic lupus erythematosus, and may potentially provide prognostic information.

Reduced heart rate response after premature ventricular contraction depending on severity of atrial fibrillation symptoms - Analysis on heart rate turbulence in atrial fibrillation patients

Background

The severity of symptoms during atrial fibrillation (AF) may be influenced by heart rate and blood pressure variation, due to irregular beats and the related adaptations in baroreflex sensitivity. This study investigated whether heart rate turbulence (HRT) as a reflection of baroreflex sensitivity is related to symptom severity during AF.

Method

Ninety-seven patients (pts) who underwent electrophysiological study were enrolled. Consecutive 56 pts had paroxysmal AF (21 with milder symptoms [EHRA I or II; Group-M], 35 with severe symptoms [EHRA III or IV; Group-S]), and 41 age-matched controls without AF were included. After delivering a single ventricular extrastimulus during sinus rhythm and repeating the process 10 times, the quantification of HRT was performed by measuring turbulence onset (TO: heart rate acceleration) and turbulence slope (TS: rate of heart rate deceleration).

Results

Group-M pts showed significantly diminished TO as compared to controls and Group-S pts (P = 0.012). There was no significant difference of the TS between the 3 groups. Given that a TO ≥ 0% or TS ≤ 2.5 ms/RR was considered abnormal, Group-M pts showed significantly higher incidences of abnormal HRT as compared to controls and Group-S pts (71% vs 40% vs 21%, respectively, P = 0.0012). Regression analysis demonstrated an independent and significant association between a diminished TO and milder AF symptoms (P < 0.05).

Conclusions

The usual heart rate acceleration after premature ventricular contraction is significantly diminished in pts with milder AF symptoms as compared to pts with severe AF symptoms. The mechanism of association between this diminished response and symptoms should be further investigated.

Myotonic dystrophy and the heart: A systematic review of evaluation and management

Myotonic dystrophy (MD) is a multisystem, autosomal dominant disorder best known for its skeletal muscle manifestations. Cardiac manifestations arise as a result of myocardial fatty infiltration, degeneration and fibrosis and present most commonly as arrhythmias or conduction disturbances. Guidelines regarding the optimal cardiac management of patients with MD are lacking. The present article provides a summary of the pathophysiology of cardiac problems in patients with MD and provides a practical approach to contemporary cardiac monitoring and management of these patients with a focus on the prevention of complications related to conduction disturbances and arrhythmias.

METHODS

A literature search was performed using PubMed and Medline. The keywords used in the search included "myotonic dystrophy", "cardiac manifestations", "heart", "arrhythmia", "pacemaker" and "defibrillator", all terms were used in combination. In addition, "myotonic dystrophy" was searched in conjunction with "electrophysiology", "electrocardiogram", "echocardiograph", "signal averaged electrocardiograph", "magnetic resonance imaging" and "exercise stress testing". The titles of all the articles revealed by the search were screened for relevance. The abstracts of relevant titles were read and those articles which concerned the cardiac manifestations of myotonic dystrophy or the investigation and management of cardiac manifestations underwent a full manuscript review.

Heart rate variability measurement and clinical depression in acute coronary syndrome patients: narrative review of recent literature

AIM

We aimed to explore links between heart rate variability (HRV) and clinical depression in patients with acute coronary syndrome (ACS), through a review of recent clinical research literature.

BACKGROUND

Patients with ACS are at risk for both cardiac autonomic dysfunction and clinical depression. Both conditions can negatively impact the ability to recover from an acute physiological insult, such as unstable angina or myocardial infarction, increasing the risk for adverse cardiovascular outcomes. HRV is recognized as a reflection of autonomic function.

METHODS

A narrative review was undertaken to evaluate state-of-the-art clinical research, using the PubMed database, January 2013. The search terms "heart rate variability" and "depression" were used in conjunction with "acute coronary syndrome", "unstable angina", or "myocardial infarction" to find clinical studies published within the past 10 years related to HRV and clinical depression, in patients with an ACS episode. Studies were included if HRV measurement and depression screening were undertaken during an ACS hospitalization or within 2 months of hospital discharge.

RESULTS

Nine clinical studies met the inclusion criteria. The studies' results indicate that there may be a relationship between abnormal HRV and clinical depression when assessed early after an ACS event, offering the possibility that these risk factors play a modest role in patient outcomes.

CONCLUSION

While a definitive conclusion about the relevance of HRV and clinical depression measurement in ACS patients would be premature, the literature suggests that these measures may provide additional information in risk assessment. Potential avenues for further research are proposed.