Including patients with diabetes mellitus or coronary artery bypass grafting decreases the association between heart rate variability and mortality after myocardial infarction

Heart Rate Variability and Its Role in Predicting Atrial Fibrillation in Patients Undergoing Coronary Artery Bypass Graft

Background

An association between heart rate variability (HRV) and cardiac events in certain diseases has been demonstrated. However, the association with new-onset atrial fibrillation (AF) after coronary artery bypass grafting (CABG) is still controversial. This study aimed to investigate the association between HRV and new-onset AF in patients undergoing CABG during a 6-month follow-up.

Methods

This prospective study included 119 consecutive patients who underwent off-pump CABG. All patients were assessed using 24-hour Holter recordings 2 days before CABG and 1 week, 3 months, and 6 months postoperatively. HRV was analyzed, and AF was detected from its recordings.

Main results

In patients undergoing CABG, NYHA III increased the AF rate 7 days postoperatively, and advanced age and diabetes were associated with AF 6 months postoperatively. A reduction in time-domain measurements before surgery was significantly associated with a higher risk of developing AF seven days postoperatively; no association between preoperative HRV and AF was found at six months. Reduced preoperative HRV (SDNN (standard deviation of all normal-to-normal intervals [) < 50 ms) was an independent predictor of AF at 3 (AUC = 0.65) and 6 months (AUC = 0.62) following surgery.

Conclusion

A reduction in the time domain measurements before CABG was associated with a higher risk of new-onset AF at 7 days postoperatively but not at 6 months. An SDNN <50 ms was a weak independent predictor of a higher incidence of AF at 3 and 6 months post-surgery.

Heart Rate Variability Analysis May Identify Individuals With Williams-Beuren Syndrome at Risk of Sudden Death

BACKGROUND

Williams-Beuren syndrome (WBS) (Online Mendelian Inheritance in Man #194050) is a rare genetic multisystem disorder resulting from a chromosomal microdeletion at 7q11.23. The condition is characterized by distinct facies, intellectual disability, and supravalvar aortic stenosis. Those with WBS have an increased risk of sudden death, but mechanisms underlying this phenotype are incompletely understood.

OBJECTIVES

The aim of this study was to quantify and compare autonomic activity as reflected by heart rate variability (HRV) measures in a cohort of individuals with WBS (n = 18) and age- and sex-matched control subjects (n = 18).

METHODS

We performed HRV analysis on 24-hour electrocardiography recordings using nonlinear, time and frequency domain analyses on a cohort of subjects with WBS and age- and sex-matched control subjects enrolled in a prospective cross-sectional study designed to characterize WBS disease natural history.

RESULTS

WBS subjects demonstrated diminished HRV (reflected by the SD of the NN intervals [P = 0.0001], SD of the average NN interval for 5-minute intervals over 24 hours [P < 0.0001], average of the 5-minute SDs of NN intervals for 24 hours [P = 0.0002], root mean square of successive differences of NN intervals [P = 0.0004], short axis of the Poincaré plot (SD1) [P < 0.0001], and long axis of the Poincaré plot [P < 0.0001]) and indirect markers of parasympathetic activity (reflected by the percent of NN intervals different from previous by 50% or more of local average [P < 0.0007], root mean square of successive differences of NN intervals [P = 0.0004], natural log high-frequency power [P = 0.0038], and SD1 [P < 0.0001]). Additional parameters were also significantly different, including natural log very low-frequency power (decreased; P = 0.0002), natural log low-frequency power (decreased; P = 0.0024), and SD1 divided by the long axis of the Poincaré plot (decreased; P < 0.0001).

CONCLUSIONS

Individuals with WBS demonstrate significant HRV abnormalities consistent with diminished autonomic reserve. Future studies will be needed to determine the relationship between autonomic dysregulation observed and sudden death risk seen in these patients. (Impact of Elastin Mediated Vascular Stiffness on End Organs; NCT02840448).

Pattern Changes in the Heart Rate Variability of Patients Undergoing Coronary Artery Bypass Grafting Surgery

Introduction

Coronary artery bypass grafting (CABG) with extracorporeal circulation is a key therapy for coronary artery disease (CAD). However, cardiovascular events and cardiac arrhythmias may still occur in these patients following surgery. Many studies have demonstrated a correlation between cardiac arrhythmias and heart rate variability (HRV). This study aimed to establish the temporal change pattern of HRV observed following CABG.

Methods

A prospective method was used to study 119 consecutive patients with stable CAD who were assessed using 24-hour Holter recordings 2 days before CABG and 1 week, 3 months, and 6 months after the surgery at Hanoi Heart Hospital from June 2016 to August 2018. Main results: All the time-domain and frequency-domain parameters of HRV decreased precipitately after CABG and were mostly recovered 3 months postoperatively. The percentage of decreased HRV before surgery was 28.6% and 51.8% after 7 days, 19.6% after 3 months, and 12.7% after 6 months. ASDNN and SDNN before and after surgery had the highest rates of change.

Conclusion

The early decrease in HRV observed 7 days after CABG may be related to the acute effects of the surgery. The recovery of HRV at 3 months after surgery, regardless of the preoperative state of the patients, implies that the autonomic nervous system (ANS) disorder may be improved at this time. At 6 months after surgery, the autonomic nervous injury was recovered in combination with improvement of reperfusion, resulting in improvement in almost all HRV indices compared with those indices preoperatively.

Prognostic value of heart rate variability in patients with coronary artery disease in the current treatment era

Coronary artery disease (CAD) mortality has declined substantially over the past decades thanks to advancing medical and interventional/surgical treatments; therefore, the prognostic value of the heart rate variability in CAD in the current treatment era is not well established. We evaluated the prognostic significance of baseline heart rate variability in 1,757 ARTEMIS study patients with angiographically verified CAD. During an average follow-up time of 8.7 ± 2.2 years, a total of 285 (16.2%) patients died. Of the patients, 63 (3.6%) suffered sudden cardiac death or were resuscitated from sudden cardiac arrest (SCD/SCA), 60 (3.4%) experienced non-sudden cardiac death (NSCD), and death attributable to non-cardiac causes (NCD) occurred in 162 (9.2%) patients. For every 10 ms decrease in standard deviation of normal to normal intervals the risk for SCD/SCA, NSCD and NCD increased significantly: HR 1.153 (95% CI 1.075–1.236, p<0.001), HR 1.187 (95% CI 1.102–1.278, p<0.001) and HR 1.080 (95% CI 1.037–1.125, p<0.001), respectively. The natural logarithm of the low-frequency component of the power spectrum and the short-term scaling exponent of the detrended fluctuation analysis also had significant association with all modes of death (p<0.001). After relevant adjustment, standard deviation of normal-to-normal intervals retained its association with NSCD and NCD (p<0.01), the natural logarithm of the low-frequency component of the power spectrum with all modes of death (p from <0.05 to <0.01), and the short-term scaling exponent of the detrended fluctuation analysis with SCD/SCA (p<0.05) and NCD (p<0.001). In conclusion, impairment of many measures of heart rate variability predicts mortality but is not associated with any specific mode of death in patients with stable CAD during the current treatment era, limiting the clinical applicability of heart rate variability to targeting therapy.

Comparative study of short-term cardiovascular autonomic control in cardiac surgery patients who underwent coronary artery bypass grafting or correction of valvular heart disease

Introduction: Our aim was to perform a comparative study of short-term cardiovascular autonomic control in cardiac surgery patients who underwent coronary artery bypass grafting (CABG) or surgical correction of valvular heart disease (SCVHD ). Methods: The synchronous 15 minutes records of heart rate variability (HRV) and finger's photoplethysmographic waveform variability (PPGV) were performed in 42 cardiac surgery patients (12 women) aged 61.8 ± 8.6 years (mean ± standard deviation), who underwent CABG, and 36 patients (16 women) aged 54.2 ± 14.9 years, who underwent SCVHD , before surgery and in 5-7 days after surgery. Conventional time and frequency domain measures of HRV and index S of synchronization between the slow oscillations in PPGV and HRV were analyzed. We also calculated personal dynamics of these indices after surgery. Results: We found no differences (Р > 0.05) in all studied autonomic indices (preoperative and post-surgery) between studied patients' groups, except for the preoperative heart rate, which was higher in patients who underwent SCVHD (P = 0.013). We have shown a pronounced preoperative and post-surgery variability (magnitude of inter-quartile ranges) of all autonomic indices in studied patients. In the cluster analysis based on cardiovascular autonomic indices (preoperative and post-surgery), we divided all patients into two clusters (38 and 40 subjects) which did not differ in all clinical characteristics (except for the preoperative hematocrit, P = 0.038), index S, and all post-surgery HRV indices. First cluster (38 patients) had higher preoperative values of the HR, TP, HF, and HF%, and lower preoperative values of the LF% and LF/HF. Conclusion: The variability of cardiovascular autonomic indices in on-pump cardiac surgery patients (two characteristic clusters were identified based on preoperative indices) was not associated with their clinical characteristics and features of surgical procedure (including cardioplegia).

Changes in Heart Rate Variability after Coronary Artery Bypass Grafting and Clinical Importance of These Findings

Heart rate variability is a physiological feature indicating the influence of the autonomic nervous system on the heart rate. Association of the reduced heart rate variability due to myocardial infarction and the increased postinfarction mortality was first described more than thirty years ago. Many studies have unequivocally demonstrated that coronary artery bypass grafting surgery generally leads to significant reduction in heart rate variability, which is even more pronounced than after myocardial infarction. Pathophysiologically, however, the mechanisms of heart rate variability reduction associated with acute myocardial infarction and coronary artery bypass grafting are different. Generally, heart rate variability gradually recovers to the preoperative values within six months of the procedure. Unlike the reduced heart rate variability in patients having sustained myocardial infarction, a finding of reduced heart rate variability after coronary artery bypass surgery is not considered relevant in predicting mortality. Current knowledge about changes in heart rate variability in coronary patients and clinical relevance of such a finding in patients undergoing coronary artery bypass grafting are presented.

Heart rate variability in risk stratification of cardiac patients

Heart rate (HR) variability has been extensively studied in cardiac patients, especially in patients surviving an acute myocardial infarction (AMI) and also in patients with congestive heart failure (CHF) or left ventricular (LV) dysfunction. The majority of studies have shown that patients with reduced or abnormal HR variability have an increased risk of mortality within a few years after an AMI or after a diagnosis of CHF/LV dysfunction. Various measures of HR dynamics, such as time-domain, spectral, and non-linear measures of HR variability have been used in risk stratification. The prognostic power of various measures, except of those reflecting rapid R-R interval oscillations, has been almost identical, albeit some non-linear HR variability measures, such as short-term fractal scaling exponent have provided somewhat better prognostic information than the others. Abnormal HR variability predicts both sudden and non-sudden cardiac death. Because of remodeling of the arrhythmia substrate after AMI, early measurement of HR variability to identify those at high risk should likely be repeated later in order to assess the risk of fatal arrhythmia events. Future randomized trials using HR variability/turbulence as one of the pre-defined inclusion criteria will show whether routine measurement of HR variability/turbulence will become a routine clinical tool for risk stratification of cardiac patients.

Clinical application of heart rate variability after acute myocardial infarction

Heart rate (HR) variability has been extensively studied in patients surviving an acute myocardial infarction (AMI). The majority of studies have shown that patients with reduced or abnormal HR variability/turbulence have an increased risk of mortality within few years after an AMI. Various measures of HR dynamics, such as time-domain, spectral, and non-linear measures of HR variability, as well as HR turbulence, have been used in risk stratification of post-AMI patients. The prognostic power of various measures, except of those reflecting rapid R-R interval oscillations, has been almost identical, albeit some non-linear HR variability measures, such as short-term fractal scaling exponent, and HR turbulence, have provided somewhat better prognostic information than the others. Abnormal HR variability predicts both sudden and non-sudden cardiac death after AMI. Because of remodeling of the arrhythmia substrate after AMI, early measurement of HR variability to identify those at high risk should likely be repeated later in order to assess the risk of fatal arrhythmia events. Future randomized trials using HR variability/turbulence as one of the pre-defined inclusion criteria will show whether routine measurement of HR variability/turbulence will become a routine clinical tool for risk stratification of post-AMI patients.

Determinants of a reduced heart rate variability in chronic atrial fibrillation

BACKGROUND

We aimed to evaluate whether clinical factors, which influence heart rate variability (HRV) in the presence of undisturbed sinus rhythm, have any associations with HRV in patients with permanent atrial fibrillation (AF).

METHODS

One hundred ninety-seven consecutive patients with permanent AF were included (122 males, 75 females, aged 64 ± 11 years, range 25-85). In each patient a 24-hour electrocardiographic recording was performed and an HRV fraction (HRVF)-the index based on scatter plot numerical processing-was calculated. Additionally, standard HRV measures were analyzed. Reduced HRVF was defined as its value lower than lower normal limit. Demographic and clinical factors were examined for their association with a reduced HRVF by means of a univariate and multivariate logistic regression analysis.

RESULTS

The reduced HRVF was associated with advanced age, clinical diagnosis of a previous MI or dilated cardiomyopathy, presence of diabetes, depressed left ventricular function, NYHA class > II, treatment regimen, use of digoxin, diuretics or antiarrhythmic agents, nonuse of beta-blockers, and increased heart rate. The independent determinants that sustained after multivariate analysis were: heart rate (per 10 bpm increase, odds ratio 2.77 [1.88-4.07]), age (per 5 years increase 1.43 [1.1-1.85]), depressed left ventricular EF (<30% vs higher 2.26 [1.19-4.31]), and presence of diabetes (3.45 [1.1-10.85]). The HRVF correlated moderately with standard HRV measures. This index showed also the strongest correlation with left ventricular ejection fraction.

CONCLUSION

We concluded that advanced age, left ventricular systolic dysfunction, increased heart rate, and presence of diabetes are cofactors of a reduced HRV in AF patients. Thus, the determinants of heart rate variability in the presence of atrial fibrillation are the same as those in sinus rhythm.

Heart rate variability and non-linear dynamics in risk stratification

The time-domain measures and power–spectral analysis of heart rate variability (HRV) are classic conventional methods to assess the complex regulatory system between autonomic nervous system and heart rate and are most widely used. There are abundant scientific data about the prognostic significance of the conventional measurements of HRV in patients with various conditions, particularly with myocardial infarction. Some studies have suggested that some newer measures describing non-linear dynamics of heart rate, such as fractal measures, may reveal prognostic information beyond that obtained by the conventional measures of HRV. An ideal risk indicator could specifically predict sudden arrhythmic death as the implantable cardioverter-defibrillator (ICD) therapy can prevent such events. There are numerically more sudden deaths among post-infarction patients with better preserved left ventricular function than in those with severe left ventricular dysfunction. Recent data support the concept that HRV measurements, when analyzed several weeks after acute myocardial infarction, predict life-threatening ventricular tachyarrhythmias in patients with moderately depressed left ventricular function. However, well-designed prospective randomized studies are needed to evaluate whether the ICD therapy based on the assessment of HRV alone or with other risk indicators improves the patients’ prognosis. Several issues, such as the optimal target population, optimal timing of HRV measurements, optimal methods of HRV analysis, and optimal cutpoints for different HRV parameters, need clarification before the HRV analysis can be a widespread clinical tool in risk stratification.

Improvements in heart rate variability with exercise therapy

Heart rate variability (HRV) is a noninvasive, practical and reproducible measure of autonomic nervous system function. A heart rate that is variable and responsive to demands is believed to bestow a survival advantage, whereas reduced HRV may be associated with poorer cardiovascular health and outcomes. In recent years, many researchers have investigated the prognostic implications of HRV in a variety of clinical populations. Evidence suggests that reduced HRV has prognostic significance for individuals with myocardial infarction, chronic heart failure, unstable angina and diabetes mellitus. Interventions to increase HRV, such as exercise therapy, have also been examined. The findings of the present review suggest that exercise therapy may improve HRV in myocardial infarction, chronic heart failure and revascularization patients by increasing vagal tone and decreasing sympathetic activity. One hypothesis is that a shift toward greater vagal modulation may positively affect the prognosis of these individuals. While the underlying mechanisms by which exercise training improves vagal modulation are speculative at present, angiotensin II and nitric oxide may be potential mediators.

New York Heart Association functional class influences the impact of diabetes on cardiac autonomic function

BACKGROUND

Diabetes (D) and heart failure (HF) are associated with abnormal heart rate variability (HRV). It is unclear whether the HRV effect of having both is cumulative.

METHODS

Pretreatment HRV (traditional, nonlinear, and heart rate [HR] turbulence) in 80 D versus 74 non-D (ND) systolic HF patients was compared by New York Heart Association II versus III among patients entered into an HF drug evaluation study.

RESULTS

Age-adjusted HR was lower in class II D versus class III and most HRV including HR turbulence was better in class II ND versus all others, with few differences between class II D and class III ND and D patients.

CONCLUSION

The effect of D and HF on autonomic function may be cumulative in class II, but D may have little additional effect on most HRV in class III patients. The prognostic value of different HRV measures in D versus ND HF patients should be further investigated.

The relationships among heart rate variability, inflammatory markers and depression in coronary heart disease patients

Studies show negative correlations between heart rate variability (HRV) and inflammatory markers. In cardiac patients, depression is related to both. We investigated links between short-term HRV and inflammatory markers in relation to depression in acute coronary syndrome (ACS) patients. We measured C-reactive protein (CRP), interleukin-6 (IL-6), depression symptoms (Beck Depression Inventory, BDI-II), and SDNN, high frequency (HF) and low frequency (LF) power at rest in 682 (553 men) patients approximately two months post-ACS. There were no differences in HRV measures between those with and without elevated depressions symptoms (BDI-II >or= 14). However, all HRV measures were negatively and significantly associated with both inflammatory markers. Relationships were stronger in patients with BDI-II >or= 14. Differences were significant for CRP and not explained by covariates (including age, sex, previous MI, left ventricular ejection fraction, coronary bypass surgery at index admission, diabetes, smoking, body mass index (BMI), fasting cholesterol, fasting glucose, angiotensin-converting-enzyme inhibitors, beta-blockers, statins, and antidepressants). HRV independently accounted for at least 4% of the variance in CRP in the depressed, more than any factor except BMI. Relationships between measures of inflammation and autonomic function are stronger among depressed than non-depressed cardiac patients. Interventions targeting regulation of both autonomic control and inflammation may be of particular importance.

Progressive Impairment of Autonomic Control of Heart Rate in Patients with Multiple Sclerosis

BACKGROUND

Data regarding the autonomic control of heart rate in multiple sclerosis (MS) patients depending on the disease duration are lacking in the literature. The goal of this study was to evaluate differences in heart rate variability (HRV) in patients with MS according to the duration of the disease.

METHODS

The study included 39 patients (23 female and 16 male; median age 42 years, range 34-53 years) with relapsing-remitting MS (RRMS) in stable phase and 39 age- and sex-matched healthy controls. RRMS patients were divided into two groups: group 1 with 21 patients within 5 years and group 2 with 18 patients with >5 years from the diagnosis of MS. HRV analysis was done with 24-h Holter ECG.

RESULTS

Patients with RRMS had a significantly lower overall HRV than controls: SDNN 91+/-18 msec vs. 135+/-24 msec, p<0.001. RRMS patients with lower duration of disease (Group 1) had all higher HRV parameters except LF/HF ratio compared with RRMS patients with >5 years from the diagnosis of MS (Group 2): SDNN 94+/-24 vs. 88+/-21 msec, p=0.008; TP 2028+/-1326 vs. 1683+/-1017 ms2, p=0.006.

CONCLUSIONS

Results of the study suggested that the autonomic control of heart rate depends on the disease duration in RRMS patients. Longer disease duration led to progressive impairment of cardiac autonomic balance in MS patients.

Comparison of the short-term effects of salmeterol and formoterol on heart rate variability in adult asthmatic patients

STUDY OBJECTIVES

We investigated the effects of beta2-adrenergic agonists salmeterol and formoterol on heart rate variability (HRV) in adult asthmatic patients using time-domain measures of HRV.

PATIENTS

Thirty-nine adult patients with asthma were studied. All patients showed a mild-to-moderate decrease in baseline FEV1. Any diseases that might have influenced the autonomic function were excluded. All patients underwent a complete physical examination and medical history that revealed no cardiovascular disease or medication.

METHODS

The beta2-adrenergic inhaled agonists salmeterol, 50 microg, and formoterol, 12 microg, were used in the study. HRV analysis was performed for each 5-min segment: 5 min and 10 min before inhalation of the study drug, and 5, 10, 15, 20, 25, and 30 min after inhalation. Time-domain parameters of HRV were calculated: (1) the SD all normal-to-normal intervals; (2) the SD of the mean of all normal-to-normal intervals in all 5-min segments of the entire recording; (3) the root mean square of differences between adjacent normal-to-normal intervals; (4) the mean of the SD of all normal-to-normal intervals in all the 5-min intervals; and (5) the SD of the SD of all normal-to-normal intervals in all the 5-min intervals.

RESULTS

Baseline HRV parameters were not significantly different between formoterol and salmeterol groups. There were no significant differences in HRV parameters after formoterol and salmeterol inhalation. The HRV parameters in each 5-min segment in the formoterol group were not statistically significant different when compared to the same segment in the salmeterol group.

CONCLUSION

Salmeterol and formoterol have no short-term adverse effects on HRV.

Traditional and nonlinear heart rate variability are each independently associated with mortality after myocardial infarction

INTRODUCTION

Decreased heart rate variability (HRV) and abnormal nonlinear HRV shortly after myocardial infarction (MI) are risk factors for mortality. Traditional HRV predicts mortality in patients with a range of times post-MI, but the association of nonlinear HRV and outcome in this population is unknown.

METHODS AND RESULTS

HRV was determined from 740 tapes recorded before antiarrhythmic therapy in Cardiac Arrhythmia Suppression Trial patients with ventricular premature contractions (VPCs) suppressed on the first randomized treatment. Patients were 70 +/- 121 days post-MI. Follow up was 362 +/- 241 days (70 deaths). The association between traditional time and frequency-domain HRV and mortality and nonlinear HRV and mortality were compared for the entire population (ALL), those without coronary artery bypass graft post-MI (no CABG), and those without CABG or diabetes (no CABG, no DIAB) using univariate and multivariate Cox regression analysis. Strength of association was compared by P values and Wald Chi-square values. Nonlinear HRV included short-term fractal scaling exponent, power law slope, and SD12 (Poincare dimension). For ALL and for no CABG, increased daytime SD12 had the strongest association with mortality (P=0.002 ALL and P <0.001 no CABG). For no CABG, no DIAB increased 24-hour SD12 hours had the strongest association (P <0.001) with mortality. Upon multivariate analysis, increased SD12, decreased ln ULF (ultra low frequency), and history of prior MI and history of congestive heart failure each remained in the model.

CONCLUSION

Nonlinear HRV is associated with mortality post-MI. However, as with traditional HRV, this is diluted by CABG surgery post-MI and by diabetes. Results suggest that decreased long-term HRV and increased randomness of heart rate are each independent risk factors for mortality post-MI.

Increased sympathetic and decreased parasympathetic cardiovascular modulation in normal humans with acute sleep deprivation

Cardiovascular autonomic modulation during 36 h of total sleep deprivation (SD) was assessed in 18 normal subjects (16 men, 2 women, 26.0 +/- 4.6 yr old). ECG and continuous blood pressure (BP) from radial artery tonometry were obtained at 2100 on the first study night (baseline) and every subsequent 12 h of SD. Each measurement period included resting supine, seated, and seated performing computerized tasks and measured vigilance and executive function. Subjects were not supine in the periods between measurements. Spectral analysis of heart rate variability (HRV) and BP variability (BPV) was computed for cardiac parasympathetic modulation [high-frequency power (HF)], sympathetic modulation [low-frequency power (LF)], sympathovagal balance (LF/HF power of R-R variability), and BPV sympathetic modulation (at LF). All spectral data were expressed in normalized units [(total power of the components/total power-very LF) x 100]. Spontaneous baroreflex sensitivity (BRS), based on systolic BP and pulse interval powers, was also measured. Supine and sitting, BPV LF was significantly increased from baseline at 12, 24, and 36 h of SD. Sitting, HRV LF was increased at 12 and 24 h of SD, HRV HF was decreased at 12 h SD, and HRV LF/HF power of R-R variability was increased at 12 h of SD. BRS was decreased at 24 h of SD supine and seated. During the simple reaction time task (vigilance testing), the significantly increased sympathetic and decreased parasympathetic cardiac modulation and BRS extended through 36 h of SD. In summary, acute SD was associated with increased sympathetic and decreased parasympathetic cardiovascular modulation and decreased BRS, most consistently in the seated position and during simple reaction-time testing.