Identifying diabetic patients with cardiac autonomic neuropathy by heart rate complexity analysis

Background  

Cardiac autonomic neuropathy (CAN) in diabetes has been called a "silent killer", because so few patients realize that they suffer from it, and yet its effect can be lethal. Early sub clinical detection of CAN and intervention are of prime importance for risk stratification in preventing sudden death due to silent myocardial infarction. This study presents the usefulness of heart rate variability (HRV) and complexity analyses from short term ECG recordings as a screening tool for CAN.     

Electrophysiological heart rate regulation in patients with the Wolff-Parkinson-White phenomenon and syndrome

The article presents the results of electrocardiography, echocardiography, heart rate variability, and nonlinear dynamics in patients with Wolff-Parkinson-White phenomenon and syndrome (WPW). Fifty-four patients were enrolled in the study; they were divided into three groups: the WPW phenomenon group, the WPW syndrome group, and the group of healthy subject. Using the mathematical models based on correlation analysis, the role of the main pathophysiological mechanisms of the formation of cardiac pathology in WPW syndrome—the disturbances of regulatory mechanisms, as well as the electrical and mechanical remodeling of the myocardium—was proven.     

Determination of heart rate and heart rate variability in the equine fetus by fetomaternal electrocardiography

Heart rate is an important parameter of fetal well-being. We have analyzed fetal heart rate (HR) and heart rate variability (HRV) by fetomaternal electrocardiography (ECG) in the horse (Equus caballus) from midpregnancy to foaling. It was the aim of the study to detect changes in the regulation of fetal cardiac activity over time and to establish normal values in undisturbed pregnancies. A total of 22 mares were available for the study. Fetomaternal electrocardiography was a reliable technique to detect cardiac signals in fetuses between Day 173 of gestation and foaling. Fetal HR decreased from 115 ± 4 beats/min (Days 170 to 240 of gestation) to 83 ± 3 beats/min (Day 320) to 79 ± 1 beats/min (1 d before foaling; P < 0.001). Mean beat to beat (RR) interval and standard deviation of the RR interval (SDRR) increased (P < 0.001). Gestational age thus affects RR interval and HR in the equine fetus. From Days 270 to 340 of gestation, SDRR increased from 11.4 ± 1.3 msec on Day 270 to 27.8 ± 3.6 msec on Day 340 (P < 0.05), and the root mean square of successive RR differences (RMSSD) tended to increase (P = 0.07), indicating maturation of the fetal autonomous nervous system. For the last 10 d before foaling, fetal HR and HRV remained constant and did not allow predicting the onset of parturition in the horse. Only during the last 30 min before the foal was born, in 4 of 5 fetuses, HR decreased and RR interval increased. Accelerations and decelerations in HR were detectable at all times, but neither their number nor duration changed over time.     

Changes in the heart rate variability in patients with obstructive sleep apnea and its response to acute CPAP treatment

Introduction

Obstructive Sleep Apnea (OSA) is a major risk factor for cardiovascular disease. The goal of this study was to demonstrate whether the use of CPAP produces significant changes in the heart rate or in the heart rate variability of patients with OSA in the first night of treatment and whether gender and obesity play a role in these differences.

Methods

Single-center transversal study including patients with severe OSA corrected with CPAP. Only patients with total correction after CPAP were included. Patients underwent two sleep studies on consecutive nights: the first night a basal study, and the second with CPAP. We also analyzed the heart rate changes and their relationship with CPAP treatment, sleep stages, sex and body mass index. Twenty-minute segments of the ECG were selected from the sleep periods of REM, no-REM and awake. Heart rate (HR) and heart rate variability (HRV) were studied by comparing the R-R interval in the different conditions. We also compared samples from the basal study and CPAP nights.

Results

39 patients (15 females, 24 males) were studied. The mean age was 50.67 years old, the mean AHI was 48.54, and mean body mass index was 33.41 kg/m² (31.83 males, 35.95 females). Our results showed that HRV (SDNN) decreased after the use of CPAP during the first night of treatment, especially in non-REM sleep. Gender and obesity did not have any influence on our results.

Conclusions

These findings support that cardiac variability improves as an acute effect, independently of gender or weight, in the first night of CPAP use in severe OSA patients, supporting the idea of continuous use and emphasizing that noncompliance of CPAP treatment should be avoided even if it is just once.     

Blood pressure and heart rate in patients with ischaemic heart disease receiving nifedipine and propranolol.

A randomised controlled crossover trial was performed to assess the anti-anginal effects of nifedipine and propranolol separately and together. The effects of these treatments on blood pressure and heart rate were assessed at rest and after the cold pressor and mental arithmetic tests. Nifedipine and propranolol together produced the greatest reduction in supine and erect systolic and diastolic blood pressures. Propranolol (480 mg daily) lowered resting systolic/diastolic blood pressures by 7/6 mm Hg and nifedipine (60 mg daily) lowered it by 10/8 mm Hg, while in the erect position the hypotensive effect of these agents averaged 9/8 mm Hg. During the cold pressor test propranolol lowered the maximum pressure by an average of 11/6 mm Hg and nifedipine by 19/10 mm Hg. For the mental arithmetic test, the results were 7/2 mm Hg and 16/7 mm Hg respectively. Propranolol (480 mg daily)reduced supine and erect heart rate by 19 and 25 beats/minute respectively, while nifedipine did not alter heart rate significantly. The favourable haemodynamic responses to nifedipine suggest that it may be of value in the management of hypertension.     

Complex of immunological characteristics for the diagnostics of pancreatogenic immunodeficiency

The results of the immunological study of blood in 89 patients with severe acute pancreatitis (SAP) were analyzed. Immune reactions in SAP were characterized by the presence of moderate leukocytosis, an increase in the phagocytic and metabolic activity of neutrophils, relative lymphopenia, a decrease in the number of B-lymphocytes. The average values of the parameters of the immunogram of patients with the favorable course of the disease on days 2 - 3 were analogous to the average population values in 89 examinees. The direction and the degree of manifestation were slightly variable and could be registered within one standard quadratic deviation. Such heterogeneity in the character of immune reactions made it possible to regard the average values of the immunogram parameters of these patients as "the norm". For the objective evaluation of the immune status of SAP patients a scale for the evaluation, in points, of disturbances in immune reactions to the destructive process in the pancreas was developed. This scale for the evaluation, in points, of the severity of disturbances in the immune status of SAP patients made it possible to prognosticate the development of complications.     

Learned control of heart rate during exercise in patients with borderline hypertension

Twelve patients with borderline hypertension [less than or equal to 21 X 33/12.6, greater than or equal to 18 X 6/12.0 kPa (less than or equal to 160/95; greater than or equal to 140/90 mm Hg)] participated in an experiment aimed at testing whether they could learn to attenuate heart rate while exercising on a cycle ergometer. Six experimental (E) subjects received beat-to-beat heart-rate feedback and were asked to slow heart rate while exercising; six control (C) subjects received no feedback. Averaged over 5 days (25 training trials) the exercise heart-rate of the E group was 97.8 bt min-1, whereas the C group averaged 107 bt min-1 (P = 0.03). Systolic blood pressure was unaffected by feedback training. Generally, changes in rate-pressure product reflected changes in heart-rate. Oxygen consumption was lower in the E than in the C group late in training. We conclude that neurally mediated changes associated with exercise in patients with borderline hypertension can be brought under behavioral control through feedback training.     

Effect of stimulating the auricular branch of the vagus nerve on the heart rate in patients with severe chronic heart failure

A study was made to evaluate the prospects of improving the cardiac function by electrical stimulation of the auricular branch of the vagus nerve in patients with severe chronic heart failure (CHF). Sympathetic hyperactivity and the cardiac function were evaluated by 24-hour ECG monitoring, echocardiography, and a 6-min walk test. At the time of enrollment into the study, patients had a heart rate (HR) of more than 60 bpm, a left ventricular (LV) ejection fraction (EF) of less than 40%, and CHF NYHA functional class (FC) III or IV even with well tolerated medications. Control-group patients (n = 7) did not show significant changes in the functional state of the heart after sham treatment. In the test group (n = 44), a significant increase in LV EF and a decrease in end-systolic volume were induced by electrical pulse stimulation of the auricular branch. A decrease in HR was documented in 34 patients; CHF FC decreased by one or two grades in 40 patients. The changes were assumed to reflect new balance achieved in the autonomic regulation of the heart to contribute to sustaining competence of the myocardium. Electrical pulse stimulation of the auricular branch of the vagus nerve was concluded to provide a safe and efficacious addition to drug therapy in patients with severe CHF.     

Reassessment of failed beta-blocker treatment in angina pectoris by peak-exercise heart rate measurements.

Twenty-one patients with angina pectoris were treated with adrenergic beta-receptor antagonists. Previously the resting heart rate had been used as a guide to treatment, a reduction in the rate to 55-60 beats/min without symptomatic improvement indicating failure of medical treatment. These patients were re-evaluated before coronary arteriography using the peak-exercise heart rate as an index of adrenergic beta-receptor antagonism. The dose of beta-blocking drugs was increased to produce a peak-exercise heart rate of less than 100 beats/min or a consistent rate of 100-125 beats/min which would not lessen in spite of progressive dose increments. The resting heart rate was ignored. On these criteria 15 patients previously considered to have responded inadequately to beta-blockade responded satisfactorily and were therefore removed from the waiting list for coronary arteriography. They all remained well up to two years later. Six patients failed to respond and had coronary arteriography with a view to surgical treatment. Reliance on the resting heart rate as the index of optimum adrenergic beta-receptor antagonism is likely to lead to premature or unnecessary referral for surgery; the failure of beta-blockade in the treatment of angina pectoris can be determined simply and accurately by using peak-exercise heart rate.     

Autonomic control of heart rate during exercise studied by heart rate variability spectral analysis.

Spectral analysis of heart rate variability (HRV) might provide an index of relative sympathetic (SNS) and parasympathetic nervous system (PNS) activity during exercise. Eight subjects completed six 17-min submaximal exercise tests and one resting measurement in the upright sitting position. During submaximal tests, work rate (WR) was increased for the initial 3 min in a ramp fashion until it reached constant WRs of 20 W, or 30, 60, 90, 100, and 110% of the predetermined ventilatory threshold (Tvent). Ventilatory profile and alveolar gas exchange were monitored breath by breath, and beat-to-beat HRV was measured as R-R intervals of an electrocardiogram. Spectral analysis was applied to the HRV from 7 to 17 min. Low-frequency (0-0.15 Hz) and high-frequency (0.15-1.0 Hz) areas under power spectra (LO and HI, respectively) were calculated. The indicator of PNS activity (HI) decreased dramatically (P less than 0.05) when the subjects exercised compared with rest and continued to decrease until the intensity reached 60% Tvent. The indicator of SNS activity (LO/HI) remained unchanged up to 100% Tvent, whereas it increased abruptly (P less than 0.05) at 110% Tvent. The results suggested that (cardiac) PNS activity decreased progressively from rest to a WR equivalent to 60% Tvent, and SNS activity increased only when exercise intensity exceeded Tvent.     

The relationship of the slope of the heart rate graph regression with linear and nonlinear heart rate dynamics in stationary short-time series

The relationship of the slope of the heart rate graph regression curve (b ₁) with periodic (linear) and nonlinear heart rate dynamics has been studied in stationary short-time series (256 points). For estimating nonlinear dynamics, a parameter derived from correlation dimension has been used, which has made it possible to estimate chaotic processes in short-time series. According to the results of the study, the heart rate dynamics in short-time series may be represented as a sum of linear (periodic) and nonlinear (stochastic) processes. The relationships of b ₁ with both the linear and the nonlinear heart rate dynamics have been demonstrated. Equations for calculating the absolute and relative (to the periodic oscillation amplitude) noises in the heart rate dynamics in short-time series are proposed. Stochastic nonlinear dynamics in different physiological states of humans have been compared. It has been found that the increase in the relative noise intensity in the heart rate dynamics with an increase in respiration rate is determined not only by the decrease in the amplitude of respiratory waves, but also by an increase in the amplitude of the noise itself. The absolute noise intensity is decreased in the states of neurotic excitement, fatigue, and, especially, mental stress. In the state of rest, nonlinear (stochastic) processes dominate over linear (periodic) ones.     

电刺激迷走神经对蟾蜍心率和心率变异的影响

目的:观察不同频率迷走神经刺激对蟾蜍离体心脏的心率及心率变异的影响。方法:将蟾蜍心脏和右侧迷走交感干离体后,以不同频率电刺激神经,记录心电图曲线并作心率变异性(HRV)分析。结果:交感神经阻断后,电刺激迷走交感干,心率(HR)显著下降(P0.01),全部正常心动周期的标准差(SDNN)和相邻正常心动周期差值的均方根(RMSSD)显著升高(P0.01),不同频率刺激组之间没有明显差异;与对照组相比,各指标变化较大;给药组0.2Hz时高频(HF)显著升高(P0.01),低频/高频比值(LF/HF)明显降低(P0.05),0.8Hz时HF和LF/HF接近刺激前水平。结论:一定范围内增加刺激频率,迷走神经降低心率的作用增强;没有交感神经调节条件下的迷走神经对心率和心率变异的调节可能存在不同的机制。     

Effect of ivabradine-induced heart rate reduction on flow-mediated dilation measured with high-sensitivity ultrasound in patients with stable coronary heart disease

Background

Experimental data suggests that exclusive heart rate reduction with ivabradine is associated with the amelioration of the endothelial function. Since it is presently unknown whether this also applies to humans, the aim of this pilot study was to investigate whether heart rate reduction with ivabradine modulates the endothelial function in humans with an established coronary heart disease.

Methods

Using high-sensitivity ultrasound, we analysed the flow-mediated (FMD) and nitro-mediated dilation (NMD) of the brachial artery in 25 patients (62.9?±?8.4 years) with a stable coronary heart disease and a resting heart rate of ≥70 beats per minute (bpm). To assess acute effects, measurements were performed before and 4 hours after the first intake of ivabradine 7.5 mg. Sustained effects of an ivabradine therapy (5 mg to 7.5 mg twice daily) were investigated after 4 weeks.

Results

We found a significant decrease in heart rate, both 4 hours after the intake of 7.5 mg of ivabradine (median -8 [interquartile range (IQR) -14 to -4] bpm) and after 4 weeks of twice daily intake (median -10 [IQR-17 to -5] bpm) (p?<?0.05). However, the FMD did not change significantly: neither after first dose of ivabradine nor after sustained therapy (baseline FMD: median 5.0 [IQR 2.4 to 7.9]%; FMD 4 hours after 7.5 mg of ivabradine: median 4.9 [IQR 2.7 to 9.8]%; FMD after 4 weeks of ivabradine therapy: median 6.1 [IQR 4.3 to 8.2]%). No significant changes of the NMD were observed. In regression analysis, the heart rate and FMD did not correlated, irrespective of the ivabradine intake (r²?=?0.086).

Conclusion

In conclusion, in our study heart rate reduction through ivabradine does not improve the endothelial function in patients with a stable coronary heart disease. Moreover, we found no correlation between the heart rate and the endothelial function.