Tomasz Krauze

Heart rate asymmetry by Poincaré plots of RR intervals.

Abstract The Poincaré plot is a widely used method for visualizing and calculating heart rate variability and for investigating the oscillatory nature of heart action. We show that the Poincaré plot produced using physiological data for RR intervals is asymmetric. This suggests that the processes of heart rate acceleration (shortening of consecutive RR intervals) and deceleration (prolongation of successive RR intervals) might be asymmetric. To investigate this phenomenon, we define descriptors quantifying the heart rate asymmetry and present the results of a study involving 5-min ECG recordings of 50 healthy subjects in which, despite of the shortness of the recordings, the asymmetry is clearly visible.

INDICES OF VASCULAR STIFFNESS AND WAVE REFLECTION IN RELATION TO BODY MASS INDEX OR BODY FAT IN HEALTHY SUBJECTS

1 Obesity appears to influence vascular stiffness, an important cardiovascular risk factor. An accurate picture of arterial stiffness may be obtained when a combination of various techniques is used. 2 The purpose of the present study was to assess whether the body mass index (BMI) and body fat content obtained by bioimpedance were of equal value in estimating the influence of body fatness on various indices of vascular stiffness and wave reflection. 3 A total of 175 healthy subjects was studied. Anthropometric measurements and total body bio‐impedance analysis were performed to assess fat mass as a proportion of total body composition. Arterial stiffness and wave reflection were assessed using digital volume pulse analysis and tonometric measurement of the wave reflection indices and central haemodynamics. 4 Significant differences in the stiffness index (SIDVP; P < 0.0001), peripheral augmentation index (pAIx; P < 0.0001), central augmentation index (cAIx; P < 0.0001), peripheral pulse pressure (pPP; P = 0.026) and central pulse pressure (cPP; P < 0.0001) were found when the population examined was divided accordingly to tertile of body fat content. However, subdividing various indices of arterial stiffness according to the tertile of BMI did not reveal any significant differences between groups, except for pPP and cPP. 5 Body fat content was significantly correlated with SIDVP, pAIx, cAIx, pPP and cPP. The BMI correlated weakly with SIDVP, pPP and cPP. 6 In conclusion, the BMI is not very useful in predicting changes in arterial stiffness and wave reflection due to obesity. However, stiffness and wave reflection indices derived from digital volume pulse analysis, the characteristics of radial and aortic pressure waveforms and peripheral and aortic pulse pressure are all related to body fat content, as estimated by bioimpedance.

Asymmetric features of short-term blood pressure variability.

Prolongations of cardiac cycles have a significantly larger contribution to short-term heart rate variability than shortenings—this is called heart rate asymmetry. Our aim is to establish the existence of blood pressure asymmetry phenomenon, which has not been done so far. We used 30-min resting continuous recordings of finger pressure waveforms from 227 healthy young volunteers (19–31 years old; 97 female), and performed Poincaré plot analysis of systolic blood pressure (SBP) to quantify the effect. Median contribution of SBP increases (Ci) to short-term blood pressure variability was 52.8% (inter-quartile range: 50.9–55.1%) and median number of SBP increases (Ni) was 48.8% (inter-quartile range: 47.2–50.1%). The Ci>50% was found in 82% (P<0.0001; binomial test) and Ni<50% in 75% (P<0.0001) of the subjects. Although SBP increases are significantly less abundant than reductions, their contribution to short-term blood pressure variability is significantly larger, which means that short-term blood pressure variability is asymmetric. SBP increases and reductions have unequal contribution to short-term blood pressure variability at supine rest in young healthy people. As this asymmetric behavior of blood pressure variability is present in most of the healthy studied people at rest, it can be concluded that blood pressure asymmetry is a physiological phenomenon.

The plasma concentration of advanced oxidation protein products and arterial stiffness in apparently healthy adults

Background: Oxidative stress plays an important role in the pathogenesis of atherosclerosis. Advanced oxidation protein products (AOPP) are markers of oxidative stress and mediators of inflammation. Increased arterial stiffness is associated with increased risk of cardiovascular mortality and morbidity. The aim of this study was to evaluate the relationship between an indirect marker of arterial stiffness and the AOPP level in apparently healthy individuals. Methods and results: Arterial stiffness was estimated with the use of the stiffness index (SIDVP) which significantly correlated with age, mean blood pressure, body fat content and AOPP. The SIDVP was associated with AOPP concentration in both single (R = 0.22, p = 0.03) and multiple regression models adjusted for age, sex, mean blood pressure and body fat content (R2 = 42%, p < 0.0001). Conclusions: The AOPP concentration is elevated in healthy people with increased values of stiffness index. This finding supports the concept that oxidative stress may contribute to arterial stiffening in humans.

Noninvasively assessed pulsatility of ascending aortic pressure waveform is associated with the presence of coronary artery narrowing

Several hemodynamic indices, measured invasively in the ascending aorta during routine angiography, are related to the presence and severity of coronary atherosclerosis. Radial artery tonometry, when combined with a validated transfer function, offers the possibility of noninvasive assessment of central arterial pressure. We aim to evaluate the association between noninvasive indices of aortic or radial pressure waveforms and the presence of a significant coronary stenosis. Patients who underwent elective coronary angiography were studied (110 men, 91 women, mean age 53 ± 0.9 years). Noninvasive measurement of their central hemodynamics was performed by analysis of the aortic pressure waveform derived from the radial artery. An increase in aortic fractional pulse pressure was associated with coronary artery narrowing or previous myocardial infarction. After multivariate adjustment, the odds ratio and confidence intervals (CI) of having a significant coronary aortic stenosis was 1.72 (95% CI, 1.1–2.7) and of previous myocardial infarction 1.6 (95% CI, 1.1–2.2). An increase in noninvasively assessed aortic fractional pulse pressure, but not of the peripheral index is significantly associated with the presence of coronary artery disease.

Pulse pressure amplification in relation to body fatness

WHAT IS ALREADY KNOWN ABOUT THIS SUBJECT Aortic-brachial pulse pressure amplification (PPA) is a measure of arterial elasticity and it is also an independent cardiovascular risk factor. The PPA is mainly determined by age, height, central and peripheral pressure waveforms characteristics, including measures of arterial stiffness and wave reflection. WHAT THIS STUDY ADDS In this study, however, we demonstrate that PPA is also significantly associated with indirect indices of body fatness. As the body fatness is treatable, our findings might be used as a reference for future studies on the effects of body fat reduction on PPA and the PPA-related cardiovascular risk. AIMS Arterial pressure transfer to the periphery is accompanied by pulse pressure amplification (PPA). Pulse pressure is influence by body fat. The purpose of the present study was to evaluate any possible inter-relation between body fatness and PPA in healthy subjects. METHODS Haemodynamic and wave reflection indices were estimated by pulse wave analysis. Body fat was measured by bio-impedance. RESULTS A total of 367 healthy volunteers (136 men and 231 women) was studied. Pulse pressure amplification correlated significantly with percentage of body fat (r=-0.53, P < 0.0001), age (r=-0.62, P < 0.0001), height (r= 0.43, P < 0.0001), heart rate (r= 0.28, P < 0.0001) and mean blood pressure (r=-0.29, P < 0.0001). The association of PPA with body fat was also significant in a multiple linear regression model. Age was an independent predictor of PPA and analysis of study subjects subdivided into two groups, those <50 years and those >50 years showed that body fatness correlated inversely and significantly with PPA in individuals both younger and older than 50 years (r=-0.44, P < 0.0001, r=-0.37, P < 0.0001 respectively). Augmentation pressure was also associated significantly with percentage of body fat in both subgroups (r= 0.48, P < 0.0001 and r= 0.49, P < 0.0001 respectively). CONCLUSIONS This study performed on healthy subjects showed that pulse pressure amplification is related to body fatness over a wide age range. Percentage body fat is significantly associated with augmentation pressure, a component of central pulse pressure.

Arterial stiffness, central hemodynamics and wave reflection in normal pregnancy and control nonpregnant women

OBJECTIVES Pregnancy is accompanied by different physiological adaptations in the cardiovascular system. However, information on central blood pressures, wave reflection, arterial stiffness in uncomplicated pregnancy compared with nonpregnant women is limited. STUDY DESIGN Forty-six women (mean age 28 years) in the third trimester of pregnancy and 45 healthy age- and height-matched controls were evaluated. Arterial stiffness, central hemodynamics and wave reflection was assessed with the use of digital volume pulse analysis and pulse wave analysis. RESULTS In comparison with nonpregnant participants, pregnant women had significantly lower mean (p=0.04) and central systolic (p=0.02) blood pressure, central pulse pressure (p=0.02), augmentation index (p=0.02) and augmentation pressure (p=0.002), whereas their pulse pressure amplification was significantly higher (p=0.001). Similarly, arterial stiffness index was higher in pregnant women than in healthy nonpregnant controls (p=0.006). This index was correlated significantly with central augmentation index and augmentation pressure (r=0.5, p=0.0005 and r=0.52, p=0.0002, respectively) but only in nonpregnant women. CONCLUSIONS Healthy pregnancy is associated with increased pulse pressure amplification as well as diminished wave reflection, which results in lower central augmentation index and augmentation pressure. Women in the third trimester of pregnancy have slightly higher arterial stiffness in comparison with healthy nonpregnant, age- and height-matched controls. The increased value of measures of arterial stiffness might be secondary to a known physiological increase of cardiac output and the amount of circulating blood.

Cardiopulmonary resonance at 0.1 Hz demonstrated by averaged Lomb-Scargle periodogram

We demonstrate the resonant-like behaviour of the cardiopulmonary system in healthy people occurring at the natural low frequency oscillations of 0.1 Hz, which are often visible in the continuous pressure waveform. These oscillations represent the spontaneous oscillatory activity of the vasomotor centre and are sometimes called the Mayer waves. These 10-second rhythms probably couple with forced breathing at the same frequency and cause the observed cardiopulmonary resonance phenomenon. We develop a new method to study this phenomenon, namely the averaged Lomb-Scargle periodogram method, which is shown to be very effective in enhancing common frequencies in a group of different time series and suppressing those which vary between datasets. Using this method we show that in cardiopulmonary resonance the cardiopulmonary system behaves in a very similar way to a simple mechanical or electrical oscillator, i.e. becomes highly regular and its averaged spectrum exhibits a clear dominant peak and harmonics. If the forcing frequency is higher than 0.1 Hz, the total power and the share of power in the dominant peak and harmonics are lower and the prominence of the dominant peak and its harmonics greatly diminishes. It is shown that the power contributions from different forcing frequencies follow the resonance curve.

Add-On Therapy with a Nighttime Dose of Doxazosin in Patients with Uncontrolled Hypertension: Effects on Autonomic Modulation of the Cardiovascular System

This study was designed to determine whether or not the addition of a single nighttime dose of doxazosin in extended-release form (GITS; gastrointestinal therapeutic system) would affect the autonomic modulation of the cardiovascular system in patients with uncontrolled hypertension treated with a multi-drug regimen. Resting 5-min noninvasive finger blood pressure and ECG signals, as well as 24-h Holter ECGs, were recorded in 30 patients with uncontrolled hypertension on multi-drug treatment before and after 16-week add-on therapy with doxazosin GITS. Cardiovascular autonomic modulation was evaluated by spectral analysis of heart rate variability (HRV) and a cross-correlation method for spontaneous baroreflex sensitivity (BRS) in 5-min resting recordings, and by the analysis of Poincaré plots and phase-rectified signal averaging of the duration of cardiac cycles in 24-h ECG recordings. This combined therapy significantly reduced systolic pressure (19.4±3.5 mmHg; p<0.0001), diastolic blood pressure (9.4±2.0 mmHg; p=0.0003), and pulse pressure (10.0±2.8 mmHg; p=0.0021). Concomitantly, there was a significant increase in resting spontaneous BRS (p=0.0191) and increases in 24-h short-term (p=0.0129) and total (p=0.0153) HRV, but with no significant change in heart rate or other measures of HRV. The improvements in HRV and BRS were observed mainly in patients already treated with thiazide diuretics. There was a significant association (r=0.49; p=0.0065) between the degree of change in diastolic blood pressure and short-term HRV caused by the combined treatment. The addition of 4 mg doxazosin GITS to multi-drug antihypertensive therapy is associated with an improvement in cardiovascular autonomic control.

Measures of Heart Rate Variability in 24-h ECGs Depend on Age but Not Gender of Healthy Children

Many methods computing heart rate variability (HRV) have been applied in studies in children. Not all of these methods have a comprehensive physiological interpretation, and not all of studies are in agreement with the Task Force Standards on HRV from 1996, and the New Joint Position Statement on the advances of HRV from 2015. The study aim was to analyse HRV in the 24-h ECGs of healthy children by the Poincare plots and Lomb-Scargle periodograms, and to follow proper HRV recommendations. Additionally, we investigated the associations between age, childrens sex and measured HRV indices. One hundred healthy children, aged 3–18 underwent 24-h ECG Holter monitoring. HRV was analyzed by the Poincaré plots and spectral by Lomb-Scargle periodograms of RR intervals. The Mann-Whitney test was used to compare sex differences in HRV, the van Elterens test was used to correct for the age-gender interaction, and non-parametric Spearman correlation was applied to analyse the association between age and HRV indices. None of the HRV measures differed significantly between boys and girls. None of the HRV indices was modified by the age-gender interaction. There were statistically significant associations of age with measures of ultra-low (rho = 0.42; p < 0.0001), very low (rho = 0.35; p = 00004) and low (rho = 0.30; p = 0.0028) frequency powers, the ratio of the low to high frequency power (rho = 0.38; p = 0.0001), indices of long-term (SD2; rho = 0.37; p = 0.0002) and total (SDNN; rho = 0.33; p = 0.0008) HRV, and the contribution of the long-term HRV to total HRV (CL; rho = 0.32; p = 0.0012). In general, HRV parameters derived from the analyses of Poincaré plots and Lomb-Scargle periodograms appear not to be affected by gender, however, most of them increase with age in the 24-h ECG recordings in healthy children.