pRR30, pRR3.25% and Asymmetrical Entropy Descriptors in Atrial Fibrillation Detection.

BACKGROUND: Early detection of atrial fibrillation (AF) is essential to prevent stroke and other cardiac and embolic complications. We compared the diagnostic properties for AF detection of the percentage of successive RR interval differences greater than or equal to 30 ms or 3.25% of the previous RR interval (pRR30 and pRR3.25%, respectively), and asymmetric entropy descriptors of RR intervals. Previously, both pRR30 and pRR3.25% outperformed many other heart rate variability (HRV) parameters in distinguishing AF from sinus rhythm (SR) in 60 s electrocardiograms (ECGs). METHODS: The 60 s segments with RR intervals were extracted from the publicly available Physionet Long-Term Atrial Fibrillation Database (84 recording, 24 h Holter ECG). There were 31,753 60 s segments of AF and 32,073 60 s segments of SR. The diagnostic properties of all parameters were analysed with receiver operator curve analysis, a confusion matrix and logistic regression. The best model with pRR30, pRR3.25% and total entropic features (H) had the largest area under the curve (AUC)-0.98 compared to 0.959 for pRR30-and 0.972 for pRR3.25%. However, the differences in AUC between pRR30 and pRR3.25% alone and the combined model were negligible from a practical point of view. Moreover, combining pRR30 and pRR3.25% with H significantly increased the number of false-negative cases by more than threefold. CONCLUSIONS: Asymmetric entropy has some potential in differentiating AF from SR in the 60 s RR interval time series, but the addition of these parameters does not seem to make a relevant difference compared to pRR30 and especially pRR3.25%.

MOTS-c Serum Concentration Positively Correlates with Lower-Body Muscle Strength and Is Not Related to Maximal Oxygen Uptake-A Preliminary Study.

The mitochondrial open reading frame of 12S rRNA-c (MOTS-c) is a mitochondrial-derived peptide that regulates the nuclear genome during stressful conditions such as hypoxia, which is typical of exercise and training. We aim to mainly investigate the relationship between serum MOTS-c concentration and muscle strength parameters measured during the countermovement jump test with oxygen consumption (VO2) measured during the cardiopulmonary exercise test to exhaustion. Physically active healthy volunteers (17 male, three female, median age 30 years), not involved in any regular exercise program or participating in any sports competitions, performed five consecutive countermovement jump tests and cardiopulmonary exercise tests until maximal exhaustion and underwent a body composition assessment by means of bioelectrical impedance analysis, and had serum MOTS-c concentration measured at rest. Serum MOTS-c concentration was positively correlated with the average power and average and maximal force of the jumps, both overall muscle mass and leg muscle mass, but not with body fat percentage. There was no correlation with peak VO2. A higher serum MOTS-c concentration is associated with greater muscle mass, force, and power generated during jumping in healthy individuals but not exercise capacity reflected by peak VO2. More studies are needed to better understand the physiological and clinical values of these findings and why MOTS-c is better associated with measures of muscle strength and not endurance in physically active people.

ATPase Inhibitory Factor 1-A Novel Marker of Cellular Fitness and Exercise Capacity?

ATPase inhibitory factor 1 is a myokine inhibiting the hydrolytic activity of mitochondrial adenosine triphosphate synthase and ecto-F1-ATPase on the surface of many cells. IF1 affects ATP metabolism in mitochondria and the extracellular space and upregulates glucose uptake in myocytes; these processes are essential in physical activity. It is unknown whether the IF1 serum concentration is associated with exercise capacity. This study explored the association between resting IF1 serum concentration and exercise capacity indices in healthy people. IF1 serum concentration was measured in samples collected at rest in 97 healthy amateur cyclists. Exercise capacity was assessed on a bike ergometer at the successive stages of the progressive cardiopulmonary exercise test (CPET). IF1 serum concentration was negatively and significantly correlated with oxygen consumption, oxygen pulse, and load at various CPET stages. A better exercise capacity was associated with lower circulating IF1. IF1 may reflect better cellular/mitochondrial energetic fitness, but there is uncertainty regarding how IF1 is released into the intravascular space. We speculate that lower IF1 concentration may reflect a better cellular/mitochondrial integrity, as this protein is bound more strongly with ATPases in mitochondria and cellular surfaces in people with higher exercise capacity.

Non-invasive in vivo human model of post-ischaemic skin preconditioning by measurement of flow-mediated 460-nm autofluorescence.

AIMS: Transient ischaemia and reperfusion (TIAR) induce early ischaemic preconditioning (IPC) in different tissues and organs, including the skin. IPC protects tissues by modifying the mitochondrial function and decreasing the amount of the reduced form of nicotinamide adenine dinucleotide (NADH). Skin 460-nm autofluorescence is proportional to the NADH content and can be non-invasively measured during TIAR. We propose a non-invasive in vivo human model of skin IPC for studying the effects of repeated TIARs on the NADH content. METHODS: Fifty-one apparently healthy volunteers (36 women) underwent three 100-second forearm ischaemia episodes induced by inflation of brachial pressure cuff to the pressure of 60 mmHg above systolic blood pressure, followed by 500-second long reperfusion episodes. Changes in skin NADH content were measured using 460-nm fluorescence before and during each of the three TIARs. RESULTS: The first two TIARs caused a significant reduction in the skin NADH content before (P = .0065) and during the third ischaemia (P = .0011) and reperfusion (P = .0003) up to 3.0%. During the third TIAR, the increase in skin NADH was 20% lower than during the first ischaemia (P = .0474). CONCLUSIONS: The measurement of the 460-nm fluorescence during repeated TIARs allows for a non-invasive in vivo investigation of human skin IPC. Although IPC reduces the overall NADH skin content, the most noticeable NADH reduction appears during ischaemia after earlier TIARs. Studying the skin model of IPC may provide new avenues for in vivo physiological, clinical and pharmacological research on mitochondrial metabolism.

Grip strength is associated with markers of central hemodynamics.

Objectives. Reduced muscular strength (measured by grip strength) has been associated with an increased risk of cardiovascular complications. Further research is needed to identify how muscular strength is associated with various markers of cardiovascular function to provide at least some mechanistic explanation for observed interrelations. We, therefore, addressed the question of whether handgrip (HG) strength is associated with descriptors of peripheral and central hemodynamics in the population of healthy individuals. Design. Two hundred thirty-one healthy volunteers (90 men and 141 women, mean age 54 years) were studied. Patients were asked to perform the maximum handgrip trial in the standing position with the dominant arm, using hydraulic hand dynamometer. Applanation tonometry was used to execute the non-invasive assessment of the pressure waveform. Results. HG strength was associated with various markers of hemodynamics and clinical characteristics, e.g. correlated significantly and positively with BMI [body mass index, r = 0.21, p = .001], PPA [pulse pressure amplification, r = 0.43, p < .0001], Tr [time to return of pressure wave, r = 0.43, p < .0001] and significantly and negatively with AP [augmentation pressure, r = -0.45, p < .0001]. Multiple linear regression showed that sex, handgrip and mean blood pressure were independently associated with AP (R2 = 0.38), PPA (R2 = 0.21) and Tr (R2 = 0.29). Conclusions. Our study demonstrated the association between handgrip strength and central hemodynamic metrics. These interactions may add a mechanistic explanation for the role of muscle strength as a risk marker for incident cardiovascular complications.

Cardiovascular Function in Obstructive Sleep Apnea Patients with Controlled Hypertension.

This study investigated hemodynamic characteristics of obstructive sleep apnea (OSA) accompanied by hypertensive disease in obese men, in whom blood pressure was pharmacologically controlled within the normal range, not exceeding 140/90 mmHg. There were 21 severe OSA patients (mean age 54.1 ± 9.3 years, apnea-hypopnea index of 47.1 ± 18.8 episodes per hour) included in the study, in whom OSA was diagnosed with polysomnography. The control group consisted of healthy normotensive age-matched subjects. Hemodynamic profile was recorded nonivasively with impedance cardiography. Brachial blood pressure and radial artery tonometry were performed to capture and reconstruct peripheral radial and central aortic pressure waveforms in both groups of subjects. Compared to healthy men, OSA patients had a significantly higher body mass index (BMI); the mean increase in BMI amounted to 6.4 ± 1.2 kg/m2. The patients also presented significant differences in the hemodynamic profile. The difference consisted of a faster heart rate, higher peripheral pulse pressure, and reduced blood flow acceleration and velocity indices, describing myocardial contractility. Notably, the significance of hemodynamic differences in OSA patients disappeared in the analysis adjusted for the outstanding increase in BMI. In conclusion, the findings strongly suggest that obesity rather than the hypertensive disease per se is a source of hemodynamic consequences in OSA patients.

Relative Consistency of Sample Entropy Is Not Preserved in MIX Processes.

Relative consistency is a notion related to entropic parameters, most notably to Approximate Entropy and Sample Entropy. It is a central characteristic assumed for e.g., biomedical and economic time series, since it allows the comparison between different time series at a single value of the threshold parameter r. There is no formal proof for this property, yet it is generally accepted that it is true. Relative consistency in both Approximate Entropy and Sample entropy was first tested with the M I X process. In the seminal paper by Richman and Moorman, it was shown that Approximate Entropy lacked the property for cases in which Sample Entropy did not. In the present paper, we show that relative consistency is not preserved for M I X processes if enough noise is added, yet it is preserved for another process for which we define a sum of a sinusoidal and a stochastic element, no matter how much noise is present. The analysis presented in this paper is only possible because of the existence of the very fast NCM algorithm for calculating correlation sums and thus also Sample Entropy.

Pulse wave velocity to the global longitudinal strain ratio in survivors of myocardial infarction.

BACKGROUND: New index of pulse wave velocity to global longitudinal peak systolic strain (PWV/GLPSS) was reported to be associated with cardiovascular damage. We evaluated the prognostic role of this metric in survivors of acute myocardial infarction (AMI). MATERIAL AND METHODS: We investigated in 569 patients with AMI, whether PWV/GLPSS was associated with a composite endpoint of death, stroke or new myocardial infarction, in long-term follow-up. Left ventricular longitudinal strain was evaluated by speckle tracking, and carotid arterial stiffness (local PWV) was determined using radiofrequency data technology. RESULTS: During follow-up (median 1316 days), 114 subjects reached composite endpoint. These subjects were significantly older (P < 0.0001) and were characterized by lower ejection fraction (P < 0.0001), lower GLPSS (P < 0.0001), higher PWV (P = 0.007) and lower PWV/GLPSS index (P < 0.0001). Patients with PWV/GLPSS <-0.74 were at a significantly higher risk for the composite endpoint during the follow-up (hazard rate: 1.7; 95% confidence interval: 1.2-2.6; P < 0.001). The PWV/GLPSS was additive to the predictive value of EF < 35%-patients with PWV/GLPSS <-0.74 and EF < 35% had the highest risk for the endpoint events. CONCLUSIONS: The current study shows that PWV/GLPSS index has significant, independent and additive value in predicting CV complications, in subjects with myocardial infarction.

Association of left atrial fibrosis with aortic excess pressure and white matter lesions.

Objectives. Left atrial fibrosis represents a substrate for atrial fibrillation (AF) and cardioembolic events. White matter hyperintensities (WMH) are commonly found on magnetic resonance imaging (MRI) and are regarded, at least partly as ischemic brain lesions. Aortic excess pressure (excessPTI) represents an extra work performed by the left ventricle and is a new risk metric associated with cardiovascular complications. The aim of our study was to assessed whether there is a correlation between the degree of LA fibrosis, aortic excess pressure, and WMH in patients without a history of atrial fibrillation but the presence of risk factors for cardiovascular complications. Design. Thirty-eight subjects (10, females, 28 males, median age 64 years) with risk factors (hypertension, diabetes, heart failure, vascular disease) but no history of AF were recruited. Left atrial fibrosis and brain WMH were estimated by MRI. Aortic excess pressure was obtained non-invasively. Results. Atrial fibrosis correlated significantly with aortic excess pressure (r = 0.65, p < .0001) and was significantly associated with periventricular white matter lesion volume (r = 0.34, p = .036). In multiple regression analysis, atrial fibrosis and age were positively associated with periventricular white matter lesions, while aortic excess pressure was not quite significant associated with WMH. This model explains the 30% variance in white matter lesions volume observed in the study. Left atrial fibrosis was independently associated with excessPTI but not with age and mean BP. This model explained 42% of the variance in an area of atrial fibrosis. Conclusions. Atrial fibrosis in subjects with cardiovascular risk factors and no history of AF is associated with white matter hyperintensities and aortic excess pressure.

Airway Obstruction in Sleep Apnea Patients.

Obstructive sleep apnea (OSA) is a condition of breathing pathology occurring during sleep, characterized by repeated episodes of upper airway obstruction. The aim of the study was to determine the occurrence of airway obstruction in smoking males with OSA in whom lung function tests had not been performed before. One hundred and four current smokers selected from 1241 patients were enrolled for the research. The subjects included in the study smoked minimum 20 cigarettes a day for at least 10 years. The diagnosis of OSA was confirmed by polysomnography (PSG) in the Sleep Laboratory and subjects were assigned to one of three groups, depending on the severity of OSA. The control group consisted of 30 age-matched male smokers in whom OSA was not confirmed in PSG. Patients from the study and control group scored ≥ 11points in the Epworth Sleepiness Scale. Spirometry, impulse oscillometry, and body plethysmography were used to assess pulmonary function. Airflow limitation in subjects of the control group and OSA patients was confirmed. There were no significant differences in the incidence of bronchial obstruction between the control and study groups, and among the patients of various OSA severity. We conclude that the severity of OSA in smokers does not associate with the presence of airway obstruction. However, the increased peripheral respiratory resistance found in oscillometry did relate to a longer smoking time in OSA patients.

Clinical stage of acquired immunodeficiency syndrome in HIV-positive patients impacts the quality of the touch ECG recordings.

INTRODUCTION: HIV patients are at higher risk for cardiovascular disease and cardiac arrhythmias which can be recorded by a handheld single­lead ECG device. Quality of ECG depends on the skin condition, which worsens with the progression of HIV infection. OBJECTIVE: To study the quality of the ECG signal acquired by a mobile ECG device in patients with different clinical stages of human immunodeficiency virus (HIV) infection. PATIENTS AND METHODS: We studied the quality of 30-second single lead ECGs obtained by a handheld ECG device (Kardia; AliveCor Inc., San Francisco, USA) in 263 Kenyan adults (203 women) in various stages of HIV. The recordings were made during routine check-ups at the outpatient clinics. ECG quality was categorized as readable (not interfering with clinical interpretation) or unreadable (impossible clinical interpretation). The progression of the HIV infection was estimated using the World Health Organization AIDS Clinical Staging (WACS) scale, ranging from stage 1 (asymptomatic generalized lymphadenopathy) to stage 4 (wasting syndrome and Kaposi sarcoma). RESULTS: The median age of patients was 46 (39-53) years. ECG was readable in 201 patients (76.4%) and unreadable in 62 (23.6%). The WACS score > 1 was associated with 3.95 odds ratio (95% confidence interval 2.14-7.29; p < 0.0001) for the acquiring an unreadable ECG (univariate logistic regression adjusted to age, sex, body mass index and time since HIV). CONCLUSIONS: ECG quality recorded by a touch ECG device worsens with advancing HIV infection. For this reason, the accuracy of arrhythmia diagnosis by mobile ECG appears to be limited in HIV patients.

The association between irisin and muscle metabolism in different thyroid disorders.

BACKGROUND: Irisin is a new adipo-myokine, encoded by the FNDC5 gene. Currently, there is a discussion regarding the relation between thyroid function and irisin concentration. This prospective study assesses the influence of thyrometabolic changes on serum irisin concentration in association with altered muscle metabolism. This is performed on a large cohort of patients affected by severe hypo- or hyperthyroidism, as well as by the expression of the FNDC5 gene in thyroid tissue affected by different pathologies. METHODS: The study group comprised 119 patients with newly diagnosed severe hyperthyroidism or hypothyroidism, and a control group of 45 healthy subjects. Body composition, serum irisin concentrations, and thyroid-related hormones, creatine kinase, dystrophin and titin concentrations were evaluated. FNDC5 expression was also analysed in tissue samples from 80 patients with nontoxic multinodular goitre, toxic goitre, Graves' disease and papillary thyroid cancer. RESULTS: Irisin concentration was lower in patients with prolonged hypothyroidism. There was a tendency towards lower dystrophin and titin concentrations in patients with hypothyroidism and hyperthyroidism. Restoration of euthyroidism in patients with hypothyroidism resulted in a decreased muscle mass with an increase in irisin concentrations, while the hyperthyroid group showed an increase in fat mass. Statistically significant overexpression of FNDC5 gene was found in patients with toxic goitre as compared to Graves' disease, papillary thyroid cancer and controls. CONCLUSIONS: The presented data support the theory that irisin concentration changes are associated with prolonged hypothyroidism and might primarily constitute the result of prolonged myopathy. These changes are most likely not related to the expression of the FNDC5 gene in the thyroid gland.

Massive J-waves in the context of intracranial hemorrhage.

Transient ST-segment elevation may be caused by conditions other than myocardial ischemia, among them intracranial hemorrhage. Recognition of the underlying etiology of these ST-segment changes is key because of the vastly different therapies used to treat them. We describe the case of a patient with massive transient J-waves and ST-segment elevation in the context of an intracranial hemorrhage.

ECG by mobile technologies.

Mobile electrocardiographs consist of three components: a mobile device (e.g. a smartphone), an electrocardiographic device or accessory, and a mobile application. Mobile platforms are small computers with sufficient computational power, good quality display, suitable data storage, and several possibilities of data transmission. Electrocardiographic electrodes and sensors for mobile use utilize unconventional materials, e.g. rubber, e-textile, and inkjet-printed nanoparticle electrodes. Mobile devices can be handheld, worn as vests or T-shirts, or attached to patient's skin as biopatches. Mobile electrocardiographic devices and accessories may additionally record other signals including respiratory rate, activity level, and geolocation. Large-scale clinical studies that utilize electrocardiography are easier to conduct using mobile technologies and the collected data are suitable for "big data" processing. This is expected to reveal phenomena so far inaccessible by standard electrocardiographic techniques.

Decreased large-artery stiffness in midluteal phase of the menstrual cycle in healthy women of reproductive age.

OBJECTIVES: Sex hormones are specific factors contributing to the regulation of cardiovascular system. Studies on the effects of hormonal fluctuations during the menstrual cycle on hemodynamics and arterial stiffness in young women are limited and provide conflicting results. AIM: The aim of the study was to assess arterial stiffness, peripheral/central blood (pBP and cBP) and pulse (pPP and cPP) pressures throughout the single, natural menstrual cycle (early follicular [EFP], late follicular [LFP] and midluteal [LP] phase). MATERIALS AND METHODS: Forty two healthy regularly menstruating women (28.6±5.1 yrs of age; BMI 22.0±3.5 kg/m2) were evaluated during EFP (Estradiol [E], FSH, LH, PRL, TSH, Testosterone [T], DHEAS, and SHBG), LFP (E, FSH, LH) and LP (Progesterone, E, FSH, LH). Transvaginal ultrasound was performed to confirm ovulatory cycle. Resting radial and aortic BP were assessed noninvasively and continuously using tonometric measurement of peripheral PP wave-PPW (Colin BMP7000, Japan) and on-line reconstruction of central PPW (Sphygmocor Mx, Australia) at EFP, LFP and LP. ANOVA and Friedman test were used in statistical analysis. RESULTS: There were no significant differences in systolic/diastolic BP and PP both at the periphery and at ascending aorta throughout the menstrual cycle. Comparable observations of no interphasal differences were noted for peripheral Augmentation Index (AI). Central AI and augmentation pressure (AP) were significantly lower in LP than in LFP (by 4%; p<0.05 and by 37%; p<0.05, respectively). CONCLUSIONS: We demonstrated significant differences in mechanical properties of large arteries at the midluteal phase of natural menstrual cycle. We conclude that sex hormones may play role in the regulation of arterial stiffness in the reproductive age women.

Visualising and quantifying the usefulness of new predictors stratified by outcome class: The U-smile method.

Binary classification methods encompass various algorithms to categorize data points into two distinct classes. Binary prediction, in contrast, estimates the likelihood of a binary event occurring. We introduce a novel graphical and quantitative approach, the U-smile method, for assessing prediction improvement stratified by binary outcome class. The U-smile method utilizes a smile-like plot and novel coefficients to measure the relative and absolute change in prediction compared with the reference method. The likelihood-ratio test was used to assess the significance of the change in prediction. Logistic regression models using the Heart Disease dataset and generated random variables were employed to validate the U-smile method. The receiver operating characteristic (ROC) curve was used to compare the results of the U-smile method. The likelihood-ratio test demonstrated that the proposed coefficients consistently generated smile-shaped U-smile plots for the most informative predictors. The U-smile plot proved more effective than the ROC curve in comparing the effects of adding new predictors to the reference method. It effectively highlighted differences in model performance for both non-events and events. Visual analysis of the U-smile plots provided an immediate impression of the usefulness of different predictors at a glance. The U-smile method can guide the selection of the most valuable predictors. It can also be helpful in applications beyond prediction.

Sex differences in the associations between right heart structure and peak exercise capacity parameters in amateur cyclists.

Introduction: Right heart changes and their association with exercise capacity, including sex differences, are still being investigated. We analysed right heart structure and its relationship with exercise capacity parameters in amateur cyclists. Materials and methods: A cross-sectional study involving 215 consecutive adult amateur cyclists, who underwent resting transthoracic echocardiography and a cardiopulmonary exercise test (CPET) to exhaustion was performed. Results: The median age of participants was 29 years (IQR 24-37), 71% of them were men. The mean training time was 6 h/week, and 90% participated in vigorous or moderate physical activity. Men had larger right ventricular diameters (basal - RVD1, mid-cavity - RVD2 and longitudinal - RVD3) compared to women (40.9 vs. 37.6 mm, p = 0.0005, 28.7 vs. 26.3 mm, p = 0.03, 92.2 vs. 81.9 mm, p < 0.0001). Indexing for body surface area revealed comparable right atrial volume (RAVI) between sexes (24.1 vs. 22.7 mL/m2). Men achieved higher peak exercise capacity parameters [O2 pulse, oxygen consumption (VO2) and workload] in CPET. Multivariate linear regression models revealed a positive association between peak VO2, workload and O2 pulse with RAVI in women but not with RVD1 or RVD3. Conversely, these parameters showed a positive association with RVD3 and RVD1 but not with RAVI in men. Conclusion: Sex differences exist in the relationship between right heart structural parameters and peak exercise capacity descriptors in amateur cyclists. Better exercise capacity during CPET to exhaustion is associated with greater RAVI in women but a greater RVD1 and RVD3 in men. These findings suggest different mechanisms of right heart adaptation to training in men and women.

Shortening baroreflex delay in hypertrophic cardiomyopathy patients -- an unknown effect of ß-blockers.

AIMS: Hypertrophic cardiomyopathy (HCM) is characterized by left ventricular hypertrophy and impaired diastolic and systolic function. Abnormal sympathetic-parasympathetic balance is a potential stimulus for left ventricular hypertrophy in HCM patients. ß-Blockers are routinely used in HCM for their strong negative inotropic effect; however, these drugs also influence the sympathetic-parasympathetic balance. This study aimed to determine the autonomic control of the cardiovascular system and the autonomic effects of ß-blockers in HCM patients treated or untreated with ß-blockers. METHODS: Among 51 HCM outpatients (18-70 years old; 29 men) there were 19 individuals with no medication and 32 subjects treated with a ß-blocker. Fourteen age- and gender-matched (23-70 years old; nine men) healthy volunteers were enrolled in the control group. Continuous, non-invasive finger blood pressure was recorded during supine rest for 30 min. Autonomic regulation of the cardiovascular system was measured by heart rate variability and spontaneous baroreflex function (cross-correlation sequence method). RESULTS: The mean pulse interval, time domain and spectral measures of heart rate variability and baroreflex sensitivity were comparable between HCM patients, treated or not with ß-blockers, and the control group. However, the delay of the baroreflex was significantly longer in HCM patients who were not treated with ß-blockers [2.0 (1.6-2.3) s] in comparison with HCM patients receiving ß-blockers [1.4 (1.1-1.8) s; P = 0.0072] or control subjects [1.2 (0.8-1.8) s; P = 0.0025]. This delay did not differ between HCM patients treated with ß-blockers and the control group. CONCLUSIONS: Hypertrophic cardiomyopathy not treated with ß-blockers is accompanied by prolonged baroreflex delay. The use of ß-blockers normalizes this delay.

Asymmetry of the variability of heart rate and conduction time between atria and ventricles.

BACKGROUND: Heart rate asymmetry is caused by an unequal contribution of heart rate decelerations and accelerations to heart rate variability. This study evaluates the asymmetric properties of the variability of the AA, HH, VV, AH and HV intervals. METHODS AND RESULTS: We recorded 50 1-min intracardiac ECG tracings from 10 patients (18-66 years old; 8 females) during a routine electrophysiological study. Standard descriptors of variance asymmetry were calculated for all intervals. Nonparametric tests were used for statistical comparisons. The prolongations of VV (P=0.0297), AH (P=0.0133) and HV (P=0.0004) intervals contributed significantly more than their shortenings to their short-term variance. The proportion of recordings with a larger contribution of prolongations than shortenings was significantly different from random for VV (0.66, P=0.0328), AH (0.68, P=0.0154) HV (0.74, P=0.0009). CONCLUSIONS: In addition to heart rate asymmetry (VV interval), the conduction from the atria, through the atrioventricular node, His-Purkinje system to ventricles shows asymmetric properties in 1-min tracings.

Obstructive sleep apnea and heart rate asymmetry microstructure during sleep.

PURPOSE: Heart rate decelerations and accelerations have unequal input to heart rate variability (HRV) and patterns created by consecutive cardiac cycles-this phenomenon is known as heart rate asymmetry (HRA). The analysis of monotonic runs of heart rate decelerations and accelerations provides a detailed insight into the HRA microstructure and thus of HRV. AIM: To evaluate the relation between the severity of obstructive sleep apnea (OSA) and the HRA microstructure during sleep. METHODS: Seventy-eight patients with suspected OSA underwent overnight polysomnography. The 300-min ECGs from the polysomnography were selected and analyzed. The HRA microstructure was quantified by measuring (1) the contribution of monotonic runs of decelerations or accelerations of different lengths to the number of all sinus beats, and (2) the length of the longest deceleration and acceleration runs. RESULTS: There were 19 patients with no/mild OSA (Apnea/Hypopnea Index (AHI) 5.1 ± 2.5/h), 18 with moderate OSA (AHI 21.8 ± 4.0/h) and 41 with severe OSA (AHI 42.8 ± 17.4/h). Patients with severe OSA had significantly reduced deceleration and acceleration runs of length 1 compared to the moderate OSA group, and compared to patients with no/mild OSA they had an increased number of longer runs (from 5 to 10 for accelerations and from 5 to 8 for decelerations; p < 0.05 for all comparisons). The longest acceleration runs were significantly longer in severe OSA group (p < 0.05) than in subjects with no/mild OSA. CONCLUSIONS: HRA microstructure is related with OSA severity. An increased number of longer deceleration and acceleration runs is more common in severe OSA patients.