Pavel Leinveber

Dynamic Changes of Left Ventricular Performance and Left Atrial Volume Induced by the Mueller Maneuver in Healthy Young Adults and Implications for Obstructive Sleep Apnea, Atrial Fibrillation, and Heart Failure

Using the Mueller maneuver (MM) to simulate obstructive sleep apnea (OSA), our aim was to investigate acute changes in left-sided cardiac morphologic characteristics and function which might develop with apneas occurring during sleep. Strong evidence supports a relation between OSA and both atrial fibrillation and heart failure. However, acute effects of airway obstruction on cardiac structure and function have not been well defined. In addition, it is unclear how OSA might contribute to the development of atrial fibrillation and heart failure. Echocardiography was used in healthy young adults to measure various parameters of cardiac structure and function. Subjects were studied at baseline, during, and immediately after performance of the MM and after a 10-minute recovery. Continuous heart rate, blood pressure, and pulse oximetry measurements were made. During the MM, left atrial (LA) volume index markedly decreased. Left ventricular (LV) end-systolic dimension increased in association with a decrease in LV ejection fraction. On release of the maneuver, there was a compensatory increase in blood flow to the left side of the heart, with stroke volume, ejection fraction, and cardiac output exceeding baseline. After 10 minutes of recovery, all parameters returned to baseline. In conclusion, sudden imposition of severe negative intrathoracic pressure led to an abrupt decrease in LA volume and a decrease in LV systolic performance. These changes reflected an increase in LV afterload. Repeated swings in afterload burden and chamber volumes may have implications for the future development of atrial fibrillation and heart failure.

Changes in Left and Right Ventricular Mechanics During the Mueller Maneuver in Healthy Adults A Possible Mechanism for Abnormal Cardiac Function in Patients With Obstructive Sleep Apnea

Background—Obstructive sleep apnea is highly prevalent in patients with cardiovascular disease and has detrimental effects on systolic and diastolic function of the ventricles. In this research, the changes in strain (S) and strain rate (SR) during the performance of the Mueller maneuver (MM) in an effort to better understand how negative intrathoracic pressures affect ventricular mechanics. Methods and Results—The MM was performed to maintain a target intrathoracic pressure of −40 mm Hg. Echocardiography was used to measure various parameters of cardiac structure and function. Myocardial deformation measurements were performed using tissue speckle tracking. Twenty-four healthy subjects (9 women; mean age, 30±6 years) were studied. Global left ventricular longitudinal S in systole and SR in early filling were significantly decreased during the MM (S: baseline, −17.0±1.6%; MM, −14.5±2.2%; P<0.0001, SR: baseline, 1.09±0.20 s−1; MM, 0.92±0.21 s−1; P=0.01). Global right ventricular longitudinal S was also significantly decreased during the MM (baseline, −22.0±3.1%; MM, −17.2±2.5%; P<0.0001), as was global right ventricular longitudinal systolic SR (baseline, −1.34±0.35 s−1; MM, −1.02±0.21 s−1; P=0.0006). Conclusions—Left ventricular and right ventricular longitudinal deformation are significantly reduced during the MM. These results suggest that negative intrathoracic pressure during apnea may contribute to changes in myocardial mechanics. These results could help explain the observed changes in left ventricular and right ventricular mechanics in patients with obstructive sleep apnea.

Sleep Disordered Breathing in Patients with the Brugada Syndrome

We investigated breathing patterns and the occurrence of arrhythmias and ST-segment changes during sleep in patients with Brugada syndrome. Patients with Brugada syndrome are more likely to die from ventricular arrhythmias during sleep. ST-segment changes have been correlated with risk of sudden cardiac death. Whether sleep disturbances may contribute to arrhythmogenesis is unknown. Patients with Brugada syndrome underwent overnight polysomnography with simultaneous 12-lead electrocardiographic recording. A control group matched by age, gender, and body mass index (BMI) also underwent polysomnography. Twenty patients were included (50 ± 15 years old, 75% men). Despite their normal BMI (24.7 ± 2.7 kg/m(2)), 45% had sleep-disordered breathing (SDB), with a mean apnea-hypopnea index of 17.2 ± 14 events/hour. In patients with a high risk of arrhythmias, 5 (63%) had SDB. In the control group, 27% had SDB. Atrial or ventricular arrhythmias were not observed. Spontaneous ST-segment changes occurred in 2 patients over 45 different time points. Most ST-segment changes were observed during rapid eye movement sleep (31%) or within 1 minute of arousals (44%). Regarding respiratory events, 25 (56%) of ST-segment changes were related to occurrence of apnea or hypopnea. In conclusion, patients with Brugada syndrome have a high prevalence of SDB even in the setting of normal BMI. The higher incidence of nocturnal death in patients with Brugada syndrome may be conceivably related to co-morbid SDB. Moreover, autonomic instability encountered in rapid eye movement sleep and arousals could potentiate the risk of arrhythmias.

Dynamic coupling between heart rate and ventricular repolarisation

Abstract A novel model for the coupling between ventricular repolarisation and heart rate (QT/RR) is presented. It is based upon a transfer function (TRF) formalism that describes the static and dynamic properties of this coupling, i.e., the behaviour after a sudden change in heart rate. Different TRF models were analysed by comparing their capability to describe experimental data collected from 19 healthy volunteers using several RR stimulation protocols: (i) rest with deep breathing at 0.1 Hz; (ii) tilt with controlled breathing at 0.1 and 0.33 Hz; and (iii) cycling. A search for the best TRF led to unambiguous identification of a three-parameter model as the most suitable descriptor of QT/RR coupling. Compared with established static models (linear or power-law), our model predictions are substantially closer to the experimental results, with errors ∼50% smaller. The shape of the frequency and step responses of the TRF presented is essentially the same for all subjects and protocols. Moreover, each TRF may be uniquely identified by three parameters obtained from the step response, which are believed to be of physiological relevance: (i) gain for slow RR variability; (ii) gain for fast RR variability; and (iii) time during which QT attains 90% of its steady-state value. The TRF successfully describes the behaviour of the RR control following an abrupt change in RR interval, and its parameters may offer a tool for detecting pharmacologically induced changes, particularly those leading to increased arrhythmogenic risk.

Cardiac autonomic control in Brugada syndrome patients during sleep: The effects of sleep disordered breathing☆

AIMS Brugada syndrome is characterized by typical ECG features, ventricular arrhythmias and sudden cardiac death (SCD), more frequent during nighttime. Autonomic cardiovascular control has been implicated in triggering the ventricular arrhythmias. Sleep-disordered breathing (SDB) elicits marked autonomic changes during sleep and is also associated with an increased risk of nighttime SCD. Brugada patients may have a higher likelihood of SDB compared to controls. However, no data are available on cardiac autonomic control in Brugada patients, particularly with regard to the comorbidity of SDB. METHODS We evaluated autonomic cardiovascular control in Brugada patients with SDB (BRU-SDB, n=9), without SDB (BRU, n=9), in controls (CON, n=8) and in non-Brugada patients with SDB (n=6), during wakefulness and sleep (N2, N3 and REM). Linear spectral and entropy-derived measures of heart rate variability (HRV) were performed during apnea-free stable breathing epochs. RESULTS Total HRV was attenuated in BRU-SDB compared to CON and BRU. During N2 and REM, in BRU-SDB patients sympathetic modulation decreased compared to BRU and CON, while during REM, they showed an increased parasympathetic modulation, compared to the other two groups. BRU-SDB and SDB were similar in terms of spectral components. Entropy-derived indices showed preserved dynamic changes in Brugada patients compared to controls through the different sleep stages. CONCLUSION Brugada syndrome per se does not appear associated with an altered autonomic cardiovascular control during wakefulness and sleep. The comorbidity with SDB may contribute to disrupted autonomic cardiovascular regulation during sleep, possibly predisposing to the increased likelihood of sleep-related ventricular tachyarrhythmias and SCD.

Measure of the QT/RR Dynamic Coupling in Patients with the Long QT Syndrome

Background: The patients with the long QT syndrome type‐1 (LQT‐1) have an impaired adaptation of the QT interval to heart rate changes. Yet, the description of the dynamic QT–RR coupling in genotyped LQT‐1 has never been thoroughly investigated.

Prevalence and Predictors of Early Heart Failure With Preserved Ejection Fraction in Patients With Paroxysmal Atrial Fibrillation

BACKGROUND Patients with atrial fibrillation (AF) have an increased risk of diastolic dysfunction and heart failure. The purpose of this study was to identify independent predictors of early (ie, only exercise-induced) heart failure with preserved ejection fraction (HFpEF) and to describe the prevalence of early HFpEF among patients with paroxysmal AF. METHODS AND RESULTS One hundred patients with paroxysmal AF and preserved left ventricular ejection fraction (LVEF) underwent catheterization for left atrial pressure (LAP) measurements at rest and at the peak of arm exercise (LAP-exe). Based on resting and exercise LAP values, the patients were divided into 3 groups. Sixty-one patients had no evidence of HFpEF (LAP at rest ≤15 mm Hg, LAP-exe <25 mm Hg). Twenty-five subjects had early HFpEF (LAP at rest ≤15 mm Hg, LAP-exe ≥25 mm Hg, prevalence 25%). Fourteen patients already had HFpEF at rest (LAP at rest >15 mm Hg). Multivariate exact logistic regression analysis identified age ≥58 years, LAP at rest ≥11 mm Hg, and peak systolic mitral annular velocity ≤9.3 cm/s to be independent predictors of early HFpEF. CONCLUSIONS In patients with paroxysmal AF and preserved LVEF, there appears to be a clinically significant prevalence of early HFpEF.

High prevalence of exercise-induced heart failure with normal ejection fraction in post-heart transplant patients.

AIM Post-heart transplant patients are at increased risk of diastolic dysfunction. The aim of this study was to assess the prevalence of isolated only exercise-induced heart failure with normal ejection fraction (HFNEF) in heart transplant recipients. METHODS AND RESULTS To determine pulmonary capillary wedge pressure (PCWP) at rest and during exercise, 81 patients after orthotopic heart transplantation with normal left ventricular ejection fraction (LVEF) underwent exercise right heart catheterization with simultaneous exercise echocardiography. Based on PCWP values, the patients were divided into three groups. Twenty-one patients had no evidence of HFNEF (PCWP at rest < 15 mmHg, maximal PCWP during exercise < 25 mmHg, prevalence 26%). Forty-seven subjects were found to have only exercise-induced HFNEF (PCWP at rest < 15 mmHg, maximal PCWP during exercise ≥ 25 mmHg, prevalence 58%). Thirteen patients had HFNEF already at rest (PCWP ≥ 15 mmHg at rest, prevalence 16%). Of the noninvasive parameters obtained at rest, multivariate regression analysis identified LV mass index adjusted for allograft age to be an independent predictor of exercise-induced HFNEF. CONCLUSIONS In heart transplant recipients with normal LVEF, there is a high prevalence of exercise-induced HFNEF. LV mass index adjusted for allograft age is predictive of exercise-induced HFNEF.

A multichannel bioimpedance monitor for full-body blood flow monitoring.

Abstract The design, properties, and possible diagnostic contribution of a multichannel bioimpedance monitor (MBM) with three independent current sources are presented in this paper. The simultaneous measurement of bioimpedance at 18 locations (the main part of the body, legs, arms, and neck) provides completely new information, on the basis of which more precise haemodynamic parameters can be obtained. The application of the MBM during various haemodynamic stages, such as resting in a supine position, tilting, exercise stress, and various respiration manoeuvres, is demonstrated. Statistical analysis on a group of 34 healthy volunteers is presented for demonstration of blood flow monitoring by using the proposed method.

Multichannel QRS Morphology Clustering - Data Preprocessing for Ultra-High-Frequency ECG Analysis

Ultra-high-frequency ECG (UHF-ECG) in a range of 500–1,000 Hz has been tested as a new information source for analysis of left-ventricle dyssynchrony and other myocardial abnormalities. The power of UHF signals is extremely low, for which reason an averaging technique is used to improve signal-to-noise ratio. Since ventricle dyssynchrony is different for various QRS complex types, the detected QRS complexes must be clustered into morphology groups prior to averaging. Here, we present a fully-automated method for clustering. The first goal of the method is to separate previously detected QRS complexes into different morphology groups. The second goal is to precisely fit the QRS annotation marks to the exact same position against the QRS shape. The method is based on the Pearson correlation and is optimized for parallel processing. In our application with UHF-ECG data the number of detected groups was 3.24 ± 3.41 (mean and standard deviation over 1,030 records). The method can be used in other areas also where the clustering of repetitive signal formations is needed. For validation purposes, the method was tested on the MIT-BIH Arrhythmia and INCART databases from Physionet with results of purity of 98.24 % and 99.50 %.