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

Impact of Obstructive Sleep Apnea On In-Hospital Outcomes in Patients With Atrial Fibrillation: A Retrospective Analysis of the National Inpatient Sample

Background Obstructive sleep apnea (OSA) is frequently seen with atrial fibrillation (AF) and is associated with increased cardiovascular morbidity, including hypertension, congestive heart failure, ischemic heart disease, and stroke. However, the impact of OSA on in-hospital outcomes of patients with AF is unclear. Methodology All patients aged ≥18 admitted primarily for AF between January 2016 and December 2017 were identified in the National Inpatient Sample database. They were then categorized into those with OSA and those without OSA. The primary outcome was in-hospital mortality. Unadjusted and adjusted analysis was performed on appropriate variables of interest. Results Of 156,521 primary AF hospitalizations, 15% of the patients had OSA. Baseline characteristics revealed no race disparity between the two groups. However, compared to those without OSA, the OSA group was younger and had a significantly higher proportion of males, obesity, heart failure, hypertension, chronic obstructive pulmonary disease, diabetes, and hyperlipidemia. Long-term anticoagulation and inpatient cardioversion were also higher in the OSA group. Following propensity matching, inpatient mortality was similar between the two groups [0.54% in OSA vs. 0.51% in non-OSA; adjusted odds ratio = 1.06 (95% confidence interval = 0.82-1.35)]. Similarly, OSA was not significantly associated with acute kidney injury, cardiac arrest, gastrointestinal bleed, acute stroke, or length of stay. However, the OSA group was less anemic and required fewer in-hospital blood transfusions. Conclusions Although OSA is highly prevalent in AF patients, inpatient mortality and cardiovascular outcomes such as cardiac arrest, stroke, or major bleeding were similar in AF patients with or without concomitant OSA with no significant differences in length of stay.

Cardiac autonomic dynamics during sleep are lost in patients with TIA and stroke

Ischaemic stroke is accompanied by important alterations of cardiac autonomic control, which have an impact on stroke outcome. In sleep, cardiac autonomic control oscillates with a predominant sympathetic modulation during REM sleep. We aimed to assess cardiac autonomic control in different sleep stages in patients with ischaemic stroke. Forty-five patients enrolled in the prospective, multicentre SAS-CARE study but without significant sleep-disordered breathing (apnea-hypopnea index < 15/hr) and without atrial fibrillation were included in this analysis. The mean age was 56 years, 68% were male, 76% had a stroke (n = 34, mean National Institutes of Health Stroke Scale [NIHSS] score of 5, 11 involving the insula) and 24% (n = 11) had a transitory ischaemic attack. Cardiac autonomic control was evaluated using three different tools (spectral, symbolic and entropy analysis) according to sleep stages on short segments of 250 beats in all patients. Polysomnographic studies were performed within 7 days and 3 months after the ischaemic event. No significant differences in cardiac autonomic control between sleep stages were observed in the acute phase and after 3 months. Predominant vagal modulation and decreased sympathetic modulation were observed across all sleep stages in ischaemic stroke involving the insula. Patients with ischaemic stroke and transitory ischaemic attack present a loss of cardiac autonomic dynamics during sleep in the first 3 months after the ischaemic event. This change could represent an adaptive phenomenon, protecting the cardiovascular system from the instabilities of autonomic control, or a risk factor for stroke, which precedes the ischaemic event.

Multi-disciplinary approach to perioperative risk assessment and post-transplant management for liver transplantation in a patient at risk for Brugada syndrome

Brugada syndrome, an autosomal dominant genetic disorder, is characterised by abnormal electrocardiogram findings and increased risk of ventricular tachyarrhythmias and sudden cardiac death. Our report describes the multi-disciplinary perioperative management of a 28-year-old patient presenting to the Duke Transplant Center with a familial sodium channel gene SCN51 mutation concerning Brugada syndrome. We discuss the preparatory work-up, medication review and appropriate post-surgical follow-up for patients undergoing liver transplant surgery with cardiac monitoring.

Sleep Apnea and Sudden Cardiac Death

Sleep plays an integral role in maintaining health and quality of life. Obstructive sleep apnea (OSA) is a prevalent sleep disorder recognized as a risk factor for cardiovascular disease (CVD) and arrhythmias. Sudden cardiac death (SCD) is a common and devastating event. Out-of-hospital SCD accounts for the majority of deaths from cardiac disease, which is the leading cause of death globally. A limited but emerging body of research have further elaborated on the link between OSA and SCD. In this article, we aim to provide a critical review of the existing evidence by addressing the following: What epidemiologic evidence exists linking OSA to SCD? What evidence exists for a pathophysiologic connection between OSA and SCD? Are there electrocardiographic markers of SCD found in patients with OSA? Does heart failure represent a major effect modifier regarding the relationship between OSA and SCD? What is the impact of sleep apnea treatment on SCD and cardiovascular outcomes? Finally, we elaborate on ongoing research to enhance our understanding of the OSA-SCD association.

Cardiac autonomic control during sleep in patients with myotonic dystrophy type 1: the effects of comorbid obstructive sleep apnea

OBJECTIVE

Myotonic dystrophy type 1 (DM1) is a hereditary myopathy characterized by an autosomal dominant inheritance with important cardiovascular and autonomic deregulation. DM1 patients have a high prevalence of obstructive sleep apnea (OSA), but the effects of this comorbidity on cardiovascular autonomic control (CAC) are unknown. The present study aimed to investigate CAC during sleep-wake cycle in DM1 patients, taking into account the effects of OSA comorbidity.

METHOD

Twenty-three patients with a diagnosis of DM1, and a control group, underwent a complete polysomnographic study (PSG). Electrocardiogram and respiration were extracted from PSG, divided according to the sleep stages, and analyzed using spectral analysis (SpA) of heart rate variability (HRV). SpA identified three components: very low frequency (VLF), low frequency (LF), a marker of sympathetic modulation, and high frequency (HF), a marker of vagal modulation.

RESULTS

The results showed that in DM1 patients, the sympathovagal balance shifted towards a vagal predominance during non-rapid eye movement (NREM) sleep and a sympathetic predominance during rapid eye movement (REM) sleep. Second, this preserved cardiac autonomic modulation was not affected by the comorbidity with obstructive sleep apnea syndrome (OSAS). Third, in DM1 patients, OSAS comorbidity was associated with a reduction in HRV during the whole sleep-wake cycle. Lastly, in DM1 patients with OSA, cardiorespiratory coupling was reduced compared to controls.

CONCLUSIONS

DM1 patients had preserved cardiac autonomic dynamics during NREM and REM sleep, and this phenomenon was not affected by the presence of OSA. However, the comorbidity with OSA was characterized by a reduction in total HRV, which is a marker of the ability of autonomic control to respond to stressors stimuli.

Cardiac autonomic control and complexity during sleep are preserved after chronic sleep restriction in healthy subjects

Acute sleep deprivation (SD) alters cardiovascular autonomic control (CAC) and is associated with an increased risk of cardiovascular disorders. However, the effects of partial SD on CAC are unclear. Thus, we aimed to investigate the effects of partial SD on CAC during sleep. We randomized seventeen healthy subjects to a restriction group (RES, n = 8, subjects slept two-thirds of normal sleep time based on individual habitual sleep duration for 8 days and 8 nights) or a Control group (CON, n = 9, subjects were allowed to sleep their usual sleep time). Attended polysomnographic (PSG) studies were performed every night; a subset of them was selected for the analysis at baseline (day 3-D3), the first night after sleep restriction (day 5-D5), at the end of sleep restriction period (day 11-D11), and at the end of recovery phase (day 14-D14). We extracted electrocardiogram (ECG) and respiration from the PSG and divided into wakefulness (W), nonrapid eye movements (REM) sleep (N2 and N3) and REM sleep. CAC was evaluated by means of linear spectral analysis, nonlinear symbolic analysis and complexity indexes. In both RES and CON groups, sympathetic modulation decreased and parasympathetic modulation increased during N2 and N3 compared to W and REM at D3, D5, D11, D14. Complexity analysis revealed a reduction in complexity during REM compared to NREM sleep in both DEP and CON After 8 days of moderate SD, cardiac autonomic dynamics, characterized by decreased sympathetic, and increased parasympathetic modulation, and higher cardiac complexity during NREM sleep, compared to W and REM, are preserved.

Abnormal autonomic nervous system function in rural Thai men: A potential contributor to their high risk of sudden unexplained nocturnal death syndrome

BACKGROUND

Rural compared to urban Thai populations have a higher incidence of sudden unexplained nocturnal death syndrome (SUNDS). This study tests the hypothesis that compared to young urban Thai men, the young rural northeast Thai men display autonomic system dysfunction that may contribute to their relatively high risk to develop SUNDS.

METHODS

Forty-seven healthy second and third year students from Khon Kaen University (20-22years old) were divided into central, urban northeastern, and rural northeastern groups, based on the locality in which they had grown up and in which their parents had lived prior to their birth.

RESULTS

Body weight, body height, serum sodium, serum potassium, fasting blood sugar, glucose tolerance, resting mean arterial pressure, resting heart rate, ulnar nerve conduction velocity, and sympathetic and parasympathetic nervous system activity were not significantly different among the three groups. In contrast, compared to urban northeasterners and central Thais, rural northeasterners displayed low sympathetic and high parasympathetic responses to cold stress and oral saline load; however, baroreflex sensitivity and the autonomic nervous system responses to upright tilt were not significantly different among the three groups. In addition, respiratory rates at rest and in response to upright tilt, cold stress, and oral saline load were not significantly different among the three groups.

CONCLUSIONS

These data indicate that compared to central or urban, individuals from rural origin display decreased sympathetic and increased parasympathetic responses to stresses. These altered responses could predispose the individuals to inappropriate autonomic control during the stresses, including those resulting in SUNDS.

The utility of T-wave alternans during the morning in the summer for the risk stratification of patients with Brugada syndrome

The prognostic value of the seasonal variations of T-wave alternans (TWA) and heart rate variability (HRV), and the seasonal distribution of ventricular fibrillation (VF) in Brugada syndrome (Br-S) is unknown. We assessed the utility of seasonal variations in TWA and HRV for risk stratification in Br-S using a 24-h multichannel Holter electrocardiogram (24-M-ECG). We enrolled 81 patients with Br-S (grouped according to their history of VF, n = 12; syncope, n = 8; no symptoms, n = 61) who underwent 24-M-ECG in all four seasons. Precordial electrodes were attached to the third (3L-V2) and fourth (4L-V2, 4L-V5) intercostal spaces. We determined the maximum TWA (max-TWA) values and calculated HRV during night and morning time periods for all seasons. During a follow-up period of 5.8 ± 2.8 years, 11 patients experienced new VF episodes and there was a peak in new VF episodes in the summer. The VF group had the greatest 3L-V2 max-TWA value during morning time in the summer among the three groups and showed higher 3L-V2 max-TWA value than in the other seasons. The cutoff value for the 3L-V2 max-TWA during morning time in the summer was determined to be 42 µV using ROC analysis (82 % sensitivity, 74 % specificity; p = 0.0006). Multivariate analysis revealed that a 3L-V2 max-TWA value ≥42 µV during morning time in the summer and previous VF episodes were predictors of future VF episodes. The 3L-V2 max-TWA value during morning time in the summer may be a useful predictor of future VF episodes in Br-S.

Sleep, death, and the heart

Obstructive and central sleep apnea have been associated with increased risk of adverse cardiovascular events and mortality. Sympathetic dysregulation occurring as a result of the respiratory disturbance is thought to play a role in this increased risk. Sleep apnea increases the risk of arrhythmias, myocardial ischemia/infarction, stroke, and heart failure, all of which may increase mortality risk. A higher incidence of nocturnal arrhythmias, cardiac ischemia, and sudden death has been noted in subjects with sleep-disordered breathing (SDB). In this review, the association between SDB and each of these conditions is discussed, as well as the potential mechanisms underlying these risks and the effects of treatment of SDB. Particular emphasis is placed on the relationship between SDB and nocturnal atrial and ventricular arrhythmias, myocardial ischemia/infarction and sudden death.

Preserved cardiac autonomic dynamics during sleep in subjects with spinal cord injuries

BACKGROUND

Spinal cord injuries (SCI) are associated with altered cardiovascular autonomic control (CAC). Sleep is characterized by modifications of autonomic control across sleep stages; however, no data are available in SCI subjects on CAC during sleep. We aim to assess cardiac autonomic modulation during sleep in subjects with SCI.

PATIENTS AND METHODS

27 participants with a neurological and radiological diagnosis of cervical (Cerv, n = 12, ie, tetraplegic) and thoracic SCI (Thor, n = 15, ie, paraplegic) and healthy subjects (Controls) were enrolled. Overnight polysomnographic (PSG) recordings were obtained in all participants. Electrocardiography and respiration were extracted from PSG, divided into sleep stages [wakefulness (W), non-REM sleep (NREM) and REM] for assessment of CAC, using symbolic analysis (SA) and corrected conditional entropy (CCE). SA identified indices of sympathetic and parasympathetic modulation and CCE evaluated the degree of complexity of the heart period time series.

RESULTS

SA revealed a reduction of sympathetic and predominant parasympathetic control during NREM compared to W and REM in SCI patients, independent of the level of the lesion, similar to the Controls. In all three groups, complexity of autonomic regulation was higher in NREM compared to W and REM.

CONCLUSIONS

In subjects with SCI, cardiac autonomic control changed across sleep stages, with a reduction of sympathetic and an increase of parasympathetic modulation during NREM compared to W and REM, and a parallel increase of complexity during NREM, which was similar to the Controls. Cardiac autonomic dynamics during sleep are maintained in SCI, independent of the level of the lesion.

Heart rate variability in normal and pathological sleep

Sleep is a physiological process involving different biological systems, from molecular to organ level; its integrity is essential for maintaining health and homeostasis in human beings. Although in the past sleep has been considered a state of quiet, experimental and clinical evidences suggest a noteworthy activation of different biological systems during sleep. A key role is played by the autonomic nervous system (ANS), whose modulation regulates cardiovascular functions during sleep onset and different sleep stages. Therefore, an interest on the evaluation of autonomic cardiovascular control in health and disease is growing by means of linear and non-linear heart rate variability (HRV) analyses. The application of classical tools for ANS analysis, such as HRV during physiological sleep, showed that the rapid eye movement (REM) stage is characterized by a likely sympathetic predominance associated with a vagal withdrawal, while the opposite trend is observed during non-REM sleep. More recently, the use of non-linear tools, such as entropy-derived indices, have provided new insight on the cardiac autonomic regulation, revealing for instance changes in the cardiovascular complexity during REM sleep, supporting the hypothesis of a reduced capability of the cardiovascular system to deal with stress challenges. Interestingly, different HRV tools have been applied to characterize autonomic cardiac control in different pathological conditions, from neurological sleep disorders to sleep disordered breathing (SDB). In summary, linear and non-linear analysis of HRV are reliable approaches to assess changes of autonomic cardiac modulation during sleep both in health and diseases. The use of these tools could provide important information of clinical and prognostic relevance.