Determinants of postexercise heart rate recovery in patients with the obstructive sleep apnea syndrome

Heart Rate Recovery: Up to Date in Heart Failure-A Literature Review

The rising prevalence of cardiovascular disease underscores the growing significance of heart failure (HF). Pathophysiological insights into HF highlight the dysregulation of the autonomic nervous system (ANS), characterized by sympathetic overactivity and diminished vagal tone, impacting cardiovascular function. Heart rate recovery (HRR), a metric measuring the heart's ability to return to its baseline rate post-exertion, plays a crucial role in assessing cardiovascular health. Widely applied across various cardiovascular conditions including HF, coronary artery disease (CAD), and arterial hypertension (HTN), HRR quantifies the difference between peak and recovery heart rates. Given its association with elevated sympathetic tone and exercise, HRR provides valuable insights into the perspective of HF, beyond effort tolerance, reaching toward prognostic and mortality indicators. Incorporating HRR into cardiovascular evaluations enhances our understanding of autonomic regulation in HF, offering potential implications for prognostication and patient management. This review addresses the significance of HRR in HF assessment, analyzing recently conducted studies, and providing a foundation for further research and clinical application.

Is Sleep Disordered Breathing Confounding Rehabilitation Outcomes in Spinal Cord Injury Research?

The purpose of this article is to highlight the importance of considering sleep-disordered breathing (SDB) as a potential confounder to rehabilitation research interventions in spinal cord injury (SCI). SDB is highly prevalent in SCI, with increased prevalence in individuals with higher and more severe lesions, and the criterion standard treatment with continuous positive airway pressure remains problematic. Despite its high prevalence, SDB is often untested and untreated in individuals with SCI. In individuals without SCI, SDB is known to negatively affect physical function and many of the physiological systems that negatively affect physical rehabilitation in SCI. Thus, owing to the high prevalence, under testing, low treatment adherence, and known negative effect on the physical function, it is contended that underdiagnosed SDB in SCI may be confounding physical rehabilitation research studies in individuals with SCI. Studies investigating the effect of treating SDB and its effect on physical rehabilitation in SCI were unable to be located. Thus, studies investigating the likely integrated relationship among physical rehabilitation, SDB, and proper treatment of SDB in SCI are needed. Owing to rapid growth in both sleep medicine and physical rehabilitation intervention research in SCI, the authors contend it is the appropriate time to begin the conversations and collaborations between these fields. We discuss a general overview of SDB and physical training modalities, as well as how SDB could be affecting these studies.

Childhood Obesity and its Influence on Sleep Disorders: Kids-Play Study

Background: Sleep disorders are associated with overweight and obese children, and could decrease life quality with limitations to normal daily activities. The purpose of the study is to describe the prevalence of sleep disorders in a cohort of overweight/obese children using respiratory polygraphy. Methods: A descriptive cross-sectional study was conducted in Granada (Spain) on a sample of 98 children with overweight or obesity. The presence of sleep disorders was determined by respiratory polygraphy. Results: Regarding apnoea–hypopnea-index (AHI) results, 44% of affected children had severe sleep apnoea–hypopnea syndrome (SAHS), and the remaining 56% had a mild form of the disorder. With respect to oxygen-desaturation index, 56% of the same group had severe SAHS, 32% had mild SAHS, and the remaining 12% did not suffer from SAHS. Among participants, average scores of 13.8 obstructive apnoea, 7.7 central apnoea, and 13.6 hypopnoea were recorded. Conclusions: Respiratory polygraphy can provide conclusive results in the diagnosis of SAHS in overweight/obese children. Interventional programmes designed and implemented to reduce overweight and obesity can improve quality of sleep and life in children.

Epicardial fat accumulation is an independent marker of impaired heart rate recovery in obese patients with obstructive sleep apnea

BACKGROUND

Sympathetic nervous system activation plays a pivotal role in obese patients with obstructive sleep apnea (OSA), contributing to increased cardiovascular risk. Epicardial adipose tissue (EAT) activates cardiac autonomic nervous system. Our main study objective was to investigate effects of these autonomic dysfunction factors on post-exercise heart rate recovery (HRR).

METHODS

36 patients, referred for clinical assessment of obesity (BMI > 30 kg/m²), underwent overnight polysomnography, transthoracic echocardiography and cardiopulmonary exercise testing.

RESULTS

Compared to non-OSA patients, OSA patients were older and displayed reduced body weight-indexed peak VO₂. Cardiac output at peak exercise was similar among groups. Peak exercise arterio-venous oxygen content difference D[a-v]O₂ was lower in OSA patients. In univariate linear analysis, age, AHI, EAT thickness, peak VO₂ and diabetes were associated with blunted HRR. Multiple linear regression analysis showed that increased EAT thickness, AHI and diabetes were independently associated with lower HRR. For identical AHI value and diabetes status, HRR significantly decreased by 61.7% for every 1 mm increase of EAT volume (p = 0.011). If HRR was treated as a categorical variable, EAT [odds ratio (OR) 1.78 (95% confidence interval [CI] 1.19-2.66); p = 0.005], and type 2 diabetes [OR 8.97 (95% CI 1.16-69.10); p = 0.035] were the only independent predictors of blunted HRR.

CONCLUSIONS

Aerobic capacity and peak exercise D[a-v]O₂ are impaired in obese OSA patients, suggesting abnormal peripheral oxygen extraction. EAT thickness is an independent marker of post-exercise HRR, which is a noninvasive marker of autonomic nerve dysfunction accompanying poor cardiovascular prognosis in obese patients.

A clinical approach to obstructive sleep apnea as a risk factor for cardiovascular disease

Obstructive sleep apnea (OSA) is associated with cardiovascular risk factors, cardiovascular diseases, and increased mortality. Epidemiological studies have established these associations, and there are now numerous experimental and clinical studies which have provided information on the possible underlying mechanisms. Mechanistic proof-of-concept studies with surrogate endpoints have been performed to demonstrate that treatment of OSA by continuous positive airway pressure (CPAP) has the potential to reverse or at least to attenuate not only OSA but also the adverse cardiovascular effects associated with OSA. However, no randomized studies have been performed to demonstrate that treatment of OSA by CPAP improves clinical outcomes in patients with cardiovascular risk factors and/or established cardiovascular disease and concomitant OSA. In the present review, we summarize the current knowledge on the role of OSA as a potential cardiovascular risk factor, the impact of OSA on cardiac function, the role of OSA as a modifier of the course of cardiovascular diseases such as coronary artery disease, atrial fibrillation, and heart failure, and the insights from studies evaluating the impact of CPAP therapy on the cardiovascular features associated with OSA.

Heart Rate Recovery as a Preoperative Test of Perioperative Complication Risk

The autonomic nervous system plays important physiologic roles in a variety of organ systems. Autonomic dysfunction has been shown to be predictive of increased mortality in patients with cardiovascular disease. Its importance in patients with chronic respiratory disorders has been described in recent years. Here, we summarize the prognostic value of autonomic dysfunction, as reflected by impaired heart rate recovery (HRR), in patients with chronic respiratory disorders, including chronic obstructive pulmonary disease, interstitial lung disease, and lung cancer. We suggest that HRR may be clinically useful in the preoperative physiologic evaluation, specifically in lung cancer patients being considered for surgery.

Sleep and exercise: a reciprocal issue?

Sleep and exercise influence each other through complex, bilateral interactions that involve multiple physiological and psychological pathways. Physical activity is usually considered as beneficial in aiding sleep although this link may be subject to multiple moderating factors such as sex, age, fitness level, sleep quality and the characteristics of the exercise (intensity, duration, time of day, environment). It is therefore vital to improve knowledge in fundamental physiology in order to understand the benefits of exercise on the quantity and quality of sleep in healthy subjects and patients. Conversely, sleep disturbances could also impair a person's cognitive performance or their capacity for exercise and increase the risk of exercise-induced injuries either during extreme and/or prolonged exercise or during team sports. This review aims to describe the reciprocal fundamental physiological effects linking sleep and exercise in order to improve the pertinent use of exercise in sleep medicine and prevent sleep disorders in sportsmen.

Heart rate recovery post 6-minute walking test in obstructive sleep apnea: cycle ergometry versus 6-minute walking test in OSA patients

PURPOSE

To examine the clinical usefulness of heart rate recovery (HRR) post 6-minute walking test (6MWT) as a simple marker of cardiovascular risk in obstructive sleep apnea (OSA) patients in comparison to HRR post cycle ergometry, the validated and more sophisticated protocol.

METHODS

Seventy-four participants underwent full overnight polysomnography, cycle ergometry and 6MWT. The HRR at 1, 2 and 3 min (HRR-1, HRR-2 and HRR-3) 6MWT was compared to HRR at 1, 2, and 3 min post cycle ergometry in normal subjects and in moderate and severe OSA patients before and after 6-month CPAP treatment.

RESULTS

The HRR-1, HRR-2 and HRR-3 in 6MWT were significantly different between normal, moderate and severe OSA patients with higher rates achieved in normal. The higher the severity of OSA the lower the HRR was. There were also no differences found between work rate and distance walked during cycle ergometry or 6MWT, respectively, concerning normal, moderate and severe OSA patients. Heart rate recovery was further associated with minimum saturation of oxygen during sleep independently of the duration of apnea episodes of BMI and ESS. The treatment with CPAP had a beneficial effect on HRR both post-6MWT and post cycle ergometry.

CONCLUSIONS

Autonomic nervous system dysfunction in OSA can be found even with submaximal exertion. Heart rate recovery post-6MWT, such as HRR post cycle ergometry, was significantly impaired in OSA patients in comparison to normals and was favorably influenced from CPAP treatment. Furthermore, it was found to be more sensitive compared with distance walked in 6MWT in discriminating severity of OSA. The HRR post-6MWT was found to be an easily measured and reliable marker of OSA severity both before and after CPAP treatment.

A hypertensive response to exercise is prominent in patients with obstructive sleep apnea and hypertension: a controlled study

Blood pressure (BP) behavior during exercise is not clear in hypertensive patients with obstructive sleep apnea (OSA). The authors studied 57 men with newly diagnosed essential hypertension and untreated OSA (apnea-hypopnea index [AHI] ≥5) but without daytime sleepiness (Epworth Sleepiness Scale score ≤10), and an equal number of hypertensive controls without OSA matched for age, body mass index, and office systolic BP. All patients underwent ambulatory BP measurements, transthoracic echocardiography, and exercise treadmill testing according to the Bruce protocol. A hypertensive response to exercise (HRE) was defined as peak systolic BP ≥210 mm Hg. Patients with OSA and control patients had similar ambulatory and resting BP, ejection fraction, and left ventricular mass. Peak systolic BP was significantly higher in patients with OSA (197.6±25.6 mm Hg vs 187.8±23.6 mm Hg; P=.03), while peak diastolic BP and heart rate did not differ between groups. Furthermore, an HRE was more prevalent in patients with OSA (44% vs 19%; P=.009). Multiple logistic regression revealed that an HRE is independently predicted by both the logAHI and minimum oxygen saturation during sleep (odds ratio, 3.94; confidence interval, 1.69-9.18; P=.001 and odds ratio, 0.94; confidence interval, 0.89-0.99; P=.02, respectively). Exaggerated BP response is more prevalent in nonsleepy hypertensives with OSA compared with their nonapneic counterparts. This finding may have distinct diagnostic and prognostic implications.

Heart rate recovery: a practical clinical indicator of abnormal cardiac autonomic function

The autonomic nervous system (ANS) and cardiovascular function are intricately and closely related. One of the most frequently used diagnostic and prognostic tools for evaluating cardiovascular function is the exercise stress test. Exercise is associated with increased sympathetic and decreased parasympathetic activity and the period of recovery after maximum exercise is characterized by a combination of sympathetic withdrawal and parasympathetic reactivation, which are the two main arms of the ANS. Heart rate recovery after graded exercise is one of the commonly used techniques that reflects autonomic activity and predicts cardiovascular events and mortality, not only in cardiovascular system disorders, but also in various systemic disorders. In this article, the definition, applications and protocols of heart rate recovery and its value in various diseases, in addition to exercise physiology, the ANS and their relationship, will be discussed.

A systematic review on heart-rate recovery to monitor changes in training status in athletes

Heart-rate recovery (HRR) has been proposed as a marker of autonomic function and training status in athletes. The authors performed a systematic review of studies that examined HRR after training. Five cross-sectional studies and 8 studies investigating changes over time (longitudinal) met our criteria. Three out of 5 cross-sectional studies observed a faster HRR in trained compared with untrained subjects, while 2 articles showed no change as a result of training. Most longitudinal studies observed a corresponding increase in HRR and power output (training status). Although confounding factors such as age, ambient temperature, and the intensity and duration of the exercise period preceding HRR make it difficult to compare these studies, the available studies indicated that HRR was related to training status. Therefore, the authors conclude that HRR has the potential to become a valuable tool to monitor changes in training status in athletes and less well-trained subjects, but more studies and better standardization are required to match this potential.