Benefit of atrial pacing in sleep apnea syndrome

Treatment of sleep disorders in elderly patients

Sleep disorders are common among the elderly and are associated with diminished quality of life, increased risk for development of psychiatric disorders, inappropriate use of sleep aids, and decreased daytime functioning. The most common and important sleep disorders in the elderly include insomnia, obstructive sleep apnea syndrome, restless legs syndrome, rapid eye movement sleep behavior disorder, and the advanced sleep phase syndrome. In this article, we summarize the current treatment strategies for each of these sleep-related disorders. Before contemplating specific treatments, the authors recommend that more conservative and nonpharmacologic therapies be attempted first because the elderly are more likely to have medication side effects or complications related to surgery. Many sleep problems can be treated by simple sleep hygiene modifications that can be implemented and adopted easily. For others, therapies that specifically consider older adults may be required. For each of the sleep disorders we provide an updated discussion of therapies beginning with diet and lifestyle, pharmacologic treatment, interventional procedures, surgery, assistive devices, physical and speech therapy, exercise, and emerging therapies with specific considerations for older adults.

Radiotherapy to patients with artificial cardiac pacemakers

BACKGROUND

The in vitro studies show that the modern cardiac pacemakers utilising the complementary metal-oxide semi-conductor (CMOS) circuitry can be adversely affected by therapeutic radiation. However, the published clinical data are sparse regarding the safety of radiotherapy delivery to patients with artificial pacemakers. Despite the potential risk of life threatening complications, there are no national guidelines and most radiotherapy departments have no formal clinical risk management strategy in place. A literature review was performed to assess the risks involved in irradiating patients with pacemakers and to identify strategies, which minimise the risk of pacemaker malfunction. Recommendations for radiotherapy departments are made.

CONCLUSION

Modern multi-programmable pacemakers are very sensitive to therapeutic megavoltage irradiation. There is no safe radiation threshold for megavoltage radiation. The low energy kilovoltage X-rays used for radiotherapy simulation cause no pacemaker malfunction. Megavoltage radiation can be safely delivered to patients with cardiac pacemakers provided direct irradiation of pacemakers is avoided, adequate monitoring is done during and after irradiation, and the dose to the pacemaker generator is kept below 2 Gy. Close liaison with cardiologists and a pacemaker clinic is essential and radiotherapy departments should have protocols in place to identify and care for cancer patients with pacemakers.

Sleep disordered breathing and its treatment in congestive heart failure

Sleep disordered breathing (SDB) is a common problem with adverse cardiorespiratory, endocrinological, and endothelial effects. Recent studies demonstrate an even higher prevalence of SDB in congestive heart failure (CHF) than in a randomly selected population, with up to 40% and 11% having Cheyne Stokes respiration-central sleep apnoea and obstructive sleep apnoea-hypopnoea syndromes, respectively. Randomised controlled trials of nocturnal respiratory support for SDB associated with CHF for up to three months demonstrate significant benefits in terms of improvements in left ventricular ejection fraction, markers of sympathetic system activity, and quality of life. Further randomised controlled trials of larger scale and longer duration are required to establish the role and benefit of this intervention for the treatment of this debilitating condition. The evidence for the higher prevalence of SDB in CHF, its pathogenesis, its pathophysiological consequences, and the emerging benefits of respiratory support are reviewed.

Heart failure and sleep apnoea: to sleep perchance to dream

Heart failure and sleep apnoea are major health problems with an increasingly recognized association; evidence suggests that sleep apnoea may play a role in the progression of heart failure. However, confounding factors such as obesity, hypertension and coronary heart disease make this relationship uncertain and an independent correlation remains unproven. Diagnosis of sleep apnoea is suboptimal, as it is often asymptomatic and polysomnography is expensive and time-consuming. A simple and reliable screening protocol is required. All heart failure patients should be considered to be at high risk of sleep apnoea, as this association might be linked to adverse outcome. Continuous positive airway pressure has shown some beneficial effects, but long-term outcome and improvement in survival remains to be demonstrated. Despite recent advances in the understanding of the complex relationship between heart failure and sleep apnoea, there are a number of areas requiring further investigation, which may have important implications for the management and prognosis of a significant number of patients.

Controversies in pacing: Indications and programming

This article reviews controversies in cardiac pacing in four areas: methods to prevent unnecessary right ventricular pacing and optimal ventricular pacing sites in the bradycardia population, pacing for prevention of atrial fibrillation (AF), a novel pacing technique for the treatment of heart failure, and pacing for the treatment of sleep apnea. Frequent right ventricular pacing has been reported to increase the incidence of AF and congestive heart failure. However, many patients with pacemakers for bradycardia have intrinsic atrioventricular conduction most of the time. Optimal programming of pacemakers and new algorithms designed to reduce unnecessary ventricular pacing are discussed. Pacing algorithms for prevention of AF have generally been shown to be ineffective. Atrial antitachycardia pacing has been shown to reduce the burden of atrial tachyarrhythmias in selected patients. Cardiac contractility modulation has recently been reported to be a promising new approach to the treatment of heart failure. Some pacing techniques may be effective in the treatment of sleep apnea but larger, long-term clinical trials are required to demonstrate a significant clinical benefit.

Prenatal nicotine exposure recruits an excitatory pathway to brainstem parasympathetic cardioinhibitory neurons during hypoxia/hypercapnia in the rat: implications for sudden infant death syndrome

Maternal cigarette smoking and prenatal nicotine exposure increase the risk for sudden infant death syndrome (SIDS) by 2- to 4-fold, yet despite adverse publicity, nearly one of four pregnant women smoke tobacco. Infants who succumb to SIDS typically experience a severe bradycardia that precedes or is accompanied by centrally mediated life-threatening apneas and gasping. Although the causes of the apnea and bradycardia prevalent in SIDS victims are unknown, it has been hypothesized that these fatal events are exaggerated cardiorespiratory responses to hypoxia or hypercapnia. Changes in heart rate are primarily determined by the activity of cardiac vagal neurons (CVNs) in the brainstem. In this study, we tested whether hypoxia/hypercapnia evokes synaptic pathways to CVNs and whether these cardiorespiratory interactions are altered by prenatal exposure to nicotine. Spontaneous rhythmic inspiratory-related activity was recorded from the hypoglossal rootlet of 700- to 800-microm medullary sections. CVNs were identified in this preparation by retrograde fluorescent labeling, and excitatory synaptic inputs to CVNs were isolated and studied using patch-clamp electrophysiologic techniques. Hypoxia/hypercapnia did not elicit an increase in excitatory neurotransmission to CVNs in unexposed animals, but in animals that were exposed to nicotine in the prenatal period, hypoxia/hypercapnia recruited an excitatory neurotransmission to CVNs. This study establishes a likely neurochemical mechanism for the exaggerated decrease in heart rate in response to hypoxia/hypercapnia that occurs in SIDS victims.

Atrial overdrive pacing compared to CPAP in patients with obstructive sleep apnoea syndrome

AIMS

Obstructive sleep apnoea (OSA) is associated with oxygen desaturation, blood pressure increase, and neurohumoral activation, resulting in possible detrimental effects on the cardiovascular system. Continuous positive airway pressure (CPAP) is the therapy of choice for OSA. In a recent study, nocturnal atrial overdrive pacing (pacing) reduced the severity of sleep apnoea in pacemaker patients. We compared the effects of CPAP with those of pacing in patients with OSA but without pacemaker indication or clinical signs of heart failure.

METHODS AND RESULTS

Ten patients with OSA on CPAP therapy were studied for three nights by polysomnography. During the nights that followed a night without any treatment (baseline), the patients were treated with CPAP or pacing in a random order. Pacing was performed with a temporary pacing lead. The pacing frequency was 15 b.p.m. higher than the baseline heart rate. The apnoea-hypopnoea index was 41.0 h(-1) (12.0-66.6) at baseline and was significantly lower during CPAP [2.2 h(-1) (0.3-12.4)] compared with pacing [39.1 h(-1) (8.2-78.5)]. Furthermore, duration and quality of sleep were significantly improved during CPAP when compared with pacing.

CONCLUSION

Nocturnal atrial overdrive pacing is no alternative therapeutic strategy to CPAP for the treatment of OSA in patients without clinical signs of heart failure and without conventional indication for anti-bradycardia pacing.

The role of high-frequency jet ventilation in the treatment of Cheyne-Stokes respiration in patients with chronic heart failure

BACKGROUND

Cheyne-Stokes respiration with central sleep apnea (CSR-CSA) is common in patients with severe cardiac failure. Various modes of positive airway pressure have been suggested as treatments. The authors hypothesized that high frequency jet ventilation (HFJV) can improve central sleep apnea in patients with chronic heart failure.

METHODS

Eleven subjects with stable, optimally treated chronic heart failure and Cheyne-Stokes respiration were tested untreated and on four treatment nights in random order: nasal oxygen (4 L/min), continuous positive airway pressure (CPAP) (mean 9.3 cm H(2)O), bilevel positive airway pressure (BiPAP)(mean 12.0/5.3 cm H(2)O), or HFJV(60 approximately 80 breaths per minute) during polysomnography (EMBLA, Flaga, Reykjavik, Iceland).

RESULTS

The apnea-hypopnea index (AHI) declined from 30.9 +/- 8.3/h in untreated night to 23.6 +/- 6.6/h oxygen night and 18.5 +/- 5.0/h CPAP, 14.3 +/- 3.9/h BiPAP, and 20.1 +/- 4.1/h HFJV (all P < 0.001 versus control). There was no significant difference between the AHI of HFJV and that of CPAP (P = 0.541). Arousal index decreased from 31.4+/-13.2/h untreated to 25.0 +/- 7.1/h oxygen and 13.6 +/- 4.7/h CPAP, to 13.7 +/- 4.9/h BiPAP and 14.4 +/- 4.7/h HFJV. HFJV had the similar effect to the other therapeutic groups in arousal index (P > 0.05). There were large increases in slow-wave and rapid eye movement (REM) sleep with HFJV. All subjects preferred HFJV to CPAP.

CONCLUSIONS

One night of therapy with HFJV improved nocturnal breathing pattern and sleep quality in patients with Cheyne-Stokes respiration in chronic heart failure. HFJV therapy for sleep and breathing were the same as those during a nasal CPAP night. A long-term study of the effect of HFJV on cardiovascular function is needed.

Prevalence and treatment of breathing disorders during sleep in patients with heart failure

Heart failure is a highly prevalent disorder, with significant economic impact, and is associated with excess morbidity and mortality. One factor that may contribute to the progressively declining course of heart failure is the occurrence of recurrent episodes of apnea and hypopnea. There are two major kinds of sleep-related breathing disorders: obstructive and central sleep apnea. In patients with heart failure, in contrast to the general population, central sleep apnea is the most common form of sleep-related breathing disorder. Episodes of apnea, hypopnea, and the subsequent hyperpnea cause sleep disruption, arousals, hypoxemia-reoxygenation, hypercapnia/hypocapnia, and changes in intrathoracic pressure. These pathophysiologic consequences of sleep-related breathing disorders have deleterious effects on the cardiovascular system, and may be even more pronounced in the setting of established heart failure and coronary artery disease. Therefore, sleep apnea in heart failure should be treated. Central sleep apnea may be treated with nocturnal supplemental nasal oxygen, theophylline, or nasal-positive pressure devices, such as nasal continuous positive airway pressure (CPAP). The treatment of choice for obstructive sleep apnea is nasal CPAP. Although long-term controlled trials of the effect of treatment of sleep apnea on mortality in patients with heart failure are still pending, treatment of sleep apnea, both obstructive and central, does result in a decrease in sympathetic activity and an improvement in systolic function, which are known surrogates of mortality. Therefore, diagnosis and treatment of sleep-related breathing disorders may increase survival of patients with heart failure.

Sleep x 9: an approach to treatment of obstructive sleep apnoea/hypopnoea syndrome including upper airway surgery

This article provides an overview of the management of the obstructive sleep apnoea/hypopnoea syndrome (OSAHS). Where possible, recommendations are based on a review of the relevant literature. With the exception of nasal continuous positive airway pressure, which is considered in greater detail elsewhere in the series, and certain oral appliances, the efficacy of many proposed treatments for OSAHS is not supported by data from randomised controlled clinical trials. To a considerable extent, treatment recommendations are based on data from uncontrolled studies, case series, consensus guidelines, practice parameters, and other less rigorous forms of evidence.

Atrial Overdrive Pacing in Patients with Sleep Apnea with Implanted Pacemaker

RATIONALE

Atrial overdrive pacing markedly improved sleep-disordered breathing in a recent study.

OBJECTIVES

Using a single-blind, randomized, crossover design, we aimed to reproduce these findings and investigate the possible underlying mechanisms.

METHODS

Twenty ambulatory patients with an implanted pacemaker or cardioverter defibrillator were studied by polysomnography on 3 consecutive nights in a randomized, single-blind, crossover study in which devices were programmed for nonpacing or for overdrive pacing at 7 or 15 beats/minute faster than the mean nocturnal heart rate. Ventilation and biomarkers (urinary norepinephrine excretion, amino-terminal portion of the precursor of brain natriuretic peptide, or NT-proBNP, were also evaluated.

MEASUREMENTS AND MAIN RESULTS

Neither the primary endpoint apnea-hypopnea index, nor the apnea index, oxygen desaturation, ventilation, or biomarkers were affected by the nocturnal atrial overdrive pacing. A small, clinically insignificant, rate-dependent reduction in the hypopnea index was evoked by pacing (nonpacing, 13.4 +/- 1.4; pacing 7, 12.9 +/- 1.4; pacing 15, 10.9 +/- 1.0; p < 0.01, analysis of variance).

CONCLUSIONS

The lack of effect on the apnea-hypopnea index means that atrial overdrive pacing is inappropriate for treating sleep-disordered breathing.

Implantable Pacing Devices and Sleep Apnea: Implications for Diagnosis and Therapy

Sleep apnea has been increasingly recognized for its prevalence and its impact on cardiovascular health. The disorder has considerable impact on cardiovascular disease states, particularly congestive heart failure. Implantable cardiac pacing devices may have a role in both the diagnosis and therapy of sleep apnea, which may be of particular importance given the seemingly wide coprevalence of cardiac disorders and sleep apnea.

Obstructive sleep apnoea and cardiovascular disease

Obstructive sleep apnoea (OSA) leads to both acute and chronic physiological effects on the cardiovascular system. There is now a large amount of evidence showing that OSA is independently associated with a wide spectrum of clinical cardiovascular disease (CVD). Evidence for a causative effect of OSA is strongest for hypertension, but is weaker for other cardiovascular disorders. Large prospective trials are ongoing and when results become available the link between OSA and CVD is likely to be strengthened. Treatment of OSA with continuous positive airway pressure has been shown to improve blood pressure, particularly in those with hypertension, and also left ventricular ejection fraction in those with congestive heart failure. Given the high prevalence of OSA in the community and its effects on the cardiovascular system, symptoms of this disorder should be sought in patients being investigated or treated for CVD.

Alleviation of Central Sleep Apnea by Ventricular Pacing in a Patient with an Implanted Cardioverter Defibrillator

A 75-year-old man with a single chamber cardioverter defibrillator implanted for the management of sustained ventricular tachycardia developing after a healed myocardial infarction was admitted for evaluation of a sleep disorder. Polysomnography confirmed the presence of severe predominant central sleep apnea syndrome. The apnea-hypopnea index score decreased from 43.3 during spontaneous cardiac rhythm to 24.6 during VVI pacing at a rate of 70 beats/min. Ventricular pacing reduced the number of episodes of central sleep apnea/hypopnea without reducing the total sleep time, though it had no effect on episodes of obstructive sleep apnea/hypopnea.

Diagnosis of sleep-related breathing disorders by visual analysis of transthoracic impedance signals in pacemakers

BACKGROUND

Minute ventilation sensors of cardiac pacemakers measure ventilation by means of transthoracic impedance changes between the pacemaker case and the electrode tip. We investigated whether this technique might detect sleep-related breathing disorders.

METHODS AND RESULTS

In 22 patients, analog waveforms of the transthoracic impedance signal measured by the pacemaker minute ventilation sensor over the course of a night were visualized, scored for apnea/hypopnea events, and compared with simultaneous polysomnography. Analysis of transthoracic impedance signals correctly identified the presence or absence of moderate to severe sleep apnea (apnea/hypopnea index, AHI >20 h(-1)) in all patients (receiver operating characteristics, ROC=1.0). The ROC for AHI scores of > or =5 h(-1) and > or =10 h(-1) showed an area under the curve of 0.95, P<0.005, and 0.97, P<0.0001, respectively. Accuracy over time assessed by comparing events per 5-minute epochs was high (Cronbach alpha reliability coefficient, 0.85; intraclass correlation, 0.73). Event-by-event comparison within +/-15 seconds revealed agreement in 81% (kappa, 0.77; P<0.001).

CONCLUSIONS

Detection of apnea/hypopnea events by pacemaker minute ventilation sensors is feasible and accurate compared with laboratory polysomnography. This technique might be useful to screen and monitor sleep-related breathing disorders in pacemaker patients.

Association of atrial fibrillation and obstructive sleep apnea

BACKGROUND

Obstructive sleep apnea (OSA) is associated with recurrent atrial fibrillation (AF) after electrocardioversion. OSA is highly prevalent in patients who are male, obese, and/or hypertensive, but its prevalence in patients with AF is unknown.

METHODS AND RESULTS

We prospectively studied consecutive patients undergoing electrocardioversion for AF (n=151) and consecutive patients without past or current AF referred to a general cardiology practice (n=312). OSA was diagnosed with the Berlin questionnaire, which is validated to identify patients with OSA. We also assessed its accuracy compared with polysomnography in a sample of the study population. Groups were compared with the 2-tailed t, Wilcoxon, and chi2 tests. Logistic regression modeled the association of AF and OSA after adjustment for relevant covariates. Patients in each group had similar age, gender, body mass index, and rates of diabetes, hypertension, and congestive heart failure. The questionnaire performed with 0.86 sensitivity, 0.89 specificity, and 0.97 positive predictive value in our sample. The proportion of patients with OSA was significantly higher in the AF group than in the general cardiology group (49% versus 32%, P=0.0004). The adjusted odds ratio for the association between AF and OSA was 2.19 (95% CI 1.40 to 3.42, P=0.0006).

CONCLUSIONS

The novel finding of this study is that a strong association exists between OSA and AF, such that OSA is strikingly more prevalent in patients with AF than in high-risk patients with multiple other cardiovascular diseases. The coinciding epidemics of obesity and AF underscore the clinical importance of these results.

Cardiac resynchronization therapy improves central sleep apnea and Cheyne-Stokes respiration in patients with chronic heart failure

OBJECTIVES

We studied the effects of cardiac resynchronization therapy (CRT) on heart failure (HF) patients with central sleep apnea (CSA).

BACKGROUND

Patients with advanced HF often suffer from CSA with Cheyne-Stokes respiration. Cardiac resynchronization therapy improves myocardial function and exercise capacity in HF patients with conduction disturbances. The relationship between CRT and CSA is currently unknown.

METHODS

Twenty-four patients (7 females; 62 +/- 11 years) with HF, a reduced left ventricular ejection fraction (24 +/- 6%), and left bundle branch block (QRS duration 173 +/- 22 ms) received a CRT device. The number of apneas and hypopneas per hour (apnea-hypopnea index [AHI]) and minimal oxygen saturation (SaO2min) were quantified by cardiorespiratory polygraphy. Fourteen patients showed CSA (AHI >5/h), and 10 patients had an AHI <5/h without CSA. Subjective sleep quality was assessed by the Pittsburgh Sleep Quality Index (PSQI). Data were evaluated before and after 17 +/- 7 weeks of CRT.

RESULTS

In patients with CSA, CRT led to a significant decrease in AHI (19.2 +/- 10.3 to 4.6 +/- 4.4, p < 0.001) and PSQI (10.4 +/- 1.6 to 3.9 +/- 2.4, p < 0.001) without Cheyne-Stokes respiration and to a significant increase in SaO2min (84 +/- 5% to 89 +/- 2%, p < 0.001). There was no significant change in AHI (1.7 +/- 0.7 to 1.5 +/- 1.6), PSQI (2.4 +/- 0.5 to 2.6 +/- 0.9), and SaO2min (90 +/- 2% to 91 +/- 1%) in patients without CSA.

CONCLUSIONS

Cardiac resynchronization therapy leads to a reduction of CSA and to increased sleep quality in patients with HF and sleep-related breathing disorders. This may have prognostic implications in patients receiving CRT.

Prevalence of sleep apnea syndrome in lone atrial fibrillation: a case-control study

BACKGROUND

According to several studies, obstructive sleep apnea predisposes to cardiac arrhythmias, but the prevalence of sleep apnea in specific arrhythmias has not been determined. Our case-control study assesses prevalence of sleep apnea syndrome (SAS) in lone atrial fibrillation (AF).

METHODS

Patients with AF (n = 59; 48 men and 11 women; mean age, 59 years; age range, 25 to 84 years) without evident cardiovascular diseases, and their 56 gender-matched, age-matched, and cardiovascular morbidity-matched community control subjects underwent an overnight sleep study.

RESULTS

Prevalence of SAS in the AF group was 32%, which did not differ from that in control subjects (29%, p = 0.67). In men, mean neck circumference was higher in the AF group (40.9 cm vs 39.5 cm, p = 0.01) than in control subjects. In men, after adjusting for body mass index and waist circumference, neck circumference was independently related to AF, with an odds ratio (OR) of 1.8 (95% confidence interval, 1.3 to 2.5) per 1-cm increase, and an OR of 5.2 (95% confidence interval, 1.6 to 17.0) for values > 40 cm. Compared to control subjects, the AF group reported more daily/almost-daily tiredness (29% vs 4%, p < 0.001), daily/almost-daily sleepiness (27% vs 7%, p = 0.005), and nightly/almost-nightly breathing pauses during sleep (12% vs 2%, p = 0.03).

CONCLUSIONS

SAS seems to be common in lone AF. Nevertheless, we could not show SAS to be more common in patients with AF than in gender-matched, age-matched, and cardiovascular morbidity-matched community control subjects. Compared to control subjects, men with AF seem to have thicker necks, and patients with lone AF report more daytime tiredness, daytime sleepiness, and breathing pauses during sleep.

Sleep Apnea:. A New Indication for Cardiac Pacing?

In the general adult population, prevalence of sleep apnea syndrome reaches 4% in men and 2% in women. Continuous positive airway pressure is the most efficient treatment. At the present time, although severe atrial bradycardias could occur during sleep apnea episodes, cardiac pacing has not been demonstrated as an efficient treatment for those bradycardias. Treating sleep apnea generally reduces the number of bradyarrhythmias. However, recent studies reported a beneficial effect of atrial pacing on the sleep apnea burden. The mechanisms rely on two phenomena: first to counteract nocturnal hypervagotonia, and second to treat heart failure. By increasing the heart rate, cardiac output improves, which mitigates pulmonary subedema. Consequently, stimulation of the pulmonary afferent vagal fibers is diminished, which reduces central sleep apnea incidence. During nocturnal hypervagotonia, snoring and obstructive apnea episodes are increased, mainly due to an excessive muscular relaxation of the upper airway area inducing cyclical substantial decreases in the airway caliper. In patients with a low heart rate, atrial pacing can counteract hypervagotonia by enhancing the sympathetic tone and modifying the degree of vigilance. Accordingly, in the near future, sleep apnea treatment might potentially rely on atrial pacing in bradycardic patients with hypervagotonia (with or without heart failure). The role of the physician would then be not only to diagnose sleep apnea, but also to identify potential responders to cardiac pacing.

Sleep-disordered breathing in heart failure

Sleep-related breathing disorders are common in heart failure patients and can have significant adverse impact on clinical outcomes. If sleep-disordered breathing or considerable daytime sleepiness exists, assessment and treatment recommendations include the following: 1) carefully assess and correct hemodynamic status; heart failure exacerbations can induce central sleep apneas; 2) if overweight, encourage patient weight loss; 3) elevate head of bed; 4) discourage sleeping on back; 5) order polysomnography, to assess type and extent of sleep-related breathing disorder; and 6) treat sleep-disordered breathing with nasal continuous positive airway pressure or bilevel positive airway pressure.

Reduction of sleep-disordered breathing after physostigmine

The cholinesterase inhibitor physostigmine (PHYS) was investigated in a double-blind, placebo-controlled, randomized, crossover trial of 10 male patients with moderate to severe obstructive sleep apnea. PHYS (0.12 microg/minute/kg, 7-hour infusion) reduced mean apnea/hypopnea index (AHI) by 13.6 (95% confidence interval [CI], 2.2-25.1) corresponding to 21.4% (95% CI, -5.5 to 47.9) and increased minimum SaO2 by 8.7% (95% CI, -0.3 to 17.7) corresponding to 23.2% (95% CI, 4.8-41.3). During the last third of the night, coinciding with predicted plasma concentration steady state, non-REM sleep AHI decreased by 19.2 (95% CI, 0.1-38.3) or 14.9% (95% CI, -43.6 to 77.7) and REM AHI by 33.8 (95% CI, 13.7-54.0) or 67.5% (95% CI, 49.7-85.3). Mean total sleep time was reduced by 74 minutes (95% CI, 33.9-114.9), but patients with the least pronounced sleep shortening had the largest reduction of AHI (r = 0.73, p < 0.02). The nocturnal decline in heart rate was reduced by PHYS. Moreover, resting (early-night placebo heart rate) was positively correlated with proportional reduction of REM apnea index (r = 0.69, p < 0.02). Body mass index was negatively correlated with reduction of REM AHI (r = 0.77, p < 0.02). This, predominantly REM-related, reduction of obstructive sleep apnea after PHYS may provide a new treatment option if the effects are maintained in long-term studies.

Sleep disorders in patients with congestive heart failure

PURPOSE OF REVIEW

This review of recent literature pertains to the growing evidence that obstructive sleep apnea contributes to the development of systemic hypertension and congestive heart failure.

RECENT FINDINGS

There is irrefutable evidence that OSA causes systemic hypertension and that continuous positive airway pressure (CPAP) treatment of OSA causes a reduction in blood pressure. Moreover there is evidence that untreated OSA is associated with left ventricular diastolic and systolic failure and that treatment with CPAP improves systolic function.

SUMMARY

OSA should be considered in patients with systemic hypertension or heart failure.

Central nervous determination of food storage—a daily switch from conservation to expenditure: implications for the metabolic syndrome

Here, we present a neuroendocrine concept to review the circularly interacting energy homeostasis system between brain and body. Body-brain interaction is circular because the brain immediately integrates an input to an output, and because part of this response may be that the brain modulates the sensitivity of this perception. First, we describe how the brain senses the body through neurons and blood-borne factors. Direct neuronal connections report the state of various organs. In addition, humoral factors are perceived by the blood-brain barrier and circumventricular organs. We describe how circulating energy carriers are sensed and what signals reach the brain during food intake, exercise and an immune response. We describe that the brain regulates the homeostatic process at two fundamentally different levels during the active and inactive states. The unbalanced output of the brain in the metabolic syndrome is discussed in relation with such circadian rhythms and with regional activity of the autonomic nervous system. In line with the above, we suggest a new approach for the diagnosis and therapy of the metabolic syndrome.

Apnées du sommeil et stimulation cardiaque : mécanismes d’action et perspectives

In an adult population, the prevalence of sleep apnea is 4% for men and 2% for women. Generally, nasal positive pressure ventilation is the best therapeutic option. To date, and in spite of the possible presence of marked brady-arrhythmias during sleep apnea, there is no recognised indication for Pacemaker implantation. However, recent data show the potential benefit of permanent cardiac stimulation in these patients. Increasing heart rate (using atrial pacing) improves cardiac output, and reduces pulmonary congestion and pulmonary vagal afferent nerves are no longer stimulated. The incidence of central sleep apnea is thereby reduced. Excessive nocturnal vagal tone increases snoring and sleep apnea, because of excessive relaxation of the oropharyngeal muscles. In patients with bradycardia, atrial stimulation may oppose increased vagal tone, by stimulating the sympathetic system or maintaining it at a minimal level. It is therefore possible that cardiac stimulation will become part of the treatment of sleep apnea in patients with documented bradycardia and/or heart failure.

[Cardiovascular consequences of obstructive sleep apnea syndrome]

PURPOSE

This article is an update of past and current data on the relationship between obstructive sleep apnea syndrome and cardiovascular diseases.

CURRENT KNOWLEDGE AND KEY POINTS

Obstructive sleep apnea syndrome is a common, but under-recognised, condition and should not be considered simplistically as the association of snoring and obesity. It may be suspected by the clinical history but a definite diagnosis requires the practice of polysomnography. Numerous studies have found a significant relationship between the presence of obstructive sleep apnea syndrome and the occurrence of cardiovascular events. Nonetheless, a definite causal relationship has only been established for the occurrence of hypertension. There are multiple immediate and delayed cardiovascular responses to the apneic events and thus there are many possible physiopathological mechanisms to explain the association of obstructive sleep apnea and cardiac and vascular events, the primary one being sympathetic hyperactivity. The prognosis of obstructive sleep apnea syndrome is closely related to the incidence of cardiovascular events. FUTURE PROSPECTS AND PROJECS: The existence of an independent relationship between obstructive sleep apnea syndrome and atherosclerosis is not yet demonstrated. The beneficial effects of continuous positive airway pressure, the treatment of choice for this condition, on the incidence of cardiovascular diseases remains to be confirmed although recent studies suggest that correct treatment of obstructive sleep apnea syndrome by continuous positive airway pressure may reduce the cardiovascular risk and in particular that of hypertension.

Sleep-disordered breathing in heart failure: characteristics and implications

Sleep-disordered breathing, namely obstructive sleep apnea (OSA) and central sleep apnea (CSA), are both often encountered in the setting of heart failure (HF), and have distinct differences in terms of prevalence, pathophysiology and consequences. OSA is independently associated with an increased risk for cardiovascular disease and for congestive HF in the general population. It is conceivable that this breathing disorder may have particularly deleterious effects in patients with coexisting heart disease, especially in those with a failing heart. There are considerable data addressing the interaction between OSA and the cardiovascular system, which underscore the importance of an early detection of this breathing disorder, especially in patients with HF. CSA is generally considered a consequence rather than a cause of HF, and is correlated with the severity of hemodynamic impairment. However, when present, it is associated with increased arrhythmic risk and higher cardiac mortality. Potential mechanisms implicated in the genesis of this breathing pattern and the possible therapeutic options, which have been proven to be effective in the clinical setting, are discussed.

Effects of vagus nerve stimulation on sleep-related breathing in epilepsy patients

PURPOSE

To describe the effects of vagus nerve stimulation (VNS) on sleep-related breathing in a sample of 16 epilepsy patients.

METHODS

Sixteen adults with medically refractory epilepsy (nine men, seven women, ages 21-58 years) underwent baseline polysomnograms (PSGs). Three months after VNS therapy was initiated, PSGs were repeated. In addition, patient 7 had a study with esophageal pressure monitoring, and patient 1 had a continuous positive airway pressure (CPAP) trial.

RESULTS

Baseline PSGs: One of 16 patients had an apnea-hypopnea index (AHI) >5 (6.8). Treatment PSGs: Five of 16 patients had treatment AHIs >5. Respiratory events were more frequent during periods with VNS activation (on-time) than without VNS activation (off-time; p = 0.016). Follow-up studies: Esophageal pressure monitoring in patient 7 showed crescendos in esophageal pressure during VNS activation, supporting an obstructive pattern. The CPAP trial of patient 1 showed that all respiratory events were associated with VNS stimulation at low CPAP levels. They were resolved at higher CPAP levels.

CONCLUSIONS

Treatment with VNS affects respiration during sleep and should be used with care, particularly in patients with preexisting obstructive sleep apnea. The AHI after VNS treatment remained <5 in the majority of patients and was only mildly elevated (<12) in five patients. In one patient, CPAP resolved VNS-related respiratory events.

Obstructive sleep apnea and cardiovascular disease

Obstructive sleep apnea (OSA) is a common disorder associated with an increased risk of cardiovascular disease and stroke. As it is strongly associated with known cardiovascular risk factors, including obesity, insulin resistance, and dyslipidemia, OSA is an independent risk factor for hypertension and has also been implicated in the pathogenesis of congestive cardiac failure, pulmonary hypertension, arrhythmias, and atherosclerosis. Obesity is strongly linked to an increased risk of OSA, and weight loss can reduce the severity of OSA. The current standard treatment for OSA-nasal continuous positive airway pressure (CPAP)-eliminates apnea and the ensuing acute hemodynamic changes during sleep. Long-term CPAP treatment studies have shown a reduction in nocturnal cardiac ischemic episodes and improvements in daytime blood pressure levels and left ventricular function. Despite the availability of effective therapy, OSA remains an underdiagnosed and undertreated condition. A lack of physician awareness is one of the primary reasons for this deficit in diagnosis and treatment.

A simple method to identify sleep apnea using Holter recordings

INTRODUCTION

Despite its severe cardiovascular and other consequences, sleep apnea syndrome frequently is undiagnosed. Because apneas result in repeated autonomic arousals associated with cyclic variations in heart rate (CVHR), we hypothesized that sleep apnea syndrome could be identified from simple HR tachograms (graphs of HR vs time) derived from ECG monitoring.

METHODS AND RESULTS

HR tachograms were generated from 57 digitized ECGs (46 clinical patients undergoing diagnostic studies and 11 research subjects) obtained during overnight polysomnography. Thirty-three had significant sleep apnea syndrome (apnea-hypopnea index > or = 15). Eight patients had simultaneous Holter recordings during sleep studies (3 with digitized ECGs and 5 with paper ECGs). Duration of CVHR on tachograms was determined. CVHR patterns were characterized as high amplitude (HR changes > or = 20 beats/min per cycle) versus lower amplitude (6-19 beats/min per cycle); or regular (in frequency, amplitude, and morphology) versus irregular. Tachograms were classified as having visible HR changes versus not visible (flat). Twenty-four studies proved to be split-night, so CVHR was quantified for the first 3 hours of each study only. When subjects were dichotomized into shorter (< 20%, < 36 min) and longer (> or = 20%) durations of CVHR, longer CVHR had a positive predictive accuracy of 86% for significant sleep apnea syndrome and 100% for abnormal sleep. When flat tachograms were excluded, negative predictive accuracy for shorter CVHR was 100%. All patients (N = 13) with > 36 min high-amplitude CVHR had significant obstructive sleep apnea. All predictions from Holter-only data were concordant with clinical diagnoses.

CONCLUSION

HR tachogram patterns derived from ambulatory ECGs provide a simple method for identifying sleep apnea syndrome and other sleep disturbances in patients without major autonomic dysfunction.

Enhanced ventilatory response to exercise in patients with chronic heart failure and central sleep apnea

BACKGROUND

In patients with chronic heart failure (CHF), central sleep apnea (CSA) and enhanced ventilatory response (VE/VCO2 slope) to exercise are common. Both breathing disorders alone indicate poor prognosis in CHF. Although augmented chemosensitivity to CO2 is thought to be one important underlying mechanism for both breathing disorders, it is unclear whether both breathing disorders are related closely in patients with CHF.

METHODS AND RESULTS

We investigated 20 CHF patients with clinically important CSA (apnea-hypopnea-index (AHI), number of episodes per hour >or=15) and 10 CHF patients without CSA. Patients with and without CSA did not differ with respect to exercise capacity (peak VO2, 63.4+/-3.4% versus 60.8+/-4.4% of predicted value; P=0.746) and left ventricular ejection fraction (LVEF, 31+/-2% versus 31+/-3%; P=0.948). The AHI was not correlated with exercise capacity (peak VO2, percent of predicted value; P=0.260) and LVEF (percent, P=0.886). In contrast, the positive correlation of the VE/VCO2 slope, determined by cardiopulmonary exercise testing, with the AHI was highly significant (P<0.001). The VE/VCO2 slope was significantly increased in patients with CSA compared with those without CSA (29.7 versus 24.9; P<0.001).

CONCLUSIONS

The ventilatory response to exercise is significantly augmented in CHF patients with CSA compared with those without. In contrast to peak VO2 and LVEF, the VE/VCO2 slope is strongly related to the severity of CSA in patients with CHF, which underscores an augmented chemosensitivity to CO2 as a common underlying pathophysiological mechanism.

fMRI responses to cold pressor challenges in control and obstructive sleep apnea subjects

Obstructive sleep apnea (OSA) patients exhibit altered sympathetic outflow, which may reveal mechanisms underlying the syndrome. We used functional MRI (fMRI) in 16 control and 10 OSA subjects who were free of cardiovascular or mood-altering drugs to examine neural responses to a forehead cold pressor challenge, which elicits respiratory slowing, bradycardia, and enhanced sympathetic outflow. The magnitude of cold-induced bradycardia was smaller, and respiratory slowing showed greater intersubject variability and reached a nadir later in OSA patients. Both groups showed similar signal changes to cold stimulation in multiple brain sites. However, signal increases emerged in OSA over controls in anterior and posterior cingulate and cerebellar and frontal cortex, whereas signals markedly declined in the ventral thalamus, hippocampus, and insula rather than rising as in controls. Anomalous responses often paralleled changes in breathing and heart rate. Medullary, midbrain areas and lentiform and cerebellar dentate nuclei also showed lower signals in OSA cases. Cold pressor physiological responses are modified in OSA and may result from both diminished and exaggerated responses in multiple brain structures.

Neural responses during Valsalva maneuvers in obstructive sleep apnea syndrome

The repetitive upper airway muscle atonic episodes and cardiovascular sequelae of obstructive sleep apnea (OSA) suggest dysfunction of specific neural sites that integrate afferent airway signals with autonomic and somatic outflow. We determined neural responses to the Valsalva maneuver by using functional magnetic resonance imaging. Images were collected during a baseline and three Valsalva maneuvers in 8 drug-free OSA patients and 15 controls. Multiple cortical, midbrain, pontine, and medullary regions in both groups showed intensity changes correlated to airway pressure. In OSA subjects, the left inferior parietal cortex, superior temporal gyrus, posterior insular cortex, cerebellar cortex, fastigial nucleus, and hippocampus showed attenuated signal changes compared with controls. Enhanced responses emerged in the left lateral precentral gyrus, left anterior cingulate, and superior frontal cortex of OSA patients. The anterior cingulate, cerebellar cortex, and posterior insula exhibited altered response timing patterns between control and OSA subjects. The response patterns in OSA subjects suggest deficits in particular neural pathways that normally mediate the Valsalva maneuver and compensatory actions in other structures.

Diabetes and sleep disturbances: findings from the Sleep Heart Health Study

OBJECTIVE

To test the hypothesis that diabetes is independently associated with sleep-disordered breathing (SDB), and in particular that diabetes is associated with sleep abnormalities of a central, rather than obstructive, nature.

RESEARCH DESIGN AND METHODS

Using baseline data from the Sleep Heart Health Study (SHHS), we related diabetes to 1). the respiratory disturbance index (RDI; number of apneas plus hypopneas per h of sleep); 2). obstructive apnea index (OAI; >or=3 apneas/h of sleep associated with obstruction of the upper airway); 3). percent of sleep time < 90% O(2) saturation; 4). central apnea index (CAI; >or=3 apneas [without respiratory effort]/h sleep); 5). occurrence of a periodic breathing (Cheyne Stokes) pattern; and 6) sleep stages. Initial analyses excluding persons with prevalent cardiovascular disease (CVD) were repeated including these participants.

RESULTS

Of the 5874 participants included in this report, 692 (11.8%) reported diabetes or were taking oral hypoglycemic medications or insulin and 1002 had prevalent CVD. Among the 4872 persons without CVD, 470 (9.6%) had diabetes. Diabetic participants had worse CVD risk factor profiles than their nondiabetic counterparts, including higher BMI, waist and neck circumferences, triglycerides, higher prevalence of hypertension, and lower HDL cholesterol (P < 0.001, all). Descriptive analyses indicated differences between diabetic and nondiabetic participants in RDI, sleep stages, sleep time <90% O(2) saturation, CAI, and periodic breathing (P < 0.05, all). However, multivariable regression analyses that adjusted for age, sex, BMI, race, and neck circumference eliminated these differences for all sleep measures except percent time in rapid eye movement (REM) sleep (19.0% among diabetic vs. 20.1% among nondiabetic subjects, P < 0.001) and prevalence of periodic breathing (odds ratio [OR] for diabetic subjects versus nondiabetic subjects 1.80, 95% CI 1.02-3.15). Additionally, adjusted analyses showed diabetes was associated with nonstatistically significant elevations in the odds of an increased central breathing index (OR 1.42, 95% CI 0.80-2.55). Addition to the analysis of the 1002 persons with prevalent CVD (including 222 people with diabetes) did not materially change these results.

CONCLUSIONS

These data suggest that diabetes is associated with periodic breathing, a respiratory abnormality associated with abnormalities in the central control of ventilation. Some sleep disturbances may result from diabetes through the deleterious effects of diabetes on central control of respiration. The high prevalence of SDB in diabetes, although largely explained by obesity and other confounders, suggests the presence of a potentially treatable risk factor for CVD in the diabetic population.

Pacemakers, recent directions and developments

PURPOSE OF REVIEW

Pacemaker and implantable cardiovertor defibrillator utilization is evolving rapidly. Expanding indications are reviewed.

RECENT FINDINGS

Current pacemakers are smaller, more dependable, longer lasting and have rate-adaptive features. Implantable cardiovertor defibrillators use transvenous leads and have advanced pacing abilities. Primary pacing indications remain sinus node dysfunction or atrioventricular conduction abnormalities. Dual-chamber pacemakers compared with single chamber ventricular pacemakers, have small quality of life advantages and result in less atrial fibrillation, but decrease stroke rates and mortality. In congestive heart failure patients with delayed ventricular conduction, cardiac resynchronization therapy (atrially timed biventricular pre-excitation) improves physiological parameters, performance indices and quality of life. Atrial arrhythmias may be prevented or treated with appropriate pacing strategies. Pacing-related improvements for symptomatic neurally mediated syncope and symptomatic hypertrophic obstructive cardiomyopathy have been demonstrated. For patients with coronary artery disease and low ejection fractions, implantable cardiovertor defibrillators are well established in the secondary prevention of sudden death, and may be helpful for primary prevention if there are inducible ventricular arrhythmias. Combining cardiac resynchronization and implantable cardiovertor defibrillators in similar patients is under investigation. The role of atrial defibrillators is being defined. Electromagnetic interference remains possible with these devices, particularly in electromagnetically hostile environments.

SUMMARY

More pacemakers and implantable cardiovertor defibrillators will be encountered. Despite increasing sophistication, most often only basic anti-bradycardia modes are essential in the perioperative setting. Understanding the indications for implantation will help the anesthesiologist better support the physiological needs of the patient. Existing perioperative pacemaker-related guidelines for the anesthesiologist still apply.

Sleep disordered breathing and risk factors for cardiovascular disease

Patients with sleep disordered breathing (SDB) are at increased risk for cardiovascular disease including hypertension, angina, myocardial infarction, and stroke. Neurohumoral and hemodynamic responses to untreated sleep apnea are likely mechanisms that produce functional and structural changes within the cardiovascular system. Obesity, higher blood pressure, and advancing age, which are common characteristics of patients with SDB, contribute to the overall risk for cardiovascular disease. Recent studies indicate that OSA is associated with or aggravates other risk markers for cardiovascular disease. These factors include leptin, C-reactive protein, homocysteine, and insulin resistance syndrome. Elevations in C-reactive protein and glucose intolerance may be correlated with the severity of SDB. The impact of alleviating SDB on these cardiovascular risk factors has not been fully elucidated. Regardless, assessment of overall cardiovascular risk in patients with sleep apnea is warranted to identify those individuals that are high-risk who require immediate attention and intervention or in those that should be treated more aggressively.

Cardiovascular consequences of sleep-related breathing disorders

Sleep-related breathing disorders (SRBDs) represent a spectrum of abnormalities that range from simple snoring to upper airway resistance syndrome to sleep apnea. The clinical presentation may include obesity, snoring, neuropsychological dysfunction, and daytime hypersomnolence and tiredness. The acute hemodynamic alterations of obstructive sleep apnea include systemic and pulmonary hypertension, increased right and left ventricular afterload, and increased cardiac output. Earlier reports attributed the coexistence of SRBDs with cardiovascular diseases to the shared risk factors such as age, sex, and obesity. However, recent epidemiologic data confirm an independent association between SRBDs and the different manifestations of cardiovascular diseases. Possible mechanisms may include a combination of intermittent hypoxia and hypercapnia, repeated arousals, sustained increase in sympathetic tone, reduced baroreflex sensitivity, increased platelet aggregation, and elevated plasma fibrinogen and homocysteine levels. The strength of the association, its pathogenesis, and the impact of treatment of SRBDs on the health outcome of patients with cardiovascular diseases are issues to be addressed in future studies.