Obstructive sleep apnea and the recurrence of atrial fibrillation

Prevalence of sleep disordered breathing in paroxysmal and persistent atrial fibrillation patients with normal left ventricular function

AIMS

Recent studies have suggested an emerging link between sleep apnoea and atrial fibrillation (AF). These studies included patients with reduced left ventricular (LV) function which may cause both AF and sleep disordered breathing (SDB). We examined the prevalence of SDB in a population of patients with AF and normal LV function.

METHODS AND RESULTS

Ninety patients with paroxysmal or persistent AF and 45 controls were prospectively enrolled and matched 2:1 for age (AF 56 +/- 12 years; controls 54 +/- 11years) and sex. All patients had normal LV function. SDB was diagnosed using all-night portable polysomnography. Apnoea-hypopnoea index (AHI) in AF patients was higher than in controls (23.19 +/- 19.26 vs. 14.66 +/- 12.43, P = 0.01). The proportion with significant SDB (AHI > 15) was also greater in AF patients (62 vs. 38%, P = 0.01). After adjustment for relevant covariates, the odds ratio for the association between AF and SDB (AHI > 15) was 3.04 (95% CI 1.24-7.46, P = 0.02). The paroxysmal AF group was classified as either 'low-frequency AF' (< or =6) or 'high-frequency AF' (>6) episodes in the past year. High-frequency AF was associated with a higher prevalence (75 vs. 43%, P = 0.012) and severity (mean AHI 28.08 +/- 22.94 vs. 16.69 +/- 15.06, P = 0.028) of SDB when compared with those with low-frequency AF.

CONCLUSION

A high prevalence of SDB is found in relatively young patients with both paroxysmal and persistent AF with normal LV function. This AF population warrants careful consideration for the presence of SDB.

Success of Radiofrequency Catheter Ablation of Atrial Fibrillation: Does Obesity Influence the Outcomes?

Background: Catheter ablation of atrial fibrillation (AF) is an increasingly popular therapeutic option for symptomatic patients who have failed multiple antiarrhythmic drugs (AADs). Patients of higher body mass index often fail direct current cardioversion. The role of body mass index (BMI) on the success of AF ablation is not well understood. Methods: We prospectively studied 511 patients who underwent AF ablation at the Cleveland Clinic Foundation between 2002 and 2005. Patients were divided into four classes based on their BMI: Class I ( 25); Class II (25.1-30); Class III (30.1-35) and Class IV (>35). These groups were compared for baseline demographic and clinical characteristics. Any recurrence of AF after 3 months of ablation was considered as failure. All classes were followed for at least 12 months and rates of failure were compared. Results: Based on their BMI, 25% of patients were assigned to class I, 37% in class II, 21% in class III and 16% in class IV. Patients of higher classification (class III or IV) were more likely to be male (p<0.001), diabetic (p<0.001), smokers (p=0.002), with coronary artery disease (=0.018), left atrial enlargement (p=0.015) and longstanding AF (p=0.007). Severity of obesity as measured by BMI had a direct correlation to early (p=0.05) and late (p=0.01) recurrence of AF. Conclusion: Obesity is significantly associated with long-term AF recurrence after catheter ablation. Higher incidence of smoking & left atrial enlargement may possibly contribute to higher failure rates in this sub-group of patients.

Obstructive sleep apnea, cardiovascular disease, and pulmonary hypertension

With the growing epidemic of obesity in an aging population, obstructive sleep apnea (OSA) is increasingly encountered in clinical practice. Given the acute cardiopulmonary stressors consequent to repetitive upper airway collapse, as well as evidence for cardiovascular homeostatic dysregulation in subjects with sleep apnea, there is ample biologic plausibility that OSA imparts increased cardiovascular risk, independent of comorbid disease. Indeed, observational studies have suggested strong associations with multiple disorders, such as systemic hypertension, heart failure, cardiac arrhythmias, and pulmonary hypertension. Further data in the form of longitudinal cohort studies and randomized controlled trials are accruing to add to the body of evidence. This review examines pathophysiologic mechanisms and explores current concepts regarding the impact of OSA and its treatment on selected clinical disease states.

[Arrhythmias in patients with obstructive sleep apnea]

The authors summarize the current knowledge on the types, prevalence, reasons, diagnosis and current therapy of arrhythmias occurring in patients with obstructive sleep apnea. Most of the patients with obstructive sleep apnea have nocturnal bradycardia (5-50%), paroxysmal tachyarrhythmia (atrial 35%; ventricular 0-15%), or both. The frequency of rhythm disturbances associated with the severity of the sleeping disorder. It is important to recognize the factors predisposing to arrhythmias and the early appropriate therapy of patients is essential, in order to protect patients from life threatening arrhythmias which may worsen the clinical outcome.

Body mass index, obstructive sleep apnea, and outcomes of catheter ablation of atrial fibrillation

BACKGROUND

Obesity and obstructive sleep apnea (OSA) are associated with atrial fibrillation (AF). The effects of a large body mass index (BMI) and OSA on the results of radiofrequency catheter ablation (RFA) of AF are unclear.

OBJECTIVE

To evaluate the effect of BMI and OSA on the efficacy of RFA for AF.

METHODS

RFA was performed in 324 consecutive patients (mean age = 57 +/- 11 years) with paroxysmal (234) or chronic (90) AF. OSA was diagnosed by polysomnography in 32 of 324 patients (10%) prior to ablation. Among the 324 patients, 18% had a normal BMI (<25 kg/m(2)), 39% were overweight (BMI >/= 25 kg/m(2) and <30 kg/m(2)), and 43% were obese (>or=30 kg/m(2)). RFA was performed to eliminate complex fractionated atrial electrograms (CFAE) in the pulmonary vein antrum and left atrium.

RESULTS

At 7 +/- 4 months after a single ablation procedure, 63% of patients without OSA and 41% with OSA were free from recurrent AF without antiarrhythmic drug therapy (P = 0.02). Multivariate analysis including variables of age, gender, type and duration of AF, OSA, BMI, left atrial size, ejection fraction, and hypertension demonstrated that OSA was the strongest predictor of recurrent AF (OR = 3.04, 95% CI: 1.11-8.32, P = 0.03). There was no association between BMI and freedom from recurrent AF. A serious complication occurred in 3 of 324 patients, with no relationship to BMI.

CONCLUSIONS

OSA is a predictor of recurrent AF after RFA independent of its association with BMI and left atrial size. Obesity does not appear to affect outcomes after radiofrequency catheter ablation of AF.

Implications of obstructive sleep apnea for atrial fibrillation and sudden cardiac death

Obstructive sleep apnea (OSA) is a sleep-related breathing disorder with important cardiovascular consequences, including arrhythmogenesis. The unique pathophysiology of OSA results in multiple intermediate mechanisms that may promote atrial fibrillation, ventricular arrhythmias, and sudden cardiac death. These mechanisms may act acutely to trigger nocturnal dysrhythmias, or chronically by affecting the electrical and myocardial substrates. Burgeoning epidemiological data have identified an increased risk for atrial fibrillation and sudden cardiac death related to OSA. Currently, few data exist to support the efficacy of OSA therapy, namely continuous positive airway pressure, as an adjunct for arrhythmia prevention or management.

Association of sleep-disordered breathing and ventricular arrhythmias in patients without heart failure

The prevalence and characteristics of sleep-disordered breathing (SDB) in patients with ventricular arrhythmias, such as premature ventricular complexes and ventricular tachycardia, are unknown. Therefore, this study was conducted to evaluate the prevalence of SDB in patients with severe ventricular arrhythmias and normal left ventricular (LV) function. Thirty-five patients (63% men, mean age 57.4 +/- 13.8 years) underwent a sleep study. All patients had ventricular tachycardia or frequent premature ventricular complexes (>or=300/hour) and had been referred to the cardiology department for medication, catheter ablation therapy, or the implantation of a cardioverter-defibrillator. Patients with heart failure with LV ejection fractions <50% were excluded; in the remaining patients, the mean LV ejection fraction was 63.9 +/- 8.0%. Twenty-one patients (60%) had SDB with apnea-hypopnea indexes >or=5/hour, and the average apnea-hypopnea index was 22.7 +/- 17.9/hour. Twelve patients (34%) had moderate to severe SDB, with an average apnea-hypopnea index of 33.6 +/- 16.6/hour. Central dominant sleep apnea was evident in 3 patients with SDB. The average age and body mass index were significantly higher in patients with SDB than in those without SDB (age 62.0 +/- 12.8 vs 50.6 +/- 12.7 years, body mass index 26.3 +/- 4.0 vs 21.2 +/- 2.0 kg/m2). In conclusion, this study found a high prevalence of SDB in patients with ventricular arrhythmias and normal LV function.

Association of sleep-disordered breathing with postoperative complications

BACKGROUND

Obstructive sleep apnea (OSA) is associated with increased perioperative risk, but the incidence of postoperative complications and the severity of OSA associated with increased risk have not been established. We investigated the relationship between intermittent hypoxemia measured by home nocturnal oximetry with the occurrence of postoperative complications in patients with clinical signs of OSA identified during preoperative assessment for elective surgery.

METHODS

This study was performed at a tertiary care hospital. Home nocturnal oximetry was performed on elective surgical patients with clinical features of OSA. The number of episodes per hour of oxygen desaturation (or oxygen desaturation index) of > or = 4% (ODI4%) was determined. Subjects with five or more desaturations per hour (ODI4% > or = 5) were compared to those with less than five desaturations per hour (ODI4% < 5). Hospital records were reviewed to assess the incidence and type of postoperative complications.

RESULTS

A total of 172 patients were investigated as part of this study. No significant differences were observed between groups in terms of age, body mass index, number of medical comorbidities, or smoking history. Patients with an ODI4% > or = 5 had a significantly higher rate of postoperative complications than those with ODI4% < 5 (15.3% vs 2.7%, respectively [p < 0.01]; adjusted odds ratio, 7.2; 95% confidence interval, 1.5 to 33.3 [p = 0.012]). The complication rate also increased with increasing ODI severity (patients with an ODI4% of 5 to 15 events per hour, 13.8%; patients with an ODI4% of > or = 15 events per hour, 17.5%; p = 0.01) Complications were respiratory (nine patients), cardiovascular (five patients), GI (one patient), and bleeding (two patients). The hospital length of stay was similar in both groups.

CONCLUSION

An ODI4%> or = 5, determined by home nocturnal oximetry, in patients with clinical features of OSA is associated with an increased rate of postoperative complications.

Diagnosis and treatment of sleep apnea in heart disease

One of the most common yet unidentified conditions in heart disease is sleep-disordered breathing (SDB). Although it is most prevalent in patients with heart failure, it has been epidemiologically and pathophysiologically linked to ischemic heart disease, hypertension, sudden cardiac death, atrial fibrillation, and stroke. There are two primary SDB syndromes: obstructive sleep apnea (OSA) and central sleep apnea (CSA; also known as Cheyne-Stokes respiration). The pathophysiologic mechanisms that underlie these disorders appear to be distinct but both involve recurrent cycles of excessive sympathetic activation, hypoxemias and hypercapnias, and increases in ventricular wall stress. Signs and symptoms may include daytime somnolence, snoring, difficult-to-control hypertension, and refractory arrhythmias or angina. In heart failure, half of patients will have SDB and most patients will exhibit evidence of both OSA and CSA, although one or the other may predominate. The current standard diagnostic method is overnight laboratory polysomnography. Primary therapies for OSA include lifestyle changes, various facial and oral appliances, head and neck surgery, and continuous positive airway pressure (CPAP). CPAP is the most effective form of therapy for OSA, with few side effects, but is limited by compliance because of comfort-related issues. In patients with cardiovascular disease who predominantly suffer from OSA, treatment recommendations should be based on current guidelines for OSA. For patients with heart failure with predominant CSA, the current cornerstone of therapy is the optimization of medical therapy and resynchronization therapy when indicated. When SDB persists despite optimal medical management, referral to a sleep medicine consultant should be considered.

Status of the epidemiology of atrial fibrillation

Atrial fibrillation (AF), an increasingly common dysrhythmia, is responsible for substantial morbidity and mortality. Currently in the United States, approximately 2.3 million people are diagnosed with AF and, based on the census, this number may rise to 5.6 million by 2050. Risk factors for AF include advancing age and cardiovascular disease and its risk factors. The chief hazard of AF is embolic stroke, which is increased four- to fivefold, assuming great importance in advanced age when it becomes a dominant factor. AF is associated with about a doubling of mortality.

Severe obesity and P-wave dispersion: the effect of surgically induced weight loss

BACKGROUND

Recent data have shown that obesity is an important potential risk factor for atrial fibrillation (AF). The mechanism of development of AF in obesity patients is still unclear and may be related to atrial refractoriness heterogeneity. The aim of our study was to determine the influence of bariatric surgery with a consequent substantial weight loss on P-wave dispersion in morbidly obese population.

METHODS

We enrolled in this study 40 severe obese patients, and 40 age-matched non-obese healthy subjects were also recruited as controls. All subjects underwent conventional 12-lead electrocardiography for the analysis of P-wave dispersion. All subjects underwent bariatric surgery and were resubmitted to electrocardiography, biochemical, and anthropometric examination within 12 months after intervention.

RESULTS

Severe obese patients had greater values in P-wave duration and dispersion than the normal weight controls. Bariatric surgery reduced significantly P-wave dispersion. There was a significant correlation between decrease of atrial refractoriness heterogeneity and bariatric-surgery-induced weight loss.

CONCLUSIONS

In severe obese patients, surgically induced weight loss reduction is associated with significant decreased in P-wave dispersion. The reduction of the atrial refractoriness heterogeneity may be of clinical significance by reducing the risk of atrial fibrillation in morbidly obese subjects.

Depressive symptoms predict recurrence of atrial fibrillation after cardioversion

OBJECTIVE

The aim of this study was to evaluate whether depressive symptoms and the type-D personality are predictive of early recurrence of atrial fibrillation (or atrial flutter; AF) after successful electrical cardioversion (CV).

BACKGROUND

Depressive symptoms are associated with an adverse prognosis in patients with coronary artery disease, congestive heart failure, and ventricular arrhythmias. Anger and hostility have been shown to be predictive of development of AF. However, little is known about the effects of depression on AF.

METHODS

Fifty-four patients with persistent AF completed the Hospital Anxiety and Depression Scale (HADS) and the Type D Scale (DS-14) prior to elective electrical CV. Patients with a successful CV were followed for 2 months.

RESULTS

During the follow-up period, 27 patients (50%) had recurrence of the arrhythmia. Depressive mood (HADS depression scale >7) was the only significant nonsomatic predictor of recurrence, which was observed in 85% of depressed versus 39% of nondepressed patients [odds ratio=8.6; 95% confidence interval (CI)=1.7-44.0, P=.004]. HADS anxiety scores and the presence of the type-D personality pattern were not associated with recurrence of AF. On multivariate Cox regression analysis, including variables with a prevalence >10% of the total study population and a univariate discriminative effect yielding a P value of <.2, a HADS depression score >7 was found to be the only independently predictive variable of arrhythmia recurrence (hazard ratio=2.7; 95% CI=1.05-7.2; P=.046).

CONCLUSIONS

Our results indicate that depressive mood is a major risk factor for recurrence of AF after electrical CV. Heightened adrenergic tone and a proinflammatory state are possible mechanisms responsible for the observed association. Identification of depression may be of value prior to the decision to perform electrical CV.

Positive airway pressure treatment for obstructive sleep apnea

Positive airway pressure (PAP) is the treatment of choice for patients with moderate-to-severe obstructive sleep apnea (OSA). Randomized controlled trials have demonstrated that PAP can effectively reduce the apnea-hypopnea index and improve subjective and objective sleepiness. Some studies have also demonstrated benefits in sleep quality and quality of life for both the patient and bed partner. Observational studies have shown a reduction in the risk of cardiovascular events in OSA patients treated with PAP compared to untreated patients. Since continuous PAP (CPAP) treatment of OSA was described, additional modes of pressure delivery have been developed (bilevel PAP, autoadjusting PAP, flexible PAP). While none of the variants of PAP improves adherence in unselected patients compared to CPAP, individual patients may respond to a change in pressure mode. Attended PAP titration remains the standard of practice for selecting a treatment pressure. However, use of autotitrating PAP devices in the unattended setting can provide an effective titration alternative with careful patient selection and review of titration results. More choices of mask interface are now available to improve comfort and intervene for mask or mouth leaks. However, despite the increase in PAP treatment options, lack of acceptance and inadequate adherence to PAP therapy remain the major causes of treatment failure. Some studies suggest that heated humidification can improve PAP adherence, especially in patients with nasal congestion or dryness. A systematic approach to PAP treatment including education, objective adherence monitoring, early intervention for side effects, and telephone and clinic support is essential to optimize adherence.

Sleep apnea: epidemiology, pathophysiology, and relation to cardiovascular risk

Several studies have shown the occurrence of an independent association between obstructive sleep apnea syndrome (OSAS) and cardiovascular disease, including arterial hypertension, ischemic heart disease, and stroke. The pathogenesis of the cardiovascular complications of OSAS is still poorly understood, however. Several mechanisms are likely to be involved, including sympathetic overactivity, selective activation of inflammatory molecular pathways, endothelial dysfunction, abnormality in the process of coagulation, and metabolic dysregulation. The latter may involve insulin resistance and disorders of lipid metabolism. The aim of this review, which reports the data presented at a workshop jointly endorsed by the European Society of Hypertension and by the European Union COST action on OSAS (COST B26), is to critically summarize the evidence available to support an independent association between OSAS and cardiovascular disease.

Obstructive Sleep Apnea and its Relationship to Cardiac Arrhythmias

Obstructive sleep apnea (OSA) affects approximately 4% of middle-aged men and 2% of middle-aged women. Cardiac arrhythmias are common problems in patients with OSA, even though the true prevalence and clinical relevance of cardiac arrhythmias remains to be determined. The presence and complexity of both tachyarrhythmias and bradyarrhythmias may influence morbidity, mortality, and the quality of life for OSA patients. Although the exact mechanisms underlying the link between OSA and cardiac arrhythmias are not well established, they could be partially the same proposed mechanisms relating OSA to different cardiovascular diseases. OSA is characterized by repetitive pharyngeal collapse during sleep that leads to markedly reduced or absent airflow, followed by oxyhemoglobin desaturation, persistent inspiratory efforts against an occluded airway, and termination by arousal from sleep. These mechanisms elicit a variety of autonomic, hemodynamic, humoral, and neuroendocrine responses that by themselves evoke acute and chronic changes in cardiovascular function. These effects may lead to the development of cardiac arrhythmias and any other form of cardiovascular disease linked to OSA. The aims of this review are to describe the essential cardiovascular pathophysiological aspects of OSA, to outline the relationship between OSA and both tachyarrhythmias and bradyarrhythmias and their possible influence in the natural history of OSA patients, and to assess the effects of OSA treatment on the presence of cardiac arrhythmias.

Cardiovascular outcomes of CPAP therapy in obstructive sleep apnea syndrome

Considerable evidence is now available of an independent association between obstructive sleep apnea syndrome (OSAS) and cardiovascular disease. The association is particularly strong for systemic arterial hypertension, but there is growing evidence of an association with ischemic heart disease and stroke. The mechanisms underlying cardiovascular disease in patients with OSAS are still poorly understood. However, the pathogenesis is likely to be a multifactorial process involving a diverse range of mechanisms, including sympathetic overactivity, selective activation of inflammatory molecular pathways, endothelial dysfunction, abnormal coagulation, and metabolic dysregulation, the latter particularly involving insulin resistance and disordered lipid metabolism. Therapy with continuous positive airway pressure (CPAP) has been associated with significant benefits to cardiovascular morbidity and mortality, both in short-term studies addressing specific aspects of morbidity, such as hypertension, and more recently in long-term studies that have evaluated major outcomes of cardiovascular morbidity and mortality. However, there is a clear need for further studies evaluating the impact of CPAP therapy on cardiovascular outcomes. Furthermore, studies on the impact of CPAP therapy have provided useful information concerning the role of basic cell and molecular mechanisms in the pathophysiology of OSAS.

Obstructive sleep apnea is associated with increased urinary albumin excretion

BACKGROUND

Obstructive sleep apnea (OSA) is associated with cardiovascular disease through incompletely understood mechanisms. Urinary albumin excretion is a surrogate for endothelial dysfunction and a potent cardiovascular disease risk predictor. We sought to determine whether urinary albumin excretion is increased in subjects with OSA.

METHODS

Four hundred ninety-six adults, representing a spectrum of OSA severity, underwent overnight polysomnography and urine collection. OSA severity was assessed using the apnea-hypopnea index (AHI). The primary outcome measure was the adjusted albumin-to-creatinine ratio (aACR). Linear mixed models were used to assess the association between AHI category and aACR, adjusted for confounders and renal dysfunction.

RESULTS

Subjects had a mean age of 44 +/- 17 (SD) years and approximately half were men (44%) and African American (56%). The percentages of subjects with mild (AHI 5-14), moderate (AHI 15-29), and severe (AHI > or = 30) OSA were 23%, 15%, and 15%, respectively. The median aACR for the entire sample was 4.3 mg/g (interquartile range: 2.9, 7.5). Adjusted linear mixed-model analyses showed a significant association between AHI category and aACR, with the AHI > or = 30 group having the highest aACR levels (7.87 +/- 1.02 mg/g vs 5.08 +/- 0.41 mg/g for those with AHI < 5; P < 0.006). Similar findings were observed after excluding subjects with renal dysfunction.

CONCLUSION

OSA is significantly associated with increased urine albumin excretion, especially among those with more severe disease. These data provide further evidence supporting endothelial dysfunction as a mediating pathway between cardiovascular disease and OSA.

Microarray studies of genomic oxidative stress and cell cycle responses in obstructive sleep apnea

Obstructive sleep apnea (OSA), the commonest form of sleep-disordered breathing, is characterized by recurrent episodes of intermittent hypoxia and sleep fragmentation. This study evaluated microarray measures of gene transcript levels in OSA subjects compared to age and BMI matched healthy controls. Measurements were obtained before and after: (a) a night of normal sleep in controls; and (b) a night of untreated apnea in OSA patients. All subjects underwent full polysomnography. mRNA from the whole blood samples was analyzed by HG-U133A and B Affymetrix GeneChip arrays using Spotfire 7.2 data analysis platform. After sleep in OSA patients, changes were noted in several genes involved in modulation of reactive oxygen species (ROS), including heme oxygenase 1, superoxide dismutase 1 and 2, and catalase. Changes were also observed in genes involved in cell growth, proliferation, and the cell cycle such as cell division cycle 25B, signaling lymphocyte activating molecule (SLAM), calgizzarin S100A11, B-cell translocation gene, Src-like adapter protein (SLAP), and eukaryotic translation initiation factor 4E binding protein 2. These overnight changes in OSA patients are suggestive of activation of several mechanisms to modulate, and adapt to, increased ROS developing in response to the frequent episodes of intermittent hypoxia.

Clinical perspective of obstructive sleep apnea-induced cardiovascular complications

Obstructive sleep apnea (OSA) syndrome is a highly prevalent disorder characterized by recurrent upper airway collapse during sleep, and associated with repetitive episodes of transient oxygen desaturation during sleep. It disrupts normal ventilation and sleep architecture, and is typically associated with excessive daytime sleepiness, snoring, and witnessed apneas. Besides being associated with neurocognitive impairment, mood and behavioral effects, and increased risk for work-related and traffic accidents, OSA has also been implicated in the pathogenesis of various cardiovascular diseases, including systemic hypertension, coronary artery disease, congestive heart failure, pulmonary hypertension, stroke, and cardiac arrhythmias. The mechanisms by which OSA affects the cardiovascular system may involve mechanical effects on intrathoracic pressure, increased sympathetic activation, intermittent hypoxia, and endothelial dysfunction. Therapy with continuous positive airway pressure (CPAP) has been demonstrated to improve cardiopulmonary hemodynamics in patients with OSA and may reverse the endothelial cell dysfunction.

Sleep apnea: clinical investigations in humans

Sleep apnea syndrome (SAS), a common disorder, is characterized by repetitive episodes of cessation of breathing during sleep, resulting in hypoxemia and sleep disruption. The consequences of the abnormal breathing during sleep include daytime sleepiness, neurocognitive dysfunction, development of cardiovascular disorders, metabolic dysfunction, and impaired quality of life. There are two types of SAS: obstructive sleep apnea syndrome (OSAS) and central sleep apnea syndrome (CSAS). OSAS is a prevalent disorder in which there is snoring, repetitive apneic episodes, and daytime sleepiness. Anatomical conditions causing upper airway obstruction (obesity or craniofacial abnormalities such as retrognathia or micrognathia) can cause OSAS. CSAS, much less common than OSAS, is a disorder characterized by cessation of breathing which is caused by reduced respiratory drive from the central nervous system to the muscles of respiration. The latter condition is common in patients with heart failure and cerebral neurologic diseases. The diagnosis of SAS requires assessment of subjective symptoms and apneic episodes during sleep documented by polysomnography. Treatments of OSAS include continuous positive airway pressure (CPAP), oral appliances, and surgery; patients with CSAS are treated with oxygen, adaptive servo-ventilation, or CPAP. With assessment and treatment of the SAS, patients usually have resolution of their disabling symptoms, subsequently resulting in improved quality of life.

Comparison of cardiac structural and functional changes in obese otherwise healthy adults with versus without obstructive sleep apnea

Obstructive sleep apnea (OSA) and obesity have been linked to systolic and diastolic dysfunction of the left ventricle. Right ventricular function is poorly understood in the 2 clinical conditions. Data from this study show that otherwise healthy obese patients with OSA had increased an left atrial volume index compared with similarly obese patients without OSA (16.3 +/- 1.2 ml/m in obese patients without OSA vs 20.2 +/- 1.0 ml/m in those with OSA, p = 0.02) and altered diastolic function reflected by changes in mitral annular late diastolic velocity (-5.7 +/- 0.7 cm/s in obese patients without OSA vs -7.3 +/- 0.7 cm/s in those with OSA, p = 0.007), mitral annular early diastolic velocity (-7.9 +/- 0.6 cm/s in obese patients without OSA vs -6.4 +/- 0.3 cm/s in those with OSA, p = 0.05), and early to late diastolic annular ratio >1 (82% of obese patients without OSA vs 26% of those with OSA, p = 0.001), which may be signs of early subclinical impairment of cardiac function. Importantly, healthy obese subjects had similarly increased left ventricular mass compared with obese patients with OSA but normal diastolic function and left atrial size. There was a trend toward abnormal right ventricular filling in patients with OSA, measured by altered superior vena cava diastolic velocity during expiration (-15 +/- 2 cm/s in obese patients without OSA vs -10 +/- 3 cm/s in those with OSA, p = 0.2) and a tendency toward diastolic dysfunction reflected by decreased lateral tricuspid annular early diastolic velocity (-7.2 +/- 0.5 cm/s in obese patients without OSA vs -6.1 +/- 0.5 cm/s in those with OSA, p = 0.1) beyond that seen in obesity alone. In conclusion, OSA independent of obesity may induce cardiac changes that could predispose to atrial fibrillation and heart failure.

Feasibility of automated detection of advanced sleep disordered breathing utilizing an implantable pacemaker ventilation sensor

OBJECTIVES

This study tested the feasibility of automatically detecting advanced sleep disordered breathing (SDB) from a pacemaker trans-thoracic impedance sensor.

BACKGROUND

SDB is prevalent yet under-diagnosed in patients with cardiovascular disease. The potential for automated detection of SDB in patients receiving pacemakers with respiration sensors has not been fully explored. We hypothesized that the trans-thoracic impedance sensor could be utilized for automatic detection of advanced SDB.

METHODS

Patients underwent overnight polysomnography (PSG). The pacemaker trans-thoracic impedance signal was simultaneously recorded and time synchronized with the polysomnograph. Cardiovascular health variables were abstracted from medical records. Apnea was defined as cessation of inspiratory airflow lasting 10 seconds or longer. Hypopnea was defined as a reduction of tidal volume of at least 30% from baseline tidal volume, lasting 10 seconds or more. A computer algorithm (PM-A) was developed to automatically detect SDB from the pacemaker impedance sensor data. The performance of automated SDB detection was compared against PSG.

RESULTS

Sixty patients (aged 69 +/- 12 years, 45 males) were studied. Advanced SDB (moderate or severe) was diagnosed in 40 patients. Severe SDB (apnea-hypopnea index [AHI]> or = 30) was diagnosed in 32 patients (53%), but only 5 patients had prior diagnosis of the disease. Moderate SDB (30 > AHI > 15) was diagnosed in 8 patients of whom only two were previously diagnosed. Cardiovascular health variables did not predict the presence of advanced SDB. PM-A derived AHI correlated with that of the PSG (r = 0.80, P < 0.01). The algorithm identified patients with advanced SDB with 82% sensitivity and 88% specificity.

CONCLUSIONS

It is feasible to automatically measure SDB severity using a pacemaker trans-thoracic impedance sensor. Advanced SDB was frequently undiagnosed in this cohort of pacemaker patients.

Obstructive sleep apnea: an update on mechanisms and cardiovascular consequences

BACKGROUND AND AIM

There is growing recognition of the widespread incidence and health consequences of obstructive sleep apnea (OSA). This review examines the evidence linking sleep apnea with cardiovascular disease and discusses potential mechanisms underlying this link.

DATA SYNTHESIS

The weight of evidence provides increasing support for a causal relationship between OSA and hypertension. Furthermore, OSA may contribute to the initiation and progression of cardiac ischemia, heart failure and stroke. Chronic sympathetic activation appears to be a key mechanism linking OSA to cardiovascular disease. Other potential mechanisms include inflammation, endothelial dysfunction, increased levels of endothelin, hypercoagulability and stimulation of the renin angiotensin system. OSA, hypertension and obesity often coexist and interact, sharing multiple pathophysiological mechanisms and cardiovascular consequences. Effective treatment of OSA may attenuate neural and humoral abnormalities in circulatory control, improve blood pressure control and conceivably reduce the risk of future cardiovascular events.

CONCLUSION

Patients with OSA are at increased risk for cardiovascular disease. OSA should be considered in the differential diagnosis of hypertensive patients who are obese. In particular, OSA should be excluded in patients with hypertension resistant to conventional drug therapy.

Lungenerkrankungen und Herzfunktion

The most severe cardiac sequel to lung disease is the load on the right ventricle due to pulmonary hypertension with the development of a cor pulmonale. This is characterized by hypertrophy and/or dilatation of the right ventricle because of a primary impairment of lung function and/or lung structure. The most important pathomechanisms for the development of pulmonary hypertension are vessel obliteration, mechanical lesions, primary vascular or extra-vascular inflammation and hypoxic vasoconstriction. Chronic obstructive pulmonary disease (COPD) is one of the most important reasons for chronic cor pulmonale. A further very common reason is obstructive sleep apnea syndrome, especially if combined with a COPD. In this case, the prevalence of cor pulmonale can reach 80%. The development of a chronic cor pulmonale is the most striking negative prognostic factor for these patients. Only 30% of COPD patients with cor pulmonale survive longer than 5 years, and only early detection of the disturbances to respiration which might potentially lead to cor pulmonale and their subsequent therapy are able to improve the patient's prognosis. Furthermore, pulmonary diseases may also have an impact on the left heart side in terms of an impairment of left heart function or by inducing severe arrhythmias . Thus, lung diseases may have both a significant impact on right and left heart performance.

Screening for sleep-related breathing disorders by transthoracic impedance recording integrated into a Holter ECG system

In patients with arrhythmias, coincidence with sleep-related breathing disorders (SRBD) is high and of clinical relevance. Electrocardiogram-derived (ECG) parameters have been developed for SRBD screening, but it has proved necessary to exclude patients with frequent arrhythmias. Holter-based screening tools, easy to use, are therefore warranted. The goal of our study was to evaluate the diagnostic accuracy, with respect to SRBD detection, of transthoracic impedance recording (TTIR) integrated into a Holter System. Our investigation consisted of 2 phases. In phase 1 we compared the performance of TTIR to that of in-hospital polysomnography (PSG) in 56 patients (46 male, mean age 57). In phase 2 we compared TTIR to results from an ambulatory polygraphy (PG) system in 180 patients (143 male, mean age 56). We scored apnea and hypopnea from P(S)G, and derived a respiratory-disturbance index (P(S)G-RDI). TTIR was analyzed semi-automatically. Reduction of the impedance amplitude by more than 50% over 10 s was scored as apnea/hypopnea, with consequent calculation of TTIR-RDI. In phase 1, 20 out of 56 patients revealed a PSG-RDI > 10 h(-1). TTIR-RDI in 19 patients from this group was >10 h(-1) (sensitivity 95%, specificity 97.2%, positive predictive value 95%, negative predictive value 97.2%, interclass correlation coefficient 0.98). In phase 2, 46 of 180 patients revealed a PSG-RDI > 10 h(-1). TTIR-RDI in 37 out of this group was >10 h(-1) (sensitivity 80.4%, specificity 92.5%, positive predictive value 78.7%, negative predictive value 93.2%, interclass correlation coefficient 0.92). TTIR integrated into a Holter ECG system and tested in a large patient cohort demonstrates acceptable high accuracy in detection of SRBD. Arrhythmia analysis and screening for SRBD can be performed in a single-step approch.

Obstructive sleep apnea, obesity, and the risk of incident atrial fibrillation

OBJECTIVES

This study sought to identify whether obesity and obstructive sleep apnea (OSA) independently predict incident atrial fibrillation/flutter (AF).

BACKGROUND

Obesity is a risk factor for AF, and OSA is highly prevalent in obesity. Obstructive sleep apnea is associated with AF, but it is unknown whether OSA predicts new-onset AF independently of obesity.

METHODS

We conducted a retrospective cohort study of 3,542 Olmsted County adults without past or current AF who were referred for an initial diagnostic polysomnogram from 1987 to 2003. New-onset AF was assessed and confirmed by electrocardiography during a mean follow-up of 4.7 years.

RESULTS

Incident AF occurred in 133 subjects (cumulative probability 14%, 95% confidence interval [CI] 9% to 19%). Univariate predictors of AF were age, male gender, hypertension, coronary artery disease, heart failure, smoking, body mass index, OSA (hazard ratio 2.18, 95% CI 1.34 to 3.54) and multiple measures of OSA severity. In subjects <65 years old, independent predictors of incident AF were age, male gender, coronary artery disease, body mass index (per 1 kg/m2, hazard ratio 1.07, 95% CI 1.05 to 1.10), and the decrease in nocturnal oxygen saturation (per 0.5 U log change, hazard ratio 3.29, 95% CI 1.35 to 8.04). Heart failure, but neither obesity nor OSA, predicted incident AF in subjects > or =65 years of age.

CONCLUSIONS

Obesity and the magnitude of nocturnal oxygen desaturation, which is an important pathophysiological consequence of OSA, are independent risk factors for incident AF in individuals <65 years of age.

The risk factor association syndrome as a barisystemic syndrome: A view on obesity and the metabolic syndrome

A number of factors are known to be associated to an increased risk of cardiovascular disease. High blood pressure, lipid abnormalities, type 2 diabetes mellitus, obesity and sleep apnea may act as isolated risk factors but, frequently, coexist in the same person. Studies involving surgery aimed at weight reduction (bariatric surgery - from barys, the greek term for heavy) have consistently shown a high probability of resolution of major risk factors, namely of diabetes, hyperlipidemia and hypertension, associated to weight reduction. Data in a similar direction were obtained after weight reduction was reached by means of pharmacological therapy. Excessive weight thus may stand as the probable cause for a number of cardiovascular risk factors, at least in many patients with an adequate genetic background. The moment may have come to focus on causality and to suggest that the risk factor association syndrome, in patients with overweight/obesity, may be defined as the systemic consequences of excessive weight, including hormonal, body habitus, metabolic, hemodynamic and respiratory parameters. A suitable name for the syndrome might be the barisystemic syndrome.

Epidemiology of atrial fibrillation: a current perspective

The prevalence of atrial fibrillation (AF) increases with age. Recent population-based data indicate a trend of increasing incidence and prevalence of AF that is incompletely explained by an aging population. A recent population study estimated that the number of Americans afflicted by AF will increase from the current 2.3 million to more than 10 million by 2050. Novel risk factors--obesity and sleep apnea--may partially account for the current AF epidemic. Ethnic differences in the epidemiology of AF have been suggested but not clearly elucidated by population-based studies. The heritability of AF in the general population is strongly supported by population-based data. Genetic epidemiological studies on AF can potentially yield important mechanistic insights that may ultimately lead to novel preventative and therapeutic strategies.

The risk profile for obstructive sleep apnea does not affect the recurrence of atrial fibrillation

BACKGROUND

Obstructive sleep apnea (OSA) has been linked to increased prevalence and recurrence of atrial fibrillation (AF). We hypothesized that OSA may aggravate AF in patients with pacemakers implanted for sinus bradycardia who had documented paroxysmal AF.

METHODS

Seventy-two patients (36 M, aged 77 +/- 6 years) completed the study. All patients received a dual-chamber pacemaker equipped with diagnostic and preventive functions for AF. OSA was diagnosed with the Berlin Questionnaire, which is validated to identify patients with OSA. Four-month continuous pacemaker recordings were collected for all patients.

RESULTS

OSA was diagnosed in 28% of patients. Patients at high risk for OSA (HR group) and patients at low risk for OSA (LR group) were equivalent for gender, age, and body mass index. The rate of hypertension was higher in HR than in LR group (90% vs 44%, P < 0.01). The prevalence of paroxysmal AF during the study period was similar in HR and LR group (53% vs 44%, P = NS). Overall number of AF episodes per month was not significantly different between HR and LR group (7 +/- 13 vs 36 +/- 122, P = NS). Similarly, AF burden (AF%) was not significantly different between HR and LR group (0.3 +/- 0.6 vs 2.0 +/- 4.8, P = NS). Circadian distribution of AF episodes was similar in both groups.

CONCLUSION

Long-term pacemaker recording of AF recurrence, AF burden, and its circadian distribution is similar in patients with paroxysmal AF at high risk for OSA and those at low risk for OSA.

Validation and clinical utility of a simple in-home testing tool for sleep-disordered breathing and arrhythmias in heart failure: results of the Sleep Events, Arrhythmias, and Respiratory Analysis in Congestive Heart Failure (SEARCH) study

Fifty patients with New York Heart Association class III systolic heart failure were enrolled in this prospective multicenter study that compared the diagnostic accuracy of a home-based cardiorespiratory testing system with standard attended polysomnography. Patients underwent at least 2 nights of evaluation and were scored by blinded observers. At diagnostic cutoff points of > or =5, > or =10, and > or =15 events per hour for respiratory disturbance severity, polysomnography demonstrated a sleep-disordered breathing prevalence of 69%, 59%, and 49%, respectively. Compared with polysomnography, the cardiorespiratory testing system demonstrated predictive accuracies of 73%, 73%, and 75%, which improved to 87%, 87%, and 83%, respectively, when analysis of covariance suggested reanalysis omitting one site's data. The system accurately identified both suspected and unsuspected arrhythmias. The device was judged by 80% of patients to be easy or very easy to use, and 74% of patients expressed a preference for the in-home system. Therefore, this system represents a reasonable home testing device in these patients.

[Role of oxidative stress in respiratory diseases and its monitoring]

Together with inflammation and subsequent remodeling of airways, an imbalance between oxidative and anti-oxidative agents is generated during the development of numerous pulmonary diseases. This process seems to be involved in both the pathogenesis and chronification of asthma, chronic obstructive pulmonary disease (COPD), SOAS, interstitial lung diseases and cystic fibrosis. Reactive oxygen species including superoxide anion, hidroxyl radicals and hydrogen peroxide (H2O2) are synthetised as a response of inflammatory cells and are responsible of the oxidation of nucleic acids, proteins and membrane lipids, leading to cell damage and enhanced inflammation. Until recently, it was difficult to quantify the airway production of reactive oxidative species (ROS). In fact, it has been only in the last few years when it has been possible to determine indirectly the levels of ROS in expired air and in tissue of asthmatic patients. The analysis of exhaled air is a single, reproducible and non-invasive technique which is useful in the study of volatile and non-volatile gases generated in different conditions. The determination of exhaled nitric oxide and carbon monoxide (CO) has a great usefulness in the assessment of asthma. Nitric oxide seems to be closely related to the physiopathology of asthma and COPD. In fact, it is correlated with the levels of sputum eosinophils and with the response to the treatment with steroids. Yet a correlation with the degree of airflow obstruction and the seriousness of the process has not been found. Exhaled CO is another indirect marker of inflammation and it is increased in asthma, COPD, cystic fibrosis and bronchectases. Even though numerous studies have shown its usefulness as a marker of inflammation and in the response to corticosteroids, its clinical application has limitations. In particular, it is not a specific and exclusive marker of oxidative stress and its levels are highly influenced by tobacco smoke. On the other hand, the association between exhaled CO and FEV1 is not clear and no relationship has been proved so far with the improvement of pulmonary function after steroid therapy and with the decrease of maximum expiratory flow at relapses. In this Review, we describe the advances in the knowledge of oxidative stress as a decisive factor in the pathogenesis of prevalent pulmonary diseases, as well as the methods allowing its analysis and monitoring.

Cardiac changes during arousals from non-REM sleep in healthy volunteers

Our aim was to evaluate cardiac changes evoked by spontaneous and sound-induced arousals from sleep. Cardiac responses to spontaneous and auditory-induced arousals were recorded during overnight sleep studies in 28 young healthy subjects (14 males, 14 females) during non-rapid eye movement sleep. Computerized analysis was applied to assess beat-to-beat changes in heart rate, atrio-ventricular conductance, and ventricular repolarization from 30 s before to 60 s after the auditory tone. During both types of arousals, the most consistent change was the increase in the heart rate (in 62% of spontaneous and in 89% of sound-induced arousals). This was accompanied by an increase or no change in PR interval and by a decrease or no change in QT interval. The magnitude of all cardiac changes was significantly higher for tone-induced vs. spontaneous arousals (mean +/- SD for heart rate: +9 +/- 8 vs. +13 +/- 9 beats per min; for PR prolongation: 14 +/- 16 vs. 24 +/- 22 ms; for QT shortening: -12 +/- 6 vs. -20 +/- 9 ms). The prevalence of transient tachycardia and PR prolongation was also significantly higher for tone-induced vs. spontaneous arousals (tachycardia: 85% vs. 57% of arousals, P < 0.001; PR prolongation: 51% vs. 25% of arousals, P < 0.001). All cardiac responses were short-lasting (10-15 s). We conclude that cardiac pacemaker region, conducting system, and ventricular myocardium may be under independent neural control. Prolongation of atrio-ventricular delay may serve to increase ventricular filling during arousal from sleep. Whether prolonged atrio-ventricular conductance associated with increased sympathetic outflow to the ventricular myocardium contributes to arrhythmogenesis during sudden arousal from sleep remains to be evaluated.

Obesity, ethnicity, and sleep-disordered breathing: medical and health policy implications

The obesity epidemic in the United States is a major health problem, which poses im-mediate and long-term health risks with potential for significant reduction in life expectancy if not curtailed. Despite affecting all segments of the population, minorities carry a relatively larger burden of the obesity threat. Obesity is a major risk factor for develop-ing obstructive sleep apnea and the metabolic syndrome, which are associated with increased cardiovascular and cerebrovascular morbidity and mortality. This article discusses the implications of the obesity trend on the prevalence of obstructive sleep ap-nea and health, highlights ethnic differences, reviews the resultant economic implications, and suggests public health and health policy initiatives that may be beneficial in stemming the obesity scourge.

Uvulopalatopharyngoplasty decreases levels of C-reactive protein in patients with obstructive sleep apnea syndrome

BACKGROUND

C-reactive protein is a crucial risk factor for cardiovascular diseases. Previous studies demonstrated that in patients with obstructive sleep apnea syndrome (OSAS), levels of this protein elevate dependently on the degree of upper airway obstruction. However, it has not been determined whether the surgery for OSAS reduces the levels of C-reactive protein by restoring the airway opening. Therefore, we evaluated the effect of uvulopalatopharyngoplasty (UPPP) on levels of serum C-reactive protein in patients with this syndrome.

METHODS

Fifteen adult patients with mild to severe OSAS were enrolled in this study. Levels of serum C-reactive protein and sleep parameters including apnea-hypopnea index a month before and 3 months after UPPP were evaluated using peripheral venous blood and polysomnography, respectively.

RESULTS

Uvulopalatopharyngoplasty significantly restored sleep parameters, accompanying with decreased levels of C-reactive protein (from 0.21 +/- 0.17 to 0.10 +/- 0.16 mg/dL, P < .05).

CONCLUSIONS

In patients with OSAS, UPPP appears to decrease levels of serum C-reactive protein. Surgical therapy may reduce inflammatory response in these patients.

Cardiac structure and apnea/hypopnea index in patients with arterial hypertension and excessive weight

BACKGROUND/AIMS

Arterial hypertension is frequently associated with sleep apnea, excessive weight, and with changes in the echocardiographic characteristics of the left cardiac chambers. The present investigation was conducted in order to search for a possible relation between left cardiac structure and sleep apnea magnitude in patients with arterial hypertension and excessive weight.

METHODS

A group of 56 patients with arterial hypertension and mean body mass index of 30.6 +/- 3.8 (weight in kilograms/height in meters squared) was studied by echocardiography, sleep study and electrocardiography.

RESULTS

A relatively high mean apnea-hypopnea index (AHI) was found (17.9 +/- 17.2 episodes/h sleep), but this parameter was not found to be correlated with cardiac echocardiographic diameters. Patients with an AHI <5 episodes/h had smaller mean values for left atrial diameter, left ventricular mass index and left ventricular relative wall thickness, when compared to patients with an AHI value of > or =5. The mean corrected QT interval was found to be longer in female patients, whereas left ventricular end-diastolic diameter was smaller than in male patients.

CONCLUSION

In patients with arterial hypertension and excessive weight, significant apnea seems to be very common. In such patients, left ventricle wall thickness, left ventricle mass index and the left atrium diameter may act as surrogate markers for significant sleep apnea. Thus, the hypothesis is raised that hypoxia may lead to changes in heart structure.