Peak time of acute coronary syndrome in patients with sleep disordered breathing

The Nadir Oxygen-Specific Heart Rate Response in Sleep Apnea Links With the Occurrence of Acute Myocardial Infarction

Background

Little is known regarding the quantification of sleep apnea- and hypoxemia-elicited heart rate (HR) response and its prognostic significance of the cardiovascular risk. We sought to explore the impact of HR response and variability specific to obstructive sleep apnea (OSA) on the occurrence of a common cardiovascular event - acute myocardial infarction (AMI).

Methods

Consecutive patients with suspected OSA were enrolled and underwent nocturnal respiratory study and electrocardiography monitoring. The minimal oxygen saturation (minSpO2) was determined from the oxygen saturation curve under a subject-specific search window. Primary HR metrics such as maximal HR in response to minSpO2 and respiratory event-specific HR variability were computed from the synchronized recordings. Multivariate regression analyses were conducted to analyze the associations between individualized HR metrics and the occurrence of AMI.

Results

Of 2,748 patients recruited, 39% (n = 1,071) had moderate-to-severe OSA (respiratory event index, REI ≥ 15), and 11.4% (n = 313) patients had AMI. Patients with AMI experienced severe OSA, severe minSpO2, and greater HR reactions. Patients with minSpO2 <90% had an adjusted odds ratio (OR) of 1.48 [95% confidence interval (CI): 1.09-2.00, p = 0.012) for AMI. Notably, minSpO2-induced elevated mean HR response (HRmean > 73 bpm) was significantly associated with AMI (OR 1.72, 95% CI: 1.32-2.23, p < 0.001). Patients with both severe minSpO2 (<90%) and elevated HRmean carried an additive OR of 2.65 (95% CI: 1.74-4.05, p < 0.001) for the risk of AMI after adjustment for potential confounders. A large total power spectrum specific to respiratory events was correlated with an adjusted OR of 0.61 for AMI risk.

Conclusion

Patients with substantial HR reactions to OSA-induced oxygen nadir and restricted cardiac cycle shifting to respiratory events were likely at increased risk of developing AMI. Detection of nocturnal HR response to hypoxemia may help improve cardiovascular risk stratification.

Obstructive Sleep Apnea-Induced Neurogenic Nocturnal Hypertension: A Potential Role of Renal Denervation?

There is a bidirectional, causal relationship between obstructive sleep apnea (OSA) and hypertension. OSA-related hypertension is characterized by high rates of masked hypertension, elevated nighttime blood pressure, a nondipper pattern of nocturnal hypertension, and abnormal blood pressure variability. Hypoxia/hypercapnia-related sympathetic activation is a key pathophysiological mechanism linking the 2 conditions. Intermittent hypoxia also stimulates the renin-angiotensin-aldosterone system to promote hypertension development. The negative and additive cardiovascular effects of OSA and hypertension highlight the importance of effectively managing these conditions, especially when they coexist in the same patient. Continuous positive airway pressure is the gold standard therapy for OSA but its effects on blood pressure are relatively modest. Furthermore, this treatment did not reduce the cardiovascular event rate in nonsleepy patients with OSA in randomized controlled trials. Antihypertensive agents targeting sympathetic pathways or the renin-angiotensin-aldosterone system have theoretical potential in comorbid hypertension and OSA, but current evidence is limited and combination strategies are often required in drug resistant or refractory patients. The key role of sympathetic nervous system activation in the development of hypertension in OSA suggests potential for catheter-based renal sympathetic denervation. Although long-term, randomized controlled trials are needed, available data indicate sustained and relevant reductions in blood pressure in patients with hypertension and OSA after renal denervation, with the potential to also improve respiratory parameters. The combination of lifestyle interventions, optimal pharmacological therapy, continuous positive airway pressure therapy, and perhaps also renal denervation might improve cardiovascular risk in patients with OSA.

Blood-pressure variability in patients with obstructive sleep apnea: current perspectives

Obstructive sleep apnea (OSA) is often associated with hypertension and other cardiovascular diseases. Blood pressure (BP) variability is part of the assessment of cardiovascular risk. In OSA, BP variability has been studied mainly as very short-term (beat-by-beat) and short-term (24-hour BP profile) variability. BP measured on consecutive heartbeats has been demonstrated to be highly variable, due to repeated peaks during sleep, so that an accurate assessment of nocturnal BP levels in OSA may require peculiar methodologies. In 24-hour recordings, BP frequently features a "nondipping" profile, ie, <10% fall from day to night, which may increase cardiovascular risk and occurrence of major cardiovascular events in the nocturnal hours. Also, BP tends to show a large "morning BP surge", a still controversial negative prognostic sign. Increased very short-term BP variability, high morning BP, and nondipping BP profile appear related to the severity of OSA. Treatment of OSA slightly reduces mean 24-hour BP levels and nocturnal beat-by-beat BP variability by abolishing nocturnal BP peaks. In some patients OSA treatment turns a nondipping into a dipping BP profile. Treatment of arterial hypertension in OSA usually requires both antihypertensive pharmacological therapy and treatment of apnea. Addressing BP variability could help improve the management of OSA and reduce cardiovascular risk. Possibly, drug administration at an appropriate time would ensure a dipping-BP profile.

Prevalence of sleep-disordered breathing in acute coronary syndrome: a systemic review and meta-analysis

PURPOSE

This study aimed to review the literature on the prevalence of sleep-disordered breathing (SDB) in patients with acute coronary syndrome (ACS).

METHODS

Relevant studies were searched on PubMed, EMBASE, and Cochrane Library through December 2014. Data were extracted using standardized forms. Pooled prevalence of all SDB (apnea-hypopnea index (AHI) > 5), moderate-to-severe SDB (AHI > 15), and severe SDB (AHI > 30) in ACS patients was calculated using DerSimonian-Laird random-effects model. Sensitivity analysis was performed based on races and diagnostic methods of SDB.

RESULTS

A total of 32 studies were included in the present meta-analysis, examining 3360 patients. The meta-analysis indicated that pooled prevalence of all SDB (AHI > 5), moderate-to-severe SDB (AHI > 15), and severe SDB (AHI > 30) in ACS patients were 69 % (95 % confidence interval (CI) = 61, 77 %), 43 % (95 % CI = 36, 49 %), and 25 % (95 % CI = 17, 33 %), respectively. Sensitivity analysis indicated that the pooled prevalence of SDB in Western population was similar to that in Asian population. However, diagnostic methods of SDB seemed to have various impacts on the prevalence of all SDB (AHI > 5), moderate-to-severe SDB (AHI > 15), and severe SDB (AHI > 30).

CONCLUSIONS

High prevalence of all SDB, moderate-to-severe SDB, and severe SDB was found in ACS patients. It is clinically important to screen for SDB in patients with ACS.

Circadian variability of fibrinolytic markers and endothelial function in patients with obstructive sleep apnea

STUDY OBJECTIVES

Obstructive sleep apnea (OSA) is strongly associated with cardiovascular disease, including stroke and acute coronary syndromes. Plasminogen activator inhibitor-1 (PAI-1), the principal inhibitor of tissue-type plasminogen activator (t-PA), has a pronounced circadian rhythm and is elevated in both OSA and cardiovascular disease and may be an important link between the two conditions. Endothelial dysfunction is one of the underlying pathophysiological mechanisms of cardiovascular disease, and may be altered in OSA. Our primary aim was to compare circadian variability of PAI-1 and t-PA in patients with OSA and normal controls by determining the amplitude (peak level) and mesor (rhythm adjusted mean) of PAI-1 and t-PA in serial blood samples over a 24-h period. The secondary aim was to measure markers of endothelial function (brachial and radial artery flow) in patients with OSA compared with normal controls.

SETTING

Cross-sectional cohort study.

PATIENTS OR PARTICIPANTS

Subjects age 18 y or older, with a body mass index of 25-45 kg/m(2), with or without evidence of untreated OSA.

INTERVENTIONS

Plasma samples were collected every 2 h, in OSA patients and matched controls, over a 24-h period. PAI-1 and t-PA antigen and activity were measured. The presence or absence of OSA (apnea-hypopnea index of 5 or greater) was confirmed by overnight polysomnography. Endothelial function was measured via brachial artery flow mediated vasodilatation and computerized arterial pulse waveform analysis.

MEASUREMENTS AND RESULTS

The rhythm-adjusted mean levels of PAI-1 antigen levels in the OSA group (21.8 ng/mL, 95% confidence level [CI], 18 to 25.7) were significantly higher as compared to the non-OSA group (16 ng/mL, 95% CI, 12.2 to 19.8; P = 0.03). The rhythm-adjusted mean levels of PAI-1 activity levels in the OSA group (23.9 IU/mL, 95% CI, 21.4 to 26.5) were also significantly higher than in the non-OSA group (17.2 IU/ mL, 95% CI, 14.6 to 19.9; P < 0.001).There were strong correlations between amplitude of PAI-1 activity and severity of OSA as measured by AHI (P = 0.02), and minimum oxygen levels during sleep (P = 0.04). Endothelial function parameters did not differ significantly between the two groups.

CONCLUSION

The presence of obstructive sleep apnea adversely affects circadian fibrinolytic balance with higher mean plasminogen activator inhibitor-1 activity and antigen, and significantly lower mean tissue-type plasminogen activator activity compared with controls. This perturbation may be an important mechanism for increased cardiovascular events in patients with obstructive sleep apnea. Intermittent hypoxia and changes in circadian clock gene activity in obstructive sleep apnea may be responsible for these findings and warrant further study. Favorable changes in fibrinolytic balance may underlie the reduction in cardiovascular events observed with the treatment of obstructive sleep apnea.

Development and Validation of Sleep Disturbance Questionnaire in Patients with Acute Coronary Syndrome

Background and Objectives. Severe sleep disturbance is a common problem among patients in cardiac care units (CCUs). There are questionnaires to measure sleep disturbances. Therefore, the present study seeks to design a valid and reliable questionnaire to assess sleep disturbance in patients with acute coronary syndrome (ACS) hospitalized in CCUs. Materials and Methods. In the present methodological research, items of the questionnaire were extracted through a systematic review. The validity and reliability of the questionnaires was assessed by face validity, content validity, construct validity, Cronbach's alpha coefficient, and test-retest methods. Results. Factor analysis provided a questionnaire of 23 items on 5 dimensions of sleep disturbance in coronary patients: “sleep onset and continuity disorder,” “disorder in daytime functioning,” “sleep disturbance caused by environmental factors,” “sleep disturbance as a result of cardiac diseases,” and “respiratory disorders during sleep.” Furthermore, test-retest analysis showed a reliability correlation coefficient of r = 0.766 and α Cronbach's reliability (α = 0.855). Conclusion. Sleep disturbance questionnaire for patients with ACS hospitalized in coronary care unit (CCU) was identified in 5 dimensions and assessed for validity and reliability. To control and improve the sleep quality of CCU hospitalized patients, we need to identify and remove predisposing factors.

The association of sleep disordered breathing with heart failure and other cardiovascular conditions

An abundance of evidence exists in support of primary and secondary prevention for tackling the scourge of cardiovascular disease. Despite our wealth of knowledge, certain deficiencies still remain. One such example is the association between sleep disordered breathing (SDB) and cardiovascular disease. A clear body of evidence exists to link these two disease entities (independent of other factors such as obesity and smoking), yet our awareness of this association and its clinical implication does not match that of other established cardiovascular risk factors. Here, we outline the available evidence linking SDB and cardiovascular disease as well as discussing the potential consequences and management in the cardiovascular disease population.

Clinical correlates of insomnia in patients with acute coronary syndrome

This study sought to examine the prevalence of insomnia and its association with depression, anxiety, and medical comorbidities in patients after an acute coronary syndrome (ACS). Insomnia increases risk of recurrent cardiac events in ACS patients, but little is known about the prevalence and clinical correlates of insomnia in this setting. Patients (n = 102, 58.3 ± 10.6 years-old) admitted for ACS to a cardiology service at an urban academic medical center completed the Insomnia Severity Index, Epworth Sleepiness Scale, and measures of depression and anxiety. A subset (n = 20) completed ambulatory polysomnography (PSG) in their homes several weeks after discharge. Moderate or severe insomnia was reported by 37% of patients during hospitalization and was associated with 76 minutes more wake after sleep onset measured by home PSG. Although depression and insomnia were strongly associated, about 1 in 4 patients with insomnia did not report significant depressive symptoms. Sleep apnea was documented in 80% of patients on PSG, but insomnia was not associated with sleep apnea, periodic limb movements, demographic factors, or medical conditions other than liver disease. Insomnia is present in over one-third of ACS patients during hospitalization, but at-risk patients could not be readily identified by demographic or medical factors or by depression symptoms.

Impact of sleep-disordered breathing, visceral fat accumulation and adiponectin levels in patients with night-time onset of acute coronary syndrome

Acute coronary syndrome (ACS) during sleep occurs at a relatively low frequency and the pathogenic background remains uncertain. The aim of the present study was to determine the significance of sleep-disordered breathing (SDB) and excess visceral fat with nocturnal dysregulation of adipocytokines in night-time onset of ACS. SDB, visceral fat area (VFA), and changes in circulating adipocytokine levels were assessed in 109 consecutive patients with ACS. SDB and VFA were assessed by cardiorespiratory monitoring and computed tomographic scan, respectively. Visceral fat accumulation was more common in patients with (12 to 7 a.m.) than without (7 to 12 a.m.) night-time onset of ACS (p <0.05). In patients with night-time onset of ACS, those with excess visceral fat were significantly more likely to have SDB and nocturnal dysregulation of adiponectin than those without such accumulation (p <0.05), but there was no difference between those with and without excess visceral fat (VFA cutoff 100 cm(2)) in patients with non-night-time onset of ACS. In conclusion, night-time onset of ACS is associated with excess visceral fat and SDB (referred as to "syndrome Z"). SDB and excess visceral fat are treatable risk factors. Decrease of excess visceral fat and treatment of SDB could be beneficial in in preventing nocturnal cardiac events.

Effectiveness of a portable device and the need for treatment of mild-to-moderate obstructive sleep-disordered breathing in patients with cardiovascular disease

BACKGROUND AND PURPOSE

In Japan, there are two sleep-disordered breathing (SDB)-related problems, which include diagnosing SDB using a portable device (PD) and treating mild-to-moderate SDB (mm-SDB) using continuous positive airway pressure (CPAP) for severe SDB (s-SDB) in obstructive sleep apnea (OSA) patients. Our aims were to evaluate the effectiveness of a PD in diagnosing SDB in patients with cardiovascular disease (CVD), and to assess the difference between mm-SDB [apnea-hypopnea index (AHI): 20-40h(-1)] and s-SDB (AHI: >40h(-1)) using brain natriuretic peptide (BNP) in OSA patients.

METHODS AND SUBJECTS

After their underlying CVD was treated, full-night sleep studies using polysomnography (PSG) and PD were performed on the same day.

RESULTS

Eighty-three patients underwent full-night PSG simultaneously with PD. The average duration of the sleep study was 8.6+/-6.2 days. There was a tendency for a higher AHI value obtained with PSG (PSG, 28.9+/-24.3h(-1); PD, 22.3+/-16.7h(-1); p=0.05). However, the specificity and sensitivity of diagnosing SDB using PD were 86% and 81%, respectively. Using PD, twenty-nine OSA patients had mm-SDB and eleven patients had s-SDB. The BNP value was higher in the mm-SDB patients (318+/-550pg/ml) than in the s-SDB patients (202+/-160pg/ml).

CONCLUSIONS

The PD was effective in diagnosing SDB in patients with CVD. The BNP value was higher in the mm-SDB patients. Therefore, they need to be treated with CPAP to treat underlying CVD.

Obstructive sleep apnea and cardiovascular disease

Over the past few decades, sleep apnea has emerged as an important potential etiologic factor in a broad range of cardiac and vascular diseases. These disease conditions include hypertension, coronary artery disease, myocardial infarction, heart failure, and stroke. Recognition of the role of sleep apnea in clinical cardiology is also increasing in Japan. Although sleep apnea has been strongly linked to obesity in Western populations, in Japanese and other Asian populations there is evidence to indicate that sleep apnea may be prevalent even at lower levels of obesity. In this review we address the epidemiology of sleep apnea. Since sleep apnea includes the combined stresses of hypoxemia, apnea, and disrupted sleep, we also review briefly the potential disease mechanisms that may be activated as a consequence of sleep apnea. We further examine the role of sleep apnea in the pathophysiology and management of specific cardiovascular conditions. Overall, while the evidence of sleep apnea as a causal mechanism in cardiovascular disease is strong and increasing, definitive evidence of the etiologic role of sleep apnea has yet to be obtained. The evidence is most clear in patients with hypertension. Also remaining to be established is whether the treatment of sleep apnea prevents cardiac and vascular events. With regard to this question, although the available data strongly suggest that continuous positive airway pressure treatment is beneficial, randomized control trials are needed in order to confirm this.