Effects of Obstructive Sleep Apnea and its Treatment on Signal-Averaged P-Wave Duration in Men

Cross-Sectional Relationship Between Atrial Conduction Delay and Arterial Stiffness in Patients with Obstructive Sleep Apnea

Aim

Prolonged P-wave duration (PWD), which indicates atrial conduction delay, is a potent precursor of atrial fibrillation (AF) that may be induced by obstructive sleep apnea (OSA). The cardio-ankle vascular index (CAVI), which is an arterial stiffness parameter, is elevated in patients with OSA; moreover, an increased CAVI is associated with atrial conduction delay through left atrium enlargement in association with left ventricular diastolic dysfunction. We aimed to examine the relationship between the CAVI and PWD in patients with OSA.

Methods

We included patients with a sinus rhythm who underwent overnight polysomnography. We measured the PWD and CAVI on standard 12-lead electrocardiograms; further, we analyzed the relationship between PWD and CAVI.

Results

We analyzed data from 300 participants (men, 89.0%; mean age, 52.3 ± 13.1 years; and body mass index, 26.2 ± 3.9 kg/m2). The mean PWD was 104.4 ± 10.4 ms while the mean CAVI was 7.5 ± 1.5. PWD was significantly correlated with CAVI (r = 0.478, p < 0.001); additionally, PWD and CAVI were directly associated with OSA severity (p = 0.002 and p = 0.002, respectively). Multivariate regression analysis revealed an independent significant correlation of PWD and CAVI with OSA severity.

Conclusion

In patients with OSA, an increase in arterial stiffness is associated with atrial conduction delay.

Impact of CPAP on the Atrial Fibrillation Substrate in Obstructive Sleep Apnea: The SLEEP-AF Study

BACKGROUND

Observational studies report that obstructive sleep apnea (OSA) is associated with an increasingly remodeled atrial substrate in atrial fibrillation (AF). However, the impact of OSA management on the electrophysiologic substrate has not been evaluated.

OBJECTIVES

In this study, the authors sought to determine the impact of OSA management on the atrial substrate in AF.

METHODS

We recruited 24 consecutive patients referred for AF management with at least moderate OSA (apnea-hypopnea index [AHI] ≥15). Participants were randomized in a 1:1 ratio to commence continuous positive airway pressure (CPAP) or no therapy (n = 12 CPAP; n = 12 no CPAP). All participants underwent invasive electrophysiologic study (high-density right atrial mapping) at baseline and after a minimum of 6 months. Outcome variables were atrial voltage (mV), conduction velocity (m/s), atrial surface area <0.5 mV (%), proportion of complex points (%), and atrial effective refractory periods (ms). Change between groups over time was compared.

RESULTS

Clinical characteristics and electrophysiologic parameters were similar between groups at baseline. Compliance with CPAP therapy was high (device usage: 79% ± 19%; mean usage/day: 268 ± 91 min) and resulted in significant AHI reduction (mean reduction: 31 ± 23 events/h). There were no differences in blood pressure or body mass index between groups over time. At follow-up, the CPAP group had faster conduction velocity (0.86 ± 0.16 m/s vs 0.69 ± 0.12 m/s; P (time × group) = 0.034), significantly higher voltages (2.30 ± 0.57 mV vs 1.94 ± 0.72 mV; P < 0.05), and lower proportion of complex points (8.87% ± 3.61% vs 11.93% ± 4.94%; P = 0.011) compared with the control group. CPAP therapy also resulted in a trend toward lower proportion of atrial surface area <0.5 mV (1.04% ± 1.41% vs 4.80% ± 5.12%; P = 0.065).

CONCLUSIONS

CPAP therapy results in reversal of atrial remodeling in AF and provides mechanistic evidence advocating for management of OSA in AF.

Interatrial conduction block in an obstructive sleep apnea patient: An electrical premonitor of atrial fibrillation

Obstructive sleep apnea (OSA) is an important sleep disorder and is associated with increased cardiovascular morbidity and mortality. Several recent studies have demonstrated an association OSA and atrial fibrillation (AF). Therefore, it is of great importance understanding the pathophysiological substrate and the interaction between OSA and AF. Moreover, it is well accepted that interatrial block (IAB), evaluated not only by the P-wave duration but also by the P-wave morphology, has the potential to give information about the anatomical substrate predisposing to AF. OSA and AF share many risk factors and comorbidities, including older age, male gender, obesity, hypertension, heart failure, and coronary artery diseases. IAB is defined when the P-wave is ≥120 ms which signifies excessive time for sinus impulses to conduct from the right atrium to the left atrium and may predict future AF events. Accordingly, recent studies have suggested that OSA is associated with atrial functional and structural remodeling which indeed are associated with increased risk of AF. We speculate that IAB, a known factor to predict future AF episodes, may associate with OSA and contribute to the development of arrhythmic events. In the present case, the report presents a woman with OSA and IAB on the surface electrocardiogram (ECG)automatic P-wave analysis and some short episodes of AF in the external event recorder monitoring.

Signal-averaged P wave area increases during respiratory events in patients with paroxysmal atrial fibrillation and obstructive sleep apnea

PURPOSE

P wave characteristics change during simulated apneic events in individuals with atrial fibrillation (AF). This study sought to assess whether similar changes occur during nocturnal respiratory events in patients with AF and obstructive sleep apnea (OSA).

METHODS

Thirty-five individuals with severe OSA who underwent formal polysomnography and subsequent AF ablation were compared to a matched group without AF. Electrocardiographic segments from each polysomnogram corresponding to the following events were identified: period of wakefulness closest to the initial onset of sleep (baseline-awake), first respiratory event, respiratory event with the lowest nadir oxygen saturation, longest respiratory event, and last respiratory event. Signal-averaged P wave duration and signal-averaged positive P wave area (amplitude*duration for positive P wave amplitudes) were extracted using custom software. P wave characteristics during respiratory events and the baseline-awake condition were compared.

RESULTS

Compared to the baseline-awake condition, the signal-averaged positive P wave area was significantly greater during the longest event and the event with the lowest oxygen saturation in those with AF, but not in those without AF. There were no significant differences in signal-averaged P wave duration for any respiratory event compared to the baseline-awake condition, regardless of AF status.

CONCLUSION

In patients with paroxysmal AF and obstructive sleep apnea, the signal-averaged positive P wave area is greater during certain respiratory events than during wakefulness. This finding may reflect the acute impact on right atrial volume of increased venous return associated with respiratory events and could be useful to assess AF risk in sleep apnea and to monitor response to treatment.

Association between sleep disordered breathing and electrocardiographic markers of atrial abnormalities: the MESA study

Aims

Electrocardiographic (ECG) markers of left atrial (LA) abnormalities have been linked to increased risk of atrial fibrillation (AF). Sleep disordered breathing (SDB) has been associated with increased risk of AF. We aimed to examine the association of ECG markers of LA abnormalities with SDB.

Methods and results

1546 participants (mean age 67.2 years, 53.4% women, and 63.3% non-whites) from the Multi-Ethnic Study of Atherosclerosis Exam 5 Sleep ancillary study were included in this analysis. ECG markers of LA abnormalities (P wave terminal force in V1 (PTFV1), maximum P wave duration, PR interval and heart rate corrected PR interval) were measured from resting standard digital ECG tracings using standardized processing. Linear and logistic regression analyses were utilized to examine the cross-sectional associations of measures of SDB (apnea hypopnea index [AHI] and % time spent with oxygen saturation <90% [%SpO290]) with each ECG marker. In a multivariable analysis adjusting for demographics, cardiovascular risk factors, and comorbidities, AHI was associated with greater PTFV1 but not with other ECG markers of LA abnormalities. A 1-SD increase of AHI (16.6/hr) was associated with higher levels of PTFV1 (175.1 µV.ms, 95% confidence interval [95%CI] 75.4, 274.7) and higher odds of abnormally elevated PTFV1 (≥4000 µV.ms) (Odds Ratio: 1.21 [95%CI 1.05, 1.39]). No association was found between %SpO290 and ECG markers of LA abnormalities.

Conclusion

Severity of SDB, as measured by AHI, is associated with subclinical LA disease, as indicated by PTFV1. PTFV1 may be an important ECG marker linking SDB and AF.

Sleep, sleep apnea and atrial fibrillation: Questions and answers

Sleep apnea (SA) is a common sleep disorder increasingly recognized as a risk for cardiovascular disease. Atrial fibrillation (AF) is the most common cardiac arrhythmia and is associated with significant morbidity and mortality. An increasing number of investigations in recent years have linked SA to AF. In this review, we aim to provide a critical overview of the existing evidence in a question and answer format by addressing the following: What is the prevalent association between the two conditions (separating nocturnally detected AF episodes from AF as a prevalent condition)? Is SA a risk factor for incident AF? Is SA a risk factor for recurrence of AF following cardioversion/catheter-based ablation? What is the association between SA and AF in patients with heart failure? Are there signature electrocardiographic markers of AF found in patients with SA? Are there electrophysiology-based studies supporting the link between SA and AF? What other sleep characteristics (beyond SA) are found in patients with AF? What is the impact of SA treatment on AF? What is the effect of AF treatment on sleep? Finally, we address unsolved questions and suggest future directions to enhance our understanding of the AF-SA relationship.

OSA and Cardiac Arrhythmogenesis: Mechanistic Insights

A surge of data has reproducibly identified strong associations of OSA with cardiac arrhythmias. As an extension of epidemiologic and clinic-based findings, experimental investigations have made strides in advancing our understanding of the putative OSA and cardiac arrhythmogenesis mechanistic underpinnings. Although most studies have focused on the links between OSA and atrial fibrillation (AF), relationships with ventricular arrhythmias have also been characterized. Key findings implicate OSA-related autonomic nervous system fluctuations typified by enhanced parasympathetic activation during respiratory events and sympathetic surges subsequent to respiratory events, which contribute to augmented arrhythmic propensity. Other more immediate pathophysiologic influences of OSA-enhancing arrhythmogenesis include intermittent hypoxia, intrathoracic pressure swings leading to atrial stretch, and hypercapnia. Intermediate pathways by which OSA may trigger arrhythmia include increased systemic inflammation, oxidative stress, enhanced prothrombotic state, and vascular dysfunction. Long-term OSA-associated sequelae such as hypertension, atrial enlargement and fibrosis, ventricular hypertrophy, and coronary artery disease also predispose to cardiac arrhythmia. These factors can lead to a reduction in atrial effective refractory period, triggered and abnormal automaticity, and promote slowed and heterogeneous conduction; all of these mechanisms increase the persistence of reentrant arrhythmias and prolong the QT interval. Cardiac electrical and structural remodeling observed in OSA animal models can progress the arrhythmogenic substrate to further enhance arrhythmia generation. Future investigations clarifying the contribution of specific OSA-related mechanistic pathways to arrhythmia generation may allow targeted preventative therapies to mitigate OSA-induced arrhythmogenicity. Furthermore, interventional studies are needed to clarify the impact of OSA pathophysiology reversal on cardiac arrhythmogenesis and related adverse outcomes.

Obstructive Sleep Apnea Treatment and Atrial Fibrillation: A Need for Definitive Evidence

Prevalence rates of atrial fibrillation (AF) and obstructive sleep apnea (OSA) are rising on a global scale. Epidemiological data have consistently demonstrated an independent association between the 2 conditions. Investigators pose that pathophysiologic features of OSA enable progression of the AF substrate; these features include abnormalities of gas exchange, autonomic remodeling, atrial stretch, and inflammation. Furthermore, many of the mechanistic perturbations that impact the AF substrate in OSA can be substantially attenuated by effective treatment with continuous positive airway pressure (CPAP). Clear associations of OSA treatment and improved AF control have been observed across multiple clinical contexts. However, the precision and generalizability of these findings are unclear in view of the data's observational nature. Although risk factor management has emerged as a critical component of AF treatment, effective control of many AF risk factors can be challenging in the longer term. In view of the efficacy and sustainability of CPAP therapy, OSA raises its profile as a prime candidate for intervention. However, translation of this strategy to the broader framework for AF management requires robust data from randomized controlled trials.

Simulated Obstructive Sleep Apnea Increases P-Wave Duration and P-Wave Dispersion

Background

A high P-wave duration and dispersion (Pd) have been reported to be a prognostic factor for the occurrence of paroxysmal atrial fibrillation (PAF), a condition linked to obstructive sleep apnea (OSA). We tested the hypothesis of whether a short-term increase of P-wave duration and Pd can be induced by respiratory manoeuvres simulating OSA in healthy subjects and in patients with PAF.

Methods

12-lead-electrocardiography (ECG) was recorded continuously in 24 healthy subjects and 33 patients with PAF, while simulating obstructive apnea (Mueller manoeuvre, MM), obstructive hypopnea (inspiration through a threshold load, ITH), central apnea (AP), and during normal breathing (BL) in randomized order. The P-wave duration and Pd was calculated by using dedicated software for ECG-analysis.

Results

P-wave duration and Pd significantly increased during MM and ITH compared to BL in all subjects (+13.1ms and +13.8ms during MM; +11.7ms and +12.9ms during ITH; p<0.001 for all comparisons). In MM, the increase was larger in healthy subjects when compared to patients with PAF (p<0.05).

Conclusion

Intrathoracic pressure swings through simulated obstructive sleep apnea increase P-wave duration and Pd in healthy subjects and in patients with PAF. Our findings imply that intrathoracic pressure swings prolong the intra-atrial and inter-atrial conduction time and therefore may represent an independent trigger factor for the development for PAF.

ECG risk markers for atrial fibrillation and sudden cardiac death in minimally symptomatic obstructive sleep apnoea: the MOSAIC randomised trial

OBJECTIVE

Obstructive sleep apnoea (OSA), atrial fibrillation (AF) and sudden cardiac death (SCD) may occur concomitantly, and are of considerable epidemiological interest, potentially leading to morbidity and mortality. Effective treatment of OSA with continuous positive airway pressure (CPAP) could prevent progression and/or recurrence of AF and factors leading to SCD. Recently, a randomised controlled trial showed a statistically and clinically significant prolongation of measures of cardiac repolarisation after CPAP withdrawal in symptomatic patients with moderate to severe OSA. Whether or not CPAP therapy improves ECG risk markers of AF and SCD in patients with minimally symptomatic OSA as well, is unknown.

METHODS

3 centres taking part in the MOSAIC (Multicentre Obstructive Sleep Apnoea Interventional Cardiovascular) trial randomised 303 patients with minimally symptomatic OSA to receive either CPAP or standard care for 6 months. Treatment effects of CPAP on P-wave duration, P-wave dispersion, QT interval, QT dispersion, Tpeak-to-Tend (TpTe) and TpTe/QT ratio were analysed.

RESULTS

Participants were primarily men (83%). Mean age was 57.8 (7.2) and mean ODI (Oxygen Desaturation Index) at baseline was 13.1/h (12.3). Full 12-lead ECG data was available in 250 patients. Mean (SD) baseline intervals of P-wave duration, P-wave dispersion, QTc interval, QT dispersion, TpTe and TpTe/QT ratio in ms were 87.4 (8.3), 42.3 (11.9), 397.8 (22.7), 43.1 (16.7), 73.5 (13.7) and 0.19 (0.0), respectively. No treatment effect of CPAP on risk markers for AF and SCD was found.

CONCLUSIONS

There seems to be no effect of CPAP on ECG measures of arrhythmia risk in patients with minimally symptomatic OSA.

TRIAL REGISTRATION NUMBER

ISRCTN34164388; Post-results.

Impact of Continuous Positive Airway Pressure Therapy on Atrial Electromechanical Delay in Obesity-Hypoventilation Syndrome Patients

BACKGROUND

Obesity-hypoventilation syndrome (OHS) is defined as daytime hypercapnia and hypoxemia in obese patients with sleep-disordered breathing. We evaluated the electrocardiographic P-wave duration and dispersion (PD) and echocardiographic noninvasive indicators of atrial conduction heterogeneity in OHS patients and the impact of CPAP on atrial conduction and atrial fibrillation incidence.

METHODS AND RESULTS

We enrolled 50 OHS patients and 50 sex- and age-matched obese subjects as control. Study population underwent cardiologic evaluation and polysomnography before enrollment, at 1- and 6-month follow-ups after CPAP therapy. The OHS group showed a significant increase in inter-atrial (35.2 ± 8 milliseconds vs. 20.1 ± 2.7 milliseconds, P < 0.0001), intra-left (30.5 ± 7.2 milliseconds vs. 16.5 ± 2 milliseconds, P < 0.0001), and intra-right atrial electromechanical delays (AEMD)(24.8 ± 10 milliseconds vs. 15 ± 2.6 milliseconds, P < 0.0001) as well as in Pmax (130 ± 7.4 milliseconds vs. 97 ± 7.2 milliseconds, P = 0.002) and PD (56.5 ± 8.5 milliseconds vs. 31 ± 7.2 milliseconds, P = 0.002) compared to the control group. Significant improvement was noted after 6 months of CPAP therapy in inter-atrial (35.2 ± 8 milliseconds vs. 24.5 ± 6.3 milliseconds, P < 0.0001), intra-left (30.5 ± 7.2 milliseconds vs. 20.6 ± 5 milliseconds, P = 0.003), and intra-right AEMD (24.8 ± 10 milliseconds vs. 17 ± 7.5 milliseconds, P < 0.0001), as well as in Pmax (130 ± 7.4 milliseconds vs. 95 ± 10 milliseconds, P < 0.0001) and in PD (56.5 ± 8.5 milliseconds vs. 32.5 ± 6 milliseconds, P < 0.0001) in the OHS group. External loop recorder monitoring detected paroxysmal AF in 19 OHS patients (38%) with significant reduction in paroxysmal AF episodes (12 ± 6 vs. 47 ± 12, P < 0.0001) after 6-month CPAP therapy.

CONCLUSION

Our findings showed a significant increase of electrocardiographic and echocardiographic indexes of atrial conduction heterogeneity in OHS patients. The CPAP therapy, having a positive impact on atrial conduction time, seems to reduce AF incidence in OHS patients.

Reverse Remodelling of the Atria After Treatment of Obstructive Sleep Apnoea with Continuous Positive Airway Pressure: Evidence from Electro-mechanical and Endocrine Markers

BACKGROUND

Recent studies have suggested a strong association between obstructive sleep apnoea (OSA) and atrial fibrillation (AF). However, the impact of continuous positive airway pressure (CPAP) therapy on reverse atrial remodelling in patients with OSA is poorly understood. We aimed to determine the impact of CPAP therapy on total atrial conduction time measured by PA tissue Doppler imaging (TDI) interval in patients without history of AF.

METHODS AND RESULTS

Thirty-five patients with first diagnosed OSA (group 1) and 20 reference patients without OSA (group 2) were prospectively enrolled. Group 1 was divided into 25 patients with starting CPAP therapy (intervention group) and 10 patients without CPAP therapy (control group). PA-TDI interval, measured by tissue Doppler imaging, and B-type natriuretic-peptide (BNP) were determined at baseline and repeated after 30 days in group 1. Patients with OSA had a significantly longer PA-TDI interval (131.4±16.0 ms vs. 120.1±6.4 ms, p<0.001) compared to reference patients. PA-TDI interval shortened significantly after 30 days of CPAP therapy (131±17.1 ms vs. 124.6±15.7 ms, p<0.001), whereas no significant change was found in the control group (132.6±13.6 ms vs. 133.2±13.1 ms, p=0.31) and BNP-levels decreased significantly (39.1±50.7 pg/ml vs. 28.2±42.4 pg/ml, p<0.01), while BNP-levels remained unaffected after 30 days in control group (31.5±20 pg/ml vs. 34.4±20.5 pg/ml, p=0.41).

CONCLUSIONS

Change in PA-TDI interval, as an indirect surrogate marker of atrial remodelling, suggests reverse atrial remodelling in patients with OSA and treated by CPAP. This effect may ensue from decreased atrial pressure or volume overload, as indicated by significantly reduced BNP levels. These observations suggest that the substrate pre-disposing to AF may be reversible and moreover can be measured by PA-TDI interval and BNP.

P wave duration and dispersion in Holter electrocardiography of patients with obstructive sleep apnea

PURPOSE

The underlying mechanisms of the association between obstructive sleep apnea (OSA) and atrial fibrillation (AF) remained unclear. We investigated P wave parameters as indicators of atrial conduction status among OSA patients.

METHODS

We studied 42 untreated OSA patients, categorized into mild (6), moderate (18), and severe (18) OSA based on the apnea/hypopnea index (AHI) and 18 healthy controls. Twenty-four-hour Holter electrocardiography was applied to measure P wave parameters including P wave duration and P wave dispersion; difference between the maximum (P-max) and minimum (P-min) measured P wave duration.

RESULTS

Mean P wave duration ranged from 110.2 ± 9.3 ms in mild OSA patients to 121.1 ± 15.4 ms in severe OSA patients and was 113.4 ± 10.0 ms in controls with no significant difference among the groups, P = 0.281. P wave dispersion and P-max were significantly longer in those with moderate OSA (68.0 ± 9.3 and 154.2 ± 9.3 ms) and those with severe OSA (71.6 ± 13.7 and 157.2 ± 13.3 ms) than controls (52.6 ± 15.3 and 142.1 ± 15.4 ms), P < 0.05. AHI was significantly correlated with P-max (r = 0.407, P = 0.012) and P wave dispersion (r = 0.431, P = 0.008). With linear regression analysis controlling for age, gender, and BMI, the AHI was independently associated with P wave dispersion (β = 0.482, P = 0.002).

CONCLUSIONS

Using Holter monitoring for measurement of P wave parameters, this study showed an association of OSA with prolonged P-max and P wave dispersion. These results indicate that patients with OSA have disturbances in atrial conduction associated with OSA severity. Repeating this study in a larger sample of patients is warranted.