Letter to the Editor
Left atrial diameter is independently associated with arterial stiffness in patients with obstructive sleep apnea: Potential implications for atrial fibrillation

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Abstract

Background

Obstructive sleep apnea (OSA) is associated with increased risk for the occurrence and recurrence of atrial fibrillation. However, the mechanisms involved are poorly understood.

Methods

We studied 73 middle-aged subjects divided in two groups: with moderate-to-severe OSA (apnea–hypopnea index [AHI]  15 events/h) or without OSA (AHI  5 events/h) by polysomnography. The groups were matched for age, sex, body mass index and hypertension diagnosis. Carotid–femoral pulse wave velocity (a non invasive measurement of arterial stiffness of the aorta) and transthoracic echocardiography were performed in all participants.

Results

As expected, patients with OSA presented higher AHI than patients without OSA (49.6 ± 21.5 vs. 3.3 ± 1.4 events/h; P < 0.001). Compared with subjects without OSA, pulse wave velocity (9.6 ± 1.5 vs. 10.7 ± 1.8 m/s; P < 0.001) and left atrial diameter (34.7 ± 3.2 vs. 37.6 ± 3.3 mm; P < 0.001) were significantly increased in patients with OSA. Pulse wave velocity significantly correlated with left atrial diameter (r = 0.45; P < 0.001). Multivariate regression analysis showed that AHI and systolic blood pressure were the only independent determinants of pulse wave velocity (F = 30.5; r2 = 0.48; P < 0.01). The only independent variable associated with left atrial diameter was pulse wave velocity.

Conclusions

Left atrial diameter is significantly increased and independently associated with arterial stiffness in patients with OSA. This potential mechanism of atrial remodeling may contribute to explain the increase risk of atrial fibrillation in these patients.

Introduction

Obstructive sleep apnoea (OSA) is associated with 2 to 3 fold increased risk for the occurrence of atrial fibrillation [1]. Moreover, patients with untreated OSA have a higher recurrence of atrial fibrillation after cardioversion after one year than patients without OSA [2]. However, the mechanisms by which OSA predisposes to atrial fibrillation are poorly understood. It is well established that enlarged left atrial size is an independent risk factor for atrial fibrillation [3]. Recent evidences suggested that OSA is associated with vascular and heart remodeling [4]. For instance, we previously demonstrated that OSA is independently associated with increased arterial stiffness of the aorta (determined by carotid–femoral pulse wave velocity—PWV) [4]. In the present investigation, we tested the hypothesis that the increased arterial stiffness observed in OSA patients is independently associated with left atrial diameter.

Section snippets

Methods

The local Ethics Committee approved the protocol, and all participants gave written informed consent.

We studied subjects with moderate-to-severe OSA (apnea–hypopnea index [AHI]  15 events/h) and without OSA (AHI  5 events/h by polysomnography). The groups were matched for age, sex, body mass index and hypertension diagnosis. Hypertension was diagnosed according to current guidelines [5]. In order to avoid acute effects of antihypertensive treatment, patients did not take medications on the day

Results

We initially selected 50 controls and 50 patients with moderate-to-severe OSA according to our inclusion/exclusion criteria. Because of the presence of OSA detected by the polysomnography, we excluded 15 participants in the control group. Five participants refused to perform one or more exams and were also excluded. On the other hand, we excluded 7 patients with OSA that had already initiated treatment with continuous positive airway therapy.

The 2 groups studied were similar in respect to

Discussion

Our study provides important insights on the association between OSA and atrial fibrillation, including (1) OSA is associated with increased left atrial diameter and arterial stiffness; (2) OSA is independently associated with arterial stiffness in the multivariate analysis; (3) Arterial stiffness is an independent factor associated with left atrial diameter. Since increased arterial stiffness of the aorta contributes significantly to increase left ventricular afterload [8], our results

Sources of funding

The study was supported by the FAPESP, the CNPq and the Fundação Zerbini.

Acknowledgement

The author of this manuscript has certified that he complies with the Principles of Ethical Publishing in the International Journal of Cardiology [15].

References (15)

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    Citation Excerpt :

    Two main factors may contribute to atrial remodeling in OSA: (1) chronic atrial dilation by repetitive changes in intrathoracic pressure24 and (2) surges in blood pressure. In addition, OSA has been shown to increase aorta stiffness that in turn contributes to increased heart afterload and atrial and ventricular remodeling.25,26 In the past 2 decades, growing evidence has suggested the potential role of OSA in the genesis of AF occurrence and recurrence.27,28

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