Left Atrial Volume and Function in Patients With Obstructive Sleep Apnea Assessed by Real-Time Three-Dimensional Echocardiography

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Background

Studies have suggested that obstructive sleep apnea (OSA) contributes to the deterioration of left ventricular diastolic function. This may lead to atrial myocardial overstretching and enlargement, which could be associated with increased cardiovascular risk. The aim of this study was to evaluate left atrial (LA) volume and function in patients with OSA compared with controls without OSA and their associations with any left ventricular diastolic abnormalities using real-time 3-dimensional echocardiography (RT3DE).

Methods

Fifty-six patients with mild to severe OSA and 50 controls of similar age and with similar body mass indexes, blood pressure, and frequency of hypertension were analyzed. All subjects underwent polysomnography and RT3DE.

Results

A larger 3-dimensional maximum LA volume indexed for body surface area, larger volume before atrial contraction, and higher active atrial ejection fraction were found in patients with OSA (P < .01 for all). Mitral annular early diastolic velocity (E′) was reduced in patients with OSA (P = .03), whereas late diastolic velocity (A′) and the ratio of mitral valve early diastolic velocity to mitral annular early diastolic velocity (E/E′) were increased in the same group (P < .05 for both). In addition, a lower E′/A′ ratio was also found in the OSA group (P = .02). An increase in 3-dimensional maximum LA volume indexed for body surface area was observed, depending on OSA severity. The apnea-hypopnea index and E/E′ ratio were independent predictors of an increase in 3-dimensional maximum LA volume in a multiple regression model.

Conclusion

Using RT3DE, this study demonstrates that OSA induces a functional burden on the left atrium, resulting in remodeling. These functional and structural changes are related to the impairment of diastolic function in this population.

Section snippets

Population

Fifty-six recently diagnosed, nontreated patients with OSA, aged 29 to 70 years (29 men), were recruited and referred to the Sleep Laboratory of the Federal University of São Paulo (São Paulo, Brazil). The diagnoses of OSA were confirmed by full polysomnography in conjunction with the requirement that patients present with apnea-hypopnea index values > 5 events/hour of sleep.

One hundred eighteen age-matched community subjects were invited to participate in this study as controls. The main

General Results

A total of 56 patients with mild to severe OSA and 50 control subjects without OSA were included in this study. As expected, the mean age did not significantly differ between groups, as shown in Table 1. Patients with OSA had greater neck circumferences compared with controls, but the frequencies of male gender, hypertension, and diabetes were similar in both groups. Additionally, BMI, heart rate, and systolic and diastolic blood pressure values were similar in both groups.

Polysomnographic Findings

The apnea-hypopnea

Discussion

The main findings of the current study were a significant increase in LA volume and augmentation of LA active systolic function associated with the impairment of left ventricular diastolic function in patients with OSA compared with controls as analyzed using RT3DE. Our study is the first to analyze subjects with OSA those without while controlling for confounding factors, such as hypertension and obesity, and the first to demonstrate LA functional differences between the 2 groups.

Conflicting

Conclusion

Using RT3DE, we demonstrated that OSA places a functional burden on the left atrium, resulting in remodeling. These functional and structural changes are related to diastolic impairment independent of hypertension, obesity, and diabetes mellitus. These patterns appear to increase according to OSA severity.

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This study was supported by Fundação de Apoio a Pesquisa do Estado de São Paulo; grants from Centros de Pesquisa, Inovação e Difusão; and Associação Fundo de Incentivo à Psicofarmacologia.

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