CPAP effect on recurrent episodes in patients with sleep apnea and myocardial infarction

Abstract

Background

Obstructive sleep apnea (OSA) is linked to increased cardiovascular risk, but the association between OSA and myocardial infarction (MI) remains controversial. Our objectives were to compare the frequency of OSA in patients with acute MI and in a population-based sample of control subjects, and to evaluate the impact of CPAP on recurrent MI and coronary revascularization.

Methods

Case–control study with a 6-year follow-up of the case cohort. 192 acute MI patients and 96 matched control subjects without coronary artery disease (CAD) (ratio 2:1). After overnight polysomnography, CPAP was recommended if apnea–hypopnea index (AHI) ≥ 5, and a mean daily use > 3.5 h/day was considered necessary to maintain the treatment. Lipids, fasting glucose, blood pressure, spirometry, comorbidity and current treatment were also registered. End-points were recurrent MI or need of revascularization.

Results

OSA was an independent predictor of MI, with odds ratio 4.9 (95% confidence interval [CI] 2.9–8.3, p = 0.017). 63 MI patients without OSA, 52 untreated patients with OSA and 71 OSA patients treated with CPAP were included in the follow-up study. After adjustment for confounding factors, treated OSA patients had a lower risk of recurrent MI (adjusted hazard ratio 0.16 [95%CI 0.03–0.76, p = 0.021]) and revascularization (adjusted hazard ratio 0.15 [95%CI 0.03–0.79, p = 0.025]) than untreated OSA patients, and similar to non-OSA patients.

Conclusion

Mild-severe OSA is an independent risk factor for MI. Risk of recurrent MI and revascularization was lower in OSA patients who tolerated CPAP.

Introduction

Obstructive sleep apnea (OSA) is an independent risk factor for cardiovascular morbidity [1]. The prevalence of hypertension is higher in subjects with OSA in a dose-dependent manner [2]. OSA has also been associated with arrhythmias, stroke, and heart failure [3]. Similarly, the incidence of coronary artery disease (CAD) is increased with OSA [4], although the effect is more modest [5].

However, the association of OSA with acute myocardial infarction (MI) remains ambiguous. A number of cross-sectional [6], [7], [8] and case–control [9] studies have reported high rates of OSA in patients with acute coronary syndrome, whereas other studies have failed to clearly demonstrated an independent association between OSA and MI [2], [10]. Some of these studies have been criticized because they often lacked adjustment for important cardiovascular risk factors and due to the selection process of control subjects.

The effect of sleep apnea on prognosis of CAD patients is controversial. Whereas some authors [4], [11] reported an increase in mortality rates, others did not find a significant difference regarding 10-year survival in CAD patients with OSA compared with those without OSA [12]. Although an increased risk of the combined end-point of death, MI, stroke and transient ischemic attack has been described in OSA patients [7], [13], the effect of OSA on the progression of coronary injuries turns out to be less definite. Lee and coworkers [8] did not find an association between OSA and impaired microvascular perfusion after primary percutaneous coronary intervention. In contrast, Nakashima et al. [14] have reported that OSA may impair myocardial tissue perfusion in patients with MI. There is little specific information about the most relevant clinical consequences of the myocardial perfusion affectation, such as the risk of presenting recurrent MI or the need for a new revascularization procedure.

Another important issue is whether elimination of apnea–hypopneas with nasal continuous positive pressure (CPAP) reduces mortality and morbidity after acute MI. In a long-term follow-up study [15], CPAP reduces the risk of cardiovascular events, defined as cardiovascular death, acute coronary syndrome, hospitalization for heart failure, or need for coronary revascularization. However, other authors found that CPAP treatment is associated with a reduction in the number of cardiac deaths, but not in major adverse cardiac or cerebrovascular events [16]. Differences in patient selection, study design, and small study groups could explain the inconsistent results.

The objective of our study was to evaluate the association between OSA and MI and to clarify whether treatment of OSA is associated with a lower recurrence of MI. We aim to compare OSA frequency in patients with acute MI and a population-based sample of subjects without CAD. Moreover, we evaluate the impact of CPAP therapy on recurrent MI and on the need for coronary revascularization over a 6-year period.