Undiagnosed sleep apnoea syndrome in patients with acute myocardial infarction: potential importance of the STOP-BANG screening tool for clinical practice.

Sleep apnoea hypopnea syndrome (SAHS) has been identified as an independent risk factor for adverse cardiovascular events in patients admitted with an acute coronary syndrome (ACS) [1]. Most people with SAHS, including those with ACS, are undiagnosed. Konecny and colleagues [2] reported a prevalence of previously diagnosed or suspected SAHS (specificall obstructive sleep apnoea) of 14% among 74 patients with acute MI. However, the frequency of SAHS defined by overnight polysomnography (PSG) was 69%, more than half of whom had PSG findings indicative of moderate–severe SAHS. Whilst PSG is the gold standard for the diagnosis of SAHS, it is time consuming and costly to perform, and its routine application to patients with ACS is impractical. By contrast, a simple screening tool capable of stratifying patients into high and low risk groups for SAHS could potentially be applied to this patient group. The STOP-BANG screen for SAHS comprises four binary questions and four items, paraphrased here as: Snore?, Tiredness during daytime?,Observed apnoea?, High Blood Pressure?, Body mass index, Age, Neck circumference and Gender [3]. We applied the STOP-BANG screen to all patients admitted with acute MI within a one month period to a tertiary referral centre, an urban general hospital and a rural general hospital. A total of 135 patients were diagnosed with MI during the study period. 101 (75%) were male, the mean age was 66±14.6 years, and the mean body mass index (BMI) was 28±5.7 kg/m. There was no significant difference in these variables between the three centres. A STOP-BANG score suggestive of SAHS (≥3) was present in 100 (74%) patients. The two patients who had a pre-existing diagnosis of SAHS both had a STOP-BANG score suggesting high risk of SAHS (6,7). The proportion of significant scores was similar across centres (P=0.88). A significant score was more common in males compared with females (83% v 47%; χ=17.3, Pb0.001) and this was not explained by BMI. In this study of patients presenting with ACS to UK hospitals, 74% of those with confirmedMI had a STOP-BANG score suggestive of preexisting SAHS. While this proportion appears surprisingly high, our data are consistent with those from two recent PSG-based studies of patients with acute MI. In these studies, the prevalence of SAHS defined by an apnoea hypopnea index (AHI) >5, was 68.9% and 74.9%, respectively (Fig. 1) [2,4]. For patients with an AHI>5 the sensitivity of the STOP-BANG for SAHS is 83.6%, rising to 92.9% for those with an AHI>15 [3]. In the present study population, the STOP BANG is likely to have identified the majority of patients across the spectrum of SAHS severity but with greatest sensitivity implied for those with moderate–severe SAHS. That only two of our patients who had significant STOP-BANG scores had a prior diagnosis of SAHS reinforces the finding of Konecny and colleagues [2] that this potentially important underlying condition is not well recognised. The high sensitivity of the STOP-BANG makes it a potentially useful screening tool for SAHS and its simplicity means that it is ideal for use in patients presenting with acute MI. Indeed, we were able to apply the STOP-BANG to all patients who presented with MI whereas studies utilising PSG have generally excluded patients with co-morbidities such as diabetes [4], COPD, stroke and valvular heart disease [5], and concomitant treatment with sedatives and narcotics [5].