Alex Shipolini

A meta-analysis of cognitive outcome following coronary artery bypass graft surgery

Coronary artery bypass graft (CABG) surgery is an established treatment for complex coronary artery disease. There is a widely held belief that cognitive decline presents post-operatively. A consensus statement of core neuropsychological tests was published in 1995 with the intention of guiding investigation into this issue. We conducted a meta-analysis evaluating the evidence for cognitive decline post-CABG surgery. Twenty-eight published studies, accumulating data from up to 2043 patients undergoing CABG surgery, were included. Results were examined at very early (<2 weeks), early (3 months) and late (6-12 months) time periods post-operatively. Two of the four tests suggested an initial very early decrease in psychomotor speed that was not present at subsequent testing. Rather, the omnibus data indicated subtle improvement in function relative to pre-operative baseline testing. Our findings suggest improvement in cognitive function in the first year following CABG surgery. This is contrary to the more negative interpretation of results of some individual publications included in our review, which may reflect poor outcomes in a few patients and/or methodological issues.

Fixing hearts and protecting minds: a review of the multiple, interacting factors influencing cognitive function after coronary artery bypass graft surgery.

Ischemic heart disease is a significant cause of mortality and morbidity in Western populations. Consistent with this, coronary artery bypass graft (CABG) surgery remains one of the most frequently performed major surgeries. Improved survival rates mean that our research focus now extends beyond surgical technique to include quality of postoperative outcome. Postoperative cognitive dysfunction (POCD) has emerged as one of the most challenging and hotly debated issues, with increasing impetus to answer the unresolved question: does fixing the heart come at a cost to the brain?nnCABG surgery is associated with neurological events including stroke in 1.6%1 and delirium in 5.8%2 of patients. Beyond these severe and marked alterations to neurological function, there has been a widely held belief that CABG surgery is associated with POCD, which may presage a decline toward dementia. Research has been influenced by the 1995 Consensus Statement3 into the study of POCD in patients undergoing CABG surgery. Although the methods of investigation set forth by the Consensus Statement achieved widespread acknowledgment, its specific recommendations have not always been followed.4 Despite significant methodological issues, it seems that the balance of interpretation has historically been in favor of CABG surgery as a cause of significant POCD. More recently, however, a review of a series of publications from a well-controlled longitudinal cohort study conducted at Johns Hopkins5 and a meta-analysis6 suggested that cognition is in fact stable or may even show some improvement after CABG surgery in the majority of patients, at least within the first year (Figures 1 and 2). There is little doubt that POCD affects some patients in the short term, but the pathophysiological mechanisms underlying this and the influence on longer-term cognitive function remain uncertain. For research to progress, we require a paradigmatic shift in our focus from …

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].