Outcomes of coronary artery bypass grafting (CABG) in patients with OSA-COPD overlap syndrome versus COPD alone: an analysis of US Nationwide Inpatient Sample

To the best of our knowledge, this study is the first to investigate outcomes following elective CABG between patients with OSA-COPD overlap versus COPD alone. The analyses found that of patients with COPD and undergoing CABG, 20% had OSA-COPD overlap syndrome. Compared to patients with COPD alone, those with OSA-COPD overlap are more likely to have a non-routine discharge, and overall postoperative complications. Additionally, compared to patients with COPD alone, those with OSA-COPD overlap have a higher likelihood of respiratory failure/prolonged mechanical ventilation, regardless of obesity status. Furthermore, OSA-COPD is associated with a higher risk of AKI among obese patients or patients older than 60 years. Nevertheless, OSA-COPD appears to not be associated with a greater risk of postoperative AF or pneumonia than COPD alone. Unexpectedly, in-hospital mortality risk appears lower in patients with OSA-COPD overlap than COPD alone after CABG.

While PCI is a commonly performed procedure, CABG has been performed for more than 50 years and is preferred over PCI in patients with very severe atherosclerosis [4]. Patients who require CABG commonly have comorbidities that can increase the risk of surgery, and 2 comorbidities commonly seen in patients who require CABG are COPD and OSA [4]. Both COPD and OSA are associated with a decreased oxygen saturation, and in OSA-COPD overlap the decrease can be greater than in either condition alone, resulting in increased morbidity and mortality [11, 17, 20].

COPD is a chronic lung disease associated with decreased oxygenation that can be progressive, and debilitating [7, 9, 20]. Patients with COPD who require cardiac surgery, including CABG, are at increased risk of complications. A study comparing the outcomes of cardiac surgery in patients with COPD and those without COPD reported that patients with COPD required a longer intubation time, longer ICU stay, and longer LOS in the hospital [16]. Patients with COPD also had a higher risk of postoperative bronchoconstriction, respiratory failure, and AF. The mortality rate within 30 days after surgery was also higher in patients with COPD than those without. A meta-analysis of patients with COPD undergoing CABG found that COPD was associated with higher risks of postoperative pneumonia, respiratory failure, stroke, renal failure, and wound infection [15].

Like COPD, OSA is a chronic condition that is characterized by complete or partial obstruction of airflow during sleep [10, 20]. Typical symptoms of OSA are daytime sleepiness and fatigue; however, persons with OSA are at increased risk of heart failure, arrhythmias, and coronary artery disease [10]. While it is difficult to estimate the overall prevalence of OSA-COPD overlap syndrome, it is believed than more than 10% of adults have COPD and 9 to 38% of adults have OSA, and OSA is typically associated with male sex, obesity, and advanced age [12]. In addition, it is believed that COPD can increase the risk of developing OSA, and OSA increases the risk of acute exacerbations of COPD [12]. Patients with OSA-COPD overlap have more severe respiratory symptoms, worse quality of life, a higher rate of hospitalizations, and higher mortality than persons with either condition alone [12, 21]. Additionally, patients with OSA-COPD overlap have a higher prevalence of hypertension and diabetes than those with COPD alone [21, 22]. Risk factors for OSA in patients with COPD include high BMI, neck circumference, and CCI score [21]. Interestingly, the risk of OSA was found to be lower in patients with severe COPD than those with mild or moderate COPD [21]. Recent studies have reported OSA-COPD overlap syndrome is associated with increased cardiovascular risk, including hypertension, pulmonary hypertension, heart failure, ischemic heart disease, and cerebrovascular disease [23‐25].

In the present study, we found that patients with OSA-COPD overlap had increased risks of various inpatient outcomes, which is generally consistent with the previous literature. However, we unexpectedly found that patients with OSA-COPD overlap had a lower risk of in-hospital mortality than those with COPD alone. While seemingly paradoxical, a number of studies in the literature have documented similar phenomena. Raymonde et al. also reported that in patients with pneumonia who were on mechanical ventilation, OSA was linked to increased non-routine discharges but lower in-hospital mortality [26]. Another study highlighted that while OSA leads to a higher comorbidity burden and slightly increased complication rates in patients undergoing spinal fusions, it does not independently predict inpatient mortality [27]. Yet another research using the same NIS dataset suggested that OSA is associated with a reduced in-hospital mortality among non-surgical patients [28]. The authors stated that the unexpected result may arise from the failure to identify patients with undiagnosed OSA. Other potential explanations may be: Patients with OSA may receive more comprehensive respiratory management, including the use of CPAP, thereby lessening the hypoxemia often seen in COPD. This might also, in turn, reduce pulmonary hypertension, and decrease the workload on the heart, and mitigate some of the adverse effects of COPD on the cardiovascular system, potentially reducing the risk of life-threatening events. Also, patients diagnosed with both OSA and COPD might undergo more rigorous and frequent medical surveillance than those with COPD alone. This can lead to earlier detection and treatment of potential complications, thereby reducing the risk of mortality. It’s important to note that while these factors might help explain the observed protective effect of OSA-COPD overlap on in-hospital mortality, it should be subject to ongoing verification through future research. Lastly, although already considered in our analysis, the use of CPAP might be largely underestimated when relying on admission claim codes, leading to a potential bias.

Notably, our findings indicate that both hospital bed number and location significantly impact in-hospital outcomes, with smaller bed numbers associated with higher mortality and rural hospitals showing lower risk or respiratory failure compared to urban-teaching hospitals, as detailed in Supplementary Table S3. Hospitals with fewer beds often have lower patient volumes, potentially influence the surgical experience and quality of care. Urban and teaching hospitals, dealing with complex cases and specializing in certain treatments, might show higher respiratory failure rates due to the nature of their patient demographics and the complexity of cases they handle.

Despite expectations of higher costs due to the poorer outcomes associated with OSA-COPD overlap syndrome, our study discovered that total hospital costs did not significantly differ from those for COPD alone. This can be attributed to the overlap in treatment pathways and healthcare resource utilization for both conditions, including the use of non-invasive ventilation techniques common to their management. Consequently, the presence of OSA-COPD overlap does not substantially increase healthcare costs beyond the treatment expenses for COPD alone.

Though our results did not find any excessive risks of OSA-COPD on the occurrence of AF compared to COPD alone, other studies have reported relations between COPD, OSA, and heart surgery. AF is the most common atrial arrhythmia after CABG, with a prevalence of 15 to 45%, and is associated with a poor long-term prognosis [29]. A study of postoperative AF in patients with OSA who underwent CABG reported that all categories of OSA were significantly associated with postoperative AF, with the greatest association for severe OSA (OR = 6.82) [30]. It is estimated that about 24% of patients with AF also have COPD [31]. It is also believed that COPD promotes the progression of AF, increases the recurrence of AF after cardioversion, and reduces the effectiveness of AF treatment [31]. A recent meta-analysis reported that about 13% of patients with AF also have COPD, and the presence of COPD is associated with overall worse outcomes and a 2-fold increased risk of all-cause death, cardiovascular death, and major bleeding [32].