The potential of clinical prediction model development from a change in cardiac repolarization and pulse oximetry data in patients with undiagnosed obstructive sleep apnea undergoing coronary artery bypass grafting

INTRODUCTION

In the current issue of the Journal of Clinical Sleep Medicine, the paper by Teo et al studies the impact of obstructive sleep apnea (OSA) and temporal changes in cardiac repolarization in patients undergoing coronary artery bypass grafting (CABG).¹ In order to help the readers understand the importance of this paper, this commentary is divided into three sections: (1) the importance of OSA detection in patients undergoing CABG, (2) the significance of the Teo et al paper, and (3) future implications of the Teo et al paper.

OSA AND CABG

OSA is a prevalent condition, and approximately 1 billion people experience at least mild OSA.² A recent meta-analysis showed a worldwide combined prevalence of OSA of approximately 54%.³ OSA is prevalent in cardiac patients, ranging from 40% to 80%.^4,5 Patients with OSA tend to have early atherosclerosis,⁶ increased arterial wall stiffness,⁷ coronary plaque instability,⁸ and coronary artery calcification.⁹ Another study reported moderate to severe OSA as an independent risk factor for increased severity of coronary artery disease.¹⁰

OSA is common in patients undergoing CABG, and if it remains untreated, it is associated with adverse outcomes.^11–13 OSA is associated with prolonged QTc interval and abnormal cardiac repolarization.^11,12 Increased QTc interval and untreated OSA are risk factors for major adverse cardiovascular and cerebrovascular events (MACCE).^13,14 Another study that followed patients 4 years after myocardial infarction reported nocturnal hypoxemia as an independent predictor of MACCE.⁷

SIGNIFICANCE OF THE TEO ET AL PAPER

Teo and colleagues studied the relationship between OSA, abnormal cardiac repolarization, and the future occurrence of MACCE in patients undergoing CABG. They conducted a prospective cohort study that included 1,007 patients and finally included 954 patients for analysis. They included patients aged 18–90 years (median age 62 years) who were scheduled to have elective CABG surgery. They excluded patients who received continuous positive airway pressure (CPAP), mechanical ventilation, oxygen, or other treatment for OSA. They also excluded those who had heart failure exacerbation or needed an intra-aortic balloon pump for shock. The patients underwent an overnight sleep study prior to CABG. They only considered moderate to severe OSA with an apnea-hypopnea index of 15 events or more per hour to better compare with previous cardiovascular studies.^15,16 The patients also had an electrocardiogram (ECG) within 48 hours before the CABG and within 24 hours after the CABG to assess change in cardiac repolarization through QTc. Approximately 115 patients developed MACCE during a 2.1-year follow-up period. Teo et al performed Cox regression analysis and found that a higher preoperative oxygen desaturation index (ODI) was an independent predictor of a smaller change QTc. A smaller change in QTc was an independent risk factor for MACCE. This study highlights the importance of OSA detection in patients undergoing elective CABG surgery and certain tools to predict clinical outcomes.

FUTURE IMPLICATIONS OF THE TEO ET AL PAPER

Obstructive sleep apnea is prevalent in patients with coronary artery disease, and proper evaluation and management of OSA may reduce MACCE.¹⁷ With the advancements in wearable technology, an automated heart rate–based algorithm can accurately identify sleep staging just from ECG monitoring.¹⁸ Polymer sensor embedded and Internet of Things (IoT) enabled t-shirts have many sensors to collect multiple cardiopulmonary physiological data, and they can help diagnose and monitor OSA, which can be utilized in the future using machine learning and artificial intelligence.¹⁹

Teo et al’s study brings great insight into improving the care of patients undergoing elective CABG. During routine workups prior to CABG, where a sleep study is not available, nocturnal pulse oximetry may be included. Nocturnal pulse oximetry can provide the ODI and duration of hypoxemia below 90%. The ECG is already a routine procedure. If ODI data, the duration of hypoxemia below 90% with QTc changes, and screening tools for OSA are combined, a clinical prediction model can be developed. This type of clinical prediction model can be integrated into electronic health records to alert clinicians about the risk of MACCE in those patients (Figure 1).

Figure 1. Potential clinical prediction model for patients with CABG to reduce MACCE.

CABG = coronary artery bypass grafting, desat = desaturation, ECG = electrocardiogram, EHR = electronic health record, MACCE = major adverse cardiac and cerebrovascular events, ODI = oxygen desaturation index, OSA = obstructive sleep apnea.

CONCLUSIONS

A change in QTc within 24 hours after CABG could be a novel predictor of MACCE. Further studies and validation of the research done by Teo et al are needed to develop a clinical prediction model, which can impact many lives. Collaboration is required between clinicians, researchers, engineers, institutions with large datasets, and regulators to achieve the great mission of improving patient care.

DISCLOSURE STATEMENT

The authors report no conflicts of interest.