The impact of obstructive sleep apnoea severity on cardiac structure and injury

Obstructive sleep apnoea (OSA) is an important factor in the development and progression of heart failure (HF). The prevalence of OSA is higher in patients with HF than in the general population. We sought to test the hypothesis that OSA severity was predictive of ventricular function and cardiac injury [as assessed by high-sensitivity cardiac troponin I(hs-cTnI)].

A total of 60 patients were recruited after evaluation for sleep disturbances using the Jenkins Sleep Questionnaire (JSQ) and Epworth Sleepiness Scale (ESS). Subsequently, they underwent polysomnography thus confirming the diagnosis of OSA and were equally divided into three groups according to OSA severity grade. Following polysomnography, the next morning patients underwent venous blood sampling and echocardiography.

We observed a statistically significant association (P = 0.009) between diastolic dysfunction grades and severity grades of OSA. All the three diastolic dysfunction variables E/A ratio, deceleration time and E/e' ratio had a significant association(P < 0.05) with severity grades of OSA. There was a marginally significant positive correlation (ρ = 0.3244, p = 0.04) between AHI events per hour and mitral E/e' ratio. There was a statistically significant association(P < 0.001) between hs-cTnI value among different severity grades of OSA.

Here in our study, we found OSA a potential risk factor for development of myocardial injury and diastolic dysfunction. Severe grades of OSA are associated with higher grades of diastolic dysfunction and circulating levels of hs-cTnI. These data are consistent with the notion of a vicious cycle of frequent apnoea's or hypoxemia and recurrent myocardial injury, which could increase the risk of heart failure especially diastolic dysfunction in OSA.