Objective To investigate the association between obstructive sleep apnoea (OSA) severity with markers of overnight myocardial injury in patients with refractory angina.

Methods Patients with refractory angina were characterised clinically and they underwent ischaemia imaging stress tests by single-photon emission computed tomography (SPECT) and/or cardiac MRI. The patients were admitted to the hospital, remained under resting conditions for blood determination of high-sensitivity cardiac troponin T (hs-cTnT) at 14:00, 22:00 and after overnight polysomnography at 7:00.

Results We studied 80 consecutive patients (age: 62±10 years; male: 66%; body mass index (BMI): 29.5±4 kg/m²) with well-established diagnosis of refractory angina. The mean apnoea–hypopnoea index (AHI) was 37±29 events/h and OSA (AHI >15 events/h) was present in 75% of the population. Morning detectable hs-cTnT and above 99th percentile was present in 88% and 36% of the population, respectively. Patients in the first to third quartiles of OSA severity did not have circadian variation of hs-cTnT. In contrast, patients in the fourth quartile (AHI ≥51 events/h) had a circadian variation of hs-cTnT with a morning peak of hs-cTnT that was two times higher than that in the remaining population (p=0.02). The highest quartile of OSA severity remained associated with the highest quartile of hs-cTnT (p=0.028) in multivariate analysis.

Conclusion Very severe OSA is common and independently associated with overnight myocardial injury in patients with refractory angina.