A composite score of polygraphic oximetry parameters predicts left ventricular hypertrophy in patients with obstructive sleep apnoea.

BACKGROUND

Obstructive sleep apnoea (OSA) is linked to cardiovascular disease (CVD). The obstructive apnoea-hypopnoea index (oAHI) used for diagnosing and grading OSA has limitations in predicting CVD. The present study assessed and compared the association between nocturnal hypoxaemia parameters and left ventricular hypertrophy (LVH).

METHODS

A cross-sectional study was conducted on 187 consecutive adult outpatients diagnosed with OSA after home cardiorespiratory polygraphy. Blood pressure control was tested with ambulatory blood pressure monitoring. A standard transthoracic cardiac ultrasound examination assessed LVH. Oximetry parameters were grouped into a single parameter (Oxy-score) using factor analysis (a higher Oxy-score indicating better nocturnal oxygenation), which was tested for association with LVH.

RESULTS

The mean age was 60±12 years, with 75% male sex and 94% overweight/obese. The prevalence of arterial hypertension and LVH was 92% and 75%, respectively. The prevalence of severe OSA was 44%, with a mean oAHI of 32±19. Patients with LVH had significantly higher oAHI (34±19 versus 27±18; p=0.030), oxygen desaturation index (41±23 versus 30±18; p=0.004), and worse oximetry parameters. Oxy-score results were independently associated with LVH (adjusted OR 0.45; p=0.044). oAHI lost its independent relationship with LVH when the model included the Oxy-score. Receiver operating characteristic curves showed that oAHI was less accurate in predicting LVH than Oxy-score (area under the curve (AUC) 0.63, 95% CI 0.59-0.68 versus AUC 0.70, 95% CI 0.65-0.74, respectively; p=0.005).

CONCLUSION

Nocturnal oximetry parameters, grouped into a single parameter as a proxy of the global hypoxic burden, proved to be a better and independent predictor of LVH than oAHI, supporting the pivotal relevance of oximetry parameters beyond oAHI in patients with OSA.