Analysis of left ventricular systolic function by midwall mechanics in patients with obstructive sleep apnoea

Midwall mechanics reveal systolic dysfunction in obese and hypertensive patients with concentric left ventricular (LV) geometry, which is frequently detected in subjects with obstructive sleep apnoea (OSA). Midwall mechanics have never been studied in these patients, who frequently experience heart failure (HF).

We analysed midwall stress-shortening relations by echocardiography in 150 controls and 200 patients with OSA (age 62 ± 13 years) without known cardiac disease. On the basis of the severity of OSA, patients were divided into mild OSA (n = 63), moderate OSA (n = 70), and severe OSA (n = 67). LV stress-corrected midwall shortening (scMS) was considered low if <87% in men and <90% in women. scMS was similar in controls and mild OSA (90 ± 13 and 91 ± 18%, respectively) and significantly lower in moderate and severe OSA (83 ± 14 and 83 ± 15%; all P < 0.001 vs. controls and mild OSA). Prevalence of low scMS was 40 and 39% in controls and mild OSA (P=NS), 62% in moderate and 61% in severe OSA (both P < 0.001 vs. controls and mild OSA). In logistic regression analysis, low scMS was associated with moderate–severe OSA (OR 3.82, P < 0.001) independent of significant associations with diabetes (OR 5.06, P < 0.01), LV hypertrophy (OR 1.89, P = 0.01), and LV concentric geometry (OR 2.79, P < 0.001).

Midwall mechanics are impaired in more than half of middle-aged patients with OSA without known cardiac disease. Moderate–severe OSA predicts LV systolic dysfunction independent of diabetes, LV hypertrophy, and concentric geometry. These relations may in part explain the increased rate of HF and cardiovascular events in these patients.