B-PO03-143 LOCALIZED PULMONARY VEIN STRESS INDUCED BY POSTURAL CHANGE IN HEALTHY HUMANS

Abstract

A change in body position can trigger cardiac arrhythmias. Increased stress of atrial myocardium is proarrhythmic. The effect of body position on localized atrial stress and strain is unknown. We sought to evaluate the effect of body position on localized stress and strain in the left atrium (LA) and pulmonary veins (PV). Functional cardiac magnetic resonance imaging was carried out in supine and left lateral (LL) body position in healthy human volunteers (n=20) that resembled patients with atrial fibrillation in terms of sex, age and BMI. We analyzed local LA strain with a feature-tracking algorithm. Following a change from supine to LL position, the heart moved in an anterior-LL direction in the thorax. Maximal LA volume was 17% larger in LL than supine position (61.7±15.4 (mean±SD) vs. 51.0 (17.8) (median (IQR)) ml, respectively, p=0.015). The diameter of the right superior pulmonary vein (RSPV) was larger in LL than in supine position (24.6±3.9 mm vs. 20.7±4.4mm, respectively, p=0.003). Two-dimensional (2D) strain during the cardiac cycle (defined as the vector summation of radial motion fraction and longitudinal strain) was lower in the RSPV posterior wall and higher in the right inferior PV posterior wall in LL than supine position (16.8±5.4 vs. 21.1±9.6 arbitrary unit (AU), p=0.048, and 19.7±7.9 vs. 14.6±6.9AU, p=0.023, LL vs. supine, respectively). Maximal longitudinal strain was lower in the LA posterior wall in LL compared to supine (43.4±22.5 vs. 49.1±32.5%, LL vs. supine, p=0.025). In contrast, the atrial septum deformed more in LL than in supine position (2D strain: 66.8±18.2 vs. 57.0±16.5AU, respectively, p=0.030). Body position change induced localized alterations in LA and PV stress and strain. These results imply that posture-triggered atrial arrhythmias may be caused by altered strain.