75 The effects of atrial fibrillation on left ventricular mechanics and genomics in mitral regurgitation

BackgroundThe development of atrial fibrillation (AF) in mitral valve regurgitation (MR) adversely affects patient’s long term outcome despite successful surgical repair. The fundamental changes in LV myocardial mechanics and genomics in AF remains to be fully elucidated. The aim of this study was to elucidate LV mechanics and myocardial gene expression profiling in MR patients with AF.Material and methodsWe studied 28 consecutive patients (age 64±14 yr, 18 males) undergoing elective MV surgery for degenerative severe MR. Of whom 25 patients (12 AF vs 13 SR) underwent physiological study using transoesophageal echo, high fidelity LV pressures and Swan-Ganz pulmonary catheter for cardiac output before the cardiopulmonary bypass. Transverse LV cavity dimension and wall thickness were derived from mid-cavity M-mode echocardiograms along with LV pressure by digitising. Systolic wall stress, peak Vcf, thus myocardial power were determined. LV ejection fraction and MR fraction (MR volume/LVSV) were measured. Gene expression profiling by LV myocardium biopsy was studied in 11 patients using Stanford Human Exonic Evidence Based Oligonucleotide (HEEBO) array. Statistical analysis was performed between 5 AF and 6 SR cases using parametric permutative (permutation times=1000) t-test p-value cut-off 0.01. Gene functional annotation clusters were performed using Database for Annotation, Visualization and Integrated Discovery (DAVID, NIH, USA) and pathway analysed by GeneSpring GX10.ResultsThe AF group had a significantly greater MR fraction (70± 12 vs 47±11, %, p