RT Journal Article SR Electronic T1 54 Measures of Endothelial Dysfunction Predict Response to Cardiac Resynchronisation Therapy JF Heart JO Heart FD BMJ Publishing Group Ltd and British Cardiovascular Society SP A39 OP A39 DO 10.1136/heartjnl-2016-309890.54 VO 102 IS Suppl 6 A1 David Warriner A1 Ryan Crapper A1 Patricia Lawford A1 Paul Sheridan YR 2016 UL http://heart.bmj.com/content/102/Suppl_6/A39.1.abstract AB Background Cardiac resynchronisation therapy (CRT) improves morbidity and mortality in heart failure (HF). Impaired endothelial function, as measured by flow mediated dilation (FMD) is associated with increased morbidity and mortality in heart failure (HF) and may help to differentiate responders from non-responders.Methods FMD was measured at baseline and 12 months following CRT. The patient group were 94% male, mean age 69 ± 8 years, New York Heart Association (NYHA) functional class II-IV, QRSd 173 ± 21 ms and had a left ventricular ejection fraction (LVEF) 26 ± 8%.Results 70% of patients were found to have responded at 12 months. Responders had significant improvements in VO2 (12.6   ± 1.7 to 14.7 ± 1.5 ml/kg/min, p < 0.05), quality of life score (43 ± 23 to 24 ± 22, p < 0.01), left ventricular end diastolic volume (210 ± 125 ml to 173 ± 125 ml, p < 0.01), NT-proBNP (2422 ± 829 ml to 1732 ± 976 ml, p < 0.01 and 6 min walk distance (379 ± 117 m at baseline to 418 ± 105 m, p < 0.05). Baseline FMD in responders was 2.9 ± 1.9% and 7.4 ± 3.73% in non-responders (p < 0.05).Conclusions This confirms that FMD identifies response to CRT, due to endothelium dependent mechanisms alone.