Box plots showing the distribution of baseline brachial artery flow-mediated dilation (FMD) and nitroglycerine-mediated dilation (NMD). Box plots showing the distribution of baseline brachial artery flow-mediated dilation (FMD) and nitroglycerine-mediated dilation (NMD). Responders to cardiac resynchronisation therapy (CRT) demonstrated impaired endothelial function at baseline that was significantly lower than baseline in non-responders. David R Warriner et al. Open Heart 2016;3:e000391 ©2016 by British Cardiovascular Society