Background A transpulmonary gradient (TPG)>12mmHg is thought to represent evidence of vascular change beyond that expected from passive pulmonary venous congestion in patients with pulmonary hypertension and left heart disease (PH-LHD). However recent studies found those with a diastolic pressure gradient (DPG) >6 to have a worse survival. This has led to a change in the recent guidelines suggesting 2 types of PH-LHD: “isolated post-capillary PH” (pulmonary arterial wedge pressure (PAWP)>15 mm Hg and DPG<7mmHg) and “combined postcapillary PH and pre-capillary PH” (PAWP>15 mm Hg and DPG≥7 mmHg). It would be advantageous if a non-invasive method of predicting DPG could be found for both prognostication and to identify potential patients for clinical trials of targeted therapies. Our aim was investigate the utility of cardiac magnetic resonance (CMR) imaging for estimation of DPG in patients with PH-LHD.