1068 Prediction of pulmonary vascular resistance in patients with a left to right shunt by cardiac MRI
© Bell et al; licensee BioMed Central Ltd. 2008
Published: 22 October 2008
Late presentation of a large left to right shunt or the presence of significant respiratory co-morbidity may be associated with the development of pulmonary vascular disease. In this situation, invasive assessment of the pulmonary vascular resistance (PVR) is required in order to determine operability. Phase contrast MRI (PC-MRI) allows for the non-invasive assessment of arterial flow and left to right shunt. When combined with simultaneous cardiac catheterization it is possible to accurately determine the PVR.
The PVR of patients with a large congenital defect can be predicted based on the magnitude of the left to right shunt assessed by PC-MRI.
All patients referred for MRI catheter assessment of the PVR with a large congenital defect that would result in a left to right shunt were eligible for inclusion. Exclusion criteria were pulmonary artery flow restriction in the form of a pulmonary artery band or bilateral branch pulmonary artery stenosis. MRI Cardiac Catheter was performed in a combined XMR suite with a 1.5 T Philips Intera Achieva Scanner and a single plane X-Ray unit. All studies were undertaken under general anaesthesia with ventilation to normocarbia. Invasive pressure measurements were obtained simultaneously with PC-MRI flows.
Pulmonary vascular resistance can be expressed as either an absolute value indexed to body surface area or as a resistance ratio. We have demonstrated that under general anaesthesia, the indexed PVR and the resistance ratio correlate strongly, implying that both are a valid measure of pulmonary vascular resistance in this setting.
There is a significant exponential relationship between the PVR and the net shunt which can be calculated by PC-MRI. In future, this model may be applied to patients with a large shunt to predict the PVR and possibly avoid the need for invasive catheter assessment prior to surgery.
This article is published under license to BioMed Central Ltd.