Editors' ChoicePulmonary Arterial Hypertension

Estimation of Blood Flow Resistance in the Lung with MRI

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Science Translational Medicine  28 Aug 2013:
Vol. 5, Issue 200, pp. 200ec144
DOI: 10.1126/scitranslmed.3007308

In pulmonary arterial hypertension (PAH), vascular cells in the lung proliferate, leading to elevated pulmonary vascular resistance (PVR), failure of the right ventricle of the heart, and premature death. PVR is a useful measure that reflects the degree of pulmonary artery involvement and therefore the patient's prognosis. In addition, serial measurements of PVR allow monitoring of disease progression and response to therapies. PVR is usually calculated by dividing the transpulmonary gradient (mean pulmonary artery pressure minus right atrial pressure) by the cardiac output, parameters obtained during right heart catheterization. Despite the risk of complications from this invasive procedure, there are few safe alternatives.

Cardiac magnetic resonance (CMR) may be a good substitute. A well-established methodology for assessing right ventricular function noninvasively, CMR measures the average pulmonary artery flow, which is strongly associated with PVR. Now, García Álvarez et al. have taken this method one step further to show that CMR can accurately detect changes in PVR in Large White pigs with acute and chronic pulmonary hypertension. The hypertension was produced by injecting polydextrane microspheres either once or multiple times into the animals. Simultaneous hemodynamic and CMR assessments were regularly performed to calculate and estimate PVR, respectively. CMR estimations of PVR were based on pulmonary artery velocity and right ventricular ejection fraction. As chronic pulmonary hypertension developed or after pulmonary vasodilators were given to the pigs, changes in both the estimated PVR and a simpler measure (average pulmonary artery flow velocity) reflected variations in the PVR, which was obtained by right heart catheterization.

There is a persistent need to identify noninvasive methodologies that can better assess PAH severity. These new results indicate that CMR can estimate PVR both at a single time point and over time, a discovery that positions this methodology as a promising tool for the noninvasive monitoring of PAH patients and their response to therapy.

A. García-Álvarez et al., Noninvasive monitoring of serial changes in pulmonary vascular resistance and acute vasodilator testing using cardiac magnetic resonance. J. Am. Coll. Cardiol., published online 14 August 2013 (10.1016/j.jacc.2013.07.037). [Abstract ]

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