Purpose: To determine whether the perfusion index (PI) can be used as a noninvasive measure to diagnose and predict the severity of disease in patients with pulmonary arterial hypertension (PAH).
Materials and methods: Twenty-two patients were included in this retrospective investigation: 9 controls and 13 patients with PAH. Controls had no evidence of PAH [mean pulmonary arterial pressure (MPAP) ≤25 mm Hg and pulmonary capillary wedge pressure ≤18 mm Hg]. The study patients had PAH (MPAP ≥25 mm Hg and pulmonary capillary wedge pressure ≤18 mm Hg) and no diagnosis of pulmonary embolism. Due to the retrospective nature of the study, the PI was calculated from the posterior perfusion image of a ventilation perfusion scan. The PI was computed as the sum of differences versus control for the 9 deciles above background. Receiver operating characteristic curve analysis was used to compare PI with other parameters for predicting PAH.
Results: Linear correlations of PI were found to be significant with the following parameters: pulmonary vascular resistance (r=0.81, P=0.00009), total pulmonary vascular resistance (MPAP/cardiac output) (r=0.80, P=0.00013), pulmonary artery systolic pressure (r=0.73, P=0.00018), MPAP (r=0.72, P=0.00022), pulmonary diastolic pressure (r=0.53, P=0.01), and right atrial pressure (r=0.50, P=0.03). Using logistic regression, the PI was significant in separating patients with PAH from controls (χ²=5.6, P=0.02).
Conclusion: The data suggest that PI can be used for the noninvasive diagnosis and measurement of severity of PAH.