Performance of the right ventricular outflow tract/aortic diameter as a novel predictor of risk in patients with acute pulmonary embolism.

Right ventricular (RV) enlargement, determined via the ratio of the right to left ventricular diameters (RV/LV) by CT imaging is used to classify the severity of acute pulmonary embolism (PE) and impacts treatment decisions. The RV/LV ratio may be an unreliable marker of RV dysfunction, due in part to the complex RV geometry. This study compared the RV/LV ratio to a novel metric, the ratio of the right ventricular to aortic outflow tract diameters (RVOT/Ao) in patients with acute PE treated with catheter-directed therapies (CDT). RVOT/Ao and RV/LV ratios were measured on CT images from 103 patients who received CDT for acute submassive or massive PE and were compared to RV dysfunction severity determined by transthoracic echocardiography. Ratios and biomarkers on admission were assessed for correlation with invasively-measured hemodynamics [right atrial (RA) pressure, mean pulmonary artery (PA) pressure, cardiac output (CO)]. RVOT/Ao but not RV/LV ratios were increased in patients with moderate or severe RV dysfunction compared to those without RV dysfunction (p < 0.05). Neither ratio showed significant correlation with RA (r = 0.09 vs 0.055, p > 0.05), mean PA pressure (r = 0.167 vs 0.146, p > 0.05), or CO (r = 0.021 vs - 0.183, p > 0.05). proBNP correlated with mean PA pressure (r = 0.377, p < 0.05). The RVOT/Ao ratio may be better at assessing RV dysfunction than the RV/LV ratio in patients presenting with acute PE. Although currently accepted protocols rely on the RV/LV ratio in determining when CDT are of benefit, the RVOT/Ao ratio may be a more useful tool in identifying high risk patients.