Introduction: Ultrasound-facilitated, catheter-directed fibrinolysis improves right ventricular (RV) function in patients with acute pulmonary embolism (PE). Resolution of central pulmonary arterial thrombotic obstruction has been hypothesized as the principal mechanism for RV recovery.
Hypothesis: We postulated that improved peripheral blood flow rather than central blood flow correlates with reversal of RV enlargement due to PE.
Methods: Using a 3-dimensional quantitative reconstruction technique that allows resolution of the distal pulmonary arteries, we analyzed the computed tomographic (CT) pulmonary angiograms of 60 submassive and massive PE patients treated with ultrasound-facilitated, catheter-directed, low-dose fibrinolysis. We correlated the change in blood volume of the pulmonary arteries (<10 mm2 vs. >40 mm2 cross sectional area) from baseline to 48 ± 6 hours with change in CT-measured RV volume.
Results: Forty-five patients demonstrated reduction in RV volume (mean change was -31 ml). Increase in total lung blood volume/lung volume correlated with decreased RV volume/lung volume (R2 = 0.26). RV volume-to-left ventricular volume ratio decreased by 26% (Figure, Panel A). Decreased RV volume correlated with increased blood volume through <10 mm2 pulmonary arteries (R2 = 0.28) but not larger pulmonary arteries (> 40 mm2) (R2 = 0.00003) (Figure, Panel B1 and B2).
Conclusion: Total lung blood volume increases following ultrasound-facilitated, catheter-directed fibrinolysis. Increased blood volume through the peripheral, but not central, pulmonary artery vasculature correlates with reduction in RV volume after ultrasound-facilitated catheter-directed fibrinolysis.