Purpose: To evaluate variability in right ventricular-to-left ventricular (RV/LV) diameter ratios introduced by differences in measurement methods and the subsequent influence on the accuracy of predicting outcomes for patients with acute pulmonary embolism (PE).
Materials and methods: For 200 consecutive computed tomography pulmonary angiograms positive for acute PE, RV/LV diameter ratios were retrospectively measured using 3 different 4-chamber reformations and from axial images alone. The first 4-chamber reformation method (4ch-1) was a single oblique technique using LV morphology landmarks; the other 2 methods (4ch-2 and 4ch-3) were double oblique techniques that created an intermediate short-axis image to identify the maximum RV diameter but with different approaches to reach short-axis images. Interobserver variability was measured using 30 cases. Receiver-operating characteristic analysis compared the accuracy of predicting outcomes among the 4 measurements for PE-related death, and for death or the need for intensive therapies (composite outcome).
Results: The difference in median RV/LV diameter ratios was insignificant among 4ch-2 (1.01), 4ch-3 (1.02), and axial (1.03) datasets, whereas that from 4ch-1 (0.93) was significantly lower (P<0.001). Correlation between observers was excellent for all 4 datasets (r=0.881 to 0.925). Compared with 4ch-1, the other 3 datasets equally achieved higher accuracy in predicting PE-related 30-day mortality (area under curve: 0.55 vs. 0.69 to 0.73, P=0.007 to 0.019) and a composite outcome (area under curve: 0.65 vs. 0.77 to 0.78, P=0.003 to 0.010).
Conclusions: Double oblique 4-chamber reformation methods that use intermediate short-axis images to optimize RV size predict outcomes better in patients with acute PE than do single oblique methods using only LV landmarks; however, their accuracy is not superior to that from measurements based on axial images.