This study was conducted on 150 patients with an approved PE diagnosis to detect the CTPA indices indicating the PE with higher PESI. We found the obstruction index, the pulmonary trunk size, the presence of backwash contrast into IVC, and the abnormal septal morphology as predictive factors of higher PESI. We also investigated the dilated pulmonary trunk as the most effective predictor.
Among the signs included in the study, backwash contrast was significantly correlated with PESI. The result, in concordance with other studies, reported the presence of mentioned sign as a risk factor for mortality [11,12,13]. The backwash contrast into IVC is due to a right ventricular dysfunction that leads to tricuspid valve dysfunction, a decrease in forward flow from the right ventricle, and an increase of blood stasis in central veins. In addition to studies reflecting the presence of backwash contrast as a sign of RV dysfunction, some published articles have suggested this sign as an unreliable predictor [14, 15].
In this study, an abnormal septal morphology was significantly more common among patients with a high-risk PE. Interventricular septal morphology is caused by an increase of right ventricular pressure secondary to PE. It sometimes causes a leftward shift of interventricular septum that may lead to a decrease in left ventricular filling and a reduction of cardiac output, causing right ventricular wall ischemia, impaired heart function, and a poor prognosis for patients with PE .
In the present study, pulmonary trunk size was positively correlated with PESI. Patients with high-risk PE had significantly higher pulmonary trunk diameter. In this study, the value of 29 mm was established for the maximal value for normal pulmonary artery diameter. Also, we found that the dilated pulmonary artery had the highest OR = 4.4 in comparison with other predictors including abnormal septal morphology or the presence of backwash contrast. It suggests the idea that pulmonary trunk size can be used as a factor in prediction of patients with high-risk PE. The association between pulmonary artery diameter and short-term clinical outcomes was observed in a report of Lyhne et al. However, they did not report the pulmonary artery diameter as a strong predictor of PE outcomes .
There are many studies on the association between RV/LV ratio and PE outcomes. RV/LV ratio greater than 0.9 in the short axis was proposed as a sign of poor outcome and a higher 30-day risk of mortality [17,18,19]. However, there are some other studies reporting higher cutoff points including 1, 1.2, and 1.5 for the RV/LV ratio to be reported as an independent predictor of PE mortality [20,21,22]. Meinel et al. reported RV/LV diameter ratio as the strongest predictor of the clinical outcome of PTE . However, we did not find any association between RV/LV ratio and PESI, which is in accordance with the report of Lyhne et al. . The different results in different studies indicate that further studies are needed on this subject.
In addition to clinical symptoms and imaging features, there are many laboratory tools that are frequently utilized in patients with suspected PE, including arterial blood gas, brain natriuretic peptide, troponin, and D-dimer. These tests are not diagnostic, but they may have some prognostic values [24, 25]. In this study, we did not find any correlation between troponin, D-dimer level, and PESI. These results are in concordance with the report of Lerche et al., who stated that troponin level is not correlated to thrombotic obstruction and severity of PE . However, they found a correlation between D dimer and clot burden. Meanwhile, in the present study, D dimer was not correlated with CBS and the PESI.
Although this study identified CTA indices related to higher PESI in patients with stable hemodynamic, it cannot be generalized to all patients with PE. None of the participants in this study had a massive PE. Another study is needed to identify the predictive features of CTA in patients with hemodynamic instability.