Introduction and Objectives Acute right ventricular (RV) failure is known to cause death in patients with pulmonary embolus due to circulatory collapse. CT pulmonary angiogram (CTPA) is now considered the gold standard test for the detection of pulmonary emboli, the technique provides excellent structural detail, however provides limited functional information. This aim of this was to assess time-resolved CTPA contrast transit times (TT) as a potential functional CT marker for the detection of right heart strain in patients with PE.
Methods We retrospectively reviewed consecutive patients who underwent CTPA at our institution over a 2-month period. Scans were performed on a Phillips Brilliance 16-slice scanner with a 4 ml/s OptirayTM 300 pressure injection. TT was defined as the time from the start of the injection to the scan trigger at the threshold of 150 hounsfield units measured from ROI analysis at the main pulmonary artery. Established CT structural imaging metrics were scored for comparison.
Results 56 consecutive patients were identified with evidence of pulmonary embolic disease or normal thoracic CT appearances from CTPA scans. One patient with PE was excluded as the CTPA scan was non-diagnostic. TT, RV septum to free wall distance, RV/LV ratio and PA diameter were all significantly elevated in patients with pulmonary embolus compared to patients with a normal CTPA. On analysis of bivariate correlation, TT had a statistically significant positive correlation with hepatic reflux, PA diameter and RV/LV ratio. Notably, the TT and RV/LV ratio demonstrated a significant direct linear correlation (p=0.001).
Conclusions This study supports previous evidence of existing markers, such as RV/LV ratio, being useful imaging marker in pulmonary embolic disease. It also suggests that TT, could be a new useful functional marker of right heart strain. The importance of further research into this field is highlighted, and particularly into TT as a haemodynamic prognostic indicator in acute pulmonary embolism.