PE Classification
| Category | Definition | Mortality |
|---|---|---|
| Massive | Sustained hypotension (<90 mmHg) >15 min OR requiring vasopressors | 25–65% |
| Submassive | SBP >90 mmHg + RV strain (CT / echo / ECG / troponin / BNP) | ~3% |
| Low risk | None of the above | <1% |
Massive PE requires immediate escalation — systemic thrombolytics or catheter-directed therapy. Submassive PE with worsening hemodynamics may also require escalation.
RV Strain on CT
RV strain can be identified on standard CTA chest:
- RV:LV diameter ratio >1.0 on axial four-chamber view (at level of mitral and tricuspid valves)
- Interventricular septal bowing — D-sign; leftward deviation indicates elevated RV pressure
- Reflux of contrast into IVC and hepatic veins — indicates elevated right heart pressure
- Main pulmonary artery diameter >29 mm — suggests chronic or acute-on-chronic elevated PA pressure
RV:LV ratio threshold varies by reference (>0.9 vs >1.0). A ratio >1.0 on axial CT correlates strongly with adverse outcomes and should be explicitly reported.
CT Findings of PE
| Finding | Description |
|---|---|
| Filling defect | Intraluminal low-density area within contrast-opacified pulmonary artery |
| Saddle embolus | Clot straddling the main pulmonary artery bifurcation |
| Pulmonary infarct | Peripheral wedge-shaped opacity (Hampton's hump) abutting pleura; may be truncated cone |
| Oligemia (Westermark sign) | Focal hypoperfused lung distal to occlusion on CXR |
| Mosaic attenuation | Heterogeneous lung density from regional differences in blood flow |
Reporting Checklist — Pulmonary Embolism
- Clot location: saddle / main PA / lobar / segmental / subsegmental — list affected vessels
- Bilateral vs unilateral involvement
- RV/LV diameter ratio on axial CT (>1.0 = RV strain); note method
- Interventricular septal bowing: D-sign present / absent; direction
- Reflux of contrast into IVC/hepatic veins: present / absent
- Main pulmonary artery diameter (normal <29 mm)
- Pulmonary infarct: present / absent; location; size
- Pleural effusion: present / absent; laterality; size
- Classification: massive / submassive / low-risk based on imaging findings
Reference
Sista AK et al. Stratification, Imaging, and Management of Acute Massive and Submassive PE. Radiology. 2017;284(1):5–24.