Filling defects across the pulmonary arterial tree — location, burden, and clinical severity
Iodinated contrast timed to peak pulmonary arterial opacification for clot detection.
Region of interest placed in main PA; scan triggers automatically.
Thin collimation resolves vessels down to subsegmental caliber.
Radiologists trace central to peripheral branches in order.
Each branch checked for contrast cutoff or filling defect.
Central clots straddle the trunk or main branches, often causing severe compromise.
Large defects abruptly cut flow to both lungs downstream.
Right ventricle strain and shock can follow quickly.
Bright contrast surrounds a dark, low-attenuation filling void.
Distal branches often appear dim from reduced flow.
Central saddle emboli are a classic indication for aggressive, urgent intervention.
Lobar and segmental branches show smaller, more localized filling defects.
Lobar and segmental vessels feed a limited lung territory.
Occlusion here rarely destabilizes the whole right heart.
Standard anticoagulation is typically sufficient at this level.
Size and symptom burden still guide final decisions.
Subsegmental clots are small, harder to see, and debated clinically.
Tiny vessel caliber and motion artifact obscure small defects.
False positives and missed calls both occur here.
Isolated subsegmental clots may not always need treatment.
Risk factors and symptoms weigh heavily on the choice.
Isolated subsegmental PE remains one of the more debated calls in emergency imaging.
Location on the arterial tree correlates with severity and urgency of care.
Central, high-burden clots push toward aggressive management fast.
Small distal clots often allow a measured approach.
Location plus burden plus patient status guides final urgency.
CTPA remains the reference standard for this decision.
Anatomic level of clot burden is a core driver of pulmonary embolism triage.