A 62-year-old woman on oral contraceptives presents with acute dyspnea and hemoptysis. CTPA is performed and shows a wedge-shaped area of consolidation in the right lower lobe with a central pulmonary artery cutoff sign. Which additional imaging finding on CTPA would best support the diagnosis of acute pulmonary embolism with infarction?

Explanation

## CTPA Findings in PE with Pulmonary Infarction **Key Point:** Pleural effusion adjacent to a wedge-shaped consolidation is a hallmark sign of pulmonary infarction secondary to PE. This finding, combined with the central pulmonary artery cutoff sign, strongly supports acute PE with tissue necrosis. ### Pathophysiology of Pulmonary Infarction 1. **Mechanism:** PE → obstruction of pulmonary artery → ischemia → hemorrhagic infarction 2. **Frequency:** Occurs in only 10% of PE cases (requires occlusion of distal vessels + compromised bronchial circulation) 3. **Location:** Typically peripheral, wedge-shaped, in lower lobes (gravity-dependent) 4. **Associated pleural effusion:** Results from hemorrhage into pleural space and inflammatory response ### CTPA Signs of PE with Infarction | Finding | Significance | Specificity | |---------|--------------|-------------| | **Wedge-shaped consolidation** | Hampton's hump; classic but rare (10% of PE) | High | | **Central pulmonary artery cutoff** | Direct visualization of embolus | Very high | | **Pleural effusion** | Hemorrhage from infarction; exudative | High when adjacent to wedge | | **RV/LV ratio > 0.9** | RV strain; indicates hemodynamic significance | Moderate; seen in 40% of PE | | **Atelectasis** | Non-specific; can occur with any lung process | Low | **Clinical Pearl:** Hampton's hump (wedge-shaped opacity with pleural effusion) is pathognomonic for pulmonary infarction but occurs in only 5–10% of PE cases. When present, it is highly specific for PE. ### Why Pleural Effusion is the Best Answer **High-Yield:** Pleural effusion adjacent to the wedge-shaped consolidation indicates: - Hemorrhage into the pleural space from infarcted lung tissue - Inflammatory exudate from tissue necrosis - Strong support for the diagnosis of PE with infarction (Hampton's hump) This finding, combined with the central pulmonary artery cutoff sign already described in the stem, creates a highly specific pattern for acute PE with pulmonary infarction. ### Mnemonic: WEDGE-PE **W** — Wedge-shaped opacity (peripheral, lower lobe) **E** — Effusion (pleural, adjacent) **D** — Distal vessel occlusion **G** — Gravity-dependent location **E** — Embolic source (DVT, right heart) **P** — Pulmonary infarction (rare but pathognomonic) **E** — Exudative fluid (hemorrhagic) ### RV Strain vs. Infarction **Key Point:** RV/LV ratio > 0.9 indicates RV strain from hemodynamic compromise but does NOT specifically indicate pulmonary infarction. RV strain can occur with massive PE without infarction. Pleural effusion adjacent to wedge-shaped consolidation is more specific for infarction.