Would a computed tomography (CT) scan be helpful in a patient with worsening shortness of breath (SOB) and known severe pulmonary arterial hypertension (PAH) on echocardiogram, with concern for bilateral pneumonia?

From the Guidelines

A CT scan would be helpful in this case of worsening shortness of breath with known severe pulmonary arterial hypertension and chest X-ray findings concerning for bilateral pneumonia. I recommend proceeding with a CT pulmonary angiogram (CTPA), which can provide detailed information about both the lung parenchyma and pulmonary vasculature, as suggested by the most recent guidelines 1. This would help confirm the pneumonia diagnosis, assess its extent, and evaluate for potential complications like empyema or lung abscess. Additionally, the CTPA can better characterize the pulmonary arterial hypertension, potentially identifying underlying causes such as chronic thromboembolic disease, interstitial lung disease, or vascular abnormalities that may be contributing to the worsening symptoms, as discussed in the 2022 update of the ACR Appropriateness Criteria for suspected pulmonary hypertension 1. The CT findings would guide appropriate management, which might include antibiotics for pneumonia (typically a respiratory fluoroquinolone like levofloxacin 750mg daily for 5-7 days or ceftriaxone 1-2g daily plus azithromycin 500mg daily for 3-5 days), optimization of pulmonary hypertension therapy, and potentially oxygen supplementation based on saturation levels. The benefit of obtaining this additional imaging outweighs the radiation exposure risk given the clinical scenario of deteriorating respiratory status in a patient with significant underlying pulmonary vascular disease, as supported by the European Respiratory Journal guidelines from 2015 1.

Some key points to consider when interpreting the CT scan include:

• A main pulmonary artery diameter of 29 mm has been shown to be 87% sensitive and 89% specific for pulmonary hypertension, with a positive predictive value of 97% 1
• The ratio of the main pulmonary artery to the adjacent ascending aorta is an extremely sensitive CT finding for pulmonary hypertension, with a positive predictive value of 96% 1
• Other findings suggestive of pulmonary hypertension on CT include a ratio of segmental pulmonary artery to accompanying bronchus >1:1, mosaic attenuation of the lungs, and enlargement of the right ventricle 1
• High-resolution CT can provide detailed views of the lung parenchyma and facilitate the diagnosis of interstitial lung disease and emphysema, as well as pulmonary capillary hemangiomatosis and pulmonary veno-occlusive disease 1

Overall, the use of CT scanning in this clinical scenario is supported by the most recent and highest quality evidence, and can provide valuable information to guide management and improve patient outcomes.

From the Research

Diagnostic Considerations for Worsening Shortness of Breath

• A patient with known severe pulmonary arterial hypertension (PAH) on echocardiogram presenting with worsening shortness of breath (SOB) and concern for bilateral pneumonia may benefit from a computed tomography (CT) scan to evaluate for potential causes of their symptoms 2, 3.
• CT angiography of the chest can help identify severe emphysematous changes, large bullae, and other abnormalities that may be contributing to the patient's symptoms 2.
• Additionally, CT scans can help diagnose alternative conditions such as pulmonary atelectasis, which can present with similar symptoms to pulmonary embolism (PE) and can be a frequent alternative diagnosis in patients undergoing CT-PA for suspected PE 3.

Role of CT Scan in Diagnosing Pulmonary Embolism

• CT pulmonary angiography is a standard diagnostic tool for evaluating patients with suspected pulmonary embolism, and can help identify partial and complete intraluminal filling defects, as well as other signs of PE 4.
• However, factors such as patient-related, technical, anatomic, or pathologic issues can cause misdiagnosis of pulmonary embolism, and the radiologist needs to determine the quality of the CT pulmonary angiographic study and whether PE is present 4.
• Breathing techniques during CT scan acquisition can also impact the diagnostic accuracy, with shallow breathing potentially improving image quality in patients with insufficient contrast enhancement during breath-hold examinations 5.

Considerations for Patients with Severe PAH

• Patients with severe PAH may have unique diagnostic challenges, and a comprehensive evaluation including CT scans and echocardiograms may be necessary to identify the underlying cause of their symptoms 2, 6.
• Concomitant conditions such as coronary disease may also need to be considered, and surgical management may be necessary in some cases 6.