An Unusual Cause of Severe Pulmonary Hypertension: Compression of Pulmonary Arteries by Aortic Aneurysm and Thrombus Formation.

Pulmonary hypertension (PHTN) has a broad differential, ranging from common aetiologies like thromboembolism, chronic lung disease, and heart failure. External compression of the pulmonary arteries by thoracic aortic aneurysms (TAAs) is an exceptionally rare cause of PH but may significantly impact haemodynamics. We report the case of an 81-year-old woman presenting with progressive dyspnoea and peripheral oedema, who was found to have near-complete compression of the right main pulmonary artery (RMPA) by an ascending aortic aneurysm, along with intraluminal thrombus. Transthoracic echocardiography revealed severe PH with preserved left ventricular (LV) function. CT pulmonary angiography was carried out, confirming both mechanical compression of RMPA and thrombus formation. According to the existing literature, we proposed that compression-induced stasis likely contributed to thrombosis, aligning with Virchow's triad. Given the patient's frailty and comorbidities, she was managed conservatively. The multifactorial nature of this case prompts us to consider broader differentials in unexplained PH. It also acknowledges the challenges in managing larger symptomatic aneurysms in the elderly population.