October 2023
Congenital cardiovascular abnormality and dynamic airways collapse
October 2023
Dr Liam Peng, Dr Xinyi Qiu, Dr Emily Hughes, Dr Ryan Grech, Dr Gruschen Veldtman, Dr John Dreisbach
Case History:
A 65-year-old female with a history of asthma and chronic rhinosinusitis presented with wheezy cough and persistent exertional dyspnoea, having previously been reasonably fit and active during her childhood and earlier adult life. Spirometry showed an obstructive pattern, with partial improvement in FEV1 following bronchodilator therapy. Peak flow was, however, persistently low with a truncated expiratory flow volume loop. An initial HRCT with inspiratory and expiratory scans demonstrated a right aortic arch with narrowing of the trachea and right main bronchus. The patient was further investigated with a CT angiogram and 4D dynamic airways CT.
CT Angiogram:
A CT angiogram demonstrated a mirror-image right arch with a vascular ring completed by a left ligamentum arteriosum extending from a left-sided retroesophageal ductal diverticulum from the right-sided proximal descending aorta to the left pulmonary artery. Additionally, there was moderate dilation of the proximal descending aorta partly related to the ductal diverticulum.
CT angiogram. Mirror-image right arch with a left ligamentum arteriosum completing a vascular ring, as well as moderate dilation of the proximal descending aorta related to the ductal diverticulum.
4D Dynamic Airways CT:
A 16 cm volume CT covering the trachea and central bronchi was performed while the patient instructed to gently breath in and out during a continuous 4-second long acquisition with multiple phase reconstructions throughout the respiratory cycle (DLP 185.70 mGy.cm; effective dose 2.6 mSv).
The vascular ring, formed by the proximal descending aorta, right arch, brachiocephalic trunk, and left ligamentum arteriosum, resulted in mild resting narrowing of the mid trachea but only mild dynamic collapse (~40% decrease in cross-sectional area).
There was, however, also moderate resting narrowing of the right main bronchus, compressed between the dilated proximal descending aorta and right pulmonary artery, with severe dynamic collapse (~80% decrease in cross-sectional area).
4D dynamic airways CT of the mid trachea at the level of the vascular ring demonstrating mild dynamic collapse.
