Final answer:
A specific sign of dilatation of the collateral chest wall vessels due to coarctation of the aorta is observable pulsations or rib notching on chest X-ray, which results from the development of intercostal artery collaterals.
Step-by-step explanation:
Coarctation of the aorta is a congenital condition involving a narrowing of the aorta. This abnormality can result in several compensatory changes within the body, as it attempts to maintain adequate blood flow despite the obstruction. One clear sign of this condition's impact on the circulation is the dilatation of collateral chest wall vessels. These vessel changes occur as blood flow is rerouted through smaller, secondary vessels to bypass the obstruction and deliver blood to the lower part of the body. Over time, these vessels can become more prominent and visible on the chest wall.
A particular physical sign associated with the dilatation of collateral chest wall vessels due to coarctation of the aorta is the development of intercostal artery collaterals, which may result in observable pulsations or rib notching on chest X-ray. Additionally, palpable collateral vessels may sometimes be felt around the scapulae or along the sides of the thorax in affected individuals.