A 56-year-old male is admitted to the intensive care unit (ICU) with a diagnosis of an acute descending thoracic aortic dissection. Which of the following echocardiographic findings is MOST helpful when distinguishing the true lumen from the false lumen?
A. The false lumen is usually smaller than the true lumenCorrect Answer: D
It is important to distinguish the true from the false lumen in an acute aortic dissection, especially when the dissection involves the ascending aorta, as there is a potential in compromising the patency of the coronaries and head and neck vessels, or distally, the visceral arteries as these may originate from the false lumen. Additionally, identification of the true lumen is critical to guide aortic wire placement during interventions. There are certain characteristics that help to identify the true lumen on echocardiography. In the descending aorta, the true lumen is usually smaller than the false lumen (A) and expands during systole (B). In the ascending aorta, the true lumen tends to be larger than the false lumen because proximal aortic pressures (closer to the left ventricle) are higher and thus keep the true lumen pressurized. The false lumen has a concave appearance compared to the convex appearance of the true lumen in systole. Echo findings of cobwebs (fibrinous remnants sheared from the intima during separation from media) are 100% specific for the false lumen in acute aortic dissection (C). Color-flow Doppler pattern is always inphase with the cardiac cycle as opposed to the out-of-phase pattern in the false lumen (D).
Echocardiographic features of true and false lumen are important to recognize compression of the true lumen, which may result in organ malperfusion to identify the origin of important aortic branches (if they originate from the true vs false lumen) and provide live guidance for cannula placement in the true lumen.
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