Ascending Aorta – when and how it should be treated
Parietal tension is a physical quantity acting on the wall of a vessel (not just blood vessel, but any vessel, including another hollow organ such as the stomach or intestine) and which depends, according to Laplace’s Law, of three parameters: the pressure inside the vessel, the thickness of the vessel wall and the vessel diameter. Parietal tension of the aortic wall is thus determined by the pressure of the blood in the aorta (the “system tension”), the thickness of the aortic wall and the diameter of the aorta.
Increased aortic diameter will result in increased parietal tension. Thus, as the diameter of the aorta increases it will increase its rate of growth.
Overgrowth has two major consequences: rupture of the aorta and appearance of aortic insufficiency.
Rupture of aortic wall is a dramatic phenomenon that can cause rapid death of the patient, in the absence of urgent and large-scale intervention – the results of which are much lower than of a planned elective intervention. It is important to note that most patients with aneurysms of the ascending aorta not treated surgically die after these aneurysms rupture.
It should be noted that a dilated aorta should be replaced before of its rupture. We know today that spontaneous rupture (non-traumatic) of the aorta is exceptional at a size below a certain threshold. This threshold is different for different categories of patients. Thus, in patients with connective tissue disease (Marfan syndrome and other related syndromes, bicuspid aortic), aorta tends to rupture earlier (smaller size). Consequently, in these patients the indication for replacement of the dilated ascending aorta is recommended earlier.
In general, the reference aortic diameter is 5 cm. In younger patients and especially those with connective tissue diseases (Marfan syndrome) is recommended to replace the ascending aorta at a diameter of 4.3-4.5 cm. Also, is recommended prophylactic replacement of the ascending aorta at sizes smaller than 5 cm (4-4.5 cm in patients with bicuspid aortic and 4.8 cm at other patients) during cardiac surgery for another injury.
In conclusion, an enlarged ascending aorta should be monitored regularly by ultrasound. Since rupture is exceptional, usually at sizes smaller than 5 cm, it is recommended that these patients to address a heart surgeon only in special cases (younger patients, Marfan syndrome or other related syndromes, chronic aortic dissection). Due to the considerably risk of rupture at larger sizes (average size at which the ascending aorta ruptures is 5.9 cm) is recommended surgical replacement of the ascending aorta aneurysms larger than 5-5.5 cm.