Acute Type B Aortic Dissection
I. Background
A Type B aortic dissection is when the intimal tear is present beyond the subclavian artery however it can be located in the aortic arch. The false channel propagates distally into the descending and abdominal aorta. If the false channel travels toward the ascending aorta this is classified as a Type A aortic dissection. The passage of blood through a channel in the aortic wall can lead to complications such as spinal cord injury (paraplegia), lack of blood supply to the intestines or lower extremities. The flow of blood in the false channel can cause these complications by pinching off flow of blood into the branches off the aorta.
II. Presentation
Overall, greater than 60-80% of patients with type B aortic dissection have an elevated blood pressure at presentation. Another predominant feature in patients with aortic dissections is the history of cigarette smoking. Approximately 30-40% of patients have a history of atherosclerosis. Ten to twenty percent of patients have history of a connective tissue disorders, prior cardiac or aortic surgery or aortic aneurysm. The most common presentation is severe, sharp, ripping, back pain. At times the pain may feel like it is extending into your chest and abdomen.
III. Treatment
Approximately 85% of patients can be treated conservatively with blood pressure and heart rate control. The treatment is called “anti-impulse” therapy. Basically, the therapy slows down the heart rate and blood pressure to reduce the shear stress on the aortic wall. Surgery or endovascular therapies are performed when there are complications from the aortic dissection such as rupture or lack of blood to various organs. If there is rapid expansion in the size of the aorta, surgery may be necessary.
IV. Follow-up
Patients require long-term follow-up to evaluate the rate of growth and size of the aorta. The weakened thoracic aorta secondary to the aortic dissection can develop into an aneurysm. Patients with a dissected aortic aneurysm of the descending thoracic aorta need potential surgery when the diameter reaches 5.5cm. In studies dedicated to investigating the natural history of thoracic aortic aneurysms, the patients with a chronic type B aortic dissection tended to have more aortic complications when the aortic diameter reached 6 cm.