The aorta and its major branches distribute the blood which is pumped out of the heart with each beat and circulates around the body before returning to the heart via the veins. These are large vessels and become diseased either through genetic defects of collagen or elastin fibres in the wall of these vessels or as a result of other disease processes like high blood pressure or cholesterol, diabetes, sleep apnoea and smoking.
The pressure stress on these vessels occurs with every heartbeat. Even at rest, 80mls of blood is ejected from the left ventricle in a fraction of a second at high pressure into the aorta. This pressure wave travels down the circulation and is reflected back from the smaller branches imposing an additional stress on the aorta and its major branches. This peak pressure (systolic BP) falls to a lower level before the next heart beat (diastolic BP).
Diseases affecting the aorta
Disease of the aorta can be undetected as the aorta usually enlarges gradually. Like any other elastic tube there will reach a point when the artery thins and ruptures, either into the wall of the artery (‘dissection’) or through the wall. This is extremely sudden and painful – classically described as “tearing’ – and often fatal unless recognised promptly and treated in a hospital.
Prevention is the key by early detection and surveillance. Genetic susceptibility to aortic disease is common – examples include Marfan syndrome and Familial Thoracic Aneurysms and Dissection or TAAD, Loeys-Dietz syndrome and Ehlers-Danlos syndrome. Screening high risk family members is critically important.
Symptoms of aortic disease
Aortic dissection of the first section of the aorta – the ascending aorta and arch or type A – typically causes severe pain in the front of the chest. It can be confused with a heart attack. Unless the diagnosis of aortic dissection is considered possible, it may be missed with a serious outcome. The treatment of aortic dissection is quite different to heart attack. Treatment of suspected heart attack with thrombolytic or “clot buster” drugs is standard practice but a harmful treatment in dissection.
Dissection of the descending aorta – Type B – which lies in the back of the chest and abdomen typically causes “tearing’ or ‘ripping’ felt between the shoulder blades and back. Dissection of the descending aorta can damage a series of aortic branches including those to the spine (causing paraplegia), kidneys and gut.
The aorta can dissect along its entire length so patients may experience either of these events, simultaneously or sequentially.
Treatment of Aortic Dissection
Treatment of aortic dissection depends on where it is but for those which involve the ascending aorta, surgery is the best treatment option. A descending aortic dissection is usually best treated with stenting or medications.
The ascending aorta and arch are shown on the left and the CT scan shows the stent placed at the beginning of the descending aorta just beyond the origin of the left subclavian artery.