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| The Surgical Technologist | AUGUST 2015 352 late unidirectional blood flow. The tricuspid valve allows deoxygenated blood to flow from the right atrium into the right ventricle. The deoxygenated blood will then flow from the right ventricle to the pulmonary artery through the pulmonary valve. At this point the blood will flow to the lungs to become oxygenated and back to the heart via the pulmonary veins (the only veins in the body that carry oxygenated blood), which will then empty into the left atrium. The mitral valve then opens to allow the oxy- genated blood to leave the left atrium and enter the left ventricle. The fourth and final valve within the heart is the aortic valve. The aortic valve sits between the left ventricle and the ascending aorta, the largest artery in the body. The ascending aorta is the starting point of the large network of arteries that carry oxygenated blood from the heart to the rest of the body and the veins that return deoxygen- ated blood back to the heart. The aorta consists of three portions: ascending (portion that arises from the left ven- tricle), arch (transverse portion that curves up and down into the left chest) and descending segment (includes tho- racic and abdominal portion). The abdominal portion of the aorta is where the aorta bifurcates into the common iliac arteries. The femoral arteries are a continuation of the external iliac arteries and are the main arteries of the lower limbs. AOR T I C VA LV E S T ENOS I S Aortic valve stenosis is a narrowing after the outflow tract from the left ventricle to the ascending aorta. The most common causes of this condition are rheumatic fever, birth defect and radiation therapy with the number one cause being age-related calcification. 1 When calcium deposits that flow through the blood stream begin to accu- mulate on the annulus and leaflets of the aortic valve, the leaflets become rigid and unable to open freely, resulting in stenosis. “Gradual, chronic obstruction to the left ventricular outflow creates an increasing pres- sure load on the left ventricle. The ventricle must work harder to generate a pressure high- er than the aortic pressure in order to propel blood through the narrowed orifice into the systemic circulation. The ventricle cannot compensate indefinitely. Although cardiac output can be maintained for a considerable period, left ventricular dilation occurs, which predisposes the heart to left sided failure and left atrial enlargement. If the ventricle is dilated and LV function is more significantly impaired, preoperative risk increases.” 2 Syncope, angina pectoris and dyspnea all can be symptoms of aortic valve stenosis. These symptoms are caused by insuf- ficient blood flow to the brain and the heart and to impaired left ventricular function. 3 Traditionally, a patient suffering from severe aortic stenosis would undergo open heart sur- gery to replace the calcified valve. T AV R A DVA N T AGE S There are several advantages to trans- catheter aortic valve replacement, the foremost being recovery time. Patients typically are discharged from the hos- pital within a few days of their pro- cedure. 4 TAVR procedures preclude the need for a sternotomy, which is necessary for traditional aortic valve replacement surgery. Also aiding in recovery time is the use of a small incision at the groin and a few small punctures where the sheaths are placed. This decreases the incidence of infection as well as pain. In most cases, there is no need to utilize the cardiopulmonary bypass machine, which puts less stress on the organs of the body. There are three main approaches currently being uti- lized for the TAVR procedures. Most commonly used is the transfemoral approach, where access is gained through the femoral artery. The transapical approach is when access is gained through the apex of the heart and is accomplished through a small left thoracotomy. The transaortic approach, is where access is gained by making a sideline mini-sternot- omy directly over the ascending aorta. Two less commonly known TAVR approach options are the carotid and subcla- vian routes, used for patients with unusual circumstances. Transcatheter aortic valve replacement procedures are typi- cally for patients who are considered non-operable through traditional sternotomy because of preexisting comorbidi- ties, which prevent them from being candidates, or for cases where open heart surgery has been deemed too risky.