Friday, November 25, 2011

Aortic Regurgitation

Being the pumping station of the body, the heart pumps oxygenated blood throughout the body via aorta. A cardiac cycle is performed by the heart in the form of regular contractions and dilations in heart. A systole is characterized by the contraction of ventricles thereby pumping the blood into pulmonary artery and the aorta. A diastole, on the other hand, is characterized by the relaxing of ventricles during which the blood is received from the pulmonary vein and the vena cava. The pumping of blood is done from the left ventricle into the aorta all the way through the semi lunar valves. 

Aortic Regurgitation is the term used for an abnormal condition wherein the blood falls back into the ventricle during the process of dilation. The nostalgic blood flow through the aortic valve during a cardiac diastole can result in a clinical condition referred as Aortic Regurgitation. This clinical condition occurs primarily because of the aortic valve being unable to check the rearward blood flow. Any type of impairment in the valvular apparatus, such as leaflets, annulus of aorta is not able to check the pumped up blood from reverting back towards the left ventricle.

Valves are, basically, pathological conditions like Openings present in the heart. These valves open in one direction like trapdoors thus allowing the blood to pass through.whe these valves are closed, the blood cannot flow rearward into the atria. The aortic valve features three thin leaflets, also known as cusps, projecting from the wall of the proximal ascending aorta. Aortic Regurgitation might occur due to numerous reasons. These reasons might be congenital concerning the origin and the structure of an organ or acquired. The ventricular septal defect of the membrane, absence of 2-3 aortic valve leaflets, or dysplasia of valve cusps without the commissures’ fusion are anatomical abnormalities related to the valve structure or the ascending aorta which cannot prevent the blood from flowing backwards into the left ventricle. 

However, the valvular insufficiency need not essentially be present from birth but can also be acquired during the course of life. Different diseases associated with aortic regurgitation include:

Rheumatic fever
Systemic lupus erythematosus
Connective tissue syndrome like marfan syndrome, type IV, and turner syndrome
Prolonged and uncontrolled hypertension
Degenerative aortic valve diseases
Collagen vascular disease
Cystic medical necrosis
Senile aortic ectasia
Giant cell arteritis
Syphilitic aortic
Takayasu arteritis
Ankylosing spondylitis
Whipple disease

Data from researches reveals that the percentage of individuals suffering from aortic valve insufficiency resulting from aortic root disease has increased significantly as compared with the percentage of those with valvular disease. Besides, it has been recently recorded that more than 50% of patients with aortic regurgitation also have aortic valve insufficiency resulting from aortic root disease.

Aortic Regurgitation is characterized by sudden and severe breathlessness, fast developing heart failure, and chest pain if, in case, myocardial perfusion pressure is lessened or an aortic dissection is present. In case of severe AR, the patient might be required to undergo a long standing period, without symptoms. This standing period might last for several years. A decreased diastolic filling period can be created developing a compensatory tachycardia so as to maintain large volumes of forward stroke blood. Other symptoms linked with severe AR include forced heartbeats resulting in palpitations occurring from increase pulse pressure. Breathlessness might not become too serious due to presence of compensatory tachychardia in the primary stages. However, permanent chest pain and a sudden cardiac death, though, occur rarely.

There are numerous measures that can be adopted to treat aortic regurgitation. However, acute and severe cases might ask for surgical intervention. The patiens are administered with drugs like dobutamine, which are helpful in boosting the cardiac output and shortening the diastole, and sodium nitroprusside which helps to lessen the after load in hypertensive patients.

Another beneficial treatment is the vasodilator therapy. This therapy is helpful in lessening the after load of a patient with systolic hypertension in addition to bringing down the wall stress and raising the LV function. However, the vasodilator therapy is a long term t6ehrapy recommended to patients suffering from severe AR but cannot undergo a surgery.

Some other beneficial drugs, however not widely recommended, include nitrates, diuretics, and digoxin. Besides, patients containing prosthetic material in their hearts, like simulated valves or valves repaired with prosthetic material, or a cardiac transplantation should essentially go through prophylactic antibiotic therapy before any kind of dental procedures. The patients with severe AR are recommended not to go through the beta-blocker therapy for the reason that reduced heart rate in such patients might prolong the diastole thereby making AR worse. However, researches have shown that beta blocker therapy is related to an important survival benefit for patients with severe AR and hopefully, further researches might allow the recommendation for the same in future.