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Aortic Stenosis

Aortic stenosis refers to narrowing of the aortic valve opening.  The three causes of aortic stenosis are 1) congenital abnormality resulting in one or two cusps of the valve rather than the normal variation of three, 2) calcification of the valve with increasing age and 3) rheumatic heart disease. Worldwide, the most common cause is rheumatic heart disease whereas in the United States, the most common cause is calcified disease and congenital bicuspid valve.

Signs, symptoms and complications

The clinical signs and symptoms of aortic stenosis vary depending on the time of presentation. When aortic stenosis is severe and progressed, the patients will develop heart failure, syncope or transient loss of consciousness and angina or pain caused by reduced blood flow to the heart due to obstruction of the coronary arteries. The most common symptoms include difficulty breathing, dizziness and angina with exertion. It is important to rule out non-cardiac causes of such symptoms including lung and gastrointestinal diseases.

On physical exam, patients with aortic stenosis will have a murmur described as systolic ejection murmur which is heard best in the right chest between ribs 2 and 3 and radiates to the carotid arteries. The intensity and timing of the murmur may be associated with the severity of the stenosis, with loud and late murmurs usually indicative of severe stenosis.

Aortic stenosis poses certain risks in patients which can have life threatening consequences. Patients with aortic stenosis can develop abnormal heart rhythms including atrial fibrillation, ventricular tachycardias and bradycardia or decreased heart rate. Abnormal heart rhythms can potentially cause sudden cardiac death. Patients are also at risk of developing ineffective endocarditis or an infection of the valve.  Other risks included increased tendency to bleed in the gastrointestinal tract, submucosal layer and skin and embolism or formation of blood clots in major blood vessels within the brain and body.

Diagnostic tests

The testing involved in evaluating a patient with aortic stenosis includes performing an electrocardiogram or EKG to check the rhythm of the heart, a chest X-ray to evaluate changes in the shape of the heart and valve calcifications and an echocardiogram (ECHO) which uses an ultrasound probe to evaluate the heart shape, valvular motion and pulmonary artery pressure. If the ECHO does not properly show the heart, a CT or MRI of the aorta may be necessary. In some cases, a cardiac catheterization may be warranted to measure the flow of blood through the valve.

Management

Patients with aortic valve stenosis may be advised not to play strenuous sports, even if they do not have symptoms. Medications can be utilized to manage the symptoms associated with aortic stenosis, however they do not prevent the progression of valvular disease. Medications that treat heart failure, such as diuretics, beta blockers or nitrates may be used. High blood pressure due to aortic stenosis may also be treated with antihypertensives. However, this must be done slowly so the blood pressure does not drop suddenly.

Prophylactic antibiotics are currently not recommended for the prevention of infective endocarditis in patients who undergo dental procedures and subsequently develop bacteremia or blood infection.

The survival of patients with aortic stenosis dramatically decreases once patients develop signs of severe aortic stenosis including angina, syncope or heart failure.  Aortic valve replacement is recommended for patients who develop symptoms related to aortic stenosis and is considered the most effective treatment in order to improve survival. The aortic valve can be replaced surgically or with the use of a trans-catheter. Trans-catheter aortic valve implantation repairs the aortic valve without removing the old, damaged valve. A full collapsible valve is delivered to the site through a catheter. The new valve pushes the leaflets of the old valve out of the way and takes over the regulation of the blood flow.

For patients who do not develop symptoms, the American College of Cardiology and American Heart Association recommend valve replacement in patients who have a reduced ejection fraction (<50%), measured on an echocardiogram. Other factors considered for valve replacement include the likelihood of aortic stenosis progression which depends on age, calcification and coronary artery disease. The severity of stenosis based on specific valve dimensions and an abnormal stress test, a test used to assess the heart for ischemia or reduced perfusion can also play a role in the decision.

Conclusion

Aortic stenosis is narrowing of the aortic valve opening due to congenital abnormalities, age related calcifications and rheumatic heart disease. Patients with aortic stenosis can have no symptoms, mild symptoms or severe symptoms. The diagnosis of aortic stenosis relies on patient presentation as well as various tests. Patients who develop signs of severe aortic stenosis and do not receive aortic valve replacement have a poor prognosis.  When considering management of aortic stenosis, it is important to compare the combined risk of  aortic valve procedures and risk associated with prosthetic valves with the risk of complications and death due to aortic stenosis.

References

Lester SJ and Abbas AE. Aortic Stenosis, Chapter 17 of Current Diagnosis and Treatment Cardiology, 4th edition. McGraw Hill. 2014.

Otto, CM. Clinical  features and evaluation of aortic stenosis in adults. Uptodate. Last updated August 4, 2014.

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