Aortic Stenosis
last authored: Oct 2013, David LaPierre
last reviewed:
Introduction
Aortic stenosis (AS), or a narrowing and hardening of the aortic valve in the heart, is the most common of all valvular abnormalities. When mild, AS can be of no significance; however, with moderate to severe disease, AS can cause obstruction of blood flow from the heart to such a degree that function is profoundly progressively impaired, and angina, heart failure, and death can result.
AS is commonly identified through cardiac auscultation
The Case of Jill B.
Jill is a 78 year-old woman who comes to her doctor with a 6 month history of gradually worsening shortness of breath. As her doctor further evaluates her, he finds a loud systolic murmur. He worries about the possibility of aortic stenosis in Jill.
- How should he further evaluate her condition?
Causes and Risk Factors
AS is usually the consequence of calcification due to progressive 'wear and tear' with aging. Incidence rises with age, with patients at age 60 beginning to develop evidence of AS
The aortic valve is normally a tricuspid valve. However, approximately 1-2% of the population has bicuspid valves - the most common congenital heart defect. Rates of AS are much higher in these people.
Other risk factors include:
- age
- lipids
- male
- rheumatic fever
Pathophysiology
Congenital stenosis leads to fusion of the valve, leaving only a small opening, creates extra work for the heart and results in LV hypertrophy and a murmur.
Aortic sclerosis is a normal mechanism of aging, with 20-40% of patients over 65 with sclerosis.
stenosis leads to gradual outflow obstruction, resulting in left ventricular hypertrophy, as well as potential cardiomyopathy and heart failure.
Calcium heaps up within the aortic cusps, protruding into the surfaces and preventing opening.
The Venturi effect states that as fluid flows through a narrowed aperture, velocity increases, but pressure decreases.
A gradually increasing pressure gradient can reach 100 mmHg in severe cases, where the valve area is 0.5-1cm2, compared to the normal 4 cm2. A valve area less than 0.7 cm2 is considered severe. The pressure gradient is >40 mmHg, with a Vmax of >4 m/s.
Vmax <2.5
Stroke volume <35ml/m2
Signs and Symptoms
- history
- physical exam
History
Patients can be asymptomatic for many years, but usually lead to some symptoms. The classical triad includes:
- dyspnea (most common)
- angina
- syncope
but developing myocardial ischemia can lead to angina, and congestive heart failure can follow. Syncope is considered the third cardinal symptom.
Physical Exam
On physical exam, a crescendo-decrescendo systolic ejection murmur can be heard.
A laterally displaced and sustained apical impulse can occur with left ventricular hypertrophy.
Carotid impulse is often diminished and delayed (pulsus parvus et tardus).
Brachial-radial delay
In late disease, signs of left heart failure can be evident, withpulmonary edema, increased jugular pressure.
An S4 heart sound may be heard. A2 can be diminished, and S2 can be paradoxically split.
Investigations
- lab investigations
- diagnostic imaging
Lab Investigations
Diagnostic Imaging
ECG principally shows left ventricular hypertrophy. Left bundle branch block is also common.
Echocardiography is the most useful diagnostic test, and can reveal the cause and extent of obstruction. Indicators include:
- Flow velocity (through doppler study)
Cardiac catheterization can confirm the diagnosis and evaluate for coronary artery disease.
Differential Diagnosis
The differential diagnosis of a heart murmur is described here.
Treatments
Medical treatment is ineffective, and surgery is the mainstay of treatment. This is best done when left ventricular systolic function is preserved. Treatment should be considered through risk stratification.
Balloon aortic valvuloplasty is most effective in young patients, while replacement is the treatment in most older folks.
Valvular replacement can be done with open surgery, or with transcatheter aortic valve replacement/implant (TAVR/TAVI). Surgery remains the preferred approach, though can be contraindicated for a number of reasons (previous cardiac surgery, aortic calcification, co-morbidities, etc).
Patients with
Consequences and Course
Most asymptomatic people have excellent prognosis.
For this with symptoms of angina or CHF, cardiac compensation has been exhausted and 50% of people will die within 5 years.
Valve replacement can lead to arrhythmia and heart block.
Resources and References
Topic Development
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