Introduction
Background
Aortic stenosis (AS) is the obstruction of blood flow across the aortic valve. Aortic stenosis has several etiologies including congenital unicuspid or bicuspid valve, rheumatic fever, and degenerative calcific changes of the valve.
Stenotic aortic valve (macroscopic appearance).
Pathophysiology
When the aortic valve becomes stenotic, resistance to systolic ejection occurs and a systolic pressure gradient develops between the left ventricle and the aorta. Stenotic aortic valves have a decreased aperture that leads to a progressive increase in left ventricular systolic pressure. This leads to pressure overload in the left ventricle, which, over time, causes an increase in ventricular wall thickness (ie, concentric hypertrophy). At this stage, the chamber is not dilated and ventricular function is preserved, although diastolic compliance may be affected.
Eventually, however, the left ventricle dilates. This, coupled with a decrease in compliance, is associated with an increase in left ventricular end-diastolic pressure, which is increased further by a rise in atrial systolic pressure. A sustained pressure overload eventually leads to myocardial decompensation. The contractility of the myocardium diminishes, which leads to a decrease in cardiac output. The elevated left ventricular end-diastolic pressure causes a corresponding increase in pulmonary capillary arterial pressures and a decrease in ejection fraction and cardiac output. Ultimately, congestive heart failure (CHF) develops.
Frequency
United States
Aortic stenosis is a relatively common congenital cardiac defect. Incidence is 4 in 1000 live births.
Mortality/Morbidity
Sudden cardiac death occurs in 3-5% of patients with aortic stenosis. Adults with aortic stenosis have a 9% mortality rate per year. Once symptoms develop, the incidence of sudden death increases to 15-20%, with average survival duration of less than 5 years. Patients with exertional angina or syncope survive an average of 3 years. After the development of left ventricular failure, life expectancy is slightly greater than 1 year.
Sex
Among children, 75% of cases of aortic stenosis are in males.
Age
Aortic stenosis usually is not detected until individuals are school aged. Aortic stenosis exists in up to 2% of those who are younger than 70 years. The etiology of aortic stenosis in those aged 30-70 years can be rheumatic disease or calcification of a congenital bicuspid valve. Patients with a biscuspid valve are more prone to develop aortic stenosis at an earlier age (fifth to sixth decades of life) than those with a tricuspid valve (seventh to ninth decades).1 In those older than 70 years, degenerative calcification is the primary cause of aortic stenosis. Among people older than 75 years, 3% have critical aortic stenosis.2
Clinical
History
Aortic stenosis usually has an asymptomatic latent period of 10-20 years. Symptoms develop gradually. Ultimately, patients experience the classic triad of chest pain, heart failure, and syncope.3 Typical symptoms include the following:
- Palpitations
- Fatigue (may be an early symptom among children)
- Visual disturbances
- Gradual decrease in physical activity with insidious progression of fatigue and dyspnea on exertion
- Angina pectoris (30-40%)
- Patients may have a higher incidence of nitroglycerin-induced syncope than the general population.
- Always consider aortic stenosis as a possible etiology for a patient in the ED with particular hemodynamic sensitivity to nitrates.
- Syncope during exertion - Proposed mechanisms include arrhythmias and left ventricular failure with an abrupt decline in cardiac output.4
- Congestive heart failure4 - Symptoms of left ventricular failure (eg, dyspnea on exertion, nocturnal cough, orthopnea, paroxysmal nocturnal dyspnea, hemoptysis) may occur. This is due to an elevation of the pulmonary capillary pressure from left ventricular dilation and reduced compliance.
- GI bleeding - Heyde syndrome4
Physical
- The most common signs of aortic stenosis include a pulse of small amplitude.3
- Palpation reveals a laterally displaced apex reflecting the presence of left ventricular hypertrophy.
- A systolic thrill may be palpable at the base of the heart, in the jugular notch, and along the carotid arteries.
- Crescendo-decrescendo systolic ejection murmur begins shortly after the first heart sound. The intensity increases toward midsystole, then decreases, and the murmur ends just before the second heart sound. It is generally a rough, low-pitched sound that is loudest at the base of the heart and most commonly is appreciated in the second right intercostal space that radiates to the carotids.4 An ejection click may be auscultated. This is associated with bicuspid valves.
- An audible fourth heart sound indicates the presence of left ventricular hypertrophy in severe aortic stenosis. Once the left ventricle dilates and fails, a third heart sound may be audible.
- Pulsus parvus et tardus: This is an arterial pulse with a delayed and plateaued peak, decreased amplitude, and gradual downslope.
- A high-pitched, diastolic blowing murmur may be present if the patient has associated aortic regurgitation.
Causes
The ventricular pressure required to deliver a certain cardiac output at the required perfusion pressure is the pressure gradient across the valve in systole. This pressure gradient defines the degree of aortic valve obstruction.
- Newborns with significant aortic stenosis develop congestive heart failure (CHF) within the first week of life. The left ventricle is often too small to be compatible with life. The newborn heart develops left-to-right shunting through the patent foramen ovale, which leads to worsening CHF.
- Congenital aortic stenosis caused by a congenital unicuspid or bicuspid aortic valve is usually asymptomatic in the otherwise healthy developing child. It often is diagnosed on routine physical examination, although a child may present with angina pectoris with exercise.
- As rheumatic fever decreases in frequency, so does rheumatic fever–induced aortic stenosis. These patients have a fibrous contracture with shortening of the cusps due to recurrent inflammation from rheumatic carditis. Adjacent cusps tend to fuse at the commissures. This causes a form of acquired unicuspid or bicuspid aortic valve. Calcifications may develop, but the primary cause of stenosis is the adhesions that fuse the cusps. In patients older than 70 years, the most common cause of aortic stenosis is degenerative calcification of the valve. Mönckeberg senile calcific aortic stenosis occurs in elderly patients in whom all 3 cusps are highly calcified.
- Calcific aortic stenosis also occurs in older patients with congenital or acquired bicuspid valves. Congenital bicuspid valves cause calcific aortic stenosis 4 times more frequently than acquired forms do.
More on Aortic Stenosis |
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| Differential Diagnoses & Workup: Aortic Stenosis |
| Treatment & Medication: Aortic Stenosis |
| Follow-up: Aortic Stenosis |
| Multimedia: Aortic Stenosis |
| References |
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References
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Further Reading
Keywords
AS, aortic stenosis, congenital unicuspid or bicuspid valve, rheumatic fever, degenerative calcific changes of the valve, aortic valve, congestive heart failure, CHF, congenital cardiac defect, congenital heart defect, left ventricular failure, rheumatic disease, calcification of a congenital bicuspid valve, degenerative calcification of the valve
