Aortic Stenosis

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Aortic stenosis rheumatic, gross pathology 20G0014 lores

Aortic Stenosis (AS) is a cardiac condition resulting from the partial opening of the aortic valve. This valve plays a crucial role in controlling blood flow from the left ventricle directly to the aorta. In an ideal state, the aortic valve ensures an unhindered flow between these two areas. However, certain situations may cause the valve to become narrower than it should be, creating an obstruction in the blood flow. This condition is termed as aortic valve stenosis or, in short, aortic stenosis, which can also be abbreviated as AS.

Pathophysiology

Studies in cardiac pathology (1911)

A stenotic aortic valve causes a noticeable pressure gradient between the left ventricle (LV) and the aorta. The greater the valve constriction, the more significant this gradient becomes. For instance, a mild AS may present a gradient of 20 mmHg, meaning that while the LV might generate a pressure of 140 mmHg at peak systole, the aorta receives only 120 mmHg. This discrepancy can lead to a situation where a blood pressure cuff detects a standard systolic blood pressure, but the actual pressure within the LV is significantly higher.

Moreover, AS compels the left ventricle (LV) to exert more pressure to counteract the enhanced afterload instigated by the stenotic aortic valve, ensuring proper blood ejection. Severe aortic stenosis results in a more extensive gradient difference between the left ventricular systolic pressures and aortic systolic pressures. Over time, the additional pressures force the myocardium (the heart's muscle) of the LV to undergo hypertrophy (an increase in muscle mass), manifesting as thickened LV walls. The hypertrophy seen in AS is typically concentric, denoting an even thickening of the LV walls.

Etiology

Various factors can cause aortic stenosis. These include conditions like acute rheumatic fever, congenital issues such as bicuspid aortic valve and congenital anomalies. Aging can also lead to aortic valve calcification, resulting in stenosis.

Physical examination

Often, AS is identified during its asymptomatic phase through routine heart examinations. A distinguishing factor is a pronounced systolic, crescendo-decrescendo murmur audible at the upper right sternal border and radiating towards the carotid arteries. To differentiate it from hypertrophic obstructive cardiomyopathy (HOCM), it's observed that the murmur's intensity increases with squatting but decreases during standing or isometric muscular contractions. Respiration doesn't alter the murmur's intensity. A stenosis of higher severity causes the murmur's peak to occur later within the crescendo-decrescendo phase. Over time, due to the increased left ventricular pressures from the stenotic aortic valve, the ventricle might develop hypertrophy, leading to diastolic dysfunction. As a result, a 4th heart sound may become audible because of the ventricle's stiffness. If the ventricular pressure continues to rise, ventricle dilation might occur, leading to the manifestation of a 3rd heart sound.

Symptoms and signs of aortic stenosis

When symptomatic, AS can lead to various conditions like syncope, angina, and congestive heart failure. Greater symptom prevalence typically indicates a graver prognosis. The primary treatment for this condition is replacing the diseased valve with options like a porcine aortic valve, cadaveric aortic valve, or an prosthetic aortic valve.

Associated symptoms

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AS is often linked with Heyde's syndrome, where it is associated with angiodysplasia of the colon. Recent studies have revealed that stenosis might cause a variant of von Willebrand disease, a condition that breaks down its associated coagulation factor (factor VIII-related antigen, also termed von Willebrand factor), attributed to increased turbulence near the stenotic valve.

Calculation of valve area

Determining the valve area of aortic stenosis can be achieved through several methods, with echocardiography-based measurements being the most prevalent. To interpret these measurements, the area is usually divided by the individual's body surface area, helping deduce the ideal aortic valve orifice area for the patient.

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