Aortic Regurgitation - Diagnosis

The ECG in patients with aortic regurgitation is non-specific and may show LVH and left atrial enlargement.

In acute aortic regurgitation, sinus tachycardia due to the increased sympathetic nervous tone may be the only abnormality on ECG. The chest radiograph is also non-specific in aortic regurgitation. Cardiomegaly is present in patients with chronic aortic regurgitation. In acute aortic regurgitation, pulmonary edema is almost universally present. If the aortic regurgitation is due to an aortic dissection, the mediastinum may appear widened.

Echocardiography is crucial to the identification of aortic regurgitation, determining the etiology, and estimating the severity. Echocardiography is almost 100% sensitive and specific for the detection of aortic regurgitation. The actual regurgitant jet can be directly visualized using color flow Doppler. This is extremely important in patients with acute aortic regurgitation since the physical examination may not be revealing of any valvular abnormality.

The etiology of aortic regurgitation can often be determined using echocardiography. Structural abnormalities such as calcification or thickening of the AV can be seen. Vegetations on the AV may be identified (transesophageal echocardiography is more sensitive) indicating endocarditis as the cause. A bicuspid AV or prolapse of the AV may be seen. The size of the aortic root can be measured and aortic dissections can be identified.

The severity of AR can be estimated using three parameters:

1. Regurgitant jet size
2. Pressure half-time
3. Regurgitant fraction

Regurgitant jet size is helpful by measuring the ratio of the aortic regurgitation jet diameter just below the leaflets of the aortic valve to the size of the LV outflow diameter. Ideally, the ratio should be zero since no regurgitant jet should be present. A ratio of < 24 is mild, 25-45 is moderate, 46-64 is moderately severe, and > 65 is severe.

The pressure half-time index is the time it takes for the initial maximal pressure gradient in diastole to fall by 50%. In patients with mild aortic regurgitation, this fall in pressure is gradual. In the setting of severe aortic regurgitation, a rapid drop in pressure gradient occurs. A pressure half-time of > 500 is considered mild aortic regurgitation, 500-349 is moderate, 349-200 is moderately severe, and < 200 is severe. The severity of aortic regurgitation assessed by using the pressure half-time is overestimated in patients with a significantly increased LVEDP.

The regurgitant fraction is perhaps a more straightforward means of assessing the severity of aortic regurgitation. The regurgitant fraction is the percentage of stroke volume that returns to the left ventricle from the aorta during diastole. For example, a regurgitant fraction of 33% would indicate that one-third of the total stroke volume returns to the LV retrograde across the aortic valve during diastole. A regurgitant fraction of < 20% indicates mild aortic regurgitation, 20-35% indicates moderate aortic regurgitation, 36-50% indicates moderately severe aortic regurgitation, and > 50% severe aortic regurgitation.

It is important to note that the severity of aortic regurgitation assessed using echocardiography is dependent on the hemodynamic status of the patient at the time of the evaluation, most importantly, the afterload.

Cardiac catheterization for hemodynamic measurements is not necessary in the majority of patients with aortic regurgitation because of echocardiography. During cardiac catheterization, aortic regurgitation can be detected by injecting contrast into the aortic root and visualizing the appearance of contrast in the left ventricle. Catheterization can also assess for aortic root disease. A number of factors affect the grading of severity of aortic regurgitation during catheterization. If the catheter is positioned too closely to the aortic valve, the amount of aortic regurgitation will be overestimated. The volume and rapidity of injection of contrast into the aortic root affects the amount of aortic regurgitation visualized. As previously mentioned, the hemodynamic parameters (mostly afterload) at the time of assessment also affect the severity of aortic regurgitation. The grading scale for aortic regurgitation used during catheterization is below. Cardiac catheterization can also measure LVEDV and LVEDP which can be helpful in determining the severity of aortic regurgitation. Cardiac catheterization is also indicated if aortic valve replacement is going to be performed so that the coronary arteries can be imaged. If significant coronary atherosclerosis is present, coronary artery bypass grafting can be done at the same time as the valve replacement.

PROCEED TO AORTIC REGURGITATION - TREATMENT

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