Aortic Regurgitation Workup

Laboratory testing in patients with aortic regurgitation (AR) should be guided by the clinical scenario. For example, in patients with AR due to suspected infective endocarditis, peripheral blood counts and cultures may help clarify the diagnosis and identify the causative organism. Specific serologic tests may assist in the diagnosis of rheumatological causes. Laboratory assessment of renal and hepatic function may play an important role in determining a patient's eligibility for certain vasodilator or other drug therapy.

• Transthoracic echocardiography should be performed in all patients with suspected AR, and periodically in patients with confirmed AR of significant severity. Echocardiography is a highly accurate test in AR, with sensitivity and specificity well in excess of 90%. In addition, echocardiographic parameters are used to determine the optimal timing of surgery in many cases.^[5] Important echocardiographic findings in AR include the following:

  • Aortic valve structure and morphology (bileaflet versus trileaflet, flail, thickening)
  • Presence of vegetations or nodules (may require transesophageal echocardiography in selected cases)
  • Severity of AR
    • Color Doppler jet width (the vena contracta width is usually >65% of the width of the left ventricular outflow tract in severe AR)
    • Vena contracta width
    • Regurgitant volume, fraction, and orifice area
    • Premature closure of the mitral valve (seen in severe AR) and opening of the aortic valve (with severely elevated LV end-diastolic pressure)
    • Pressure half-time (usually < 300-350 ms with significant AR)
  • Associated lesions of the aorta, including dilation, aneurysm, dissection, or ectasia
  • LV structure and function
    • LV hypertrophy and dilation
    • EF and end-systolic dimension are key determinants of outcome
    • Surgery recommended if EF is ≤ 55% or if end-systolic dimension is >55 mm^[5]
• Standard chest radiography may show evidence of structural abnormalities (aortic dilation, prosthetic valve dislodgement, aortic valvular calcification) or functional compromise (pulmonary edema, cardiomegaly).
• Radionuclide imaging may provide complementary clinical information, including AR regurgitant fraction and LV/RV stroke volume ratio (often >2 in severe AR).
• Cardiac computed tomography (CT) and magnetic resonance imaging (MRI) have not yet achieved widespread adoption in the management of AR, although support in the literature is increasing for the potential clinical use of these imaging techniques.^{[18, 19, 20]}

• Electrocardiography findings are nonspecific but may include evidence of the following:

  • LV hypertrophy
  • Left axis deviation
  • Left atrial enlargement
  • LV volume overload pattern (prominent Q waves in leads I, aVL, and V₃ to V₆ and relatively small r waves in V₁)
  • LV conduction defects (typically late in the disease process)
• Exercise treadmill testing may be used to guide recommendations for surgical therapy in patients with chronic severe AR and equivocal symptoms.^[5] However, the role of stress echocardiography in patients with AR remains uncertain, and further studies may be needed before it can be recommended for routine clinical use.^[21]

• Cardiac catheterization is not always required in all patients with chronic AR but may provide extremely valuable clinical information, especially in patients who are contemplating surgery. Class I indications for cardiac catheterization under current American College of Cardiology/American Heart Association guidelines include the following:^[5]

  • Assessment of coronary anatomy prior to aortic valve surgery in patients with risk factors for coronary artery disease
  • Assessment of severity of AR, LV function, or aortic root size when noninvasive tests are inconclusive or discordant with clinical findings
• Aortic angiography, which may be performed during a cardiac catheterization procedure, may provide useful information regarding the severity of the patient's AR. Traditional angiographic grading is as follows:

  • Mild (1+): A small amount of contrast enters the left ventricle during diastole and clears with each systole.
  • Moderate AR (2+): Contrast enters the LV with each diastole, but the LV chamber is less dense than the aorta.
  • Moderately severe AR (3+): The LV chamber is equal in density with the ascending aorta.
  • Severe AR (4+): Complete, dense opacification of the LV chamber occurs on the first beat and the LV is more densely opacified than the ascending aorta.
• Intra-aortic balloon counterpulsation is contraindicated in patients with severe AR.

Histological valvular findings in patients with AR depend on the cause of the patient's AR. Patient with congenital abnormalities can usually be easily characterized noninvasively or grossly at the time of surgery or during pathological inspection. Aortic root dilatation may be present in up to 25% of patients with AR due to bicuspid valve. Many patients with a bicuspid aortic valve have concurrent aortopathy including connective tissue and cellular abnormalities that predispose to aortic dilation, aneurysm, and dissection.^[8]