Approach Considerations
Laboratory testing in patients with 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 to clarify the diagnosis and to identify the causative organism. Specific serologic tests may assist in the diagnosis of rheumatologic 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.
Laboratory studies for AR may also include the following:
-
Complete blood count (CBC)
-
Prothrombin time (PT)/activated partial thromboplastin time (aPTT)
-
Type and screen
-
Electrolytes
-
VDRL
-
Lactate dehydrogenase
Early surgical intervention is recommended in cases of AR caused by infective endocarditis, and emergent intervention is warranted in cases caused by aortic dissection.
Imaging for Aortic Regurgitation
Transthoracic echocardiography
Transthoracic echocardiography should be performed in all patients with suspected AR, and should be performed periodically in patients with confirmed AR of significant severity. [27]
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. [4] 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
-
Vena contracta width - In severe AR, the vena contracta width is usually more than 65% of the width of the LV outflow tract
-
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 less than 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
-
Ejection fraction (EF) and end-systolic dimension - These are key determinants of outcome; surgery is recommended if the EF is 55% or less or if the LV end-systolic dimension is more than 55 mm [4]
Echocardiographic assessment of AR following TAVR is much more challenging because the AR is usually paravalvular and occurs in the context of acute hemodynamic changes, as well as prosthetic materials that may impair image quality. Proposed TEE criteria for identifying significant AR include a regurgitant jet extending below the LV outflow tract, multiple AR jets, holodiastolic flow reversal in the descending aorta, and circumferential extent of the jet in short axis (>10% moderate, ≥ 30% severe). [6] Further research is needed to validate these criteria for clinical application.
Exercise treadmill testing
Exercise treadmill testing may be used to guide recommendations for surgical therapy in patients with severe chronic AR and equivocal symptoms. [4] 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. [28]
Chest radiography
Standard chest radiography may show evidence of structural abnormalities (aortic dilation, prosthetic valve dislodgement, aortic valvular calcification) or functional compromise (pulmonary edema, cardiomegaly).
In acute aortic regurgitation, the following may be seen:
See the list below:
-
Minimal cardiac enlargement
-
Normal aortic root/arch
-
Pulmonary venous pattern increased
In chronic aortic regurgitation, the following may be seen:
-
Marked cardiac enlargement
-
Prominent aortic root/arch
-
Normal pulmonary venous pattern
Radionuclide imaging
Radionuclide imaging may provide complementary clinical information, including the AR regurgitant fraction and the LV/right ventricular (RV) stroke volume ratio. In the absence of mitral regurgitation and tricuspid regurgitation, an LV/RV stroke volume ratio of 2.5 or more denotes severe aortic regurgitation.
Demonstration of a fall in the EF with exercise is one of the most important indications for surgery in patients who are asymptomatic.
Aortic angiography
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 LV 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 to 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
Assessment of the anatomy of the aorta and coronary ostia usually produces normal findings, except for the visible reflux of dye from the aortic root into the ventricle.
Cardiac CT scanning and magnetic resonance imaging (MRI)
Cardiac computed tomography (CT) scanning 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. [29, 30, 31]
In a study that used quantitative flow measurement by cardiac MRI (CMR) with calculation of regurgitant fraction (RF) to assess aortic regurgitation (AR), Orwat et al found that TTE significantly underestimated the presence of moderate AR, compared with CMR. [32] Overall, there was only fair agreement between CMR and TTE regarding the grading of AR (weighted κ = 0.33). The investigators indicated given that higher AR severity on echocardiography has been associated with worse patient outcome, prospective studies of the potential incremental prognostic value of CMR are warranted in this setting. [32]
In a separate study, Harris et al noted that CMR-derived regurgitant volume was more predictive of clinical outcomes than that derived by TTE in patients with AR, whereas both imaging modalities demonstrated similar performances for patients with mitral regurgitation. [33] Regurgitant volume greater than 50 mL on CMR identified those with AR at high risk, with 50% undergoing valve surgery, compared to 0% in those whose regurgitant volumes were 50 mL or less.
Electrocardiography
Electrocardiographic 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
Cardiac Catheterization
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. Indications for cardiac catheterization include the following [4] :
-
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 are discordant with clinical findings
Histologic Findings
Histologic valvular findings in patients with AR depend on the AR’s cause. Patients with congenital abnormalities can usually be easily characterized noninvasively or grossly at the time of surgery or during pathologic inspection.
Aortic root dilation 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 predisposes these individuals to aortic dilation, aneurysm, and dissection. [8]
-
Aortic regurgitation. Color Doppler echocardiogram.
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Aortic regurgitation. Doppler echocardiographic signals may be reviewed to evaluate the severity of disease.
-
Aortic regurgitation. Two-dimensional (2D) color Doppler echocardiography.
-
Aortic regurgitation. Aortic-root angiography shows regurgitation of contrast material into the left ventricle (LV).
-
Aortic regurgitation. Chest radiograph in a patient with aortic dissection and acute aortic regurgitation shows a cardiac silhouette of essentially normal dimension.
Tables
LVESD (mm) |
LVEDD (mm) |
Dimensions |
Clinical Evaluation |
Echocardiogram |
< 45 |
< 60 |
Stable |
6-12 months |
12 months |
< 45 |
< 60 |
Increasing |
3 months |
3 months |
45-50 |
60-70 |
Stable |
6 months |
12 months |
45-50 |
60-70 |
Increasing |
3 months |
3 months |
50-55 |
70-75 |
Stable |
6 months |
6 months |
50-55 |
70-75 |
Increasing |
3 months |
3 months |
>55 |
>75 |
|
Surgery recommended |
|
Aortic valve replacement (AVR) indications Note: STS guidelines recommend “valve replacement or valve repair” |
AHA/ACC (2014) [4] |
ESC/EACTS (2012) [43] |
STS (2013) [9] |
Symptomatic severe AR |
Class I |
Class I |
Class I |
Asymptomatic chronic severe AR and left ventricular ejection fraction (LVEF) ≤50% |
Class I |
Class I |
Class I |
Severe AR when undergoing other cardiac surgery |
Class I |
Class I |
Class I |
Asymptomatic severe AR with normal LVEF (≥50%) but with severe LV dilation (LVESD >50mm) |
Class IIa-Reasonable |
Class IIa-Reasonable |
Class IIa-Reasonable |
Moderate AR when undergoing other cardiac surgery |
Class IIa-Reasonable |
Class IIb-Consider |
|
Asymptomatic severe AR and normal LVEF (≥50%) but with progressive severe LV dilation (LVEDD >65 mm) if surgical risk is low |
Class IIb-Consider |
Class IIa-Reasonable |
Class IIb-Consider |
Not indicated for asymptomatic patients with mild, moderate, or severe AR and normal LV systolic function at rest when the degree of LV dilation is not moderate or severe |
Class III |
