Investigations
1st investigations to order
ECG
Test
The ECG is abnormal in >90% of patients with AS, with the most common abnormality being left ventricular hypertrophy (LVH) due to pressure overload.[27]
Evidence of LVH and absent Q waves helps distinguish AS from other conditions such as aortic sclerosis with ischaemic heart disease.
Patients with AS can often have conduction disease manifesting as atrioventricular block, hemiblock, or bundle branch block.[Figure caption and citation for the preceding image starts]: ECG showing changes associated with left ventricular hypertrophyFrom the collection of Melanie Everitt MD, Heart Failure & Transplantation Program, Primary Children's Medical Center, Salt Lake City, UT; used with permission [Citation ends].
How to record an ECG. Demonstrates placement of chest and limb electrodes.
Result
may demonstrate left ventricular hypertrophy and absent Q waves, atrioventricular block, hemiblock, or bundle branch block
transthoracic echocardiography (TTE)
Test
TTE is the test of choice in the evaluation of suspected AS and for the evaluation of murmurs detected on physical examination. Doppler TTE can reliably and accurately detect the presence of a pressure gradient across the aortic valve. It can also assess left ventricle function and the presence of hypertrophy. It is essential for the diagnosis of AS and for serial evaluation once the diagnosis has been established.[26]
The American College of Cardiology/American Heart Association (ACC/AHA) guidelines recommend TTE when there is an unexplained systolic murmur, a single second heart sound, a history of a bicuspid aortic valve, or symptoms that might be due to AS.[26]
The ACC/AHA also recommend that measurements taken during echocardiography examination should be used to grade the severity of AS.[26]
Although murmur intensity does not correlate well with the haemodynamic significance of the associated lesion, grade 3 murmurs are generally thought to reflect more significant lesions and thus warrant further evaluation with TTE. In practice, most patients with suspected cardiac disease and a murmur on examination should have an echocardiogram.
In the UK, the National Institute for Health and Care Excellence (NICE) recommends to consider echocardiography if the patient has a murmur and no other signs or symptoms, but valve disease is suspected based on the nature of the murmur, family history, age (especially if >75 years), or medical history (e.g., history of atrial fibrillation).[28]
NICE recommends to arrange echocardiography for any patient with suspected valve disease and signs or symptoms of valve disease (such as peripheral oedema, angina, or breathlessness), an abnormal ECG, or an ejection systolic murmur with reduced second heart sound but no other signs or symptoms.[28]
NICE further recommends to refer for urgent (within 2 weeks) specialist assessment and echocardiography if valve disease is suspected, and the patient has a systolic murmur and exertional syncope, or a murmur and severe symptoms (such as angina or breathlessness on minimal exertion or at rest) which are thought to be due to valvular heart disease.[28]
Result
elevated aortic pressure gradient; measurement of valve area and left ventricular ejection function
chest x-ray
Test
In patients with known or suspected valvular heart disease, a chest x-ray is indicated as part of the initial assessment to assess the presence or absence of pulmonary congestion or other lung pathology.[26]
Result
may be normal; may show pulmonary congestion or other lung pathology
Investigations to consider
Cardiac computed tomography (CT)
Test
Cardiac CT allows both qualitative and quantitative evaluation of the calcium burden on the aortic valve.
The American College of Cardiology/American Heart Association guidelines recommend use of the Agaston aortic valve calcium score, which can be calculated and used to make the diagnosis of severe AS when echocardiography or invasive measurements are inconclusive. This is particularly helpful in the evaluation of low-flow low-gradient AS.[29][30]
In the UK, the National Institute for Health and Care Excellence recommends to consider using cardiac CT to measure aortic valve calcium score if the severity of symptomatic AS is uncertain.[28]
Result
demonstrates stenotic aortic valve
cardiac MRI
Test
Cardiac MRI (cMRI) provides detailed, dynamic images of the heart. It allows for analysis of cardiac function and haemodynamics. cMRI may be useful when trying to distinguish between true valvular stenosis and subvalvular stenosis related to a subvalvular membrane.
Owing to the complexity of cMRI, the American College of Cardiology/American Heart Association recommend transthoracic echocardiography as the preferred test for evaluating AS, but state that cMRI may be a good option when echocardiography fails to yield quality images.[29]
If cMRI shows mid-wall fibrosis in adults with severe AS, the National Institute for Health and Care Excellence in the UK recommends enhanced follow up (e.g., more frequent reviews) and further assessment (e.g., stress echocardiography) to monitor the need for intervention.[28]
Late gadolinium enhancement in particular has shown potential for use in AS risk stratification.[31]
Result
demonstrates stenotic aortic valve
CT angiography
Test
CT angiography (CTA) uses a thin-section CT acquisition that is timed to coincide with peak arterial or venous enhancement. The resulting 3-dimensional image allows characterisation and reporting of aortic valve morphology.[29] CTA can also be used to screen for coronary artery disease before valular surgery.[32]
Result
demonstrates aortic valve morphology
magnetic resonance angiography
Test
MR angiography (MRA) has been found to produce good reproducibility of aortic annulus dimensions and calcifications in comparison with cardiac CTA, even in the presence of arrhythmias.[33] MRA may not be suitable; however, when there is a high-susceptibility artifact, magnetic field incompatible devices, and severe arrhythmia.[29] MRA examination is also technically more complex, with longer study time and a higher required degree of patient cooperation, which some patients may find problematic.[29][34]
Result
ECG exercise stress testing
Test
Consider in asymptomatic patients and those with equivocal symptoms.[26]
Many experts advocate the use of symptom-limited exercise testing in asymptomatic patients with severe AS as a means of risk-stratification for the development of symptoms, and for the need for surgery.
Exercise echocardiography may add additional diagnostic and prognostic information.[37][38][26]
Symptomatic patients should not have exercise testing and should be referred for valve replacement.[26]
How to record an ECG. Demonstrates placement of chest and limb electrodes.
Result
asymptomatic patients: a positive exercise stress test demonstrates either decreased exercise tolerance (compared with normal for age and sex) or a drop in systolic blood pressure of 10 mmHg with exercise
dobutamine stress echo
Test
The American College of Cardiology/American Heart Association recommend this test for patients with a low transvalvular gradient and left ventricular systolic dysfunction (low ejection fraction), in order to identify pseudostenosis and the presence of contractile reserve.[26]
Patients with pseudostenosis do not have severe AS and should not be referred for aortic valve replacement.
The presence of contractile reserve suggests a better prognosis and lower perioperative risk with surgical aortic valve replacement; however, it does not predict outcomes after transcatheter aortic valve implantation.
The National Institute for Health and Care Excellence in the UK recommends that stress echocardiography be used as part of further assessment to monitor need for intervention if cardiac MRI shows mid-wall fibrosis in adults with severe AS.[28]
Result
may demonstrate pseudostenosis and presence of contractile reserve (≥20% increase in stroke volume with dobutamine)
Transoesophageal echocardiography (TOE)
Test
TOE provides alternate detailed views of the aortic valve apparatus, and is frequently used in patients undergoing valve surgery or transcatheter aortic valve replacement.[29]
Result
may show an echo-dense valve with reduced or no cusp motion; may also show otherwise unexplained left ventricular hypertrophy with or without atrial enlargement
cardiac catheterisation
Test
Catheterisation allows for direct measurement of the pressure gradient. The sensitivity and specificity of the test are high.
Due to the invasive nature, this test is useful for diagnosis when the echocardiogram is inconclusive or discrepant from other findings. It can also be useful in the diagnosis of low-flow low-gradient aortic valve stenosis.
Result
elevated aortic pressure gradient
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