Investigation and diferential diagnosis of aortic stenosis

Investigations
The health care provider will be able to feel a vibration or movement when placing a hand over the person's heart. A heart murmur, click, or other abnormal sound is almost always heard through a stethoscope. There may be a faint pulse or changes in the quality of the pulse in the neck

Imaging tests
Chest radiography
o Chest radiographs may show cardiac enlargement. Minimal enlargement and more subtle signs of concentric hypertrophy without dilatation are present, including mildly enlarged heart size, rounding at the cardiac apex, and slight backward displacement of the heart as seen in lateral view.
o In later, more severe stages of aortic stenosis, radiographic signs of left atrial enlargement, pulmonary artery enlargement, right-sided enlargement, calcification of the aortic valve, and pulmonary congestion may be evident.

Echocardiography
o TTE-Two-dimensional transthoracic echocardiography can confirm the clinical diagnosis of aortic stenosis and provide specific data on left ventricular function. It can show the structure and function of the other valves as well.

Possible findings
 An aortic valve with no cusp motion is indicative of severe aortic stenosis.
 A decrease in the maximal aortic cusp separation is also indicative of severe aortic stenosis.
 The presence of otherwise unexplained left ventricular hypertrophy implies significant aortic stenosis.

o Using echo-Doppler techniques, the systolic pressure gradient across the aortic valve can be assessed. Doppler techniques also can help visualize any mitral or aortic regurgitation that might be present.

Other tests

Electrocardiography
o Generally, ECG is not a reliable test because of the wide variations seen in aortic stenosis and other cardiac conditions.
o An ECG of a patient with significant aortic stenosis most likely shows evidence of left ventricular hypertrophy. T-wave inversion and ST-segment depressions are common.

Cardiac catheterisation
Catheterization of the left side is performed to obtain information about the heart chambers on the left side (left atrium and left ventricle), the mitral valve (located between the left atrium and left ventricle), and the aortic valve (located between the left ventricle and the aorta). The left side is catheterized more often than the right.
Measuring the left ventricular end-diastolic and systolic volume and calculating the ejection fraction (EF) can quantitate the status of LV systolic pump function.

Stress testing
Stress testing gives your doctor information about how your heart works during physical stress. Some heart problems are easier to diagnose when your heart is working hard and beating fast.
During a stress test, you exercise (walk or run on a treadmill or pedal a bicycle) to make your heart work hard and beat fast. Tests are done on your heart while you exercise.
You may have arthritis or another medical problem that prevents you from exercising during a stress test. If so, your doctor may give you medicine to make your heart work hard, as it would during exercise. This is called a pharmacological stress test.

A stress test can detect the following problems, which may suggest that your heart isn't getting enough blood during exercise.
• Abnormal changes in your heart rate or blood pressure
• Symptoms such as shortness of breath or chest pain, which are particularly important if they occur at low levels of exercise
• Abnormal changes in your heart's rhythm or electrical activity

Exercise stress testing is usually not needed in patients with severe aortic stenosis to rule out coronary artery disease. However, closely monitored exercise stress testing may be of value to assess exercise capacity in asymptomatic patients. Abnormal results may prove greater disability than the patient would admit. In addition to watching for symptoms on the treadmill, one should also look for hemodynamic abnormalities, such as blood pressure decreases or failure to increase blood pressure normally, which can occur in the absence of symptoms. The test here is not used to screen for coronary disease.




Differential diagnosis

Myocardial Infarction
• Convex ST-segment elevation with upright or inverted T waves is generally indicative of myocardial infarction in the appropriate clinical setting.
• Troponin levels are now considered the criterion standard in defining and diagnosing myocardial infarction, according to the American College of Cardiology (ACC)/American Heart Association (AHA) consensus statement on myocardial infarction. Elevated amount of troponin in the blood is very likely due to a MI.

Hypovolemic Shock
• Hypovolemic shock refers to a medical or surgical condition in which rapid fluid loss results in multiple organ failure due to inadequate circulating volume and subsequent inadequate perfusion. Most often, hypovolemic shock is secondary to rapid blood loss
• Could be mistaken with aortic stenosis because of low BP and increased pulse rate. But easily ruled out by history and blood test.

Mitral Regurgitation
• The echocardiogram is commonly used to confirm the diagnosis of mitral regurgitation. Color doppler flow on the transthoracic echocardiogram (TTE) will reveal a jet of blood flowing from the left ventricle into the left atrium during ventricular systole.

Mitral Stenosis
• Use of chest x-ray, echocardiography, doppler’s echocardiography.

Mitral Valve Prolapse
• Echocardiography is the most useful method of diagnosing a prolapsed mitral valve. Two- and three-dimensional echocardiography are particularly valuable as they allow visualization of the mitral leaflets relative to the mitral annulus. This allows measurement of the leaflet thickness and their displacement relative to the annulus. Thickening of the mitral leaflets >5 mm and leaflet displacement >2 mm indicates classic mitral valve prolapse.