Master the board step 3

Master the Boards: USMLE Step 3
Physical Exam
Choose the cardiovascular (CV) exam, chest, and extremities.
Normal aortic valve
gradient is zero.
AS gives a crescendo-decrescendo systolic murmur. The murmur will be
heard best at the second right intercostal space and radiate to the carotid arteries.
The murmur will increase in intensity with leg raising, squatting, and amyl
nitrate. The murmur will decrease with Valsalva, standing, and handgrip. The
case may describe delayed carotid upstroke as well.
Basic Science Correlate
Mechanism of Crescendo/Decrescendo Murmur of AS
The first part of the cardiac cycle is isovolumetric contraction. With isovolumetric
contraction, no blood moves. No blood moving = No murmur. Peak flow occurs
in mid-systole. Peak flow = Peak noise. Hence, AS yields a diamond-shaped
crescendo-decrescendo murmur.
Diagnostic Testing
The transthoracic echocardiogram (TTE) is the best initial diagnostic test.
A transesophageal echocardiogram (TEE) is more accurate. Left heart catheterization
is the most accurate diagnostic test and allows the most accurate
method of assessing the pressure gradient across the valve. Mild disease is a gradient
< 30 mm Hg. Moderate disease is indicated by 30–70 mm Hg, and severe
disease is indicated by a gradient > 70 mm Hg. For CCS cases, also choose an
EKG and a chest x-ray, which will show left ventricular hypertrophy.
Balloon dilate AS only if
the patient is too sick to
undergo surgery.
Mechanical valves can wear
out after 15–20 years.
Treatment
Diuretics are the best initial therapy but will not alter long-term prognosis.
Further, overdiuresis is dangerous, and use of diuretics needs to be very
judicious.
The treatment of choice is valve replacement. Bioprosthetic valves (porcine,
bovine) will last 10 years on average, but do not require anticoagulation with
warfarin. Mechanical valves do not have to be replaced as often, but must also
be treated with warfarin to an INR of 2–3. Valve replacement is well tolerated,
even in the elderly. Valve replacement by catheter is done when a patient can’t
tolerate surgery.
Aortic Regurgitation (AR)
Hypertension, rheumatic heart disease, endocarditis, and cystic medial
necrosis cause AR. Rarer causes are Marfan’s syndrome, ankylosing spondylitis,
syphilis, and reactive arthritis. Reactive arthritis is an inflammatory arthritis
of large joints, inflammation of the eyes (conjunctivitis and uveitis), and
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