Master the board step 3

Master the Boards: USMLE Step 3
Pulmonary edema is associated with a decrease in cardiac output because of pump
failure, which results in the backup of blood into the left atrium and an increased
wedge pressure. There is also an increase in right atrial pressure, which is the same as
saying jugular venous distention. Increases in sympathetic outflow will increase systemic
vascular resistance in an attempt to maintain intravascular filling pressure. Choice B represents
hypovolemic shock, such as dehydration. Choice C represents septic shock, which
is driven by massive systemic vasodilation, such as from gram-negative sepsis. Choice D
represents pulmonary hypertension.
Basic Science Correlate
Mechanism of Increased Wedge Pressure in CHF
Wedge pressure = Left atrial (LA) pressure
The inflated balloon blocks pressure from behind catheter, making the catheter
tip pick up flow from “in front,” or downstream. “Downstream” for the
pulmonary capillaries means the left atrium.
LV failure = Increased LA pressure = Increased wedge pressure
Chronic Management of CHF
All patients, having been stabilized from acute pulmonary edema, should have
an echocardiogram to establish whether there is systolic dysfunction with a
low ejection fraction or diastolic dysfunction with a normal ejection fraction.
Long-term management of dilated cardiomyopathy or systolic dysfunction
is based on the use of ACE inhibitors, beta blockers, and spironolactone.
Diuretics are also used but have not been proven to lower mortality. Digoxin
is used to decrease symptoms and decrease the frequency of hospitalization but
has not been shown to decrease mortality in congestive failure. ARBs can be
used interchangeably with ACE inhibitors. The beta blockers with evidence
for lowering mortality in CHF are metoprolol, carvedilol, and bisoprolol. ACE
inhibitors and beta blockers are indicated for CHF patients with systolic dysfunction
at any stage of disease. Spironolactone lowers mortality but has only
been proven to do so for more advanced, symptomatic disease; any patient
originally presenting with pulmonary edema should get spironolactone.
Spironolactone is anti-androgenic. Spironolactone causes gynecomastia and
erectile dysfunction in men; switch to eplerenone. Eplerenone is a mineralocorticoid
antagonist. Eplerenone lowers mortality in CHF without the antiandrogenic
side effects of spironolactone.
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Diastolic dysfunction is treated with beta blockers and diuretics. However,
you have to be careful not to overuse diuretics. The benefit of ACE inhibitors
for diastolic dysfunction is not clear. Digoxin and spironolactone definitely do
not help diastolic dysfunction.