Cardiology
Clinical Case / MCQS / Uworld for Usmle step 2 / case 5 with answer and
explanation and references and Educational objective
A
69-year-old man comes to the emergency department due to left leg pain. The
patient says he used to have pain in both legs after walking a couple of
blocks, but several hours ago he suddenly started having severe left leg pain
while resting. He reports numbness in the left leg, and he is also experiencing
intermittent palpitations. The patient has a prolonged history of hypertension
and hyperlipidemia. His current medications include lisinopril, amlodipine, and
rosuvastatin. He has smoked a half pack of cigarettes daily for 45 years and
drinks 3-4 cans of beer weekly. His blood pressure is 130/80 mm Hg and pulse is
116/min and irregular. On examination, hair is sparse on both legs. The left
leg appears pale and feels colder than the right. Distal pulses are absent on
the left and diminished on the right. Sensation to light touch is decreased on
the dorsum of the left foot and leg. Ankle dorsiflexion is slightly weaker on
the left. Which of the following is the best first step in management of this
patient?
|
A. Ankle brachial index . B. Arterial Doppler study . C. Intravenous heparin infusion . D. Nerve conduction study . E.
Transthoracic echocardiogram . |
Answer : C
Explanation:
The
patient has the classic clinical presentation of acute arterial occlusion of
the left lower extremity (acute limb ischemia): pain, pallor, poikilothermia
(cool extremity), paresthesia, pulselessness, and paralysis (6 Ps ). This is
most likely due to thromboembolic occlusion from left atrial thrombus due to
atrial fibrillation (irregular heartbeat) in a patient with preexisting
peripheral vascular disease (multiple risk factors, intermittent claudication,
diminished pulses).
Patients
with suspected acute arterial occlusion leading to an immediately-threatened limb
(sensory loss, rest pain, muscle weakness) should be immediately started on anticoagulation
while further diagnostic procedures are performed. Heparin prevents further
thrombus propagation and thrombosis in the distal arterial and venous
circulation.
(Choice
A) Ankle-brachial index (ratio of systolic pressure in ankle to that in arm) is
often used as a screening and/or diagnostic tool in patients with suspected
peripheral arterial disease (PAD). Although this patient likely has PAD, the
more acute limb-threatening complication should be addressed first.
(Choice
B) Arterial Doppler study or duplex ultrasonography can identify the presence and
location of acute arterial occlusion; however, the clinical suspicion for acute
embolic occlusion in this patient is so high that anticoagulation initiation
should not be delayed while obtaining additional confirmatory testing.
(Choice
D) This patient's abnormal neurologic findings (eg, decreased sensation) are likely
the result of nerve ischemia. Therefore, nerve conduction studies would not add
much value.
(Choice
E) Transthoracic echocardiogram (TTE) can aid in identifying potential cardiac sources
of emboli (eg, left atrial thrombus due to atrial fibrillation, left
ventricular thrombus, infective endocarditis [septic emboli], thrombus from
prosthetic valves).
However,
TTE should be performed after the limb-threatening acute ischemia has been addressed.
Educational
objective:
Patients
with suspected acute arterial occlusion leading to an immediately-threatened limb
(eg, sensory loss, rest pain, muscle weakness) should be immediately started on
anticoagulation with intravenous heparin prior to further evaluation with
noninvasive or invasive imaging.
|
References: 1.
Inter-Society
Consensus for the Management of Peripheral Arterial Disease (TASC II). New
links : 1.
Inter-Society
Consensus for the Management of Peripheral Arterial Disease (TASC II). |
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