A 72-year-old woman comes to the physician for follow-up care. One year ago, she was diagnosed with a 3.8-cm infrarenal aortic aneurysm found incidentally on abdominal ultrasound. She has no complaints. She has hypertension, type 2 diabetes mellitus, and COPD. Current medications include hydrochlorothiazide, lisinopril, glyburide, and an albuterol inhaler. She has smoked a pack of cigarettes daily for 45 years. Her temperature is 37°C (98.6°F), pulse is 90/min, respirations are 12/min, and blood pressure is 145/85 mm Hg. Examination shows a faint abdominal bruit on auscultation. Ultrasonography of the abdomen shows a 4.9-cm saccular dilation of the infrarenal aorta. Which of the following is the most appropriate next step in management?

Elective endovascular aneurysm repair

Adjustment of cardiovascular risk factors and follow-up ultrasound in 12 months

Adjustment of cardiovascular risk factors and follow-up ultrasound in 6 months

Adjustment of cardiovascular risk factors and follow-up CT in 6 months

A previously healthy 4-year-old boy is brought to the physician by his parents because he has had a fever, diffuse joint pain, and a rash on his abdomen for the past week. Acetaminophen did not improve his symptoms. He emigrated from China with his family 2 years ago. He attends daycare. His immunization records are not available. His temperature is 38.5°C (101.3°F), pulse is 125/min, and blood pressure is 100/60 mm Hg. Examination shows polymorphous truncal rash. The eyes are pink with no exudate. The tongue is shiny and red, and the lips are cracked. The hands and feet are red and swollen. There is right-sided anterior cervical lymphadenopathy. Which of the following is the most appropriate next step in management?

HHV-6 immunoglobulin M (IgM) detection

Antistreptolysin O titer measurement

A 44-year-old woman comes to the physician because of progressively worsening shortness of breath with exertion and intermittent palpitations over the last 2 months. She has had neither chest pain nor a cough. Her pulse is 124/min and irregular. Physical examination shows a grade 4/6 high-pitched holosystolic murmur that is best heard at the apex and radiates to the back. The murmur increases in intensity when she clenches her hands into fists. The lungs are clear to auscultation. Further evaluation of this patient is most likely to show which of the following findings?

Dilation of left atrium on echocardiogram

Obstruction of the right marginal artery on coronary angiogram

Diffuse ST elevations on electrocardiogram

Reversible area of myocardial ischemia on nuclear stress test

Pulmonary artery thrombus on computed tomography scan

A 3-month-old male presents to the pediatrician with his mother for a well child visit. The patient drinks 4 ounces of conventional cow’s milk formula every three hours. He usually stools once per day, and urinates up to six times per day. His mother reports that he regurgitates a moderate amount of formula through his nose and mouth after most feeds. He does not seem interested in additional feeding after these episodes of regurgitation, and he has become progressively more irritable around meal times. The patient is starting to refuse some feeds. His mother denies ever seeing blood or streaks of red in his stool, and she denies any family history of food allergies or dermatological problems. The patient’s weight was in the 75th percentile for weight throughout the first month of life. Four weeks ago, he was in the 62nd percentile, and he is now in the 48th percentile. His height and head circumference have followed similar trends. On physical exam, the patient smiles reciprocally and can lift his head and chest when in the prone position. His abdomen is soft, non-tender, and non-distended. Which of the following is the best next step in management?

Counsel on positioning and thickening feeds

A 4-year-old boy is brought to a pediatrician by his parents with a history of fever for the last 5 days and irritability, decreased appetite, vomiting, and swelling of the hands and feet for the last 3 days. The patient’s mother mentions that he has been taking antibiotics and antipyretics prescribed by another physician for the last 3 days, but there has been no improvement His temperature is 39.4°C (103.0°F), pulse is 128/min, respiratory rate is 24/min, and blood pressure is 96/64 mm Hg. On physical examination, there is significant edema of the hands and feet bilaterally. There is a 2.5 cm diameter freely moveable, nontender cervical lymph node is palpable on the right side. A strawberry tongue and perianal erythema are noted. Conjunctival injection is present bilaterally. Laboratory findings reveal mild anemia and a leukocytosis with a left-shift. Erythrocyte sedimentation rate (ESR) and serum C-reactive protein (CRP) are increased. If not treated appropriately, this patient is at increased risk of developing which of the following complications?

Lower gastrointestinal hemorrhage

Acute disseminated encephalomyelitis (ADEM)

A 5-year-old girl presents with a rash and a persistent fever of 41.0°C (105.8°F), not relieved by Tylenol. The patient's mother says that her symptoms started 5 days ago and have not improved. The rash started on her trunk and now is present everywhere including the palms and soles. Her birth history is normal. Her pulse is 120/min and respiratory rate is 22/min. On physical examination, the patient is agitated and ill-appearing. There is significant swelling of the distal upper and lower extremities bilaterally. The pharynx is hyperemic (see image). Generalized edema with palpable cervical lymphadenopathy is noted. Muscle tone is normal. Remainder of exam is unremarkable. Laboratory findings are significant for the following: Laboratory test Hb 9 g/dL RBC 3.3/mm3 Neutrophilic leukocytosis 28,000/mm3 Normal platelet count 200,000/mm3 Serum ɣ-GT increased Hyperbilirubinemia 2.98 mg/dL AST and ALT are normal, but there is markedly increased serum CRP. Which of the following is the most likely diagnosis in this patient?

Staphylococcal scalded skin syndrome

Cardiac complications and evaluation for USMLE Step 1: High-Yield Pediatrics Lessons

Pathophysiology - Heart Under Fire

Immune-mediated vasculitis targeting medium-sized arteries, with a strong predilection for coronary arteries.
Involves infiltration of neutrophils, lymphocytes, and plasma cells, leading to destruction of the tunica media and internal elastic lamina.
This structural damage results in weakening of the vessel wall, predisposing to coronary artery aneurysms (CAA), thrombosis, and stenosis.
Myocarditis is also common in the acute phase.

⭐ The inflammatory process can lead to giant aneurysms (>8 mm), which have the highest risk of thrombosis.

Coronary artery vasculitis in Kawasaki disease

Coronary Artery Aneurysms (CAA) - Bulging Arteries

Most feared complication; necrotizing arteritis weakens the coronary artery wall, leading to dilation and aneurysm formation.
Risk: Untreated ≈ 25%; with timely IVIG, risk falls to <5%.
Classification (AHA guidelines): Based on internal lumen diameter z-scores (normalized for body surface area).
- Dilation: z-score 2 to <2.5
- Small Aneurysm: z-score ≥2.5 to <5
- Medium Aneurysm: z-score ≥5 to <10
- Large/Giant Aneurysm: z-score ≥10

⭐ Giant aneurysms (z-score ≥10 or absolute dimension >8 mm) carry the highest risk of thrombosis, stenosis, and subsequent myocardial infarction. Lifelong antiplatelet and anticoagulation therapy is often required.

Echocardiographic Evaluation - Heart Detective Work

Primary Goal: Detect coronary artery abnormalities (CAA), primarily aneurysms, and assess myocardial function.
Key Findings to Assess:
- Coronary Arteries: Dilatation, aneurysms (saccular/fusiform), thrombosis. Measured in LAD, RCA, LCx.
- Myocardium: ↓ Ejection fraction (myocarditis).
- Valves: Valvular regurgitation (mitral > aortic).
- Pericardium: Pericardial effusion.
Z-Scores (Body Surface Area-Adjusted):
- No dilatation: Z-score < 2
- Dilatation only: Z-score ≥ 2 to < 2.5
- Small aneurysm: Z-score ≥ 2.5 to < 5
- Medium aneurysm: Z-score ≥ 5 to < 10
- Large/Giant aneurysm: Z-score ≥ 10

⭐ Giant aneurysms (Z-score ≥ 10 or absolute dimension >8 mm) carry the highest risk of thrombosis and stenosis.

Echo Timing Algorithm:

Risk Stratification & Management - Clot Control Crew

Goal: Prevent coronary artery thrombosis based on aneurysm severity (Z-score).
Initial Therapy (All): Low-dose Aspirin (3-5 mg/kg/day) after fever subsides for 48h.

Echocardiogram: LMCA measurement and color Doppler flow

⭐ Giant Aneurysms (absolute diameter >8 mm or Z-score ≥10) carry the highest risk of thrombosis and myocardial infarction. Long-term anticoagulation is mandatory.

High‑Yield Points - ⚡ Biggest Takeaways

Coronary artery aneurysms (CAA) are the most feared complication of Kawasaki disease, potentially leading to thrombosis or stenosis.

2D-Echocardiography is the gold standard for diagnosis and monitoring, performed at baseline, 2 weeks, and 6-8 weeks after onset.

Myocarditis is the most common cardiac manifestation during the acute phase.

Giant aneurysms (>8 mm or Z-score ≥10) have the highest risk of thrombosis and subsequent myocardial infarction.

Delayed IVIG administration beyond day 10 of fever significantly ↑ risk of CAA.

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