A 36-year-old woman presents to the emergency department with chest discomfort and fatigue. She reports that her symptoms began approximately 1 week ago and are associated with shortness of breath, swelling of her legs, and worsening weakness. She’s been having transitory fevers for about 1 month and denies having similar symptoms in the past. Medical history is significant for systemic lupus erythematosus (SLE) treated with hydroxychloroquine. She had a SLE flare approximately 2 weeks prior to presentation, requiring a short course of prednisone. Physical exam was significant for a pericardial friction rub. An electrocardiogram showed widespread ST-segment elevation and PR depression. After extensive work-up, she was admitted for further evaluation, treatment, and observation. Approximately 2 days after admission she became unresponsive. Her temperature is 100°F (37.8°C), blood pressure is 75/52 mmHg, pulse is 120/min, and respirations are 22/min. Heart sounds are muffled. Which of the following is a clinical finding that will most likely be found in this patient?

Decreased systolic blood pressure by 8 mmHg with inspiration

Unequal blood pressure measurements between both arms

A 42-year-old woman presents with complaints of a sharp, stabbing pain in her chest upon coughing and inhalation. She says that the pain started acutely 2 days ago and has progressively worsened. Her past medical history is significant for a rash on her face, joint pains, and fatigue for the past few weeks. The patient is afebrile and her vital signs are within normal limits. On physical examination, there is a malar macular rash that spares the nasolabial folds. There is a friction rub at the cardiac apex that does not vary with respiration. Which of the following additional physical examination signs would most likely be present in this patient?

Chest pain that improves with leaning forward

Pain improvement with inspiration

A 41-year-old woman presents to the emergency room with chest pain. She has had progressive substernal chest pain accompanied by weakness and mild shortness of breath for the past 2 hours. Her past medical history is notable for poorly controlled systemic lupus erythematosus (SLE), Sjogren syndrome, and interstitial lung disease. She was hospitalized last year with pericarditis presumed to be from SLE. Her temperature is 98.6°F (37°C), blood pressure is 106/56 mmHg, pulse is 132/min, and respirations are 26/min. On exam, the skin overlying the internal jugular vein fills at 9 cm above the sternal angle and distant heart sounds are appreciated. There is no friction rub. She is given 1000cc of intravenous fluids with no appreciable change in her blood pressure. An electrocardiogram in this patient would most likely reveal which of the following findings?

ST elevations in leads II, III, and aVF

Wide QRS complexes with no P waves

A 73-year-old man with coronary artery disease and hypertension is brought to the emergency department by ambulance 90 minutes after the acute onset of substernal chest pain and dyspnea. He has smoked 2 packs of cigarettes daily for 52 years. Shortly after arriving at the hospital, he loses consciousness and is pulseless. Despite attempts at cardiopulmonary resuscitation, he dies. Examination of the heart at autopsy shows complete occlusion of the left anterior descending artery with a red thrombus overlying a necrotic plaque. Which of the following pathophysiologic mechanisms is most likely responsible for this patient's acute coronary condition?

Secretion of matrix metalloproteinases

Influx of lipids into the endothelium

Release of platelet-derived growth factor

Proliferation of smooth muscle cells

A 51-year-old woman with hyperlipidemia comes to the physician because of weakness for one month. At the end of the day, she feels too fatigued to cook dinner or carry a laundry basket up the stairs. She also complains of double vision after she reads for long periods of time. All of her symptoms improve with rest. Her only medication is pravastatin. Physical examination shows drooping of the upper eyelids. Strength is initially 5/5 in the upper and lower extremities but decreases to 4/5 after a few minutes of sustained resistance. Sensation to light touch is intact and deep tendon reflexes are normal. Which of the following best describes the pathogenesis of this patient's condition?

Type II hypersensitivity reaction

Pericardial diseases for USMLE Step 1: High-Yield Pathology Lessons

Acute Pericarditis - Sac on Fire

Etiology: Most commonly idiopathic (presumed viral). Other causes include autoimmune disease (e.g., SLE), uremia, post-myocardial infarction (Dressler syndrome), and trauma.
Clinical Presentation:
- Chest Pain: Sudden, sharp, pleuritic, and retrosternal. Classically improves with sitting up and leaning forward, worsens when supine.
- Pericardial Friction Rub: High-pitched, scratching, or grating sound best heard at the left sternal border.
ECG Findings:
- Diffuse, concave ST-segment elevation across multiple leads.
- PR-segment depression (highly specific).

⭐ Exam Favorite: Unlike the localized ST elevation seen in myocardial infarction, the ST elevation in acute pericarditis is diffuse, involving nearly all leads except aVR and V1.

Treatment: NSAIDs (e.g., ibuprofen, indomethacin) and colchicine are first-line. Corticosteroids are reserved for refractory or autoimmune cases.

Pericardial Effusion & Tamponade - Water Torture

Pericardial Effusion: Excess fluid in the pericardial sac. Can be serous, serosanguinous, or purulent.
Etiologies: Idiopathic (viral), infection (TB), malignancy, uremia, autoimmune, post-MI (Dressler syndrome).
Cardiac Tamponade: Effusion that impairs cardiac filling, leading to ↓ cardiac output & shock. The rate of fluid accumulation is more critical than the volume.

Clinical Presentation (Tamponade):
- Beck's Triad (📌 Big Effusion Compresses K): BP low (Hypotension), Elevated JVP, Cannot hear heart (Muffled sounds).
- Pulsus Paradoxus: Inspiratory SBP drop >10 mmHg.
- Tachycardia, dyspnea, shock.
Diagnostics:
- ECG: Low-voltage QRS, electrical alternans (swinging heart).
- CXR: Globular, "water-bottle" heart silhouette.

Echocardiogram: Pericardial Effusion & Cardiac Tamponade

⭐ Echocardiography is the gold standard, revealing effusion size and diastolic collapse of the right atrium/ventricle-the most specific sign of tamponade.

Management: Urgent pericardiocentesis or pericardial window.

Constrictive Pericarditis - The Unyielding Cage

Pathophysiology: A thickened, fibrotic, and often calcified pericardium encases the heart, severely limiting diastolic filling. This leads to fixed cardiac output and signs of right-sided heart failure.
Etiologies: Most commonly idiopathic or post-viral. Can also result from cardiac surgery, radiation therapy, or tuberculosis.
Clinical Signs:
- Kussmaul's sign: Paradoxical ↑ in JVP on inspiration.
- Pericardial knock: An early, high-pitched diastolic sound.
- Prominent y descent (Friedreich's sign) in JVP.

Chest X-ray with sternal wires, no pericardial calcification

⭐ Hemodynamic Hallmark: Equalization of diastolic pressures in all four cardiac chambers, producing the characteristic "square root sign" or "dip-and-plateau" waveform on right heart catheterization.

Management: Definitive treatment is surgical pericardiectomy.

Acute pericarditis presents with pleuritic chest pain relieved by leaning forward, a pathognomonic friction rub, and diffuse ST-segment elevation.

Cardiac tamponade is a medical emergency characterized by Beck's triad (hypotension, JVD, muffled heart sounds) and pulsus paradoxus.

Constrictive pericarditis shows a pericardial knock on auscultation and Kussmaul's sign (paradoxical rise in JVP with inspiration).

Dressler syndrome is a delayed form of pericarditis occurring weeks to months after a myocardial infarction.

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