# Clinical Cases: Cardiac Anatomy and Histology

## Case 1: Acute Pericarditis with Pericardial Effusion

### Patient Presentation
**Demographics:** 32-year-old male

**Chief Complaint:** Sharp chest pain for 2 days

**History of Present Illness:**
A 32-year-old previously healthy male presents with sharp, stabbing chest pain that started 2 days ago. The pain is worse when lying flat and improves when sitting forward. He reports a recent viral upper respiratory infection 1 week ago. He also notes low-grade fever and fatigue.

**Physical Examination:**
- Vital Signs: BP 118/72 mmHg, HR 98 bpm, RR 18/min, Temp 38.1°C, SpO2 98% on room air
- General: Anxious-appearing male, sitting forward
- Cardiovascular: Pericardial friction rub heard at left lower sternal border (three-component scratchy sound)
- Lungs: Clear to auscultation bilaterally
- JVP: Normal

### Workup
- **ECG:** Diffuse ST-segment elevation with PR depression in multiple leads (concave upward ST elevation)
- **Echocardiogram:** Small pericardial effusion (0.8 cm), normal LV function
- **Labs:**
  - Troponin I: 0.08 ng/mL (mildly elevated)
  - WBC: 11,200/μL
  - ESR: 45 mm/hr
  - CRP: 6.2 mg/dL

### Diagnosis
**Acute viral pericarditis with small pericardial effusion and mild myopericarditis**

*Anatomical Correlation:* The pericardium consists of the fibrous pericardium (outer layer) and serous pericardium (parietal and visceral layers). The pericardial cavity normally contains 15-50 mL of fluid. Inflammation of the pericardium causes the characteristic friction rub heard when roughened pericardial surfaces rub together.

### Treatment
1. NSAIDs (Ibuprofen 600 mg TID for 1-2 weeks)
2. Colchicine 0.5 mg BID for 3 months (reduces recurrence)
3. Activity restriction until symptoms resolve
4. Serial echocardiography to monitor effusion

### Clinical Image
![Pericardial Effusion on Echocardiogram](case_01_image.jpg)

**Image Description:** Echocardiogram showing pericardial effusion as an echo-free space surrounding the heart. The pericardial fluid appears as a dark (anechoic) space between the visceral and parietal pericardium.

**Source:** Wikimedia Commons - Echocardiography of pericardial effusion
**License:** CC BY-SA 4.0
**URL:** https://commons.wikimedia.org/wiki/File:Pericardial_effusion_with_tamponade.gif

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## Case 2: Right Coronary Artery Occlusion with Inferior MI

### Patient Presentation
**Demographics:** 58-year-old male

**Chief Complaint:** Crushing chest pain and nausea for 1 hour

**History of Present Illness:**
A 58-year-old male with history of hypertension and smoking presents with sudden onset crushing substernal chest pain radiating to his jaw and left arm. He also reports nausea, diaphoresis, and lightheadedness. Symptoms began 1 hour ago while watching television.

**Physical Examination:**
- Vital Signs: BP 92/60 mmHg, HR 48 bpm, RR 22/min, SpO2 94% on room air
- General: Diaphoretic, pale, anxious
- Cardiovascular: Bradycardic, regular rhythm, S4 gallop, JVP elevated to 12 cm
- Lungs: Clear bilaterally

### Workup
- **ECG:** ST-segment elevation in leads II, III, aVF (inferior leads); ST depression in I, aVL (reciprocal changes); Sinus bradycardia at 48 bpm
- **Echocardiogram:** Inferior and posterior wall hypokinesis, RV dilation with reduced function
- **Labs:**
  - Troponin I: 8.5 ng/mL (markedly elevated)
  - CK-MB: 85 ng/mL

### Diagnosis
**Acute inferior STEMI due to right coronary artery (RCA) occlusion with right ventricular involvement**

*Anatomical Correlation:* The right coronary artery supplies the inferior wall of the left ventricle (via posterior descending artery in right-dominant circulation), the right ventricle, and importantly the SA node (in 60% of people) and AV node (in 90% of people). This explains the bradycardia and hypotension seen with RCA occlusion. The RCA originates from the right aortic sinus.

### Treatment
1. Emergent cardiac catheterization with PCI to RCA
2. IV fluids (avoid diuretics and nitrates due to RV involvement)
3. Atropine for symptomatic bradycardia
4. Aspirin 325 mg, P2Y12 inhibitor, heparin
5. Temporary pacing if needed for high-grade AV block

### Clinical Image
![Inferior STEMI ECG](case_02_image.jpg)

**Image Description:** 12-lead ECG demonstrating ST-segment elevation in inferior leads (II, III, aVF) consistent with acute inferior myocardial infarction. Reciprocal ST depression is visible in lateral leads.

**Source:** Wikimedia Commons - ECG showing inferior STEMI
**License:** CC BY-SA 3.0
**URL:** https://commons.wikimedia.org/wiki/File:AMI_inferior.png

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## Case 3: Atrial Septal Defect Discovered in Adult

### Patient Presentation
**Demographics:** 35-year-old female

**Chief Complaint:** Palpitations and exercise intolerance

**History of Present Illness:**
A 35-year-old female presents with a 2-year history of progressive exercise intolerance and palpitations. She notes becoming short of breath when climbing stairs and during aerobic exercise. She has had occasional episodes of rapid heartbeat. She has no prior cardiac history and was previously athletic.

**Physical Examination:**
- Vital Signs: BP 115/70 mmHg, HR 85 bpm (irregular), RR 16/min, SpO2 97% on room air
- General: Thin female in no acute distress
- Cardiovascular:
  - Fixed split S2 (does not vary with respiration)
  - Grade 2/6 systolic ejection murmur at left upper sternal border (pulmonary flow murmur)
  - RV heave palpable
- Lungs: Clear

### Workup
- **ECG:** Right axis deviation, incomplete RBBB pattern, atrial fibrillation
- **Chest X-ray:** Enlarged right atrium and right ventricle, prominent pulmonary arteries
- **Echocardiogram:**
  - Secundum ASD (2.2 cm) with left-to-right shunt
  - Dilated right atrium and right ventricle
  - Qp:Qs ratio 2.5:1
  - Estimated PA systolic pressure 45 mmHg

### Diagnosis
**Secundum atrial septal defect with right heart volume overload and secondary atrial fibrillation**

*Anatomical Correlation:* The interatrial septum develops from the septum primum and septum secundum. The foramen ovale is formed between these structures. A secundum ASD occurs due to excessive resorption of septum primum or inadequate development of septum secundum, resulting in a defect in the fossa ovalis region. The left-to-right shunt causes chronic RV volume overload leading to chamber dilation.

### Treatment
1. Rate control for atrial fibrillation (beta-blocker)
2. Anticoagulation for atrial fibrillation
3. Percutaneous transcatheter ASD closure (suitable for secundum defects with adequate rims)
4. Post-closure monitoring for resolution of RV dilation

### Clinical Image
![Atrial Septal Defect Echocardiogram](case_03_image.jpg)

**Image Description:** Echocardiogram (subcostal view) demonstrating an atrial septal defect with color Doppler showing left-to-right shunt flow across the interatrial septum from left atrium to right atrium.

**Source:** Radiopaedia - Atrial septal defect
**License:** CC BY-NC-SA 3.0
**URL:** https://radiopaedia.org/cases/atrial-septal-defect-asd-secundum