7.5 Pericardial & Acute Aortic Diseases

Pericardial and acute aortic disorders present with high-acuity chest pain and complex hemodynamic derangements. In MRCP(UK) Part 1, candidates are frequently tested on electrocardiographic discrimination between pericarditis and STEMI, hemodynamic differentiation between cardiac tamponade and constrictive pericarditis, and acute emergency management of Stanford Type A versus Type B aortic dissections.

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1. Acute Pericarditis

Aetiology

Acute pericarditis represents inflammation of the fibroserous pericardial sac. Primary causes include:

• Idiopathic / Viral (~80–90% of cases in developed nations): Enteroviruses (Coxsackievirus B, Echovirus), Adenovirus, Influenza, Epstein-Barr virus (EBV), Cytomegalovirus (CMV), Parvovirus B19, and SARS-CoV-2.
• Post-Myocardial Infarction:
  • Early Pericarditis (Peri-infarction pericarditis): Occurs 24–72 hours post-transmural STEMI due to direct transmural inflammatory extension; usually self-limiting.
  • Late Pericarditis (Dressler's Syndrome): Occurs 2–10 weeks post-MI; an autoimmune-mediated polyserositis characterized by fever, pleuritic chest pain, pericardial effusion, and elevated ESR/CRP.
• Uraemic Pericarditis: Occurs in patients with end-stage renal disease (ESRD) or severe acute kidney injury, typically when blood urea nitrogen exceeds 20–30 mmol/L. Characterized by fibrinous ("bread and butter") exudate; often causes minimal fever and a quiet rub due to thick adherence. Treatment requires urgent hemodialysis.
• Malignancy: Metastatic infiltration from bronchogenic carcinoma, breast carcinoma, lymphoma, leukaemia, or malignant melanoma.
• Connective Tissue & Autoimmune Diseases: Systemic lupus erythematosus (SLE), rheumatoid arthritis, systemic sclerosis, granulomatosis with polyangiitis.
• Infectious (Non-Viral): Mycobacterium tuberculosis (leading cause in sub-Saharan Africa and developing nations; strong tendency toward constrictive pericarditis), purulent bacterial (Staph aureus, Strep pneumoniae).

Clinical Features & Diagnosis

• Symptoms: Acute, sharp, retrosternal or precordial pleuritic chest pain. Pain characteristically radiates to the trapezius ridges (pathognomonic; mediated by the phrenic nerve C3–C5 which innervates both the fibrous pericardium and the adjacent diaphragmatic pleura). Pain is aggravated by lying supine, coughing, and deep inspiration, and is classically alleviated by sitting upright and leaning forward.
• Physical Examination: Pericardial friction rub (scratchy, superficial, high-pitched sound heard best with the stethoscope diaphragm at the lower left sternal border with the patient leaning forward in held expiration). Can have up to 3 phases per cardiac cycle (atrial systole, ventricular systole, rapid ventricular filling); highly specific, but transient and dynamic.
• 12-Lead Electrocardiogram Evolution:
  • Stage 1 (Acute Phase): Widespread, concave-upwards ("saddle-shaped") ST segment elevation across all limb and precordial leads (except aVR and V1). Concurrent PR segment depression in multiple leads. Reciprocal changes are limited strictly to lead aVR (and occasionally V1), which demonstrates ST segment depression and PR segment elevation.
  • High-Yield Differentiation from Acute STEMI: STEMI demonstrates convex-upward ("tombstone") localized ST elevation conforming to a specific coronary artery territory, prominent reciprocal ST depression in opposing vascular territories, pathological Q waves, and absence of PR segment depression.
  • Stage 2: Normalization of ST and PR segments (days later).
  • Stage 3: Widespread symmetrical T wave inversions.
  • Stage 4: Normalization of the ECG (weeks to months).

Pharmacotherapy Protocol

According to ESC guidelines, first-line medical therapy consists of:

1. High-Dose NSAIDs: Oral ibuprofen (600 mg every 8 hours) or high-dose aspirin (750–1000 mg every 8 hours) for 1–2 weeks, followed by gradual tapering after symptom resolution and CRP normalization. A proton pump inhibitor (PPI) must be co-prescribed for gastroprotection. (In post-MI Dressler syndrome, high-dose aspirin is preferred over other NSAIDs to avoid interfering with myocardial scar healing).
2. Adjuvant Weight-Adjusted Colchicine: Administered for 3 months (0.5 mg daily for patients <70 kg; 0.5 mg twice daily for patients >=70 kg). Multiple randomized trials (COPE, ICAP) demonstrate that adding colchicine significantly accelerates symptom resolution and cuts the recurrent pericarditis rate by >50%.
3. Corticosteroids: (e.g., oral prednisolone 0.25–0.5 mg/kg/day). Strictly reserved as second-line therapy for patients with contraindications/intolerance to NSAIDs, refractory symptoms, or specific autoimmune/systemic aetiologies. Systemic corticosteroids used during the initial acute viral episode are strongly associated with higher rates of chronicity and disease recurrence.

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2. Cardiac Tamponade vs Constrictive Pericarditis

Both conditions present with impaired diastolic filling of the ventricles, elevated systemic venous pressures, and low cardiac output, but their underlying pathophysiology, physical findings, and hemodynamic traces diverge fundamentally.

Cardiac Tamponade

Occurs when fluid accumulation within the non-compliant pericardial space raises intrapericardial pressure above intracardiac diastolic pressures, leading to external chamber compression and impaired filling throughout the entire cardiac cycle.

• Beck's Triad:
  1. Hypotension with narrow pulse pressure (due to reduced stroke volume).
  2. Elevated Jugular Venous Pressure (JVP) with absent/blunted y-descent.
  3. Muffled / Distant Heart Sounds (due to insulating fluid envelope).
• Pulsus Paradoxus: An exaggerated inspiratory drop in systemic systolic arterial blood pressure >10 mmHg during quiet spontaneous breathing. (Mechanism: During inspiration, increased venous return enlarges the right ventricle within the tight, non-distensible pericardial space, causing the interventricular septum to bulge leftward into the LV cavity, impairing LV filling and drastically reducing LV stroke volume).
• JVP Waveform: Shows a preserved or prominent systolic 'x' descent, but blunting or complete loss of the diastolic 'y' descent. Ventricular filling during early diastole is prevented because intracardiac diastolic pressure is lower than the elevated intrapericardial pressure.
• ECG & Echocardiography: Low-voltage QRS complexes; electrical alternans (beat-to-beat alternation of QRS axis and amplitude caused by the heart physically swinging like a pendulum within the massive pericardial effusion). Echocardiography confirms effusion, right atrial systolic collapse (early, sensitive), and right ventricular diastolic collapse (highly specific).
• Management: Emergency needle pericardiocentesis (subxiphoid approach under ultrasound guidance) or surgical pericardial window. Intravenous fluid boluses provide temporary hemodynamic bridge by elevating right atrial filling pressures.

Constrictive Pericarditis

Arises from chronic fibroelastic thickening, scarring, and calcification of the pericardium. While early diastolic filling is uninhibited, filling is abruptly halted in mid-to-late diastole when cardiac volume hits the rigid, non-compliant shell.

• Clinical Presentation: Chronic, progressive right-sided heart failure symptoms: peripheral pitting oedema, ascites, hepatomegaly, and fatigue out of proportion to dyspnoea.
• Kussmaul's Sign: A paradoxical rise (or failure of the normal fall) in JVP during inspiration. The rigid pericardium prevents transmission of negative intrathoracic inspiratory pressure to the heart; increased venous return cannot be accommodated by the right heart, backing up into the jugular veins.
• Auscultation: Pericardial Knock—a loud, high-pitched, early diastolic sound heard shortly after S2 (earlier than a normal S3), caused by the abrupt cessation of ventricular expansion.
• JVP Waveform: Prominent 'x' descent AND a steep, deep, and rapid 'y' descent (giving the JVP a classic "W" or "M" contour, also called Friedreich's sign).
• Diagnostic Imaging: Chest radiography (lateral view) and cardiac CT/MRI demonstrate pericardial calcification and thickening (>3–4 mm).
• Management: Complete surgical pericardiectomy ("pericardial stripping") is the definitive curative treatment.

Comparative Overview Table

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3. Acute Aortic Syndromes

Acute aortic syndromes represent a life-threatening spectrum of conditions affecting the aortic wall: Acute Aortic Dissection, Intramural Haematoma (IMH; haemorrhage within the media without intimal flap), and Penetrating Atherosclerotic Ulcer (PAU; atherosclerotic erosion through internal elastic lamina into the media).

Acute Aortic Dissection: Pathophysiology & Risk Factors

Initiated by a tear in the aortic intima, allowing systemic pressurized blood to surge into the media, separating the aortic layers and propagating longitudinally to create a true lumen and a false lumen.

• Major Risk Factors:
  • Systemic Hypertension: Present in 75–80% of patients; primary driver of mechanical shear stress.
  • Connective Tissue Disorders: Marfan syndrome (fibrillin-1 mutation, FBN1), Loeys-Dietz syndrome (TGFBR1/2), Vascular Ehlers-Danlos syndrome (Type IV, COL3A1), Turner syndrome.
  • Congenital Vascular Anomalies: Bicuspid aortic valve, coarctation of the aorta.
  • Preceding Aortic Pathology / Trauma: Tertiary syphilitic aortitis, pregnancy (third trimester), cocaine abuse, prior cardiac catheterization or sternotomy.

Clinical Presentation & Complications by Branch Involvement

• Pain Profile: Sudden, catastrophic "tearing", "ripping", or sharp chest pain, characteristically radiating to the back (interscapular region in descending dissection, anterior chest/neck in ascending dissection).
• Pulse & Blood Pressure Discrepancies: Asymmetric peripheral pulses or a difference in systolic blood pressure >20 mmHg between the arms (compression of the subclavian artery by the false lumen).
• Branch Malperfusion Complications:
  • Coronary Ostia: Proximal dissection can shear off the right coronary artery ostium, causing acute inferior STEMI (leads II, III, aVF). CRITICAL PITFALL: Administering thrombolysis to an aortic dissection masquerading as an inferior STEMI is universally fatal.
  • Aortic Valve Competence: Disruption of the aortic root suspension produces acute, severe aortic regurgitation (early diastolic murmur, acute pulmonary oedema).
  • Pericardium: Rupture into the pericardial reflection leads to hemopericardium and acute fatal cardiac tamponade.
  • Carotid / Innominate Arteries: Stroke, syncope, or altered consciousness.
  • Renal Arteries: Acute renal failure or malignant renovascular hypertension.
  • Mesenteric Vessels (Coeliac/SMA): Bowel ischaemia with severe metabolic acidosis.
  • Spinal Arteries (Artery of Adamkiewicz): Anterior spinal cord syndrome / paraplegia.
  • Iliac arteries: Acute lower limb ischaemia.

Stanford & DeBakey Classifications

Diagnostic Strategy

• CT Aortogram (Contrast-Enhanced Multi-Detector CT): First-line diagnostic gold standard in hemodynamically stable patients (sensitivity and specificity >98%). Demonstrates the intimal flap, distinguishes true from false lumina, and maps branch vessel malperfusion.
• Transoesophageal Echocardiography (TOE): Highly accurate; ideal for unstable patients in the resuscitation room or theatre, and accurately evaluates aortic regurgitation and tamponade.
• CXR: May demonstrate mediastinal widening (>8 cm), double aortic contour, or left-sided hemothorax; however, a normal CXR occurs in up to 15% and does NOT exclude dissection.

Medical & Surgical Management Protocol

1. Immediate Stabilization: Two large-bore IV cannulae, continuous arterial line monitoring (placed in the arm with the higher systolic pressure), high-flow oxygen, and urgent cross-match.
2. Targeted Medical Therapy (Anti-Impulse Therapy):
   • First-line: Intravenous Beta-Blockers: Administer IV labetalol (or esmolol infusion). The goal is to reduce both heart rate (<60 bpm) and blood pressure, minimizing the rate of change of aortic pressure over time (dP/dt), which drives dissection propagation.
   • Target Hemodynamics: Systolic blood pressure 100–120 mmHg and heart rate 50–60 bpm within 30 minutes.
   • Secondary Vasodilators: If systolic BP remains >120 mmHg despite adequate beta-blockade, add an IV vasodilator such as sodium nitroprusside or nicardipine. Rule: Never administer vasodilators alone without preceding beta-blockade, as reflex sympathetic tachycardia will increase dP/dt and accelerate dissection propagation.
3. Definitive Treatment:
   • Type A Dissection: Immediate emergency transfer to the cardiothoracic operating theatre for open surgical repair (mortality increases by 1–2% per hour if untreated in the first 48 hours).
   • Type B Dissection: Uncomplicated cases are managed medically in an intensive care setting with tight oral/IV antihypertensive therapy. Complicated Type B dissection (defined by intractable pain, rapid aortic expansion, rupture, or end-organ malperfusion of kidneys, limbs, or bowel) mandates Thoracic Endovascular Aortic Repair (TEVAR).