What is the diagnosis and management for a patient with hypotension on inspiration, pericardial friction rub, and electrical alternans on electrocardiography (ECG)?

Cardiac Tamponade

This clinical triad—pulsus paradoxus (inspiratory blood pressure decrease >10 mmHg), pericardial friction rub, and electrical alternans on ECG—is diagnostic of cardiac tamponade requiring urgent echocardiography followed by immediate pericardiocentesis or surgical drainage. 1

Diagnosis

Clinical Presentation

The combination of these three findings represents a medical emergency:

• Pulsus paradoxus is the hallmark finding, defined as an inspiratory decrease in systolic arterial pressure >10 mmHg during normal breathing, caused by exaggerated ventricular interdependence when cardiac chamber volumes become fixed 1, 2
• Electrical alternans on ECG reflects the "swinging heart" motion within pericardial fluid, manifesting as alternating QRS amplitude 1, 2, 3
• Pericardial friction rub indicates pericardial inflammation, though this may disappear as fluid accumulates 1

Additional supporting features include:

• Tachycardia (usually >100 bpm) as a compensatory mechanism 1, 2
• Elevated jugular venous pressure from impaired right heart filling 1, 2
• Hypotension (though blood pressure may be maintained initially, especially with pre-existing hypertension) 1, 4
• Low QRS voltage on ECG due to fluid dampening effect 1, 2
• Enlarged cardiac silhouette on chest X-ray with clear lung fields 1, 2

Diagnostic Workup

Echocardiography is the single most important diagnostic test and must be performed immediately (Class I recommendation, Level C evidence) 1

Key echocardiographic findings include:

• Right ventricular diastolic collapse (highly specific) 1, 2, 5
• Right atrial systolic collapse (sensitive) 1, 2, 5
• Swinging heart motion corresponding to electrical alternans 1, 2, 3
• Inferior vena cava plethora without respiratory collapse 1, 2
• Exaggerated respiratory variation in mitral inflow velocity (>25%) 1
• Abnormal ventricular septal motion reflecting ventricular interdependence 1, 2

Management

Immediate Treatment

Urgent pericardiocentesis or cardiac surgery is mandatory (Class I recommendation, Level C evidence) 1

The treatment algorithm is:

1. Perform echocardiography-guided pericardiocentesis without delay in unstable patients 1

   • This is the preferred drainage method for most cases 1
   • Use echocardiographic or fluoroscopic guidance for safety 1

2. Choose surgical drainage instead for:

   • Purulent pericarditis 1
   • Bleeding into pericardium (hemopericardium) 1, 5
   • Type A aortic dissection with hemopericardium 5
   • Ventricular free wall rupture post-MI 5
   • Severe chest trauma 5

Critical Management Pitfalls

Avoid these interventions that worsen outcomes:

• Vasodilators and diuretics are contraindicated in cardiac tamponade (Class III recommendation) 1
• Positive-pressure ventilation should be avoided if possible, as it decreases cardiac output 5
• Intravenous sedation can precipitate cardiovascular collapse and should be minimized 5

Pre-Procedure Considerations

• Administer cautious intravenous fluids to hypotensive, hypovolemic patients to temporarily support preload 5
• Consider vasoactive medications for refractory hypotension 5
• Correct coagulopathy and anticoagulation before procedure when feasible 5
• Position patient to prevent hypoxia during procedure 5

Procedural Technique

• Target the largest, shallowest fluid pocket without intervening vital structures 5
• Use low-depth sonographic views for needle guidance 5
• Confirm catheter placement with agitated saline injection 5
• Drain fluid slowly to avoid pericardial decompression syndrome 5

Pathophysiology Context

This is a "last-drop phenomenon"—the pericardium's steep pressure-volume curve means the final fluid increment produces critical compression, while the first drainage increment produces maximal decompression 1, 2. The rate of fluid accumulation determines severity more than absolute volume; rapid accumulation of even small amounts can cause severe tamponade 2.