U01.07.049 Cardiac tamponade

Cardiac tamponade occurs when fluid accumulates in the pericardial space, compressing the heart and impairing its ability to pump blood. This compression leads to decreased cardiac output (CO) and an equilibration of diastolic pressures across all four chambers of the heart.

Pathophysiology

Compression of the heart: Accumulation of fluid (such as blood or effusions) in the pericardial space leads to compression of the heart.
Impaired cardiac output (CO): As the heart is compressed, its ability to pump blood effectively decreases.
Equilibration of diastolic pressures: All four chambers of the heart reach equal diastolic pressure due to the increased pressure from the pericardial effusion.

Key Findings

Beck’s Triad:
- Hypotension: Decreased blood pressure due to reduced cardiac output.
- Distended neck veins: Jugular venous distension caused by impaired venous return.
- Distant heart sounds: Muffled heart sounds due to fluid surrounding the heart.
Pulsus Paradoxus: A decrease in the amplitude of systolic blood pressure by more than 10 mm Hg during inspiration. This is a hallmark of cardiac tamponade and can also be seen in conditions like:
- Constrictive pericarditis
- Obstructive pulmonary diseases (e.g., Croup, Obstructive Sleep Apnea (OSA), Asthma, COPD)
Increased Heart Rate (HR): The body compensates for reduced CO by increasing heart rate.

Diagnostic Findings

ECG: Characterized by:
- Low-voltage QRS complexes: Due to the dampening effect of the surrounding fluid.
- Electrical alternans: A pattern is seen when the heart swings back and forth within the effusion, causing alternating changes in the amplitude of the QRS complexes.

Clinical Signs and Symptoms of Cardiac Tamponade

Clinical Finding	Description
Hypotension	Low blood pressure due to reduced cardiac output.
Distended Neck Veins	Jugular venous distention due to impaired venous return.
Distant Heart Sounds	Muffled heart sounds due to the surrounding pericardial fluid.
Pulsus Paradoxus	A drop in systolic blood pressure by more than 10 mm Hg during inspiration.
Increased Heart Rate (HR)	Compensatory response to reduced cardiac output.
Low-voltage QRS	ECG finding due to the electrical dampening by pericardial fluid.
Electrical Alternans	Alternating QRS complex amplitudes due to heart swinging in the fluid.

Differential Diagnosis

Pulsus paradoxus is not exclusive to cardiac tamponade and can also be observed in:

Constrictive Pericarditis
Obstructive Pulmonary Diseases (Croup, OSA, Asthma, COPD)

The mnemonic “Pea COAT” can be used to remember conditions that feature pulsus paradoxus:

P: Pericarditis (Constrictive)
C: COPD
O: Obstructive sleep apnea (OSA)
A: Asthma
T: Tamponade (Cardiac)

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