Pericardial Effusion and Pericardiocentesis
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Direct answer
Pericardial effusion is fluid in the pericardial sac, and it becomes an emergency when it accumulates quickly enough to cause cardiac tamponade, which impairs diastolic filling. Tamponade classically presents with Beck's triad of hypotension, raised venous pressure and muffled heart sounds, and echo shows right-sided diastolic collapse. Pericardiocentesis is indicated for haemodynamic compromise, whereas small effusions without compromise are usually observed.
What you must remember
- Tamponade physiology: raised intrapericardial pressure impairs diastolic filling, so cardiac output falls even though the ventricle itself is normal.
- Beck's triad: hypotension, raised jugular venous pressure and muffled heart sounds, though all three are present in only a minority of patients.
- Pulsus paradoxus: a fall in systolic pressure of more than 10 mmHg during inspiration, a classic clinical sign of tamponade.
- Electrical alternans: beat-to-beat variation in QRS amplitude from the swinging heart, with low voltage and sinus tachycardia on the ECG.
- Echo signs: right atrial or ventricular diastolic collapse, a plethoric inferior vena cava and exaggerated respiratory variation in mitral and tricuspid inflow.
- Haemorrhagic causes: malignancy, trauma, tuberculosis, uraemia and aortic dissection typically produce blood-stained or exudative fluid.
- Myxoedema: a large, serous effusion with high protein content, often tolerated well and rarely causing tamponade.
- Malignant effusion: lung, breast, lymphoma and melanoma are common sources, and cytology of the fluid confirms the cause.
Pericardiocentesis for tamponade, step by step
A 40-year-old woman with a history of lymphoma presents with hypotension, distended neck veins and muffled heart sounds after a week of breathlessness. The steps below set out how to drain the effusion and treat its cause.
- Confirm tamponade with echo: Echo shows the effusion and any right-sided diastolic collapse, and it guides the needle. Tamponade is a clinical diagnosis first, so do not delay drainage for a perfect scan if the patient is collapsing.
- Choose the approach: The subxiphoid route, with the needle at the left xiphocostal angle and directed towards the left shoulder, is the classic approach. Echo guidance is preferred when time allows.
- Aspirate in small volumes: Withdraw fluid slowly and stop if the patient develops ventricular ectopy or ST changes, since these suggest the needle is touching the myocardium.
- Leave a drain for large or recurrent effusions: A pericardial catheter is kept in place when the effusion is large or likely to recur, and fluid is sent for cell count, culture, cytology and adenosine deaminase.
- Treat the cause and monitor: Repeat echo after the procedure to check for re-accumulation, and treat the cause, for example antitubercular therapy for tuberculous effusion or a pericardial window for recurrent malignant effusion.
Where the examiner sets the traps
Pericardial effusion questions usually test whether you can separate observation from drainage.
- Trap: draining every effusion, including small asymptomatic ones Correct: small effusions without haemodynamic compromise are usually observed, while tamponade is the main indication for urgent drainage.
- Trap: expecting hypotension in every case of tamponade Correct: tachycardia with a narrow pulse pressure is common, and hypotension may appear late, so Beck's triad must be read alongside the clinical picture.
- Trap: treating tamponade with NSAIDs alone Correct: NSAIDs and colchicine suit uncomplicated viral or post-injury pericarditis, whereas tamponade needs urgent drainage.
Frequently asked questions
What is Beck's triad in cardiac tamponade?
Beck's triad in cardiac tamponade comprises hypotension, raised jugular venous pressure and muffled heart sounds. It reflects reduced cardiac output with venous congestion, but all three features are present in only a minority of patients, so echo is essential.
Which echo signs indicate cardiac tamponade?
Echo signs of cardiac tamponade include right atrial or right ventricular diastolic collapse, a plethoric inferior vena cava with reduced respiratory variation, and exaggerated respiratory variation in mitral and tricuspid inflow. These findings are most useful when they appear alongside a clinical picture of low output.
What is electrical alternans on an ECG?
Electrical alternans is a beat-to-beat variation in QRS amplitude caused by the heart swinging within a large pericardial effusion. It is most often seen with tamponade and suggests a large effusion, although its absence does not exclude one.
Where is pericardiocentesis usually performed for tamponade?
Pericardiocentesis for tamponade is usually performed through a subxiphoid approach, with the needle placed at the left xiphocostal angle and angled towards the left shoulder. Echo guidance is preferred when time allows, because it lowers the risk of puncturing the myocardium or a coronary artery.