Cardiac Tamponade Signs and Echocardiographic Diagnosis
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Direct answer
Cardiac tamponade is compression of the heart by fluid in the pericardial space, raising intrapericardial pressure until diastolic filling falls and cardiac output drops. Its classic bedside signs are hypotension, raised venous pressure and muffled heart sounds, known as Beck triad, with pulsus paradoxus and electrical alternans supporting the diagnosis. Echocardiography confirms it, and urgent pericardiocentesis is the treatment.
What you must remember
- Beck triad: hypotension, raised jugular venous pressure and muffled heart sounds; the full triad is often absent in hypovolaemic patients.
- Pulsus paradoxus: an inspiratory fall in systolic pressure of more than about 10 mmHg; severe asthma and COPD are common mimics.
- ECG: low voltage QRS, sinus tachycardia and electrical alternans, where QRS amplitude alternates beat to beat.
- Echo: diastolic collapse of the right atrium or right ventricle, a plethoric inferior vena cava and large respiratory variation in mitral and tricuspid inflow; right ventricular diastolic collapse is widely regarded as the most specific sign.
- Causes: malignancy, uraemia, tuberculosis, post-infarction free wall rupture, cardiac surgery, aortic dissection and trauma.
- Definitive treatment: echo-guided pericardiocentesis, with a pericardial window for malignant or recurrent effusions.
- Temporising: volume loading, avoidance of positive pressure ventilation and vasodilators, and cautious inotropes until drainage is arranged.
Recognising a slow tamponade on the ward
A 52-year-old woman with breast cancer is admitted with breathlessness and a blood pressure that has drifted down over two days. Her neck veins are full, her heart sounds are faint, and her pulse varies with breathing.
- Recognise the triad: The clinician recognises the triad and checks for pulsus paradoxus with a sphygmomanometer, noting the fall in systolic pressure during inspiration. Malignant effusions accumulate slowly, so the pericardium stretches over days and a large effusion can be tolerated until a small increment tips her over.
- Obtain an ECG: It shows low voltage and possibly electrical alternans.
- Confirm on echo: Echocardiography confirms the effusion and shows whether the right heart collapses in diastole.
- Protect the circulation: Positive pressure ventilation is avoided and volume is given while pericardiocentesis is arranged, typically by the echo-guided subxiphoid or apical route.
- Send fluid and plan drainage: The fluid is sent for cytology, culture and biochemistry, because the cause shapes the long-term plan. A pericardial window may be needed if the effusion recurs.
Where the examiner tests the signs
Four traps recur with the signs of tamponade.
- Trap: trusting a normal venous pressure Correct: tamponade raises it, but hypovolaemia can flatten it, so a bleeding trauma patient may show tamponade physiology with an unremarkable neck.
- Trap: confusing tamponade with constriction Correct: both raise the JVP, but in tamponade the y descent disappears and the echo shows chamber collapse rather than a thickened pericardium.
- Trap: treating the pulsus paradoxus of asthma as tamponade Correct: asthma and COPD cause a similar inspiratory fall in systolic pressure, so the clinical context separates the two.
- Trap: treating every large effusion as tamponade Correct: slow accumulation is tolerated, whereas rapid accumulation of even a modest volume can be fatal.
Frequently asked questions
What is pulsus paradoxus and how is it measured?
Pulsus paradoxus is an inspiratory fall in systolic pressure of more than about 10 mmHg. It is measured by deflating a cuff slowly and noting the pressure at which sounds appear in expiration and later in inspiration. It is also seen in severe asthma.
Which echocardiographic sign is most specific for tamponade?
Right ventricular diastolic collapse is widely regarded as the most specific sign of tamponade, although right atrial collapse is also seen. Large respiratory variation in mitral and tricuspid inflow supports the diagnosis.
Why is positive pressure ventilation dangerous in tamponade?
Positive pressure ventilation raises intrathoracic pressure and reduces venous return to the right heart. This lowers preload and cardiac output in a patient whose filling is already compromised, so ventilation is kept as gentle as possible.
What is electrical alternans?
Electrical alternans is beat-to-beat alternation of QRS amplitude, caused by the heart swinging within a large effusion. It is a classic sign of tamponade, although it is not present in every patient.
How is a malignant pericardial effusion treated?
Echo-guided pericardiocentesis relieves acute tamponade, but a recurrent malignant effusion usually needs a subxiphoid pericardial window. Drainage addresses the immediate physiology, and the window reduces the chance of reaccumulation.