Cardiac tamponade
A clinical diagnosis that echo supports: collapse, interdependence, plethora — and where to put the needle.
Numbers to remember
- RA systolic collapse lasting >⅓ of systole — sensitive and specific [24]
- RV early-diastolic collapse — specific, less sensitive [24,31]
- Mitral E fall >25–30% and tricuspid E rise >40–60% with inspiration [24,31]
- Plethoric IVC (>21 mm, <50% collapse) — sensitive but not specific [3,24]
Questions echo must answer
Tamponade is a clinical and haemodynamic diagnosis: hypotension, tachycardia, raised JVP and pulsus paradoxus. Echo is the key supporting test [31,149]. The mechanism is ventricular interdependence: the fixed pericardial volume forces the right and left heart to fill at each other's expense with respiration.
- Is there fluid?Size and distribution (see Pericardial effusion).
- Chamber collapseRA systolic, RV diastolic, and LA or LV in loculated effusions.
- InterdependenceRespiratory variation in mitral and tricuspid inflow; septal shift.
- Venous congestionIVC plethora, hepatic vein expiratory diastolic reversal.
- Guide drainageBest entry site, depth, and confirmation of needle position with agitated saline [149].
Acquisition protocol
- Subcostal 4CThis is usually the first view, and often the best in the unstable patient. Assess RV free wall motion in early diastole and fluid depth.
- Subcostal IVCMeasure the diameter and inspiratory collapse [3,50].
- A4CRA inversion; time its duration against systole with slow-motion loops.
- PLAX with M-modeRV free-wall early-diastolic collapse.
- PW mitral / tricuspid inflowUse low sweep speed (25–50 mm/s) and a respirometer if available. Measure the maximal E variation [24].
- Hepatic veinsDiastolic flow reversal in expiration.
- Drainage planningMeasure the shortest distance to fluid (subcostal or apical) and check for liver or lung in the path.
- Effusion size
- RA collapse duration
- RV diastolic collapse
- Mitral E variation (%)
- Tricuspid E variation (%)
- IVC diameter and collapse
- Hepatic vein reversal
- Drainage site and depth
Diagnosis & severity
| Sign | Sensitivity / specificity | Notes |
|---|---|---|
| RA systolic collapse >⅓ of systole | High / high | Short collapse is common without tamponade [24] |
| RV early-diastolic collapse | Moderate / high | Absent if RV pressure or wall thickness is high (PH, RVH) [24,31] |
| Mitral inflow E fall with inspiration | >25–30% | Echo equivalent of pulsus paradoxus [24] |
| Tricuspid inflow E rise with inspiration | >40–60% | [24] |
| Plethoric IVC | Very sensitive / low specificity | A normal-sized, collapsing IVC makes tamponade unlikely [3,24] |
| Swinging heart | Specific for large effusions | Electrical alternans |
PitfallPositive-pressure ventilation inverts the respiratory pattern. Inflow variation is unreliable in ventilated patients, and intubation can precipitate arrest by reducing venous return [149].
Thresholds that change management
- Clinical tamponade with supportive echo → urgent drainage, by echo-guided pericardiocentesis or surgery [31,149].
- Haemopericardium from type A dissection, free-wall rupture or trauma → surgery. Needle drainage only as a bridge in extremis [9,31,138].
- Low-pressure tamponade (hypovolaemia, dialysis) → fluid can be temporising, and drainage is still needed [31].
- Before drainage: avoid intubation and positive-pressure ventilation where possible; give volume if hypovolaemic; do not give diuretics or vasodilators [149].
- After drainage: repeat echo to confirm resolution and look for re-accumulation and effusive-constrictive physiology [31].
Pitfalls & mimics
PitfallRegional tamponade after cardiac surgery can compress only the RA or LA or LV and have none of the classic signs. Suspect it in any post-operative low output. TOE is often needed [24].
- PH, RV hypertrophy or a severely raised RV diastolic pressure prevents RV collapse, so tamponade can occur without it. The left heart may collapse instead.
- Respiratory variation is also seen in COPD, asthma, obesity, hypovolaemia, PE and constriction.
- A plethoric IVC has many causes (RV failure, TR, constriction). It is a rule-out sign, not a rule-in sign.
- Arrhythmia (AF) makes the Doppler variation hard to interpret.