In tamponade the heart cannot expand, so the two ventricles compete for space. With inspiration, filling shifts toward the right heart and away from the left. Doppler shows this as mitral inflow falling and tricuspid inflow rising with each breath.
By James Napolitano. Cutoffs from the guidelines cited below.
Start with the 2D findings
A pericardial effusion: dark fluid between the heart and the bright pericardium.
Right atrial collapse at end-diastole and RV collapse in early diastole.
A plethoric IVC with little respiratory change.
Live exampleFigure 1. Live apical 4-chamber view of a heart with a pericardial effusion. Note the dark fluid between the heart and the bright pericardium, right atrial collapse at end-diastole and RV collapse in early diastole. The PW gate moves to the mitral tips, then the tricuspid tips. Drag it yourself.
Record inflow variation
Apical 4-chamber view. Turn on the respirometer and slow the sweep to 25 to 50 mm/s so several breaths fit on screen.
Place a PW gate at the mitral leaflet tips. Measure the tallest and shortest E wave across one breath.
Move the gate to the tricuspid leaflet tips and repeat.
Variation = (maximum E − minimum E) / maximum E
Calculator
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Live exampleFigure 2. Live mitral and tricuspid inflow on a slow sweep with a respirometer trace. Measure the tallest and shortest E across one breath.
Tap a trace to freeze and measure.
Stroke volume
Apical 5-chamber
Angle to flow --
What the gate records
Move the gate and watch the trace change.
How to read it
An inspiratory fall in mitral E of about 30% is considered diagnostic in research studies, and should be read together with chamber collapse, a plethoric IVC and hepatic vein flow rather than alone.1 Some emergency medicine teaching uses lower cutoffs, 25% mitral and 40% tricuspid, to favor sensitivity.
Caveats
Mitral E falls and tricuspid E rises with inspiration in spontaneous breathing. Positive pressure ventilation changes the pattern.
Exaggerated variation also occurs with severe COPD or asthma, large respiratory swings and constrictive physiology.
Tamponade is a clinical diagnosis. Doppler supports it.
Practice this on live Doppler.Critical Care Echo Trainer has all five measurements: stroke volume, RVSP, diastolic function, tamponade and TAPSE. Random cases with an answer key, and the full Acquire view with probe position and technique for each. $59, one-time.
Klein AL, et al. American Society of Echocardiography clinical recommendations for multimodality cardiovascular imaging of patients with pericardial disease. J Am Soc Echocardiogr. 2013;26:965-1012.