True Alternans in Cardiac Tamponade

Report:

Sinus tachycardia 126 - 132/min

Electrical alternans

Comment:

By definition, there must be no change in rhythm or conduction for alternans to be diagnosed. In this case, the mechanism is the "swinging" of the heart, pendulum-like, within the pericardial sac. There is no equivalent pulsus alternans, but the heart sounds may alternate in intensity.

The 12-lead ECG, of poor quality often associated with distressed patients, is shown below (Fig 270a). Apart from the alternans, it is a good example of absolute small voltage.

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