- Sinus tachycardia
- Low QRS voltages — Multiple limb lead QRS complexes < 5 mm in amplitude.
- Electrical alternans — There is a beat-to-beat variation in the QRS complex height. Taller complexes alternate with shorter ones.
The triad of tachycardia, low QRS voltages and electrical alternans is extremely suspicious for massive pericardial effusion.
Given the clinical history, I would be concerned about the presence of a malignant pericardial effusion causing tamponade. The diagnosis can be rapidly confirmed on bedside echo (watch these videos from The Ultrasound Podcast to learn how: Part 1, Part 2). There may also be clinical evidence of pulsus paradoxus.
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