Electrical Alternans

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Contents 1 Introduction 2 More General Terms 3 Additional Terms 4 References

Introduction

• A beat to beat alteration in the electrocardiogram.

• Total electrical alternans involving the p-wave, the QRS complex, the ST segment & the T-wave with sinus tachycardia is a relatively specific sign of pericardial effusion, often with pericardial tamponade. This occurs from a periodic swing of the heart in the effusion at a frequency of 1/2 the heart rate.
• ST-T electrical alternans is a sign of electrical instability & may signal impending ventricular fibrillation.

More General Terms

• cardiology

Additional Terms

• electrocardiogram (ECG, EKG)
• pericardial effusion
• ventricular fibrillation (V Fib)

References

Harrison's Principles of Internal Medicine, 14th ed.  Fauci et al (eds), McGraw-Hill Inc. NY, 1998, pg 1246

electrical alternans