Definition

  Beat to beat alternating amplitudes or the configuration of the P, QRS and/or T waves.

 
QRS alternans is the most common among them.

  If P, QRS and T waves are all involved, it is called as
total alternans.

 
ST segment alternans may also be observed during myocardial ischemia.



Causes of electrical alternans

  Massive pericardial effusion.

  Myocardial failure.

  Narrow QRS tachycardia (independent of the tachycardia mechanism).

  Myocardial ischemia.

  ST segment alternans has been reported in association with the Brugada pattern.



Links to similar ECGs

  Am J Crit Care 2012;21:365-366



References

  Ann Intern Med, 1974; 814: 51-54.

  J Am Coll Cardiol 1987;9:489-499.

  Cardiovasc J Afr 2013 Mar 23;24(2):e1-3. doi: 10.5830/CVJA-2012-065.





ECG 1. QRS
aLtE rNaNc E is seen in a patient with pericarditis and pericardial effusion.

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ECG 2. QRS alternance in a patient with pericarditis and massive pericardial effusion.

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ECG 3. This ECG is from a patient with pericardial effusion. QRS amplitude
increases and decreases : QRS alternance.

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ECG 4. The above ECG shows T wave alternans in a patient with long QT syndrome.

Pediatric cardiologist Prof. Dr. Birgul Varan has donated the above ECG to our website.

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ECG 5a. The ECG above is from a middle-aged hypertensive man and was recorded during retrosternal chest pain.
He was diagnosed as having unstable angina pectoris and coronary angiography was performed immediately after this ECG.
QRS amplitude is changing during myocardial ischemia.
Also, inferior leads and the V6 show T wave negativity, and the lead V5 shows T wave flattening.
According to Gubner criteria, this ECG is compatible with left ventricular hypertrophy.

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ECG 5b. Two hours later, ECG was recorded again. This time, the patient had no chest pain.
No angina, no QRS alternance.
T wave negativity in inferior leads persist.
Now the T wave in lead V5 is upright and the negative T wave in lead V6 has disappeared.

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ECG 5c. Next day, another ECG was recorded during angina pectoris (above).
QRS amplitude is changing again due to myocardial ischemia.
Now many leads show ST segment depression while leads V1 and aVR show ST segment elevation.

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ECG 5d. On the same day with ECG 6c, another ECG was recorded but now the patient does not have chest pain.
No ischemia, no QRS alternance.

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