Electrical Alternans Workup

Updated: Feb 27, 2014
  • Author: Eric Gorgon Shaw, MD, FACEP, FAAEM, FAWM; Chief Editor: Jeffrey N Rottman, MD  more...
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Workup

Laboratory Studies

Direct laboratory investigations toward discovery of the primary underlying etiology of electrical alternans. Based on other clinical information, appropriate lab studies include cardiac enzymes for myocardial ischemia and infarction as well as serum calcium, potassium, and magnesium if electrolyte abnormalities are suspected. In the setting of a large pericardial effusion, laboratory studies searching for a malignancy may be warranted.

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Imaging Studies

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  • Chest radiography
    • Chest radiograph may reveal an enlarged cardiac silhouette, possibly indicating cardiomyopathy or large pericardial effusion.
    • Evidence of the Westermark sign or Hampton hump may suggest pulmonary embolism as the cause of electrical alternans.
  • Echocardiography
    • Echocardiography should be performed on those patients with total electrical alternans (P, QRS, and T wave) to evaluate for pericardial effusion.
    • Echocardiography is also necessary for evaluation of patients with hypertrophic cardiomyopathy, alcoholic cardiomyopathy, or congestive heart failure.
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Other Tests

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  • Electrocardiogram
    • ECG is the main study through which electrical alternans is discovered. Any or all components of the electrical waveforms may exhibit alternans (see following images).
      Typical alternate-beat QRS electrical alternans. N Typical alternate-beat QRS electrical alternans. Note that QRS voltage is low.
      Supraventricular tachycardia with alternans. Note Supraventricular tachycardia with alternans. Note the phasic nature to the QRS morphology, particularly in the rhythm strip in V1.
    • High-resolution ECG with spectral analysis can detect alternans in the microvolt range of amplitude. This detailed study is appropriate when searching for T-wave alternans as a predictor of ventricular tachyarrhythmia events. [12]
    • Routine ambulatory ECG monitoring of T-wave alternans, using dynamic, nonspectral, modified moving average analysis, may be helpful for risk stratification for arrhythmias.
    • T-wave alternans may be seen best in lead V 2 .
    • T-wave alternans can be detected by use of implantable cardioverter-defibrillators (ICDs). [13]
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Procedures

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  • Electrical alternans due to a large pericardial effusion should resolve completely after the effusion is drained. Pericardiocentesis must be performed emergently in the setting of cardiac tamponade.
  • In selected cases, cardiac catheterization may be indicated to further evaluate those patients with suspected vasospastic or nonvasospastic angina pectoris.
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