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Electrical alternans and cardiac electrical instability.

J M Smith1, E A Clancy, C R Valeri

  • 1Harvard-MIT Division of Health Sciences and Technology, Cambridge, MA 02139.

Circulation
|January 1, 1988
PubMed
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Analyzing electrocardiographic morphology variations, or electrical alternans, offers a new noninvasive method to assess cardiac electrical stability. This technique shows promise in identifying patients at risk for dangerous heart arrhythmias.

Area of Science:

  • Cardiology
  • Electrophysiology
  • Biomedical Engineering

Background:

  • Cardiac electrical stability is crucial for preventing life-threatening arrhythmias like ventricular fibrillation.
  • Current methods for assessing cardiac electrical stability can be invasive and carry risks.
  • Electrical alternans, a beat-to-beat variation in electrocardiogram (ECG) morphology, has been observed but its clinical utility in assessing electrical stability is not well-established.

Purpose of the Study:

  • To investigate the relationship between electrical alternans and cardiac electrical stability.
  • To evaluate the potential of a novel multidimensional spectral technique for quantifying electrical alternans.
  • To determine if electrical alternans can serve as a noninvasive marker for cardiac electrical instability.

Main Methods:

Related Experiment Videos

  • Developed and applied a novel multidimensional spectral technique to detect and quantify electrical alternans in the QRS complex and ST-T wave, termed the alternating electrocardiographic morphology index (AEMI).
  • Assessed cardiac electrical stability in 20 dog experiments using the ventricular fibrillation threshold (VFT) measurement, induced by systemic hypothermia or transient coronary artery ligation.
  • Conducted a double-blind pilot clinical trial with 19 patients, using electrophysiologic testing (programmed stimulation) as an independent measure of cardiac electrical stability.

Main Results:

  • In dog experiments, conditions that decreased VFT (indicating instability) significantly increased AEMI(QRS) and AEMI(ST-T) values (p < .0001).
  • Strong negative correlations were found between VFT and AEMI(QRS) (r = -0.30, p < .001) and VFT and AEMI(ST-T) (r = -0.55, p < .0001).
  • In the clinical study, electrical alternans identified patients with inducible arrhythmias with 92% sensitivity, 70% positive predictivity, and 50% specificity (p < .05).

Conclusions:

  • Analysis of subtle beat-to-beat variability in ECG morphology (electrical alternans) provides a noninvasive measure of cardiac electrical stability.
  • The novel spectral technique effectively quantifies electrical alternans, correlating with established measures of cardiac electrical stability.
  • Electrical alternans holds significant potential for noninvasive risk stratification of patients susceptible to cardiac arrhythmias.