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Related Experiment Videos

Electrocardiographic R-wave changes during cardiac surgery.

J B Mark1, G L Chien, R A Steinbrook

  • 1Department of Anesthesia, Harvard Medical School, Brigham and Women's Hospital, Boston, Massachusetts 02115.

Anesthesia and Analgesia
|January 1, 1992
PubMed
Summary

Intraoperative electrocardiogram (ECG) monitoring during cardiac surgery can be affected by sternal retractors. The Canadian sternal retractor significantly reduced R-wave amplitude and ST-segment deviation, impacting diagnostic accuracy.

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Area of Science:

  • Cardiology
  • Surgical Monitoring
  • Electrocardiography

Background:

  • Exercise electrocardiography accuracy is improved by R-wave gain factor correction for ST-segment changes.
  • Intraoperative myocardial ischemia diagnosis may benefit from similar gain factor correction if R-wave amplitude changes occur during cardiac operations.

Purpose of the Study:

  • To determine the frequency and magnitude of intraoperative V5 R-wave amplitude changes during cardiac operations.
  • To assess the impact of sternal retractors on ECG parameters and their correlation with myocardial ischemia indicators.

Main Methods:

  • ECG recordings from 83 patients were taken while awake, anesthetized (baseline), after Favaloro and Canadian sternal retractor placement, and at end-operation.
  • V5 R-wave and S-wave amplitudes, and absolute ST-segment deviation were measured and compared across different surgical stages.

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Main Results:

  • The Canadian sternal retractor significantly reduced V5 R-wave amplitude (15±1 to 10±1 mm) and ST-segment deviation (0.50±0.04 to 0.39±0.05 mm) compared to baseline.
  • Changes in V5 R-wave amplitude correlated with ST-segment deviation changes in patients with baseline deviations ≥0.5 mm (r=0.55, P=0.0004).
  • Significant V5 R-wave amplitude reduction persisted at end-operation (15±1 to 9±1 mm).

Conclusions:

  • Sternal spreading with the Canadian retractor causes marked reductions in V5 R- and S-wave amplitudes and ST-segment deviations.
  • These significant R-wave amplitude changes persist even after sternal closure, potentially affecting intraoperative diagnosis.