Canis ISSN: 2398-2942

ECG: principles of interpretation

Contributor(s): Lisa Moore, Jill Sammarco, Simon Swift

Introduction

  • The interpretation should be based on a good ECG recording ECG: overview.
  • Four features should be examined on every ECG:
    • Heart rate.
    • Heart rhythm.
    • Complexes, dimensions and intervals.
    • Mean electrical axis (MEA).
  • The largest positive (upward) deflections are usually the R waves.
  • The Q and S waves are usually negative waves immediately preceding or following the R wave respectively.
  • Q and S waves may not always be present in normal individuals.
  • The T wave is the deflection following the S or R waves after a short pause.
  • The P wave preceeds the Q wave and is usually positive ECG sinus rhythm.

Heart rate

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Heart rhythm

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General inspection

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Measure complexes and intervals

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Conclusion

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Further Reading

Publications

Refereed papers

  • Recent references from PubMed and VetMedResource.
  • Detweiler D K (1989) Comprehensive electrocardiography, total theory and practice in health and disease. Peter MacFarlane & Lawrie T D (eds) 1st edn. Pergamon Press, NY. pp 1267-1329. (This paper is backed by research and examination of 1000s of normal dogs.)

Other sources of information

  • Kittleson M D (1998) Electrocardiography - Basic Concepts, Diagnosis of Chamber Enlargement and Intraventricular Conduction Disturbances. In: Small Animal Cardiovascular MedicineEds. M D Kittleson and R D Kienle, Mosby.
  • Tilley L P (1992) Essentials of Canine and Feline Electrocardiography - Interpretation and Treatment. Lea and Febiger.


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