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THE MORNING REPORT

The Best in FOAM Education

  • John Coacci, DO

Review of EKG Interpretation


Basics of Interpretation

  • Limb leads


  • Precordial leads


  • Atrial and ventricular depolarization and contraction in relation to the EKG waveforms


Rate

  • Evaluate the distance between R-R intervals.

  • 1 small box = 0.04s

  • 1 large box = 0.2s


  • Counting based off of large boxes:

  • Irregular rhythms (or very slow/fast): ​

  • 6 second strip: # cycles × 10 = rate​

  • 10 second strip: # cycles × 6 = rate​

  • Rate > 100 = tachycardia​

  • Rate < 60 = bradycardia

Rhythm

  • Identify Basic Rhythm

    • Evaluated for pauses, premature beats, irregularity, abnormal waves

  • Always check for:

    • P waves before each QRS complexes

    • PR intervals to determine AV blocks

    • QRS intervals to determine bundle branch blocks

    • QT intervals to evaluate for risk for Torsade's and to limit / discontinue any QT prolonging medications

Axis



  • Normal Sinus Rhythm

    • Regular rate - 60-100bpm

    • P wave before each QRS

    • Normal P wave Axis

    • PR interval constant

    • QRS <120ms


  • Sinus Bradycardia

    • Sinus rhythm criteria with rate < 60 bpm​


  • Sinus Tachycardia

    • Sinus rhythm criteria with rate > 100 bpm


  • SVT​

    • Any tachycardia above bundle of His, but commonly used to describe AVNRT​

    • Regular​ Rate ~140-280​

    • Narrow QRS (< 120 ms) ​

    • P waves can have retrograde conduction or inversion​


  • Atrial Fibrillation​

    • Irregularly irregular ​

    • No P waves​

    • Variable ventricular rate​

    • QRS usually narrow, < 120 ms unless other BBB, accessory, aberrancy ​

    • Fibrillatory waves


  • Atrial Flutter​

    • Atrial activity ~300 bpm​

    • Narrow QRS < 120 ms​

    • “Saw tooth” inverted flutter waves in inferior leads​.

    • Ventricular rate a fraction of atrial rate

      • 2:1 block = 150 bpm

      • 3:1 block = 100 bpm

      • 4:1 block = 75 bpm


  • Ventricular Tachycardia​

    • Wide and broad complex tachycardia​

    • Uniform QRS complexes in each lead


  • Ventricular Fibrillation​

    • Chaotic irregular deflections​

    • No P waves, QRS, T ​

    • Amplitude rate 150-500 ​

    • Amplitude decrease with duration (coarse to fine)


  • AV Blocks​

    • First Degree Block

      • Fixed PR interval elongation (>200ms)

    • Second Degree block Mobitz Type I​ (Wenckebach)

      • Progressive prolongation of the PR interval until a non-conducted P wave

    • Second Degree block Mobitz Type II​

      • Intermittent non-conducted P waves without progression of PR interval

    • Third Degree​ block

      • AV dissociation​

      • Independent atrial and ventricular rates


  • Myocardial injury morphologies

    • Ischemia

      • Inverted T waves (symmetrical inversion)

      • Usually in same lead that demonstrates acute infarction ​

      • ST depression can represent subendocardial ischemia


  • Injury

    • ST elevation​

    • Represents an acute process (normalizes over time)​

    • Acute or recent infarct can presents with significant Q waves


  • Infarct / Necrosis

    • Significant Q wave​

    • > 1 mm wide or 1/3 amplitude of QRS​

    • Significant Q waves can remain over time (permanent)


Advanced ECG Interpretations

  • sinus arrhythmia, wandering pacemaker, MAT, torsades

  • Ectopy​

  • Ventricular Hypertrophy​

  • Atrial enlargement​

  • Electrolyte abnormalities​

    • Sinusoidal waves

    • hyperacute T waves

    • u waves

  • Fascicular blocks/hemi-blocks​

  • Aberrant conduction patterns​

  • Brugada criteria​

  • Wolf-parkinson-white

  • Epsilon waves

  • OMI (occlusive myocardial infarctions) vs. STEMI paradigm shift

    • Sgarbossa criteria​

    • Wellen's waves

    • DeWinter T waves

    • RV infarction

    • Posterior MI

    • Diffuse ST depression

    • Wide based peaked T waves

  • Medication effects

    • TCAs

    • Digoxin

References

  • Cadogan, Mike. “ECG Lead Positioning.” Life in the Fast Lane • LITFL, 30 Jan. 2022, litfl.com/ecg-lead-positioning/. ​

  • Cadogan, Mike. “ECG Library.” Life in the Fast Lane • LITFL, 14 Nov. 2021, litfl.com/ecg-library/. ​

  • Cummins, Richard O., et al. ACLS Provider Manual. American Heart Association, 2004. ​

  • Dubin, Dale. Rapid Interpretation of EKG’s: Dr Dubin’s Classic, Simplified Methodology for Understanding EKG’s. Cover Publishing, 2016.

John Coacci, DO

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