ECG for Interns UCI Internal Medicine Mini-Lecture

Learning Objectives

• Establish Consistent Approach to Interpreting ECGs

• Review Essential Cases for New Interns

• Provide Additional Resources for Future Learning

ECG Interpretation

What is your approach to reading an ECG? •Rate •Rhythm •Axis •Hypertrophy •Intervals •P wave •QRS complex •ST segment – T wave

Rate Square Counting: 300-150-100-75-60-50-42A

Count QRS in 10 second rhythm strip x 6

Rhythm

• Are P waves present?

• Is there a P wave before every QRS complex and a QRS complex after every P wave?

• Are the P waves and QRS complexes regular?

• Is the PR interval constant?

Axis

Left or right axis deviation? Look at limb leads I and aVF. •Normal: I +, aVF + •LAD: I +, aVF – •RAD: I -, aVF +

Hypertrophy

LVH: S in V1 or V2 + R in V5 or V6 ≥ 35 mm.

RVH: V1 R/S ratio >1 or V6 S/R ratio >1.

Intervals

What is the normal PR interval?

•0.12 to 0.20 s (3 - 5 small squares). Short PR – Look for Wolff-Parkinson-White. Long PR – 1st Degree AV block

What is the normal QRS?

•< 0.12 s duration (3 small squares). Long QRS - look for bundle branch block, ventricular pre-excitation, ventricular pacing or ventricular tachycardia

What is the normal QTc (QT/square root of RR)?

•< 0.42 s. Long QTc can lead to torsades to pointes.

P Waves

Evaluate the shape, height and width of P waves. • Multiple morphologies Wandering pacemaker or

Multifocal atrial tachycardia • Notched (M-shaped) P-wave in I and II, > 0.12 s

P-mitrale seen in severe left atrial enlargement

QRS complex Poor R Wave Progression in V1 to V6: suggests prior anterior MI

Pathologic Q wave: previous MI. Q wave amplitude 25% or more of the subsequent R wave, OR > 0.04 s in width + > 2 mm in amplitude in more than one lead

ST segment & T wave

Case #1

70 year old male with history of diabetes mellitus and hypertension occasionally feels lightheaded. He recently fainted while standing.

Case #1 ECG

Case #2

58 year old female with no significant past medical history presents with fatigue, lightheadedness and shortness of breath.

Case #2 ECG

Case #3

78 year old female with history of HTN, DM, HL, CAD admitted for syncope complains of palpitations and lightheadedness.

Case #3 ECG

Case #4

67 year old male with history of diabetes, hypertension, COPD presents with chest pain.

Case #4 ECG

Case #5

38 year old female with history of DM, HTN, CKD presents with 2 days of nausea and abdominal pain.

Case #5 ECG

Case #6

60 year-old man with history of HTN, HL, CAD presents with nausea, shortness of breath and chest pain.

Case #6 ECG

Additional Resources

Websites: • http://en.ecgpedia.org/ • http://ecg.utah.edu • http://ecg.bidmc.harvard.edu/maven/

Apps: • ECG Guide by QxMD (iPad and iPhone) • ECG Interpret (iPhone)

Books: • 12-Lead ECG: The Art of Interpretation, Tomas Garcia

(perhaps the best book on ECGs with detailed explanations and physiology.)

• Arrhythmia Recognition, Tomas Garcia

Summary

• Always keep a consistent approach.

• Do not rely upon machine reads.

• Practice makes perfect.