ECG for Interns презентация

Learning Objectives
Basics of EKG
Establish Consistent Approach to Interpreting ECGs
Rate, rhythm, axis, identifying ischemia
Review Essential Cases for New Interns
Provide Additional Resources for Future Learning

Basics of EKG: Einthoven’s Triangle and Vectors
+AVR
+AVL
+AVF
Why is lead II often so important?
->you can see the heart’s depolarization vector is in the same axis as lead II!
->this means that in normal conduction, the QRS should be upright in lead II

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 ? use this method to determine rate when rhythm is irregular (e.g., atrial fibrillation)

Rhythm
Look at the rhythm strip below and answer the questions
Are P waves present?
yes
Is there a P wave before every QRS complex and a QRS complex after every P wave?
yes
Are the P waves and QRS complexes regular?
yes
Is the PR interval constant?
yes
?Yes to all these questions, so this is normal sinus rhythm!

Axis
Axis is the general flow of electricity as it passes through the heart
? Look at the main direction of the QRS complex in leads I and AVF

QRS Duration
Normal QRS is < 120 ms
Prolonged QRS duration (>120ms) is seen in bundle branch blocks (BBB).
This is a result of abnormal conduction through the bundle branches or fascicles in the electrical conduction system
Different criteria for left and right bundle branch blocks but know the general morphology of each.

Left and right bundle branch blocks
Left BBB –
Dominant S wave in V1 (‘W’-shaped)
Broad, notched (‘M’-shaped) R wave in V6
Right BBB –
Tall R wave in V1 (‘M’-shaped)
Wide, slurred S wave (‘W’-shaped) in V6

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
- Q wave > 0.04 s in width + > 2 mm in amplitude in more than one lead

Hypertrophy
RVH:
V1 R/S ratio >1
OR
V6 S/R ratio >1
LVH: 2 commonly used criteria (use either)
1. Sokolow criteria:
S in V1 or V2 + R in V5 or V6 ≥ 35 mm.
2. Cornell criteria:
S in V3 + R in aVL > 28 mm (men)
S in V3 + R in aVL > 20 mm (women)

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
Left atrial enlargement (P mitrale) = wide, bifid P wave: >0.12s in lead II or biphasic P in lead V1 with largely negative terminal portion
Right atrial enlargement (P pulmonale) = peaked P: amplitude >2.5mm in inferior leads (II, III, avF) or >1.5mm in V1, V2
If multiple morphologies ? Wandering pacemaker or Multifocal atrial tachycardia (common in COPD)

ST segment and MI
ST elevation may indicate STEMI if the following are met:
At least 1 mm (0.1 mV) elevation in the limb leads (I, II, III, AVL, AVR)
At least 2 mm elevation in the precordial leads (V1-V6)
Elevation must be in at least 2 anatomically contiguous leads (see upcoming slides on “grouping leads”)
ST depression may indicate NSTEMI if the following are met:
Downsloping ST depression ≥ 0.5 mm
Must be in at least 2 anatomically contiguous leads

Evolution of an MI: Patterns on EKG

First thing you should do when looking for ischemia: Group leads by region!

EKG “Grouped Leads” correspond to area of injury

LET’S DO SOME PRACTICE CASES

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

Case #5 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