Cardiovascular Diseases

ECG Rhythm Interpretation

How to Analyze a Rhythm

The ECG Paper

Horizontally One small box - 0.04 s One large box - 0.20 s Vertically One large box - 0.5 mV

Rhythm Analysis

Step 1: Calculate rate. Step 2: Determine regularity. Step 3: Assess the P waves. Step 4: Determine PR interval. Step 5: Determine QRS duration Step 6: ST -T

Step 1: Calculate Rate

300/No of large square between 2 R waves= 90 bpm

Step 2: Determine regularity

Look at the R-R distances (using a caliper or markings on a pen or paper). Regular (are they equidistant apart)? Occasionally irregular? Regularly irregular? Irregularly irregular? Interpretation?
Regular
R
R

Step 3: Assess the P waves

Are there P waves? Do the P waves all look alike? Do the P waves occur at a regular rate? Is there one P wave before each QRS? Interpretation?
Normal P waves with 1 P wave for every QRS

Step 4: Determine PR interval

Normal: 0.12 - 0.20 seconds. (3 - 5 boxes)

Interpretation?

0.12 seconds

Step 5: QRS duration

Normal: 0.04 - 0.12 seconds. (1 - 3 boxes)

Interpretation?

0.08 seconds

Step 6: ST -T

ST Start from S wave till the beginning of T wave


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IHD *Subendocardial ischemia *Non q wave MI *Reciprocal changes in acute MI NON-ISCHEMIC CAUSES *VH, BBB, digoxine, hypokalemia, MVP, CNS diseases
ST depression

ST elevation

ST Elevation convex upward *Acute MI *Prinzmetal angina *Ventricular Aneurysm *Normal variant ST Elevation concave upward *Pericarditis OTHER CAUSES (LBBB,hyperkalemia)

ST elevation

Abnormalities of T wave
T INVERSION *MI *Ischemia *Pericarditis *Myocarditis *CNS dis *VH (strain pat.) *Digoxine *MVP PEAKED T WAVE *Anxiety *Hyperkalemia

Rhythm Summary

Rate 90-95 bpm Regularity regular P waves normal PR interval 0.12 s QRS duration 0.08 s ST -T isoelectric Interpretation? Normal Sinus Rhythm

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Reading 12-Lead ECGs
The best way to read 12-lead ECGs is to develop a step-by-step approach (just as we did for analyzing a rhythm strip). In these modules we present a 6-step approach: Calculate RATE Determine RHYTHM 3. Calculate INTERVALS 4. Determine QRS AXIS 5. Assess for HYPERTROPHY 6. Look for evidence of INFARCTION

QRS AXIS

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HYPERTROPHY

LVH Sv1+Rv6>35 mm RVH Rv1/Sv1 >1


LVH
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RVH
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