ECG STEPS,10 STEPS IN ECG INTERPRETATION

10 STEPS IN ECG INTERPRETATION

1. ECG BASICS Dr.G.VENKATA RAMANA MBBS DNB FAMILY MEDICINE

2. E lectrocardiogram ( ECG ) is the representation on paper of the electrical activity of the heart The electrocardiogram paper is a graph paper where for every five small (1 mm) squares you can find a heavier line forming a larger 5 mm square

3. The vertical axis measures the amplitude of the heart’s electrical current It is measured in millivolts (mV ) By standard, 10 mm in height equals 1  mV Therefore each 1 mm square on the vertical axis equals 0.1 mV and each large square, 0.5  mV The horizontal axis measures time On a standard ECG the paper speed is 25  mm/s Therefore , each 1 mm square on the horizontal axis equals 0.04 s , and each large square , 0.20  s   If needed, we can increase paper speed (to see wave abnormalities) or decrease it (to check for rhythm disorders); we can also increase the amplitude (if low voltage is present) or decrease it (when QRS complexes are too large)

4. Electrocardiogram paper measures: Vertical: 1 mm = 0.1 mV. Horizontal: 1 mm = 0.04  s

5. STEPS IN ECG READING First look for Standardization 1.RATE Normal Fast Slow 2.RHYTHM S upraventricular ( SA node/ Atria/ AVjunction ) Ventricular Conduction (Normal, impaired, accelerated) Regular or Irregular 3.AXIS Normal Left axis Right axis 4.P WAVE Present or Absent

6. If P waves absent Completely absent Intermittently absent Present but not obvious If P waves present look for Morphology Uniformity Amplitude Duration No of P waves per QRS complex 5. PR INTERVAL Normal, Short or Prolonged Does the PR interval vary or can it not be measured? Is the PR segment elevated or depressed?

7. 6.QRS COMPLEX Are there any pathological Q waves? Are any R or S waves too big? Is there a dominant R wave in aVR ? Is there a poor R wave progression? Are the QRS complexes too small? How is the width of QRS complexes? Are any QRS complexes an abnormal shape ?

8. 7.ST SEGMENT F lat Depressed Elevated 8.T WAVE Are the T waves too tall? Are the T waves too small? Are any of the T waves inverted? 9.U WAVE P resent or Absent If present Prominent ? Inverted? 10.QT INTERVAL S hort Prolonged

9. This is recorded at  50 mm/sec  on the left (12-lead), and 12.5 mm per sec on the right (for rhythm)

10. Why use 50 mm/second? Doubling the standard rate can reveal subtle ECG findings hidden at the slower rates, in particular atrial flutter waves in a 2:1 block At 50mm/sec, P waves are more clearly discernible in a 2:1 ratio to QRS complexes

11. RATE CALCULATION FOR REGULAR RHYTHMS

12. RATE CALCULATION FOR IRREGULAR RHYTHMS

13. RHYTHM