ECG INTERPRETATION -HALLMARK OF THE TRAINING PART 1

7 STEP METHOD OF  ECG INTERPRETATION

The following steps are required for interpretation of an ECG.
1.Rhythm
2.Rate
3.Waveforms- P ,QRS complex, T wave.
4.Intervals,-PR, and R-R
5. Heart axis
6. ST Segment
7.Abnormalities- e.g Hypertrophy, AV blocks,pericardial effusion


1.The  Rhythm.
There are 3 main types of rhythms.
 1.sinus rhythm- .there is evidence of P waves on the ECG strip indicating the source as sinoatrial node.
Lead 2 (THE GOLDEN LEAD) is ideal in determining presence of P waves.
Absence P waves would suggest-
            ATRIAL FIBRILLATION,
            ATRIAL FLUTTER.
  2.AV junctional rhythm- evident when sinoatrial node fails and hence the AV  node takes over the pacing mechanism of the heart.
 Common with patients with AV block. 2nd  and 3rd Degree AV blocks
 QRS COMPLEXES ARE BROAD  AND WIDE>120ms

 3.Idio-ventricular rhythm-The origin being the purkinje system of fibres.
  This is an emergency with patients being in ICU.
  Very low voltage and wide QRS complexes


2.The Rate.
Expressed in Bpm ( beats per minute)
The easiest and fastest way to calculate the rate is to use two R waves on the ECG strip.
Using a factor of 1500 divide it by the number of small boxes in between the two R waves.
Ideal in ICU EMERGENCY CASES.

Other ways exist such as -
Counting  NUMBER OF R WAVES OF 6 SECOND STRIP OF AN ECG STRIP AND MULTIPLYING THE  NUMBER BY A FACTOR OF 10.

The 300 METHOD is inaccurate and I don't advice you to use it.It involves dividing the factor of 300 by the number of large boxes in between 2 R waves.


3.THE WAVEFORMS
1.The P WAVE.-Indicates atrial contraction/DEPOLARISATION.
A normal P wave is upright /POSITIVE in Lead 2.

The P wave represents atrial depolarization. In normal ECGs the P-wave preceeds the QRS complex. It looks like a small bump upwards from the baseline. The amplitude is normally 0.05 to 0.25mV (0.5 to 2.5 small boxes). Normal duration is 0.06-0.11 seconds (1.5 to 2.75 small boxes). The shape of a P-wave is usually smooth and rounded.


ASK YOURSELF P-wave questions:

• Are they present?


• Do they occur regularly?


• Is there one P-wave for each QRS complex?


• Are the P-Waves smooth, rounded, and upright?


• Do all P-Waves have similar shapes?

2.QRS COMPLEX
The QRS complex indicates  ventricular depolarization. Depolarization triggers contraction of the ventricles.
Because of the larger tissue mass, the QRS complex is larger than the P wave. .

In this step, measure the QRS interval from the end of the PR interval to the end of the S wave.  Normal QRS  interval is 0.08 to 0.12 seconds/60-120 ms  (2 to 3 boxes).

ASK YOURSELF QRS questions:

• Does the QRS interval fall within the range of 0.08-0.12 seconds?


• Are the QRS complexes similar in appearance across the ECG tracing?
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