SUMMARY-ECG EDUCATION-F-SAMPLE ECGS AND PRACTICES HOW TO READ THEM

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ECG SUMMARY-2.SAMPLE ECGS AND HOW TO READ THEM

Now we can practice the interpretation of ECG at home by using portable ECG devices. The normal sinus rhythm in ECG by a single lead portable device (Fig-1)

FIG-1

The normal sinus rhythm will be seen in the ECG paper recorded by the limb lead-II as in Fig-2.

Fig-2

In the above Fig-2 the normal sinus rhythm is marked with segments and intervals. These segments are also as important as waves. There are three segments and two intervals which are very important.

The P-Q segment which starts from the end of the P-wave to the beginning of the Q-wave represents the electrical impulse travels from the AV node to the Bundle of His. (See Fig-2)

The segment QRS complex represents the ventricular depolarization.

The ST segment represents the time taken by the ventricles to relax.

The T-wave represents the relaxation of the ventricles. The T-wave starts slowly and ends fast.

T-wave should be in the same direction as the QRS-complex in V2, V3, V4, V5, and V6.

Its apex can be asymmetrical or some times rounded.

The amplitude of the T-wave should not be less than 0.2mV in leads V3 and V4 and not less than 0.1mV in V5 and V6.

The P-wave has a duration of not more than 0.08 to 0.12 secs (<2 to 3 ss).

The PQ-segment must have a duration of not more than 0.12 to 0.20 secs(3 to 4 ss)

The duration of the QRS complex must be less than 0.12 sec (<3ss). If the QRS duration is more than 0.12 sec (>3ss) then it is known as QRS warning or Ventricular Escape Rhythm. This rhythm is not originated from the SA node rather it is originated from the ventricular myocardium itself. And this can be due to a bundle branch block. Hence the QRS is widened during either RBBB or LBBB.

The QRS amplitude is greater than 0.5mV in at least one standard lead (I, or II, or aVF), and greater than 1mV in at least one chest leads (V5 or V6)

The upper average limit of the amplitude is 2.5 to 3 mV.(ImV = 1ss in Y-axis)

The septal q-wave in lead-I,aVL, V5, and V6 must be less than 0.04 secs and the amplitude is 1/3 rd of the R-wave in V5 or V6.

The ST segment is very important as characteristic changes happen in ST-segment during a heart attack or angina.

If the ST segment is elevated above the x-axis as shown in Fig-3 below is known as ST-SEGMENT ELEVATED MYOCARDIAL INFARCTION (STEMI) or HEART ATTACK.

If ST-segment is depressed below the x-axis as shown in Fig-3 then it is due to angina or ischemia.

Fig-3

The PR-interval must be between 0.12 to 0.2 secs

(3 to 4 ss).This represents the electric current travels from atria to the SA node. Elongated duration of the PR interval suggests a heart block. The shortening of the PR interval suggests the presence of Wolff Parkinson White Syndrome or Lown-Ganong-Levine Syndrome.

The QT interval another important parameter to indicate heart problems. The corrected QT interval is calculated as follows:-

                      QTc =                   

QTc=QT interval corrected
RR=The interval between two R-waves
ss->small squire
LS-> Large Squire

In the above calculation the range should be within 0.38 to 0.42 seconds (9.5ss to 10.3ss or 2LS approx). If it is above this then it indicates the presence of ventricular tachycardia or ventricular fibrillation.

A Sample ECG Report-NORMAL

Fig-3A

In Fig-3A a normal ECG report is being examined and interpreted as follows:-

See the columns recorded by the leads II, V5, and V6 in the above Fig-3. All of the three leads' recordings show similar rhythms with clear P, Q, R, S, and T waves resemble the one shown in Fig-2. Hence this ECG is normal with no heart problems.

Calculating the heart rate by a large squire method. There are 4 LS in between any two R-waves. (Fig 3 A)

Hence the HR      = 300/5 =60 bpm.

By the 6 sec method:-

6 R-waves are noted in 6 secs (within 30 LS), try yourself.

Hence the HR     = 6 X 10 =70 bpm

The three leads we examined are placed more or less along with the normal axis of the heart. Hence they give 80% of the ECG results.

Check the rhythm recorded by the electrode aVR which is a mirror image of lead II recorded. Because this lead is placed on the right-hand wrist of the body which is far away from the axis of the heart and it recorded a negative rhythm. Hence the ECG is normal. The above Fig 3A has been modified to more clear in a different way as Fig-3B below.

Fig 3 B

In the above ECG sample (Fig-3 B) each leads columns have been conveniently separated to give a more clear view. Note the important leads such as II, V5, and V6. All recordings are with positive deflections with distinguishable P, Q, R, S, and T waves.

By measuring the segments and intervals they are within the limits. Hence it is a normal ECG.

ECG SAMPLE WITH ABNORMALITIES:-

1.HEART ATTACK-A-HA Due To Posterior Conduction Block:

Fig-4 A

Fig 4 B

See the above two figures 4-A and 4-B both are sample ECGs taken at a patient who suffered from a kind of heart attack called posterior wall myocardial infarction.

Posterior means the bottom side. Three leads II, III, and aVF are looking at the heart from the bottom. Hence their recordings will give a clear picture in this case. See the elevated ST segments which have been marked in all the leads' II, III,aVF recordings indicates the posterior wall MI.

2.HEART ATTACK-B-Anterior Wall MI.

Fig-5

In Fig 5 a typical heart attack has been recorded as ECG which is due to the anterior heart wall ischemia. This can be identified by the ST segments elevation in the ECGs recorded by the leads V3 and V4 and to some extent by V2 which are covered in the green squires.

V4 which has the anteroseptal view also indicates the ST segment elevations covered by the green squire.

Leads I, have a left lateral view shows a little elevation.

aVF, lead III, and lead II which have a posterior view and show ST depression-Hence the result is Anterior Wall HA.

ECG SAMPLES IN PALPITATIONS:-

Fig-6A

Fig 6B

The above Fig-6A represents the sample ECG taken during palpitations. Check the ECG recorded by the lead II. The recording shows the rhythm is randomly regular and irregular and very fast. This we can prove by calculating the Heart Rate by the two methods which we already described. See the Fig-6B and 6C below

Fig-6C

In the above two figures it has been observed the heart rate above 100 bpm and hence it is a fast heart rhythm or palpitations.
Palpitations are due to many causes:
1.Thyroid overactivity
2.Mitral valve prolapse.
3.Alcohol
4.Anxiety and panic attacks
5.Stress.                                   Continued ......