ECG READING EXERCISES-K-MODEL ECG IN HEART ATTACKS

ECG IN ANGINAL ATTACKS

In this article we are to practice the interpretation of ECG reports during various conditions of angina pectoris.

Angina is caused by the imbalance between the supply and demand of oxygen by the arteries of the heart muscles (Coronary Arteries). When the demand exceeds supply the affected area of the heart muscle becomes darkened and weakened to act. This condition is called ischemia. This may result in chest pain.
Some people may suffer from angina but on examination there is no visible ischemia on their heart muscle. This may be due to hidden ischemia in the endothelium of the heart muscle which may be due to the block in micro-arteries of the endothelium.

Angina itself is not life-threatening but if it is left untreated it may precipitate a heart attack.

Anginas are many types but the serious one is the suddenly unstable angina.

Types of Angina:-

1.Unstable Angina-More dangerous and a prediction of an immediate heart attack. It is due to coronary artery blockage by clots, atherosclerosis, or by any other means like an air bubble.

2. Stable Angina-It is less severe than unstable angina. It occurs when a person does some work like running, physical exercise, or any other routine work. A brief rest can relieve anginal pain. But the pain may revert again if the person resumes the work.

3. Microvascular, Variant, or Prinzmetal Angina-These are less severe and less serious but proper food control with doctor's advice is necessary.

RISK FACTORS

1.Diabetes Mellitus

2.Cigarette Smoking

3.High Cholesterol

4.High B.P

5.LifeStyles

6.Family History

7.Kidney Failure

8.Over Stress

9.Obesity.

Model ECG in Unstable Angina:-

Fig-1A

Fig 1B

It is very easy to recognize the presence of Unstable Angina (UA) in ECG. The main recognizable feature is ST-segment depression. Check the model ECG in Fig-1B and inspect the ST-depression marked with a small red circle both in lead II and in lead V3.

Lead V3 shows the depression very clearly as it views the heart more closely from the lateral left side.
The exact appearance of ECG waves is simulated in Fig 1A. Compare the images of Fig-1B with Fig 1A.

ECG in Stable Angina:-

Fig 2A

Fig 2B

In Fig-2A and Fig 2B two ECG models taken in patients with Stable Angina have been presented.
Stable Angina or SA is the condition that occurs when the patient is at work and disappears when the patient is at rest.
In the above two figures the ECG waves are normal at rest and show ST-segment depressions after some physical activities such as routine home or office works or lifting something or running etc.etc.The depressions have been marked by small red circles in Fig-2B.

MICROVASCULAR ANGINA

Fig-3

Microvascular angina occurs when tiny arterial blood flow is blocked by clots, atherosclerosis, or air bubbles.

In a similar manner we can understand variant or Prinzmetal anginas. These three anginas can escape from diagnosis and can be detected by ECG examinations which shows typical ST-segment depressions as shown above.

Commonly all anginas have common symptoms like chest pain or chest pressure radiate from the left arm, followed by sweating headache, nausea, vomiting, and loss of consciousness.

Continued...

ECG READING EXERCISES-J-MODEL ECG IN HEART ATTACKS

MYOCARDIAL INFARCTION-HEART ATTACK

We have already seen how to interpret the ECG reports taken in anterior, inferior, and posterior heart attacks in Article-F in this blog. In this article we are to study how to read the ECG reports in various conditions that may results in heart attacks other than the conditions already described. Heart attack can result from any pathological condition of the myocardium-(heart muscle.)

Fig-1A

Fig-1B

Fig-1C

Check and compare the above ECG report shown in Fig-1C with the images shown in Fig-1A and 1B.
In Fig 1A a normal sinus rhythm has been drawn by hand. In Fig 1B another simulated ECG image has been drawn to demonstrate its deviations from the normal rhythm due to heart attack. It is clear from the Fig-1B that the abnormal rhythm contains an elevated and depressed ST segment.
The ST segment represents the time taken and the work done during ventricular relaxation. But the deviation indicates that the ventricles are not properly relaxed.
The elevation confirms the prediction of the immediate event of a heart attack while the depression indicates the presence of ischemic angina which may or may not result in a heart attack immediately.
Now we can interpret the model ECG report shown in Fig-1C. First check the records of the master lead -II which is the important lead that views the heart from the normal axis.
See the deviations marked in small red circles. The ST segment is elevated.
Now we can Check the unipolar electrodes aVL and aVF which also view the heart from left top and bottom respectively. They are also showing the elevation.
The elevation is more clear in the chest leads such as V4, V5, and V6 which view the heart very closely and from the left.
And hence this ECG is foretelling about the event of a severe heart attack.

1.HEART ATTACK WITH BUNDLE BLOCKS: -A- RIGHT BUNDLE BRANCH BLOCK (RBBB):-

First we must know about what is the bundle and its branches, diagrammatically.

In the above diagram it is clearly seen that the electrical current which is conducted from the AV node to the Bundle of His is blocked in the right branch and passed through the left branch and arrived at the RV indirectly from the left. This is RBBB in which the right ventricle cannot receive electrical current from the HIS bundle branch but receiving it from the left ventricular muscle as shown in the diagram above.

In a similar manner the LBBB can also be understood.

RBBB and LBBB are asymptomatic and may not be serious if they are benign. But they become serious if they are with other problems in the heart such as ischemia, arrhythmias, or drug overdoses like BP medicines or antiarrhythmic medicines like beta-blockers and digoxin, etc.

In aged conditions when the heart muscles are weak these benign conditions may become violent.

Fig-2A

Fig-2B

In Fig-2A there are simulated ECG drawings that have been shown to demonstrate the appearance of the rhythm in lead-II,leads-V1, and V6.
See the M shaped rhythm in lead V1 and N shaped rhythm in lead V6.
In V1 and aVR which view the heart from the right the rhythm contains one r, and one R-waves and an S-wave and no Q-wave. Hence this is an RBBB rhythm.
RBBB is many times may not be a serious problem but if it is associated with a heart attack or with a weak heart muscle it can be fatal. In RBBB as we already described the hearts axis is slightly shifted to the right.

B-LEFT BUNDLE BRANCH BLOCK(LBBB):-

Fig 2C

Compare the above model ECG taken during LBBB in Fig-2C with the simulated hand-drawn LBBB image in Fig 2B and observe the camelback like M appearance. Hence this an LBBB rhythm.

Symptoms:-

The most common symptom is syncope (fainting) or presyncope (feelings to syncope).

Causes for Bundle Blocks

1.Beta-blockers like atenolol, metoprolol
2.Calcium canal blockers like amlodipine, nifedipine
3.antiarrhythmic drugs like digoxin
If the drugs are withdrawn in doctors' supervision bundle blocks can be corrected.

                                                                                Continued.......

SUMMARY-ECG EDUCATION-I-EXERCISES-CONTINUED-Palpitations due to diseases-3

SAMPLE ECG EXERCISES-3

1.Ventricular Tachycardia(VT-VPalpitations-1)

Fig-1

See Fig-1 and check the records by lead II which is the master lead. Check the QRS complex. It is widened more than 120 million secs (>3ss). There are 2 LS in between a consecutive R-R. Hence the heartbeats are 300/2=150 bpm. Hence it is ventricular tachycardia. The ECG records by aVL,aVF, V4, V5, and V6 all show similar trends. If VT is left untreated it leads to more serious V.Fibrillation followed by cardiac arrest.
VT is of two types. Monomorphous and Polymorphous (Torsade de Points, TDP).Fig-1 shows a monomorphous VT in which the rhythms are normal.No P-waves. That means the conductions are not from the atria, and AV nodes.

Fig-2

The Fig-2 shows a sample ECG report taken during polymorphous VT or Torsades de Points.
See the Lead-II stripe which shows the poly phases of the rhythm. The rhythm is irregular. It randomly swinging around the baseline as elevations and depressions. Check the heartbeats. It is undoubtedly above 300 bpm as we cannot count squires between any two consecutive R-R waves. Leads V1 to V6 shows swirling rhythms.No P-waves.ST segments are randomly seen elevated. Hence this is polymorphous and Torsades de Points.
The stripe of lead II shows, in the beginning, weak ventricular rhythms with long QT intervals followed by the swinging of waves around the baseline (Torsades de Points).
Causes For VT:-
1. The condition develops due to low potassium, low calcium, or low magnesium.
2.Antiarrhythmic drugs such as quinidine, procainamide(I-a), sotalol, and amiodarone (III), etc.
3.Anti depressives such as amitriptyline, imipramine
4.Antipsychotics such as haloperidol.
3.Antipsychotics such as haloperidol, droperidol, chlorpromazine
If you are taking the mentioned medicines stop to take and consult your doctor.
Treatments:-(Subjected to doctors consulting)
Magnesium sulfate, Calcium salts, or Potassium salts.
4.Beta-blockers
Torsades de Points if left untreated may lead to cardiac arrest.

VENTRICULAR FIBRILLATION(V.Fib):-

V. Fib is another kind of palpitations and is the most serious one.

Fig-3

A sample ECG taken in a patient suffered by V.Fibrillation is shown in Fig-3.
As a general concept lead-II is the hero lead whose records represent 75% of the heart's condition.
Also records by the chest lead V1 which looks the right ventricle, and  V5 and V6 which looks the left ventricles are also important. Generally all the 6 chest leads are very important because unlike the limb leads they watch ventricles very closely.
In Fig-3 in lead II, V1 and V6 are all showing the swinging waves of QRS complex.No P-waves means the ventricles are fibrillating independently. The heart rate is >300 bpm. Beats are very irregular. The conductions are not in a uniform axis. These are known as ectopic conductions.
Finally if ventricular tachycardias are not early diagnosed for correction it may result in serious consequences such as life-threatening V.Fibrillations and death.

SUMMARY-ECG EDUCATION-H-EXERCISES-CONTINUED

                                                         

SAMPLE ECGS-2

A.PALPITATIONS DUE TO DISEASES-1.ATRIAL FIBRILLATIONS

Normal Rhythm

Fig-1

The above ECG sample shows a kind of arrhythmia known as atrial fibrillation (atrial palpitation)

Atria are the upper chambers of the heart. We know the pacemaker SA node is situated at the right atrium. When SA node starts the conduction which spread over all the atria and the atria contract. We know the normal atrial contractions are represented in the ECG as P wave.

See the above Fig 1. The P-waves are almost absent. Instead of P-waves (check the Normal Rhythm Image above) there are fibrillatory waves seen in the electrodes II, III, and aVF which view the heart from the bottom. The electrode I which view the atria from the top gives no clear waves at all but records fibrillatory waves. Hence we can conclude this is ATRIAL FIBRILLATION.
In atrial fibrillation the atria are fibrillating instead of contracting and hence no proper filling and emptying of the blood takes place. The ventricular contractions are also independent of atrial fibrillation and AV node. The R-R intervals are also randomly irregular. There is no PR interval as P-wave is absent. Waves are deviating randomly up and down from the baseline.
Atrial fibrillation may cause pulmonary embolism or brain damage such as stroke.
2.ATRIAL FLUTTER

Fig-2

See the above Fig-2 and compare this image with the previous one and observe the difference between the two atrial arrhythmias(Palpitations). The former is atrial fibrillation while the later is atrial flutter. Analyze the sample ECG image in Fig-2.
First analyze the lead II (the hero electrode) which views the heart from bottom left(normal axis).P-wave replaced by snaky spiral waves and the Q-wave is absent. The ST segment is raised above the isoelectric line. The R-waves are there with randomly elongated R-R intervals.
See the lead I which views the heart from the top.No P waves at all and R-R intervals are elongated.Lead-III which views the heart from the bottom right also record no P-wave. But all recordings shows there are no deviations from the baseline. Hence because of defective P-waves in all the leads, and elongated R-R intervals the problem is in the atria, which is known as ATRIAL FLUTTER.
The difference between A.fib and A.flut is that the former is characterized by elevated heartbeats (>180 bpm) with tachycardia (shortened R-R intervals)and random deviations from the baseline while the later is characterized by depressed heartbeats (<50 bpm), with randomly elongated R-R intervals (bradycardia) and no deviations from the baseline.
The condition is not as serious as A.fib, but if left untreated it may lead to serious consequences.
                                                 Continued.......

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

---

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 ......

SUMMARY-ECG EDUCATION-G

ECG-SUMMARY-1

1. The ECG is recorded in a graph paper which is composed of small squares with 1mm height and width. Also 5 small squires form large squires in height and width. The X-axis represents Time and the Y-axis represents electric conduction. Every small squires 1mV in height.

2. Normally the ECG machine is set up to move the graph paper 25 mm per sec in the printer. Some times this may be changed up to 50 m.m/sec.
3. Each 1mm height in the Y-axis represents 1mV.
4. A normal ECG is composed of 5 waves namely P, Q, R, S, and out of which three waves namely P, R, and T are positive upward deflections and Q and S waves are negative downward deflections.
5. The waves are identified as follows. In a normal ECG the first positive upward deflection is known as P-wave. The P-wave represents the atrial (upper chambers)contractions.
6. The P-wave is followed by a QRS complex with an interval.
7. The QRS complex is the representation of the ventricular (lower chambers) contractions.
8. In the QRS complex the first negatively downward deflection immediately followed by R-wave is known as q-wave or Q-wave according to its size. In other words a Q or q-wave is any wave which is after the P-wave deflected downward immediately before the R-wave. The Q wave represents the brief repolarization of the Inter Ventricular Septum(IVS) when a brief and weak electrical conduction is passing from left to right across the (IVS). See Fig-1 below.

Fig-1

9. After the Q-wave within the QRS-complex any immediately following positive deflection is the R-wave or r-wave according to its sizes. In other words any upward deflections immediately followed by S-wave are known as R-wave. The R-wave represents a strong ventricular contraction due to strong conduction of electricity from right to left from the Purkinje fibers, the bundle of His and across the IVS(see Fig-1)
10. Then within the QRS complex a brief negative deflection immediately following the R-wave is known as the S or s wave as per its sizes. In other words any negatively downward deflection within the QRS-complex preceded by R-wave is known as S or s wave. see Fig-2 below.

Fig-2

11.After the S-wave finally the ventricles relax after a brief interval which is represented by the S-T-interval.The T-wave is the final point or completion of one normal Sinus Rhythm. The next Sinus Rhythm starts again with the next P-wave. Hence the T-P interval, the interval between two Sinus Rhythms is the real isoelectric line as this line represents zero electric conduction in any situation whereas other wave intervals may deviate from the isoelectric line in abnormal conditions. (see Fig-3)

Fig-3

12. There are 12 leads that view the heart from 12 different angles. Out of which the bipolar electrode lead II is the hero which views the heart from the left bottom ankle which is more or less falls within the normal axis of the heart's electrical activities which is at -30 degrees to + 90 degrees. See Fig-4 below.

Fig-4

In the above figure note down the limb lead, II is viewing the heart from the bottom left which is more or less in the same ankle of the normal heart axis colored yellow in the circle. Hence the ECG recorded by this lead describes 80% of the total ECG representation.
aVR lead which views the heart from the extreme right gives the least representation of the total ECG.
Any ECG can be easily read out by looking at the lead II recordings which are at the bottom of your ECG report.
Lead aVL, I, are viewing the heart from the left anterior side
Chest leads V1, V2  looks the heart mostly the right Ventricular.
Chest leads V3 and V4, are looking at the left ventricle.
V5, V6, and aVL are viewing the heart from the left lateral side.
13.If in an ECG if there are negative deflections recorded by the left leads and positive deflections at the right leads indicates that there are abnormalities in your heart. 

Fig-5

14. It is the theory of electrocardiology that if current flows towards the lead then it is recorded as a positive upward deflection in the ECG by that lead and vice versa. It is explained in Fig-5 above.

15. Axis is very important. Already we know that the axis of the heart is normally towards the downward left, southeast at an angle of 0 degrees to +90 degree. This can be seen in the ECG as +ve deflections in aVF, lead I, and II.
More commonly the normal axis is extended beyond 0 degrees up to -30 degrees from +90 degrees. This can be seen in the ECG as positive deflections in aVL, lead I and II, and negative deflection at aVF.This is shown in the following diagram. (Fig 6A)

Fig-6A

 There are three types of the deviated axis which we can observe easily in the ECG. The three deviations are illustrated in the following figure (Fig-6B) 

Fig-6B

                                             

In the above Fig 6B the 3rd diagram shows the presence of Left Axis Deviation (LAD). This can be observed in the ECG as follows:
The electrode aVL and lead-I show positive deflections and all others show negative deflections. This condition indicates that there is left ventricle enlargement and right ventricle's weakness. Also due to the left anterior fascicular block.
The 4th diagram shows the presence of Right Axis Deviation (RAD). This can be observed in the ECG as follows:-
Only electrode aVF and lead-III show positive deflections and all others show negative deflections. This condition indicates that there are a right ventricular enlargement and a weak left ventricle. Also this may be due to the right anterior fascicular block.
The 5th diagram shows the presence of Extreme Deviation which is a rare but dangerous condition. This can be observed in the ECG as follows:-
Only aVR electrode shows positive deflections. This indicates
atrioventricular canal defects. Also this may be due to extreme and heavy enlargement of the right ventricle and light and weak left ventricle. There may be a right anterior and posterior fascicular block or ventricular tachycardia.
16. Fundamentally we should keep in our mind that the augmented electrodes and the limb leads are looking the heart in vertical views and the pericardial or chest leads looks the heart in close horizontal views and concentrated towards the ventricles.
V1and V2 view the right ventricles, V3 and V4 view the interseptum and to some extend overall view, and V5 and V6 view the left ventricle. See the diagram below.

Fig-7

In Fig 7 the location of the chest leads is shown diagrammatically. From the position of the chest leads we can observe any problems in the ECG.

Any problem in the right ventricle the V1 and V2 record negative deflections.-

Any problem in the left ventricle can be clearly notified at the V5 and V6 deflections.

                                        Continued.....