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

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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 ......

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.....

MORPHOLOGY OF THE ECG WAVES-SELF-ECG EDUCATION-F

MORPHOLOGY OF ECG WAVES

• 
  
• The Article:-

This is the last and final step to expertise the ECG education after the identification of the ECG-waves.In this article we will analyze the morphology, physiology, and the pathology of the ECG-waves.

VALIDITY OF THE ECG

Fig-1

Before going into the heading first thing we must confirm the validity of the ECG. To check the validity we must see the correct placements of the leads. If the leads are wrongly placed or mistakenly interchanged then the whole ECG will appear abnormal leading to wrong diagnosis and treatment.
For example the nature of the ECG recorded by aVR electrode (augmented Voltage Right) is a mirror image of the ECG recorded by aVL and lead-II electrodes.
Because the aVR electrode is placed far right from the heart at the right-hand wrist or shoulder.Since the axis of the heart and its activities are all towards left this lead record the sinus rhythm upside down and which is normal as shown in Fig-1 above.
If in case the aVR records a normal positive rhythm instead of mirror image then there are problems either in the heart (Dextrocardia)or due to leads misplacements.
Dextrocardia means the hearts axis is abnormally rotated to the right or extreme right. Hence a proper diagnosis must be conducted by the doctor. If Dextrocardia is absent then the patient has to be sent back to the ECG room to retake the ECG with correct placements of the leads.

P-waves:-Morphology

Fig-2

P-wave totally represents the contractions of the two upper chambers(Atria). See Fig-2. The three types of P-waves have been shown with three different morphologies. Out of the three two are abnormals in appearances which are pathological.
The first P-wave is the normal one. The morphology of the normal P-wave as shown in Fig-2 is a half-circle bump above the baseline with not more than 2.5mm(<2.5ss) both in height and width. The bump has been equally halved. The right one-third of the side (R)represents right atrial contraction, and the left one-third of the side represents the left atrial contraction and the remaining curved upper portion is the combination of the right and left atrial contraction represented by (R+L).
The second P-wave is with a cone shape that indicates there is a problem at the right side of the heart. That is right upper chamber enlargement due to problem in the tricuspid valve(the valve in between the right upper and lower chambers) stenosis,(narrowing of the valve opening), or lung diseases.-Cor Pulmonale
The third abnormal P-wave. It is M-shaped or it may look like a camel hump. This is due to the left upper chamber enlargement due to the mitral valve (the valve between the left upper and lower chambers) stenosis.
QRS-MORPHOLOGY:
The following is the QRS-Complex which represents the contractions of the two lower chambers(Ventricles).
Any abnormality in the appearance or morphology of QRS represents the problems (Pathological) in the lower chambers. See below the Fig-3

Fig-3

This is a typical morphology of the QRS which describes the morphological changes during Right Bundle Branch Block (RBBB) and Left Bundle Branch Block(LBBB).
In the RBBB the right ventricle is not directly activated as it should be by the right bundle branch because there is an electrical conduction block. The left ventricle is activated by the left bundle branch and these impulses are conducted by the LV myocardium to the right which then contracted. In this ECG we can observe the rapid depolarization of the L.V along with a slowed and delayed depolarization of the R.V.This is clearly indicated by the first shortened widened QRS complex followed by a deep negative deflection as S-wave and then a steep positive upward deflection, the R'-wave. These changes can be observed in the V1 electrode which is viewing the heart from the right. The V-6 electrode which views the heart from the left records a mirror image of what V-1 records (see Fig-3-RBBB).The reason is very simple. Because it views the heart from the left side but the conduction is towards the right and away from the left.
Similarly in LBBB the left ventricle is not directly getting conduction from the left bundle branch instead it receives the impulses from the right ventricular myocardium and the contraction is delayed while the right ventricle contracts normally and quickly.
See the Fig-3 above. The V-6 lead receives positive impulses hence it records positive deflection (Fig-3)
QRS IN MI:-

Fig-4

In the above figure a typical abnormal QRS is presented. There is a deep negative deflection of the Q-wave and the ST-segment is elevated.
A normal Q-wave represents an impulse with a small magnitude passes from left to right at the intraventricular septum. The impulse is followed by a large impulse with a large magnitude passes from right to left which is represented by the R-wave.
But a deep negative Q-wave indicates that the ventricular contraction is delayed due to a blockade, because the impulse which passes from left to right very strong. The elevated ST-segment also indicates the irregular repolarization or relaxation of the ventricles. If the QRS looks with this morphology it means it confirms the presence and prediction of heart attack or myocardial infarction (MI)
QRS IN VENTRICULAR TACHYCARDIA:-
Tachycardia means elevated heartbeats per minute (<160 bpm)

Fig-5
Ventricular Tachycardia(VT)

In Fig-5 some of the recordings such as V4, V5, and V6 are omitted as they are also somewhat similar to other recordings except V-1, and V-2.
This is because V1 and V2 are viewing the heart from the right side.
aVR is recording a  positive deflection this may be due to the rotation of the heart axis towards the right extreme. Hence VT may be originated from the right ventricle.
In general, during tachycardia the heartbeats are irregular and the QR segment is wider and there are more R waves per minute. In Ventricular Tachycardia, in the ECG the QRS complex is wider than 3.5 small boxes (>0.12 seconds)
Also in VT the P-wave has no connection with the QRS.
There is a fusion of sinus and ventricular rhythms.
Torsade de Points:-

Fig-5A

If the VT if not treated properly it becomes polymorphic (very irregular) as shown in the figure above. At certain points sinus rhythm may return but soon the QT intervals widened (>500ms, see Fig-5A above) followed by irregular twitching of QRS around the isoelectric line may indicate Torsade de Points which will lead to fatal V.Fib followed by death.

QRS IN VENTRICULAR FIBRILLATION(V.F)

See the fig-6  below which is the ECG recorded by the lead-II.

Fig-6

Fig-6-A

See the above Fig-6 and Fig-6A which shows the ECG of VF recorded by lead-II. The morphology shows that there are no P-waves. The ventricles are fibrillating without any coordinations.
                                      Continued...

HOW TO IDENTIFY ECG WAVES?-ECG EDUCATION-E

ECG-NOMENCLATURE

In this article we are going to study how to identify a particular wave among the important five waves namely P, Q, R, S, T.

At any time when we examine the ECG we should always note that the first wave of the heartbeat as shown in the figure should be identified as P-waves. The P-waves appear in many forms as shown below.

FIG-1

The above figure (Fig-1) note that the P-waves are in different forms. Except for the first one all three are abnormal P-waves. At the last abnormal P-wave, the P-wave is almost absent.
As we already studied from the last posts about ECG that the P-wave represents the contraction (depolarization)of the upper chambers (Atria) of the heart. Hence any irregular abnormal P-waves are seen in the ECG then it means there are problems in any one of the atria or both. If there is a conical shaped apex in the P-wave (Fig-1-1st abnormal) it means the right atrium is enlarged.
If there is an M-shaped apex in the P-wave (2nd abnormal in Fig-1) it means the left atrium is enlarged.
If the P-wave is overlaid on the baseline, disappeared, or almost absent(3rd abnormality-Fig-1) then  SA nodal blockade and atrial fibrillation must be suspected. In atrial fibrillation the P-wave is replaced by tiny irregular f-waves.
The next wave follows is the Q-wave which forms a part of the important QRS-complex.
The Q-wave can be defined in two ways.
1.Q-wave is the wave with a minute or large negative deflexion following the P-wave. or
2. The Q-wave can be defined as the wave with a small or large negative deflection which is immediately followed by the R-wave.In other words 
Any negative deflection whether it is small or large immediately before R-wave should be identified as Q-wave or 'q'-wave if it is small 
QRS-Nomenclature
As we know that the QRS-complex is the main part of the ECG so we should deal with a special for it as follows:-
Three things we must keep in our minds.
1.Position of the waves
2.Nature of deflection (+ or -)
3.Size of the deflection.
See the following figures Fig-2; and Fig-3.Fig-4; and Fig-5.

Fig-2
A normal QRS

See the above Fig-2 a normal QRS complex is displayed.

Fig-3

In the above figure (Fig-3)there is a typical QRS complex is displayed. Sometimes we come across such complicated ECGs to identify the waves.
In such cases we should always devise a common theory which states that in any QRS- complex the first negative deflection immediately before the R-waves must be named as Q or q-waves depending upon the size of the deflection. If there are more than one it should be quoted with ' (prime)
Note in the above figure (Fig-3) the Q-wave is absent as there is no first negative deflection before R-wave.
Secondly in any QRS complex any first positive deflection within the complex should be named as R or r waves with ' (prime) if there are more than one according to its sizes.
See the following another typical QRS.

Fig-4

Thirdly any first negative deflection immediately after the R-wave is the S or s waves with '(prime)
if more than as per its sizes.
In the above figure (FIG-4) again there are no Q-waves. But there are 2 consecutive positive deflections represents two R-waves (R, R') immediately followed by two consecutive negative deflections named as S and S'.
Then the nomenclature of the T-wave which represents the relaxation of the ventricles.

Fig-5

In the above figure note the position deflection of the T-wave. After the T wave, after the ventricular relaxation there is no electrical conduction up to the next cycle started by the SA-node the pacemaker. Hence the interval T-P is the perfect and absolute iso electrical line to be kept for reference.
                    Continued in next post(F)