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Maybe the best ECG book by Hampton. It requires that you read the first two in order to get a hint about what you're going to see. Actually, these constant quizzes were a great way to seriously get a grip on the ECG. Definitely a requirement for those interested in ECG. Dec 25, Ahmed marked it as to-read Recommends it for: study. Nov 12, Sara Ahmed rated it really liked it Shelves: medical-books. She has also been feeling fatigued and occasionally light headed.
Using your analysis tool, complete the following table: What is the rate? Is it regular or irregular? P waves Is there ventricular activity? Is there a relationship between the atrial activity and the ventricular activity? Are the PR intervals normal? Activities 3 Mr Jones is a year-old man who has been suffering with a chest infection for several days and is being treated with oral antibiotics. His oral temperature is Today, he developed chest pain across his left lower thorax.
An ECG is taken to exclude a possible cardiac cause of this pain see fig 3. Record any abnormalities in the table below. Analysis What is the rate? You can either take recordings from your colleagues, or you could take some copies of ECGs that you record in your daily practice. Remember to seek permission from the person you are taking the ECG from, and make sure that any personal identifying data is removed in order to protect patient confidentiality.
Heart blocks or AV blocks occur when conduction from the atria to the ventricles is either blocked or slowed. These arrhythmias may be classed as first, second and third degree heart blocks. They may be caused by fibrosis of the conducting system, damage from coronary heart disease or as a result of drugs, such as beta blockers or digoxin. First degree heart block First degree heart block is when there is an excessive delay in the electrical impulse being passed through the AV node from the atria to the ventricles.
The prolonged PR interval is always constant. Figure 4. Mobitz type I or the Wenkebach phenomenon This is the most common type of second degree heart block. Each successive impulse from the atria finds it more difficult to pass through the AV node. Eventually the impulse is unable to pass through to the ventricles and a P wave is not followed by a QRS complex. When the next P wave reaches the AV node it has recovered and conducts normally. Then the pattern repeats. See Figure 4. The cycle then begins again. When the impulse is passed onto the ventricles the PR intervals are always constant.
Third degree complete heart block In third degree heart block there is no relationship between the P waves and the QRS complexes. The atria and ventricles are working independently. Atrial impulses can be blocked at the AV node or lower down in the conducting system. If the SA node fails, impulses may be initiated from a subsidiary site — located in the atria, at the AV node, or in the ventricles. In third degree heart block there are two different pacemaker sites, the atria and the ventricles. The site of the pacemaker stimulating the ventricles will determine the ventricle rate see Figure 4.
Treatment for heart blocks? The need for treatment for heart blocks depends on the haemodynamic consequences of the arrhythmia, rather than the precise ECG classification of the arrhythmia. First degree heart block produces no symptoms but can deteriorate and lead to the other types of block.
If the ventricular rate in second and third degree heart block is sufficiently low usually below 40 beats per minute , cardiac failure and hypotension may be precipitated. Extreme bradycardia may precipitate cardiac arrest so the heart must be accelerated. This may be achieved by inserting an artificial pacemaker. Note that there are regular P waves blue arrows and there are also regular QRS complexes red arrows but there is no relationship between them. If not, could it be a type of heart block? Which pattern does it fit?
Third degree No relationship between atrial and ventricular activity. It requires a bit of practice at first, as some of the blocks can appear very similar. In these activities you will look at different types of block, particularly the specific features that differentiate them from each other. You will also be tested on your learning up to this point in the book.
Answers are provided on pp. Activity 4. Is the ventricular activity regular? Is the PR interval constant or does it vary? If the PR interval is constant, is it normal? Are there missed QRS complexes? What is this heart block? Activities 4 Is there atrial activity?
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ECG 3 Activity 4. A Patient movement B Electrical apparatus C Palpitations D Poor electrode contact 8 Lead V4 is positioned… A In the fourth intercostal space on the right sternal border B In the fourth intercostal space on the left sternal border C In the fifth intercostal space on the midaxillary line D In the fifth intercostal space on the mid-clavicular line 9 The width of the QRS should be… A 0.
These unusual patterns are referred to as arrhythmias. There are many different types of arrhythmia, with many different causes. This chapter will explain five of the most common types of arrhythmia that you are likely to come across in practice: atrial fibrillation, atrial flutter, ventricular tachycardia, supraventricular tachycardia and ventricular fibrillation.
The origin is called the focus or foci, if there are several of them. It is fairly easy to see whether the focus of the arrhythmia is atrial or ventricular when you look at the ECG. As a rule, if the QRS complex is wide and abnormal to look at, the focus is in the ventricles. Atrial fibrillation Atrial fibrillation AF is the most common cardiac arrhythmia. It is usually experienced by the elderly and those with heart failure, but it can occur at any age.
These small, irregular contractions do not generate enough energy for the atria to pump blood into the ventricles, so blood pressure is often reduced as a result. As we saw in Chapter 2, normal atrial conduction is shown on the ECG as a P wave that is small and rounded. This is because the SA node is solely responsible for the conduction of the atria.
However, in AF many different parts of the atrial conduction system are conducting independently of each other, each trying to conduct the atria see fig 5. On the ECG, it will look as if there is no P wave. Instead there will be a lot of chaotic activity on the baseline see fig 5. These fibrillations are so fast and irregular that the AV node is unable to pass all the conduction waves through into the ventricles. The AV node therefore only allows some of the conduction waves through. Because these atrial conductions are random, the conduction waves that do pass through the AV node are also irregular.
This leads to an irregular heart rate. Figure 5. AF can be fast or slow, or it might vary between fast and slow. The irregularity has no pattern or cycle to it, and each QRS complex will have a different interval between it and the next. Atrial flutter Like atrial fibrillation, atrial flutter is an arrhythmia in which the atria conduct very rapidly — more rapidly than the ventricles.
The difference with atrial flutter is that there is only one focus in the atrium that is conducting quickly, rather than the multiple foci found in atrial fibrillation. Because there is only one focus for this arrhythmia, it is possible to see some rough-looking waves on the baseline. You will notice that when one flutter wave ends, another starts straight away. This is because the circuit that develops in the atria continuously conducts the atria, without a pause see fig 5.
The rate of these flutter waves is about per minute. If all these conduction waves were transferred through to the ventricles, we would see a heart rate of , which would certainly lead to loss of consciousness. Thankfully, the AV node does its best to control the heart rate, and does not allow every flutter wave to pass through to the ventricles. There is some variation in how often the AV node allows these conductions to pass into the ventricles. The ratio of flutter waves to each QRS complex may be , or Atrial fibrillation is like rockets going off at a firework party.
At any one time, there may be many rockets exploding in the sky, sending out sparks in all directions. In the atria, many foci are going off like rockets, sending out waves of conduction in different, random and unpredictable directions.
Atrial flutter is more like a catherine wheel, nailed to a post. It remains in one place but spins around very quickly, throwing out sparks in all directions each time it goes round. There is a more even pattern to the conduction in the atria because it is all coming from one place. Supraventricular tachycardia Supraventricular tachycardia SVT is the name given to a whole range of arrhythmias, each with different causes. Their one common characteristic is that they all have their focus above the ventricles, as the name implies.
SVT may be a result of the SA node conducting too quickly, or because of some genetic conduction disorder. Most commonly, SVT comes about as a result of some interruption or disturbance to some of the conduction tissue near or sometimes inside the AV node. In this case, a small circuit develops in the conduction tissue that rapidly generates ventricular conductions see fig 5. The circuit acts in a similar way to that which causes atrial flutter see above. However, unlike atrial flutter, the AV node is unable to regulate the heart rate, so each circuit results in a QRS complex.
SVT may come in short bursts or may be sustained for some time. Its focus is usually an area of conduction tissue that has been affected by cellular injury or by some local electrolyte changes. A small circuit develops in the conduction fibres and leads to a rapid cycle of conduction occurring across the ventricles see fig 5. Because the normal conduction system through the ventricles is not being used, the wave of conduction takes much longer to travel across the ventricular mass. This explains why the resulting QRS complex is broad and abnormally shaped see fig 5.
Ventricular fibrillation Ventricular fibrillation VF is a life-threatening arrhythmia and the patient requires immediate medical attention. There is no coordinated electrical conduction within the ventricles; and the ventricular myo-cardium twitches chaotically, rather than contracting. The heart has essentially stopped. If your patient is still conscious, then this is not VF, and you should check the equipment and electrodes.
VF can be Fine or Coarse but both types represent a cardiac arrest situation and should be treated accordingly. Activity 5. Answers are provided on p. On the left is a description of an ECG rhythm; on the right is a list of arrhythmias. Tick the box in the middle column next to the arrhythmia that you feel fits the description best. They are also commonly referred to as extrasystoles or premature contractions.
Ventricular ectopics Ventricular ectopics are early beats that begin in the ventricles and appear as wide, bizarre complexes see fig 6. They tend to be followed by a compensatory pause, and are not always preceded by a P wave. The wide, bizarre-looking shape is due to the early impulse beginning in one ventricle and spreading to the other but with some delay.
This delay occurs because the impulse is conducted more slowly through the ventricles than through normal conduction pathways. Meanwhile, the atrial cycle continues independently. No ectopic P wave is present. A P wave may occur either directly before or after the QRS but does not bear any relationship to it.
The sinus rhythm resumes again as scheduled. Figure 6. Ventricular ectopics may be isolated or may be a few in a row. More than six ventricular ectopics in a row constitute a ventricular tachycardia see Chapter 5. Ventricular ectopics may be positive or negative complexes. To find out which they are, you need to view lead V1 of your ECG or rhythm strip. If the QRS complex of the ectopic is negative, the impulse must be travelling towards the left and therefore coming from the right.
When some ectopics seen on a rhythm strip are positive and some are negative, they are collectively referred to as multifocal ectopics. Bigeminy is a term used to describe an arrhythmia in which every other beat is a ventricular ectopic. Isolated ventricular ectopics have little effect on the pumping action of the heart and usually do not cause symptoms, unless they are frequent.
They tend not to be dangerous for people who do not have a heart disorder. However, when they occur frequently in people who have structural heart disease, they may be followed by life-threatening arrhythmias such as ventricular tachycardia and ventricular fibrillation see Chapter 5. When a ventricular ectopic falls so early that it interrupts the T wave of the preceding complex there is a high risk of ventricular tachycardia or fibrillation. The apex of the T wave is a vulnerable phase in the ventricular cycle.
If stimulated by an ectopic, it may produce repeated ventricular responses, leading to these life-threatening arrhythmias. This is known as the R on T phenomenon. The most common causes of ventricular ectopics are hypokalaemia and ischaemia, particularly in the early stages of myocardial infarction, when the ventricles are irritable. Indeed if you watch a monitor of a patient who is starting to get ischaemic chest pain, it is common to see ventricular ectopics appearing on the tracing.
Ventricular ectopics are not usually treated if the patient is asymptomatic, as anti-arrhythmic drugs can also be pro-arrhythmic. These medications should therefore only be used for patients with symptoms. Atrial ectopics Atrial ectopics are premature contractions that originate in the atria but not in the SA node. The atria are depolarised from a different direction from normal. The ectopic P wave therefore has a different shape or morphology from the sinus P wave. Sometimes the ectopic P wave gets caught in the T wave of the preceding beat, and this causes it to distort the shape of the T wave.
At other times, if the ectopic originates near the AV node, the P wave is inverted or even absent. Ventricular depolarisation continues as usual, inscribing a normal width QRS complex. Atrial ectopics may appear in isolation or there may be a few in a row, which then go on to develop into an atrial arrhythmia. However, if the ectopics are becoming frequent this may indicate the onset of an atrial arrhythmia. Other causes of atrial arrhythmia can include: anxiety; stimulants such as caffeine, alcohol and excessive smoking; atrial hypertrophy; thyrotoxicosis and electrolyte disturbances.
Atrial ectopics do not usually require treatment. Look at the three rhythm strips below. Identify any ectopic beats and state where in the heart they originate. The 12 lead ECG see fig 7. Each view of the heart is known as a lead. If we look at Figure 7. Those on the right-hand side of the page labelled V1—V6 are collectively known as the chest leads. When we looked at rhythm strips earlier, we saw what a rhythm strip should look like in normal circumstances.
This made it easier to go on and identify abnormalities on rhythm strips. We will take the same approach now with the 12 lead ECG, starting with normal readings and going on to look at abnormal readings. This is referred to as the polarity of the limb leads. We will now learn which ones should be positive and which ones should be negative. If an impulse travels away from an electrode, a negative QRS will be recorded. Figure 7.
We can see that the impulse is travelling directly towards Lead II and this is therefore the most positive QRS complex. It reflects the normal pathway of the impulse so it is usually the best lead to pick up the wave forms of the PQRST complex. All the limb leads except aVR are positive, as the impulse is travelling in their direction. Some are more positive than others because the impulse travels more directly towards some electrodes than others. The chest leads V1—V6 To understand what the chest leads should look like in a normal ECG, we need to start by looking back at the explanation of the QRS complex see p.
The way it is labelled actually depends upon the direction of the deflections. The first positive deflection from the baseline is called an R wave. The first negative deflection from the baseline is called a Q wave. A negative deflection after an R wave is called an S wave. It is possible to have more than one positive or negative deflection in a QRS complex. These are called R1 or S1 waves respectively. This knowledge helps us to identify how the chest leads look in a normal ECG.
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We look for R wave progression. In V1 there should be a tiny R wave positive deflection after the PR interval , in V2 this should be slightly bigger i. In V5 and V6 the R waves should start to lose their height see fig 7. The ECG either shows good R wave progression see fig 7. If a lead has no R wave it has Q waves instead. As we will learn later on p. This pattern in the V leads can be explained by the way the directions of the electrical impulses depolarise the heart. As we saw earlier, if an impulse travels towards an electrode there is a positive deflection on the ECG and if the impulse travels away from the electrode there is a negative deflection.
When the impulse reaches the septum it depolarises the septum from left to right. This is because the impulse descends the left bundle branch more rapidly than the right.
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Both ventricles are activated simultaneously. However the wall of the right ventricle is much thinner than the left so the impulse travels through the right ventricular wall to the epicardium before the impulse on the left reaches the epicardium. The R wave becomes progressively taller from V1 to V4. The S wave becomes smaller until it disappears completely in V6.
There is a small R wave in V1 as expected but it does not increase in size through successive leads. However, it does look normal in lead V6. The S wave is deep in leads V1 to V4 and only reduces in size by a small amount. When the impulse reaches the right ventricle it is also travelling towards the V1 electrode and therefore increases the positive deflection. The next impulse activating the left ventricle is travelling away from V1 and therefore produces a negative deflection an S wave.
This explains why we get a small R wave in V1, followed by an S wave. The V2 electrode is closer to the septum. Therefore, as the initial impulse has less distance to travel to the electrode, the R wave is more positive. In V3 the electrode is closer still; and in V4, which is situated on the septum, you will find the tallest R wave. V5 and V6 sit on the left of the septum so the initial impulse is travelling away from the electrode. This results in a small negative deflection Q wave as the initial deflection. The following activities will reinforce this learning so that you are better able to recognise normal and abnormal QRS complexes.
Activity 7. Approximate time required to complete this activity: 5 minutes Answers are provided on p. They are presented here in the wrong order. This could be the one that you took in Chapter 1 or any ECG that you have recorded since. Describe the complex e. We have also seen how the direction of this impulse and the position of electrodes around the heart affect the polarity of the limb leads. However, there may be times when the normal pathway of the impulse is disrupted, e. Such a disruption may cause the pathway of the impulse to deviate to the left or the right or in extreme cases back up to the direction from which it came.
This is known as axis deviation. This disruption will affect the polarity of the limb leads. If something is causing the impulse to travel back from where it came, the aVR may be positive on the ECG, rather than negative, because the impulse is now travelling towards the aVR. Meanwhile Lead II may be negative, as the impulse is now travelling away from the lead.
One way of working out axis deviation is therefore by looking at the polarity of two of the limb leads. This can be most easily done by assessing Lead I and the aVF. Therefore, if the ECG shows a normal axis deviation meaning that there is no disruption of the normal pathway of electrical activity both Lead I and the aVF should look positive see fig 8. Figure 8. Lead I and the aVF lead are negative. Note that the aVR is positive; the electrical impulses are therefore moving in the opposite direction from normal.
If the impulse deviates to the left, there is left axis deviation, Lead I is positive and the aVF is negative. Lead I is positive and the aVF is negative. Extreme axis deviation is the most worrying for a patient, then right axis deviation, and then left. In practice, axis deviation does not necessarily require any treatment in itself. However, it raises the question of what has caused the axis deviation in the first place. This can be done by plotting the axis on a graph called the Hexaxial Reference System see fig 8.
The first method that we learned will be adequate for the majority of ECGs that you will encounter. However, calculating axis deviation using the Hexaxial Reference System is useful if you encounter a Lead I and aVF that are equiphasic equally positive and negative. In addition, some complex arrhythmias can be distinguished from one another by the degree of axis deviation that is present.
The purpose of including the Hexaxial Reference System within this text is simply to help make sense of what looks like a complex diagram in many ECG books. Such diagrams can make learners think they have reached their limit with ECG interpretation! The Hexaxial Reference System is divided into degree segments.
The numbers at the bottom of the Hexaxial Reference System are positive and those at the top half, negative. If you look at Figure 8. Here the heart is superimposed onto the Hexaxial Reference System. In normal circumstances, the pathway of the impulse would flow through the conducting system directly towards Lead II. This falls within the normal axis deviation quadrant of the Hexaxial Reference System. If deviation is to the right, it would fall in the lower left-hand quadrant. And if the pathway of the impulse goes back to where it came from, it would travel towards the upper left quadrant, which represents extreme axis deviation.
Calculating axis deviation in degrees using the Hexaxial Reference System Here is a step-by-step method to follow: 1 Look at the ECG and decide, by looking at Lead I and Lead aVF, if it is a normal, left, right or extreme axis deviation. If lead 1 is equiphasic a complex that is as positive as it is negative , it is sufficient at this stage to say that it is either a left or a normal axis, for example.
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Remember: the smallest limb lead complex may not be equiphasic; you need to choose the lead that is both small and equiphasic. This is the axis deviation of the ECG. For example, Figure 8. Lead aVL is the smallest, equiphasic complex in the limb leads. We have already learned that if an impulse travels towards an electrode we get a positive deflection, and if it travels away from an electrode we get a negative deflection. If we travel at 90 degrees to an electrode, we get an equiphasic complex see fig 8.