ECG Flashcards
Small squire measures in ECG?
1 mm = 0.04 s
Large squire measures in ECG??
1 large 🔶= 5 small🔶 =0.2 s
How amplitude measures in ECG??
10 mm = 1 mv
How amplitude measures in ECG??
10 mm = 1 mv
P wave duration?
=0.12 s
3 small squires
What is the indication of wide or notched p wave and in which lead it appears?
Left trial enlargement
Lead 2
What is the duration of PR?
0.12 - 0.2 s
3-5 small squires
What is represented by PR interval?
Av conduction
spread of depolarization from the SA node to the ventricular muscle is shown by the PR interval
What is the cause of short PR interval less than 0.12 s?
Accessory pathway between atria and ventricle
What abnormalities in Wolff-Parkinson White Syndrome?
QRS/delta wave immediately follows the P-wave PR interval<0.12 sec
What are the Preexcitation syndrome??
🔶Lown-Ganong-LevineSyndrome
= LGL Syndrome
🔶 Wolff-Parkinson WhiteSyndrome =wpw syndrome
What are the abnormalities in Lown-Ganong-LevineSyndrome = LGL Syndrome
QRS immediately follows the P-wave PR interval< 0.12 sec
What is the meaning of ‘rhythm’??
❤️refer to the part of the heart which is controlling the activation sequence.
The normal heart rhythm, with electrical activation beginning in the SA node, is called ‘sinus rhythm.
Roles of QRS waves??
🔹If the first deflection is downward, it is called a Q wave.
🔹An upward deflection is called an R wave, regardless of whether it is preceded by a Q wave or not .
🔹Any deflection below the baseline following an R wave is called an S wave, regardless of whether there is a preceding Q wave
🔹Single downward deflection is QS pattern
What waves represent ventricular depolarization and contraction??
▪️▪️▪️ QRS complex represents depolarization, not contraction, of the ventricles – contraction is proceeding during the ECG’s ST segment
What pericordal leads correspond to RTV > anterioseptal
V1 V2 V3
What are the leads correspond to basal septum??
V2 V3
What are the leads correspond to Anteriolateral
V1-6
What are the leads correspond to lateral wall??
1 aVL V5 V6
What are the leads correspond to posterior wall??
V7 V8
What leads correspond to right ventricle ❓
RV4 RV4
Shape of QRS complex??
Depolarization
(a) moving towards the lead, causing a predominantly upward QRS complex. V5 V6
(b) moving away from the lead, causing a predominantly downward QRS complex. V1 V2 V3
(c) at right angles to the lead, generating equal R and S waves
V4
What 12 lead representation on the heart??
🔹Leads I, II and VL look at ➡️the left lateral surface of the heart, 🔹leads III and VF at ➡️ the inferior surface.
🔹lead VR looks➡️ at the right atrium.
🔹leads V1 and V2 look at the right ventricle.
🔹V3 and V4 look at the septum between the ventricles and the anterior wall of the left ventricle.
🔹V5 and V6 look at the anterior and lateral walls of the left ventricle
What is first degree heart block
delay somewhere along the conduction pathway, then the PR interval is prolonged.
What are the conditions that can cause first degree heart block ❓❓
sign of
🔹coronary artery disease
🔹 acute rheumatic carditis.
🔹digoxin toxicity
🔹 electrolyte disturbances.
What is the second degree heart block ❓❓
Sometimes excitation completely fails to pass through the AV node or the bundle of His.
➡️ When this occurs intermittently, ‘second degree heart block’ is said to exist.
What are the types of 2nd degree heart block ❓❓
There are three variations of this:
1* Wenckebach’ or ‘Mobitz type 1’
2Mobitz type 2
3alternate conducted and nonconducted atrial beats
What is are the abnormalities behind mobitz type 1 ❓
🔺progressive lengthening of the PR interval and then failure of conduction of an atrial beat, followed by a conducted beat with a shorter PR interval and then a repetition of this cycle.
What are the abnormalities in mobitz type 2 ❓❓
🔺Most beats are conducted with a constant PR interval, but occasionally there is atrial depolarization without a subsequent ventricular depolarization. This is called the ‘Mobitz type 2’ phenomenon (Fig. 2.4).
What are the abnormality in type 3 2nd degree heart block ❓❓
🔺There may be alternate conducted and nonconducted atrial beats (or one conducted atrial beat and then two or three nonconducted beats), giving twice (or three or four times) as many P waves as QRS complexes. This is called ‘2:1’ (‘two to one’), ‘3:1’ (‘three to one’) or ‘4:1’ (‘four to one’) conduction (Fig. 2.5).is important to remember that, as with any other rhythm, a P wave may only show itself as a distortion of a T wave
What are The underlying causes of second degree heart block ❓❓
The Wenckebach phenomenon is usually benign
🔹Coronary artery disease
🔹 Acute Rheumatic Carditis
🔹Digoxin toxicity
🔹Electrolyte disturbances
What is the pathophysiology of 3rd degree heart block ❓❓
Complete heart block (third degree block) is said to occur when atrial contraction is normal but no beats are conducted to the ventricles
➡️ When this occurs the ventricles are excited by a slow ‘escape mechanism, from a depolarizing focus within the ventricular muscle.
What are the Causes of Complete heart block ❓❓
🔺acute phenomenon in patients with myocardial infarction (when it is usually transient)
🔺 it may be chronic, usually due to fibrosis around the bundle of His. It may also be caused by the block of both bundle branches.
What are the ECG abnormalities in complete heart block ❓❓
➡️No relationship between P waves and QRS complexes
➡️∑ QRS complex rate is low
➡️Abnormally shaped QRS complexes, because of abnormal spread of depolarization from a ventricular focus
What is wide QRS complex indicate ❓❓
🔺 bundle branch block
🔺if depolarization begins within the ventricular muscle itself
What is block of both bundle branches / right /left bundle branch indicates ❓❓
➡️Block of both bundle branches has the same effect as block of the His bundle, and causes complete (third degree) heart block.
➡️Right bundle branch block (RBBB) often indicates problems in the right side of the heart, but RBBB patterns with a QRS complex of normal duration are quite common in healthy people.
➡️Left bundle branch block (LBBB) is always an indication of heart disease, usually of the left ventricle.
What is ECG abnormalities in RBBB ❓❓
RSR1 pattern in lead V1 and wide QRS with deep s wave in V6
🔺no conduction occurs down the right bundle branch but the septum is depolarized from the left side as usual, causing an R wave in a right ventricular lead (V1) and a small Q wave in a left ventricular lead (V6)
🔺 Excitation then spreads to the left ventricle, causing an S wave in lead V1 and an R wave in lead V6.
It takes longer than in a normal heart for excitation to reach the right ventricle
🔺. The right ventricle therefore depolarizes after the left. This causes a second R wave (R1) in lead V1, and a wide and deep S wave, and consequently a wide QRS complex, in lead V6 (Fig. 2.11).
What are ECG abnormalities in LBBB ❓❓
M pattern in lead V6
🔺conduction down the left bundle branch fails, the septum becomes depolarized from right to left, causing a small Q wave in lead V1, and an R wave in lead V6.
🔺The right ventricle is depolarized before the left, so despite the smaller muscle mass there is an R wave in lead V1 and an S wave (often appearing only as a notch) in lead V6.
🔺Subsequent depolarization of the left ventricle causes an S wave in lead V1 and another R wave in lead V6.
LBBB is associated with T wave inversion in the lateral leads (I, VL and V5–V6), though not necessarily in all of these.
What is the difference between RBBB VS LBBB❓❓
💛RBBB is best seen in lead V1, where there is an RSR1 pattern.
💛LBBB is best seen in lead V6, where there is a broad QRS complex with a notched top, which resembles the letter ‘M’ and is therefore known as an ‘M’ pattern . The complete picture, with a ‘W’ pattern in lead V1, is often not fully developed.
What is the cause of Left bundle branch block and what is the treatment ❓
aortic stenosis and ischaemic disease.
∑ If the patient is asymptomatic, no action is needed.
∑ If the patient has recently had severe chest pain, LBBB may indicate an acute myocardial infarction, and intervention should be considered.
Left axis deviation and right bundle branch block
∑ Indicates severe conducting tissue disease.
∑ No specific treatment needed.
∑ Pacemaker required if the patient has symptoms suggestive of intermittent complete heart block.
If both the right bundle branch and the left anterior fascicle are blocked what does the ECG show ❓❓
ECG shows RBBB and left axis deviation
This is sometimes called ‘bifascicular block’, and this ECG pattern obviously indicates widespread damage to the conducting system
What can influence The rate of discharge of the SA node ❓
▪️ vagus nerves
▪️ reflexes originating in the lungs.
What are the Causes of slow sinus rhythm (‘sinus bradycardia’) ❓
▪️ athletic training, ▪️fainting attacks, ▪️hypothermia ▪️myxoedema. ▪️immediately after a heart attack
fast sinus rhythm (‘sinus tachycardia’) can be associated with ❓❓
exercise, fear, pain, haemorrhage or thyrotoxicosis
Note ∑ One P wave per QRS complex ∑ Constant PR interval ∑ Progressive beat-to-beat change in the R–R interval
What are the ‘supraventricular’ rhythms❓❓
Sinus rhythm, atrial rhythm and junctional
the atrial muscle; the region around the atrioventricular (AV) node (this is called ‘nodal’ or, more properly, junctional)
What is the difference between supraventricular rhythm and ventricular rhythm ❓❓
💛In supraventricular the depolarization wave spreads to the ventricles in the normal way via the His bundle and its branches . The QRS complex is therefore normal, and is the same whether depolarization was initiated by Spread of the depolarization wave in supraventricular rhythms the SA node, the atrial muscle, or the junctional region.
💛In ventricular rhythms, on the other hand, the depolarization wave spreads through the ventricles by an abnormal and slower pathway, via the Purkinje fibres
The QRS complex is therefore wide and is abnormally shaped. Repolarization is also abnormal, so the T wave is also of abnormal shape
In supraventricular rhythm always QRS complex in normal except ❓❓
🔺supraventricular rhythm with right or left bundle branch block
🔺 the Wolff–Parkinson–White (WPW) syndrome, when the QRS complex will be wide
Abnormal rhythms arising in the atrial muscle, the junctional region or the ventricular muscle can be categorized as:
∑ bradycardias – slow and sustained
∑ extrasystoles – occur as early single beats
∑ tachycardias – fast and sustained
∑ fibrillation – activation of the atria or ventricles is totally disorganized.
What are Escape rhythms and with what condition it is associated ❓❓
🔺are not primary disorders, but are the response to problems higher in the conducting pathway.
▪️They are commonly seen in the acute phase of a heart attack, when they may be associated with sinus bradycardia.
▪️It is important not to try to suppress an escape rhythm, because without it the heart might stop altogether.
Ventricular escape rhythms can occur without complete heart block, and ventricular escape beats can be single
What is accelerated idioventricular rhythm ❓❓
▪️▪️The rhythm of the heart can occasionally be controlled by a ventricular focus with an intrinsic frequency of discharge faster than that seen in complete heart block.
▪️▪️often associated with acute myocardial infarction.
What is the treatment of accelerated idioventricular rhythm❓❓
is benign and should not be treated
Atrial escape ❓❓
After one sinus beat the SA node fails to depolarize
∑ After a delay, an abnormal P wave is seen because excitation of the atrium has begun somewhere other than the SA node
∑ The abnormal P wave is followed by a normal QRS complex, because excitation has spread normally down the His bundle
∑ The remaining beats show a return to sinus arrhythmia
What are the ECG abnormalities in junctional escape rhythm ❓❓
Sinus rhythm, rate 100/min ∑ Junctional escape rhythm (following the arrow), rate 75/min
∑ No P waves in junctional beats (indicates either no atrial contraction or P wave lost in QRS complex) ∑ Normal QRS complexes
What are the abnormalities in ventricular escape rhythm ❓❓
Note ∑ Regular P waves (normal atrial depolarization)
P QRS
∑ P wave rate 145/min ∑ QRS complexes highly abnormal because of abnormal conduction through ventricular muscle
∑ QRS complex (ventricular escape) rate 15/min
∑ No relationship between P waves and QRS complexes
What are the abnormalities in ventricular escape rhythm ❓❓
Note ∑ After three sinus beats, the SA node fails to discharge
∑ No atrial or nodal escape occurs ∑ After a pause there is a single wide and abnormal QRS complex (arrowed), with an abnormal T wave
∑ A ventricular focus controls the heart for one beat, and sinus rhythm is then restored
What is the ‘sinus arrhythmia ❓
Changes in heart rate associated with respiration are normally seen in young people.
Iis ventricular extrasystoles is dengerous ❓❓❓
Ventricular extrasystoles are common, and are usually of no importance. However, when they occur early in the T wave of a preceding beat they can induce ventricular fibrillation (see p. 79), and are thus potentially dangerous.
What is the meaning of extrasystole ❓❓
Any part of the heart can depolarize earlier than it should, and the accompanying heartbeat is called an extrasystole. The term ‘ectopic’ is sometimes used to indicate that depolarization originated in an abnormal location, and the term ‘premature contraction’ means the same thing.
What is the difference BTW extrasystole and an escape beat ❓❓
the difference is that an extrasystole comes early and an escape beat comes late.
In atrial tachycardia,
the atria depolarize faster than 150/min. The AV node cannot conduct atrial rates of discharge greater than about 200/min. If the atrial rate is faster than this, ‘atrioventricular block’ occurs, with some P waves not followed by QRS complexes.
What is Carotid sinus pressure effect❓❓
activates a reflex that leads to vagal stimulation of the SA and AV nodes. This causes a reduction in the
frequency of discharge of the SA node, and an increase in the delay of conduction in the AV node
What is the cause of ventricular tachycardia ❓❓
If a focus in the ventricular muscle depolarizes with a high frequency (causing, in effect, rapidly repeated ventricular extrasystoles)
This trace was recorded from lead V6, and the M pattern and inverted T wave characteristic of left bundle branch block are easily identifiable
If a patient with an acute myocardial infarction has broad complex tachycardia it will almost always be ventricular tachycardia. However, a patient with episodes of broad complex tachycardia but without an infarction
could have ventricular tachycardia, or supraventricular tachycardia with bundle branch block or the Wolff–Parkinson–White syndrome
following points may be helpful: 1. Finding P waves and seeing how they relate to the QRS complexes is always the key to identifying arrhythmias. Always look carefully at a full 12-lead ECG.
2. If possible, compare the QRS complex during the tachycardia with that during sinus rhythm. If the patient has bundle branch block when in sinus rhythm, the
75The rhythm of the heart
QRS complex during the tachycardia will have the same shape as during normal rhythm.
3. If the QRS complex is wider than four small squares (160 ms), the rhythm will probably be ventricular in origin.
4. Left axis deviation during the tachycardia usually indicates a ventricular origin, as does any change of axis compared with a record taken during sinus rhythm.
5. If during the tachycardia the QRS complex is very irregular, the rhythm is probably atrial fibrillation with bundle branch block
No P waves, and an irregular baseline ∑ Irregular QRS complexes ∑ Normally shaped QRS complexes ∑ In lead V1, waves can be seen with some resemblance to those seen in atrial flutter – this is common in atrial fibrillation
VENTRICULAR FIBRILLATION
When the ventricular muscle fibres contract independently, no QRS complex can be identified, and the ECG is totally disorganized
Wolff–Parkinson–White syndrome. The accessory bundles form a direct connection between the atrium and the ventricle, usually on the left side of the heart, and in these bundles there is no AV node to delay conduction. A depolarization wave therefore reaches the ventricle early, and ‘pre-excitation’ occurs. The PR interval is short, and the QRS complex shows an early slurred upstroke called a ‘delta wave
The Wolff–Parkinson–White syndrome Note ∑ Sinus rhythm, rate 125/min ∑ Right axis deviation ∑ Short PR interval ∑ Slurred upstroke of the QRS complex, best seen in leads V3 and V4. Wide QRS complex due to this ‘delta’ wave ∑ Dominant R wave in lead V1
- Patients with any bradycardia that is affecting the circulation can be treated with atropine, but if this is ineffective they will need temporary or permanent pacing (Fig. 3.30).
The first treatment for any abnormal tachycardia is carotid sinus pressure. This should be performed with the ECG
running, and may help make the diagnosis: – Sinus tachycardia: carotid sinus pressure causes temporary slowing of the heart rate.
– Atrial and junctional tachycardia: carotid sinus pressure may terminate the arrhythmia or may have no effect.
– Atrial flutter: carotid sinus pressure usually causes a temporary increase in block (e.g. from 2:1 to 3:1).
– Atrial fibrillation and ventricular
tachycardia: carotid sinus pressure has no effect.
6. Narrow complex tachycardias should be treated initially with adenosine.
7. Wide complex tachycardias should be treated initially with lidocaine.
Pacemaker
Note ∑ Occasional P waves are visible, but are not related to the QRS complexes
∑ The QRS complexes are preceded by a brief spike, representing the pacemaker stimulus
∑ The QRS complexes are broad, because pacemakers stimulate the right ventricle and cause ‘ventricular’
All supraventricular rhythms have normal QRS complexes, provided there is no bundle branch block or pre-excitation (WPW) syndrome.
∑ Ventricular rhythms cause wide and abnormal QRS complexes, and abnormal T waves.
Is the abnormality occasional or sustained? 2. Are there any P waves? 3. Are there as many QRS complexes as P waves?
4. Are the ventricles contracting regularly or irregularly?
5. Is the QRS complex of normal shape? 6. What is the ventricular rate?
What are the features of left ventricular hypertrophy ❓❓
🔺 S ( V1 or V2)
🔺R (V5 OR V6)
S+R = 35mm=3.5mv
Sometimes excitation completely fails to pass through the AV node or the bundle of His.
➡️ When this occurs intermittently, ‘second degree heart block’ is said to exist.
What are the types of 2nd degree heart block ❓❓
There are three variations of this:
1* Wenckebach’ or ‘Mobitz type 1’
2Mobitz type 2
3alternate conducted and nonconducted atrial beats
What is are the abnormalities behind mobitz type 1 ❓
🔺progressive lengthening of the PR interval and then failure of conduction of an atrial beat, followed by a conducted beat with a shorter PR interval and then a repetition of this cycle.
What are the abnormalities in mobitz type 2 ❓❓
🔺Most beats are conducted with a constant PR interval, but occasionally there is atrial depolarization without a subsequent ventricular depolarization. This is called the ‘Mobitz type 2’ phenomenon (Fig. 2.4).
What are the abnormality in type 3 2nd degree heart block ❓❓
🔺There may be alternate conducted and nonconducted atrial beats (or one conducted atrial beat and then two or three nonconducted beats), giving twice (or three or four times) as many P waves as QRS complexes. This is called ‘2:1’ (‘two to one’), ‘3:1’ (‘three to one’) or ‘4:1’ (‘four to one’) conduction (Fig. 2.5).is important to remember that, as with any other rhythm, a P wave may only show itself as a distortion of a T wave
Rss
R V1 >=0.5mm
S V1 (R/S) >= 1
S V5 >=0.5 mm
What are the types of 2nd degree heart block ❓❓
There are three variations of this:
1* Wenckebach’ or ‘Mobitz type 1’
2Mobitz type 2
3alternate conducted and nonconducted atrial beats
What is are the abnormalities behind mobitz type 1 ❓
🔺progressive lengthening of the PR interval and then failure of conduction of an atrial beat, followed by a conducted beat with a shorter PR interval and then a repetition of this cycle.
What are the abnormalities in mobitz type 2 ❓❓
🔺Most beats are conducted with a constant PR interval, but occasionally there is atrial depolarization without a subsequent ventricular depolarization. This is called the ‘Mobitz type 2’ phenomenon (Fig. 2.4).
What are the abnormality in type 3 2nd degree heart block ❓❓
🔺There may be alternate conducted and nonconducted atrial beats (or one conducted atrial beat and then two or three nonconducted beats), giving twice (or three or four times) as many P waves as QRS complexes. This is called ‘2:1’ (‘two to one’), ‘3:1’ (‘three to one’) or ‘4:1’ (‘four to one’) conduction (Fig. 2.5).is important to remember that, as with any other rhythm, a P wave may only show itself as a distortion of a T wave
What is partial right bundle branch block ❓❓
An ‘RSR1’ pattern, with a QRS complex of normal width (less than 120 ms). It is seldom of significance, and can be considered to be a normal variant.
What is the rate of ventricular tachycardia ❓❓
Ventricular tachycardia should not be diagnosed unless the heart rate exceeds 120/min.
