Uni content ECGs Flashcards
Describe the following rhythm, its mechanism, features, management
Atrial flutter is a narrow complex tachycardia.
It is a “regularly irregular” pattern.
Characteristics
- regular atrial activity at 300 bpm
- loss of isoelectric line
- upright flutter waves in V1 that may resemble P waves
- can be typical (with sawtooth appearance, especially in leads II, III, aVF, tricuspid/mitral isthmus)
- or atypical (CHD, damage)
Mechanism
Atrial flutter is a form of SVT caused by a re-entry circuit within the right atrium.
Typical atrial flutter
- is more common
- it involved the IVC and tricuspid isthmus in the re-entry circuit
- it can be further classified based on whether the direction of the re-entry circuit is anticlockwise or clockwise
- anticlockwise re-entry: commonest form of atrial flutter, produces inverted flutter waves in leads II, III and aVF; and positive flutter waves in V1 that may resemble upright P waves
- clockwise re-entry: opposite pattern to anticlockwise re-entry
Atypical atrial flutter
- often associated with rhythm instability, higher atrial rates, and less amenable to treatment with ablation
Management
Note: atrial flutter and fibrillation are treated the same, for example, beta blockers, calcium channel blockers, amiodarone or sotalol, cardioversion ^[quick, low energy shocks to restore rhythm, synchronised to QRS complex] and radiofrequency ablation (but flutter is more refractory to treatment)
Note 2: similarly, CHAD score is used to assess risk
Identify the following arrhythmia, briefly describe its features, mechanism, complications and management
This is an example of atrial fibrillation.
AF is the most common cardiac arrhythmia characterized by a chaotic heart rhythm, or “disorganised atrial electrical activity and contraction resulting in an irregularly irregular ventricular responses a.k.a fibrillation waves”.
Characteristics
Key points about AF are:
- Absence of P wave on 12-lead ECG
- Lasts for >30 seconds
- AF can be acute, transient, paroxysmal, or chronic
- Patients may be stable or unstable
- Has multiple possible underlying causes
- Prevalence increases with age
- It is a common occurrence post cardiac surgery
Mechanism of AF
AF can be triggered by various factors:
- Atrial distension as a results of pulmonary hypertension (Pulmonary vein triggers), septal defects and valvular disease e.g. mitral stenosis including infective endocarditis (80%)
- Non-PV triggers: abnormalities of the conducting system, increased atrial automaticity or irritation i.e. due to alcohol, caffeine, myocarditis, electrolyte derangement
- Substrate i.e. catecholamine excess or increased sensitivity - which can be sourced exogenously or endogenously
Complications
Complications of atrial fibrillation can be broadly categorised into two types:
- adverse effects on haemodynamics, including loss of atrial systole, decreased diastolic filling time due to tachycardia, and rate-related cardiomyopathy
- atrial thrombus formation: including systemic embolism especially stroke, and pulmonary embolism
Management of AF
The management of AF involves several considerations:
- Recorded 12-lead ECG to identify atrial fibrillation and associated disease
- Anticoagulation issues
- Assess Thromboembolic (TE) Risk, treated with warfarin or NOAC
- Rate and Rhythm control
- AF type symptoms
- Treatment of underlying disease
- Consider referral
- Treat with ACEIs, ARBs, CPAP, or others depending on comorbidities or underlying causes
Describe the following pattern, its characteristics, and its types
AV Nodal Reentrant Tachycardia or AVNRT
Definition
- a type of paroxysmal SVT that is te consequence of a re-entry circuit within or adjacent to the AV node
- it is the most common cause of palpitations in patients with structurally normal hearts
Characteristics
- characterized by a fixed, short RP interval mimicking r’ deflection.
Like other SVTs, AVNRT can be categorised based on location and regularity:
- typically ECG shows heart rate between 140 and 280 bpm
- location: AV node
- regularity: regular
There are several types of AVNRT:
- Slow-fast AVNRT: pseudo- S in II, III and aVF, and pseudo R’ in V1
- Fast-slow AVNRT: P waves between QRS and T
- slow-slow AVNRT: late P waves after QRS, appears as atrial tachycardia
slow fast shown
Describe the following pattern, its characteristics, and its types
AVRT
AVRT: Accessory Pathway and Ventricular Preexcitation (Wolff-Parkinson-White Syndrome)
Definition
AVRT is a form of paroxysmal SVT that occurs in patients with accessory pathways. This is usually a result of a re-entry circuit between the AVN and accessory pathways. ECG features depend on whether conduction is orthodromic or antidromic.
Characteristics
- congenital
- present anywhere in heart
- PR interval short, due to fast conduction
- when symptomatic, leads to WPW syndrome
- slurring of QRS leads to **delta wave
Orthodromic AV Reentrant Tachycardia
Anterograde conduction via the AVN, producing a narrow complex rhythm (antidromic, via AP, produces regular wide complex rhythm).
Characteristics
- rate usually 200-300 bpm
- retrograde P waves usually visible, with long RP interval
- narrow QRS
- rate-related ischaemia common
ORTHODROMIC SHOWN
Describe the following arrhythmia, its causes, characteristics
Torsade de Pointes
Definition
a specific type of polymorphic VT with a prolonged QT interval
Characteristics:
- both PVT and QT prolongation must be present
- it has a characteristic morphology in which the QRS complexes “twist” around the isoelectric line
Cause:
- A prolonged QT reflects prolonged myocyte repolarisation due to ion channel malfunction
- This prolonged repolarisation period also gives rise to early after-depolarisations (EADs)
- EADs may manifest on the ECG as tall U waves; if these reach threshold amplitude they may manifest as premature ventricular contractions (PVCs)
- TdP is initiated when a PVC occurs during the preceding T wave, known as ‘R on T’ phenomenon
- The onset of TdP is often preceded by a sequence of short-long-short R-R intervals, so called “pause dependent” TDP, with longer pauses associated with faster runs of TdP
Factors:
- ischemia
- dyselectrolytemia
- drugs
- LQTS (Long QT Syndrome).
Describe this arrhythmia, its characteristics and causes
Ventricular Fibrillation
Definition:
Ventricular fibrillation is described as a totally chaotic rapid ventricular rhythm, often precipitated by VT.
It is the most important shockable cardiac arrest rhythm.
Characteristics:
Can be marked by low blood pressure, hypoxia.
- Chaotic irregular deflections of varying amplitude
- No identifiable P waves, QRS complexes, or T waves
- Rate 150 to 500 per minute
- Amplitude decreases with duration (coarse VF –> fine VF)
Causes
- Electrical (electrocution, lightning, trauma)
- Ischaemia/hypoxic susceptibility (respiratory arrest)
- Electrolyte abnormality (low K and Mg)
- Altered autonomic and vagal inputs
- Mechanical stimuli (wire or catheter in RV)
- Congenital susceptibility (conduction abnormalities)
- Acquired disorders (ischaemia, hypertrophy, myocarditis, pro-arrhythmic drugs)
Treatment
Immediate treatment: shocking the patient, otherwise death.
Describe this rhythm and its features
Definition
Sinus Bradycardia is characterized by a slow depolarization of the sinus node.
It is usually seen as a resting heart rate of less than 60 bpm for adults, or below the reference range for children.
Characteristics
Looks exactly like sinus rhythm, with much longer RR intervals.
Causes
Can be pharmacological or non-pharmacological
* Hypothyroidism
* Drugs
* During vomiting or vasovagal syncope
* Increased intracranial pressure
* Hypoxia, hypothermia
* Infections
* Depression
* Jaundice
Can also be physiological – atheletes
Management
If the patient is symptomatic and the rhythm is persistent and irreversible, a pacemaker may be required.
Describe this rhythm and its characteristics
Sinus pause/arrest
Definition
Sinus Pause/Arrest involves the failure of the sinus node to discharge, resulting in periods of ventricular asystole.
Note arrest = pause greater than 3 seconds
Characteristics
- rate varies, typically slow
- rhythm = irrregular
- PP and RR intervals irregular
- P waves present except for pause
- P: QRS usually 1:1
- PR and QRS intervals of normal width
Mechanism
SAN dysfunction
Management
Pacemaker treatment may be necessary in some cases.
Describe this rhythm and its characteristics
Sinoatrial exit block
Definition
A consequence of failed propagation of pacemaker impulses beyond SAN.
Characteristics
- some dropped P waves, otherwise present
- rate varies, usually slow
- PP and RR irregular
- P: QRS usually 1:1
- PR and QRS intervals of normal width
Describe sinus arrest
Definition
* Failure of sinus node discharge
Characteristics
* Absence of atrial depolarization
* Periods of ventricular asystole
* May be episodic as in vaso-vagal syncope, or carotid sinus
hypersensitivity
Management
– May require a pacemaker
Describe chronotropic incompetence
Definition
In Chronotropic Incompetence, the heart rate is unable to increase adequately in response to the body’s metabolic demand, leading to limited activity and symptoms.
Cause
Chronotropic incompetence is often caused by SND, and is very common among heart failure patients.
NOTE: beta blcokers can increase chronotropic incompetence
Normal, healthy heart is able to increase peak cardiac output by up to 5x
baseline with exercise
* In chronotropic incompetence, patient may only be able to double cardiac
output over baseline
* An increase in stroke volume only may limit activity and
cause symptoms
Treatment
As with other bradyarrhythmias. Avoid BBs. Can be addressed with pacemaker.
Describe brady tachy syndrome
Definition
Brady/Tachy Syndrome presents with intermittent episodes of slow and fast rates from the SA node or atria, often associated with periods of atrial fibrillation and chronotropic incompetence.
Characteristics
- Brady < 60 bpm
- Tachy > 100 bpm
- Sinus Node Disease
– Most common pacing indication
Describe this arrhythmia and its characteristics
Definition
First-Degree AV Block is characterized by a prolonged PR interval (>200 ms) due to delayed conduction through the AV node. In most cases, it is not an indication for pacing.
Characteristics
- Delay between impulse generation and transmission to the atrium.
- Generally asymptomatic
Causes
- Increased vagal tone
- Athletic training
- Inferior MI
- Mitral valve surgery
- Myocarditis (e.g. Lyme disease)
- Electrolyte disturbances (e.g. Hyperkalaemia)
- AV nodal blocking drugs (beta-blockers, calcium channel blockers, digoxin, amiodarone)
- May be a normal variant
Treatment
Nothing specific required
Note: Some consider this a normal variant (not an arrhythmia)
Describe the following arrhythmia and its characteristics
Definition
Second-Degree AV Block, known as Mobitz I , or Wenckeback shows a progressive prolongation of the PR interval until there is a failure to conduct, resulting in a dropped ventricular beat. It is usually not an indication for pacing.
Characteristics
- usually 1:1 ratio
- PP remains relatively constant
- mostly asymptomatic
- Progressive prolongation of the PR interval culminating in a non-conducted P wave:
- PR interval is longest immediately before dropped beat
- PR interval is shortest immediately after dropped beat
Describe the following arrhythmia and its characteristics
Definition
Second Degree AV Block, known as Mobitz II, involves regularly dropped ventricular beats, indicating a high-grade block and is often an indication for pacing.
Characteristics
- no progressive prolongation of PR interval - remains constant
– 2:1 block (2 P-waves for every 1 QRS complex) aka The RR interval surrounding the dropped beat(s) is an exact multiple of the preceding RR interval (e.g. double the preceding RR interval for a single dropped beat, triple for two dropped beats, etc)
– Atrial rate = 75 bpm, Ventricular rate = 42 bpm
Cause
- Mobitz II is usually due to failure of conduction at the level of the His-Purkinje system (i.e. below the AV node)
- While Mobitz I is usually due to a functional suppression of AV conduction (e.g. due to drugs, reversible ischaemia), Mobitz II is more likely to be due to_structural_damage to the conducting system (e.g. infarction, fibrosis, necrosis)
Describe the following arrhythmia and its characteristics
Definition:
In third-degree AV block, there is no impulse conduction from the atria to the ventricles, resulting in complete atrioventricular disassociation. The atrial rate is indicated as 130 bpm, while the ventricular rate is 37 bpm. In most cases, complete heart block leads to a wide QRS, as the ventricular rate is idioventricular.
Characteristics:
- severe bradycardia
Causes
The causes are the same as for Mobitz I and Mobitz II second degree heart block.The most important aetiologies are:
- Inferior myocardial infarction
- AV-nodal blocking drugs (e.g. calcium-channel blockers, beta-blockers, digoxin)
- Idiopathic degeneration of the conducting system (Lenegre’s or Lev’s disease), causing true trifascicular block
Describe the following arrhythmia and its characteristics
Right bundle branch block
Characteristics
- QRS duration > 120ms
- RSR’ pattern in V1-3 (“M-shaped” QRS complex) - i.e. MARROW
- Sometimes rather than an RSR’ pattern in V1, there may be a broad monophasic R wave or a qR complex.
- Wide, slurred S wave in lateral leads (I, aVL, V5-6)
Causes of Right Bundle Branch Block
- Right ventricular hypertrophy / cor pulmonale
- Pulmonary embolus
- Ischaemic heart disease
- Rheumatic heart disease
- Congenital heart disease (e.g. atrial septal defect)
- Myocarditis
- Cardiomyopathy
- Lenègre-Lev disease: primary degenerative disease (fibrosis) of the conducting system
Management
- can be asymptomatic
- re-synchronisation is indicated in patients with CHF and RBBB ^[as per StatPearls]
Describe the following arrhythmia and its characteristics
Left BBB
Characteristics
- QRS duration > 120ms
- Dominant S wave in V1
- Broad monophasic R wave in lateral leads (I, aVL, V5-6) – WILLO (m)
- Absence of Q waves in lateral leads
- Prolonged R wave peak time > 60ms in leads V5-6
Interpret the following ECG
Sinus Rhythm. Normal ECG.
Interpret the following ECG
Sinus arrhythmia: due to changes in vagal tone associated with respiratory phase (increase HR in inspiration, decrease HR in expiration)
Interpret the following ECG
Atrial fibrillation with rapid ventricular response rate
Interpret the following ECG
Acute anterior wall STEMI, with Q waves in V1-3, and ST elevation in leads V1-5
Interpret the following ECG
Acute pericarditis
- prominent T waves
- diffuse ST elevation (I, II, III, aVF, V3-6)
Interpret the following ECG
Monomorphic ventricular tachycardia
- can be lifethretening
- most patients have significant heart disease e.g. CAD or CM
- does not invariably cause haemodynamic collapse–> patients may be conscious and stable
