Arrhythmia Flashcards
Cardiac causes [6]
Ischemic heart disease
Structural changes
Cardiomyopathy
Pericarditis
Myocarditis
Aberrant conduction pathways (WPW syndrome)
Non cardiac causes [5]
Electrolyte imbalance
Metabolic - hypoxia/acidosis/thyroid
Caffeine, Smoking, Alcohol
Pneumonia, phaeochromocytoma
Drugs
Drugs that cause arrhythmia [5]
Levodopa
Digoxin
Beta 2 agonists (asthma drugs)
Tricyclic antidepressants
Doxorubicin
Presentation [7]
Palpitations
Dyspnoea
Chest pain
Fatigue
syncope/presyncope
Pulmonary oedema
Can be asymptomatic
Initial mx of arrhythmias [6]
ABCDE
Oxygen
Gain IV access
12 lead ECG
Correct metabolic abnormalities
Classify patient as stable or unstable
What is a sinus arrhythmia? [3]
Management?
Normal conduction at faster frequency
HR increases inspiration
Decreases expiration
No Rx needed
Causes of sinus arrhythmia [7]
Infection, fever
dehydration, hypovolaemia
pain / exercise
drugs, salbutamol
adrenaline
PE
hypothyroid
MI
Categorisation of tachyarrhythmias
Supraventricular - narrow complex
Ventricular - broad complex
Sinus tachycardia
Features suggesting VT rather than SVT with aberrant conduction
AV dissociation
fusion or capture beats
positive QRS concordance in chest leads
marked left axis deviation
history of IHD
lack of response to adenosine or carotid sinus massage
QRS > 160 ms
What is a narrow complex tachycardia and why? [4]
> 100BPM
QRS <120
Short P wave
Ventricles depolarised via normal pathway so QRS normal
Types of regular narrow complex tachycardias [5]
Regular
* Sinus tachycardia
* Atrial tachycardia (unifocal)
* Atrial flutter
* AV re-entry tachycardia (WPW pattern)
* AV nodal re-entrant tachycardia (AVNRT)
Multifocal atrial tachycardia
Definition? Demographic it is more common in
Multifocal atrial tachycardia (MAT) may be defined as a irregular cardiac rhythm caused by at least three different sites in the atria, which may be demonstrated by morphologically distinctive P waves. It is more common in elderly patients with chronic lung disease, for example COPD
How is multifocal atrial tachycardia managed?
correction of hypoxia and electrolyte disturbances
rate-limiting calcium channel blockers are often used first-line
cardioversion and digoxin are not useful in the management of MAT
What is WPW [2]
ECG [2]
AV re-entrant tachycardia - another pathway through atrial and ventricle not AV node
Complications: AF, VF
ECG:
- short PR interval
- wide QRS complexes with a slurred upstroke - ‘delta wave’
What causes irregular narrow complex [3]
Irregular NCT
* AF
* Atrial flutter with irregular block
* Multifocal atrial tachycardia
What is associated with WPW [4]
HOCM
Mitral valve prolapse
Ebstein
Thyrotoxicosis
APs can be left-sided or right-sided, and ECG features will vary depending on this:
Describe ECG features in Type A vs Type B
Left-sided AP: produces a positive delta wave in all precordial leads, with R/S > 1 in V1. Sometimes referred to as a type A WPW pattern
Right-sided AP: produces a negative delta wave in leads V1 and V2. Sometimes referred to as a type B WPW pattern
Localisation of the aberrant accessory pathway in AVRT
The closer the accesory pathway is to the sinoatrial node or site of atrial ectopy, the greater the degree of pre-excitation.
Pathway originating from right free wall
* shortened PR interval
* broader QRS
Pathway originating from left free wall
* more normal ECG
Orthodromic vs Antidromic AVRT
Orthodromic
* Atrial ectopic beat is propagated in usual anterograde fashion, then retrograde conduction occurs along aberrant accessory pathway.
Antidromic
* If ventricular ectopic is propagated in a retrograde fashion via myocardial cells not usual conduction system, this results in a boarder QRS - this may resemble VT.
Management of AVRT and AVNRT are similar
AVNRT
* Paroxysmal AVNRT - transient AV node blockade using verapamil, BB, verapamil. These induce block along slow pathway.
* Infrequent symptoms but clear onset, prescribe PRN flecainide.
* Definitive mx includes catheter ablation of the slow pathway.
Pathophysiology in AVNRT
AV NODAL re-entry
* Congenital abnormality where AVN has dual physiology - fast and slow circuits.
* Premature atrial complex occurs when fast pathway is in refractory mode > so the electricity is conducted on slow pathway. Once the electricity goes along two pathways this creates a re-entry circuit.
Remember the major difference in AVRT vs AVNRT is
AVRT = WPW and is caused by a congenital ‘aberrant’ accessory pathway connecting atria and ventricles, NOT through the AV node.
In narrow complex tachycardias, what can you use instead of adenosine if contraindicated?
Adenosine is contraindicated in asthma
Another option is to use verapamil which slows AV nodal conduction
Management of supraventricular tachycardias
Acute management
1. vagal manoeuvres:
Valsalva manoeuvre: e.g. trying to blow into an empty plastic syringe
carotid sinus massage
2. intravenous adenosine
rapid IV bolus of 6mg → if unsuccessful give 12 mg → if unsuccessful give further 18 mg
3. electrical cardioversion
Prevention of episodes
* beta-blockers
* radio-frequency ablation
What is the Valsalva manoeuvre [5]
Forced expiration against closed glottis Increases intrathoracic pressure Reduced venous return due to increased atrial pressure Reduced preload Reduced CO