ECG interpretation - arryhthmias, BBB etc Flashcards
List the main supraventricular arryhthmias
Supraventricular tachycardia:
- Atrial Fibrillation
- Atrial Flutter
- Ectopic atrial tachycardia
Bradycardia:
- Sinus bradycardia
- Sinus pauses
List the main ventricular arryhthmias
- Ventricular ectopics or Premature Ventricular Complexes (PVC)
- Ventricular Tachycardia (VT)
- Ventricular Fibrillation (VF)
- Asystole
List the main AV node arryhthmias
AVN re-entry tachycardia (AVNRT)
AV reciprocating or AV Reentrant tachycardia (AVRT)
AV block:
- 1st degree
- 2nd degree
- 3rd degree
List the clinical causes of arryhthmias
Abnormal anatomy:
- left ventricular hypertrophy
- accessory pathways
- congenital HD
Autonomic nervous system (ANS):
- Sympathetic stimulation: stress, exercise, hyperthyroidism
- Increased vagal tone causing bradycardia
Metabolic:
- Hypoxia: chronic pulmonary disease, pulmonary embolus
- Ischaemic myocardium: acute MI, angina
- Electrolyte imbalances: K+, Ca 2+, Mg2+
Inflammation: viral myocarditis
Drugs: direct electrophysiologic effects or via ANS
Genetic: mutations of genes encoding cardiac ion channels e.g. the congenital long QT syndrome
What are the common symptoms of arryhthmias ?
- Palpitations, ”pounding heart”
- Shortness of breath
- Dizziness
- Loss of consciousness; ”Syncope”
- Faintness: “presyncope”
- Sudden cardiac death
- Angina, heart failure
What are the 1st line investigations to be done on someone presenting with a possible arryhthmia ? (will commonly present with palpatations)
- 12-lead ECG:
- TFT’s - thyrotoxicosis may precipitate atrial fibrillation and other arrhythmias
- Urea and electrolytes: looking for disturbances such as a low potassium
- FBC
- CXR
First-line investigations are often normal in patients complaining of palpitations. The next step is to exclude an episode arrhythmia, what investigations should now be done ?
Most commonly a 24hr Holter ECG is done - patients are asked to keep a diary to record any symptomatic palpitations. This can later be compared to the rhythm strip at the time of the symptoms
Others which may be done include:
- Excercise ECG
- Electrophysiological study
What is the characteristic sign seen on ECG suggestive of WPW syndrome ?
Slurred upstroke (delta wave)
What does an excericse ECG allow you to assess?
- To assess for ischaemia
- Exercise induced arrhythmia
What does echocardiography allow you to assess?
Assess for structural disease of the heart e.g:
- Enlarged atria in AF
- LV dilatation
- Previous MI scar, aneurysm
What is able to be done at the same time of studying the arryhthmia on electrophysiological study ?
Opportunity to treat the arrhythmia by delivering radiofrequency ablation to extra pathway
When analysing the rhythmn of an ECG what are the 6 steps you should analyse?
- Is there electrical activity?
- Is the rhythm regular or irregular?
- What is the HR?
- Are the P-waves present?
- What is the relationship between the P and QRS complexes?
- What is the QRS duration?
How do you determine if there is normal sinus rhythm on an ECG ?
Check there is a p wave for every QRS complex and that the PR interval is < 200ms
How do you determine if an arryhthmia is supraventricular or ventricular in origin ?
- A supraventricular arryhthmia has a narrow QRS complex
- A ventricular arryhthmia has a broad QRS complex (>120ms)
What is shown in this ECG and explain if it is a problem or not
Normal sinus arryhthmia - it is normal and caused by Inspiration reducing vagal tone and increasing HR.
Define what sinus bradycardia is
rate < 60 beats/min (pwaves and QRS complexes normal)
What are the causes of sinus bradycardia ?
- Physiological i.e., athlete
- Drugs (B-Blocker)
- Ischaemia : common in inferior STEMIs
What is the treatment of sinus bradycardia ?
- If asymptomatic & rate >40bpm then no treatment, but stop causative factors e.g. drugs.
- If symptomatic or rate is <40bpm 1st line = IV atropine
- 2nd line = temoprary cardiac pacing required if haemodynamic compromise: hypotension, CHF, angina, collapse
Define a sinus tachycardia
HR > 100 beats/min (note the p wave and QRS are both normal)
What are the causes of sinus tachycardia ?
- Physiological (Anxiety, fever, hypotension, anaemia, excerise, stimulants e.g. caffeine, nicotine etc)
- Inappropriate (drugs, etc)
What is the treartment of sinus tachycardias ?
Treat underlying cause /lifestyle changes +/- Beta-blockers
What are the 3 types of AF?
- Paroxysmal - lasts < 48hrs, often recurrent
- Persistent - lasts > 48hrs but is able to be cardioverted back to normal sinus rhythm (unlikely to spontaneously revert to NSR)
- Permanent (chronic) - Inability of pharmacologic or non-pharmacologic methods to restore NSR
What are the 3 ways in which AF may be terminated and reverted back to normal sinus rhythm (NSR)?
- Pharmacologic cardioversion with anti-arrhythmic drugs (30% effective)
- Electrical Cardioversion (90% effective) by direct current (DCCV)
- Spontaneous reversion to sinus rhythm
List the possible causes of AF
- Hypertension
- Congestive heart failure
- Sick sinus syndrome - ‘tachy brady syndrome’
- Coronary heart disease
- Obesity
- Thyroid disease
- Familial
- Cardiac Valve disease
- Alcohol abuse
- Congenital heart disease
- Cardiac surgery
- COPD, Pneumonia,
- Septicaemia,
- Pericarditis, tumors
- Vagal cause – high endurance athletess
Define what idopathic (lone) AF is
This is AF in the absence of any heart disease and no evidence of ventricular dysfunction ==> diagnosis of exclusion
What are the symptoms of AF ?
- Palpitations
- Pre-syncope (dizziness)
- Syncope
- Chest pain
- Dyspnea
- Sweatiness
- Fatigue
Basically the same as any other arryhthmia
What ECG features are characterisitic of atrial fibrillation ?
- Irregularly irregular QRS complexes (distance between them)
- Absent p waves
What ECG abnormality is shown ?
AF
What are the 2 different approaches for the management of AF ?
- Rhythm control - aim is to maintain SR
- OR Rate control - aim is to accept AF but control ventricular rate
Anti-coagulation for both approaches if high risk for thromboembolism
What is the treatment of new onset AF with haemodynamic instability ?
1st line = emergency electrical cardioversion (do not delay this to achieve anticoagulation)
What is the preferred treatment of AF if the onset is > 48hrs or is uncertain and they are haemodynamically stable?
Rate control
When is rate control not the preferred treatment method of AF ?
If there is co-existent heart failure, first onset AF or where there is an obvious reversible cause of the AF (do rhythm control here)
What is the stepwise options for rate control of AF ?
- 1st line = standard Beta-blocker (but not sotalol) or a rate-limiting CCB (diltiazem or verapamil)
- 2nd line = combination of any of the following 3; Beta-blocker (but not sotalol), diltiazem or digoxin
- 3rd line = Rhythm control
Why is digoxin not a 1st line option for rate control of AF?
Because it is less effective at controlling rate in exercise and ==> better for very sedentry people
What are the 2 ways in which rhythm control of AF is achieved
- Pharmacological cardioversion
- Electrical cardioversion (DC)
Prior to doing rhythm control in patients other than those previously mentioned needing emergency DC cardioversion, what needs to be ensured prior to cardioversion ?
That the patient has either been anticoagulated or their symptom onset was < 48hrs prior to attempting cardioversion
What is the stepwise options for rhythm control ?
- 1st line in patients where AF present > 48hrs = electrical cardioversion
- 2nd line = pharmacological cardioversion with flecainide or amiodarone
What should electrical cardioversion not be attempted before (unless emergency)
Until ≥ 3 wks of anticoagulation or a transoesophageal echo is done to exclude a left atrial thrombus (if this is done then can immediately heparinise & cardiovert)
Following cardioversion what may be required to maintain NSR ?
- 1st line = standard beta-blocker
- 2nd line = amiodarone or flecainide mainly (or sotalol)
When should amiodarone or flecainide be used over oneanother ?
- Amiodarone used if patient has structural heart disease
- Flecainide if they dont have it
If an AF patient is at high risk of cardioversion failure, what should they take prior ?
Amiodarone or sotalol for ≥ 4wks
Following cardioversion of someone with AF what should be given for at least ≥ 4wks ?
Anticoagulation & then decision to continue based on the standard AF risk assessment
The treatment of atrial flutter has the same principles as AF (rate vs rhythm control) however atrial flutter does not respond as well to drug treatment as AF.
When is rate control usually used in atrial flutter treatment then ?
As an interium measure prior to restoration of NSR
What are the stepwise options for rate control of atrial flutter?
- 1st line = beta-blocker (but not sotalol) or CCB (diltiazem or verapamil)
- 2nd line = may add digoxin, it can be useful for those in heart failure
Rhythm control is preferred as the treatment of atrial flutter, what is the stepwise options ?
- 1st line for when rapid conversion to NSR needed i.e. when associated with haemodyanmic compromise = electrical cardioversion (usually DC)
- 1st line for recurrent atrial flutter = catheter ablation
If electrical cardioversion not done as emergency then need to follow same guidelines on anticoagulating or doing a TOE prior same as in AF
Pharma cardioversion has limited effect
What should all patients with AF be assessed for risk of and how ?
- Risk of stroke (thrombus) & ==> the need for anticoagulation
- Done using the CHA2DS2-VASc score (note this needs to be weighed against risk of bleeding using the HASBLED score)
A CHA2DS2-VASc score of what required anticoagulation ?
What should patients with AF or atrial flutter requiring anticoagulation be offered?
A choice between warfarin or NOAG unless valvular AF then warfarin preferred
What are the characterisitic features on ECG of atrial flutter ?
- A regular narrow complx tachycardia
- Sawtooth baseline
- Rate is a division of 300 (usually 150, but can be 100, 75 etc)
- Best seen in V1 or lead II
What ECG abnormality is shown here ?
Atrial flutter
What are the characterisitc features of junctional rhythms?
- Regular rhythm
- No p waves prior to QRS complex, instead they are seen following the ARS complex in the ST segment and are inverted
- Narrow QRS complex unless co-exisitent L or RBBB
- May have a normal, bradycardic or tachycardic rate
What are SVT’s usually caused by?
- AV nodal re-entrant tachycardia (AVNRT)
- AV reciprocating tachycardia / AV reentrant tachycaria (via an accessory pathway) (AVRT) i.e. Wolf-parkison white
- Ectopic atrial tachycardia (EAT)