Cardiac Arrhythmias Flashcards
what should you look for in your general approach to arrhythymias
- whether the heart rhythm is fast (tachycardia) or slow (bradycardia)
- you should see whether the patient is presenting acutely or electively
- you should see whether the arrhythmia is primary (the heart) or secondary (something else)
what is tachycardia
greater than 100bpm
What is bradycardia
less than 60bpm
How do you assess the patient with tachycardia and what do you do in unstable tachycardia
- Monitor SpO2 and give oxygen if they are hypoxic
- monitor ECG and BP and record 12 lead ECG
- obtain IV access
- identify and treat reversible causes
adverse features
- shock
- MI
- heart failure
- Syncope
- if you have these adverse features then this means that the tachycardia is unstable
- if the tachycardia is unstable you should administer a synchronised DC shock up to 3 times
What are the adverse features of tachycardia
- shock
- MI
- heart failure
- Syncope
What do you do in stable tachycardia
- Look to see if the QRS is narrow (at less than 0.12s)
-
What do you do in unstable tachycardia
adverse features
- shock
- MI
- heart failure
- Syncope
- if you have these adverse features then this means that the tachycardia is unstable
- if the tachycardia is unstable you should administer a synchronised DC shock up to 3 times
What determines the width of the QRS complex
using normal confusion system (his-purkinje system) to active ventricles
- tachycardia where ventricles are activated by a normal conduction system
Name how a narrow QRS complex is caused and define it
- ECG shows a rate of greater than 100bpm and a QRS complex duration of less than 120ms
- it is caused supra-ventricular tachycardia and this is due to a complication happening above the bundle of his and above the ventricles, occur when the ventricles are depolarised via normal conduction pathways
What is another name for a narrow QRS complex
Supra-ventricular tachycardia
Name the types of supra-ventricular tachycardia
- Atrial fibrillation/flutter/tachycardia
- Atrio-Ventricular Nodal Reentrant Tachycardia
- Atrio-Ventricular Reentrant Tachycardia
Why are Atrial fibrillation/flutter/tachycardia
grouped together as a type of ventricular tachycardia
- substrate from the arrhythmia originates from the atria themselves
What causes atrial flutter
- Counter clockwise circuit going through the right atria
What does Atrial flutter look like on the ECG wave
- Saw tooth P flutter waves - negative in the inferior leads
- 150bpm is the ventricular rate
what causes atrial fibrillation
- random depolarisation in different parts of the atrial fibrillation
What does the ECG look like of atrial fibrillation
- RR intervals are irregular
- lack of P waves
Describe the treatment for atrial fibrillation in stages
- Acute rate and rhythm control
- manage precipitating factors - lifestyle changes, treatment of underlying cardiovascular conditions
- assess stroke risk - oral anticoagulation in patients at risk for stroke
- rate control therapy
- antiarrhtymic drugs, cardioversion, catheter ablation, AF, surgery
Describe how you would decide what medication you would use for AF
if LVEF is greater than or equal to 40%
- beta blocker or dilitiazem or verapamil
- if this does not wokr add digoxin
- initial resting heart rate target is less than 110bpm
If LVEF is less than 40% or if there are sings of congestive heart failure
- smallest dose of beta blocker to achieve rate control
- add digoxin
- initial resting heart rate target is less than 110bpm
For both of these
- avoid bradycardia
- perform echocardiogram to determine further management/choice of maintenance therapy
- consider need for anticoagulation
Describe how the CHADVASC score works in assessing stroke risk in atrial firbillation
- Congestive heart failure = 1
- Hypertension = 1
- Age 65-74 =1, over 75 = 2
- Diabetes = 1
- Stroke or prior TIA = 2
- Vascular disease = 1
- S – female sex = 1
If the score is 0 = then no treatment
If the score is 1 = males: consider anticoagulation, females no treatment
If score is 2 or more than offer anticoagulation
What is used to work out the risk of stroke occurring in atrial fibrillation
(CHADSVASC score)
How do you treat atrial fibrillation
Rate control
- either with a beta blocker or a rate limiting calcium channel blocker (e.g. dilimiazem)
Rhythm control
- either cardio version or drug induced cardioversion with amodiarone
What causes atrial ventricular node re-entry tachyarrthymia
- this is a re-entrant circuit that develops around the AV node
- re entry within the AV node
- fast and regular
What happens in atrio-ventricular reentrant tachycardia
- this occurs in patients with pre-excitation
- accessory pathway that allows electrical activity in the ventricle which occurs with the normal electrical pathway
What does an ECG look like in atrio-ventricular reentrant tachycardia
- Delta wave
What is another word for atrio-ventricular reentrant tachycardia
Wolff-Parkinson white syndrome
- pre-excited ECG
- documented tachycardia/palpitation symptoms
- orthodromic AVRT
- the ventricle is activated down the pukinje his pathway and then goes up the accessory pathway
What happens in the orthodromic AVRT
- the ventricle is activated down the pukinje his pathway and then goes up the accessory pathway
- Narrow QRS complex
What happens in the antidromic AVRT
the ventricles are activated by the accessory pathway therefore the right side of the ventricle is activated first, the pathway then goes back up the bundle of His
- Broad QRS complex
What happens when there is atrial fibrillation in the top chambers and conducts down
- atrial fibrillation in the top chambers and is conducting down into the ventricles via the AV node and the accessory pathway
- fast
- broad
- irregular
- emergency - DC cardioversion and then need inpatient ablation
What happens when you ablate the accessory pathway
Delta waves disappear
What can you use to treat atrial ventricular node re-entry tachyarrthymia and atrio-ventricular reentrant tachycardia
- both of these tachycardia depend on the node
- therefore any vagal termination with vagal manoeuvre and adenosine can terminate the tachycardia
What happens if you have a narrow QRS complex and the rhythm is irregular
- have a narrow QRS complex
- If the rhythm is irregular it is probable AF
- control rate with a beta blocker or dilitiazem
- if in heart failure consider digoxin or amiodarone
- assess thromboembolic risk and consider anticoagulant
What happens if you have a narrow QRS complex and the rhythm is regular
- Narrow QRS complex
- rhythm is regular
- vagal manoeuvres
- adenosine 6mg rapid IV bolus - if no effect give 12mg if no effect give further 12 mg
- monitor/record ECG continuously
- check to see if sinus rhythm is achieved
- if no seek expert help - could be a possible atrial flutter - control rate with something like a beta blocker
- if yes
probably re-entry paroxysmal SVT - record 12 lead ECG in sinus rhythm
- if SVT recurs treat again and consider anti-arrhythmic prophylaxis
What does if mean if you have broad complex tachycardia
= ECG shows a rate of greater than 100bpm and QRS complexes greater than 120ms
- ventricular activation not via normal specialised conduction system
What happens in ventricular tachycardia
- Ventricular tachycarida
- this occurs in the ventricle when the ventricle is activated by somewhere else in the ventricle, now it is activated from one side to the other side resulting in a broad QRS complex
What happens in SVT with abberancy
- Bundle branch block causing QRS complex to become broad
- the bundle of his system does not work as it should
describe what happens in paced rhythm
- Paced rhythm
- place a pacing wire in the right ventricle and a pace rhythm
describe what happens in excited to make the QRS complex look broad
delta wave can make the QRS complex look broad
if the origin of the VT is
- LV
- RV or Septal LV
- Lateral LV
- RV or septal LV
- apex
- base
- inferior
- superior (outflow tract)
where is the ECG showin
- LV = RBBB
- RV or Septal LV = LBBB
- Lateral LV = I, aVL ,negative
- RV or septal LV = I, aVL, positive
- apex = V3-V5, negative
- base = V3-V5, positive
- inferior = II, III, aVF, negative (superior axis)
- superior (outflow tract) = II, III, aVF, positive (inferior axis)
what can pinpoint on an ECG if the patient has ventricular tachycardia
- Regular broad complex
Va dissociation
- fusion beats
- capture beats
- independent P wave activity
- ventricular concordance
- bizarre frontal axis
- very broad QRS
What do you do if the broad QRS complex is regular
It is VT until proven otherwise
- amiodarone 300mg IV over 20-60 minutes then 900mg over 24 hours
If known to be SVT with bundle branch block
- treat as for regular narrow-complex tachycardia
What do you do if the broad QRS complex is irregular
- AF with bundle branch block – treat as for narrow complex tachycardia
- Polymorphic VT e.g. Torsade de pointes – give IV magnesium
If the bradycardia has no adverse features how do you treat
calculate if there is a risk of asystole
- recent asystole
- Mobitz II AV block
- complete heart block with broad QRS complex
- ventricular pause greater than 3 seconds
if no
- continue to observe
if yes Consider interim measures - Atropine 500mcg IV repeat to maximum of 3mg then give - transcutaneous pacing then give - isoprenaline 5mcgmin-1 IV - adrenaline 2-10mcgmin-1 IV - alternative drugs
- Seek expert help - arrange transvenous pacing
What puts you at risk of asystole if you have bradycardia
- recent asystole
- Mobitz II AV block
- complete heart block with broad QRS complex
- ventricular pause greater than 3 seconds
Name the adverse features of bradycardia
- shock
- syncope
- myocardial ischaemia
- heart failure
What happens if you have adverse features of bradycardia
adverse features
- shock
- syncope
- myocardial ischaemia
- heart failure
Yes
- Atropine 500mcg IV repeat to maximum of 3mg
- Then if this does not work then do transcutaneous pacing
- if this does not work then isoprenaline/adrenaline infusion titrated to response
Yes
calculate if there is a risk of asystole
- recent asystole
- Mobitz II AV block
- complete heart block with broad QRS complex
- ventricular pause greater than 3 seconds
no
- continue observation
if no satisfactory response to atropine
Consider interim measures
- Atropine 500mcg IV repeat to maximum of 3mg
- Then if this does not work then do transcutaneous pacing
- if this does not work then isoprenaline/adrenaline infusion titrated to response
- Seek expert help - arrange transvenous pacing
what device treatment can you use for bradycardia
pacemaker - make sure that the heart rate never drops below a certain number
What device can you use for VT/VF
ICD
How does cardiac synchronisation devices work
- special pacemakers - implanted to pace the heart at all times in a specific manner to make sure that the RV/LV work in function
- BiV/CRT
How do arrhythmias often present
- Palpitations
- chest pain
- presyncope/syncope
- hypotension
- pulmonary oedema
What tests should be carried out for someone with arrhythmias
- FBC
- U and Es
- glucose
- calcium, magnesium
- TSH
- ECG - look for signs of IHD, AF, short PR intervals, long QT intervals (metabolic imbalance, drugs, congenital), U waves (hypokalaemia)
- can do a continuous ECG monitoring - Holter monitors or loop recorders
- ECHO - structural heart disease
- exercise ECG tests
Name examples of broad complex tachycardia
- Ventricular fibrillation
- asystole
- ventricular tachycardia
- torsade de pointes
What are the indications for permanent pacemaker
- Complete av block (Stokes–Adams attacks, asymptomatic, congenital).
- Mobitz type ii av block (p[link]).
- Persistent av block after anterior mi.
- Symptomatic bradycardias (eg sick sinus syndrome, p[link]).
- Heart failure (cardiac resynchronization therapy).
- Drug-resistant tachyarrhythmias.
Name the neurological causes of collapse
- hypoglycaemia
- seizure
- stroke
- vasovagal
Name the cardiovascular causes of collapse
- postural hypotension
- aortic stenosis
- arrhythmia
What is a vasovagal collapse occur in response to
- occurs in response to stimuli such as emotion, pain, fear, prolonged standing
- there is preceding nausea, pallor, sweat and closing visual fields
- the collapse for 2 minutes
- decrease in pulse and pupils are dilated
How would you test for vasovagal collapse
- Tilt-table test - if scope diagnosis is unclear
- consider investigations to exclude other causes
- ECG is normal
What is cardioversion
= treatment that aims to get the abnormal heart rhythm (arrhythmia) back to a normal pattern
- done by sending electric shocks to the heart through electrodes placed o the chest
Who is cardio version usually done to
- atrial fibrillation
- atrial flutter
What is ablation
- It either uses heat (radiofrequency ablation) or freezing (cryoablation) on the area of the heart that is causing the abnormal heart rhythm
what two scenarios is cardio version used in AF
- As emergency if the patient is haemodynamically unstable
- Electrical or pharmacological cardioversion as an elective procedure where a rhythm control strategy is preferred
describe how cardio version is used in AF before and after 48 hours
Onset <48 hours
- If AF is less than 48 onset patients should be heparinised
- Patients who have risk factors for ischaemic stroke should be pert on lifelong oral anticoagulation otherwise patients may be cardioverted using either DC cardioversion or amiodarone if strucual heart disease
- Following cardioversion if AF is confirmed as being less than 48 hours duration then further anticoagulation is unnecessary
Onset >48 hours
- If patient has been in AF for more than 48 hours then anticoagulation should be given at least 3 weeks prior to cardioversion
- If there is a high risk of cardioversion failure then it is recommended to have at least 4 weeks amiodarone or sotalol prior to cardioversion
- Following cardioversion patietns should be anticoagulated for at least 4 weeks
How is torsade de pointes treated
IV magnesium
What is torsade de pointes
type of ventricular tachycardia which is precipitated by prolongation of the QT interval
When do you use rhythm control in AF first instead of rate control
coexistent heart failure, first onset AF or an obvious reversible cause
What is normally first line treatment for AF rate or rhythm control
rate control unless
- coexist heart failure
- first onset AF
- Obvious reversible cause
