Cardiac Arrhythmias
What if the patient is haemodynamically unstable?
Increase vagal stimulation - valsalva manoeuvre / carotid sinus massage Adenosine - AV blocking drug - terminates the junctional tachcardia IV verapamil Beta blockers - metoprolol
Outline the causes of heart block
coronary artery disease fibrosis of conducting tissue cardiomyopathy in the elderly
What symptoms occur with third degree HB at the purkinje fibres?
dizziness blackouts (Stokes Adams attacks)
What is mobitz type II HB?
dropped QRS complex not preceded by progressive prolongation of PR interval
what does sick sinus syndrome predispose to?
ectopic pacemaker activity tachyarrhythmias (Tachy-Brady syndrome is seen)
What is 2:1 /3:1 HB?
every second or third P wave conducts to the ventricle (QRS complex seen after two or three P waves)
when is sinus tachycardia a physiological response?
exercise, excitement
What can aggravate the arrhythmias?
exertion alcohol coffee
What do patients with ventricular ectopic premature beats complain of?
extra beats missed beats heavy beats
How can bradycardias be categorised?
extrinsic intrinsic neurogenic
what is sick sinus syndrome?
failure of the SAN to depolarise (sinus arrest) failure of propagation to perinodal tissue (SAN block)
when else can sinus tachycardia occur?
fever anaemia heart failure thyrotoxicosis acute PE hypovolaemia drugs (catecholamines, atropine)
What happens in sinus arrhythmia?
fluctuations of autonomic tone; causes phasic changes in discharge rate
define tachycardia
heart rate greater than 100 beats per minute
define bradycardia
heart rate less than 60 beats per minute
What is the problem in survivors?
high risk of sudden death so treat with ICD
What if the patient is haemodynamically unstable?
immediate heparinisation cardioversion IV amiodarone - if fails reattempt; can given 2 doses
When does neurogenic bradycardia occur?
in carotid sinus syndrome vasovagal attacks
What are the causes of left bundle branch block?
ischaemic heart disease left ventricular hypertrophy aortic valve disease post cardiac surgery
If third degree HB occurs at the bundle of his what is shown on the ECG?
narrow QRS complex <0.12 secs slow heart rate 50-60 bpm
What happens in right bundle branch block?
no impulse propagated along the right bundle branch the two ventricles do not contract simultaneously spread from left ventricle to right ventricle secondary R wave (RSR) in V1 slurred S wave V5, V6
What is seen on the ECG?
no p waves fibrillation f waves
What does the ECG of ventricular ectopic show?
not conducted to ventricle through normal conducting tissue QRS complex is widened strange configuration
How are they treated?
oxygen IV access and fluid replacement
What are the symptoms of long QT syndrome?
palpitations syncope
How is the atrial ectopic treated?
palpitations are treated with beta blockers
What typically happens on inspiration?
parasympathetic tone decreases - increase in HR
what happens on expiration?
parasympathetic tone increases - decrease in HR
how is sick sinus syndrome treated?
permanent pacemaker temporary pacemaker (transcutaneous, transvenous) anti-arrhythmic drugs for the tachycardia - beta blocker anticoagulation for risk of thromboembolism ATROPINE for acute bradycardia
How is third degree HB with purkinje fibres treated?
permanent pacing
What does long QT syndrome increase the risk of?
polymorphic VT torsades de pointes rapid, regular sharp QRS complex switch between being upright and inverted
What happens in an atrial ectopic?
premature discharge of ectopic atrial focus
What is mobitz type I (wenckebach) HB?
progressive PR interval prolongation until P wave fails to conduct (no QRS complex after P wave) P wave then returns to normal, cycle repeats
What is seen on the ECG in first degree HB?
prolonged PR interval >0.22 seconds no change heart rate
How does the patient with VF present?
pulseless apnoeic unconcious
What is the long term management?
radiofrequency ablation of accessory pathway via cardiac catheter flecainide, verapamil, sotalol, amiodarone
How is atrial flutter treated?
radiofrequency ablation of re-entry circuit
What does sustained ventricular tachycardia show on an ECG?
rapid ventricular rhythm broad QRS complexes
What are the associated symptoms?
rapid, regular palpitations (abrupt onset, terminate suddenly) dizziness syncope dyspnoea chest pain
What is third degree HB at the BOH due to?
recent onset ischaemia
What is the acute management?
restore/maintain sinus rhythm
How is cardiac arrest treated?
resuscitation (stop when return of spontaneous circulation/pulse) post resus - maintain O2 saturations 94-98%, blood glucose <10mmol/L, therapeutic hypothermia
What is AVNRT?
ring of conducting tissue in the AV node limbs of the ring have differing conducting times and refractory periods re-entry circuit forms
What does the ECG show?
sawtooth appearance - flutter waves
what are the signs and symptoms of arrhythmias?
severe pulmonary oedema low cardiac output hypotension impaired conciousness cold, clammy extremities
What does the ECG show then?
shortened PR interval (early depolarisation) slurred start to the QRS complex (DELTA WAVE) narrow QRS complex
what does the ECG show in sick sinus syndrome?
sinus bradycardia with pauses in between p waves
What happens in second degree HB?
some of the atrial impulses fail to reach the ventricles
What are ventricular contractions in third degree HB due to?
spontaneous escape rhythm originating below the site of the block
what does AF increase the risk of?
stroke
What can arrhythmias cause?
sudden death, syncope, dizziness, palpitations
How can tachycardias be divided?
supraventricular tachycardias ventricular tachycardias
what are atrioventricular junctional tachycardias?
tachycardia due to re-entry circuits 2 pathways for conduction paraoxysmal SVTs - young patients
what is a supraventricular tachycardia?
tachycardia of the atria/ atrioventricular junction
What happens in AF?
the atrial activity is choatic and the atria becomes mechanically ineffective Av node conducts a proportion of atrial impulses, but this results in an irregular ventricular response
what is the rate of discharge under control of?
the autonomic nervous system (parasympathetic NS predominantly) this slows the spontaneous discharge rate
What happens in left bundle branch block?
the opposite to right bundle branch block secondary R wave (RSR) in lead I, AVL, V4-6 deep S wav in V1, V2
what is the normal cardiac pacemaker?
the sinoatrial node
What happens in first degree heart block?
there is prolonged conduction at the atrioventricular node
How is AF managed?
treat the precipitating factor; e.g. alcohol, toxicity, chest infection, hyperthyroidism
how is extrinsic bradycardia managed?
treat the underlying cause
What is the treatment for sinus tachycardia?
treat the underlying cause beta blockers can slow the sinus rate
How is it treated?
urgent DC cardioversion if haemodynamically compromised IV lidocaine/ amiodarone
What is ventricular fibrillation?
very rapid, irregular ventricular activation no mechanical effect so NO CARDIAC OUTPUT
When is sinus bradycardia normal?
when sleeping/ in athletes
What does a bundle branch block show on ECG?
wide QRS complex with abnormal pattern
How long does it take for irreversible brain damage to occur in cardiac arrest?
3 minutes
When does atrial fibrillation present?
5-10% >65 years are affected younger - paroxysmal
when does intrisic bradycardia occur?
1) acute ischaemia/ infarct of sinoatrial node (complication of myocardial infarction) 2) chronic degenerative conductions - fibrosis of the atria and sinoatrial node (sick sinus syndrome)
What if the patient is stable?
1) control heart rate - beta blockers - calcium antagonists - sedentary lifestyle give digoxin 2) control rhythm (young patients <65 yrs and symptomatic patients) cardioversion using beta blockers If HD present - amiodarone No HD - sotalol, flecainide, propafenone patients with infrequent symptomatic paraoxysmal AF, e.g. 1/ month - pill in pocket approach with oral flecainide/ propafenone 3) assess for anticoagulation as AF increase risk of thromboembolism warfarin; aim for INR around 2-3 young patients - aspirin
When does extrinsic bradycardia occur?
1) drugs - beta blockers, digoxin 2) hypothyroidism 3)hypothermia 4)cholestatic jaundice 5) raised intracranial pressure
What causes long QT syndrome?
1)congenital problems with sodium and calcium channel genes 2) electrolyte disturbances - hypokalaemia - hypocalcaemia - hypomagnesaemia 3) drugs - tricyclic antidepressants, phenothiazines, macrolide antibiotics
What does the ECG show in atrial ectopic?
ECG - early/abnormal P wave, normal QRS
What causes atrial tachyarrhythmias?
IHD rheumatic HD thyroitoxicosis cardiomyopathy lone AF WPW syndrome pneumonia atrial septal defect bronchial carcinoma pericarditis PE cardiac surgery acute on chronic alcohol use
How is VF treated?
IMMEDIATE DEFIBRILLATION
What does it respond to?
IV Atropine - no needed for pacing
How is long QT syndrome treated?
IV isoprenaline
When does WPW syndrome show on an ECG?
If the accessory path allows some atrial depolarisation to pass to the ventricle before entering the AV node
What are the three types of second degree heart block called?
Mobitz type I (wenckebach) Mobitz type II 2:1/3:1
Is treatment necessary in first degree HB?
No just monitoring
What does the ECG show in AVNRT?
P waves absent or P waves present immediately before the QRS complex QRS complex of normal shape (activated normally) occasionally wide QRS complex
What happens in cardiac arrest?
There is no effective cardiac output patient is unconcious, apnoeic, absent arterial pulses (carotid arteries)
What is non-sustained ventricular tachycardia?
VT >5 consecutive beats lasts less than 30 seconds occurs in patient with heart disease
What is third degree HB?
When atrial activity fails to conduct to the ventricles NO ASSOCIATION BETWEEN P WAVES AND QRS COMPLEXES
What is long QT syndrome?
When ventricular repolarisation is prolonged prolonged QT interval
What syndrome is defined by AVRT?
Wolf Parkinson's White syndrome
What is an arrhythmia?
abnormality of cardiac rhythm
What is an AVRT?
accessory pathway - connects atria and ventricles can be retrograde or anterograde conduction
What does this irregular ventricular response cause?
an irregularly irregular pulse
What is atrial flutter?
associated with AF atrial rate 300bpm AV node conducts every second flutter beat ventricular rate 150bpm
what does the term atrial tachyarrhythmia encompass?
atrial fibrillation, atrial flutter
If a conduction block occurs at the AV node or the bundle of his what is it called?
atrioventricular block
What does AVNRT stand for?
atrioventricular nodal re-entry tachycardia
What is AVRT?
atrioventricular reciprocating tachycardia
How are ventricular ectopics treated?
beta blockers
How is it treated?
beta blockers ICD
How is recurrence prevented?
beta blockers implantable cardioverter-defibrillator
If third degree HB occurs at the purkinje fibres what is shown on the ECG?
broad QRS complex >0.12 secs slow heart rate 40bpm
if a conduction block occurs at the bundle branch what is it called?
bundle branch block
What are the causes of right bundle branch block?
can occur in normal individuals pulmonary embolus right ventricular hypertrophy ischaemic heart disease congenital heart disease (atrial septal defect) Fallots teratology
