Arrhythmia
Arrhythmia – Irregularity of heart beats
Causes
Cardiac: MI, coronary artery disease,
Non-cardiac: Caffeine, smoking, alcohol, pneumonia, drugs (beta2-agonists, digoxin, L-dopa, tricyclics, adriamycin, doxorubicin), metabolic imbalance (K, Ca, Mg, hypoxia, hypercapnia. metabolic acidosis, thyroid disease, phaeochromocytoma).
Presentation
Palpitation, chest pain, presyncope/syncope, hypotension, or pulmonary oedema
Some arrhythrnias may be asymptomatic and incidental
eg AF.
Tests
FBC, U&E, glucose, Ca, Mg, TSH
ECG: Look for signs of IHD, AF, short PR interval (WPW syndrome), long QT interval (metabolic imbalance, drugs, congenital), U waves (hypokalaemia). 24h ECG monitoring;
Echo: To look for structural heart disease, eg mitral steriosis
Provocation tests: Exercise ECG, cardiac catheterization, and electrophysiological studies
Treatment
Bradycardia
Treat the cause
HR <40bpm style="font-family: Wingdings;">à give IV atropine 0.6—1.2mg (up to maximum of 3mg).
If no response à temporary pacing wire
If necessary àisoprenaline infusion or use external cardiac pacing.
Sick sinus syndrome
Pace if symptomatic.
Narrow Complex tachycardia (>100bpm + QRS <120ms)
Sinus tachycardia: normal P wave followed by normal QRS.
SVT: p wave absent or inverted after QRS.
AF: absent P wave, irregular QRS complexes.
Atrial flutter: atrial rate usually 300bpm giving flutter waves or ‘sawtooth’ baseline, ventricular rate often l50bpm (2:1 block).
Atrial tachycardia: abnormally shaped P waves may outnumber QRS.
Multifocal atrial tachycardia: 3 or more p wave morphologies, irregular QRS complexes.
junctional tachycardia: rate 150-250bpm, P wave either buried in QRS complex or occurring after QRS complex.
Sinus tachycardia
Treat the cause
SVT
Adenosine
If fails à use verapamil 5-10mg iv over 2min, or over 3mm if elderly. If fails à give further dose of 5mg IV after 5-10min. Alternatives: atenolol 2.5mg iv at 1 mg/min repeated at 5mm intervals to a maximum of 10mg or sotalol 20—60mg iv.
If fails à DC cardioversion.
AF/flutter
Common causes:
Heart failure; hypertension; cardiac ischaemia; MI (seen in
22%); mitral valve disease; pneumonia: hyperthyroidism: alcohol
Rare causes:
Cardiomyopathy, constrictive pericarditis, sick sinus syndrome, bronchial carcinoma, atrial myxoma, endocarditis, haemochromatosis, sarcoidosis
ECG in AF/flutter
Atrial flutter
P wave rate 300/min
Sawtoothed pattern
2:1, 3:1 or 4:1 block
Block increased by carotid sinus pressure
Atrial fibrillation
QRS complex characteristically over 160/min without treatment, but can be slower
No P waves identifiable, but there is a varying, completely irregular baseline
Treatment of AF
Acute AF (eg <72h)
Treat any associated acute illness (eg MI, pneumonia)
To control ventricular rate à digoxin
If ventricular rate still too fast and
If AF does not resolve à drug or electrical cardioversion.
Drug cardioversion: amiodarone IVI (5mg/kg over 1h then ~900mg over 24h via a central line max 1.2g in 24h) or PO (200mg/8h for lwk, 200mg/12h for lwk, 100—200mg/24h maintenance). Alternative: flecainide 2mg/kg iv over >25mm (max 150mg) with ECG monitoring. 300mg stat PC may also work.
DC cardioversion is indicated: (1) electively, following a first attack of AF with an identifiable cause; (2) as an emergency, if the patient is compromised.
If AF is of recent onset with a structurally normal heart on echo, anticoagulation is not required but aspirin may be given. Otherwise, anticoagulate with warfarin for 3wks before and 4wks after DC cardioversion.
Chronic AF
Control rate with digoxin
If rate still too fast, check compliance and serum level (take blood >6h after last dose), cautiously increase dose or consider low-dose beta-blocker (eg metoprolol), Alternative: amiodarone
If >65yr à warfarin Aim for an INR of 2.5—3.5.
IF <65yr style="font-size: 10pt;">(eg hypertension, diabetes,
Paroxysmal AF
Sotalol 80mg/24h
Alternative: amiodarone
Treatment summary for AF
Treat any reversible cause.
Control ventricular rate.
Consider cardioversion to sinus rhythm, if onset within last 12 months (do echo first is heart structurally normal?).
Prevent emboli: warfarin (or aspirin)
Treatment of Atrial flutter
Consider cavotricuspid isthmus ablation
Atrial tachycardia
If digoxin toxicity à stop digoxin; digoxinspecific antibody fragments. Maintain K at 4-5mmol/L
Mulifocal atrial tachycardia
Most commonly occurs in COPD.
Correct hypoxia and hypercapnia.
Consider verapamil if rate remains >110bpm.
Junctional tachycardia
There are 3 types of junctional tachycardia:
AV nodal re-entry tachycardia (AVNRT)
AV re-entry tachycardia (AVRT)
His bundle tachycardia
Treatment
vagal manoeuvres
Adenosine
If it recurs, treat with a beta-blocker or amiodarone.
Radiofrequency ablation
Broad complex tachycardia (>100bpm + QRS >120ms)
Differential Dx:
VT; include Torsade de pointes
SVT with aberrant conduction, eg AF, atrial flutter
ECG findings in favour of VT:
Positive QRS concordance in chest leads
Marked LAD
AV dissociation (occurs in 25%) or 2: 1 or 3: 1 AV block
Fusion beats or capture beats
RSR complex in V1 (with positive QRS in V1)
QS complex in V6 (with negative QRS in V1).
Management
Connect to a cardiac monitor; have a defibrillator to hand.
Give high-flow oxygen by face mask
Obtain IV access and take blood for U&E, cardiac enzymes, Ca, Mg.
Obtain 12-lead ECG
ABG (if evidence of pulmonary oedema, reduced conscious level, sepsis).
VT: Haemodynamicaliy stable
Correct hypokalaemia and hypomagnaesemia
Amiodarone 150mg IV over 10min, then 300mg over 1hr or lignocaine 50mg over 2mm repeated every 5min to 200mg max
If this fails, or cardiac arrest occurs, use DC shock
After correction of VT, establish the cause from history/investigations.
Maintenance antiarrhythmic therapy may be required. If VT occurs <24h>24h after MI, give IV lidocaine infusion and start oral antiarrhythmic: eg amiodarone.
Prevention of recurrent VT: Surgical isolation of the arrhythmogenic area or implantation of tiny automatic defibrillators may help.
VF
Use asynchronized DC shock
Ventricular extrasystoles (ectopics)
In post MI, there is a risk of VF if 'R on T' pattern is seen.
If frequent (>10/min), treat with lignocamne 100mg IV
Torsade de pointes
Mg sulfate, 8mmol over 15mm (≈4mL of 50% solution) ± overdrive pacing.
Indications for temporary cardiac pacing
Symptomatic bradycardia, unresponsive to atropine.
Acute conduction disturbances following MI:
After acute anterior MI, prophylactic pacing is required in:
Complete AV block
Mobitz type I AV block (Wenckebach)
Mobitz type II AV block
Non-adjacent bifascicular or trifascicular block
After inferior MI
Suppression of drug-resistant tachyarrhythmias, eg
Special situations: During general anaesthesia; during cardiac surgery; during electrophysiological studies; drug overdose (eg digoxin, 3-blockers, vera- pamil).
Indications for a permanent pacemaker
Complete AV block (Stokes –
Mobitz type II AV block
Persistent AV block after anterior MI
Symptornatic bradycardias (eg sick sinus syndrome)
Drug-resistant tachyarrhythmias.
Antiarrhythmic Drugs
Quinidine sulfate
Quinidine gluconate
Procainamide
Disopyramide
Group lB
Lidocaine
Mexiletine
Group IC
Flecainide
Propafenone
Group II
Metroprolol
Group III
Amiodarone
Ibutilide
Dofetilide
Bretylium
Sotalol
Group IV
Verapamil
Diltiazem
Other
Digoxin
Adenosine
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