BOF: 2.17
A 56-year-old male lawyer has persistent atrial
fibrillation. He has had direct current cardioversion twice and has been on
amiodarone and warfarin but has gone into atrial fibrillation again.
A decision has been made to refer him for radiofrequency
ablation treatment. This treatment involves radiofrequency ablation of the
ostium of the:
a)
Superior vena cava
b)
Inferior vena cava
c)
Coronary sinus
d)
Pulmonary veins
e)
Coronary arteries
Answer:
d)
Atrial fibrillation is one of the most common arrhythmias
and is the strongest independent risk factor for embolic stroke.
Classification of atrial fibrillation
Atrial fibrillation may be:
Paroxysmal (where the episode
terminates spontaneously)
Persistent (where electrical or
chemical cardioversion is required to terminate it)
Chronic (where cardioversion is
unsuccessful or not indicated)
Aims of treatment
The aims of treatment are:
Rhythm control
Rate control
Reduction in thromboembolic risk
In older patients no mortality or morbidity benefits have
been shown in rhythm control over rate control.
Anti-coagulation
Warfarin
Should be started at least 3 weeks before
attempted cardioversion and continued for at least 4 weeks after successful
cardioversion. It may be necessary to continue anticoagulation for longer
periods if there is an increased risk of reverting to atrial fibrillation or
if there are ongoing paroxysms of atrial fibrillation.
Continuous anticoagulation is required if the
patient is being managed by controlling rate
Ximelagtran
This is a new drug, which acts as a direct
thrombin inhibitor. It does not need monitoring. It is not in routine use yet.
Rhythm control
Direct current cardioversion
External
Using monophasic or more
recently biphasic defibrillators
Internal
Using transvenous atrial
defibrillation
Pharmacological cardioversion
The established agents are:
Sotalol, flecainide,
amiodarone, propafenone
Other drugs:
Dofetilide (available in the US)
Azimilide (undergoing
evaluation)
Pacing
Dual chamber pacing with
anti-atrial fibrillation algorithms may be used for those who have an
additional indication for pacing
Radiofrequency ablation of the AV node
Interrupt conduction of the AV
node followed by pacemaker implantation
Maze procedure
Intra-atrial incisions to form
anatomical barriers and reduce the number of circulating wavelets that cause
atrial fibrillation.
This may be used if the patient
has another indication for cardiac surgery
Radiofrequency ablation of the ostium of the pulmonary
veins
This isolates the pulmonary
veins by ablating the electrical connections at the ostia and has shown high
success rates.
Rate control
The drugs commonly used are digoxin, beta-blockers and
calcium antagonists together with anticoagulation.
