REVIEW
SA JOURNAL OF DIABETES & VASCULAR DISEASE
62
VOLUME 7 NUMBER 2 • JUNE 2010
strategy), it has a role for managing infrequent symptomatic
episodes of persistent AF where a pill-in-the-pocket strategy is
ineffective, particularly if there has been a recognised infrequent
trigger such as respiratory tract infection or a surgical procedure.
Also, if a first cardioversion was unsuccessful (either complete
failure, or early recurrence of AF), a second attempt can be made
on adjuvant anti-arrhythmic therapy, and/or via a specialist centre
with high-energy external defibrillators or facilities for internal
cardioversion. Beyond this, recurrence of AF should either prompt
alteration to a rate-control strategy, or referral for consideration of
catheter ablation.
Rate versus rhythm control
The AFFIRM
39
and RACE
59
trials prospectively compared rate with
rhythm control (RACE: cardioversion
+
/
-
drugs. AFFIRM: drugs
+
/
-
cardioversion) in relatively elderly, high-risk AF populations. In
AFFIRM, rate control appeared non-inferior to rhythm control, and
was associated with fewer hospitalisations, strokes, and episodes of
torsade de pointes. However, a much greater proportion of patients
had anticoagulation withdrawn in the rhythm-control arm once
rhythm control was achieved, whichmay partly explain the increased
risk of stroke. This is an important lesson learnt from AFFIRM – the
decision to anticoagulate should, to a large extent, be based not
on whether sinus rhythm has been restored with cardioversion or
drugs, but on the pre-existing risk score (CHADS2).
The AF-CHF trial has further examined the relative roles of rate
and rhythm control in patients with heart failure.
60
Rate control
was non-inferior to (drug/cardioversion-based) rhythm control
for cardiovascular and all-cause mortality, and stroke in a large
proportion of patients.
It remains possible that better rhythm-control treatments will
shift the balance in favour of this strategy. AFFIRM and similar
data, which suggested that drug-based rate and rhythm control
strategies were equivalent, were also from an era when it was
common practice to stop anticoagulation when rhythm control was
achieved (regardless of risk of stroke). It is not known whether more
modern comparisons of the latest generations of anti-arrhythmic
drugs such as
dronedarone
which appears to reduce cardiovascular
morbidity and mortality,
56
in an era during which anticoagulation
is based more on thromboembolic risk than rhythm, would
produce similar results. Moreover, results of direct comparisons
of drug-based rate control vs ablation-based rhythm control are
not going to be available for a number of years, although there
are some indications that that ablation
may
reduce cardiovascular
morbidity
61,62
and mortality.
61
The consensus is that when AF is well tolerated in the over-
65s, it can reasonably be treated with a rate-control strategy. If,
however, a patient remains symptomatic despite optimal rate
control, the rhythm-control strategy is recommended. Appropriate
thromboprophylaxis should be given regardless of the strategy.
Who should be referred to a tertiary care heart
rhythm specialist (cardiac electrophysiologist)?
NICE guidelines suggest the following patients should be referred:
those who have failed pharmacological therapy
•
those with lone AF
•
those with ECG evidence of an underlying electrophysiological
•
disorder.
Most younger patients, particularly those under the age of 60,
should be assessed by an electrophysiologist. In particularly young
patients (
<
40 years) another arrhythmia capable of precipitating
AF, such as WPW syndrome or supraventricular tachycardia, and
that can be easily cured by catheter ablation can sometimes be
identified. However, there also appears to be a distinct group of
young (30–50 years) patients (men more frequently than women)
with no obvious associated arrhythmias or structural abnormalities
(lone AF) who are often quite symptomatic and who tend to require
specialist advice/treatment.
Many regions now have dedicated arrhythmia clinics, often with
a nurse specialist in a central role working in collaboration with a
cardiologist specialising in heart rhythm disorders. There are also
an increasing number of physicians – within both primary and
secondary care – with specialist expertise in medical management
of AF. For most patients the diagnosis and initial management of
AF can take place in primary care, but referral to an AF specialist
physician or clinic can be useful when the appropriate management
strategy is not clear or when initial therapies fail.
What are the specialist options?
A cardiologist with a specialist interest in heart rhythm (cardiac
electrophysiologist) can, amongst other things, offer the following
therapeutic options:
further optimised anti-arrhythmic therapy and/or rate control
•
pacemaker insertion, eliminating bradycardias and allowing
•
escalation in pharmacological therapy
catheter ablation of the AV node with pacemaker insertion
•
radiofrequency catheter ablation of atrial fibrillation.
•
This last procedure has become established over the last 10 years,
and is now an invaluable non-pharmacological rhythm-control
option for symptomatic patients unresponsive to, or intolerant of,
anti-arrhythmic drugs.
The discovery in the late 1990s that AF could have a focal origin,
often in the pulmonary veins, led to the use of minimally invasive
radiofrequency catheter ablation techniques to destroy these areas,
63
and later techniques to electrically disconnect the pulmonary veins
from the atria – so-called ‘pulmonary vein isolation’. Subsequent
advances in both understanding of AF pathophysiology, and
available technology, including the 3-D reconstruction of the
patient’s atria and pulmonary veins, have enabled creation of
complete encircling and linear atrial lesions (Fig. 2), in addition to
targeting other areas of pro-fibrillatory activity that contribute to
the maintenance of AF.
The procedures require significant expertise, although
technologies for 3-D catheter localisation and reconstruction of
the shape of the left atrium and pulmonary veins, as well as the
recently introduced remote catheter navigation technologies are
proving helpful. A typical procedure lasts 2–4 hours (less for some
paroxysmal, more for some long-standing persistent/permanent AF),
and is usually performed under sedation or general anaesthesia.
Long-term freedom from AF can be expected in 70–90% of
patients, depending on the duration and complexity of AF, with
repeat procedures being necessary to achieve these results in a
significant minority of patients. Important complications of the
procedure include transient ischaemic attack or stroke (0.5–1.5%,
largely dependent on age), tamponade needing drainage (1–3%),
symptomatic pulmonary vein stenosis requiring stenting (< 0.5%),
and right phrenic nerve palsy (0.3%, usually transient). These risks
