page112
should be treated with 500 micrograms of atropine sul-
phate given intravenously;
the dose may be repeated
every 3–5 minutes if necessary up to a maximum total
dose of 3 mg. If there is a risk of asystole, or if the patient
is unstable and has failed to respond to atropine,
adr-
enaline should be given by intravenous infusion in a
dose of 2–10 micrograms/minute, adjusted according to
response.
For further advice,
refer to the most recent recommen-
dations of
the Resuscitation Council
(UK)
available at
www.resus.org.uk.
Ventricular tachycardia
Pulseless ventricular tachy-
cardia or ventricular fibrillation should be treated with
immediate defibrillation (see Cardiopulmonary Resusci-
tation,
section 2.7.3).
Patients with unstable sustained ventricular tachycardia,
who continue to deteriorate with signs of
hypotension
or reduced cardiac output, should receive direct current
cardioversion to restore sinus rhythm. If this fails, intra-
venous amiodarone (section 2.3.2) should be adminis-
tered and direct current cardioversion repeated.
Patients with sustained ventricular tachycardia who are
haemodynamically stable can be treated with intra-
venous anti-arrhythmic drugs.
Amiodarone is the pre-
ferred drug.
Flecainide,
propafenone (section 2.3.2),
and,
although less effective,
lidocaine (section 2.3.2)
have all been used. If sinus rhythm is not restored, direct
current cardioversion or pacing should be considered.
Catheter ablation is an alternative if
cessation of
the
arrhythmia is
not
urgent.
Non-sustained ventricular
tachycardia can be treated with a beta-blocker (section
2.4).
All
patients
presenting with ventricular
tachycardia
should be referred to a specialist. Following restoration
of
sinus rhythm,
patients who remain at
high risk of
cardiac arrest
will
require maintenance therapy.
Most
patients will be treated with an implantable cardioverter
defibrillator.
Beta-blockers
or
sotalol
(in place of
a
standard beta-blocker),
or amiodarone (in combination
with a standard beta-blocker), can be used in addition to
the device in some patients;
alternatively,
they can be
used alone when use of
an implantable cardioverter
defibrillator is not appropriate.
Torsade de pointes
is a form of ventricular tachycardia
associated with a long QT syndrome (usually drug-
induced,
but
other
factors
including
hypokalaemia,
severe
bradycardia,
and
genetic
predisposition
are
also implicated).
Episodes are usually self-limiting,
but
are frequently recurrent and can cause impairment or
loss of consciousness.
If not controlled,
the arrhythmia
can progress to ventricular fibrillation and sometimes
death.
Intravenous
infusion of
magnesium sulphate
(section 9.5.1.3)
is
usually effective.
A beta-blocker
(but not
sotalol)
and atrial
(or ventricular)
pacing can
be considered. Anti-arrhythmics can further prolong the
QT interval, thus worsening the condition.
2.3.2
Drugs for arrhythmias
Anti-arrhythmic drugs can be classified clinically into
those that
act
on supraventricular
arrhythmias
(e.g.
verapamil),
those that
act
on both supraventricular
and ventricular
arrhythmias
(e.g.
amiodarone),
and
those that act on ventricular arrhythmias (e.g. lidocaine).
Anti-arrhythmic drugs can also be classified according
to their effects on the electrical behaviour of myocardial
cells during activity (the Vaughan Williams classifica-
tion)
although this classification is of
less clinical
sig-
nificance:
Class I:
membrane stabilising drugs (e.g.
lidocaine,
flecainide)
Class II:
beta-blockers
Class III:
amiodarone;
sotalol (also Class II)
Class IV: calcium-channel blockers (includes verap-
amil but not dihydropyridines)
Cautions
The negative inotropic effects of anti-arrhy-
thmic drugs tend to be additive.
Therefore special care
should be taken if
two or more are used,
especially if
myocardial
function is impaired.
Most
drugs that
are
effective in countering arrhythmias can also provoke
them in some circumstances;
moreover,
hypokalaemia
enhances the arrhythmogenic (pro-arrhythmic) effect of
many drugs.
Supraventricular arrhythmias
Adenosine is usually the treatment of choice for termi-
nating paroxysmal
supraventricular
tachycardia.
As it
has a very short duration of action (half-life only about 8
to 10 seconds,
but
prolonged in those taking dipyrid-
amole),
most side-effects are short lived.
Unlike verap-
amil, adenosine can be used after a beta-blocker. Verap-
amil may be preferable to adenosine in asthma.
Dronedarone is a multi-channel blocking anti-arrhyth-
mic drug;
it
is
licensed for
use in clinically stable
patients with previous or current non-permanent atrial
fibrillation, to prevent recurrence or to lower the ventri-
cular rate.
The
Scottish Medicines Consortium
(p.
4) has advised
(August 2010) that dronedarone (
Multaq
c
) is accepted
for restricted use within NHS Scotland for the preven-
tion of
recurrence of
atrial
fibrillation in patients in
whom conventional
first-line anti-arrhythmic drugs are
ineffective, contra-indicated, or not tolerated; treatment
should be initiated on specialist advice only.
NICE guidance
Dronedarone for the treatment of non-
permanent atrial fibrillation (August 2010)
Dronedarone is an option for the treatment of non-
permanent atrial fibrillation only in patients who:
.
are not controlled on first-line therapy (usually
including beta-blockers),
and
.
do not have unstable New York Heart Associa-
tion class III or IV heart failure,
and
.
have at least one cardiovascular risk factor from
the following:
.
hypertension managed by at least two dif-
ferent drug classes
.
diabetes mellitus
.
previous transient ischaemic attack,
stroke,
or systemic embolism
.
left atrial diameter 50 mm
.
left ventricular ejection fraction <40%
.
age 70 years
92
2.3.2 Drugs for arrhythmias
BNF 61
2
Cardiovascular system