Cardiovascular Journal of Africa: Vol 25 No 6 (November/December 2014)

35 / 66

CARDIOVASCULAR JOURNAL OF AFRICA • Volume 25, No 6, November/December 2014 AFRICA 285
of spontaneous resolution within six weeks, irrespective of
treatment modality used. Up to 80% of patients convert to
sinus rhythm within 24 hours, even without treatment.7 Less
than 10% of patients discharged in sinus rhythm develop
AF recurrence within six weeks of discharge.20 This supports
the merit of a more conservative approach locally, especially
with haemodynamic stability and low ventricular response.
Simple treatment measures such as inotrope reduction, fluid
balance management and electrolyte correction (potassium and
magnesium) must not be underrated. Anaemia, hypoxia, pain
and patient arousal must be addressed as well.
For patients who are haemodynamically unstable, have rapid
ventricular responses or features of myocardial ischaemia, initial
electrical cardioversion followed by intravenous amiodarone
has proved to be a useful strategy locally. We have adopted a
rhythm-control strategy as per international trends. A study by
Lee et al. showed a decreased time to cardioversion, prolonged
maintenance of sinus rhythm and decreased overall hospital stay
when a rhythm-control strategy was adopted.21
In our study, electrical cardioversion was successful only
as an isolated modality in nine patients and this is perhaps
partially explained by the exclusive use of antero-lateral pad
placement.2 Direct-current cardioversion is recommended as
first-line therapy if AF causes haemodynamic instability or
ischaemia. The initial shock energy should start with 300–360
J of monophasic waveform or 200 J of biphasic waveform and
results in more than 95% success rate in converting to sinus
rhythm.22
Amiodarone is the preferred anti-arrythmic agent in our
setting as it is readily available, has anti-arrythmic efficiency
similar to class I agents, can be used in patients with low ejection
fractions, has no pro-arrhythmic tendency and is easily converted
to oral medication. Intravenous amiodarone leads to sinus
conversion in up to 90% of patients within the first 24 hours.7
In our study, amiodarone was administered as an intravenous
loading dose (300 mg in 200 ml of 5% dextrose water over 45
minutes, followed by 900 mg in one litre of 5% dextrose water
over 24 hours) during the first 24 hours of AF onset after failed
electrical cardioversion. This was converted to oral agents (300
mg tds) on post-operative day two (or soonest possible) and
weaned off gradually in the subsequent weeks. Rho suggests the
continuation of amiodarone for a minimum of one week post
surgery since the occurrence of AF beyond day seven is rare.4
Amiodarone has proved to be effective in controlling heart rate
in the post-operative period and the intravenous preparation is
associated with improved haemodynamic status.23
Prophylactic amiodarone has inconsistently proved to effect
a reduction in post-operative AF. Several trials evaluating
the benefit of prophylactic amiodarone included patients
concomitantly treated with β-blockers. Mahoney et al. showed
that intravenous amiodarone is not cost effective for AF
prevention if administered to all patients.15Anti-arrhythmic
agents other than amiodarone used for the treatment of AF in
the study included atenolol, digoxin and diltiazem. These agents
are used for rate control in haemodynamically stable patients.
The effect of these agents on AF is undoubtedly commensurate
with the care with which they are used.
Short-acting β-blockers are the therapy of choice for rate
control, especially in ischaemic heart disease, but may be
poorly tolerated in asthmatics and patients in cardiac failure.3 A
meta-analysis of 24 randomised, controlled trials by Andrews
et al. demonstrated a 77% reduction in AF post CABG. 9 The
protective effect of pre-operative β -blocker therapy is related
to the blunting of the high sympathetic tone occurring after
cardiac surgery.16 Findings of the AFIST II trial suggested that
the concomitant use of β-blockers and amiodarone is especially
rewarding.24 Dunning et al. recommended β-blockers for the
prevention of AF in all patients undergoing cardiac surgery.2
Pre-operative β-blocker withdrawal is a significant risk factor for
AF and must be avoided.5
Digoxin is grossly inefficient when adrenergic tone is high and
is selectively used in patients with reduced ejection fractions. 3 AV
nodal blocking agents such as the non-dihydropyridine calcium
channel blockers can be alternatively used for rate control
but may cause low cardiac output. These agents must be used
cautiously until additional data on their safety profile becomes
available.3
Historically, several modalities for AF prevention have been
used with varying results. These include β -blockers, amiodarone,
digoxin, bi-atrial pacing, calcium channel blockers, magnesium,
statins, N-3 polyunsaturated fatty acids (PUFAs) and anti-
inflammatory agents.3
We do not use any AF prophylaxis strategy in our unit. There
are no robust risk models or evidence available to govern such
a strategy. Moreover, prophylaxis has not been clearly shown
to positively impact on morbidity or mortality arising from
AF, and we are unaware of any feasibility studies supporting
a prophylaxis strategy in resource-constrained environments.3
The optimal anti-arrhythmic agent, dose, timing of initiation,
and route and duration of drug administration for prophylaxis
remain elusive.
β-blockers are used liberally for our cardiac surgical patients,
mainly for coronary artery disease, as evidenced in this cohort,
barring contra-indications. We are currently content to continue
β-blocker use in the peri-operative period and enjoy whatever
consequential AF reduction it may confer.
For the treating surgeon in the developing world, AF is a
harbinger of increased LOS and resultant cost burdens.4,11,14 The
patients in our cohort took 4.6 days more than the institutional
norm to return to the general ward. The cost implication is likely
to be significant in light of the strain imposed on intensive-care
and high-care wards.
In a study in the United States of America conducted by
Aranki et al., LOS was increased by 4.9 days, with additional
hospital costs amounting $10 000–11 500.11 AF results in longer
ICU and overall hospital stays, even after adjusting for severity
of illness.7 Tamis et al. showed an increase in LOS of 3.2 days
independent of variables.25 It is, however, possible that the RGW
status in our cohort was affected by other disease processes
unrelated to AF.
Statins have been observed to attenuate inflammation and
reduce AF post coronary surgery.26 The ARMYDA-3 trial was
a prospective, randomised study that showed atorvastatin 40
mg daily, commenced seven days prior to elective surgery on
cardiopulmonary bypass and continued in the post-operative
period, reduced the incidence of AF by 61%.27
An exciting aspect of de novo AF post cardiac surgery not
addressed by this study requires discussion; the role of cardiac
biomarkers and risk-prediction models in the prediction of
post-operative AF. Studies by Gasparovic et al. and Pilatis et al.