Cardiovascular Journal of Africa: Vol 21 No 3 (May/June 2010) - page 18

CARDIOVASCULAR JOURNAL OF AFRICA • Vol 21, No 3, May/June 2010 140 AFRICA
and persistent AF who underwent isolated mitral valve inter-
vention during the cardiac operation, their AF did not resolve.9
Surgical treatments for AF, including the Cox-Maze III proce-
dure, a relatively complicated procedure based on a ‘cut and
sew’ principle, and radiofrequency ablation, a relatively simple
procedure, have resulted in 70 to 99% success rates.
In the series of Cox et al.,10 the Cox-Maze III procedure was
performed in 346 patients, with an operative mortality of 2%.
This was the largest sample using the Cox procedure and AF
could be treated in 99% of patients, with only 2% requiring long-
term postoperative anti-arrhythmia medication. Thirty-eight per
cent of their cases had transient postoperative AF, which was
attributed to the peri-operative short atrial refractory period, and
did not affect long-term results.11 Fifteen per cent of patients
required permanent pacemakers after the operation. Based on
these results, the Cox-Maze III procedure has been accepted as
the gold standard for the treatment of AF.
The success rates of Cox-Maze III procedures reported by
other centres have been lower than those reported by Cox et al. In
most series, mitral valve surgery combined with the Cox-Maze
III procedure resulted in 75 to 82% success rates for the treat-
ment of AF, and pacemaker implantation was reported in 2 to
24% of cases.12-15 These investigators attributed their relatively
low success rates to the profile of their patients, which included
those resistant to medical treatment and having additional
cardiac pathologies requiring open-heart surgery. On the other
hand, in a study, Cox et al. compared patients with and without
concomitant valvular surgery and did not find any difference in
terms of incidence of peri-operative atrial arrhythmia.16
In order to decrease peri-operative bleeding and shorten cross
clamping and cardiopulmonary bypass durations, the original
incisions of the Cox-Maze III procedure have been replaced
by lesions created by energy sources. Rates of 70 to 90% for
absence of atrial AF have been reported with radiofrequency
ablation. 17 In the present study, sinus rhythm was resumed in 75,
78 and 79% of cases at the third, sixth and 12th months post-
operatively, respectively. Although these rates were lower than
those reported by Cox et al ., they were similar to other results
for Cox-Maze III and radiofrequency ablation procedures. None
of our patients required a permanent pacemaker. The ease of the
procedure, less time needed and rare requirement of permanent
pacemaker are the advantages of radiofrequency ablation over
Cox-Maze III, whereas cost is its disadvantage.
Various types of lesions have been defined for radiofrequency
ablation.12,18,19 All these lesions involve the complete or almost
complete isolation of the pulmonary veins, and excision and
exclusion of the left atrial appendage. In addition, they include
the prevention of transmission by creating lesions between the
left pulmonary veins and the left atrial appendage, and also
between the left pulmonary veins and the mitral valve annulus.
In addition to these lesions, we also created a bipolar lesion on
the left atrial isthmus (between the LAA and mitral annulus).
Despite the diversity of these lesion types, similar AF treatment
rates were found. Success rates were almost as high as those of
the Cox-Maze III procedure.
Inclusion of only the left atrium during the ablation procedure
is still a debated issue. As atrial fibrillation originates from the
left side and atrial flutter from the right side, most authors advo-
cating the Cox-Maze III procedure suggest that an only left-sided
procedure would increase the incidence of atrial flutter and prob-
ably also the atrial fibrillation rate.18 Nakagawa et al. particu-
larly emphasised the importance of the isthmus line between the
coronary sinus and tricuspid valve, as it is responsible for most
atrial flutters.20 On the other hand, several theories indicate that
an isolated left atrial procedure may be effective. For example,
the origin of focally induced atrial fibrillation is frequently at
the right atrium, particularly on the pulmonary veins. Therefore
electrical isolation of the pulmonary veins has been suggested to
prevent the initiation of atrial fibrillation.21
Willams et al. compared the results of left-sided and bilateral
unipolar radiofrequency ablation but did not find a significant
difference (79 and 87%, respectively).18 Other investigators have
reported successful results with isolated left atrial ablation.22,23
We performed isolated left atrial ablation in all our patients and
TABLE 3. EFFECTS OF PRE-OPERATIVE CARDIAC
PARAMETERS ON ECG RHYTHMAT 6 MONTHS
Holter-ECG at 6 months
Test statistics
AF (n = 17)
(mean ± SD)
NSR (n = 59)
(mean ± SD)
LA 5.11 ± 0.74 4.98 ± 0.63 z: –0.422; p: 0.673
LVEDD 4.75 ± 1.30 5.06 ± 0.70 t: –1,192; p : 0.238
LVESD 3.38 ± 0.78 3.25 ± 0.81 t : 0.534; p : 0.596
EF 55.12 ± 9.79 55.07 ± 9.46 t : 0.017; p : 0.987
PAP 50.56 ± 14.16 46.70 ± 12.22 t : 1.036; p : 0.304
LVEDP 9.00 ± 5.24 10.77 ± 11.77 t: –0.557; p : 0.580
MAXG* 18.75 ± 2.81 17.43 ± 5.59 t : 0.633; p : 0.532
MVA* 1.55 ± 0.92 1.20 ± 0.81 z: –0.773; p: 0.440
AF: atrial fibrillation; NSR: normal sinus rhythm; t: Student’s t-test; z :
Mann-Whitney U-test; LA: left atrial diameter; LVEDD: left ventricu-
lar end-diastolic diameter; LVESD: left ventricular end-systolic diam-
eter; EF: ejection fraction; PAP: pulmonary artery pressure; LVEDP:
left ventricular end-diastolic pressure; MAXG: maximum gradient at
mitral valve; MVA: mitral valve area. *Patients with mitral stenosis.
TABLE 4. EFFECT OF PRE-OPERATIVE FUNCTIONAL
CAPACITY, TYPE OF MITRAL LESIONANDAETIOLOGY,
PRESENCE OF CORONARYARTERY DISEASE, HYPERTEN-
SION, ABLATION TECHNIQUEAND MITRAL PROCEDURE
Holter-ECG at 6 months
Test
statistics
AF (n = 17) NSR (n = 59)
n % n %
NYHA
class
II 3 17.6 5 8.5 χ2: 0.985;
p: 0.611
III 11 64.7 45 76.2
IV 3 17.6 9 15.3
Mitral
lesion
Stenosis 5 29.4 10 17 χ2: 2.126;
p: 0.547
Insufficiency 6 35.3 19 32
Mixed 6 35.3 30 51
Mitral
aetiology
Rheumatic 12 70.5 49 83
Ischaemic 1 5.8 2 3
Degenerative 4 23.7 8 14
Coronary
artery disease
Present 6 35.3 18 30 χ2: 0.189;
p: 0.664
Absent 11 64.7 41 70
Hypertension Present 9 52.9 29 49 χ2: 0.042;
p: 0.837
Absent 8 47.1 30 51
Mitral
procedure
Repair 5 29.5 4 7 Fχ2
p: 0.080
Replacement 12 70.5 55 93
AF: atrial fibrillation; NSR: normal sinus rhythm; χ2: Chi-square test.