39 / 76
CARDIOVASCULAR JOURNAL OF AFRICA • Volume 28, No 2, March/April 2017
AFRICA
105
All patients underwent transthoracic echocardiography using
a Vivid S5 (GE Healthcare) echocardiography device and Mass
S5 probe (2–4 MHz). Standard two-dimensional and colour-flow
Doppler evaluations were acquired according to the guidelines
of the American and European Societies of Echocardiography.
4
The EF was measured according to Simpson’s method. Left
atrial diameter was measured in parasternal long-axis view using
two-dimensional echocardiography at the end-systole of left
ventricular systole.
Study exclusion criteria were patients with paroxysmal or
persistent AF, being on anti-arrhythmia medication, patients
who underwent pharmacological or electrical cardioversion
before CABG surgery due to reasons other than AF, patients
who underwent other cardiac procedures in addition to CABG
or who were planned to undergo emergency surgery, and patients
who had significant valvular disease or prosthetic valvular
disease.
Levels of 25-hydroxy (OH) Vitamin D, calcium and other
biochemical and haematological parameters were measured
following a fasting period of eight hours. Serum 25-(OH) Vitamin
D levels were measured by chemiluminescence immunoassay
using a Lıaıson analyser (DiaSorin Inc). Vitamin D deficiency
was defined as serum levels of 25-(OH) Vitamin D
<
20 ng/ml
and Vitamin D insufficiency was defined as a level of 20–29 ng/
ml. Plasma levels of 25-(OH) Vitamin D
>
30 ng/ml were defined
as normal.
Statistical analysis
Statistical analysis was performed using the SPSS (version 20.0,
SPSS Inc, Chicago, Illinois) software package. Continuous
variables are expressed as mean
±
standard deviation (mean
±
SD) and categorical variables as percentage (%). The
Kolmogorov–Smirnov test was used to evaluate the distribution
of variables. The Student’s
t
-test was used to evaluate continuous
variables showing a normal distribution, and the Mann–Whitney
U
-test was used to evaluate variables that did not show a
normal distribution. A
p
-value
<
0.05 was considered statistically
significant.
Results
This study included 128 consecutive patients, of whom 41 (32%)
developed POAF. The main characteristics of patients who
developed POAF and those who did not are presented in Table 1.
All patients were on beta-blocker and statin therapy, and 93.7%
were on angiotensin converting enzym inhibitor/angiotensin
receptor blocker therapy. Comparisons of different laboratory
and echocardiographic parameters are presented in Table 2.
Univariate analysis identified age, DM, history of transcient
ischaemic attack/stroke, COPD, heart failure, left atrial
diameter, EF, and urea, creatinine, uric acid, potassium, calcium
and 25-(OH) Vitamin D levels as significant factors for the
development of POAF. Multivariate regression models revealed
that COPD, DM, HF and left atrial diameter increased the
probability of POAF independent of confounding factors (OR:
28.737, 95% CI: 0.836–16.118,
p
<
0.001 for COPD; OR: 11.486,
95% CI: 0.734–11.060,
p
=
0.001 for DM; OR: 15.430, 95% CI:
0.989–7.649,
p
=
0.006 for HF; OR: 1.245, 95% CI: 0.086–6.431,
p
=
0.011 for left atrial diameter).
Discussion
AF is a growing global health concern and is linked to a
wide range of medical complications, including heart failure,
ischaemic stroke and death. It is estimated that AF may account
for 10 to 15% of all strokes, with an associated increased
mortality rate of up to 1.9-fold higher than without AF.
5
COPD, HF, DM and left atrial diameter were found to be
independent variables predicting the development of POAF. In
previous studies, advanced age, male gender, chronic heart failure,
pre-operative AF attacks, COPD, chronic renal disease, DM
and the metabolic syndrome were reported to be pre-operative
clinical parameters predicting the development of POAF.
6
COPD is an independent risk factor for arrhythmias, especially
AF and cardiovascular morbidity and mortality.
7
COPD was
found to be an important variable predicting the development of
postoperative AF in this study. We believe that the relationship
between COPD and POAF depends on hypoxia, hypercapnia,
acidosis and inflammation.
AF is one of the most common co-morbidities in patients
with HF, while HF is also common in AF patients. Previous
studies reported that the prevalence of AF in patients with
chronic HF ranged from 15 to 50%.
8
HF was found to be an
important variable predicting the development of postoperative
AF in our study.
Aksakal and co-workers found DM increased the risk of
developing AF.
9
In our study, DM was found to be an important
variable predicting the development of postoperative AF.
The Framingham Offspring study found that individuals
with 25-(OH) Vitamin D
<
37.5nmol/l had a hazard ratio of
1.62 for the development of cardiovascular disease compared
to those with a level of
≥
37nmol/l.
10
Furthermore, Vitamin D
insufficiency was associated with endothelial dysfunction and
subclinical atherosclerosis.
11
Another study pointed out that
25-(OH) Vitamin D levels were significantly lower in patients
with coronary artery disease than in those without.
12
VDRs are found in myocytes and fibroblasts in the heart.
13
A number of animal studies have confirmed that VDRs play an
important role in cardiac hypertrophy.
14
The risk of new-onset AF is significantly higher with increased
left atrial diameter and left atrial volume.
15
In our study, left atrial
Table 1. Patient characteristics
Patient characteristics
POAF
p
-value
Present
Absent
Age (mean
±
SD)
67.6
±
8.6 63.9
±
9.8
0.047
Body mass index (mean
±
SD)
(median)
27.2
±
3.7
(25.8)
26.9
±
4.1
26.7
0.755
Gender,
n
(%)
Male
35 (85.4)
77 (88.5)
0.616
Female
6 (14.6)
10 (11.5)
Hypertension,
n
(%)
+
40 (97.6)
77 (88.5)
0.104
–
1 (2.4)
10 (11.5)
Diabetes mellitus,
n
(%)
+
31 (75.6)
26 (29.9)
<
0.001
–
10 (24.4)
61 (70.1)
TIA/stroke,
n
(%)
+
5 (12.2)
1 (4.7)
0.013
–
36 (87.8)
86 (98.9)
COPD,
n
(%)
+
15 (36.6)
5 (5.7)
<
0.001
–
5 (5.7)
82 (94.3)
Heart failure,
n
(%)
+
12 (29.3)
3 (3.4)
<
0.001
–
29 (70.7)
84 (96.6)
POAF, postoperative atrial fibrillation, TIA, transient ischaemic attack, COPD,
chronic obstructive pulmonary disease.