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CARDIOVASCULAR JOURNAL OF AFRICA • Volume 25, No 5, September/October 2014
246
AFRICA
One-way analysis of covariance (ANOVA) and the Tukey
post hoc
analysis were used to compare three or more normally
distributed samples. In the case of abnormally distributed data,
the Kruskal–Wallis test was used for more than three samples,
whereas the Mann–Whitney
U
-test was used to compare two
samples based on the adjusted Bonferroni correction. The
cross tabulation table was used to compare categorical variables
(chi-square, Fisher, Mantel–Haenszel test).
All variables were initially tested individually by univariate
analysis. Then, variables with a
p
-value of
≤
0.25 in univarate
analysis were applied into the logistic regression model to
identify independent predictors for mortality. Late survival rates
were calculated using the Kaplan–Meier method and statistical
significance was calculated with the log-rank test. A
p
-value of
<
0.05 was considered statistically significant.
Results
The mean follow up was 48.7
±
50.8 months (range 0–240).
Early postoperative complications are listed in Table 4.
Arrhythmias occurred in 26 patients (22.8%), of whom 13 had
atrial fibrillation. All received medical therapy. The other 13
(11.4%) needed permanent pacemaker implantation. Despite
optimal selection of the prosthesis to minimise the incidence
of pacemaker implantation, we found no correlation among
peri-operative risk factors, including prosthesis type (
p
=
0.457).
However, pre-operative values of NYHA (
p
<
0.001) and logistic
EuroSCORE (
p
=
0.023) were found to be significantly correlated
with peri-operative risk factors.
Renal failure was present in 11 patients (9.6%), of whom
seven patients needed transient haemodialysis after surgery.
Four (3.5%) required long-term haemodialysis. Among 30
patients (26.3%) requiring prolonged mechanical ventilation
(> 24 hours), nine (7.9%) had respiratory infection. There was
a significant correlation between LMCA stenosis and infection
(
p
=
0.049).
Three patients (2.6%) developed cerebrovascular accident and
two recovered fully before hospital discharge. Six patients needed
re-operation, of whom three were operated on due to excessive
bleeding. The rest were operated on for cardiac tamponade. The
mean length of ICU and hospital stay was 6.4
±
4.3 and 18
±
12.8
days, respectively.
In-hospital mortality was seen in 19 patients (16.7%). The
mortality rate was 8.7% in 10 patients who underwent isolated
AVR. The mean time to death after surgery was 17
±
15.61 days
(range 0–48 days). The major causes of in-hospital mortality
were low-cardiac output syndrome in eight patients (42.1%),
respiratory insufficiency or infection in six (31.5%), multi-organ
failure in four (21%), and stroke in one patient (5.2%). Univariate
analysis revealed the following variables to be associated with
operative mortality: LMCA stenosis (
p
=
0.032), NYHA
≥
III (
p
=
0.002) and EuroSCORE
≥
15 (
p
<
0.001).
During the follow-up period, 28 late deaths (29.4%) occurred.
A total of 98.9% completed the follow-up period. Based on
the univariate analysis, possible risk factors for long-term
mortality were type of prosthesis (
p
=
0.037), EuroSCORE
≥
15 (
p
=
0.013), postoperative pacemaker implantation (
p
=
0.008), respiratory infection (
p
=
0.004), and haemodialysis (
p
=
0.004). Mortality rate was higher in the mechanical valve
group. Multivariate analysis identified the following variables
as independent predictors of mortality: cross-clamp time (
p
=
0.043) and CPB time (
p
=
0.033).
Furthermore, although cerebrovascular accidents, either
from intracranial haemorrhage or ischaemic stroke, were the
leading cause of death (
n
=
8). Respiratory failure (
n
=
7) and
cardiovascular disease (
n
=
6) accounted for 46.4% of the late
mortalities. Three patients died from renal insufficiency, while
one had a neoplasm, one had mesenteric ischaemia, and two
patients suffered from sudden death.
One, three, five, 10 and 15-year survival rates were 76.2
±
4.12, 69.03
±
4.44, 61.40
±
5.13, 43.48
±
7.42 and 24.15
±
9.65%,
respectively (Fig. 1). Patients with combined surgery showed
lower survival rates (log-rank,
p
=
0.0498) (Fig. 2).
During follow up, late complications were intracranial
haemorrhage inone patient, stroke inone patient and re-operation
for vegetations and paravalvular leakage in two patients (at 10
years and one year after the initial surgery, respectively).
The patients were questioned on symptom relief and an active
lifestyle. Among 65 long-term survivors, activity level was good
in 53 (81.5%) and poor in two (3.1%). The patients reported
improved quality of life compared to their pre-operative status.
We were unable to reach 10 patients to determine their activity
levels.
Discussion
Since 1970, men and women worldwide have gained slightly
more than 10 years of life expectancy overall, but they spend
more years living with injury and illness. Non-communicable
diseases, such as cancer and heart disease, have become the
dominant causes of death and disability worldwide.
6
With the introduction of improved surgical techniques and
prolonged life expectancy, an increasing number of elderly
people are considered candidates for valve surgery. According to
the Euro Heart Survey, intervention was rejected in up to 33%
of patients, despite their severe symptomatic aortic stenosis (AS)
status.
7
However, the natural prognosis of severe AS is associated
with a life expectancy of less than five years.
8,9
In our study, we
found that mortality rates in elderly patients (
≥
70 years) who
underwent timely aortic valve operations were very low. This
encourages us to refer especially the elderly with aortic stenosis
for surgery.
Several studies have showed that valve replacement can be
performed with an acceptable mortality rate and high long-term
survival rate.
10-12
Kohl
et al
.
13
reported their operative mortality
Table 4. Postoperative complications
Variable
Number
%
Arrhythmia
26
22.8
Pacemaker implantation
13
11.4
Prolonged mechanical ventilation
30
26.3
Bleeding total (ml)
641
±
480.56
Re-operation
Bleeding
3
2.6
Tamponade
3
2.6
Cerebrovascular accident
3
2.6
Renal failure
11
7.9
Haemodialysis (permanent)
4
3.5
Pulmonary failure
9
7.9