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CARDIOVASCULAR JOURNAL OF AFRICA • Volume 28, No 1, January/February 2017
62
AFRICA
Echocardiographic procedures and measurements
were performed according to the American Society of
Echocardiography (ASE) guidelines.
13
M-mode echocardiograms
were derived from two-dimensional (2D) images. The M-mode
cursor on the 2D scan was moved to specific areas of the heart
to obtain measurements, according to the recommendation
of the committee on M-mode standardisation of the ASE.
Doppler indices of left ventricular (LV) diastolic filling were
obtained. Complete Doppler studies were performed according
to the recommendations of the ASE (Fig. 1). From the M-mode
measurements, LV dimensions and function (LV ejection
fraction) were derived. LV mass was calculated using the
recommended method from the ASE:
1.04 [(LVIDd
+
PWTd
+
IVSTd)
3
– (LVIDd)
3
] – 13.6 g.
14
where LVIDd is left ventricular internal diameter at end-diastole,
PWTd is posterior wall thickness in diastole, and IVSTd is
interventricular septal thickness in diastole.
For diastolic function, left atrial (LA) size (both antero-
posterior diameter and planimetry) and pulse-wave mitral-valve
(MV) inflow (early and late peak diastolic velocities, which
measure the E/A ratio and the deceleration time and MV A-wave
duration) were measured.
Echocardiography examinations also included assessment of
valvular architecture, a semi-quantitative estimate of the severity
of valvular regurgitation, and determination of the presence of
pericardial effusion. Other abnormalities, such as evidence of
pulmonary arterial hypertension, were also noted.
Statistical analysis
Patients whose echocardiograph was performed within four
weeks prior to and two weeks post enrollment were included in
this analysis. Continuous parameters are summarised as means
and standard deviation, and categorical parameters by absolute
and relative frequencies.
For patients who had their E/A ratios recorded, grade 1 was
defined as E/A
<
0.8, grade 2 as E/A between 0.8 and 1.5, and
grade 3 as E/A ratio
>
1.5. If a patient had a missing E/A ratio,
then the grade was defined using the E-wave deceleration time as
follows: grade 1 as E-wave
>
200 ms, grade 2 as E-wave 160–200
ms, and grade 3 as E-wave
<
160 ms.
The associations between echo parameters and clinical
outcomes were examined using Cox regression models. The
univariate associations between each predictor and outcome
were examined. The linearity of associations between
continuously distributed predictors and each outcome was
assessed using restricted cubic splines with four knots with a test
of the significance of the non-linear terms. If the association was
non-linear, a readily interpretable transformation was chosen
through examination of plots of the predicted log hazard ratio
against the value of the predictor and changes in Akaike’s
information criterion.
For the outcome of 180-day mortality, the associations
with creatinine, heart rate and posterior wall thickness were
all significantly non-linear. We chose to model creatinine as a
quadratic polynomial, and heart rate and posterior wall thickness
using linear splines with one knot where the association between
predictor and outcome appeared to change.
Table 1. Patient characteristics overall and by ejection fraction groups
Patient characteristics
Overall
(
n
=
954)
EF
<
50%
(
n
=
654)
EF ≥ 50%
(
n
=
243)
p
-value
Age, years, mean
±
SD 52.3
±
18.24 52.3
±
17.64 53.0
±
19.58 0.62
Male gender,
n
(%)
469 (49.2)
342 (52.3)
101 (41.7)
0.0050
Black Africans,
n
(%)
939 (99.1)
646 (99.1)
242 (99.6)
0.68
Hypertension,
n
(%)
532 (56.0)
369 (56.7)
138 (57.0)
0.93
Hyperlipidaemia,
n
(%)
84 (9.0)
58 (9.1)
23 (9.6)
0.80
History of smoking,
n
(%)
93 (9.8)
64 (9.8)
17 (7.1)
0.20
Malignancy,
n
(%)
13 (1.4)
10 (1.5)
3 (1.2)
1.00
History of cor pulmo-
nale,
n
(%)
67 (7.1)
34 (5.2)
30 (12.4)
0.0002
Diabetes mellitus,
n
(%)
109 (11.4)
72 (11.0)
26 (10.7)
0.88
Peripheral oedema,
n
(%) 631 (67.1)
448 (69.6)
146 (60.8)
0.014
Rales,
n
(%)
533 (63.8)
382 (65.3)
130 (59.6)
0.14
BMI, kg/m
2
, mean
±
SD 24.9
±
5.84 24.8
±
5.62 24.7
±
6.10 0.82
Systolic BP, mmHg,
mean
±
SD
130.7
±
33.51 127.9
±
32.16 137.2
±
36.35 0.0006
Diastolic BP, mmHg,
mean
±
SD
84.5
±
21.04 84.0
±
20.52 85.5
±
22.04 0.34
Heart rate, bpm, mean
±
SD
104.0
±
21.35 105.0
±
21.02 101.1
±
22.69 0.016
LVEF, %, mean
±
SD 39.4
±
16.43 31.8
±
10.04 60.6
±
9.65
<
0.001
Creatinine level, mg/dl,
mean
±
SD
1.4
±
0.99 1.4
±
0.99 1.3
±
1.07 0.54
BUN, mg/dl, mean
±
SD 34.7
±
31.59 35.1
±
29.58 35.9
±
38.35 0.79
Sodium level, mEq/l,
mean
±
SD
135.2
±
6.57 135.0
±
6.72 135.5
±
6.3
0.27
eGFR, ml/min/1.73 m
2
,
mean
±
SD
84.4
±
47.91 81.7
±
44.08 90.8
±
57.97 0.032
Haemoglobin, g/dl,
mean
±
SD
12.1
±
2.41 12.3
±
2.30 11.8
±
2.64 0.019
Glucose level, mg/dl,
mean
±
SD
109.8
±
49.92 110.4
±
51.95 106.1
±
41.93 0.22
(mmol/l)
(6.09
±
2.77) (6.13
±
2.88) (5.89
±
2.33)
Prior medication use,
n
(%)
ACE inhibitor
180 (32.4)
134 (34.9)
40 (24.8)
0.022
Loop diuretics
215 (39.4)
152 (40.1)
57 (36.5)
0.44
β
-blockers
97 (17.9)
69 (18.3)
26 (16.7)
0.65
Digoxin
103 (18.9)
80 (21.1)
22 (13.9)
0.053
Hydralazine
3 (0.6)
2 (0.5)
1 (0.6)
1.00
Nitrates
10 (1.8)
8 (2.1)
2 (1.3)
0.73
Aldosterone inhibitor
101 (18.5)
77 (20.4)
22 (13.8)
0.075
Statins
27 (5.0)
18 (4.8)
9 (5.7)
0.68
Aspirin
122 (22.2)
91 (24.0)
29 (18.1)
0.13
Anticoagulants
31 (5.7)
22 (5.9)
7 (4.4)
0.49
Aetiology of heart fail-
ure,
n
(%)
Hypertensive CMP
380 (40.9)
274 (42.5)
86 (37.6)
Idiopathic dilated
CMP
129 (13.9)
120 (18.6)
2 (0.9)
Rheumatic heart
disease
133 (14.3)
75 (11.6)
55 (24.0)
Ischaemic heart
disease
71 (7.6)
57 (8.8)
10 (4.4)
Peripartum cardiomy-
opathy
72 (7.8)
59 (9.2)
2 (0.9)
Pericardial effusion
tamponade
45 (4.8)
22 (3.4)
23 (10.0)
HIV cardiomyopathy
22 (2.4)
12 (1.9)
8 (3.5)
Endomyocardial
fibrosis
11 (1.2)
2 (0.3)
8 (3.5)
Other
66 (7.1)
24 (3.7)
35 (15.3)
EF, ejaculation fraction; BMI, body mass index; LVEF, left ventricular ejection
fraction; BUN, blood urea nitrogen; ACE, angiotensin converting enzyme; CMP,
cardiomyopathy; eGFR, estimated glomerular filtration rate.