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CARDIOVASCULAR JOURNAL OF AFRICA • Volume 30, No 3, May/June 2019
AFRICA
169
Gaborone between 1 August 2016 and 31 July 2018. PMH is a
tertiary referral and university teaching hospital that not only
serves patients from the city but also patients from around the
country.
We sought ethical approval for this study from the University
of Botswana, Ministry of Health and Princess Marina ethical
review committees. The study was conducted as per the principles
of the Declaration of Helsinki. Written informed consent was
obtained from all study participants.
The study enrolled consecutive patients aged 18 years
and older, with a documented diagnosis of AF on an
electrocardiogram (ECG), who presented to the medical wards
and clinics. Data were collected through patient interviews,
a review of electronic medical records, and physical and
echocardiographic examinations. The presence of hypertension,
ischaemic heart disease, valvular heart disease, heart failure,
diabetes mellitus, stroke and transient ischaemic attack (TIA),
and hyper/hypothyroidism was determined in all the patients. A
history of smoking, alcohol consumption, antihypertensive and
antidiabetic medication use, and previous cardiac surgery was
also determined.
We measured blood pressure, pulse rate, height and weight in
all participants. Patients’ weight (to the nearest kg) and height (to
the nearest 1 cm) were measured on individuals in light clothing
without shoes. Body mass index (BMI) was calculated as weight
(kg) divided by height squared (m
2
), and participants with a
BMI of
≥
30 kg/m
2
were classified as obese.
11
We conducted three
blood pressure measurements after 10 minutes of rest, and the
mean of the three measurements was recorded. Hypertension was
diagnosed if blood pressure was
≥
140/90 mm Hg or if the subject
was receiving antihypertensive medication.
12
Diabetes was defined
as a prior documented diagnosis of diabetes in patients’ medical
records or the use of insulin or oral hypoglycaemic agents.
A diagnosis of heart failure was reached based on a
previously documented diagnosis or diagnosed at enrolment,
based on the European Society of Cardiology criteria.
13
Patients’
serum creatinine, urea, alanine aminotransferase, aspartate
aminotransferase and thyroid function test results were also
recorded. The risk for stroke among patients with non-valvular
AF was stratified by using the CHA
2
DS
2
-VASc score.
14
The
HAS-BLED score was used to assess the risk of bleeding among
patients who qualified for anticoagulation.
14,15
Two-dimensional, motion mode (M-mode) and Doppler
transthoracic echocardiography were performed to assess cardiac
structure and function. Assessment of dimensions, systolic and
diastolic function of the ventricles, valvular function, rheumatic
heart disease and pulmonary hypertension was done using
standard guidelines.
16-20
Patients with heart failure (HF) were
classified into those with preserved ejection fraction (HFpEF)
when left ventricular ejection fraction (LVEF) was
≥
50%,
mid-range ejection (HFmrEF) when the LVEF was 40–49%, and
reduced ejection fraction (HFrEF) when LVEF was
<
40%.
20
Valvular AF was defined as AF that occurred in the presence
of mechanical prosthetic heart valves or moderate-to-severe
rheumatic mitral stenosis. Non-valvular AF was referred to as
AF that occurred in the absence of mechanical prosthetic heart
valves and the absence of moderate-to-severe rheumatic mitral
stenosis.
21,22
The primary outcome of interest was 12-month all-cause
mortality. We obtained this information by telephone calls to
participants or their relatives or from the patients’ electronic
medical records.
Statistical analysis
There was no pre-calculation of the sample size. The study
enrolled consecutive patients who presented to the medical
wards and clinics between 1 August 2016 and 31 July 2018. All
statistical analyses were conducted using Stata (version 13, Stata
Corp, College Station, Texas, USA). Continuous variables were
summarised using the mean (SD), and categorical variables were
expressed in percentages. Comparisons of data between valvular
and non-valvular AF patients were conducted using Pearson’s
chi-squared analysis or Fisher’s exact test for categorical
variables, and unpaired Student’s
t
-test for continuous variables.
All-cause mortality was assessed as the number of patients who
died during the 12-month follow-up period, divided by the total
number of participants. A
p
-value less than 0.05 was considered
statistically significant.
Results
Of the 138 patients who were enrolled, the majority (97.8%)
were of black African origin. Follow-up data were available
in all participants. Table 1 shows the baseline characteristics
of patients at enrolment. The mean (SD) age of the patients
was 66.7 (17.2) years and 63.8% of patients were female.
Hypertension (59.4%), rheumatic heart disease (37.7%) and
heart failure (35.5%) were frequent among participants. Patients
with rheumatic heart disease had moderate-to-severe mitral
regurgitation (35, 67.3%), moderate-to-severe mitral stenosis
(20, 38.4%), moderate-to-severe aortic regurgitation (four, 7.7%),
or moderate-to-severe aortic stenosis (two, 3.8%). Twenty-five
(18.1%) patients had mechanical heart valves, the majority (92%)
being mitral valve prostheses.
Chronic kidney disease (15.2%), cigarette smoking (9.4%),
diabetes mellitus (8%) and alcohol consumption (5.1%)
were uncommon. None of the participants had hyper- or
hypothyroidism. Overall, the mean (SD) heart rate was 83.9
(24.9) beats/minutes. The left atrial diameters were enlarged to
a mean (SD) value of 4.8 (1.0) cm and pulmonary hypertension
was diagnosed in 37% of the patients. The mean (SD) LVEF
was 52.8 (17.7) and about a quarter (26.8%) of the patients had
HFrEF, and 13.0% presented with HFmrEF (50%).
The mean (SD) CHA
2
DS
2
-VASc score for patients with
non-valvular AF was 3.6 (1.5), with the majority (89.4%)
scoring
≥
2. The median HAS-BLED score for patients was
2.0 (IQR 1.0–3.0), with 58.1% scoring
≤
2. For non-valvular
AF with CHA
2
DS
2
-VASc scores
≥
2, 73.8% of patients were
prescribed anticoagulation therapy [66.7% warfarin and 7.1%
novel oral anticoagulants (NOACs)]. Anticoagulant therapy
was not prescribed in 26.2% of patients with CHA
2
DS
2
-VASc
scores
≥
2. Beta-blockers (70.3%) and digoxin (37%) were
the only prescribed rate-controlling medications. Amiodarone,
calcium channel blockers and electrical cardioversion were not
documented among our participants. Angiotensin converting
enzyme (ACE) inhibitors, furosemide and spironolactone were
also frequently used.
Results in Table 2 compare the clinical and biomedical data
from patients with valvular and non-valvular AF. Compared to