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CARDIOVASCULAR JOURNAL OF AFRICA • Volume 30, No 6, November/December 2019
AFRICA
317
rheumatic fever, as many of these patients fail to comply with
penicillin prophylaxis when their cardiac symptoms improve as a
result of surgical intervention.
For those who get mechanical valves, the problem starts with
regular availability of warfarin itself.
10
Once they are on warfarin,
compliance, regular follow up and regular monitoring of their
coagulation profile has been a challenge because of lack of
facilities in almost all public institutions, and limited access to
well-equipped medical facilities. This study aimed at determining
factors associated with sub-optimal control of international
normalised ratio (INR) in children and young adults who had
received mechanical valve replacement for rheumatic valve
disease in the last few years.
Methods
This was a cross-sectional study of patients with prosthetic
heart valves who are on oral anticoagulation therapy. The study
included patients younger than 25 years who were being followed
up at the paediatric and adult cardiac clinics of Tikur Anbessa
Hospital and the Children’s Heart Fund Cardiac Centre, which
is also located within the premises of Tikur Anbessa Hospital,
Ethiopia.
The study was conducted from December 2014 to September
2015. The principal investigator collected data directly through
interviewing patients and attendants and by reviewing medical
records during this period. Socio-demographic data, including
age, gender, patient’s educational level, parental educational level,
parental occupation, income, residence, and distance from follow-
up health facility were collected on a pre-tested questionnaire.
Clinical data, including current cardiac symptoms, bleeding
episodes, strokes, frequency of follow-up visits, frequency
of INR determination, source of anticoagulant supply and
compliance were collected. For those who missed doses of
anticoagulants in the six months preceding the study, possible
reasons were inquired.
Patient records were retrieved and reviewed for age at the
time of surgery, pre-operative New York Heart Association
(NYHA) functional class, indication for valve replacement,
prosthetic valve position, type of prosthetic valve implanted,
compliance with recommended follow-up visit, INR checks,
major bleeding or thrombo-embolic events, and any post-surgical
hospital admissions. Where there were discrepancies between
patient reports and what had been documented in the medical
records, we used the information documented in the records.
Definition of adherence to follow-up visit, anticoagulant use
and INR determination in this study was based on the doctor’s
recommendation for each individual patient. The institutional
review committee approved the study.
INR determinations during the six-month period ranged
from one in the case of some of the patients to multiple values
in others. In those with multiple INR recordings, we determined
to which side the majority of the readings pointed. There were
few patients with mixed optimal and sub-optimal readings in
this study.
Our definition of optimal anticoagulation range (2.5–3.5) is
in the strict category. We chose the narrower range due to the
realities of our setting where frequent follow up, determination
of INR and adjustment of extreme boundaries of control is
difficult. Although INR values of 2.5–4.9 are considered to
be optimal by some,
2
the upper range of this value may have
predisposed our patients to bleeding due to lack of frequent
determination of their INR and subsequent dose readjustments.
The risk of bleeding increases once INR increases above 4.5.
11
Therefore, using a point close to this value would probably
have endangered our patients’ lives. We did not adjust for valve
position, namely mitral or aortic.
Statistical analysis
Data were entered into SPSS version 20 for Windows and
analysed. Demographic data were analysed using descriptive
statistics. Continuous variables are displayed as mean
±
standard
deviation (SD). Statistical significance was set at
p
<
0.05. The
chi-squared test and binary logistic regression methods were
used to test for association of factors to sub-optimal control of
anticoagulation.
Results
A total of 73 patients were included in the study and 42 (57.5%)
were female. Mean age of the participants was 21.5
±
3.1 years
(range 14–25 years) and mean follow-up period was 5.6
±
2.5
years (range 1–13 years). Sixty-three of the patients (86.3%) were
from urban areas while the rest were from semi-urban or rural
areas. Of the 73 patients, 35 (47.9%) had optimal control of their
INR. Table 1 shows the socio-demographic data and clinical
characteristics of the patients at the time of valve-replacement
surgery. With regard to educational status, 24 (32.9%) had
primary school education, 29 (39.7%) had secondary education,
19 (26.0%) had higher education and only one patient was
illiterate.
Valve brands used included St Jude mechanical valves in 40
(54.8%) patients, Edward’s mechanical valves in 12 (16.4%),
and other variants in 21 (28.8%) patients. Warfarin was the
Table 1. Baseline socio-demographic and clinical characteristics of
patients with prosthetic heart valves on oral anticoagulation therapy
Characteristics
Frequency Percentage
Gender
Female
42
57.5
Male
31
42.5
Age categories at surgery (years)
11–15
12
16.4
16–20
29
39.7
21–25
32
43.8
Residence
Urban
63
86.3
Semi-urban
9
12.3
Rural
1
1.4
NYHA functional class (before surgery)
I
–
–
II
12
16.4
III
29
39.7
IV
32
43.8
Indications for valve replacement (type of valve lesion)
Severe MR
16
21.9
Severe MS
13
17.8
Severe AR
4
5.5
Multi-valvular lesions
40
54.8
MR: mitral regurgitation; MS: mitral stenosis; AR: aortic regurgitation.