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CARDIOVASCULAR JOURNAL OF AFRICA • Volume 30, No 6, November/December 2019
316
AFRICA
Cardiovascular Topics
Factors associated with sub-optimal control of anti-
coagulation in patients with prosthetic heart valves
taking oral anticoagulants in a sub-Saharan African
setting
Tigist Chalachew, Dejuma Yadeta, Endale Tefera
Abstract
Background:
Replacement of diseased valves reduces the
morbidity and mortality rate associated with native valvular
disease but comes at the expense of risking complications
related to the implanted prosthetic device. Establishing the
desired anticoagulation level in a sub-Saharan African setting
may be a challenge.
Objectives:
This study was conducted to determine the chal-
lenges of maintaining a desired level of anticoagulation and
factors associated with sub-optimal anticoagulation in patients
with prosthetic heart valves on chronic anticoagulation.
Methods:
We reviewed 73 patients who had undergone pros-
thetic valve replacement for chronic rheumatic valvular heart
disease and were taking warfarin. The follow up ranged from
one to 13 years. We studied international normalised ratio
(INR) profiles of the patients for the six months preceding
the study and defined optimal control as an INR of 2.5–3.5.
We aimed to determine if there were factors associated with
sub-optimal control of INR.
Results:
Forty-two patients (57.5%) were female. Mean age
of the participants was 21.5
±
3.1 years (range 14–25 years).
Warfarin was the anticoagulant in 55 (75.3%) of the patients
and 18 (24.7%) were on combined warfarin and aspirin anti-
coagulation. Thirty-five (47.9%) patients had optimal control
of their INR. Educational level of primary school or less,
distance from follow-up medical facility of more than 300 km,
quarterly or less-frequent check-up visit, and public health
institution as a source of free warfarin supply were found to
be significantly associated with sub-optimal control of INR.
Conclusion:
Educational level, distance from follow-up facil-
ity, number of follow-up visits and source of warfarin supply
were found to be significantly associated with sub-optimal
control of INR.
Keywords:
anticoagulation, valve replacement, warfarin, sub-
Saharan Africa, rheumatic heart disease
Submitted 20/12/18, accepted 27/4/19
Published online 24/5/19
Cardiovasc J Afr
2019;
30
: 316–320
www.cvja.co.zaDOI: 10.5830/CVJA-2019-024
Among patients who undergo cardiac valve replacement,
approximately 60% receive mechanical valves, and replacement
of a diseased heart valve with a prosthetic valve exchanges the
native disease for potential prosthesis-related complications.
1,2
Replacement of diseased valves reduces the morbidity and
mortality rates associated with native valvular disease but comes
at the expense of risking complications related to the implanted
prosthetic device.
3
These complications include primary valve
failure, prosthetic valve endocarditis and thrombosis, thrombo-
embolism, haemorrhage and mechanical haemolytic anaemia.
4-7
The frequency of serious complications depends upon the valve
type and position and other clinical risk factors.
8
Thrombo-
embolic and anticoagulation-related problems are by far the
most frequent complications of mechanical valves.
1,2,8
Chronic rheumatic heart disease is still prevalent and is a
major public health problem in sub-Saharan Africa. In recent
years, there has been a glimmer of hope for many patients to
get surgical intervention in their local environment through
locally established facilities,
9
overseas charity referrals or visiting
surgical missions. However, determining the optimal strategy to
treat such sub-Saharan African patients is a challenge.
Colleagues from Cameroun recently reported their experience
with 233 patients who had undergone mechanical valve
replacement.
9
Although the surgical results and mid-term event-
free survival was good in their report, that may not be the
case in other parts of sub-Saharan Africa, primarily due to
issues related to anticoagulation. Tissue valves and valve repair
strategies tend to be short lived because of the recurrence of
Department of Pediatrics and Child Health, School of
Medicine, Hawassa University, Hawassa, Ethiopia
Tigist Chalachew, MD
Department of Internal Medicine, Division of Cardiology,
School of Medicine, Addis Ababa University, Addis Ababa,
Ethiopia
Dejuma Yadeta, MD
Department of Pediatrics and Adolescent Health, Division
of Cardiology, Faculty of Medicine, University of Botswana,
Gaborone, Botswana
Endale Tefera, MD,
endalet2008@gmail.com