Cardiovascular Journal of Africa: Vol 31 No 4 (July/August 2020)

CARDIOVASCULAR JOURNAL OF AFRICA • Volume 31, No 4, July/August 2020

188

AFRICA

While there is evidence that female gender, smoking and low

income are associated with bleeding complications, none of these

factors had an association with bleeding complications in the

current study.

35,36

Theabove factors affect theanticoagulationeffect

of warfarin and consequently lead to bleeding complications.

Unfortunately, our study was not powered enough to detect the

influence of these factors on the risk of bleeding.

In our study, the incidence of thromboembolic complications

was 2.8 per 100 person-years, higher than the rate of one to

two per 100 patient-years in the Western world cohorts.

8,16

This

is concerning as our cohort was younger than those in the

developed world, whose thromboembolic complications are

likely to be influenced by several co-morbidities that are risk

factors for atherosclerosis. For this reason, our results suggest

a high rate of thromboembolic complications in our young

population with MHV prostheses. These complications were not

associated with hypertension or atrial fibrillation.

Like bleeding complications, prolonged exposure to

sub-optimal levels of anticoagulation in our cohort may

partly explain the high rate of thromboembolic complications

among our patients. Patients with sub-optimal levels of

anticoagulation often present with a clear predominance of over-

anticoagulation.

This fact most likely explains a preponderance

of thromboembolic over major haemorrhagic events in our

cohort.

Theobservationof atwo-foldincreasedriskof thromboembolic

complications in those with education compared to those who

were uneducated may be explained by the fact that educated

patients are more likely to reside in the city and hence survive

thromboembolic complications because of their proximity to

healthcare services. Although ageing, smoking, female gender

and alcohol intake are linked to an increased risk of bleeding and

thromboembolic complications, these factors were neutral in the

present study.

20,35

Again, the young age of our participants may

have influenced the findings.

We are aware of the limitations of our study. Being a

retrospective study, it was not possible to document complications

as they happened. Furthermore, selection bias cannot be excluded

in this study design, as fatal warfarin-related complications that

led to mortality were likely to be missed. Also, patients’ ability to

recall events may have been limited, especially those with minor

impacts. However, we reviewed the medical records to confirm

all reported complications. Also, because of a variable number

of days between each patient’s visit, the TTR calculation might

have over- or underestimated time in therapeutic window. As

most operations were not done in Botswana, information on

the type (model) of valves was missing. Lastly, being a hospital-

based study, patients with severe morbidity that limited their

clinic attendances were likely to be missed.

Conclusion

This study shows high rates of bleeding and thromboembolic

events in a young cohort of patients with MHVs in a developing

country. Also, most of the patients had poor anticoagulation

control. Efforts aiming at improving the care of patients

with mechanical valves are necessary to reduce the burden of

complications in this young population. Decentralisation of

INR testing to their local facility might be one way of improving

anticoagulation in these patients.

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