The incidence of congenital bicuspid aortic valve (BAV) has been reported to be between 1% and 2% of live births. These reports have originated from different populations and different geographic areas.
During a recent study undertaken to echocardiographically identify the prevalence of rheumatic heart disease (RHD) in Rwandan school children using the World Heart Federation (WHF) 2012 criteria, we reported on 2,501 subjects between the ages of 6 years and 16 years. During our analyses we noted the absence of BAV in this previously unstudied sub-Saharan population of children (BAV is an important differential diagnosis in RHD affecting the aortic valve). Based upon the available literature, we had expected to identify between 25 and 50 subjects with BAV in this Rwandan study population.
We initially entertained the possibility that our echocardiographic interrogations using the focused WHF 2012 echocardiographic criteria of these 2,501 children were inadequate—perhaps compared with a more comprehensive transthoracic echocardiographic diagnostic protocol. We subsequently re-reviewed the echocardiographic records, but our original conclusion regarding BAV from the data remained unchanged.
We then considered the possibility that because BAV is more easily visualized in an adult population (due in part to calcification) and that because the mean age of our Rwandan children population was only 11.2 years, the BAV presence was not observed and went unreported. We also considered the possibility that there is a—perhaps genetic—difference(s) in this sub-Saharan population.
Since several other studies from sub-Saharan African countries using the same WHF 2012 criteria to determine RHD prevalence in sub-Saharan Africa have been published, we attempted to determine whether our findings with respect to BAV in Rwandan children were atypical. Two published studies describing a total of 4,027 children in Uganda did not specifically report BAVs. We have confirmed this with those authors by correspondence.
Therefore, of this total of 6,078 sub-Saharan children identified in the published literature, the possible absence/nonreporting of BAV compared with the expected number of subjects (60–120) is not only surprising but is quite noteworthy.
In addition to these published reports, we contacted other groups of investigators known to have recently screened children in sub-Saharan Africa including the British Society of Echocardiography (from South Africa) and the American Society of Echocardiography (from Kenya), both of whom, in retrospect, reported no findings of BAVs in the several thousand additional patients examined.
We cannot currently explain this observation. However, the apparent absence or very low incidence of BAV is intriguing and deserves further investigation/explanation.