Are minor echocardiographic changes associated with an increased risk of acute rheumatic fever or progression to rheumatic heart disease?
Introduction
Prior to the introduction of echocardiography, diagnosis of rheumatic heart disease (RHD) was primarily based on auscultation. However, it has been shown that auscultation alone is neither sensitive [1] nor specific [2], [3]. Increased availability of portable high-quality echocardiography to assess heart valve morphology and function has resulted in significant debate regarding the echocardiographic diagnosis of RHD. This debate has intensified owing to the publication of a number of RHD echocardiographic screening studies that have utilized differing diagnostic criteria [1], [2], [4], [5]. To address this issue, in 2012 the World Heart Federation (WHF) published echocardiographic criteria for the diagnosis of RHD in the absence of a history of acute rheumatic fever (ARF) [6]. These WHF criteria include a category of “Borderline” RHD that encompasses minor heart valve abnormalities of uncertain clinical significance.
The importance of such minor abnormalities in a setting of high RHD risk was highlighted by a recent Australian RHD echocardiographic screening study (gECHO (getting Every Child's Heart Okay)) [7]. Of 3946 high-risk Aboriginal and/or Torres Strait Islander children, 0.9% met the WHF criteria for Definite RHD while 1.7% met criteria for Borderline RHD. Furthermore, mitral regurgitation (MR) was detected in 22.1%, aortic regurgitation (AR) in 4.4%, morphological abnormalities of the mitral valve (MV) in 2.9%, and abnormalities of the aortic valve (AV) in 0.9%.
The clinical significance of a diagnosis of Borderline RHD or other non-diagnostic valvular abnormalities in individuals without a history of ARF remains unclear and has been identified as a priority for investigation [6], [8]. If these abnormalities represent the earliest changes of RHD then offering such individuals regular secondary prophylaxis may prevent disease progression. In contrast, if they are simply a variant of normal echocardiographic findings then unwarranted treatment should be avoided.
The Rheumatic Fever Follow-Up Study (RhFFUS) aimed to clarify the significance of minor echocardiographic changes by determining if they were associated with an increased risk of ARF or progressive heart damage consistent with the development of Definite RHD.
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Methods
The methodology of the RhFFUS study has been described previously [9]. Briefly, RhFFUS was a prospective cohort study of Aboriginal and/or Torres Strait Islander children aged 8 to 18 years residing in 32 remote Australian communities. Participants comprised a subset of children who had received an echocardiogram during the earlier gECHO study between September 2008 and November 2011 [7]. They were enrolled in RhFFUS between 2.5 and 5 years after their baseline gECHO echocardiogram.
Cases were
Results
447 individuals were enrolled. Five participants (2 Cases and 3 Controls) who had a notified episode of ARF prior to gECHO were excluded.
Of the 171 potential Cases identified from gECHO, 119 (70%) were successfully enrolled. There were no significant differences in the age, gender or ethnicity of enrolled and non-enrolled Cases (data not shown).
While the RhFFUS methodology prescribed two Matched Controls per Case, there was an excess of Controls enrolled as the study team was unable to locate
Discussion
We have shown, for the first time, that children diagnosed with Borderline RHD by the WHF criteria [6] are at increased risk of ARF, progression of cardiac valvular lesions, and development of Definite RHD. It is therefore clear that at least some children with Borderline RHD have true RHD. We have also shown that children with Borderline RHD of the MV, rather than the AV, are at particularly high risk of progression of valve disease.
While ARF is rarely diagnosed in Australia, some
Conflicts of interest
None.
Acknowledgment
This study was supported by an Australian National Health and Medical Research Council project grant (Grant Application 1005951) and the NHMRC Centre for Research Excellence to Reduce Inequality in Heart Disease (Grant Application 1044897).
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This author takes responsibility for all aspects of the reliability and freedom from bias of the data presented and their discussed interpretation.