Abstract
Introduction
Anterior mitral valve leaflet (AMVL) restriction is a prominent morphological feature of rheumatic heart disease (RHD). The World Heart Federation (WHF) criteria for echocardiographic diagnosis of RHD rely on the use of colloquial terms such as “dog-leg” to define AMVL restriction rather than a strict, reproducible definition. We recognise AMVL restriction when the tip of the leaflet is seen to point away from the interventricular septum and towards the posterior left ventricular (LV) wall at peak diastole in the parasternal long axis (PSLAX) view. This definition however risks inclusion of a finding commonly identified in our high-risk screening program (Echo in Africa- EIA) which demonstrates gradual AMVL bowing (so-called “slow-bow”) from the proximal to mid-leaflet but with free motion ('fluttering') of the tip during diastole. This is in contrast to RHD-related restriction which typically involves the distal AMVL tip only. We propose that the former is a normal variant of the AMVL and is unrelated to the RHD process, provided no concomitant morphological features of RHD are identified.
Purpose
Determine the prevalence of “slow-bow” AMVL restriction between two cohorts of schoolchildren with a documented high-and low-RHD prevalence.
Methods
Retrospective analysis of EIA data obtained from children (aged 13–18) attending two separate South African schools. The high-RHD prevalence school (HR) demonstrated a 0.8% rate of WHF “definite RHD”. The low-RHD prevalence school (LR) demonstrated no cases of WHF “definite RHD”. Cases of AMVL restriction were identified and classified according to the definitions provided above.
Results
A total of 941 screening studies (HR cohort n=577 /LR cohort n=364) were evaluated. 74 cases of AMVL restriction (12.82%, 95%, CI 10.34–15.80) were identified in the HR cohort of which 8 cases demonstrated AMVL-tip restriction (1.39%, 95%, CI 0.70–2.71) and 65 cases demonstrated “slow bow” (11.27%, 95%, CI 8.94–14.11). There were no cases of AMVL-tip restriction observed in the LR-cohort and 35 cases of “slow-bow”(9.62%, 95%, CI 7–13.08).
A. “Slow bow”; B. “Distal tip restriction”.
Conclusion
Our results support the hypothesis that “slow-bow” AMVL restriction is a common variant of the AMVL amongst South African school children and unrelated to the RHD process. Further research is required to investigate the exact mechanism underlying this form of AMVL restriction.
Acknowledgement/Funding
Edwards Lifescience EHM grant
Screening for subclinical rheumatic heart disease: Addressing borderline disease in a real-world setting
