Atrial and ventricular mitral regurgitation in the general population
Authors: Keil L , Wenzel J P , Nikorowitsch J , Reichenspurner H , Blankenberg S , Girdauskas E 
Published: October 2024

Abstract

Background
Functional mitral valve regurgitation (FMR) is the result of two concurrent pathomechanisms: (1) the dilatation of mitral valve annulus (atrial) or (2) remodelling of the left ventricle (ventricular) in the absence of relevant leaflet degeneration¹. Even though FMR has been reported to be the most common cause of relevant MR², there is no general accepted definition of the two subtypes, nor are there population-based data regarding their prevalence, distribution and risk profiles¹.

Purpose
We aimed to evaluate the prevalence of FMR and to provide an in-depth characterisation of the subtypes aFMR and vFMR in the general population.

Methods
The study included the first 10,000 participants of the population-based Hamburg City Health Study enrolled between 2016 and 2019. Of these, 8.543 echocardiographic samples were available for analysis. Mitral valve was assessed by two independent investigators. Isolated degenerative MRs as determined by valve mobility (prolapse or restrictive) were excluded. FMR was classified as ventricular when fulfilling one of the following criteria: history of myocardial infarction or coronary artery disease, left ventricular ejection fraction (LVEF) ≤ 40%, restrictive leaflet, tenting area ≥ 150 mm² or coaptation depth ≥ 10 mm. All FMR with LVEF &gt; 55% were classified as atrial.

Results
After excluding the samples with an insufficient image quality or missing data and re-assessment by the second investigator, 216 of 282 participants with a relevant MR (i.e. moderate or severe) remained (2,6% of the total cohort, see figure 1). In the next step, 153 participants were classified as pure FMR (68.9%), the remaining were mainly functional with minor degenerative features.
A total of 31 (14.4%) MRs were classified as vFMR, the remaining 185 participants had an aFMR. Female gender was significantly more common in the aFMR cohort. The remaining demographic variables (age, body mass index) as well as established cardiovascular risk factors (i.e., diabetes, smoking, hypertension) were comparable between the vFMR and aFMR cohort. However, vFMR patients had significantly higher levels of NT-proBNP or NHYA state and presented more frequently with an atrial fibrillation (see figure 2). LVEF and LV stroke volume, TAPSE, left atrial ejection fraction and E/A ratio as a parameter of diastolic dysfunction were lower in the vFMR cohort whereas tenting area and left atrial endsystolic volume was significantly increased.

Conclusion
In our population-based study, aFMR was found to be the predominant subtype of FMR. The established cardiovascular risk factors were comparable in the vFMR and aFMR cohort. Echocardiographic variables differed significantly and indicate more advanced heart failure and LV remodelling in the vFMR cohort. Further categorization of FMR, in particular regarding the prognostic impact and long-term outcomes, is strongly warranted to allow a clinically relevant definition of aFMR and vFMR.Figure 1:Overview of sample sizeFigure 2:Baseline characteristics