Does Preliminary Chest Shape Assessment Improve the Prognostic Risk Stratification of Symptomatic Individuals with Primary Mitral Regurgitation? A Narrative Review of Traditional and Innovative Prognostic Indicators

Primary mitral regurgitation (PMR) is the most common mitral valve disorder in clinical practice. Although several prognostic indicators derived from resting transthoracic echocardiography (TTE) and exercise stress echocardiography (ESE) are available, patient outcomes remain highly variable, with substantial differences in complication rates and mortality. Identifying individuals at lower cardiovascular risk is therefore clinically relevant, as they represent a large proportion of cases. Current guidelines recommend an integrative approach—combining qualitative, semi-quantitative, and quantitative indices—to determine the timing of intervention, but they do not specifically address risk stratification in low-risk PMR populations. Recent studies have highlighted the potential prognostic value of chest wall configuration, assessed noninvasively using the Modified Haller Index (MHI). Defined as the ratio of latero-lateral thoracic diameter to the antero-posterior (A-P) sternum–spine distance, MHI appears to influence myocardial deformation indices obtained by speckle-tracking echocardiography (STE). Patients with PMR due to mitral valve prolapse (MVP) often show a reduced A-P thoracic diameter caused by sternal depression. Among these, those with an MHI > 2.5 or A-P diameter ≤ 13.5 cm display greater impairment in global and basal strain, particularly in longitudinal and circumferential directions. These abnormalities likely reflect extrinsic geometric constraints and cardiac displacement leading to apparent dyssynchrony rather than intrinsic myocardial dysfunction. A reduced A-P diameter was also independently associated with mitral annular disjunction (MAD) in MVP and emerged as a determinant of impaired strain in this subgroup. In a retrospective cohort of 424 symptomatic MVP patients with moderate MR undergoing ESE, positive tests and exercise-induced severe MR were uncommon. Importantly, an MHI > 2.5 or an A-P diameter ≤ 13.5 cm was associated with a favorable medium-term prognosis, with few adverse cardiovascular events. This narrative, non-systematic review, based on a structured but non-PRISMA literature search, summarizes current evidence on conventional and novel echocardiographic prognostic markers and their implications for risk stratification in PMR. As such, it carries inherent limitations, including potential selection bias, incomplete retrieval of unpublished or negative studies, and reliance on single-center observational data. The findings should therefore be interpreted cautiously and validated through larger, independent, multicenter investigations.