Topography of the Papillary Muscles in the Mitral Valve Complex and Their Relevance for Mitral Valve Function.

Abstract

Background: The mitral valve apparatus is a complex system that requires sufficient function of all involved structures. Previous studies have demonstrated that ventricular remodeling can cause displacement of subannular structures, including the papillary muscles, which in turn promotes the development of mitral regurgitation. Furthermore, in such cases, annuloplasty alone is often insufficient to restore optimal valve function. Instead, additional reconstruction of the subannular apparatus is associated with improved clinical outcomes. Our study aimed to analyze the topography of the papillary muscles in the mitral valve complex and their relevance for mitral valve function. Methods: In 148 patients who underwent both cardiac computed tomography (CT) and echocardiography, the position of the papillary muscles within the left ventricle was assessed. CT scans were evaluated in end-diastolic four-chamber view, two-chamber view, and short-axis view. CT analysis involved determining the position of the papillary muscles based on a modified left ventricular segmentation scheme, which subdivided the original segments into "a" and "b" subsegments in a counterclockwise manner. Furthermore, the midventricular diameter, ventricular length, as well as the angle between the papillary muscle (PM) and the left ventricular wall, were measured. Comorbidities were assessed. The presence of mitral regurgitation (MR) and ejection fraction was determined based on echocardiographic data. Echocardiography was conducted either as part of initial cardiological assessments or during follow-up examinations. For detailed statistical analysis, the patients were divided into the following groups: control group, MR-only group, coronary heart disease (CHD)-only group, and combined CHD and MR subgroup. Results: Mitral regurgitation was significantly correlated with age (p < 0.001) and hypertension (r = 0.1900, p = 0.0208), and in the MR-only subgroup, additionally with atrial fibrillation (r = 0.2426, p = 0.0462). The length (p < 0.001) and internal diameter (p < 0.001) of the left ventricle were significantly larger in men than in women. Different positions of the papillary muscles were identified. Segment 7a was significantly correlated with MR in the combined CHD and MR subgroup. In normal-sized ventricles, patients with MR and papillary muscle in 12a (p = 0.0095) or 10a (p = 0.0460) showed a significantly larger angle than patients without MR (overall dataset). Conclusions: Assessment of papillary muscle position is essential in diagnosing mitral regurgitation and should guide the consideration of subannular repair during surgical treatment.