Evaluation of Left Ventricular Papillary Muscles Using Targeted Views by Echocardiography

Background: Papillary muscles (PMs) are important for mitral valve competence and left ventricular mechanics, but accurate evaluation is often limited by poor visualization in conventional echocardiographic views. We developed papillary muscle-targeted (PM-targeted) echocardiographic views to improve PM visualization and aimed to validate this approach and establish normative reference values in healthy adults. Methods: In protocol 1, posteromedial papillary muscle (PPM) length and maximum diameter measured using PM-targeted and standard views were compared with anatomic measurements in ten ex vivo porcine hearts. In protocol 2, measurements of the anterolateral papillary muscle (APM) and PPM were compared between PM-targeted and standard views in 100 healthy adults. In protocol 3, PM structural, spatial, and functional parameters were measured using PM-targeted views in 245 healthy adults. In protocol 4, PM measurements obtained from 2D PM-targeted views were compared with 3D echocardiographic measurements in 50 patients with ventricular functional mitral regurgitation (VFMR); PM parameters in VFMR were also compared with those in healthy adults. Results: In protocol 1, PM-targeted views showed stronger correlation with anatomic measurements for PPM length than standard views (0.966 vs. 0.752, p = 0.049), while standard views underestimated PPM length. In protocol 2, PM-targeted views enabled complete visualization of APM and PPM and yielded longer PM lengths and smaller maximum diameters than standard views. In protocol 3, males had larger PM maximum diameters and longer tip-to-annulus distances than females (all p < 0.05). With aging, interpapillary distance reduction (ΔIPMD), IPMD fractional shortening (IPMD-FS), and APM length decreased, whereas end-systolic IPMD increased (all p < 0.05). PM parameters correlated positively with body surface area (all p < 0.05). In protocol 4, PM measurements obtained from 2D PM-targeted views showed no differences from 3D echocardiographic measurements and demonstrated good correlation and agreement across assessed PM parameters against 3D echocardiographic measurement as a standard reference. Compared with healthy adults, patients with VFMR showed altered PM geometry/remodeling patterns. Conclusions: PM-targeted echocardiographic views improve visualization and measurement of papillary muscles and provide normative reference values, facilitating more accurate evaluation of PM-related abnormalities in clinical practice.