Abstract 2244: Real-Time 3D Echocardiographic Evaluation of the Spatial Position of Left Ventricular Papillary Muscles
Background. It has been recently recognized that mitral regurgitation (MR) in patients with dilated and ischemic cardiomyopathy is caused not only by mitral annulus (MA) dilatation, but also by the displacement of the papillary muscles (Paps) secondary to LV remodeling. Our aim was to characterize the position of Paps in 3D space using real-time 3D echocardiography (RT3DE) in patients with moderate MR.
Methods. Transthoracic RT3DE imaging was performed on 45 subjects including 15 normal (NL) subjects and 30 patient with moderate MR (effective regurgitant orifice area EROA≥0.2 cm2) secondary to dilated (DCM; N=15) or ischemic (ISC; N=15) cardiomyopathy. Custom software was used analyze RT3DE datasets. First, mitral annulus center, LV apex, Paps tips and Paps bases were manually selected at the end-diastolic frame. Then, the position of each papillary muscle was described by computing:
tethering length (from tip to mitral annulus center);
angle between LV long axis and the line connecting the tip and the mitral annulus center (theta);
thickness at the base (at the insertion of the LV wall, as well as the tip-to-tip inter-papillary distance.
Results. EROA was similar in both groups of patients: DCM: 0.34±0.13 cm2, ISC: 0.38±0.08 cm2. The basal thickness of both Paps was significantly larger in both MR groups compared to NL subjects (antero-lateral: NL 7±5 mm, DCM 17±11* mm, ISC 13±5* mm; postero-medial: NL 10±5 mm, DCM 17±8* mm, ISC 17±5* mm; *p<0.05 vs NL by Kruskal-Wallis test). The theta angles, the inter-papillary distance and the tethering lengths were significantly increased in DCM patients compared to NL subjects. In contrast to NL subjects and patients with DCM, patients with ISC had more asymmetric theta angles and unequal tethering lengths (angle difference: 13.7±5.1°, length difference: 12.7±6.1%), both statistically significant.
Conclusions. This new methodology allows the quantitative evaluation of Paps positions in 3D space. Using this methodology allowed us to demonstrate significant inter-group differences in Paps measurements despite similar degrees of MR. These results provide additional insight into the pathophysiology of MR and have implication for surgical planning.