Quantitative methods for evaluation of mitral regurgitation severity in canine degenerative mitral valve disease

Abstract

Introduction/objectives: Quantitative assessment of mitral regurgitation (MR) severity has become increasingly important as procedural therapies for MR reduction become available. This study aimed to obtain quantitative measures of MR severity across stages of degenerative mitral valve disease (DMVD) and evaluate agreement between two echocardiographic methods.

Animals, materials and methods: Fifty-one client-owned dogs were included across three DMVD stages (American College of Veterinary Internal Medicine B1, B2, and C). Regurgitant volume (RVol) and regurgitant fraction (RF) were measured on echocardiograms prospectively acquired by a single cardiologist using volumetric (using Simpson's method of discs) and proximal isovelocity surface area (PISA) methods. Results were compared across stages. Agreement between methods over the range of MR severity was determined by Bland-Altman analyses. Intra-observer and inter-observer measurement variability assessments were performed via intraclass correlation coefficients (ICCs).

Results: Median differences (25th percentile, 75th percentile) for volumetric and PISA-derived RVol and RF were as follows, respectively: B1: 0.19 mL/kg (-0.02 mL/kg, 0.25 mL/kg), 13.6% (-2.17%, 20.6%); B2: 1.49 mL/kg (1.09 mL/kg, 2.12 mL/kg), 55.6% (45.0%, 70.5%); C: 2.72 mL/kg (1.76 mL/kg, 3.13 mL/kg), 67.2% (61.8%, 78.5%); B1: 0.39 mL/kg (0.22 mL/kg, 0.69 mL/kg), 34.3% (19.0%, 56.1%); B2: 1.67 mL/kg (1.33 mL/kg, 2.15 mL/kg), 58.8% (49.8%, 73.9%); C: 3.1 mL/kg (1.91 mL/kg, 3.57 mL/kg), 75.2% (66.4%, 92.0%). All were different (P<0.0001) across stages. There was no proportional bias for RVol or RF (P=0.79, P=54). Intra-observer and inter-observer variability assessments showed ICC greater than 0.75 except PISA RF.

Conclusions: Measures of MR severity correlate with disease stage, although their accuracy remains unknown. Volumetric and PISA methods are not interchangeable.

Keywords: Echocardiography; Myxomatous mitral valve disease; Regurgitant fraction; Regurgitant volume; Simpson's method of discs.