Efficacy of a mitral regurgitation severity index to predict long‐term outcome in dogs with myxomatous mitral valve disease

Abstract

BackgroundPredicting progression of myxomatous mitral valve disease (MMVD) in dogs can be challenging.Hypothesis/ObjectivesThe mitral regurgitation severity index (MRSI) will predict time to congestive heart failure (CHF) and all‐cause death in dogs with MMVD.AnimalsEight hundred sixty‐nine client‐owned dogs.MethodsRetrospective study pooling data from 4 previous samples including dogs with MMVD stage B2 or C. MRSI was calculated as: (heart rate [HR]/120) × left atrium‐to‐aorta ratio (LA:Ao) × (age in years/10) × 100. Alternative MRSI formulas substituting radiographic measures of left atrial size were also calculated. Cox proportional hazard modeling and time‐dependent receiver‐operator characteristic curves quantified prognostic performance.ResultsFor Stage B2 pooled samples, MRSI > 156 was predictive of time to CHF (median 407 vs 1404 days; area under the curve [AUC] 0.68; hazard ratio 3.02 [95% CI 1.9‐4.9]; P < .001). MRSI > 173 was predictive of all‐cause death (median survival 868 vs 1843 days; AUC 0.64; hazard ratio 4.26 [95% CI 2.4‐7.5]; P < .001). MRSI showed superior predictive value compared to the individual variables of HR, LA:Ao, and age. Variations of the MRSI equation substituting radiographic vertebral left atrial size for LA:Ao were also significantly predictive of outcome in stage B2. MRSI was not consistently predictive of outcome in Stage C.Conclusions and Clinical ImportanceMRSI was predictive of outcome (onset of CHF and all‐cause death) in MMVD Stage B2, demonstrating utility as a useful prognostic tool. Echocardiographic LA:Ao can be effectively replaced by radiographically determined LA size in the MRSI formula.

Radiographic Left Atrial Size Measurement of Dogs in Different Mitral Valve Disease Stages with Four Different Methods

“…Different investigators have studied how to quantify the size of the left atrium radiographically; indirectly: the crossing lines method [11] and the bronchus to spine and radiographic left atrial dimension (RLAD) to spine methods [12], and objectively: RLAD [13], the vertebral left atrial size (VLAS) [6], the left atrial width [14], the modified-vertebral left atrial size (M-VLAS) [15], and the modified vertebral left atrial size (mVLAS) [16]. Several studies have been carried out to assess the clinical utility of those different methods of detecting left atrial enlargement in dogs with cardiac disease, such as A clinical utility of a single method to identify cardiac chamber remodeling diagnosed on echocardiography [6,7,13,15] compared to other methods [15,[17][18][19], proposing different cutoff values and aiding the practitioner in the diagnosis of congestive heart failure in dogs with different cardiovascular diseases [8,20,21]. Other authors have studied the existence of breed variability for the VLAS [22][23][24][25][26], M-VLAS [24], and RLAD [22,24] methods, reporting breed-specific reference values.…”