Mitral stenosis in dogs

Epidemiology of heart disease in English Bull Terriers and echocardiographic characteristics of mitral valve abnormalities

OBJECTIVES

To present the prevalence and distribution of heart disease as well as echocardiographic findings in English Bull Terriers.

MATERIALS AND METHODS

One hundred and one English Bull Terriers were retrospectively included to evaluate the prevalence and distribution of heart disease. Secondly, a retrospective study on mitral valve abnormalities was performed on three groups: a control group (n=120, 19 breeds) used to establish reference intervals for mean transmitral gradient; a healthy English Bull Terriers group (n=25) and an English Bull Terriers group with mitral valve abnormalities (n= 18). Healthy English Bull Terriers for which mitral inflow parameters were not obtainable and English Bull Terriers with other types of heart disease were excluded.

RESULTS

The prevalence of heart disease in English Bull Terriers was 65% (66/101), with mitral valve abnormalities (47%, 47/101) and aortic stenosis (29%, 29/101) being most common. The cut-off value for normal mean transmitral gradient was 3.5 mmHg in the control group. The mean transmitral gradient for healthy English Bull Terriers was higher than for other dog breeds. Healthy English Bull Terriers had a smaller mitral valve area and mitral annulus diameter compared with dogs with a similar body surface area. A high heart rate, smaller mitral valve area, mitral regurgitation, and volume overload are associated with increased mean transmitral gradient in English Bull Terriers with mitral valve abnormalities.

CLINICAL SIGNIFICANCE

We suggest that mitral valve area, mitral annulus diameter and mean transmitral gradient measurements should be included in the echocardiographic protocol for English Bull Terriers.

Transthoracic two-dimensional and three-dimensional echocardiography for the measurement of mitral valve area planimetry in English Bull Terriers with and without heart disease

INTRODUCTION

Mitral valve area (MVA) planimetry is used to diagnose and classify mitral stenosis (MS) in humans using two-dimensional and three-dimensional echocardiography (MVA_2D and MVA_3D). This study aimed to evaluate agreement, feasibility, and observer variability between MVA_2D and MVA_3D in English Bull Terriers (BT). Our hypotheses were (1) that the MVA of BT is generally smaller than that of breeds with similar body weight and (2) that these techniques could be used to diagnose MS in BTs.

ANIMALS

Twenty healthy BTs, 15 healthy Boxers, and 49 BTs with heart disease.

MATERIALS AND METHODS

A prospective diagnostic agreement study was conducted. All dogs underwent a thorough clinical examination, conventional transthoracic echocardiography, and three-dimensional echocardiography.

RESULTS

Bland-Altman plots (limits of agreement: 0.12-1.5) showed consistent bias and poor agreement between MVA_2D and MVA_3D. For the 69 BTs, MVA_3D (2.1 ± 0.50 cm²) measurements were significantly lower than MVA_2D measurements (2.9 ± 0.60 cm²), and healthy BTs had significantly lower MVA parameters than healthy Boxers (p < 0.001). Intraobserver and interobserver variability were excellent for both MVA_2D and MVA_3D (intraclass correlation coefficient >0.9). Six BTs were diagnosed with MS, with MVA_3D less than 1.8 cm² and a mean transmitral gradient (MTG) of more than 5 mmHg.

CONCLUSIONS

Both MVA_2D and MVA_3D are feasible, have low observer variability and can be used to diagnose MS in BTs. For assessing the narrowest orifice area, the preferred method is MVA_3D. The smaller MVA in BTs compared to Boxers may indicate some degree of MS.