What is the clinical evidence from this study?

Study design: Observational. Population: Chronic mitral valve insufficiency (CMVI) (n=105). Intervention: Chronic mitral valve insufficiency vs. Normal dogs without heart disease. Primary outcome: End-systolic volume index (ESVI) in large breed dogs (p=<0.001).

January 1, 2007Open Access

Decreased Systolic Function and Inadequate Hypertrophy in Large and Small Breed Dogs with Chronic Mitral Valve Insufficiency

Q: What are the key findings of this study?

Chronic mitral valve insufficiency in both small and large breed dogs was associated with systolic dysfunction, evidenced by significantly increased end-systolic volume index and inadequate left ventricular hypertrophy.

Key Result

Chronic mitral valve insufficiency in both small and large breed dogs was associated with systolic dysfunction, evidenced by significantly increased end-systolic volume index and inadequate left ventricular hypertrophy.

Study Design

Type

Observational (n=105)

Multicenter

PICO

Population

105 dogs (56 with chronic mitral valve insufficiency and moderate heart failure, and 49 normal controls) were evaluated to assess echocardiographic indices of systolic function and left ventricular hypertrophy.

Exposure / Comparator

Chronic mitral valve insufficiency vs Normal dogs without heart disease

Primary Outcome

End-systolic volume index (ESVI) in large breed dogs, p=<0.001

Main Result

Absolute Event Rate: 83.22% vs 36.43%

p-value: p=<0.001

Limitations

Inability to exclude with certainty concurrent diseases of either a systemic or a cardiac nature that could have affected systolic dysfunction.
ESVI represents a global index of ventricular function and does not represent contractility at a cellular level.
Systolic function can be affected by age, and affected dogs were significantly older than the normal dogs.
Retrospective selection of affected dogs with variable duration of heart failure signs.
Ongoing therapy with ACE inhibitors and furosemide could have influenced loading conditions and echocardiographic measurements.

Abstract

BACKGROUND: Systolic dysfunction associated with chronic mitral valve insufficiency (CMVI) has been demonstrated in experimental animal models and large breed (LB) dogs but has been reported as an uncommon finding in small breed (SB) dogs with naturally occurring disease. It has been suggested the myocardial failure could be, in part, because of an insufficient increase in left ventricular mass. HYPOTHESIS: To test if SB and LB dogs with CMVI and moderate heart failure have systolic dysfunction and if they have adequate eccentric hypertrophy. ANIMALS: Data from 38 SB and 18 LB dogs affected with CMVI were compared retrospectively with results from 2 groups of normal dogs (17 SB and 32 LB). METHODS: Systolic function was investigated echocardiographically by using percentage fractional shortening (FS), the ratio between observed and expected end-systolic diameter (ESD/ESDe), and end-systolic volume index (ESVI). Left ventricular hypertrophy was estimated by using the ratio between the thickness of the left ventricular free wall and the radius in diastole (h/R). RESULTS: Both affected SB and LB dogs had a significantly increased FS and ESVI (FS% SB 45.6 + 8.04 versus 40.06 + 8.9, P < .05; FS% LB 33.64 + 8.61 versus 27.3 + 7.3 P < .05; ESVI SB 30.0 +/- 2.3 mL/m2 versus 21.18 +/- 13.9 mL/m2, P < .05; ESVI LB 83.22 +/- 43.84 mL/m2 versus 36.43 +/- 13.30 mL/m2 versus P < .001). The h/R in affected animals was decreased (0.53 +/- 0.11 versus 0.41 +/- 0.12, P < .05 SB; 0.47 +/- 0.11 versus 0.38 +/- 0.09, P < .05, LB). CONCLUSIONS AND CLINICAL IMPORTANCE: Data from this study indicate that dogs with moderate heart failure caused by CMVI have systolic dysfunction. Inadequate hypertrophy of the left ventricle may be, in part, responsible for this finding.

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