Table 6.2 Summary: Clinical evaluation of horses with mitral regurgitation

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History

Variable signs noted by owners depending on the severity of the condition:

incidental finding

poor exercise tolerance (stopping, fading, prolonged recovery, EIPH) left- and/or right-s~ed congestive heart failure

Sudden onset or progressive over days to years

Clinical findings

Mucous membrane colour usually normal

CRT normal to slow

Arterial pulse normal to weak

Pulse rate normal (24-45) to rapid (>45), regular or irregular

Grade 2~/6 plateau-type pan or holosystolic murmur with a PMI over the left apical area or lust dorsal to this

Murmur may radiate dorsally and cranially or caudally

Murmur may radiate to right side of the chest

Late systolic murmurs may also be heard, suggestive of valve prolapse

Endocarditis seldom affects this valve in adults

Evaluation of significance

Most likely to be significant if:

associated with poor athletic performance slow CRT

weak or variable pulse quality resting heart rate >45bpm

intensity grade 4/6 or greater widespread radiation

associated with abnormal arrhythmia, especially atrial fibrillation, APCs

associated with signs of left-sided congestive heart failure (pulmonary oedema evident by white froth at nares, tachypnoea, weakness, exercise intolerance)

associated with signs of right-sided congestive heart failure (dependent oedema, jugular filling)

Note: The progression of MR is seldom predictable, so detection of MR may be a significant finding, for future athletic use, even if no clinical signs are attributed to the condition at the time of examination.

Helpful diagnostic tests

Echocardiography

Electrocardiography, if arrhythmia present