Table 6.6 Summary: Clinical evaluation of horses with myocardial disease Equine myocardial disease is poorly understood


History

Uncommon

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

sub-clinical

poor exercise tolerance

left- and/or right-sided congestive heart failure sudden death (rare?)

Usually associated with recent viral respiratory infection (myocarditis) May be a problem in a group of animals if associated with toxic origin

Clinical findings

Arrhythmias

Apex beat may be weak

Murmurs may or may not be present

Heart sounds quiet in some cases

Left- or right-sided congestive heart failure

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

murmurs present of grade 3-4/6 or greater

associated with abnormal arrhythmias, e.g. APCs, VPCs, AF

associated with signs of left- or right-sided congestive heart failure

Helpful diagnostic tests

Echocardiography (pre- and in some cases post-exercise)

Electrocardiography (resting, 24-hour, exercising)

? CPK MB fraction isoenzymes

?? LDH isoenzyme 2 fraction

Serial viral titres and haematological evaluation