MontyandZoom
Well-Known Member
From what I know vets categorised heart mumurs as "funtional" or "pathological". Functional means not to worry, whereas pathological means - worry!
The grading from 1 to 6 is concerned with the audibilty or loudness of the mumur when listened to with a stethoscope.
Functional mumurs are normally audible at 1-2 and I think pathological mumurs are then graded 3-6.
I'm pretty sure that exercise doesn't really have a bearing on severity as some functional mumurs are louder with exercise whereas some pathological mumurs are quieter with exercise or heart rate increase.
As long as there are no structural changes to the heart, ie, leaking, narrowing of arties, arrhythmia, disease or defects it shouldn't cause any problems as is therefore, functional.
The only way to know for sure about the type and severity of the mumur is to have an ECG but if the horse is a) not very expensive in the first place and b) is only required for hacking and dressage is might not be worth the expense.
QUOTE]
Not to be too picky......but grade of a heart murmur does not always determine prognosis. For example with VSD the smaller the defect (and less likely to cause a problem) the louder the murmur. So you could have a grade 5 murmur that causes no clinical signs or a grade 1 murmur that causes heart failure. Physiological murmurs are also very unlikely to get louder with exercise. An ECG will only tell you about an arrhythmia (such as AV block) but, unlike with small animals, tells you nothing about the type or severity of a murmur - this can only be done with an echocardiogram (ie an ultrasound).
Many practices have portable ultrasounds so if you were worried and very keen on the horse, you could always have it investigated?
Removing geek hat now........