I strongly advise you to take him to the cardiologist, even under sedation.
An ultrasound of the heart is the gold standard and would tell you exactly
what is wrong and waht treatment he needs. Some heart tablets like
vetmedin and fortekor come as beef flavour and are like treats, or can be given as
a beefy liquid which can be added to a drink of milk or tuna juice. The
cardiologist would take all this into consideration.
A grade 4 murmur is serious. If he is entering heart failure, it needs
treatment. Although there is no real evidence HCM can be improved, there are
many drugs that can stabilise it, my kitten was diagnosed at 3 months old and
has been taking drugs for nearly 7 years despite being given only a few
months to live.
Count his breathing as he is asleep. Find the normal pattern. Any increase
can suggest heart failure. Up tp 30 a minute is normal, 30+ concern and 40+
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