It sounds like a syncopal episode (i.e. fainting spell) and in boxers it usually signals a problem with the heart. If the heart is not pumping blood to the extremeties and brain, the dog collapses. Usually this is caused by a series of premature contractions in the right ventricle, which disrupts the normal heart rhythm. The condition is called arrhythmogenic right ventricular cardiomyopathy (ARVC) or boxer cardiomyopathy. It is very serious and life threatening (some dogs never survive their first collapse) but can be treated with varying success with arrhythmic drugs. If you search the boards for these conditions you will find many threads dealing with this topic.
Did you notice whether his gums or tongue were pale?
I would suggest you make an immediate appointment to see your vet. You will likely have to see a cardiologist for further testing. It is not enough for a vet to run a short ekg or just listen to the heart. The abnormal beats can be too erratic. The normal testing protocol is an ultrasound of the heart (echocardiogram) and Holter monitor (24-hour portable ekg).
My 8 year old collapsed a little more than 3 months ago and was diagnosed with this condition. He hasn't had any episodes since the original collapse and is on a twice daily medication called Sota
.
I know this sounds frightening, it is. But it is imperative that you understand what you may be dealing with and get your boy the medical attention he needs. I wish you all the best.
-Karlyn
