> There are two categories of healthcare right? Palliative and preventative.
The simple answer to this is that “preventative” in the case of billed medical services has a specific and clearly defined meaning - it does not even mean all services that ever would be considered preventative. This definition will be found in your insurance paperwork and corresponds at least to the site I posted - so a further philosophical discussion is irrelevant.
To your actual question - No, the echo is usually pallative. However, right off the bat I'll say this is an overly reductionist and not terribly useful schema for classifying the delivery of medical care. While it might be good as a way for the general public to think about prevention, it’s way too oversimplistic to be useful beyond that.
An aside, palliative has a specific and different meaning within medicine: roughly, treating symptoms without a goal of cure. Reducing a broken arm or removing an inflamed appendix is not palliative care in that sense.
But even if we widen the scope of palliative to be treatment an echo would be neither. An echo is diagnostic - it doesn’t prevent nor treat heart failure or disease. Often when an echo is ordered it leads to some form of treatment for some found disease, in which case if we’re going to stick to the simple classification would be “palliative” - we’re using it to guide treatment, we can’t prevent something that we already see.
> If he had violent symptoms it would clearly be palliative
It's just not that simple. Echos are sometimes used to further evaluate or manage asymptomatic disease, for instance A-fib or a concerning murmur. We're using the echo to rule out suspected coexisting conditions, that's not prevention, and it's not treatment either at that point.
Also, echos usually have some symptomatic indication - and they don't have to be violent, whatever that means.
> it can only be preventative
Can you actually think of a disease that an echo would be used to prevent?
But again, in practice we don’t think of delivery of medical care in such grossly general terms - it’s doesn’t simplify in a useful way.