Checking the extent of MVP is not really preventing or treating MVP, is it? The echo isn't preventing the mitral valve prolapse, it is also not an intervention - it is a diagnostic tool to guide further intervention. Yes, this could be considered a type of tertiary prevention - but hopefully it should also be clear how this is more usefully classified as diagnostic. Pretty much all medical care is to some extent preventive, even reducing the broken arm - so it becomes a meaningless word if it is loosely defined as any intervention that can potentially prevent sequelae. That means it’s ultimately going to be defined with some restrictive set of criteria. Is the US ACA definition very restrictive, yes, but that’s how it is.

Ejection fraction is not a disease, but let's call it heart failure. An echo evaluating for heart failure is a good example where we can use it as a diagnostic tool to prevent further progression - but again through other interventions - and if we're evaluating for abnormal ejection fraction we haven't prevented it.

Another example might be evaluating for a shunt to prevent stroke. However we don't routinely screen everyone for this.

Echo for inherited cardiomyopathies is a good example of primary or secondary prevention.

There are definitions within medicine that matter for defining appropriate use criteria, but all this preventive vs palliative is arguing loose semantics - the people you’re up against have already put in place the policy to avoid most of that.