one of the common themes in autopsy pathology is the reality that a cardiac lesion may encountered without there being pre-mortem signs/symptoms. the significance is often unclear and several possibilities exist.
do respond with your thoughts on this case.
the features point to a degenerate valve, without overt sepsis (but always worth doing Gram/PAS etc).
so, ….. if cause of death is clear then this is incidental, by definition.
but, it would be worth checking medical record for SOB/palpitation symptoms etc.
also worth flagging to family members if there is a history of early cardiac death/disease
simplest way to assess close relative swill be echocardiography initially, for reassurance.
A picture of the mitral valve would assist as macroscopic examination rather than histological examination may be by far the more reliable way of determining the nature of valve disease. If macroscopically the mitral valve looked like a proper floppy mitral valve I would agree with the comments above.