John Ritters family warns about the hiddenbut treatable heart condition that killed him on what would have been his 78th birthday

For generations, something troubling seemed to plague the men in John Ritter’s bloodline.“We always heard, ‘Oh those Ritters die of their first and last heart attack,’ ” Amy Yasbeck, the beloved comedian’s widow, told The Post.“[John’s dad] clutched his chest and fell over.

He was 60-something years old.”Country music star Tex Ritter’s sudden death was blamed on a cardiac emergency.Decades later, doctors made a similar assumption when his son showed up at a Burbank hospital sweating profusely, vomiting and complaining of chest pain in September 2003.

But John wasn’t having a heart attack — and his family now suspects his father didn’t either.In reality, the “Three’s Company” star was suffering from an aortic dissection, a medical emergency involving the body’s largest artery that doctors initially failed to recognize before it claimed his life at 54.“The sad truth of the matter is that because it’s so much more common for it to be a heart thing, John was treated for a heart attack before they had done any imaging, and that exacerbated it,” Amy, 64, said.“This happens way too often.”Now, on what would have been John’s 78th birthday, his loved ones are sounding the alarm about aortic disease — and urging people to know their family history before tragedy strikes.“We’re just ringing the alarm,” said Tyler Ritter, John’s second son and third child with ex-wife Nancy Morgan.

“If we can catch it ahead of time, we can prevent it.”An aortic dissection occurs when the wall of the aorta, the body’s main artery, tears.Blood can then force its way between the artery’s layers, potentially cutting off blood flow to vital organs including the brain, kidneys and heart, according to UChicago Medicine.

“Time is of the freaking essence when this happens,” Amy said.“Fifty percent of people don’t even make it to the hospital.”In July, Sen.

Lindsey Graham died unexpectedly at 71 after an aortic dissection.Dep...