There is an interesting term I came across called "Christmas Coronary". Emergency rooms report an increased number of cardiac cases on the day after Christmas. No one is sure why but there are a few opinions.
First and most obvious is that symptoms may be present but not addressed until after Christmas. Sometimes a patient may have atypical chest pain and attribute symptoms to indigestion. Over-indulgence in rich foods,salt, alcohol, and caffeinated beverages may also account for ER visits due to heart rhythm problems and congestive heart failure. Decrease activity and prolonged sitting in the car or at the table may also contribute.
At the risk of being called Scrooge, here are my recommendations. First, don't over eat to the point where you feel uncomfortable. Eat slowly. Avoid excessive sodium intake. "Calorie saving" where you starve yourself so you can eat more on Christmas is not a good idea. Take a baby aspirin (if not contraindicated) in the morning...especially if you are traveling. Go for a walk after your meal and avoid prolonged sitting. If you have a cardiac problem it's best to avoid caffeine and alcohol.
And finally, if you develop symptoms of seek medical attention. Waiting may make things worse.
Wishing you a Merry Christmas and Happy and Healthy New Year.