While both celebrities died from heart attacks, the specific circumstances of their deaths were different. John Ritter's heart attack was caused by a rare condition called a dissection of the aorta, which is a tear in the largest artery in the body. This condition is much less common than a standard heart attack and can be fatal.
Lucy Ball's death was attributed to a massive heart attack and there is no indication that she suffered from a dissection of the aorta.
So, while both individuals died from heart attacks, the specific causes and circumstances of their deaths were different.