James Gandolfini: How a heart attack can lead to sudden death

James Gandolfini's autopsy reportedly reveals the 51-year-old died of a heart attack while on vacation in Italy. Nothing else was suspected in causing the death, according to a family friend.

"There's nothing out of the ordinary. It was a heart attack. It was a natural cause," friend Michael Kobold told reporters Friday. "There was no foul play, no substance abuse. None of that."

Yesterday, hospital officials in Rome had said the star of "The Sopranos" died of cardiac arrest. Previously, Italian news agency AGI reported the actor suffered a heart attack in his hotel room in Rome.

A heart attack, or myocardial infarction, is caused by a blockage in an artery that disrupts the supply of oxygen-rich blood that goes to the heart.

CBS Evening News chief medical correspondent Dr. Jon LaPook explained to CBSNews.com (video above) that once blood flow to the heart is stopped by this blockage, that affected portion of the heart actually dies. That in itself may not end a person's life, he pointed out, and the victim could still have a normal heartbeat if the electrical connection that controls the beat remains intact. But, the attack could lead to cardiac arrest if there's so much irritation within the heart, that its normal electrical system starts getting all "goofed up," he said.

Instead of a normal heartbeat, "The heart beats like a 'bag of worms' ineffectively," LaPook explained. "You don't get enough blood flow to the brain and the person passes out." That's when a heart attack could lead to cardiac arrest.

Risk factors for a heart attack include family history, high blood pressure and cholesterol, smoking, obesity and age.

"Fifty-one is a tragically young age to have a heart attack and die, but it's actually very common for people in America to have clogging of the arteries at that age," according to LaPook.

For people looking to reduce their risk of heart attack and sudden death, the doctor says it's essential to eat right, exercise, maintain a healthy weight and never smoke. It's also important to know your numbers -- blood pressure and cholesterol -- and work with your doctor to get them in the right range, LaPook added. While you can't change your family history, taking these steps could dramatically reduce the risk for heart attack and sudden death from cardiac arrest.

"You have to be proactive about your health - you cannot take it for granted," said LaPook. "You certainly can control what goes on in your life that you have now, and lower the risk that you're going to have a terrible outcome like unfortunately James Gandolfini had."