What killed Carrie Fisher; George Michael?

FILE - In this Sunday, Jan. 25, 2015 file photo, Carrie Fisher presents the life achievement award on stage at the 21st annual Screen Actors Guild Awards at the Shrine Auditorium in Los Angeles. Fisher has reportedly been transported to a hospital after suffering a severe medical emergency on a flight Friday, Dec. 23, 2016. (Photo by Vince Bucci/Invision/AP, File)

FILE - In this Sunday, Jan. 25, 2015 file photo, Carrie Fisher presents the life achievement award on stage at the 21st annual Screen Actors Guild Awards at the Shrine Auditorium in Los Angeles. Fisher has reportedly been transported to a hospital after suffering a severe medical emergency on a flight Friday, Dec. 23, 2016. (Photo by Vince Bucci/Invision/AP, File)

Actress Carrie Fisher died Tuesday morning at age 60 after suffering a heart attack days earlier aboard a flight bound for Los Angeles, a family representative said. Singer George Michael died at age 53 on Christmas Day when, according to his manager, his heart "failed" him while lying peacefully in bed.

Fisher is reported to have suffered a massive heart attack while on the flight between London and Los Angeles last Friday. According to witnesses, Fisher lost consciousness about 15 minutes before the flight landed. She was given emergency treatment and taken to the hospital, where she never regained consciousness and remained on a ventilator until she died on Tuesday.

While there is not a “safe” time of the year when it comes to heart-related issues, the holidays can be a more deadly time for some. Studies have shown that a combination of excessive food, stress and alcohol can lead to an increase in heart-related deaths between Christmas and New Year’s Day. People have a 5 percent greater chance of suffering a heart-related issue – a heart attack or sudden cardiac death – at this time of year.

Here is a quick look at the difference between a heart attack, sudden cardiac death and heart failure.

What is a heart attack?'

What is called a heart attack is an incident where blood flow to a portion of the heart is blocked. This can happen for a number of reasons. Often, it is the result of a blood clot. In other cases, it’s because of a build-up of fat and cholesterol (called plaque) that sticks to the inside the artery walls and slows blood flow. Plaque can break loose, form a clot and block the flow of blood to the heart, leading to a heart attack. Doctors call heart attacks myocardial infarction.

What happens to the heart when a heart attack occurs?

The heart is a muscle. When the blood flow to the heart (or any muscle in the body) is hampered, the cells that make up the muscle begin to die. The longer the blockage of blood flow, the more the damage. The more damage, the more likely the person won’t survive the attack. When muscle dies because of lack of blood flow, it cannot be repaired.

What Is a massive heart attack?

Fisher is said to have had a “massive” heart attack. What that means is that a large portion of the heart muscle was damaged. This is most likely to happen when there is a blockage of a coronary artery that supplies blood to a large portion of the heart.

A massive heart attack will do a lot of damage to the muscle and can result in collapse, cardiac arrest (when the heart stops beating), permanent heart damage or death.

How are heart attack symptoms different in women than in men?

Men and women often have different symptoms of a heart attack.

Here are the most commonly reported symptoms from women who have had heart attacks:

• Chest pain or discomfort

• Pain in arm(s), back, neck, or jaw

• Stomach pain

• Shortness of breath, nausea, or lightheadedness

• Sweating

• Fatigue

Here are the most commonly reported symptoms from men:

• Chest discomfort.

• Discomfort in other areas of the upper body

• Shortness of breath

• Breaking out in a cold sweat, nausea or lightheadedness.

What is sudden cardiac arrest?

Sudden cardiac death is an electrical issue in the body. A sudden cardiac arrest usually results from an electrical disturbance in the heart. It's not the same thing as a heart attack, which is a blockage of the blood flow to the heart.

What happens when someone suffers a sudden cardiac arrest?

The electrical problem in the heart causes the heart’s natural rhythm to be interrupted. The rhythm become rapid and irregular, causing the heart to become less effective in pumping blood throughout the body. When that happens, the heart cannot deliver blood to the rest of the body or receive it back in. The heart muscle begins to die, the brain is starved for blood, and the person will collapse. The chances of dying are extremely high unless help is begun immediately.

What are the symptoms of sudden cardiac arrest?

In more than half the cases of sudden cardiac arrest, there are no symptoms of trouble. Other people said they felt their heart “racing” and felt dizzy or nauseated.

What causes sudden cardiac arrest?

Arrhythmias – or irregular heartbeats – is the most common cause of sudden cardiac arrest. The most deadly and a most common arrhythmia is ventricular fibrillation. That means the ventricles are not working in a controlled rhythm. The ventricles are the lower chambers of the heart. There are four chambers in the heart. The upper chambers are called atriums.

George Michael is said to have died from heart failure, something different than a heart attack.

What is heart failure?

Heart failure means the heart cannot effectively pump blood through the arteries and veins to all the other parts of the body. Heart failure is a condition that happens over time.

What happens when you suffer from heart failure?

For some reason, the heart has difficulty pumping blood around the body, and that difficulty causes the muscle’s ability to contract and fill properly. When the heart fails to empty properly before it fills instantly again with blood, then blood does not get to some parts of the body. This causes fatigue. People need oxygen to carry blood to keep body parts up and going, and it causes blood to back up into the heart, which sends a signal that the body needs to hang onto fluids. Thus, the body begins to retain water and a person begins to swell. The walls of the heart stretch and stiffen while trying to pump more blood. The heart gets weaker over time.

What causes it?

Heart failure can be caused by coronary artery disease, a heart attack, cardiomyopathy or damage to the heart caused by blood flow problems or excessive alcohol and drug abuse. Genetic conditions can also contribute to the condition. Other conditions, such as high blood pressure, heart valve disease, thyroid disease, kidney disease, diabetes, or heart defects, can also lead to heart failure.

What to do if someone suspects a heart issue?

Call 911. If someone has chest pain, do not wait to call for help. Do not be worried it’s “just indigestion." Do not think it will go away if they sit down for a while. All those things could be true, and they will be just fine, but they could also be having a problem with their heart.

Nearly 750,000 people in America suffered a heart attack last year. In the United States, someone has a heart attack every 34 seconds. Every minute of every day, someone in the United States dies from a heart disease-related event.

It is the leading cause of death in the United States and is more deadly than all forms of cancer combined.

Almost two-thirds of women who die suddenly from heart disease had no previous symptoms, according to the Centers for Disease Control and Prevention.

What to monitor to help the chances of avoiding heart trouble?

Four things: Blood pressure, blood sugar, cholesterol and triglycerides.

Sources: WebMD; The Heart Foundation; Health Grades; Cleveland Clinic