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Medical Mondays: ReEnergize Your Heart for the New Year -- Monday, January 7, 2012 -- Dr. Drew Pickett

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Drew Pickett, MD: electrophysiologist (cardiologist)
TOPIC: ReEnergize Your Heart for the New Year
Monday, January 7, 2013

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DID YOU KNOW…16 million: The estimated number of Americans who will have atrial fibrillation (AF) in 2050, up from 6 million today


Atrial Fibrillation and Heart Disease

What Is a Normal Heart Rhythm?

The heart has four chambers, or areas. During each heartbeat, the two uppers chambers (atria) contract, followed by the two lower chambers (ventricles). This action is directed by the heart's electrical system.

The electrical impulse begins in an area called the sinus node, located in the upper part of the right atrium. When the sinus node fires, an impulse of electrical activity spreads through the right and left atria, causing them to contract, forcing blood into the ventricles.

Then the electrical impulses travel in an orderly manner to another area called the atrioventricular (AV) node and HIS-Purkinje network. The AV node is the electrical bridge that allows the impulse to go from the atria to the ventricles. The HIS-Purkinje network carries the impulses throughout the ventricles. The impulse then travels through the walls of the ventricles, causing them to contract. This forces blood out of the heart to the lungs and the body. The pulmonary veins empty oxygenated blood from the lungs to the left atrium. A normal heart beats in a constant rhythm -- about 60 to 100 times per minute at rest.

What Is Atrial Fibrillation?

Atrial fibrillation (also referred to as AF or Afib) is the most common type of irregular heartbeat. It is found in about 2.2 million Americans. It increases with age. If you have AF, the impulse does not travel in an orderly fashion through the atria. Instead, many impulses begin simultaneously and spread through the atria and compete for a chance to travel through the AV node.

The firing of these impulses results in a very rapid and disorganized heartbeat. The rate of impulses through the atria can range from 300 to 600 beats per minute. Luckily, the AV node limits the number of impulses it allows to travel to the ventricles. As a result, the pulse rate is often less than 150 beats per minute, but this is often fast enough to cause symptoms.

What Are the Symptoms of Atrial Fibrillation?

You may have atrial fibrillation without having any symptoms at all. If you have symptoms, they may include:

  • Heart palpitations (a sudden pounding, fluttering, or racing feeling in the chest).
  • Lack of energy; feeling over-tired.
  • Dizziness (feeling faint or light-headed).
  • Chest discomfort (pain, pressure, or discomfort in the chest).
  • Shortness of breath (difficulty breathing during normal activities or even at rest).

What Causes Atrial Fibrillation?

Atrial fibrillation is associated with many conditions, including:

  • High blood pressure
  • Coronary artery disease (hardening of the heart arteries)
  • Heart valve disease
  • Having undergone heart surgery
  • Chronic lung disease
  • Heart failure
  • Cardiomyopathy (disease of heart muscle that causes heart failure)
  • Congenital (present at birth) heart disease
  • Pulmonary embolism (blood clot in lungs)

Less Common Causes of Atrial Fibrillation

Less common causes of atrial fibrillation include:

  • Hyperthyroidism (overactive thyroid).
  • Pericarditis (inflammation of the outside lining of the heart).
  • Viral infection.

In at least 10% of people with AF, no underlying heart disease is found. In many of these people, AF may be related to alcohol or excessive caffeine use, stress, certain drugs, electrolyte or metabolic imbalances, or severe infections. In some people, no identifiable cause can be found.

The risk of AF increases with age, particularly after age 60. According to the CDC, AF affects roughly one in every 10 persons aged 80 years or older.

Why Is Atrial Fibrillation Dangerous?

Many people live for years with atrial fibrillation without problems. However, because the atria are beating rapidly and irregularly, blood does not flow through them as quickly. This makes the blood more likely to clot. If the clot is pumped out of the heart, it can travel to the brain, resulting in a stroke. The likelihood of a stroke in people with AF is five to seven times higher than in the general population. Although about half of all blood clots related to AF result in stroke, clots can travel to other parts of the body -- such as the kidney, heart, or intestines -- also causing problems.

AF can also decrease the heart's pumping ability by as much as 20%-25%. AF combined with a fast heart rate over a period of days to months can result in heart failure. Control of AF can then improve heart failure, also over days to months.  

Chronic atrial fibrillation is associated with an increased risk of death.

How Is Atrial Fibrillation Diagnosed?

Four tests are used to diagnose atrial fibrillation, including:

  • Electrocardiogram
  • Holter monitor
  • Portable event monitor (also called a loop recorder)
  • Transtelephonic monitor

These monitoring devices help your doctor learn if you are having irregular heartbeats, what kind they are, how long they last, and what may be causing them.

How Is Atrial Fibrillation Treated?

Many options are available to treat AF, including medication, lifestyle changes, certain procedures, and surgery. The choice of treatment for you is based on your rhythm and symptoms. The goals of AF treatment are to:

Sudden Cardiac Death AWARENESS

Sudden cardiac death (SCD) is a sudden, unexpected death caused by loss of heart function (sudden cardiac arrest). It is the largest cause of natural death in the U.S., causing about 325,000 adult deaths in the United States each year. SCD is responsible for half of all heart disease deaths.

SCD occurs most frequently in adults in their mid-30s to mid-40s, and affects men twice as often as it does women. SCD is rare in children, affecting only 1 to 2 per 100,000 children each year.

How Is Sudden Cardiac Arrest Different from a Heart Attack?

Sudden cardiac arrest is not a heart attack (myocardial infarction) but can occur during a heart attack. Heart attacks occur when there is a blockage in one or more of the arteries to the heart, preventing the heart from receiving enough oxygen-rich blood. If the oxygen in the blood cannot reach the heart muscle, the heart becomes damaged.

In contrast, sudden cardiac arrest occurs when the electrical system to the heart malfunctions and suddenly becomes very irregular. The heart beats dangerously fast. The ventricles may flutter or quiver (ventricular fibrillation), and blood is not delivered to the body. In the first few minutes, the greatest concern is that blood flow to the brain will be reduced so drastically that a person will lose consciousness. Death follows unless emergency treatment is begun immediately.

Emergency treatment includes cardiopulmonary resuscitation (CPR) and defibrillation. CPR is a manual technique using repetitive pressing to the chest and breathing into the person's airways that keeps enough oxygen and blood flowing to the brain until the normal heart rhythm is restored with an electric shock to the chest, a procedure called defibrillation. Emergency squads use portable defibrillators and frequently there are public access defibrillators (AEDs, ambulatory external defibrillators) in public locations that are intended to be available for use by citizens who observe cardiac arrest.

What Are the Symptoms of Sudden Cardiac Arrest?

Some people may experience a racing heartbeat or they may feel dizzy, alerting them that a potentially dangerous heart rhythm problem has started. In over half of the cases, however, sudden cardiac arrest occurs without prior symptoms.

What Causes Sudden Cardiac Death?

Most sudden cardiac deaths are caused by abnormal heart rhythms called arrhythmias. The most common life-threatening arrhythmia is ventricular fibrillation, which is an erratic, disorganized firing of impulses from the ventricles (the heart's lower chambers). When this occurs, the heart is unable to pump blood and death will occur within minutes, if left untreated.

What Are the Risk Factors of Sudden Cardiac Arrest?

There are many factors that can increase a person's risk of sudden cardiac arrest and sudden cardiac death, including the following:

  • Previous heart attack with a large area of the heart damaged (75 percent of SCD cases are linked to a previous heart attack).
  • A person's risk of SCD is higher during the first six months after a heart attack.
  • Coronary artery disease (80 percent of SCD cases are linked with this disease).
    • Risk factors for coronary artery disease include smoking, family history of cardiovascular disease and high cholesterol.

Other risk factors include:

  • Ejection fraction of less than 40 percent, combined with ventricular tachycardia.
  • Prior episode of sudden cardiac arrest.
  • Family history of sudden cardiac arrest or SCD.
  • Personal or family history of certain abnormal heart rhythms, including long  or short QT syndrome, Wolff-Parkinson-White syndrome, extremely low heart rates, or heart block.
  • Ventricular tachycardia or ventricular fibrillation after a heart attack.
  • History of congenital heart defects or blood vessel abnormalities.
  • History of syncope (fainting episodes of unknown cause).
  • Heart failure: a condition in which the heart's pumping power is weaker than normal. Patients with heart failure are 6 to 9 times more likely than the general population to experience ventricular arrhythmias that can lead to sudden cardiac arrest.
  • Dilated cardiomyopathy (cause of SCD in about 10 percent of the cases): a decrease in the heart's ability to pump
  • Hypertrophic cardiomyopathy: a thickened heart muscle that especially affects the ventricles.
  • Significant changes in blood levels of potassium and magnesium (from using diuretics, for example), even if there is not underlying heart disease.
  • Obesity.
  • Diabetes.
  • Recreational drug abuse.
  • Taking drugs that are "pro-arrhythmic" may increase the risk for life-threatening arrhythmias.

Reducing your risk factors: If you have coronary artery disease -- and even if you do not -- there are certain lifestyle changes you can make to reduce your risk of sudden cardiac arrest.
These lifestyle changes include:

  • Quitting smoking
  • Losing weight
  • Exercising regularly
  • Following a low-fat diet
  • Managing diabetes
  • Managing other health conditions including high blood pressure and cholesterol

If you have questions or are unsure how make these changes, talk to your doctor. Patients and families should know the signs and symptoms of coronary artery disease and the steps to take if symptoms occur.

Implantable Cardioverter-Defibrillator (ICD)

An implantable cardioverter-defibrillator (ICD), also known as an automatic implantable cardioverter-defibrillator (AICD), is a small device that doctors use to watch for and fix life-threatening abnormal heart rhythms. The doctor surgically implants the defibrillator under the skin, usually below the left collarbone. A wire threaded through a large vein connects the device to the heart.

If you have had a serious episode of an abnormally fast heart rhythm or are at high risk for having one, you may need an ICD. If you have coronary artery disease, heart failure, or a problem with the structure or electrical system of the heart, you may be at risk for an abnormal heart rhythm.

How does an ICD work?

An ICD continuously monitors your heart. If it detects a life-threatening rapid heart rhythm, it sends an electric shock to your heart to restore a normal rhythm. The device then goes back to its monitoring mode.

After the shock, your heart may beat very slowly for several minutes. So ICDs also act as pacemakers, sending weaker shocks that pace the heart if the rate falls below a certain preset level.

Your doctor sets both the rate at which a shock will occur and the level of shock needed to convert to a normal rate and rhythm. If the first shock does not reset your heart rhythm, the device will send progressively stronger shocks until the heart converts to a normal rate.

Although an ICD effectively treats life-threatening episodes of abnormal heart rhythms, it does not prevent them. You will also need to take a medicine to prevent or at least decrease how often you have abnormal heart rhythms so that you are not getting too many shocks.

An example of a life-threatening heart rhythm is ventricular tachycardia.

Living with an ICD

You may feel worried by the possibility of being shocked. The shock itself can be uncomfortable-it may feel as if you are being kicked in the chest. You may pass out before the device fires, and you likely won't remember the shock. Be reassured, though, that the shock is life-saving.

Know what to do after a shock

Be sure you have a plan for what to do if you get a shock from your ICD. Talk to your doctor if you need to make a plan. In general, your plan depends on how you feel after you get a shock and how many times you get a shock.

Know what to stay away from

Strong electric or magnetic fields can interfere with the ICD. Most electrical equipment and household appliances create very weak magnetic fields and do not interfere with ICDs. So you can safely use most household and office equipment. And you can usually avoid electrical interference from magnetic or electrical sources by keeping certain things a few inches away from your pacemaker or ICD. You should completely avoid things like heavy electrical or industrial equipment.

Know when you can drive again

Driving is something else you need to think about if you have an ICD. Talk to your doctor about whether you should restrict your driving. Your doctor will check your medical history and review your risk of having another arrhythmia that could make driving unsafe. To help doctors with this decision, the American Heart Association and Heart Rhythm Society recommend the following driving restrictions:1, 2

  • If you get an ICD because you are at risk for a life-threatening arrhythmia (but have never had one), you should not drive for at least 1 week afterward to allow time to heal. After you heal, you can drive again as long as your ICD has never given you a shock and you have no symptoms of an arrhythmia. But keep in mind that an arrhythmia could cause you to pass out (lose consciousness).
  • If you get an ICD because you have already had a life-threatening arrhythmia, you should wait at least 6 months before you drive again.
  • If you have an ICD that has given you a shock for an arrhythmia, you should wait at least 6 months before you drive again.

The Watchman Study: a device alternative to warfarin (Coumadin) therapy

Dr. Drew Pickett, is the ONLY cardiologist in Tennessee enrolling patients in the Watchman Study via the Saint Thomas Research Institute


Atrial fibrillation (AF) is the most common type of sustained irregular heartbeat. It affects approximately 6 million U.S. adults, mainly those ages 65 and older. As the population continues aging, that number is expected to rise to almost 16 million by 2050. This growing prevalence lends increased urgency to the search for additional ways of preventing stroke, the most devastating complication of AF. The Watchman® Left Atrial Appendage (LAA) Closure Technology device may offer a new option for stroke prevention.

The current most common treatment for stroke prevention in people with AF is a prescription for warfarin (Coumadin), an oral anticoagulant. However, there are several major drawbacks to warfarin therapy. An increased risk of serious bleeding means that warfarin may be contraindicated for some people, including older adults who are at high risk for falls. In other cases, warfarin may still be prescribed, but the risk of dangerous bleeding means that people may be advised to curtail activities they once enjoyed, such as skiing and other sports in which falls are common.

It takes careful calibration to find the safe and effective dose for a particular patient, and monthly blood draws to monitor blood levels of the drug are required indefinitely. Warfarin also interacts with a number of prescription and over-the-counter medicines, such as antibiotics, salicylates, nonsteroidal anti-inflammatory drugs, beta-adrenergic blockers, diuretics, antidepressants, diabetes agents, and gastric acidity and peptic ulcer agents. Drug interactions can be problematic for older adults, who are often taking multiple medications. In addition, certain foods interfere with how warfarin works, which necessitates some dietary restrictions, such as limiting green leafy vegetables, Brussels sprouts, and broccoli.




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