Brought to you by St. Luke's Center for Heart and Vascular Health, expert(s) at Heart & Vascular.

Coronary artery disease, an equal opportunity killer

Abnormal heart rhythms

The heart is a muscle that works like a pump. It's divided into four chambers two atria at the top of the heart and two ventricles at the bottom. The heart beats when an electrical impulse from the heart's natural pacemaker the sinoatrial or SA node moves through it.

As long as the electrical impulse is transmitted normally, the heart pumps and beats at a regular pace. A normal heart beats 60 to 100 times a minute.

The term arrhythmia refers to any change from the normal sequence of electrical impulses, causing abnormal heart rhythms. This can cause the heart to pump less effectively. Some arrhythmias are so brief that the overall heart rate or rhythm isn't greatly affected. But if arrhythmias last for some time, they may cause the heart rate to be too slow or too fast or the heart rhythm to be erratic.

A fast heart rate is called tachycardia, and falls into two major categories. Ventricular tachycardia involves only the ventricles, while supraventricular tachycardia involves both the atria and the ventricles. The definition of too fast usually depends upon the person's age and physical activity.
Under certain conditions, the automatic firing rate of secondary pacemaker tissue may become too fast. If such an abnormal focus fires faster than the sinus node, it may take over control of the heart rhythm and cause tachycardia.

In another type of abnormal conduction, impulses get caught in a merry-go-round-like sequence. This process, called reentry, is a common cause of tachycardias. Regardless of their cause, tachycardias are classified by where they arise.

Rapid heart beating can produce symptoms of palpitations, rapid heart action, dizziness, lightheadedness, fainting or near fainting. Heartbeats may have either a regular or irregular rhythm. Rapid heart beating in the ventricles can be life-threatening. The most serious cardiac rhythm disturbance is ventricular fibrillation, where the lower chambers quiver and the heart can't pump any blood. Collapse and sudden death follows unless medical help is provided immediately.

If treated in time, ventricular tachycardia and ventricular fibrillation can be converted into normal rhythm with electrical shock. Rapid heart beating can be controlled with medications and by identifying or destroying the focus of rhythm disturbances. One effective way of correcting these life-threatening rhythms is by using an electronic device called an implantable cardioverter defibrillator.
A heart rate that's too slow is called bradycardia. This condition can cause fatigue, dizziness, lightheadedness, fainting or near-fainting spells. These symptoms can be easily corrected by implanting an electronic pacemaker under the skin to speed up the heart rhythm as needed.

Coronary Artery Disease (CAD)

Coronary Artery Disease (CAD) is the leading killer among both men and women in the United States. Roughly 13 million Americans suffer from the disease, and each year more than half a million die.

The first step toward stemming the high mortality rate of CAD is to become more educated on what the disease is, how it is treated, and how to better prevent it in the first place.

Coronary artery disease occurs when the arteries that supply blood to the heart muscle become hardened and narrowed, due to buildup of a material called plaque on the inner walls. As the plaque increases, the insides of the coronary arteries get narrower, and less blood can flow through. Eventually, blood flow to the heart muscle is reduced, and the heart muscle is not able to receive the amount of oxygen it needs. Reduced or cutoff blood flow and oxygen supply to the heart muscle can result in several conditions, including:

- Angina Chest pain or discomfort that occurs when the heart does not get enough blood.
- Heart attack When a blood clot develops at the site of plaque in a coronary artery and suddenly cuts off most or all blood supply to that part of the heart. Cells in the heart muscle begin to die if they do not receive enough oxygen-rich blood, which can cause permanent damage to the heart muscle.

If CAD goes untreated, it can weaken the heart muscle over time, which in turn can lead to heart failure or arrhythmias (changes in the normal rhythm of the heart).

Who is at risk for CAD?

Several factors increase the risk of developing CAD. The more risk factors you have, the greater chance you have of developing CAD. Some CAD risk factors can't be modified, but others can.

Risk factors that cannot be modified include:

- Age. As you get older, your risk for CAD increases. In men, risk increases after age 45. In women, risk increases after age 55.
- Family history of early heart disease. Heart disease diagnosed before age 55 in father or brother. Heart disease diagnosed before age 65 in mother or sister.

Risk factors that can be modified include:

- High blood cholesterol
- High blood pressure
- Cigarette smoking
- Diabetes
- Overweight or obesity
- Lack of physical activity

How is it diagnosed?

There is no single test to diagnose CAD. Your doctor will ask about your medical history and your family medical history, assess your risk factors, and do a physical exam and several tests. These procedures are used to decide if you have CAD, determine the extent of the disease and to rule out other possible causes of your symptoms.

Based on the results of these procedures, your doctor may order one or more of the following tests:

- EKG or Electrocardiogram This test measures the rate and regularity of your heartbeat.
- Echocardiogram This test uses sound waves to create a moving picture of your heart. The test can identify areas of poor blood flow to the heart, areas of heart muscle that are not contracting normally, as well as previous injury to the heart muscle caused by poor blood flow.
- Stress Test During stress testing, you exercise (or are given medicine if you are unable to exercise) to make your heart work harder and beat faster while heart tests are performed
- Chest X-Ray A chest x-ray takes a picture of the organs and structures inside the chest.
- Cardiac Catheterization A thin, flexible tube is passed through an artery in the groin or arm to reach the coronary arteries, allowing your doctor to examine the inside of your arteries to see if there is any blockage.
- Coronary Angiography - This test is usually performed along with cardiac catheterization. A dye that can be seen by x-ray is injected through the catheter into the coronary arteries, allowing the doctor to see the flow of blood through the heart.
- Nuclear Heart Scan A small amount of a radioactive tracer is injected into your bloodstream through a vein, usually in your arm. A special camera is placed in front of your chest providing your doctor with moving pictures of the blood passing through your heart's chambers and arteries. There are different types of nuclear heart scans. Most scans have two phases taking pictures of the heart at rest and while it is beating faster, although sometimes only a rest scan is done. Many heart problems show up more clearly when your heart is stressed than when it is at rest. By comparing the nuclear heart scan of your heart at rest to your heart at stress, your doctor can determine if your heart is functioning normally or not.
- Cardiac CT Scan - A cardiac CT scan is a heart imaging test undergoing rapid development and evaluation. A cardiac CT scan is a special noninvasive procedure that requires iodine-containing dye to be given to the patient.During this exam, information collected by the high-speed scanner is evaluated by a radiologist and cardiologist to identify CAD.

How can it be prevented?

Preventing or delaying CAD begins with knowing which risk factors you have and taking action. Remember, your chances of developing CAD increase with the number of risk factors you have.

Know your family history of health problems related to CAD. If you or someone in your family has CAD, be sure to tell your doctor. Make sure everyone in your family gets enough exercise and maintains a healthy body weight.

Information provided by the National Heart, Lung and Blood Institute.