Causes

Heart disease causes depend on your specific type of heart disease. There are many different types of heart disease. To understand the causes of heart disease, it helps to understand how the heart works.

How the heart works

Your heart is a pump. It's a muscular organ about the size of your fist, located slightly left of center in your chest. Your heart is divided into the right and the left sides.

• The right side of the heart includes the right atrium and ventricle. It collects and pumps blood to the lungs through the pulmonary arteries.
• The lungs give the blood a new supply of oxygen. The lungs also breathe out carbon dioxide, a waste product.
• Oxygen-rich blood then enters the left side of the heart, including the left atrium and ventricle.
• The left side of the heart pumps blood through the largest artery in the body (aorta) to supply tissues throughout the body with oxygen and nutrients.

Heart valves

Four heart valves keep your blood moving the right way by opening only one way and only when they need to. To work properly, the valves must be formed properly, must open all the way and must close tightly so there's no leakage. The four valves are:

• Tricuspid
• Mitral
• Pulmonary
• Aortic

Heartbeats

A beating heart squeezes (contracts) and relaxes in a continuous cycle.

• During contraction (systole), your ventricles squeeze tight, forcing blood into the vessels to your lungs and body.
• During relaxation (diastole), the ventricles are filled with blood coming from the upper chambers (left and right atria).

Electrical system

Your heart's electrical wiring keeps it beating. Your heartbeat controls the continuous exchange of oxygen-rich blood with oxygen-poor blood. This exchange keeps you alive.

• Electrical signals begin high in the upper right chamber (right atrium) and travel through specialized pathways to the ventricles, delivering the signal for the heart to pump.
• The system keeps your heart beating in a coordinated and normal rhythm, which keeps blood flowing.

Causes of coronary artery disease

A buildup of fatty plaques in your arteries (atherosclerosis) is the most common cause of coronary artery disease. Unhealthy lifestyle habits, such as a poor diet, lack of exercise, being overweight and smoking, can lead to atherosclerosis.

Causes of heart arrhythmia

Common causes of arrhythmias or conditions that can lead to arrhythmias include:

• Coronary artery disease
• Diabetes
• Drug abuse
• Excessive use of alcohol or caffeine
• Heart defects you're born with (congenital heart defects)
• High blood pressure
• Smoking
• Some over-the-counter medications, prescription medications, dietary supplements and herbal remedies
• Stress
• Valvular heart disease

In a healthy person with a normal, healthy heart, it's unlikely for a deadly arrhythmia to develop without some outside trigger, such as an electrical shock or the use of illegal drugs. However, in a heart that's diseased or deformed, the heart's electrical signals may not properly start or travel through the heart, making arrhythmias more likely to develop.

Causes of congenital heart defects

Congenital heart defects usually develop while a baby is in the womb. Heart defects can develop as the heart develops, about a month after conception, changing the flow of blood in the heart. Some medical conditions, medications and genes may play a role in causing heart defects.

Heart defects can also develop in adults. As you age, your heart's structure can change, causing a heart defect.

Causes of cardiomyopathy

The cause of cardiomyopathy, a thickening or enlarging of the heart muscle, may depend on the type:

• Dilated cardiomyopathy. The cause of this most common type of cardiomyopathy often is unknown. The condition usually causes the left ventricle to widen. Dilated cardiomyopathy may be caused by reduced blood flow to the heart (ischemic heart disease) resulting from damage after a heart attack, infections, toxins and certain drugs, including those used to treat cancer. It may also be inherited from a parent.
• Hypertrophic cardiomyopathy. This type usually is passed down through families (inherited). It can also develop over time because of high blood pressure or aging.
• Restrictive cardiomyopathy. This least common type of cardiomyopathy, which causes the heart muscle to become rigid and less elastic, can occur for no known reason. Or it may be caused by diseases, such as connective tissue disorders or the buildup of abnormal proteins (amyloidosis).

Causes of heart infection

A heart infection, such as endocarditis, is caused when germs reach your heart muscle. The most common causes of heart infection include:

• Bacteria
• Viruses
• Parasites

Causes of valvular heart disease

Many things can cause diseases of your heart valves. You may be born with valvular disease, or the valves may be damaged by conditions such as:

• Rheumatic fever
• Infections (infectious endocarditis)
• Connective tissue disorders