Picture of the Heart

Human Anatomy

Illustration of the human heart
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The heart is a muscular organ about the size of a fist, located just behind and slightly left of the breastbone. The heart pumps blood through the network of arteries and veins called the cardiovascular system.

The heart has four chambers:

  • The right atrium receives blood from the veins and pumps it to the right ventricle.
  • The right ventricle receives blood from the right atrium and pumps it to the lungs, where it is loaded with oxygen.
  • The left atrium receives oxygenated blood from the lungs and pumps it to the left ventricle.
  • The left ventricle (the strongest chamber) pumps oxygen-rich blood to the rest of the body. The left ventricle’s vigorous contractions create our blood pressure.

The coronary arteries run along the surface of the heart and provide oxygen-rich blood to the heart muscle. A web of nerve tissue also runs through the heart, conducting the complex signals that govern contraction and relaxation. Surrounding the heart is a sac called the pericardium.

Heart Conditions

  • Coronary artery disease: Over the years, cholesterol plaques can narrow the arteries supplying blood to the heart. The narrowed arteries are at higher risk for  complete blockage from a sudden blood clot (this blockage is called a heart attack).
  • Stable angina pectoris: Narrowed coronary arteries cause predictable chest pain or discomfort with exertion. The blockages prevent the heart from receiving the extra oxygen needed for strenuous activity. Symptoms typically get better with rest.
  • Unstable angina pectoris: Chest pain or discomfort that is new, worsening, or occurs at rest. This is an emergency situation as it can precede a heart attack, serious abnormal heart rhythm, or cardiac arrest.
  • Myocardial infarction (heart attack): A coronary artery is suddenly blocked. Starved of oxygen, part of the heart muscle dies.
  • Arrhythmia (dysrhythmia): An abnormal heart rhythm due to changes in the conduction of electrical impulses through the heart. Some arrhythmias are benign, but others are life-threatening.
  • Congestive heart failure: The heart is either too weak or too stiff to effectively pump blood through the body. Shortness of breath and leg swelling are common symptoms.
  • Cardiomyopathy: A disease of heart muscle in which the heart is abnormally enlarged, thickened, and/or stiffened. As a result, the heart's ability to pump blood is weakened.
  • Myocarditis: Inflammation of the heart muscle, most often due to a viral infection.
  • Pericarditis: Inflammation of the lining of the heart (pericardium). Viral infections, kidney failure, and autoimmune conditions are common causes.
  • Pericardial effusion: Fluid between the lining of the heart (pericardium) and the heart itself. Often, this is due to pericarditis.
  • Atrial fibrillation: Abnormal electrical impulses in the atria cause an irregular heartbeat. Atrial fibrillation is one of the most common arrhythmias.
  • Pulmonary embolism: Typically a blood clot  travels through the heart to the lungs. 
  • Heart valve disease: There are four heart valves, and each can develop problems. If severe, valve disease can cause congestive heart failure.
  • Heart murmur: An abnormal sound heard when listening to the heart with a stethoscope. Some heart murmurs are benign; others suggest heart disease.
  • Endocarditis: Inflammation of the inner lining or heart valves of the heart. Usually, endocarditis is due to a serious infection of the heart valves.
  • Mitral valve prolapse: The mitral valve is forced backward slightly after blood has passed through the valve. 
  • Sudden cardiac death: Death caused by a sudden loss of heart function (cardiac arrest).
  • Cardiac arrest: Sudden loss of heart function.


Heart Tests

  • Electrocardiogram (ECG or EKG): A tracing of the heart’s electrical activity. Electrocardiograms can help diagnose many heart conditions.
  • Echocardiogram: An ultrasound of the heart. An echocardiogram provides direct viewing of any problems with the heart muscle’s pumping ability and heart valves.
  • Cardiac stress test: By using a treadmill or medicines, the heart is stimulated to pump to near-maximum capacity. This may identify people with coronary artery disease.
  • Cardiac catheterization: A catheter is inserted into the femoral artery in the groin and threaded into the coronary arteries. A doctor can then view X-ray images of the coronary arteries or any blockages and perform stenting or other procedures.
  • Holter monitor: If a doctor suspects an arrhythmia, a portable heart monitor can be worn. Called a Holter monitor, it records the heart's rhythm continuously for a 24 hour period.
  • Event monitor: If a doctor suspects an infrequent arrhythmia, a portable heart monitor called an event monitor can be worn. When you develop symptoms, you can push a button to record the heart's electrical rhythm.


Heart Treatments

  • Exercise: Regular exercise is important for heart health and most heart conditions. Talk to your doctor before starting an exercise program if you have heart problems.
  • Angioplasty: During cardiac catheterization, a doctor inflates a balloon inside a narrowed or blocked coronary artery to widen the artery. A stent is often then placed to keep the artery open.
  • Percutaneous coronary intervention (PCI): Angioplasty is sometimes called a PCI or PTCA (percutaneous transluminal coronary angioplasty) by doctors.
  • Coronary artery stenting: During cardiac catheterization, a doctor expands a wire metal stent inside a narrowed or blocked coronary artery to open up the area. This lets blood flow better and can abort a heart attack or relieve angina (chest pain).
  • Thrombolysis: “Clot-busting” drugs injected into the veins can dissolve a blood clot causing a heart attack. Thrombolysis is generally only done if stenting is not possible.
  • Lipid-lowering agents: Statins and other cholesterol (lipid) lowering drugs reduce the risk for heart attack in high-risk people.
  • Diuretics: Commonly called water pills, diuretics increase urination and fluid loss. This reduces blood volume, improving symptoms of heart failure.
  • Beta-blockers: These medicines reduce strain on the heart and lower heart rate. Beta-blockers are prescribed for many heart conditions, including heart failure and arrhythmias.
  • Angiotensin-converting enzyme inhibitors (ACE inhibitors): These blood pressure medicines also help the heart after some heart attacks or in congestive heart failure.
  • Aspirin: This powerful medicine helps prevent blood clots (the cause of heart attacks). Most people who have had heart attacks should take aspirin.
  • Clopidogrel (Plavix): A clot-preventing medicine that prevents platelets from sticking together to form clots. Clopidogrel is especially important for many people who have had stents placed.
  • Antiarrhythmic medications: Numerous medicines help control the heart’s rate and electrical rhythm. These help prevent or control arrhythmias.
  • AED (automated external defibrillator): If someone has sudden cardiac arrest, an AED can be used to assess the heart rhythm and send an electrical shock to the heart if necessary.
  • ICD (Implantable cardioverter defibrillator): If a doctor suspects you are at risk for a life-threatening arrhythmia, an implantable cardioverter defibrillator may be surgically implanted to monitor your heart rhythm and send an electrical shock to the heart if necessary.
  • Pacemaker: To maintain a stable heart rate, a pacemaker can be implanted. A pacemaker sends electrical signals to the heart when necessary to help it beat properly.
WebMD Image Collection Reviewed by Varnada Karriem-Norwood, MD on November 15, 2014




National Institutes of Health.

American Heart Association.

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