Heart disease



Last Review Date: September 4, 2017


What is it?

Heart disease is a general term that refers to a variety of acute and chronic medical conditions that affect one or more of the components of the heart. The heart is a muscular, fist-sized organ that is located in the left side of the chest cavity. It continuously pumps blood, beating as many as 100,000 times a day. The blood that the heart moves carries oxygen and nutrients throughout the body and transports carbon dioxide and other wastes to the lungs, kidneys and liver for removal. The heart ensures its own oxygen supply through a set of coronary arteries and veins. The heart is also an endocrine organ that produces the atrial natriuretic peptide (ANP) hormone and the brain natriuretic peptide (BNP) hormone, which coordinate heart function with blood vessels and the kidneys.

Internally, the heart is essentially hollow. It is divided vertically into two halves by a septum (or wall) and each side of the heart has two internal chambers – an atrium at the top and a ventricle at the bottom. Venous blood (deoxygenated blood) enters the right side of the heart through the right atrium and is pumped by the right ventricle to the lungs, where carbon dioxide is released from the blood and oxygen moves into the blood. This oxygenated blood is then transported to the left atrium and pumped by the left ventricle into arteries that carry it throughout the body. Four heart valves regulate the direction and flow of blood through the chambers of the heart. The heart's characteristic ‘lub-dub’ beat is the sound of these valves opening and shutting. The heart muscle itself is called the myocardium. Lining the chambers of the heart and the valves is a membrane called the endocardium. Encasing the outside of the heart is the pericardium – a layered membrane that is fibrous on the outside and serous (fluid-secreting) on the inside. The pericardium forms a protective barrier around the heart and allows it to beat in a virtually friction free environment.

Diseases affecting the heart may be structural (i.e. resulting from abnormalities in the structure of the heart) or functional (i.e. when the heart stops functioning as well as it should). Anything that damages the heart, decreases its supply of oxygen, makes it less efficient, or reduces its ability to fill and pump will disrupt the coordinated relationship between the heart, kidneys and blood vessels, harming not only the heart but the rest of the body as well.


Signs and symptoms

Heart diseases may be acute or chronic and they may be temporary, relatively stable, or progressive. They may cause a variety of signs and symptoms that frequently change and/or worsen over time. Patients with chronic heart diseases can have episodes with acutely worsened symptoms; these may resolve (either on their own or with treatment), persist, or even become life threatening. Patients with early heart disease may experience few or vague symptoms - such as fatigue, shortness of breath (with or without effort), dizziness and/or nausea -but these symptoms do not indicate what type of heart disease they have. These symptoms may also be seen with a variety of other conditions. Other signs and complications that may arise from heart disease include:

  • Arrhythmia (an irregular heartbeat)
  • Dilation (where one or more of the heart chambers is stretched, causing their interiors to become larger because of increased pressure)
  • Embolism (where a blood vessel is blocked by material that has travelled from a distant body site - the material is typically a blood clot, but can be fat, air or even amniotic fluid)
  • Shortness of breath (due to the body's inability to keep up with increased demands for oxygen during physical activity)
  • Heart failure (a clinical syndrome that results from any structural or functional disorder that impairs the ability of the ventricles to fill with or eject blood)
  • Acute myocardial Infarction (AMI) (death of muscle cells due to a blockage that is impeding blood flow in the coronary arteries)
  • Insufficient contraction (not emptying or filling completely)
  • Pain, frequently due to ischaemia (where reduced blood flow results in a lack of oxygen; this is called angina if it affects the heart or intermittent claudication if it occurs in the legs)
  • Regurgitation (a backflow of blood due to faulty heart valves) causing increased pressure on the blood vessels of the lungs and liver
  • Stenosis (a narrowing of the openings of the heart also due to faulty valves)
  • Tissue death (permanent loss of heart tissue due to a lack of oxygen, leading to scarring)
  • Ventricular hypertrophy (increased thickness of the walls of the heart, causing a decrease in the size of the chambers and a decrease in the flexibility of the heart)

Heart diseases may be due to:


Common heart diseases

Coronary heart disease (CHD) and coronary artery disease (CAD) are the most common forms of heart disease. They are usually part of a systemic cardiovascular disease (CVD) – a narrowing of the arteries in the heart and throughout the body over time due to a build-up of fatty deposits that form plaques (atherosclerosis). This narrowing can significantly limit the amount of blood carried by the arteries and decrease the amount of oxygen supplied to the tissues. The coronary blood vessels narrow gradually, and symptoms do not appear until most of the blood flow is lost to an area of the heart, when it can cause intermittent chest pain (angina) upon exercise that worsens in frequency and severity over time. When plaques suddenly enlarge (termed "unstable plaques"), an acute narrowing of the coronary artery can cause chest pain to develop at rest or with minimum exertion (termed "unstable angina"). It can even cause the death of an area of the myocardium as part of a heart attack (myocardial infarction). These forms of acute onset of chest pain are termed acute coronary syndrome.

Heart failure, usually called congestive heart failure (CHF), causes the heart to become less effective at circulating blood and less able to completely fill or empty the chambers. As a result, blood backs up into the legs, hands, feet, lungs and liver, causing swelling, shortness of breath and fatigue. Any gradual damage to the heart can lead to heart failure over time; most commonly, this is due to coronary artery disease, high blood pressure (hypertension), heart valve damage (which can be either congenital or due to an infection) or a previous heart attack. If the cause is temporary, heart failure may also be temporary; however, it usually is a chronic condition that worsens over time, although it often improves after treatment.

Cardiomyopathy is an abnormality of the heart muscle. It may be congenital or it may occur when the heart responds to external pressures or toxins. One or more chambers of the heart may dilate (dilated cardiomyopathy), causing the chamber(s) to increase in size. In other cases, one or more of the walls of the heart may thicken (hypertrophic cardiomyopathy). Occasionally, cardiomyopathy may also be due to abnormal material accumulating in the wall of the heart, which reduces the flexibility of the ventricle walls (restrictive cardiomyopathy). Cardiomyopathy may be due to decreased blood flow to the heart, exposure to chemicals that damage the heart (such as alcohol, cocaine and some drugs used to treat cancer or other conditions), or inherited muscle problems, or it may have no obvious cause (idiopathic cardiomyopathy).

Myocarditis refers to inflammation of the heart muscle. It often presents with an acute onset of shortness of breath or an irregular heart beat and it can cause heart failure to develop quickly. It is often due to a viral infection.

Pericardial disease is a disease of the sac surrounding the heart. It may be due to a bacterial or fungal infection, trauma, an autoimmune process, cancer, or a previous heart attack. Infections of the pericardium may quickly become serious if left untreated. Pericarditis (inflammation of the pericardium) may cause increased friction “rub” and pain in the chest cavity.

Congenital heart disease, which arises during fetal development, may potentially affect any part of the heart. The amount of dysfunction depends on what form the abnormality takes and the extent to which it alters the shape, integrity, and functionality of the heart.

Endocarditis refers to inflammation of the membrane that lines the heart and heart valves. It may be due to a microorganism or an autoimmune process. When it is due to an infection, it oten can be difficult to treat.

Heart valve conditions may cause a variety of dysfunctions, including:

  • Regurgitation (backflow of blood)
  • Prolapse (where part of the heart valve protrudes into the atrium, preventing a tight seal, which may lead to regurgitation and an increased risk of endocarditis)
  • Stenosis (a narrowing of the opening, which can affect blood flow rate)

Tests

When testing for heart disease, the goal is to distinguish between heart-related symptoms and symptoms that are caused by another condition. Testing is ordered to help determine which heart disease is present, whether the disorder is acute or chronic, and the severity and extent of the disease. It is also ordered to monitor a cardiac event that is in progress (such as a heart attack).

When a patient presents to the emergency room with acute coronary syndrome – a group of symptoms that suggest heart injury due to a lack of blood flow – they are evaluated with a variety of laboratory blood tests and other tests. These are used to determine the cause of the pain and the severity of the condition. Since some treatments for a heart attack must be given within a short period of time to minimise heart damage, an accurate diagnosis must be quickly confirmed.

Heart disease that is causing few symptoms may be detected during a visit to the doctor for nonspecific symptoms such as fatigue. Doctors may order a variety of blood tests and other tests to investigate possible causes for the patient’s symptoms. Diagnosis of heart disease in these people may take time and patience.

Testing patients for existing heart disease is not the same as cardiac risk testing (which gives a measure of the risk of coronary heart disease). Cardiac risk testing is performed to screen asymptomatic people – i.e., to help determine their risk of developing coronary heart disease.

Laboratory blood tests

Cardiac biomarkers - proteins that are released when muscle cells are damaged - are frequently ordered when patients have symptoms of acute coronary syndrome, such as chest pain; pain in the jaw, neck, abdomen, or back, or pain that radiates to the shoulder or arms; nausea; dyspnoea; and lightheadedness.

Doctors will test for:

  • Cardiac troponin I or T  (This is the most commonly ordered and cardiac-specific of the markers. It will be elevated within a few hours of heart damage and will remain elevated for up to two weeks.)
  • CK-MB (This one particular form of the enzyme creatine kinase which is found mostly in heart muscle and rises when there is damage to the heart muscle cells. This test has been replaced by the more specific cardiac troponin test.)
  • Brain natriuretic peptide (This is released by the body as a natural response to heart failure. Increased levels of BNP, while not diagnostic for a heart attack, indicate an increased risk of cardiac problems in persons with acute coronary syndrome.)

The heart also releases BNP when it is stretched, and for this reason BNP is also measured in those who have swelling in the legs or abdomen or shortness of breath to see if heart failure may be present.

More general blood tests that may be ordered:

 

Other evaluations

A range of other evaluations and tests are used to assess chest pain and other symptoms. These include:

  • A medical history, including an evaluation of risk factors (such as age, CAD, diabetes, and smoking)
  • A physical examination
  • An electrocardiogram or ECG (which looks at the heart’s electrical activity and rhythm)
  • Echocardiography (ultrasound imaging of the heart)

Based on the findings of these tests, other procedures may be necessary, including:

  • Stress testing
  • A chest X-ray
  • CT (Computerised tomography) scan
  • Continuous ECG monitoring (sometimes also called Holter monitoring, where the patient wears a monitor that evaluates heart rhythm over a period of time)
  • MRI (Magnetic resonance imaging)
  • PET (Positron emission tomography)
  • Radionuclide imaging
  • Cardiac catheterisation (a thin flexible tube is inserted into an artery in the leg and threaded up to the coronary arteries to evaluate blood flow and pressure in the heart, as well as the status of the arteries in the heart)
  • Coronary angiography (X-rays are taken of the arteries using a radio-opaque dye to help diagnose CAD; this procedure is performed during coronary catheterisation)
  • Tilt table test (to evaluate syncope)

Treatment

Treatments for heart disease depend on the condition and its severity. Acute conditions, such as a heart attack, require prompt medical intervention to minimise heart damage. For chronic conditions, doctors may recommend that their affected patients modify their diets, lose excess weight, exercise (under supervision), manage stress and quit smoking. Conditions such as hypertension and diabetes should be controlled to minimise their effect on the heart. Heart failure often requires treatment with low salt diet and diuretics (to try to reduce the amount of fluid accumulating) as well as drugs to improve the function of the heart muscle.

Medications may be necessary to help manage symptoms and control heart diseases. Surgical procedures may be required to bypass blocked arteries, replace defective heart valves or fix congenital abnormalities. Those with infections may need to take antimicrobial drugs.

New medications, procedures and guidelines for addressing heart disease continue to be developed. Patients should talk to their doctor about the best treatment options for their condition.


Related pages

On this site
Tests: Cholesterol, HDL, LDL, triglycerides, lipid profile, CK, CK-MB, myoglobin, troponin, BNP, homocysteine, cardiac risk assessment, LDH, hs-CRP
Conditions: Heart attack, stroke, congestive heart failure, angina, cardiovascular disease

Elsewhere on the web
National Heart Foundation
Healthdirect Australia: Heart Health
NIH: NHLBI - What is a Heart Attack? (US)
NIH: National Heart, Lung & Blood Institute (US)
Medline Plus Medical Encyclopedia – Heart Diseases
Centers for Disease Control and Prevention: Heart disease (US)