Diseases Cardiovascular diseases, which include diseases of the heart, are the leading cause of death worldwide. The majority of cardiovascular disease is noncommunicable and related to lifestyle and other factors, becoming more prevalent with ageing.
Ischemic heart disease Coronary artery disease, also known as ischemic heart disease, is caused by
atherosclerosis—a build-up of fatty material along the inner walls of the arteries. These fatty deposits known as atherosclerotic plaques
narrow the coronary arteries, and if severe may reduce blood flow to the heart. If a narrowing (or stenosis) is relatively minor then the patient may not experience any symptoms. Severe narrowings may cause chest pain (
angina) or breathlessness during exercise or even at rest. The thin covering of an atherosclerotic plaque can rupture, exposing the fatty centre to the circulating blood. In this case a clot or thrombus can form, blocking the artery, and restricting blood flow to an area of heart muscle causing a myocardial infarction (a heart attack) or
unstable angina. In the worst case this may cause
cardiac arrest, a sudden and utter loss of output from the heart.
Obesity,
high blood pressure, uncontrolled
diabetes, smoking and high
cholesterol can all increase the risk of developing atherosclerosis and coronary artery disease.
Pericardial disease The sac which surrounds the heart, called the pericardium, can become inflamed in a condition known as
pericarditis. This condition typically causes chest pain that may spread to the back, and is often caused by a viral infection (
glandular fever,
cytomegalovirus, or
coxsackievirus). Fluid can build up within the pericardial sac, referred to as a
pericardial effusion. Pericardial effusions often occur secondary to pericarditis, kidney failure, or tumours, and frequently do not cause any symptoms. However, large effusions or effusions which accumulate rapidly can compress the heart in a condition known as
cardiac tamponade, causing breathlessness and potentially fatal low blood pressure. Fluid can be removed from the pericardial space for diagnosis or to relieve tamponade using a syringe in a procedure called
pericardiocentesis.
Congenital heart disease Some people are born with hearts that are abnormal and these abnormalities are known as congenital heart defects. They may range from the relatively minor (e.g.
patent foramen ovale, arguably a variant of normal) to serious life-threatening abnormalities (e.g.
hypoplastic left heart syndrome). Common abnormalities include those that affect the heart muscle that separates the two side of the heart (a "hole in the heart", e.g.
ventricular septal defect). Other defects include those affecting the heart valves (e.g.
congenital aortic stenosis), or the main blood vessels that lead from the heart (e.g.
coarctation of the aorta). More complex syndromes are seen that affect more than one part of the heart (e.g.
Tetralogy of Fallot). Some congenital heart defects allow blood that is low in oxygen that would normally be returned to the lungs to instead be pumped back to the rest of the body. These are known as
cyanotic congenital heart defects and are often more serious. Major congenital heart defects are often picked up in childhood, shortly after birth, or even before a child is born (e.g.
transposition of the great arteries), causing breathlessness and a lower rate of growth. More minor forms of congenital heart disease may remain undetected for many years and only reveal themselves in adult life (e.g.,
atrial septal defect).
Channelopathies Channelopathies can be categorized based on the organ system they affect. In the cardiovascular system, the electrical impulse required for each heart beat is provided by the
electrochemical gradient of each heart cell. Because the beating of the heart depends on the proper movement of ions across the surface membrane, cardiac ion channelopathies form a major group of heart diseases. Cardiac ion channelopathies may explain some of the cases of
sudden death syndrome and
sudden arrhythmic death syndrome. Long QT syndrome is the most common form of cardiac channelopathy. •
Long QT syndrome (LQTS) – Mostly hereditary. On EKG can be observed as longer corrected QT interval (QTc). Characterized by fainting, sudden, life-threatening heart rhythm disturbances –
Torsades de pointes type ventricular tachycardia, ventricular fibrillation and risk of sudden cardiac death. •
Short QT syndrome. •
Catecholaminergic polymorphic ventricular tachycardia (CPVT). •
Progressive cardiac conduction defect (PCCD). •
Early repolarisation syndrome (BER) – common in younger and active people, especially men, because it is affected by higher
testosterone levels, which cause increased potassium currents, which further causes an elevation of the
J-point on the EKG. In very rare cases, it can lead to ventricular fibrillation and death. •
Brugada syndrome – a genetic disorder characterized by an abnormal EKG and is one of the most common causes of sudden cardiac death in young men.
Diagnosis Heart disease is diagnosed by the taking of a
medical history, a
cardiac examination, and further investigations, including
blood tests,
echocardiograms,
electrocardiograms, and
imaging. Other invasive procedures such as
cardiac catheterisation can also play a role.
Examination The cardiac examination includes inspection, feeling the chest with the hands (
palpation) and listening with a stethoscope (
auscultation). It involves assessment of
signs that may be visible on a person's hands (such as
splinter haemorrhages), joints and other areas. A person's pulse is taken, usually at the
radial artery near the wrist, in order to assess for the rhythm and strength of the pulse. The
blood pressure is taken, using either a manual or automatic
sphygmomanometer or using
a more invasive measurement from within the artery. Any elevation of the
jugular venous pulse is noted. A person's
chest is felt for any transmitted vibrations from the heart, and then listened to with a stethoscope.
Heart sounds showing the mitral valve (right), tricuspid and mitral valves (top left) and aortic valve (top right). The closure of the heart valves causes the
heart sounds. Typically, healthy hearts have only two audible
heart sounds, called S1 and S2. The
first heart sound S1, is the sound created by the closing of the atrioventricular valves during ventricular contraction and is normally described as "lub". The
second heart sound, S2, is the sound of the semilunar valves closing during ventricular diastole and is described as "dub". S2 may
split into two distinct sounds, either as a result of inspiration or different valvular or cardiac problems. with either a high level or a significant rise being diagnostic. A test for
brain natriuretic peptide (BNP) can be used to evaluate for the presence of heart failure, and rises when there is increased demand on the left ventricle. These tests are considered
biomarkers because they are highly specific for cardiac disease. Testing for the
MB form of creatine kinase provides information about the heart's blood supply, but is used less frequently because it is less specific and sensitive. Other blood tests are often taken to help understand a person's general health and risk factors that may contribute to heart disease. These often include a
full blood count investigating for
anaemia, and
basic metabolic panel that may reveal any disturbances in electrolytes. A
coagulation screen is often required to ensure that the right level of anticoagulation is given.
Fasting lipids and
fasting blood glucose (or an
HbA1c level) are often ordered to evaluate a person's
cholesterol and diabetes status, respectively.
Electrocardiogram Using surface electrodes on the body, it is possible to record the electrical activity of the heart. This tracing of the electrical signal is the electrocardiogram (ECG) or (EKG). An ECG is a
bedside test and involves the placement of ten leads on the body. This produces a "12 lead" ECG (three extra leads are calculated mathematically, and one lead is
electrically ground, or earthed). There are five prominent features on the ECG: the
P wave (atrial depolarisation), the
QRS complex (ventricular depolarisation) and the
T wave (ventricular repolarisation). Echocardiograms can also be conducted under circumstances when the body is more stressed, in order to examine for signs of lack of blood supply. This
cardiac stress test involves either direct exercise, or where this is not possible, injection of a drug such as
dobutamine. CT scans,
chest X-rays and other forms of imaging can help evaluate the heart's size, evaluate for signs of
pulmonary oedema, and indicate whether there is
fluid around the heart. They are also useful for evaluating the aorta, the major blood vessel which leaves the heart.
Treatment Diseases affecting the heart can be treated by a variety of methods including lifestyle modification, drug treatment, and surgery.
Ischemic heart disease Narrowings of the coronary arteries (ischemic heart disease) are treated to relieve symptoms of chest pain caused by a partially narrowed artery (angina pectoris), to minimise heart muscle damage when an artery is completely occluded (
myocardial infarction), or to prevent a myocardial infarction from occurring. Medications to improve angina symptoms include
nitroglycerin,
beta blockers, and calcium channel blockers, while preventative treatments include
antiplatelets such as
aspirin and
statins, lifestyle measures such as stopping smoking and weight loss, and treatment of risk factors such as high blood pressure and diabetes. In addition to using medications, narrowed heart arteries can be treated by expanding the narrowings or redirecting the flow of blood to bypass an obstruction. This may be performed using a
percutaneous coronary intervention, during which narrowings can be expanded by passing small balloon-tipped wires into the coronary arteries, inflating the balloon to expand the narrowing, and sometimes leaving behind a metal scaffold known as a stent to keep the artery open. If the narrowings in coronary arteries are unsuitable for treatment with a percutaneous coronary intervention, open surgery may be required. A
coronary artery bypass graft can be performed, whereby a blood vessel from another part of the body (the
saphenous vein,
radial artery, or
internal mammary artery) is used to redirect blood from a point before the narrowing (typically the
aorta) to a point beyond the obstruction.
Cardiac arrhythmias Abnormal heart rhythms (
arrhythmias) can be treated using antiarrhythmic drugs. These may work by manipulating the flow of electrolytes across the cell membrane (such as
calcium channel blockers,
sodium channel blockers,
amiodarone, or
digoxin), or modify the autonomic nervous system's effect on the heart (
beta blockers and
atropine). In some arrhythmias such as atrial fibrillation which increase the risk of stroke, this risk can be reduced using anticoagulants such as
warfarin or
novel oral anticoagulants. If medications fail to control an arrhythmia, another treatment option may be
catheter ablation. In these procedures, wires are passed from a
vein or
artery in the leg to the heart to find the abnormal area of tissue that is causing the arrhythmia. The abnormal tissue can be intentionally damaged, or ablated, by
heating or
freezing to prevent further heart rhythm disturbances. Whilst the majority of arrhythmias can be treated using minimally invasive catheter techniques, some arrhythmias (particularly
atrial fibrillation) can also be treated using open or
thoracoscopic surgery, either at the time of other cardiac surgery or as a standalone procedure. A
cardioversion, whereby an electric shock is used to stun the heart out of an abnormal rhythm, may also be used. Cardiac devices in the form of
pacemakers or
implantable defibrillators may also be required to treat arrhythmias. Pacemakers, comprising a small battery powered generator implanted under the skin and one or more leads that extend to the heart, are most commonly used to treat abnormally
slow heart rhythms. Implantable defibrillators are used to treat serious life-threatening rapid heart rhythms. These devices monitor the heart, and if dangerous heart racing is detected can automatically deliver a shock to restore the heart to a normal rhythm. Implantable defibrillators are most commonly used in patients with heart failure,
cardiomyopathies, or inherited arrhythmia syndromes.
Heart failure As well as addressing the underlying cause for a patient's heart failure (most commonly
ischemic heart disease or
hypertension), the mainstay of heart failure treatment is with medication. These include drugs to prevent fluid from accumulating in the lungs by increasing the amount of urine a patient produces (
diuretics), and drugs that attempt to preserve the pumping function of the heart (
beta blockers,
ACE inhibitors and
mineralocorticoid receptor antagonists). In some patients with heart failure, a specialised pacemaker known as
cardiac resynchronisation therapy can be used to improve the heart's pumping efficiency. These devices are frequently combined with a defibrillator. In very severe cases of heart failure, a small pump called a
ventricular assist device may be implanted which supplements the heart's own pumping ability. In the most severe cases, a
cardiac transplant may be considered. == History ==