Heart sounds
Main article: Heart sounds
One of the simplest methods of assessing the heart's condition is to listen to it using a stethoscope.[7] In a healthy heart, there are 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".[7] Each sound consists of two components, reflecting the slight difference in time as the two valves close.[32] S2 may split into two distinct sounds, either as a result of inspiration or different valvular or cardiac problems.[32] Additional heart sounds may also be present and these give rise to gallop rhythms. A third heart sound, S3 usually indicates an increase in ventricular blood volume. A fourth heart sound S4 is referred to as an atrial gallop and is produced by the sound of blood being forced into a stiff ventricle. The combined presence of S3 and S4 give a quadruple gallop.[7]
Heart murmurs are abnormal heart sounds which can be either pathological or benign.[33] One example of a murmur isStill's murmur, which presents a musical sound in children, has no symptoms and disappears in adolescence.[34]
A different type of sound, a pericardial friction rub can be heard in cases of pericarditis where the inflamed membranes can rub together.[35]
Clinical significance
Being such a complex organ the heart is prone to several cardiovascular diseasessome becoming more prevalent with ageing.[36] Heart disease is a major cause of death, accounting for an average of 30% of all deaths in 2008, globally.[11] This rate varies from a lower 28% to a high 40% in high-income countries.[12] Doctors that specialise in the heart are called cardiologists. Many other medical professionals are involved in treating diseases of the heart, including doctors such as general practitioners, cardiothoracic surgeons and intensivists, and allied health practitioners including physiotherapists and dieticians.
Obesity, high blood pressure, and high cholesterol can all increase the risk of developing heart disease. However, half the number of heart attacks occur in people with normal cholesterol levels. It is generally accepted that factors such as exercise or the lack of it, good or poor diet, and overall well-being (including emotional), affect heart health.[37][38][39][40] Exercise results in the addition ofprotein myofilaments and this can result in hypertrophy where the size of individual cells are increased but not their number.[7] This is a condition known asathletic heart syndrome. The hearts of athletes can pump more efficiently at lower heart rates. However, enlarged hearts can have a pathological cause such ashypertrophic cardiomyopathy, which can result in a heart of 1000 g (2 lb) in mass.[7] The cause of an abnormally enlarged heart muscle is unknown, but the condition is often undiagnosed and can cause sudden death in young athletes.[7]
Coronary artery disease is also known as ischemic heart disease, and atherosclerotic disease and is the most common form of heart disease. The underlying mechanism of this disease is atherosclerosis–a build-up of plaquealong the inner walls of the arteries which narrows them, reducing the blood flow to the heart. It is the leading cause ofheart attacks and the most common cause of death, globally.[41] It is also the main cause of angina.
Cardiomyopathy and most commonly dilated cardiomyopathy, is a noticeable deterioration of the heart muscle's ability to contract, which can lead to heart failure.[42][43] Other common causes of heart failure (which can also be congestive), are heart attacks, valve disorders and high blood pressure. This happens when the heart is pumping insufficiently and cannot meet the body's blood flow demands.[44] Because the heart is a double pump, each side can fail independently of the other, resulting in heart failure of the right heart or the left heart, either of which through causing strain in the other side can result in the failure of the whole heart. Congestive heart failure results in blood backing up in the systemic circulation. Edema(swelling) of the feet, ankles and fingers is the most noticeable symptom. Pulmonary congestion results from left heart failure. The right side of the heart continues to propel blood to the lungs, but the left side is unable to pump the returning blood into the systemic circulation. As blood vessels within the lungs become swollen with blood, the pressure within them increases, and fluid leaks from the circulation into the lung tissue. This pleural effusion causes pulmonary edema. If untreated, the person will suffocate because they are drowning in their own blood.[45]
Heart murmurs are abnormal heart sounds which can be either pathological or benign and there are several kinds.[33]Murmurs are graded by volume, from 1) the quietest, to 6) the loudest, and evaluated by their relationship to the heart sounds and position in the cardiac cycle.[32] Phonocardiograms can record these sounds.[7] Murmurs can result fromvalvular heart diseases due to narrowing (stenosis), regurgitation or insufficiency of any of the main heart valves but they can also result from a number of other disorders, including atrial and ventricular septal defects.[32]
Abnormalities in the sinus rhythm can prevent the heart from effectively pumping blood and cause both atrial andventricular fibrillation.[45] Examples of cardiac arhythmias are a very rapid heart rate (tachycardia) and a very slow heart rate (bradycardia). Tachycardia is generally defined as a heart rate faster than 100 beats per minute, and bradycardia as a heart rate slower than 60.[citation needed] Asystole is the cessation of heart rhythm which results in cardiac arrest. Cardiac arrest can be diagnosed by pulseless electrical activity showing on an echocardiogram.
Cardiac tamponade, also known as pericardial tamponade, is the condition of an abnormal build-up of fluid in the pericardium which can adversely affect the function of the heart. The fluid can be removed from the pericardial sac using a syringe in a procedure called pericardiocentesis.
Carditis is inflammation of the heart; this can be specific to regions as in pericarditis, myocarditis, and endocarditis or it can be of the whole heart known as pancarditis.
Tetralogy of Fallot is a congenital cyanotic heart defect and the most common cause of blue baby syndrome.[46]
Diagnosis
Diagnosis of the various conditions can be made by assessing the presented symptoms, initially by cardiac examination. The taking of a medical history is also of importance. Further examination can involve blood tests, echocardiograms, ECGsand imaging. Cardiac catheterisation can assist, for example, in the diagnosis of aortic stenosis.
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