Mechanical replacement heart valves produce loud clicks due to the opening and closing of the valve. These prosthetic sounds may be muffled or absent if valve movement is impeded by thrombus or vegetations.
Turbulent blood flow causes heart murmurs. Turbulence may be produced when there is high blood flow through a normal valve, or when there is normal blood flow through an abnormal valve or into a dilated chamber. Turbulence is also caused by the regurgitation of blood through a leaking valve. Murmurs produced by highvelocity blood flow (e.g. the systolic murmur of mitral regurgitation) are high frequency and are often described as ‘blowing’ in quality. The intensity of murmurs is determined not only by the blood velocity but also by the volume of blood producing the murmur and the distance of the source of the murmur from the stethoscope. Rightsided murmurs tend to become louder on inspiration because inspiration increases the venous return to the right heart. Heart murmurs may occur with a normal or nearnormal heart (innocent murmurs). They are usually soft and short, and occur early in systole. Murmurs also occur in the following situations:
ANAEMIA, THYROTOXICOSIS, PREGNANCY AND OTHER CAUSES OF A HIGH CARDIAC OUTPUT produce flow murmurs, which are usually brief systolic ejection murmurs heard best at the left sternal edge or in the pulmonary area. These murmurs are believed to emanate from the pulmonary or aortic valve. Similar murmurs are heard in association with skeletal abnormalities such as kyphoscoliosis or funnel chest.
A VERY SMALL VENTRICULAR SEPTAL DEFECT may produce a short early systolic murmur, heard well at the left sternal edge. The murmur is short because contraction of the ventricle closes the small defect early in systole.
A BUZZING, TWANGING OR VIBRATORY MURMUR, called Still’s murmur, may be heard at the lower left sternal edge or cardiac apex. It is thought to arise from the region below the aortic valve. Murmurs are classified as systolic, diastolic or continuous. Another functional classification divides systolic murmurs into ejection or regurgitant. Murmurs should be assessed carefully; a summary of the auscultation procedure is shown. The intensity of cardiac murmurs can be graded as indicated.
SYSTOLIC MURMURS Systolic murmurs occur synchronously with carotid pulsation. There are three main varieties of pathological systolic murmur:
1 Ejection mid-systolic murmurs are heard separately from the first and second heart sounds. Their intensity rises then falls, being greatest in mid-systole.
2 Pan-systolic murmurs extend from the first to the second heart sound and tend to be of constant intensity throughout the whole of systole.
3 Late systolic murmurs are separated from the first sound but extend up to the second sound.
DIASTOLIC MURMURS (Table 11.8). Diastolic murmurs are always associated with cardiac disease. They are of two types:
1 Mid-diastolic murmurs usually arise from the mitral and tricuspid valves. In aortic regurgitation the flow of blood back into the left ventricle may partially close and obstruct the mitral valve, producing a mitral middiastolic murmur (Austin Flint murmur).
2 Early diastolic murmurs usually result from aortic regurgitation and rarely from pulmonary regurgitation. These murmurs begin with the second heart sound and are blowing (high-pitched) in quality. Pulmonary hypertension secondary to mitral stenosis may lead to pulmonary valve regurgitation (Graham Steell murmur).
CONTINUOUS MURMURS. A continuous murmur may occur because of a combination of systolic and diastolic murmurs, due to connections between the aorta and pulmonary artery (e.g. patent ductus arteriosus) or due to arteriovenous anastomoses and collateral circulations such as those associated with coarctation of the aorta. High venous flow, especially in young children, can produce a continuous venous hum in the neck. This is reduced by occluding the vein or by lying the child flat. Similarly, high mammary blood flow in pregnant or lactating women can produce a continuous murmur known as a mammary souffle.
Extra cardiac sounds
Bruits, usually due to arterial stenoses, are murmurs arising from a peripheral artery, including the distal aorta .
A pericardial friction rub is a scratching or crunching noise produced by the movement of inflamed pericardium. Since it is relatively high frequency, it is best heard with the diaphragm. It is most obvious in systole but may also be heard in early diastole or synchronously with atrial contraction. It should be listened for during both held inspiration and expiration.