The heart sounds are the noises (sound) generated by the beating heart and the resultant flow of blood through it. This is also called a heartbeat. In cardiac auscultation, an examiner uses a stethoscope to listen for these sounds, which provide important information about the condition of the heart.
In healthy adults, there are two normal heart sounds often described as a lub and a dub (or dup), that occur in sequence with each heart beat. These are the first heart sound (S1) and second heart sound (S2), produced by the turbulent flow against the closed AV valves and semilunar valves respectively. In addition to these normal sounds, a variety of other sounds may be present including heart murmurs, adventitious sounds, and gallop rhythms S3 and S4.
Heart murmurs are also generated by turbulent flow of blood, which may occur inside or outside the heart, but the sound has different characteristics than normal heart sounds. Murmurs may be physiological (benign) or pathological (abnormal). Abnormal murmurs can be caused by stenosis restricting the opening of a heart valve, resulting in turbulence as blood flows through it. Abnormal murmurs may also occur with valvular insufficiency (or regurgitation), which allows backflow of blood when the incompetent valve closes with only partial effectiveness. Different murmurs are audible in different parts of the cardiac cycle, depending on the cause of the murmur.
A bundle branch block will produce continuous splitting but the degree of splitting will still vary with respiration. If splitting does not vary with inspiration, it is termed a "fixed split S2" and is usually due to an atrial septal defect (ASD) or ventricular septal defect (VSD). The ASD or VSD creates a left to right shunt that increases the blood flow to the right side of the heart, thereby causing the pulmonic valve to close later than the aortic valve independent of inspiration/expiration.
Reverse splitting indicates pathology. Aortic stenosis, hypertrophic cardiomyopathy, left bundle branch block, and a ventricular pacemaker could all cause a reverse splitting of the second heart sound.
The following paragraphs overview the murmurs most commonly heard in adults who do not have major congenital heart abnormalities.
|Gradations of Murmurs|
|Grade 1||Very faint, heard only after listener has "tuned in"; may not be heard in all positions.|
|Grade 2||Quiet, but heard immediately after placing the stethoscope on the chest.|
|Grade 3||Moderately loud.|
|Grade 4||Loud, with palpable thrill (ie, a tremor or vibration felt on palpation)|
|Grade 5||Very loud, with thrill. May be heard when stethoscope is partly off the chest.|
|Grade 6||Very loud, with thrill. May be heard with stethoscope entirely off the chest.|
As noted, several different cardiac conditions can cause heart murmurs. However, the murmurs produced often change in complex ways with the severity of the cardiac disease. An astute physician can sometimes diagnose cardiac conditions with some accuracy based largely on the murmur, related physical examination and experience with the relative frequency of different heart conditions. However, with the advent of better quality and wider availability of echocardiography and other techniques, heart status can be recognized and quantified much more accurately than formerly possible with only a stethoscope, examination and experience.
Inhalation pressure causes an increase in the venous blood return to the right side of the heart. Therefore, right-sided murmurs generally increase in intensity with inspiration. The increased volume of blood entering the right sided chambers of the heart restricts the amount of blood entering the left sided chambers of the heart. This causes left-sided murmurs to generally decrease in intensity during inspiration.
With expiration, the opposite haemodynamic changes occur. This means that left-sided murmurs generally increase in intensity with expiration. Having the patient lie supine and raising their legs up to a 45 degree angle facilitates an increase in venous return to the right side of the heart producing effects similar to inhalation-increased blood flow.
There are a number of interventions that can be performed that alter the intensity and characteristics of abnormal heart sounds. These interventions can differentiate the different heart sounds to more effectively obtain a diagnosis of the cardiac anomaly that causes the heart sound.
Clicks: With the advent of newer, non-invasive imaging techniques, the origin of other, so-called adventitial sounds or "clicks" has been appreciated. These are short, high-pitched sounds.
Rubs: Patients with pericarditis, an inflammation of the sac surrounding the heart (pericardium), may have an audible pericardial friction rub. This is a characteristic scratching, creaking, high-pitched sound emanating from the rubbing of both layers of inflammated pericardium. It is the loudest in systole, but can often be heard at the beginning and at the end of diastole. It is very dependent on body position and breathing, and changes from hour to hour.
|Pulmonary valve (to pulmonary trunk)||second intercostal space||left upper sternal border|
|Aortic valve (to aorta)||second intercostal space||right upper sternal border|
|Mitral valve (to left ventricle)||fifth intercostal space||lateral to left midclavicular line|
|Tricuspid valve (to right ventricle)||fourth intercostal space||lower left sternal border|
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