Health sciences have come far since Hippocrates first put his ear to the chest of a dying man and listened for the familiar "lub-dub" sound of the heart. Shaking the patient and then listening to the sounds evoked in the chest was a method found useful for assessment by men of science in early centuries before Christ. The most practical means of auscultation came centuries later with the invention of the stethoscope in 1817 by a French physician named Laennec, who was embarrassed to put his head to the chest of a young woman to listen to her heart.1
Perhaps one of the greatest advances made to the art of physical assessment, the stethoscope allowed for a discreet examining distance from the body, better acuity of sound and a professional, scientific approach. Over the next 100 years, the stethoscope would evolve to be the familiar instrument that is so commonly used today.
Accurate physical assessment is an art and one practiced daily by healthcare practitioners and students honing their medical and nursing skills. Learning normal human physiology is a prerequisite to understanding the pathology associated with disease states. This is also true for normal body sounds.
One of the most difficult areas to become proficient in is the fine art of cardiac auscultation. For this, one must have an unhurried systematic approach, an understanding of the cardiac cycle, knowledge of the appropriate technique, and a well-functioning stethoscope with a bell and a diaphragm. To utilize this basic tutorial, knowledge of cardiac anatomy, function and rhythm should be understood. Then, add patience and practice to develop your auscultation skills.
The Systematic Approach
When assessing the cardiac system, approach the patient and explain what you intend to do. Obtaining the patient's cooperation will ensure a more accurate assessment and clinical diagnosis. Position the patient comfortably in the supine, left lateral or sitting and leaning slightly forward aspect to examine.
First, observe the patient's breathing, chest rise and fall, and assess the pulses of the carotid arteries in the neck. Look for the carotid pulsations on the right and left side of the neck. Feel for the pulse. Listen with both the bell and diaphragm of the stethoscope. Note the difference of the sounds with the bell versus the diaphragm. An abnormal turbulent sound may be a bruit as this is the sound heard with blood flow through a partially occluded vessel. Heard best with the bell, which is used for low pitched sounds, be careful not to exert too much pressure on the artery, which will distort the sound and could also compromise blood flow to sensitive individuals. Carotids are evaluated as part of the screening process to assess a patient's risk for a stroke or vascular event.
Evaluate all peripheral pulses and compare for rate, rhythm and equality. Feel for the point of maximal impulse on the chest located at the fifth intercostal space just medial to the midclavicular line on the patient's left side. Note this location. If lower and more lateral, this may indicate an enlarged heart. Feel for a thrill or heave in the chest, which may indicate an abnormality such as an enlarged heart or ventricular hypertrophy.
Note the anatomic locations on the accompanying chest diagram where the intensity of the sound of closure of the four heart valves is best heard. They are noted as "A" aortic, "P" pulmonary, "T" tricuspid and "M" mitral. Normally, this is where these heart structures lie closest to the thoracic cage.
Begin auscultation at the apex of the heart in the fifth intercostal space to the left of the sternum. Listen with the bell of the stethoscope. Then, proceed to the tricuspid area and up the left sternal border to the second intercostal space of the pulmonic on the left and aortic on the right.
The first and second heart sounds, S1 and S2, differentiate the physiologic process of systole and diastole. Appreciate the sound of S1 in all areas before attempting to discern S2. Now, listen with the diaphragm of the stethoscope in reverse order and differentiate S1 and S2. The diaphragm is used to hear higher pitched sounds.
With the primarily passive blood flow through the tricuspid and mitral valves and the resulting increase in intraventricular pressure, which overcomes that within the atria, the valves close rapidly. This is the first heart sound of S1 and is best heard at the fifth intercostal space to the left of the sternum at the apex. As these valves close, the increased pressure causes the aortic and pulmonary valves to open and blood to flow through the large vessels into the circulation. The brief period of higher pressure in these vessels at the end of systole overcomes that in the ventricles and causes these valves to snap shut. This produces the second heart sound of S2 and diastole, which is heard best at the base of the heart, the area between the apex and the sternum.
While valve closure occurs somewhat simultaneously, it is important to remember the sounds change as a result of the pressure exerted in the heart chambers and the ultimate effects, both normal and abnormal, it has on the valves.
To put this in perspective, during normal function, the left side of the heart is a higher pressure system than the right. Because of this, the mitral valve closes slightly before the tricuspid in S1. And, the aortic valve closes slightly before the pulmonary valve in S2. Pathology in any of the valves can change the timing of closure causing a split sound, such as with atrial septal defect or a murmur most often associated with stenosis or damage.
While diastole is usually longer than systole, during periods of tachycardia it may be difficult to discern S1 from S2 and ventricular filling times will decrease. The sound heard while listening to the heart and palpating a radial pulse will be that of S1. When the pulse disappears, that sound will be S2.2 Listening to the sound of S1 in various areas of the heart and then repeating this same auscultation technique for S2 will help with recognizing normal before assessing for abnormal.
The third heart sound of S3 occurs slightly after S2, early in diastole and is best heard with the bell of the stethoscope in the mitral and tricuspid areas. While usually normal in those under age 35, it is often associated with heart failure, mitral regurgitation or pericarditis.3 This low frequency sound results from increased atrial pressure leading to increased flow rates.4 The "lub du bub" sound is often referenced to the same cadence as the word "Kentucky."
The fourth heart sound of S4 is heard slightly before S1 and is a presystolic sound in late diastole. Heard best over the apex of the heart, it is a low-pitched sound and associated with stiff ventricles from hypertrophy, ischemic or dilated cardiomyopathy. The cadence of the sound is similar to the inflections of the word "Tennessee."4
Systolic & Diastolic Murmurs
Murmurs are associated with the valves where they originate. Diastolic murmurs are associated with the tricuspid and mitral valves, while systolic are those originating from the aortic and pulmonary valves. With valvular disease, the blood flow becomes turbulent and can be heard in the period associated with systole or diastole. It should be noted where the murmur is best heard as it may be not be audible in other areas of the chest. Determine the timing, the sound and the discrete beginning and ending points. Time this against the S1 and S2 phases to determine if it is systolic or diastolic. Murmurs are often described as blowing, harsh or scratchy with a crescendo or decrescendo intensity of sound and are graded on a scale of I to VI.5
Systolic murmurs involve stenosis of the aortic or pulmonary valves or regurgitation of the mitral and tricuspid valves and occur between S1 and S2. The pathologic murmur of aortic stenosis, a systolic murmur, can be caused by a congenital defect, rheumatic heart disease or calcification of the valves. It is best heard over the aortic area, the second intercostal space to the right of the sternum and radiates to the right neck. This murmur has a harsh quality and, depending on the stage of aortic stenosis, can have an early or late peak sound quality associated with it. Symptoms common to aortic stenosis are angina, syncope and heart failure as the disease progresses.5
Diastolic murmurs involve stenosis of the mitral and tricuspid valves and can also be associated with regurgitation of the aortic or pulmonary valves. These occur between S2 and S1. Mitral stenosis has a higher incidence in females and is most often rheumatic in origin. This diastolic murmur is low-pitched and rumbling and heard best at the apex with the patient in the left lateral position. Often described as presystolic, this murmur ends right before S1 begins.
Accurate cardiac assessment is a technique that is learned over time with practice and patience. But, it is one vital component to the overall assessment of patients who seek the skill and expertise of the healthcare practitioner.
Medical Antiques Online. (1998-2011). Invention of the monoaural stethoscope. Retrieved Feb. 15, 2012 from the World Wide Web: http://www.antiquemed.com/
Cable, C. (2000, December 1). Physiology of murmurs. Retrieved Feb. 15, 2012 from the World Wide Web: http://www.wilkes.med.ucla.edu/Physiology.htm
Scholton, J. (1998, Sept. 1). Cardiac auscultation. Retrieved Feb. 15, 2012 from the World Wide Web: http://int-prop.lf2.cuni.cz/heart_sounds/h10/index.htm
Pinsky, L., & Wipf, J. (1999). Advanced physical diagnosis. Edition 1. Retrieved Feb. 15, 2012 from the World Wide Web: http://depts.washington.edu/physdx/heart/evid3.html%20
Cable, C. (1998, March 19). Basic approach to murmurs. Retrieved Feb. 15, 2012 from the World Wide Web: http://www.uni-duesseldorf.de/MedFak/Herz-Kreislauf-Physiologie/lehre/sounds/html/murmur_overview.html
Sue Durkin is clinical nurse specialist in the level I trauma center at Advocate Good Samaritan Hospital, Downers Grove, IL.