Vol. 9 Issue 16 Page 31
Lub dub and so much more making sense of the rhythmic beating of the adult heart
Lub, dub, lub dub, bup, click, swish, rumble. Over the course of one’s lifespan, the heart with its power and rhythmicity will resonate at least the lub dub cycle continuously propelling blood to a normal, healthy person. Heart sounds and their interpretation is a ubiquitous language and skill that has gained much sophistication since its first descriptions by Joseph Skoda, MD, in the 1800s.1
Today, there are many diagnostic tools for cardiac assessment but none take the place of ausculatory methods. They can not only point you in the right direction for identifying a problem, but provide a great “hands-on” practical application for establishing a relationship with your patient.
The Cardiac Cycle
Heart sounds are vibratory sounds heard anywhere in the cardiac cycle and its timing is important in determining the etiology of extra and abnormal heart sounds. Fig. 1: Heart Sounds & The Cardiac Cycle depicts this relationship.
While nursing school certainly taught you the basics of listening to the heart, where to listen for specific sounds requires a higher level skill.
Fig. 2: Auscultatory Sites depicts the various anatomical locations for listening to heart sounds. Stand on the patient’s right side to begin exam. Listen to the auscultory sites in sequence: for example, lower left sternal border (LLSB), apex, Erb’s point, right base, left base using a stethoscope with a diaphragm and a bell.1
When auscultating heart sounds, it is important to identify the characteristics of each sound and describe them when charting your findings.
1.Faint but barely audible
2.Faint but able to hear
3.Moderately loud but without thrust or thrill
4.Loud with thrust or thrill
5.Very loud with stethoscope tilted on chest wall and associated thrust or thrill
6.Loud with thrust or thrill and stethoscope off chest wall
Intensity may be subjective depending on the experience of the listener. The transmission of sounds may be affected by body habitus, fluid, tissue.2
How Sounds Are Produced
A normal, functioning heart produces two sounds: lub and dub signifying S1 and S2. “Lub” or S1 occurs during systole when the mitral (M1) and tricuspid (T1) valves close and “dub” or S2 occurs when the aortic (A2) and pulmonic (P2) valves close at the conclusion of ventricular systole. The period between S1 and S2 is systole and the period between S2 and the beginning of the next S1 is diastole. S1 is heard at the apex, right or left base or LLSB.
S2 produces one sound heard at right base, LLSB or apex. During S2 a physiologic split may be audible at the left base on inspiration, which is normal.
S1 and S2 are high frequency heart sounds heard with the diaphragm of the stethoscope.
S3 and S4 are ventricular diastolic filling sounds, low frequency and heard over the mitral area with the bell of the stethoscope. These vibratory sounds are a result of changes within the wall motion of the left ventricle in response to rapid filling. High volume states may produce an S3 because of the increased cardiac output. S3 can be abnormal in valvular heart disease such as mitral regurgitation and congestive heart failure in people older than 40 with a dilated left ventricle.2
S3 is heard after S2 but before the next S1. Certain maneuvers that can enhance the sound of S3 are coughing or exercise. A left lateral recumbent position may intensify S3.
A physiologic S3 and an abnormal S3 are only different in terms of disease states present and the age of the person. A ventricular gallop rhythm sequence of S1 S2 S3 is often audible with mitral regurgitation and CHF.
Erickson cites the cadence for auscultating an S1 S2 S3 sequence would sound like lub dub bup.1
S4 occurs during late diastole. It precedes S1, has a thud-like quality and is auscultated with the bell during expiration over the apex.2
An S4 is always abnormal except in well-trained athletes. It is associated with a multitude of problems including hypertension, cardiomyopathies, ischemic heart disease, myocardial infarction, sudden mitral regurgitation anemia and hyperthyroid states.2
Erickson cites the cadence for auscultating an S4 S1 S2 sequence would sound like bub lub dub.1
Murmurs are a series of vibratory sounds caused by turbulent blood flow through a stenotic valve or as a result of an incompetent valve producing regurgitant flow from a high-pressure chamber to a low-pressure chamber. These sounds are heard during systole, diastole or both phases of the cardiac cycle.
Systolic murmurs begin after S1 and can have a harsh or blowing quality. Systolic ejection murmurs (SEM) are typically harsh and grating and occur between S1 with brief interval and the onset of S2. These murmurs are associated with such conditions as aortic stenosis, atrial septal defects and innocent murmurs. The murmur of aortic stenosis is heard in the right upper border and may radiate to the neck. More than half of all people older than 50 have SEMs.2
Systolic regurgitant murmurs are auscultated with S1 and last throughout systole (pansystolic or holosystolic). They are caused by blood flowing from high-to low-pressure chambers as a result of incompetent valves or defects in the septum such as ventricular septal defects, mitral regurgitation or tricuspid regurgitation. This distinctive blowing quality sound is heard at the apex and can radiate to the left axilla.
Diastolic murmurs are audible between S2 and the next S1 and usually are considered pathologic. They may be a result of incompetent aortic and pulmonic valves. Also, turbulent flow across a stenotic mitral or tricuspid valve will produce a diastolic murmur. Diastolic murmurs include: aortic regurgitation, pulmonic regurgitation, mitral and tricuspid stenosis.
The murmur of aortic insufficiency is heard over the aortic and pulmonic areas, Erb’s and mitral areas. It is high pitched and blowing and heard best with the diaphragm. Mitral stenosis, heard at the apex, is low pitched and has a rumbling quality. It begins with an opening snap sound and is heard best with the bell. Some people have systolic and diastolic murmurs.
Factors Affecting Sounds
Certain physiologic factors can affect heart sounds, such as exercise, hyperthermia, anemia, hypovolemia, pregnancy, low output states, shock and myocardial infarction.
Pericardial friction rub: caused by inflammation of the lining of the pericardial surfaces which creates a short scratching, grating sound heard mostly along the LLSB with the diaphragm and louder with inspiration. The patient should be sitting upright and leaning forward with their breath expelled for detection of a pericardial friction rub. This sound may be common in postop open heart surgery patients.
Prosthetic valve sounds: produced by mechanical or biological prosthetic valves. The most common mechanical valve, the St. Jude metal valve, produces a prominent closing sound or click. Also, a midsystolic ejection murmur is normal. In the aortic position, the sound is heard at the right base or aortic area. The mitral valve prosthesis is auscultated best over the apex.
Biological tissue valves have specific sounds depending on the position. Tissue aortic valves have a high-pitched closing sound and midsystolic murmur along the LLSB. The prosthetic mitral valve has high-pitched opening and closing sounds as well as a systolic murmur or diastolic rumble heard at the apex.1
Various sources are available with audio tapes and CDs that greatly enhance the ability to discern the various sounds which can be incorporated into your daily physical assessments. The more you listen and learn, the easier it will be to recognize whether bub lub dub, click, thud or rumble needs further investigation.
1. Erickson, B. (2003). Heart sounds and murmurs across the lifespan (4th ed.). St. Louis: Mosby Inc.
2. Moshier, A.L., & Caplin, M. (Eds.). (2006). Auscultation skills: Breath and heart sounds (3rd ed.). Philadelphia: Lippincott Williams & Wilkins.
Lisa A. Papp is in collaborative private practice with the Surgical Group of South Jersey.
The following links give sound examples of different heart sounds.