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Assessing heart sounds


 

ACUTE CARE FOCUS

HANDS-ON HELP:
Assessing heart sounds

SALLIE BEATTIE DULAK, RN, MSN

The author, a member of the RN editorial board, is an advanced practice nurse and consultant in cardiovascular disease in Columbia, MO.

Listening to heart sounds is an art that takes practice to perfect. But with a solid understanding of the cardiac events that produce them and a systematic approach to your assessment, you can quickly gain expertise.

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You of course know that the valves snapping shut make the two basic heart sounds often called "lub-dub." As you listen to a patient's chest, you want to hear a crisp "lub" followed by an equally crisp "dub," with a brief moment of silence in between each lub-dub.

The first heart sound, or lub, is S1. It's produced when the tricuspid and mitral valves simultaneously close. S1 marks the onset of systole, or ventricular contraction.

The simultaneous closing of the pulmonic and aortic valves produces S2, or dub. S2 marks the end of systole. The brief silent period between S2 and S1 represents diastole, or ventricular relaxation. During diastole the ventricles fill with blood coming from the atria.

As you assess a patient's heart sounds, any new whoosh, plop, or an extra lub or dub may indicate a change in the patient's condition and should prompt you to contact the physician.

These tips will help you get started

Before you begin, warm up the diaphragm end of your stethoscope in your hands for the patient's comfort. Then, expose the chest.

Never try to listen through clothing, as scratchy noises will obscure heart sounds. A hairy chest can also create noise. Moistening chest hair with a wet cloth will help relax the hair and reduce the noise.

Place the diaphragm directly on the patient's skin, and press firmly to hear high-pitched sounds, such as S1 and S2. Use the bell to hear low-pitched sounds, which are often abnormal. But lay the bell gently on the chest; pressing it firmly will make it function like a diaphragm.

Newer stethoscopes build the bell and diaphragm into one piece. You apply more or less pressure to get the function you want.

Before assessing each heart sound, always take a minute to listen to the timing, rhythm, and rate of your patient's heart. The rate should normally be between 60 and 100 beats per minute, with a regular rhythm.

Then assess the heart sounds at each of these five auscultatory sites: the aortic, pulmonic, Erb's point, tricuspid, and mitral areas. (See the "Locating the assessment points" image.) Begin either upward from the apex or downward from the base, but be consistent.

For best results, listen while the patient is sitting up, then with him supine and the head of the bed raised no more than 30 – 45 degrees, and again while he's in the left side-lying position.

Learn to distinguish the different sounds

S1 is normally softer than S2, except over the apex, where S1 is louder. Since S1 is in sync with the carotid pulse, palpating the pulse helps to distinguish lub from dub.

If you hear a quick "lu-lub," S1 may be split, meaning that the mitral valve closed just before the tricuspid. A split may be normal, but it can also occur in the presence of a bundle-branch block.

If you hear a "du-dub," it means S2 is split, which occurs when the aortic valve closes before the pulmonic valve. A split S2 is often normal and heard on inspiration.

The ventricular gallop sounds like Ken-tuc-ky

A ventricular gallop is produced when a third heart sound, called S3, occurs early in diastole. S3 is heard as a low-pitched "plop" right after dub, when there should be silence. The cadence created by S3 resembles the word Ken-tuc-ky, where S1 represents "Ken," S2 carries the accent on "tuc," and S3 is the "ky."

While a ventricular gallop may be normal in children and young adults, it is abnormal in patients over the age of 30. In adults, the sudden appearance of an S3 may indicate ischemia or heart failure. The S3 is caused by the vibration of non-compliant ventricles as they resist the rapid filling of the early phase of diastole.

S3 is heard best over the apex, using the bell of the stethoscope. It helps to have the patient hold his breath for a moment as you listen. It also helps to have him supine or in the left side-lying position.

The atrial gallop sounds like Ten-nes-see

An atrial gallop is produced by a fourth heart sound, called S4. It's another low-pitched sound heard best over the apex. However, S4 is heard late in diastole, just prior to S1. The presence of S4 creates a rhythm that sounds like the word Ten-nes-see. Here, S4 represents the "Ten," S1 represents "nes," and S2 carries the accent on the syllable "see."

S4 is normal in infants and children and common in the elderly. In adults, however, S4 often occurs after an MI. S4 is also linked to aortic stenosis, myocardial ischemia, heart failure, and hypertension. It's caused when stiff and over-distended ventricles are forced to accept blood from the atria during late diastole, when the atria exert their final squeeze, called the atrial kick.

Like the third heart sound, S4 is heard best when you use the bell of the stethoscope and the patient is in a supine position while holding his breath.

A heart murmur could spell trouble

Murmurs are either high- or low-pitched sounds that usually last longer than normal heart sounds. They're most often caused by a stiffened valve that leaves only a narrow passage for blood to get through, or by a weak, floppy valve that allows blood to backflow. A murmur can also be caused by blood flowing turbulently through a hole in the septal wall.

In any case, a murmur is always the result of a pathologic event or condition, such as ischemia, infection, drug toxicity, or a disease that's inherited or acquired. While a preexisting murmur may pose no threat, the sudden onset of a murmur or a change in an existing murmur may signal impending heart failure, shock, or the rupture of a papillary muscle.

A skilled clinician can diagnose the cause of a murmur by pinpointing its location and timing in the cardiac cycle. It's important to listen to and document the quality of a murmur, the timing, where you hear it the loudest, and its intensity.

The quality of a murmur may be described as blowing, harsh, raspy, rumbling, vibrating, or machinelike. The timing refers to where in the cardiac cycle you hear the sound. A systolic murmur, for example, may sound like "lush-dub," the murmur occurring between S1 and S2. It's caused by mitral or tricuspid insufficiency (regurgitation), or aortic or pulmonic stenosis.

A diastolic murmur can sound like "lub-dush," as the murmur sound is heard between S2 and the next S1. Diastolic murmurs are caused by either mitral or tricuspid valve stenosis or aortic or pulmonic valve insufficiency.

The point where a murmur is heard loudest can help pin down the type. For instance, a murmur caused by mitral insufficiency may be heard loudest at the apex, while pulmonic stenosis is heard loudest at the second intercostal space, left sternal border.

Grade the intensity of a murmur on a scale from one to six, using Roman numerals as a fraction of six. For instance, grade I (I/VI) is a very faint murmur that may be barely audible. Grade II/VI is a murmur that's faint but easily heard by a trained ear.

Grade III/VI is a murmur that's moderately loud, or about equal to the intensity of normal heart sounds. Grade IV/VI is a loud murmur and grade V/VI is a very loud murmur that's heard with the stethoscope barely touching the chest. Grade VI/VI is an extremely loud murmur that may be heard with the stethoscope just over—but not in contact with—the chest.

As you perfect your skills, keep in mind that it's more important to report and document any abnormal sound you hear than to split hairs over the grade of a murmur.

SOURCES

1. Diepenbrock, N. H. (2004). Quick reference to critical care (2nd ed.), (pp. 102 – 106). Philadelphia: Lippincott Williams & Wilkins.

2. Messner, R., & Wolfe, S. (1997). RN's pocket assessment guide (pp. 89 – 104). Montvale, NJ: Medical Economics.



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Helen Lippman, ed. Sally Beattie Dulak. Hands-on help: Assessing heart sounds. RN Aug. 1, 2004;67:24ac1.

Published in RN Magazine.

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