The heart is situated in the thoracic cavity between the lungs in the mediastinum and above the diaphragm. About two thirds of the heart lies within the left side of the ribs cage, with the other side as it crosses the sternum. Most of the anterior cardiac surface is occupied by the right ventricle. Part of the right atrium and left ventricle also faces anteriorly, whereas the left atrium lies primarily in a posterior position.
The heart is positioned in the thorax like a trapezoid:
Vertically along the right sternal border (RSB) from the second to the fifths rib
Horizontally (long side) from the lower right sternum to the fifth rib at the left midclavicular line (LMCL)
Diagonally from the left sternal border (LSB) at the second rib to the LMCL at the fifth rib
Horizontally (short side) from the RSB and LSB at the second intercostals space (ICS)
The base of the heart is actually the top of the trapezoid or the pulmonic and aortic areas. The apex is located at the left midclavicular line and fifth intercostals space or mitral area. The heart of the infant is more horizontally positioned; therefore the apex is higher (third to fourth intercostals space) and to the left of the midclavicular line. The apical impulse, or point of maximum impulse (PMI) (area where the heartbeat is loudest), is normally located at the apex.
Inspection. When the chest is examined, any obvious bulging is noted, especially on the left side, which may indicate cardiac enlargement. This is best done by observing the child sitting in a semi-Fowler position and looking at the anterior chest wall from an angle, comparing both sides of the rib cage to each other. Normally they should be symmetric. In children with thin chest walls, the PMI, or apical pulse, is sometimes apparent as a pulsation. Noting the location of the impulse may give some indication of the size and positioning of the heart, especially if it deviates from the expected apical site.
Since comprehensive evaluation of cardiac function is not limited to the heart, other findings are also considered, such as presence of all pulses (especially the femoral pulses), distended neck veins, clubbing pressure, and respiratory status.
Palpation. Palpation is useful in determining the size of the heart by feeling for the PMI, which ordinarily corresponds to the apex. The apex is usually at a lower interspace and more lateral in a child with cardiac enlargement. The apex is felt by placing the fingertips or the palmar aspect of the fingers and the hand at the fifth intercostals space and left midclavicular line.
When the PMI is felt for, the presence of vibratory thrills and pericardial friction rubs is noted. Thrills are palpable vibrations most commonly produced by the flow of blood from one chamber of the heart to another through a narrowed or abnormal opening, such as a stenotic valve or septal defect. They are best felt with the ball of the hand (palmar surface at the base of the fingers) and during expiration. Thrills feel similar to the placing of ones hand on a purring cat.
Pericardial friction rubs are scratchy, high pitches grating sounds, similar to pleural friction rubs, except that they are not affected by changes in respiration. This is useful clue in differentiating the two rubs, because the pleural rub will cease if the child holds his breath, but the pericardial rub will not. Both thrills and rubs are abnormal and must be reported for further evaluation.
Percussion. Percussion is used mainly to determine the size of the heart by outlining its borders. Dullness is normally heard over the left area of the heart and partially over the right, although dullness on the right side descents past the border of the heart to the nearby liver. The most important area of percussion is dullness along the lower sternal border to the left midclavicular line. This finding is often referred to as left border of cardiac dullness (LCBD). Deviation from the expected findings may indicate cardiac enlargement or displacement and warrants further study.
Auscultation. Auscultation involves listening for heart sounds with the stethoscope, similar to the procedure used in assessing breath sounds.
Origin of heart sounds. The heart sounds are produced by the opening and closing of the valves and the vibration of blood against the walls of the heart and vessels. Normally two sounds – S1 and S2 are heard, which correspond respectively to the familiar “lub dub” often used to describe the sounds. S1 is caused by the closure of the tricuspid and mitral valves (sometimes called the atrioventricular valves). Right ventricular contraction follows tricuspid valve closure, and left ventricular contraction follows mitral valve closure. The contractions (systole) occur almost simultaneously, although the mitral valve (left side) closes slightly before the tricuspid valve (right side). Normally this split of the sounds is so close that it is not audible, except occasionally at the apex of the heart.
S2 is the result of the closure of the pulmonic and aortic valves (sometimes called semilunar valves). Aortic valve closing (left side) occurs slightly before pulmonic valve closing (right side). The flow of blood into the aorta and pulmonary artery occurs following closure of their respective valves. The interval between S2 and S1 is diastole, or relaxation, of the heart. Normally the split of the two sounds in S2 is distinguishable and widens during inspiration, since inspiration prolongs right ventricular filling and delays pulmonic valve closure. “Physiologic splitting: is a significant normal finding that should be elicited. “Fixed splitting,” in which the split in S2 does not change during inspiration, is an important diagnostic sign of atrial septal defect.
The illustration shows the approximate anatomic position of the valves within the heart chambers and the auscultatory sites. The auscultatory sites, located in the direction of the blood flow through the valves, correspond to the area where the sounds are heard best.
Two other heart sounds – S3 and S4 – may be produced. S3 is the result of vibrations produced during ventricular filling. It is normally heard only in some children and young adults, but it is considered abnormal in older individuals. S4 is caused by the recoil of vibrations between the atria and ventricles following atrial contraction at the end of diastole. It is rarely heard as a normal heart sound and indicates the need for the further cardiac evaluation.
Another important category of heart sounds is murmurs, which are produced by the vibrations within the heart chambers or in the major arteries from the back and forth flow of blood. Murmurs are classified as:
- Innocent, occurring in individuals with no anatomic or physiologic abnormality
- Functional, found in individuals with no anatomic cardiac defect but with a physiologic abnormality such as anemia
- Organic, occurring in individuals with a cardiac defect with ot without a physiologic abnormality
The description and classification of murmurs are skills that require considerable practice and training. In general, the nurse should be able to recognize murmurs as distinct swishing sounds that occur in addition to the normal heart sounds and should record the following:
1/ Location of the area of the heart where the murmurs is heard best.
2/ Time of the occurrence of the murmur within the S1S2 cycle
3/ Intensity – evalution in relationship to the childs position
4/ Loudness – estimation
The usual subjective method of grading the loudness or intensity oa a murmur is listed table.
The following guidelines should be used in distinguishing between innocent and organic murmurs. Innocent murmurs generally are:
- Systolic, that is, they occur with or after S1
- Of short duration and have no transmission to other areas of the heart
- Grade III or less in intensity and do not increase over time
- Usually loudest in the pulmonic area (second or third intercostals space along the left sternal border)
- Variable in relationship to position, respiration, and activity (e.g., audible in the supine position, respiration, and activity position; may be louder with exercise, fever, anxiety, or anemia)
- Not associated with any physical signs of cardiac disease
- Usually of a low-pitched, musical, or groaning quality
There are a number of other abnormal sounds, such as ejection clicks, snaps, gallops, and hums. It is beyond the scope of this discussion to elaborate on such adventitious heart sounds. The best approach is to become familiar with normal heart sounds and to refer any questionable heart sound to a physician for further evaluation.
Grading of the intensity of heart murmurs (Table 1):
|I||Very faint, frequently not heard if child sits up|
|II||Usually readily heard, slightly louder than grade I, audible in all positions|
|III||Loud, but not accompanied by a thrill|
|IV||Loud, accompanied by a thrill|
|V||Loud enough to be heard with the stethoscope barely on the chest, accompanied by a thrill|
|VI||Loud enough to be heard with the stethoscope not touching the chest; often heard with the human ear close to the chest, accompanied by a thrill|
Differentiating normal heart sounds. In referring to Fig 1, it is apparent that normally S1 is louder at the apex of the heart in the mitral and tricuspid area and that S2 is louder near the base of the heart in the pulmonic and aortic area. Each sound is auscultated by inching down the chest in the sequence outlined in table 2. If there is difficulty in deciding which sound is S1 or S2, especially when the rate is rapid, the carotid pulse should be simultaneously palpated with the index and middle finger while the heart sounds are auscultated. S1 is synchronous with the carotid pulse. In addition to the areas listed in Table2, the following areas should be auscultated for sounds, such as murmurs, which may radiate to these regions: the sternoclavicular area above the clavicles and manubrium, along the sternal border, along the left midaxillary line, and below the scapulae.
The heart is ausculated with the child in at least two positions, sitting and reclining. If adventitious sounds are detected, they are further evaluated with the child standing, sitting and leaning forward, and lying on his left side. For example, atrial sounds such as S4 are heard best with the person in a recumbent position and usually fade if the person sits or stands.
Sequence of auscultating heart sounds (Table 2):
|Auscultatory site||Chest location||Characteristics of heart sounds|
|Aortic area||Second right intercostals space close to sternum||S2 heard louder than S1; aortic closure heard loudest|
|Pulmonic area||Second left intercostals space close to sternum||Splitting of S2 heard best, normally widens on inspiration; pulmonic closure heard best|
|Erb point||Second and third left intercostals space close to sternum||Frequent site of innocent murmurs and those of aortic or pulmonic origin|
|Tricuspid area||Fifth right and left intercostals space close to sternum||S1 heard as louder sound preceding S2 (S1 synchronous with carotid pulse)|
|Mitral or apical area||Fifth intercostals space, left midclavicular space and lateral to left midclavicular line in infants||S1 heard loudest; splitting of S1 may be audible because mitral closure is louder than tricuspid closure
S3 heard best at beginning of expiration with child in recumbent or left side-lying position, occurs immediately after S2, sounds like word “Ken-tuc-ky”
S1 S2 S3
S4 heard best during expiration with child in recumbent position (left sidelying position decreases sound), occurs immediately before S1, sounds like word “Ten-nes-see”
S4 S1 S2
Heart sounds are evaluated for:
- Quality, which should be clear and distinct, not muffled, diffuse, or distant
- Intensity, especially in relation to location or auscultatory site
- Rate, which should be the same as the radial pulse
- Rhythm, which should be regular and even
A particular arrhythmia that occurs normally in many children is sinus arrhythmia, in which the heart rate increases with inspiration and decreases with expiration. This can be differentiated from a truly abnormal arrhythmia by having the child holds his breath. In sinus arrhythmia, cessation of breathing causes the heart rate to remain steady. Table 3 lists variations in patterns of heart rate or pulse. Like respiratory rate, heart rate is always evaluated in relation to the cilds general physical status. For example, the pulse rate is usually increased by 8 to 10 beats per minute for each degree Fahrenheit elevation in temperature. Athletic children occasionally have lowred heart rates that may even reach rates suggestive of bradycardia (below 60 beats per minute) but that represent a highly developed and efficient heart muscle.
Normal Heart Rates for Infants and Children
|Age||Resting (awake)||Resting (sleeping)||Exercise (fever)|
|Newborn||100-180||80-160||Up to 220|
|1 week to 3 month||100-220||80-200||Up to 220|
|3 month to 2 years||80-150||70-120||Up to 200|
|2 years to 10 years||70-110||60-90||Up to 200|
|10 years to adult||55-90||50-90||Up to 200|