The apical pulse, also known as the point of maximal impulse (PMI) or apex beat, provides a direct measurement of the heart’s activity. It represents the pulsation felt or heard over the apex of the left ventricle as it contracts and pumps blood. This measurement offers a highly accurate assessment of heart rate and rhythm, making it a preferred method when a precise understanding of cardiac function is needed. Unlike other pulse points that rely on arterial pressure waves, the apical pulse allows for direct auscultation of the heart’s sounds.
Locating the Apical Pulse
To locate the apical pulse in an adult, place the stethoscope on the left side of the chest at the fifth intercostal space along the midclavicular line. Intercostal spaces are the areas between the ribs. The midclavicular line is an imaginary vertical line extending straight down from the midpoint of the clavicle.
To identify this spot, locate the clavicle. Imagine a line running vertically down its middle. Find the sternal notch, the soft dip at the top of the breastbone. Slide your finger down from the sternal notch until you feel a bony ridge, known as the Angle of Louis or sternal angle. This angle is where the second rib attaches to the sternum.
From the Angle of Louis, slide your finger to the left side of the chest, moving over the second rib and into the second intercostal space. Continue to move your fingers downward, counting each rib and the space below it until you reach the fifth intercostal space. Once you have found the fifth intercostal space on the left side, move your fingers laterally until they align with the imaginary midclavicular line. If finding the pulsation is difficult, leaning slightly to the left can help bring the heart closer to the chest wall.
Understanding the Apical Pulse and Its Significance
The apical pulse offers a direct assessment of the heart’s function because it involves listening to the actual sounds of the heart contracting and pumping blood. This differs from peripheral pulses, such as the radial pulse, which reflect the pressure wave of blood moving through arteries. The apical pulse provides more detailed information about the heart’s rate, rhythm, strength, and overall quality of contractions.
Taking an apical pulse is beneficial in specific situations. It is preferred for infants and young children, up to five years of age, as their peripheral pulses can be challenging to locate and count. The apical pulse is also valuable when peripheral pulses are weak, irregular, or difficult to find, such as in individuals with obesity or certain cardiovascular conditions. Healthcare providers use it to assess for heart rhythm irregularities or when a patient is taking cardiac medications like digoxin.
When listening to the apical pulse, you will hear the characteristic “lub-dub” sounds. The “lub” sound, known as S1, occurs when the mitral and tricuspid valves close at the beginning of the heart’s contraction phase (systole). The “dub” sound, or S2, follows when the aortic and pulmonary valves close at the end of the contraction phase and the beginning of the relaxation phase (diastole). Each “lub-dub” sequence represents one complete heartbeat or cardiac cycle. Listening for a full minute is recommended to ensure an accurate count and to detect any irregularities in rhythm.