The apical pulse is a direct measurement of the heart’s function, reflecting the rhythmic contraction of the left ventricle. Unlike peripheral pulses felt at sites like the wrist, this measurement involves listening directly over the heart. It is sometimes called the point of maximal impulse (PMI) or the apex beat, as it occurs at the lower, pointed end of the heart.
Precise Location and Anatomical Landmarks
The location for measuring the apical pulse is situated over the apex of the heart, resting against the chest wall. For most adults, this point is found on the left side of the chest at the fifth intercostal space (ICS), the gap between the fifth and sixth ribs. To precisely locate this spot, an imaginary vertical line, the mid-clavicular line (MCL), is drawn downward from the midpoint of the collarbone. The apical pulse is found where this line intersects the fifth intercostal space.
Finding the correct intercostal space involves locating the sternal angle, the ridge where the manubrium meets the body of the sternum, as the second rib attaches directly below this point. The anatomical location differs slightly in infants and young children due to the smaller size and different positioning of their hearts. In this younger population, the apex beat is generally located one rib space higher, at the fourth intercostal space at the left mid-clavicular line.
When and Why the Apical Pulse is Used
Measuring the apical pulse is preferred because it offers the most accurate, non-invasive assessment of the heart rate and rhythm. Unlike a peripheral pulse, listening directly to the heart allows for the detection of subtle irregularities that might not travel effectively to the radial pulse. The apical pulse is the standard method for assessing heart rate in infants and young children, whose smaller and faster pulses are difficult to palpate at the wrist.
This method is selected when a patient has a known or suspected cardiac irregularity, such as an arrhythmia. If the heart is beating inefficiently, the radial pulse rate may be lower than the true heart rate counted at the apex, a difference known as a pulse deficit. Checking the apical pulse is required for patients taking certain heart medications, such as digoxin, where a precise heart rate is needed before administering the drug. If a peripheral pulse is weak, irregular, or cannot be felt due to conditions like poor circulation or obesity, the apical site provides a reliable alternative.
Step-by-Step Measurement Technique
The apical pulse is measured using a stethoscope, a process called auscultation, which allows for direct listening to the heart sounds. Equipment includes the stethoscope and a watch or clock with a second hand or digital timer. The patient should be positioned either lying flat (supine) or sitting up, and may be asked to turn slightly onto their left side to bring the heart closer to the chest wall.
After locating the fifth intercostal space and mid-clavicular line, the healthcare provider places the diaphragm or bell of the stethoscope firmly against the bare skin. The heart sounds are heard as a distinct “lub-dub,” and each complete “lub-dub” sound counts as a single heartbeat. Listen carefully and note the rate, rhythm, and quality of these sounds.
The most accurate measurement requires counting the beats for a full 60 seconds, which is especially important for patients with an irregular heart rhythm or in young children. Counting for the entire minute ensures that subtle variations in rhythm are not missed. If the apical pulse is being measured concurrently with a peripheral pulse to check for a pulse deficit, both rates must be counted simultaneously for the full minute by two separate people.