Measuring a person’s pulse assesses cardiovascular health by counting heartbeats per minute. While the peripheral pulse, often felt at the wrist, is the most common method, it is not always the most accurate reflection of heart function. The apical pulse, measured directly over the heart, offers a more precise evaluation of the heart’s true rhythm and rate. This direct measurement is useful when a patient’s peripheral circulation is compromised or when deeper insight into cardiac performance is necessary.
Defining the Apical Pulse and Its Importance
The apical pulse represents the rhythmic contractions of the left ventricle. It is a direct measure of the heart’s mechanical activity and is heard, rather than felt, using a stethoscope over the chest wall. This location is known as the Point of Maximal Impulse (PMI) because the heart’s beat is most clearly transmitted here.
The apical measurement is the gold standard for determining heart rate accuracy, especially in individuals with irregular heart rhythms (arrhythmias). It is measured when patients take certain cardiac medications, such as digoxin or beta-blockers, to gauge the medication’s effect and ensure safety before administration. It is also the preferred site for measuring the pulse in infants and young children, whose weak peripheral pulses make a radial check difficult.
A comparison of the apical pulse with a peripheral pulse, like the radial pulse, can reveal a condition called a pulse deficit. This occurs when the heart contracts but the beat is too weak to create a palpable wave that reaches the wrist or other distant points. In such cases, the apical rate will be higher than the radial rate, indicating that some heartbeats are ineffective at circulating blood throughout the body.
Identifying the Point of Maximal Impulse
Locating the apical pulse requires identifying specific anatomical landmarks on the chest. In most adults, the PMI is found at the fifth intercostal space (ICS) near the midclavicular line (MCL). The midclavicular line is an imaginary vertical line drawn downward from the midpoint of the collarbone.
To find the fifth intercostal space, first locate the sternal angle, a prominent ridge where the manubrium and the body of the sternum join, which corresponds to the second rib. Running a finger laterally from this angle locates the second intercostal space. Counting downward, the third, fourth, and fifth intercostal spaces can be found.
The apical pulse is situated where the midclavicular line intersects with this fifth intercostal space on the left side of the chest. Positioning the patient is also important for an accurate reading. Having the person lie supine (flat on their back) or slightly elevated often allows the chest wall to be assessed more easily.
Step-by-Step Procedure for Auscultation
Once the PMI is located, the process of listening to the heart rate, known as auscultation, can begin. Use a stethoscope, typically the diaphragm side, which picks up higher-pitched sounds like the heart’s “lub-dub.” The patient should be quiet and comfortable in the supine or sitting position.
The diaphragm is placed firmly against the chest wall at the PMI, ensuring direct contact with the skin and avoiding placement over clothing. Each “lub-dub” sound represents one complete heartbeat. The count must be performed accurately for a full 60 seconds to ensure the most reliable measurement of the rate and to detect any irregularities in the rhythm.
If assessing a pulse deficit, a second person is needed to simultaneously count the radial pulse for the same 60 seconds. This concurrent counting ensures that both the heart’s mechanical rate and the peripheral circulation rate are measured over the exact same period.
Interpreting Apical Pulse Findings
The measured apical rate and rhythm provide direct insight into cardiac function. For a resting adult, a normal apical pulse rate typically falls between 60 and 100 beats per minute (bpm). Rates outside of this range are classified as bradycardia (slow, below 60 bpm) or tachycardia (fast, above 100 bpm).
Pediatric ranges are notably higher than adult ranges, with heart rates gradually slowing as a child ages toward adolescence. Beyond the rate, listening to the apical pulse also reveals the heart’s rhythm, which should be regular and steady. An irregular rhythm suggests an abnormality that may require further medical investigation.
The most significant interpretive finding is the pulse deficit, the difference between the apical rate and the radial rate. If the apical pulse is 85 bpm and the radial pulse is 70 bpm, the pulse deficit is 15. This difference signifies that 15 heartbeats per minute were not forceful enough to produce a palpable pulse at the wrist, which may indicate conditions like atrial fibrillation or heart failure.