The apical pulse, also known as the Point of Maximal Impulse (PMI), is a specific beat felt or heard on the chest wall that represents the heart’s activity. This impulse occurs when the apex of the left ventricle contracts and strikes the inside of the thoracic cavity. It is considered the most accurate, non-invasive indicator of the heart rate and rhythm.
Finding the Anatomical Location
Locating the apical pulse requires identifying specific anatomical landmarks on the torso. To find the correct spot, one must first locate the sternal notch and then count down the ribs and the spaces between them, known as the intercostal spaces (ICS).
The apical pulse is consistently found in the fifth intercostal space, situated between the fifth and sixth ribs. The second necessary landmark is the midclavicular line (MCL), which is an imaginary vertical line that drops directly down from the middle of the clavicle.
The apical pulse is precisely located at the intersection of the fifth intercostal space and the midclavicular line. This location marks where the apex of the heart is closest to the anterior chest wall in most healthy adults. In infants and young children, the PMI is typically found higher, often at the fourth intercostal space, and slightly more lateral.
Proper Technique for Measurement
Once the location has been identified, measuring the apical pulse rate requires the use of a stethoscope, a procedure known as auscultation. The patient should be positioned comfortably, ideally in a supine or semi-Fowler’s position, to ensure the heart is situated normally within the chest cavity. Applying the diaphragm of the stethoscope directly over the PMI location allows for clear sound transmission.
The listener will focus on identifying the characteristic “lub-dub” sounds, which represent the closure of the heart valves. Each complete “lub-dub” sequence counts as one full heartbeat.
For the highest degree of accuracy, the heart rate should be counted for a full 60 seconds without interruption. Counting for a shorter duration and then multiplying can introduce errors, especially if the rhythm is irregular. This direct auscultation provides the actual ventricular contraction rate.
Clinical Use and Significance
Measuring the apical pulse is a standard procedure in clinical settings because it provides a direct assessment of the heart’s function. This measurement is often preferred in situations where peripheral pulses are difficult to feel. Conditions like shock, severe dehydration, or peripheral vascular disease can cause weak or thready peripheral pulses that do not accurately reflect the central heart rate.
The apical pulse is mandatory when assessing a patient with a known or suspected irregular heart rhythm. When the heart beats irregularly, not every ventricular contraction generates a pulse wave strong enough to be felt at a peripheral site. By listening directly over the heart, every single beat is counted, ensuring a true and accurate heart rate.
Clinicians also use the apical pulse to check for a condition known as a pulse deficit. A pulse deficit is calculated by simultaneously comparing the apical pulse rate with a peripheral pulse rate, such as the radial pulse, counted by two different practitioners. If the apical rate is higher than the radial rate, a pulse deficit exists, indicating that some heart contractions are too weak to produce a palpable peripheral wave. This difference can be an important diagnostic indicator of cardiac function.