The heart is a powerful, cone-shaped muscle that constantly pumps blood throughout the body. Medical professionals focus on the heart’s most inferior and pointed part, the apex, to understand its function and assess its health. The apex’s location is a fundamental landmark in the chest cavity, helping to comprehend the heart’s complex orientation.
Anatomy of the Heart’s Apex
The apex is the rounded tip of the heart, formed primarily by the muscular wall of the left ventricle. It is positioned opposite the “base,” the broad, upper portion where great blood vessels enter and exit. Unlike the base, which is formed mostly by the atria, the apex is a feature of the ventricles, the heart’s main pumping chambers.
The heart is tilted, with its long axis oriented diagonally within the chest. The apex points distinctly downward, forward, and to the left of the body’s midline. This orientation makes the apex the lowest and most lateral part of the heart, projecting toward the left side. The thick-walled left ventricle forms this tip, giving the apex a mechanical role in the twisting motion that expels blood during contraction.
Locating the Apex in the Chest Cavity
The precise location of the heart’s apex is used as an anatomical reference for the general adult population. For a typical individual, the apex is situated behind the left fifth intercostal space, the gap found between the fifth and sixth ribs.
The apex is also found approximately at the left midclavicular line. This imaginary vertical line drops directly down from the midpoint of the left collarbone (clavicle). This location places the apex about 7.5 to 9 centimeters away from the center of the breastbone (sternum).
This location corresponds to the point where the left ventricle’s thick muscular wall comes closest to the anterior chest wall. This proximity allows the physical impulse of the heart’s contraction to be transmitted and felt externally. While this is the standard reference, individual body build (habitus) can cause slight variation in the exact position.
Clinical Importance of the Apex Beat
The anatomical location of the apex is medically relevant because it corresponds to the Point of Maximal Impulse (PMI), often called the apex beat. The PMI is the spot on the chest where the rhythmic cardiac impulse can be most clearly felt or heard during a physical examination. This impulse occurs as the contracting heart strikes against the inside of the chest wall.
The apex beat is used to take the apical pulse, considered the most accurate measure of a person’s heart rate. This measurement directly reflects the contraction of the left ventricle. It is especially useful when peripheral pulses, such as those felt at the wrist, are weak or irregular. Monitoring the position of the PMI is a diagnostic tool for healthcare providers.
If the apex beat is felt at a location other than the standard fifth intercostal space at the midclavicular line, it can signal an underlying health issue. Displacement of the PMI, particularly if shifted laterally or downward, may indicate an enlarged heart (cardiomegaly). Other conditions, such as fluid accumulation around the lungs (pleural effusion), can also physically push the heart and displace the apex beat.