During the contraction phase of the heart, the left ventricle becomes more spherical and, viewed from below, turns slightly in an anticlockwise direction. As a result of this, the most lateral part of the left ventricle (the apex) beats against the thorax wall; these precordial beats are termed the apex beat. Under normal conditions, the apex beat is located on or medial to the left midclavicular line in the 4th or 5th intercostal space. If the thorax is examined diagonally from the side then the apex beat can sometimes be observed. However, this is by no means always possible.
A decrease in the heart’s contraction strength can be the cause of a less visible apex beat. More often the cause is not to be found in the heart. For example, in elderly patients or those who are obese, suffer from emphysema or have large breasts, inspecting the apex beat is often difficult if not impossible. If the apex beat can be seen, it should be determined whether this is located on or within the left midclavicular line. If the apex beat falls outside this line it might indicate left ventricular hypertrophy (enlargement of the left ventricle due, for example, to hypertension) or dilatation (enlargement due for example to an aortic insufficiency) or displacement of the heart to the left due, for example, to a tension pneumothorax on the right or an elevated diaphragm.
Systolic retractions at the apex of the left ventricle can be indicative of constrictive pericarditis (inflammation of the heart sac as a result of which constriction and expansion of the heart are impaired).
