The apex beat, also called the point of maximum impulse (PMI), is the furthermost point outwards (laterally) and downwards (inferiorly) from the sternum at which the cardiac impulse can be felt. The cardiac impulse is the result of the heart rotating, moving forward and striking against the chest wall during systole.

[edit] Identification

The normal apex beat can be palpated in the precordium left 5th intercostal space, at the point of intersection with the left midclavicular line. In children the apex beat occurs in the fourth rib interspace medial to the nipple. The apex beat may also be found at abnormal locations; in many cases of dextrocardia, the apex beat may be felt on the right side.

[edit] Interpretation

Lateral and/or inferior displacement of the apex beat usually indicates enlargement of the heart, called cardiomegaly. The apex beat may also be displaced by other conditions:

• Pleural or pulmonary diseases
• Deformities of the chest wall or the thoracic vertebra

Sometimes, the apex beat may not be palpable, either due to a thick chest wall, or conditions where the stroke volume is reduced; such as during ventricular tachycardia or shock.

The character of the apex beat may provide vital diagnostic clues:

• A forceful impulse indicates pressure overload in the heart (as might occur in hypertension)
• An uncoordinated (dyskinetic) apex beat involving a larger area than normal indicates ventricular dysfunction; such as an aneurysm following myocardial infarction

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