What may cause the point of maximal impulse (PMI) to be displaced?

The point of maximal impulse (PMI) refers to the location on the chest where the heartbeat is most strongly felt, typically located at the 5th intercostal space along the midclavicular line. When this point is displaced, it often signals a change in heart size, shape, or position.

Cardiomegaly, which is an enlargement of the heart, commonly causes the PMI to be displaced laterally or downward from its usual position. This occurs as the enlarged heart takes up more space in the thoracic cavity and pushes against adjacent structures, altering the normal anatomy. In cases of heart failure, dilation of the heart chambers or hypertrophy due to increased workload can lead to this alteration.

In contrast, while hypertension can lead to condition changes in the heart that could be significant in the long term, it does not directly cause a displacement of the PMI on its own. Arrhythmias can affect heart rhythm but are not associated with the physical position of the heart. Pneumothorax refers to air in the pleural space and would generally affect lung dynamics rather than directly influencing the heart's position on the chest wall.

Thus, the main reason why cardiomegaly is the cause of the PMI displacement is