In The Left Lateral Decubitus Position

1. With the patient in the left lateral decubitus position, how can you tell that you are feeling a left or right ventricular apical impulse? ANS: There are two methods.

Palpate the apical impulse to see if there is a sensation of a localized thrust. In the left lateral decubitus position an LV impulse feels as if a Ping-Pong ball were protruding between the ribs in systole. An RV impulse is usually more diffuse.

Look for medial or lateral retraction. An LV impulse will manifest medial retraction because the counter-clockwise rotation of the heart causes a decrease in volume of the RV and outflow tract during systole, which causes the medial aspect of the heart to withdraw from the chest wall and pull on any overlying chest wall structures including the skin. The skin movement is often too subtle to be detected by palpation and is best detected by observing the skin while palpating the apex beat. A mark on the skin made by a pen may aid in seeing slight medial retraction. An RV apical impulse will often show lateral retraction.

Note the retraction medial to the apex. The apex has a sustained impulse due to the effect of LVH. Although these tracings were taken in the supine position, medial retraction is best seen in the left lateral decubitus position.

2. How can you tell that there is cardiac enlargement with the patient in the left lateral decubitus position?

ANS: Look for a. An enlarged area of apical impulse in the Y axis, i.e., an apical impulse should not be felt in more than one interspace.

b. An enlarged area of apical impulse in the X axis, i.e., an apex impulse should be no more than 3 cm from side to side (about L/2 finger breadths).

The normal apex beat is not felt in two interspaces during the same phase of respiration.

A normal apical impulse is no larger than about IV2 fingertip widths (3 cm).

c. An enlarged area of medial retraction. The normal area of medial retraction is not much larger than that of the normal apex beat.

d. The presence of a combination of both medial and lateral retraction. If the medial retraction is dominant, you are probably feeling a large LV. If the lateral retraction is dominant, a large RV is probably producing the apical impulse.

Retraction in the mid-left thorax, with sustained outward movements on either side, tells you that there is a biventricular volume overload.

e. A biventricular overload, as in a large ventricular septal defect (VSD) may be manifest on the chest wall as a biventricular rock, i.e., both the left parasternal and apical areas may rise with systole, with an area of retraction between them.

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