Which Ventricle Is Causing the Apical Impulse

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The heart during systole, becoming smaller, generally withdraws from the chest wall except for the apex for the reasons explained above. The effect of this withdrawal on the chest wall can be observed as an inward movement of the chest wall during systole called "retraction." Although the heart is basically comprised of two separate pumps (right and left ventricles), these two pumps operate normally at two vastly different pressures. Left ventricular systolic pressures being approximately five times higher than that of the right ventricle, its wall tension is much higher, resulting in the increased wall thickness of the left ventricular chamber. The effect of the increased muscle mass on the left side leads to dominance of the left-sided hydrodynamic forces described above. This results in the left ventricular apex as the only area of normal contact during systole. The rest of the heart essentially retracts from the chest wall. In a normal heart, this retraction of the chest wall can be observed to be located medial to the apical impulse and involving part of the left anterior chest wall (20). Even the right ventricle, which is anatomically an anterior structure, is normally pulled away from the chest wall because of its own contraction (becoming smaller) and, more importantly, the septal contraction also pulling the right ventricle posteriorly. This retraction observed in normal patients is located medial to the apical impulse (23,24). It can be best appreciated with patients in the left lateral decu-bitus position with a palpating finger only on the apical impulse with clear view of the rest of the precordium for proper observation of the inward movement of the retraction (opposite in direction to the outward movement of the apical impulse). This "medial retraction" identifies and indicates that the left ventricle forms the apical impulse. The extent of the area of medial retraction may be variable depending on both cardiac and extracardiac factors such as the compliance of the chest wall. It may sometimes be noted only over a small area very close to the apex beat. Nevertheless, if it is medial to the apical impulse, it still identifies the apex beat to be that caused by the left ventricle (Figs. 7A-C). (See also Apex Videofiles 1, 2, and 3 under Precordial Pulsations on the Companion CD.)

Normal Apical Impulse

Systolic Retraction

Fig. 7. (A) Normal apexcardiogram (Apex) showing a small A wave caused by atrial contraction (not palpable). This is followed by a rapid rise peaking at point E (onset of ejection), corresponding to the onset of the carotid pulse upstroke. The apex beat moves rapidly away from the recording transducer as well as the palpating hand during the last two-thirds of systole, ending at O point, corresponding to mitral valve opening. (B) Simultaneous recordings of electrocardiogram (ECG), carotid pulse tracing, phonocardiogram (Phono), and recording from an area medial to the apex beat showing systolic retraction, indicating that, in this patient, the apex beat is formed by the left ventricle. (Continued on next page)

When right ventricular forces are exaggerated and become dominant because of high pressures, as in pulmonary hypertension and/or excess volume in the right ventricle causing an enlarged right ventricle (as may be seen in conditions of left-to-right shunt through an atrial septal defect where the right ventricle receives extra volume of blood because of the shunt flow in addition to the normal systemic venous return), the right ventricle may form the apical impulse. Usually in these states the left ventricular forces are also dimin-

Apexcardiogram

Fig. 7. (Continued) (C) Apexcardiogram of a patient with coronary artery disease with normal left ventricular systolic function. The amplitude and the duration of the systolic wave of the apex beat are normal. The downstroke of the apex starts at the upstroke of the carotid pulse (very early systole). The A wave is exaggerated (atrial kick) because of a strong atrial contraction evoked by the increased stiffness of the left ventricle (decreased diastolic compliance) producing the S4 recorded on the phonocardiogram.

Fig. 7. (Continued) (C) Apexcardiogram of a patient with coronary artery disease with normal left ventricular systolic function. The amplitude and the duration of the systolic wave of the apex beat are normal. The downstroke of the apex starts at the upstroke of the carotid pulse (very early systole). The A wave is exaggerated (atrial kick) because of a strong atrial contraction evoked by the increased stiffness of the left ventricle (decreased diastolic compliance) producing the S4 recorded on the phonocardiogram.

ished because of underfilling of the left ventricle (e.g., atrial septal defect, pulmonary hypertension). In this situation the hydrodynamic forces, which lead to the formation of the apex beat being right ventricular, result in elimination of normal area of medial retraction. They may in fact be replaced by an outward movement of the precordium from the sternum to the apex area. In such patients, the area of the chest wall lateral to the apical impulse will have the inward movement during systole (20,23,29). This lateral retraction is again best observed when care is taken to have a clear view of the lateral chest wall with the palpating finger on the apex beat. The presence of lateral retraction identifies the apical impulse to be formed by the right ventricle, which is an abnormal state.

The usefulness of identifying the retraction and thereby determining the ventricle forming the apical impulse lies in the fact that all information derived from the assessment of that apex beat pertains to that ventricle (e.g., a wide area apex beat with medial retraction implies left ventricular enlargement).

When both the right and the left ventricles are enlarged, both of them may produce palpable impulses, each having its own characteristics (the left ventricular impulse with an area of retraction that is medial to it and the right ventricular impulse overlying the lower sternal area with an area of retraction lateral to it) (23). The apical impulse, being the lateral most impulse, will be left ventricular. The retraction will therefore be in between the two impulses, therefore termed the median retraction. (See Apex videofile 7 under Precordial Pulsations on the Companion CD.)

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Responses

  • Sara
    What is ventricular muscle causing apex beat?
    2 years ago
  • hildifons grubb
    Why apex beat is right and upwards in right ventricular enlargement?
    1 year ago
  • CARMEN
    How apical impulse formed in the heart?
    1 year ago

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