Apex beat: norm and biomechanics
Palpation always begins with an orientation phase: the palm of the right hand is gently placed on the precordial region. After that, the precise localization of pulsations is determined exclusively with the fingerpads, which must be firmly pressed against the chest wall. When examining female patients, the breast should be displaced upward and to the right (the same position is maintained subsequently for auscultation).
The main landmark during the examination is the apex beat. Its occurrence is driven not only by the muscular contraction of the left ventricular myocardium. The key biomechanical factor is that during systole, the heart "straightens" and rotates around its axis. As a result, the apex makes a firm, thrusting movement and strikes the anterior chest wall.
Normally, it is located in the fifth intercostal space, approximately 1 cm medial to the left midclavicular line (linea medioclavicularis sinistra). In about a third of healthy individuals, the apex beat is not palpable because the apex is anatomically covered by a rib. Visually, it is most noticeable in patients with an asthenic build and wide intercostal spaces. During palpation, the physician evaluates three main parameters:
- Width (area): the size of the shaking zone (normal is 1–2 cm²).
- Height: the amplitude of chest wall oscillations.
- Resistance (strength): the pressure exerted by the apex on the palpating fingers.
Causes of displacement and changes in apex beat properties
Changes in the localization of the heart apex occur under the influence of cardiac and extracardiac factors. Extracardiac causes are associated with the physical displacement of the mediastinum or diaphragm. For example, space-occupying processes (lung tumors, fluid or gas accumulation in the pleural cavity) shift the heart to the side. A high standing of the diaphragm due to ascites or meteorism also alters its position.
Cardiac causes are directly related to the enlargement of heart chambers:
- Left ventricular (LV) hypertrophy or dilatation: the impulse shifts to the left and downward, down to the sixth intercostal space.
- Right ventricular (RV) hypertrophy or dilatation: the impulse shifts only to the left. The enlarged right ventricle pushes the left one aside, but the apex itself does not drop downward.
The properties of the impulse directly indicate the type of myocardial remodeling. If the width (area) exceeds 3 cm in diameter, this is a reliable sign of LV dilatation. If a combination of increased amplitude and heightened resistance is observed, it indicates LV hypertrophy—clinically, such an impulse is referred to as "heaving" or "diffuse" (dome-shaped).
Cardiac impulse: differences and limitations of the method
Unlike the apex beat, the cardiac impulse is caused by the contraction of the entire heart, primarily the right ventricle adjacent to the anterior chest wall.
To detect it, the patient is placed supine with the head of the bed elevated. The fingerpads are successively pressed into the third, fourth, and fifth intercostal spaces at the left sternal border. The anatomical basis of the impulse corresponds to the level of the 4th rib and the 4th intercostal space.
In healthy individuals (except for asthenics with wide intercostal spaces), the cardiac impulse is neither visible nor palpable. Its distinct appearance is an important marker of right ventricular hypertrophy. However, the method has a significant limitation: in severe pulmonary emphysema, hyperinflated lungs overlie the heart, which can cause the cardiac impulse to be absent even with significant RV hypertrophy.
"Cat's purr" sign and other pulsations
The "cat's purr" sign (chest wall thrill) is a palpable sensation of low-frequency vibration. This phenomenon is the tactile equivalent of murmurs and occurs due to obstructed blood flow through narrowed orifices. It always indicates organic heart disease (stenosis) and is accompanied by a high-intensity murmur.
The thrill is detected over valve projection areas and strictly coincides with the phases of the cardiac cycle:
- Diastolic thrill at the apex indicates mitral stenosis (narrowing of the left atrioventricular orifice).
- Systolic thrill at the apex occurs in mitral regurgitation.
- Systolic thrill over the aortic orifice is characteristic of aortic stenosis.
In addition to thrills, the physician may detect other pathological pulsations. Pulsation behind the manubrium sterni often indicates an aneurysm of the aortic arch. Epigastric pulsation may be normal in thin patients (abdominal aortic pulsation), but requires differentiation from RV hypertrophy. Widespread pulsation medial to the apex beat indicates severe lesions—transmural myocardial infarction or a left ventricular aneurysm.
To remember the displacement of the apex beat: The Left Ventricle pulls the heart "to the Left and Down" (LV), while the Right Ventricle simply pushes its neighbor "to the Left" (without downward displacement).
Class and exam questions
Why is the apex beat not palpable in some healthy individuals?
In about 1/3 of patients, the heart apex is anatomically covered by a rib, so the impulse is physically not palpable, which is an absolute variant of normal.
How to distinguish left ventricular hypertrophy from dilatation during palpation?
In dilatation, the width (area) of the impulse increases to more than 3 cm. In hypertrophy, the oscillation amplitude and resistance increase (it becomes "heaving").
What is the main difference between the apex beat and the cardiac impulse?
The apex beat is formed primarily by the apex of the left ventricle and is palpable along the midclavicular line, whereas the cardiac impulse is formed by the right ventricle and is detected at the left sternal border.
What else to study on this topic
- Features of the differential diagnosis of epigastric pulsation (aorta versus right ventricle).
- The connection between the "cat's purr" sign and valve auscultation points.
- Physical signs of an aortic arch aneurysm.
- The mechanism of low-frequency oscillation formation in stenosis.
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