Difference Between Tapping Apex Beat and Normal Apex Beat
A tapping apex beat is characterized by a sharp, well-localized impulse of short duration that occurs early in systole, while a normal apex beat is a diffuse, sustained impulse that can be felt over a 2-3 cm area in the 5th intercostal space at the mid-clavicular line.
Characteristics of Normal Apex Beat
Location and Size
- Normally palpable in the 5th or 6th intercostal space 1
- Located at or medial to the mid-clavicular line in healthy adults
- Typically covers an area of approximately 2.5 cm in diameter or 5.0 cm² 2
- In the full left lateral position, the lateral margin is palpable within a 3-cm-wide area from the left anterior axillary line toward the mid-clavicular line 2
Quality and Duration
- Diffuse, sustained impulse
- Medium intensity in about 51% of healthy individuals, weak in 25%, and strong in 24% 2
- Coincides with ventricular systole
- Represents the normal contraction of the left ventricle against the chest wall
Characteristics of Tapping Apex Beat
Quality and Timing
- Sharp, well-localized impulse of short duration
- Occurs early in systole, often coinciding with the first heart sound (S1) 3
- May feel like a distinct "tap" against the examining fingers
- Often described as having a "tapping" quality
Clinical Significance
- Commonly associated with mitral stenosis 3
- The "tap" represents the first heart sound occurring perceptibly after the onset of the apex impulse itself 3
- The extent of delay between the onset of the apical thrust and the S1 "tap" correlates with the severity of mitral stenosis 3
Pathophysiological Basis
Normal Apex Beat
- Represents the normal contraction of the left ventricle
- Occurs when the anterolateral portion of the left ventricle contacts the chest wall during systole
- Duration corresponds to the ejection phase of systole
Tapping Apex Beat
- In mitral stenosis, the left ventricle is relatively empty at the start of systole due to impaired filling
- The first heart sound is accentuated and delayed due to prolonged left atrial-ventricular pressure gradient
- This creates the characteristic "tapping" sensation that follows the initial apical movement
Clinical Implications
Diagnostic Value
- A displaced apex beat (lateral to the mid-clavicular line) has significant diagnostic value for left ventricular enlargement 4, 2
- An apex beat diameter ≥4.0 cm is highly sensitive (96%) and specific (96%) for left ventricular dilatation 2
- The presence of a tapping quality to the apex beat should prompt evaluation for mitral stenosis 3
- Recent research suggests that apex beat characteristics also correlate with left atrial enlargement 5
Examination Technique
- Patient should be examined in the left lateral decubitus position for optimal assessment
- The examiner should use the palmar surface of the fingers to feel for the location and quality
- Both the location and character of the apex beat should be noted
Common Pitfalls in Assessment
- Obesity or thick chest wall may obscure the apex beat
- Emphysema can cause hyperinflation that pushes the heart away from the chest wall
- Pericardial effusion may diminish the intensity of the apex beat
- Failure to position the patient properly (left lateral position improves detection)
- Confusing the apex beat with other pulsations (e.g., epigastric pulsation)
By carefully assessing the location, size, and quality of the apex beat, clinicians can gain valuable diagnostic information about cardiac structure and function, particularly regarding left ventricular size and the presence of mitral valve disease.