What is a normal point of maximal impulse?

Normal Point of Maximal Impulse (PMI)

The normal PMI is located in the 5th intercostal space at or medial to the midclavicular line, presenting as a single, brief outward impulse measuring approximately 2-3 cm in diameter. 1

Location

• In adults, the PMI is normally found in the 5th intercostal space, though it can occasionally be in the 6th intercostal space 1
• The lateral margin should be located at or medial to the midclavicular line 1
• More precisely, the apex beat in healthy adults is typically located 2.8 to 5.4 cm from the midline when measured in the left lateral position 2
• In children, the location varies by age:
  • Birth to 3 years: 4th intercostal space 3
  • After age 3: gradually moves to the 5th intercostal space 3

Size and Characteristics

• Diameter: approximately 2.5 ± 0.5 cm in healthy adults 2
• Area: approximately 5.0 ± 2.5 cm² 2
• Quality: single, brief outward impulse that is normally shaped and free from any abnormality 1
• Intensity: typically medium degree (51%), though can be weak (25%) or strong (24%) in normal individuals 2

Clinical Examination Technique

• The PMI is best assessed with the patient in the full left lateral (90-degree) position, where it is palpable in 87% of healthy adults 2
• In the standard supine position, the PMI may be more difficult to palpate 1
• The probe marker should be directed toward the right shoulder when obtaining echocardiographic apical views from this location 1

Key Pitfalls to Avoid

• Do not use the nipple line as a reference point - it lies outside the apex beat at all ages and should not be used for clinical evaluation of cardiac size 3
• The midclavicular line provides only a rough estimate; actual measurement from the midline is more accurate for assessing cardiac size 3
• Individual variation is substantial, so the PMI location alone should not be used to diagnose pathology without considering size and quality 2

Abnormal Findings Suggesting Pathology

• Displacement lateral to the midclavicular line or beyond the left anterior axillary line suggests left ventricular enlargement 2
• Diameter ≥4.0 cm is both sensitive (96%) and specific (96%) for left ventricular dilatation 2
• Sustained or heaving impulse indicates moderate to severe left ventricular dysfunction 4
• Hyperactive or hyperkinetic impulse suggests increased cardiac activity 1