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Heart Anatomy: Anatomical Position, Boundaries, and Clinical Landmarks

The heart sits obliquely in the mediastinum, with about 2/3 to the left of the midline. Understanding its position and borders is essential for physical exam, imaging interpretation, and procedural planning.

Anatomical Position

  • Orientation: Base (posterosuperior) → Apex (anteroinferior, leftward).
  • Planes: Right anterior oblique ~30–40° from sagittal.
  • Level: T5–T8 vertebral bodies (supine); apex at 5th ICS, 8–9 cm from midline (midclavicular line).

Borders (Surface Projections)

BorderStructuresSurface Landmark
Superior (Base)LA, RA, PV, SVC, IVC, aorta, PA3rd costal cartilage (R) to 2nd ICS (L)
Inferior (Apex)LV5th ICS, midclavicular line (8–9 cm from midline)
RightRA, RV, SVC, IVC3rd–6th costal cartilages, 1–2 cm right of sternum
LeftLV, LA, pulmonary trunk2nd–5th ICS, midclavicular line

Posterior Relations

  • Esophagus, descending aorta, thoracic vertebrae (T5–T8)
  • Parietal pericardium separates from mediastinal pleura/lung
  • Azygos/hemi-azygos veins, thoracic duct

Clinical Applications

  • Auscultation areas: Valve sounds project to specific chest wall sites (not over valves).
  • Percussion: Dullness maps cardiac borders (limited by lung hyperinflation, obesity).
  • Central lines: SVC/RA junction target (carina ~T4/T5).
  • Pericardiocentesis: Subxiphoid (apex) or apical (5th ICS) approach.
  • Imaging: CT/MRI axial planes show true orientation; CXR shows silhouette.

Key Measurements (Adult, CT-derived)

  • Transverse diameter: 12–14 cm
  • AP diameter: 8–10 cm
  • Cardiothoracic ratio (CXR): < 0.5 normal

Heart position varies with body habitus, respiration, and pathology. Knowledge of landmarks guides accurate clinical assessment.

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