A stab wound enters the thorax in the 4th left intercostal space in the midclavicular line. Which cardiac chamber is most likely injured?

• A Right ventricle
• B Right atrium
• C Left atrium
• D Left ventricle ✓

Explanation

The surface anatomy of the heart: the right ventricle forms the anterior surface (anterior to the sternum); the left ventricle forms the left border and apex. A wound in the 4th left intercostal space in the midclavicular line corresponds to the cardiac apex region, which is formed by the left ventricle. The left ventricle lies inferolateral. While the right ventricle is the most anteriorly positioned chamber (most common in stab wounds near the sternum), the apex at the 5th intercostal space / midclavicular line is the left ventricle.

Reference: BD Chaurasia's Human Anatomy, 8th ed.

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Written and medically reviewed by the StethoPrep medical team.