Anatomy
Thorax
Question 172 of 180
A 19 year old woman is brought to the ED having been stabbed in the chest. She has sustained a penetrating wound in the left fourth intercostal space, just lateral to the sternal border. Which of the following thoracic structures is most likely to have been injured:
Answer:
The right ventricle forms most of the anterior wall of the heart and extends from approximately the right border of the sternum to approximately 2 inches to the left of the sternum at the level of the fourth intercostal space. The left atrium forms the posterior surface of the heart (the only portion of the left atrium seen on the anterior surface of the heart is the left auricle). The left ventricle forms most of the left border and the diaphragmatic surface of the heart. The right atrium forms the right border of the heart.Cardiac Orientation
Anatomy / Thorax / Heart and Pericardium
Last Updated: 11th April 2019
The general shape and orientation of the heart are that of a pyramid that has fallen over and is resting on one of its sides.
- The apex of this pyramid projects forwards, downwards and to the left. The apex is formed by the inferolateral part of the left ventricle and is positioned deep to the left fifth intercostal space in the midclavicular line.
- The base is facing posteriorly. The base is formed mostly by the left atrium with a small portion of the right atrium and the proximal part of the great veins, and is fixed posteriorly to the pericardial wall, opposite the bodies of the T5 - T8 vertebrae (T6 - T9 when standing). The oesophagus lies immediately posterior to the base.
Table: Surfaces and Borders of the Heart
| Border/Surface | Main Structure (Contributing Structures) |
|---|---|
| Apex | Left ventricle |
| Base | Left atrium (right atrium, proximal great veins) |
| Anterior surface | Right ventricle (right atrium, left ventricle) |
| Inferior surface | Left and right ventricle |
| Left pulmonary surface | Left ventricle (left atrium) |
| Right pulmonary surface | Right atrium |
| Inferior border | Right ventricle (left ventricle) |
| Left border | Left ventricle (left auricle) |
| Right border | Right atrium |
| Superior border | Both atria, roots of great vessels |
Surfaces
There are four surfaces to the upturned pyramid:
- The anterior (sternocostal) surface consists mostly of the right ventricle with some of the right atrium and some of the left ventricle.
- The inferior (diaphragmatic) surface consists of the left ventricle with a small portion of the right ventricle separated by the posterior interventricular groove.
- The left pulmonary surface consists mainly of the left ventricle and a portion of the left atrium.
- The right pulmonary surface consists of the right atrium.
Borders
There are four main borders separating the surfaces of the heart:
- The inferior border is formed mostly by the right ventricle and a small portion of the left ventricle near the apex.
- The left border is formed mostly by the left ventricle with a small portion of the left auricle.
- The right border is formed by the right atrium.
- The superior border is formed by both atria and the roots of the great vessels.
![Modified by FRCEM Success. Original by Mikael Häggström (See above. All used images are in public domain.) [Public domain], via Wikimedia Commons](https://mrcemsuccess.com/wp-content/uploads/2017/02/Surface_anatomy_of_the_heart-2.png)
Orientation of the Heart. (Image modified by FRCEM Success. Original by Mikael Häggström [Public domain], via Wikimedia Commons)
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- Biochemistry
- Blood Gases
- Haematology
| Biochemistry | Normal Value |
|---|---|
| Sodium | 135 – 145 mmol/l |
| Potassium | 3.0 – 4.5 mmol/l |
| Urea | 2.5 – 7.5 mmol/l |
| Glucose | 3.5 – 5.0 mmol/l |
| Creatinine | 35 – 135 μmol/l |
| Alanine Aminotransferase (ALT) | 5 – 35 U/l |
| Gamma-glutamyl Transferase (GGT) | < 65 U/l |
| Alkaline Phosphatase (ALP) | 30 – 135 U/l |
| Aspartate Aminotransferase (AST) | < 40 U/l |
| Total Protein | 60 – 80 g/l |
| Albumin | 35 – 50 g/l |
| Globulin | 2.4 – 3.5 g/dl |
| Amylase | < 70 U/l |
| Total Bilirubin | 3 – 17 μmol/l |
| Calcium | 2.1 – 2.5 mmol/l |
| Chloride | 95 – 105 mmol/l |
| Phosphate | 0.8 – 1.4 mmol/l |
| Haematology | Normal Value |
|---|---|
| Haemoglobin | 11.5 – 16.6 g/dl |
| White Blood Cells | 4.0 – 11.0 x 109/l |
| Platelets | 150 – 450 x 109/l |
| MCV | 80 – 96 fl |
| MCHC | 32 – 36 g/dl |
| Neutrophils | 2.0 – 7.5 x 109/l |
| Lymphocytes | 1.5 – 4.0 x 109/l |
| Monocytes | 0.3 – 1.0 x 109/l |
| Eosinophils | 0.1 – 0.5 x 109/l |
| Basophils | < 0.2 x 109/l |
| Reticulocytes | < 2% |
| Haematocrit | 0.35 – 0.49 |
| Red Cell Distribution Width | 11 – 15% |
| Blood Gases | Normal Value |
|---|---|
| pH | 7.35 – 7.45 |
| pO2 | 11 – 14 kPa |
| pCO2 | 4.5 – 6.0 kPa |
| Base Excess | -2 – +2 mmol/l |
| Bicarbonate | 24 – 30 mmol/l |
| Lactate | < 2 mmol/l |
