Question

Enumerate the structures forming the right and left heart border on a plain chest radiograph (PA view). Discuss the features of enlargement of various cardiac chambers on a plain radiograph. [2+8]

Hint:

Enlargement of the cardiac chambers can lead to changes in the heart borders on a chest radiograph. The right heart border is predominantly formed by the right atrium, and the left heart border by the left atrium and left ventricle. Enlargement of any chamber causes specific border changes.

Answer 1

Step 1: Structures Forming the Right and Left Heart Border on a Plain Chest Radiograph (PA View).
(1) Right Heart Border: - The right heart border is formed by the right atrium on a PA chest radiograph. The right atrium is visible on the right side of the heart silhouette, extending from the right border of the chest and merging with the right ventricle.
(2) Left Heart Border: - The left heart border is formed by the following structures from superior to inferior:
- Left atrium (forming the upper part of the left heart border, adjacent to the pulmonary veins).
- Left ventricle (forming the lower and largest portion of the left heart border).
- Aortic arch (forming the uppermost portion of the left heart border, just behind the left clavicle).
Step 2: Features of Enlargement of Various Cardiac Chambers on a Plain Chest Radiograph.
(1) Right Atrium Enlargement: - Enlargement of the right atrium will cause an increase in the right heart border width, particularly at the right atrial appendage area. On a PA chest radiograph, this leads to a bulge at the right middle of the heart border.
- This enlargement is often seen in right-sided heart failure, pulmonary hypertension, or tricuspid valve disease.
- Associated features: A rightward shift of the heart, prominent superior vena cava, and dilated azygous vein.
(2) Right Ventricle Enlargement: - Right ventricular enlargement leads to a bulging of the right heart border in the right lower quadrant. This can cause the cardiac silhouette to become more rounded in the region below the right atrium.
- This enlargement is seen in conditions like chronic obstructive pulmonary disease (COP, pulmonary embolism, pulmonary hypertension, and tricuspid regurgitation.
- Associated features: A widened costophrenic angle, pulmonary artery enlargement, and possible right-sided heart failure signs.
(3) Left Atrium Enlargement: - Left atrial enlargement results in the posterior bulging of the left heart border, especially seen on a lateral chest radiograph. On a PA view, it may lead to a prominent or elevated left atrial appendage, visible near the pulmonary veins.
- This is often associated with mitral valve disease (e.g., mitral stenosis), aortic stenosis, or left-sided heart failure.
- Associated features: A double density sign at the right upper side of the heart silhouette, representing the enlarged left atrium. The left atrial appendage may appear as a bulge on the left heart border.
(4) Left Ventricle Enlargement: - Left ventricular enlargement causes an increase in the size of the left heart border, especially in the lower part of the heart. This can result in a widened cardiac silhouette with a flattened or straightened left border.
- The apex of the heart may shift downwards and laterally. Left ventricular hypertrophy (LVH) often leads to a longer and more vertical left heart border.
- Associated features: The cardiac apex may be displaced laterally, and pulmonary venous congestion may be seen, along with interstitial edema or Kerley B lines.
- This enlargement is often seen in conditions like hypertension, aortic regurgitation, or valvular heart disease.
(5) Overall Heart Enlargement (Cardiomegaly): - If the heart as a whole is enlarged, the cardiothoracic ratio (the ratio of the heart width to the chest width) will increase. This is a sign of heart failure or other diseases causing generalized enlargement of multiple chambers.
- Associated features: A widened cardiac silhouette and pulmonary congestion, often with pleural effusions and signs of left-sided heart failure.