Chest x-ray -Cardiothoracic Ratio -CARDIAC SIZE - Cardiomegaly

Summary

This video explains how to measure the cardiothoracic ratio, a crucial tool for determining heart size and detecting enlargement. The process involves using a PA (posterior-anterior) chest X-ray to measure the heart's transverse diameter and the maximum width of the thoracic cavity. A cardiothoracic ratio greater than 50% suggests an enlarged heart, potentially indicating cardiac enlargement. The video also discusses conditions like COPD that can cause the heart to appear artificially small due to changes in lung volume. The procedure is outlined step-by-step with sample measurements to aid understanding.

Takeaways

• 😀 The cardiothoracic ratio is an essential tool for assessing heart size on a chest X-ray.
• 😀 A PA (posterior-anterior) view X-ray is required to measure the cardiothoracic ratio accurately.
• 😀 To measure the ratio, draw a vertical line from the start of the thoracic cavity to the level of the diaphragm.
• 😀 The cardiac shadow is divided into thirds, with 1/3 on the right side and 2/3 on the left side.
• 😀 The maximum extension of the heart on both the right and left sides of the X-ray must be measured.
• 😀 The transverse diameter of the heart is the sum of the measurements of the right and left cardiac shadows.
• 😀 The maximum width of the thoracic cavity is also measured to calculate the ratio.
• 😀 The cardiothoracic ratio is calculated by dividing the transverse diameter of the heart by the maximum width of the thoracic cavity.
• 😀 A normal cardiothoracic ratio is usually around 50%.
• 😀 If the cardiothoracic ratio exceeds 50%, it indicates that the cardiac size is enlarged, which could be due to cardiomegaly.
• 😀 Factors such as COPD (Chronic Obstructive Pulmonary Disease) can cause an artificial appearance of a smaller heart on the X-ray due to changes in lung volume and diaphragm position.

Q & A

What is the cardiothoracic ratio and why is it important?

The cardiothoracic ratio is a measurement used to assess the size of the heart in relation to the size of the chest. It is important for physicians to evaluate whether the heart is enlarged or not, which can indicate certain health conditions.

Which type of X-ray view is recommended for measuring the cardiothoracic ratio?

The posterior-anterior (PA) view is recommended for measuring the cardiothoracic ratio. The AP (anteroposterior) view is generally not used for this purpose.

How do you measure the cardiothoracic ratio?

To measure the cardiothoracic ratio, draw a vertical line from the top of the thoracic cavity to the diaphragm. Then, measure the maximum extension of the heart's shadow on both the right and left sides and add those two measurements together. The cardiothoracic ratio is calculated by dividing the transverse diameter of the heart by the maximum width of the rib cage.

What does the calculation of the cardiothoracic ratio indicate?

The cardiothoracic ratio indicates the size of the heart. A ratio greater than 50% suggests that the heart is enlarged, which may signal a cardiac condition such as cardiomegaly.

What are typical measurements used in the cardiothoracic ratio calculation?

In the example given, the measurements were 4 cm for the right side, 8 cm for the left side, and 24 cm for the maximum width of the rib cage. Adding the right and left side measurements (4 + 8 = 12 cm), the cardiothoracic ratio is calculated by dividing this by the rib cage width (12/24 = 0.50, or 50%).

How is the cardiothoracic ratio calculated as a percentage?

To calculate the cardiothoracic ratio as a percentage, divide the transverse diameter of the heart by the maximum width of the rib cage and multiply by 100. For example, 12 cm / 24 cm = 0.50, and then 0.50 * 100 = 50%.

What does a cardiothoracic ratio greater than 50% suggest?

A cardiothoracic ratio greater than 50% suggests that the heart is enlarged, which may indicate a condition called cardiomegaly.

Can the cardiothoracic ratio ever appear artificially altered?

Yes, certain conditions like chronic obstructive pulmonary disease (COPD) can cause the lungs to expand, leading to flatter diaphragms and darker lung fields on X-rays. In such cases, the heart may appear artificially smaller.

What effect does COPD have on the appearance of the heart on X-rays?

COPD can cause the lungs to expand, which leads to flat diaphragms and darker lung fields. This can make the heart appear smaller than it actually is, which may lead to a false impression of a reduced cardiothoracic ratio.

Why is it important to avoid inaccurate calibration when measuring the cardiothoracic ratio?

Inaccurate calibration can lead to incorrect measurements, which may affect the diagnosis and assessment of heart size. Accurate measurements are crucial for determining whether the heart is enlarged or if other factors may be affecting the appearance of the heart on an X-ray.