Module 3: Abnormal 4-chamber view

The normal cardiac to thoracic (C/T) circumference ratio is 0.55 with a range of approximately 0.5-0.6. The heart can be bigger than normal (C/T >0.6) or smaller than normal (C/T <0.5)

Low cardiothoracic ratio

• Compression from an intrathoracic mass

High cardiothoracic ratio

• Global cardiomegaly
• Dilation of one chamber or one side
• Small chest