Professional and Linguistic Assessments Board (PLAB) Practice Exam

Which condition is associated with a straight left heart border?

1. Mitral stenosis

2. Aortic regurgitation

3. Pulmonary stenosis

4. Cardiac tamponade

The correct answer is: Mitral stenosis

A straight left heart border is typically associated with mitral stenosis due to the specific changes that occur in the heart's anatomy as a result of this condition. In mitral stenosis, the left atrium often becomes enlarged due to increased pressure and volume overload caused by the obstruction of blood flow through the mitral valve. This enlargement pushes the left heart border straight out, resulting in a straightening of the contour on imaging studies such as chest X-rays. This characteristic appearance reflects the effects of the chronic pressure overload and the anatomical changes in the left atrium, particularly evident when mitral stenosis progresses. The other conditions mentioned can affect heart shape and size but do not typically lead to a straightening of the left heart border in the same way. For example, aortic regurgitation tends to lead to left ventricular enlargement and overall cardiac dilation, which does not produce the same appearance. Pulmonary stenosis primarily affects the right side of the heart and does not generally produce changes in the left heart border. Cardiac tamponade, while it can create an enlarged cardiac silhouette due to fluid accumulation around the heart, often presents with a more globular heart shape rather than a straightening of the left border.