USMLE (United States Medical Licensing Examination) Step 1 Practice Exam

In Eccentric LVH due to aortic regurgitation, what is the primary compensatory mechanism that leads to LV dilation?

1. Increased contractility

2. Left ventricular remodeling

3. Reduced preload

4. Shortened relaxation time

The correct answer is: Left ventricular remodeling

In the context of eccentric left ventricular hypertrophy (LVH) due to aortic regurgitation, left ventricular remodeling is the primary compensatory mechanism that leads to left ventricular dilation. Aortic regurgitation results in the backflow of blood into the left ventricle during diastole, which increases the volume load on the heart. As the left ventricle accommodates this increased volume, it undergoes dilation to maintain cardiac output and reduce wall stress. This remodeling process is characterized by both hypertrophic and dilating changes, where the left ventricle not only thickens its walls to handle the increased pressure and volume but also stretches to allow for greater diastolic filling. This mechanism ultimately aims to preserve the heart’s function in response to the volume overload caused by aortic regurgitation. In contrast, increased contractility may help to manage the situation temporarily, but it is not the primary mechanism leading to dilation overall. Reduced preload would not contribute to dilation, as preload is determined by the volume returning to the heart. Shortened relaxation time, while it can pertain to changes in diastolic function, does not directly cause the dilation observed. Thus, the remodeling effect is central to the adaptive physiological response seen in this condition