How does aging typically affect a dog's cardiac compliance?

How does aging typically affect a dog's cardiac compliance?

• A. Increases
• B. Decreases
• C. No change
• D. Random

Answer: (B)

As dogs age, the ventricular walls tend to stiffen because of fibrotic remodeling and changes in the extracellular matrix. This makes the ventricle less able to stretch during diastole, so its filling capacity declines. Cardiac compliance is the amount of change in volume for a given change in pressure during filling; when the ventricle becomes stiffer, this change in volume per pressure is smaller, meaning compliance decreases. Clinically, reduced compliance leads to diastolic dysfunction: the heart must generate higher filling pressures to achieve the same preload, even though systolic (pumping) function is often preserved initially. The underlying mechanism includes increased collagen content and cross-linking, along with slower relaxation of the cardiac muscle. If compliance were to increase, filling would occur more readily, which isn’t what aging typically does. No change wouldn’t reflect the well-documented structural aging of the heart, and a random pattern isn’t consistent with this progressive, predictable remodeling.

As dogs age, the ventricular walls tend to stiffen because of fibrotic remodeling and changes in the extracellular matrix. This makes the ventricle less able to stretch during diastole, so its filling capacity declines. Cardiac compliance is the amount of change in volume for a given change in pressure during filling; when the ventricle becomes stiffer, this change in volume per pressure is smaller, meaning compliance decreases.

Clinically, reduced compliance leads to diastolic dysfunction: the heart must generate higher filling pressures to achieve the same preload, even though systolic (pumping) function is often preserved initially. The underlying mechanism includes increased collagen content and cross-linking, along with slower relaxation of the cardiac muscle.

If compliance were to increase, filling would occur more readily, which isn’t what aging typically does. No change wouldn’t reflect the well-documented structural aging of the heart, and a random pattern isn’t consistent with this progressive, predictable remodeling.