Pericardial adaptations during chronic cardiac dilation in dogs

Area of Science:

• Cardiovascular Physiology
• Cardiac Remodeling
• Pericardial Adaptation

Background:

• The adaptive mechanisms of the pericardium to chronic cardiac dilation are not well understood.
• Previous research suggested alterations in pericardial size or pressure-volume relationships during cardiac enlargement.

Purpose of the Study:

• To investigate how the pericardium adapts to chronic cardiac dilation.
• To compare pericardial pressure-volume and stress-strain relationships, surface area, mass, and thickness in normal versus dilated hearts.

Main Methods:

• Comparison of seven normal dogs with seven dogs exhibiting chronic volume overload hypertrophy (due to a systemic arteriovenous fistula).
• Analysis of pericardial pressure-volume and stress-strain relations, surface area, mass, and average thickness.
• Nonlinear regression analysis to determine the proportionality constant for the pericardial pressure-volume curve.

Main Results:

• Dogs with cardiac hypertrophy showed increased pericardial volume and a more compliant pericardial chamber.
• Pericardial surface area and mass increased proportionally, maintaining unchanged average thickness.
• Pericardial mechanical properties, assessed by stress-strain analysis, were not significantly altered.

Conclusions:

• The pericardium enlarges in size and mass during chronic cardiac dilation.
• The pericardial chamber becomes more compliant, while intrinsic pericardial stiffness remains unchanged.
• The adaptive response involves the addition of new pericardial tissue, increasing its overall mass.