Cardiac function, fiber shortening, and dynamic geometry.

Area of Science:

• Cardiovascular Physiology
• Biomedical Engineering
• Medical Imaging

Background:

• Accurate cardiac geometry is crucial for modeling heart pump function.
• Previous models relied on simplified geometries due to limitations in measurement techniques.
• Dynamic, detailed dimensional data of the working heart has been lacking.

Purpose of the Study:

• To present novel methods for measuring the dynamic geometry of the working canine heart.
• To quantify cardiac dimensions, intramural deformations, and fiber shortening in situ.
• To analyze regional contraction and relaxation patterns throughout the cardiac cycle.

Main Methods:

• Utilized ultrasound-velocity tomography for dynamic geometry measurement of isolated canine hearts.
• Employed implanted radiopaque markers and biplane roentgen techniques for in situ measurements.
• Measured cardiac dimensions, intramural deformations, and fiber shortening dynamically.

Main Results:

• Successfully measured dynamic cardiac geometry and intramural deformations in canine hearts.
• Presented detailed regional contraction and relaxation patterns.
• Computed epicardial fiber shortening, demonstrating dependence on the preceding RR interval.

Conclusions:

• The developed techniques provide accurate dynamic measurements of cardiac geometry and function.
• These methods enable a more precise understanding of the heart's pump mechanism.
• Findings highlight the influence of cardiac cycle dynamics on myocardial deformation.