Activation delay after premature stimulation in chronically diseased human myocardium relates to the architecture of...

Area of Science:

• Cardiology
• Electrophysiology
• Cardiac Pathology

Background:

• Progressive activation delay during premature stimulation correlates with sudden cardiac death in hypertrophic cardiomyopathy.
• Understanding the mechanism of increased activation delay in diseased myocardium is crucial.

Purpose of the Study:

• To elucidate the mechanism of increased activation delay in chronically diseased human myocardium.
• To investigate the relationship between fibrosis architecture and electrical conduction.

Main Methods:

• High-resolution unipolar mapping of epicardial electrical activity in 11 explanted human hearts during premature stimulation.
• Construction of activation maps and conduction curves, correlated with histological analysis of fibrosis.
• Study of epicardial sheets in a tissue bath to analyze conduction properties.

Main Results:

• Prominent increases in activation delay were associated with dense, patchy fibrosis with long fibrotic strands.
• Dense, diffuse fibrosis with short strands had minimal impact on conduction curves.
• Conduction patterns in patchy fibrotic areas were highly dependent on propagation direction relative to myocardial fiber orientation.

Conclusions:

• Nonuniform anisotropic characteristics from long fibrotic strands cause progressive activation delay in diseased myocardium.
• The increase in activation delay is dependent on wave front direction and fibrosis architecture.
• Findings provide insight into electrical conduction abnormalities contributing to cardiac events.