Assessing the pattern of ST-segment depression during subendocardial ischemia using a computer simulation of the...

Area of Science:

• Biophysics
• Computational Biology
• Cardiology

Background:

• Electrogram (EG) waveforms depend on transmembrane action potentials (APs) of cardiac myocytes, excitation spread, and volume conductor properties.
• Transmembrane APs act as electromotive generators, creating potential differences recorded as EGs.
• EGs are the algebraic sum of endocardial and epicardial APs.

Purpose of the Study:

• To create an educational PC-based program simulating normal and pathological electrograms (EG).
• To analyze ST-segment and T-wave patterns during subendocardial ischemia using the simulation.
• To investigate the morphology of ST depression in subendocardial ischemia.

Main Methods:

• Utilized Microsoft Excel for a PC-based educational software.
• Simulated normal EGs by planimetrically reproducing animal epicardial and endocardial transmembrane APs, modified to mimic human APs.
• Simulated subendocardial ischemia by altering the subendocardial AP based on experimental and clinical data.

Main Results:

• Successfully reconstructed EG waveforms through algebraic subtraction of endocardial and epicardial APs.
• Simulated subendocardial ischemia by modifying only the subendocardial AP, resulting in horizontal ST segment depression.
• Achieved downsloping ST depression with modifications to subendocardial AP phase 3, suggesting it's not typical for pure subendocardial ischemia.

Conclusions:

• The PC program accurately derives EG waveforms from the algebraic sum of endocardial and epicardial APs.
• The simulated ST depression in subendocardial ischemia is predominantly horizontal.
• Downsloping ST depression may represent reciprocal changes or transmural ischemia.