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Simulating Initiation and Termination of Reentry in Cardiac
TissueEna XiaoMentor: David M. Chan
GOAL
• To understand the dynamic of a ring of excitable media that can be a cause of cardiac arrhythmia.
Background• Arrhythmias - abnormal heart rhythms
– Bradycardia - less than 60 beats per min.– Tachycardia - pace of the heart is faster
than the regulatory signal from the sinus node (over 100 beats per min).• Rapid heart beating in the ventricles can be
life-threatening. (ex. Ventricular fibrillation - heart can’t pump any blood)
Currently, over 2.2 million Americans are living with atrial fibrillation. (Estimated by American Heart Association)
Heart Diagram
Glossary
• Reentry: unidirectional recirculation of AP.• UDC: unidirectional circulation• Diastolic Interval (DI): recovering time
between AP.• Conduction Time (CT): the time required for
an AP wave front to travel a specified distance.
• Action Potential Duration (APD): defined with respect to a threshold voltage.
• T1 / T2 / T3 / T4: Threshold
Ring-like Cardiac Tissue
• A schematic representation of a ring of cardiac tissue.
Adjacent cells’ Voltage
Restitution Curve
(a) APD Restitution Curve (B) CT Restitution Curve
Thresholds
In order to initiate and maintain reentry, the
following thresholds must be satisfied.
– Each cell requires a minimum DI for recovery of
excitability.
– The reentrant action potential must propagate
around the ring slow enough for cell one to recover
excitability
– The reentrant action potential must propagate
around the ring fast enough to excite cell one
before the SA node
What I have done.
• Generating data from the model with different parameters, and looking at patterns.
• Studying different conditions that may cause lethal arrhythmia.
UDC vs. Reentry
Thank You!
Dr. David Chan, Mentor
Dr. Allison Johnson, Coordinator of HHMI Summer Scholar Program
Hailan Liu