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

ThresholdsIn 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