Transcript Simulating Initiation and Termination of Reentry in

Simulating Initiation and
Termination of Reentry in
Cardiac Tissue
Ena Xiao
Mentor: 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