Abstract 2359: 3-D Engineered Tissue Constructs (ETC) as an in vitro Model for the Study of Cardiac Fibrillation
Background: We have used cardiac monolayers as in-vitro model for the study of cardiac fibrillation. However they cannot sustain scrolls, which have been shown as an important mechanism that maintains cardiac fibrillation. Though it has been recently shown that 3-D ETCs can be made to simulate native cardiac environment, little is known about their electrophysiological properties.
Objectives: We hypothesised that 3D ETCs can sustain fibrillation by meandering and stationary rotors, and can produce APD alternans and unidirectional conduction block. In addition we hypothesised that the arrhythmias induced will allow for modulation by pacing, defibrillation and pharmacological intervention.
Methods: 25 ETCs were engineered by seeding neonatal rat cardiomyocytes into collagen scaffolds. They were field stimulated at 1 Hz starting 72 hours after seeding. Optical mapping was performed at day 6 (n=20) and 10 (n=5) with the following conditions: Norepinephrine and pinacidil were used for pharmacological intervention and field stimulation was replaced with local electrical stimulation.
Results: Measurements showed that 16/20 ETCs had spontaneous electrical activity. All 20 ETCs captured to 1 Hz programmed stimulation. Loss of capture was observed at 3 to 4 Hz with action potential alternans and conduction block. Application of norepinephrine showed accelerated spontaneous rate and APD reduction was observed after pinacidil infusion. Measurements at day 10 (older contructs with greater percentage of cardiac fibroblast due to proliferation) showed that only 2/5 ETCs had spontaneous activity, but all responded to electrical and chemical stimulation and demonstrated greater conduction block. Fibrillation was observed in 4/25 ETCs. 3 episodes had rotor morphologies behaviour that appeared to be anchored on a physical defect and another had a meandering rotor. All 4 episodes could be terminated by high energy stimulus.
Conclusion: These results show that ETCs have electrophysiological characteristics similar to isolated heart tissue and that they maintain fibrillation by meandering and stationary rotors that are amenable to modulation. This model could potentially be used to understand mechanisms that induce and maintain cardiac fibrillation.