Grant: Collaborative Health Research Projects

Junctional Ectopic Tachycardia (JET) is a supraventricular tachycardia that occurs post-operatively after open heart surgery in young children. JET can occur in >20% of patients undergoing correction for specific congenital heart defects and is associated with significant morbidity and mortality. Since the etiology of JET is not understood, clinical treatment often lacks efficacy and often results in poor patient outcomes. Cardiac synchrony is maintained by a complex arrangement of primary and secondary pacemaking foci. These foci communicate with the rest of the myocardium through electrical conduction pathways and it is this co-ordinated communication that ensures cardiac synchrony and adequate blood flow to the brain and to the rest of the body. Electrical propagation in the heart is directional: electrical wave fronts do not spread evenly in all directions but rather follow electrical pathways formed by various heart tissues. Electrical conduction follows the myofibril alignment of the heart muscle and surgery may disrupt these conduction pathways. In the absence of primary pacemaker activity, secondary and or ectopic pacemaking sites may further disrupt cardiac synchrony. However, neither electrical conduction nor myofibril alignment is easily detected. An instrument that can visualize both electrical conduction pathways as well as the cardiac tissue that delineates these conduction pathways is required to minimize dyssynchrony. Two separate technologies exist that can visualize these respective attributes. Fluorescent optical action potential mapping (APM) can resolve electrical conduction pathways and optical coherence tomography (OCT) can resolve myofibril alignments. Optical mapping is a fluorescent imaging technique that replaces the traditional microelectrode with a voltage-sensitive dye and a high performance digital camera. The fluorescent dye encodes changes in cellular membrane potential into changes in cellular fluorescence and provides non-contact action potential recordings. Optical coherence tomography utilizes back-scattered light, similar to the acoustical reflections used in ultrasound imaging devices, and creates a depth-resolved image indicating tissue type and myofibril direction as a function