Abstract 646: Dual-modal Biophotonic Imaging of the Canine Sino-Atrial Nodal Structure and Function
The origin of a canine heart beat is hidden from epi- or endocardial mapping due to slow impulse propagation within the sinoatrial node (SAN) before its atrial breakthrough. Thus, the relation between the 3D structure of the atrial pacemaker complex and propagation pattern is not well understood.
Methods: We used optical mapping with voltage-sensitive dye and optical coherence tomography (OCT, 10 μM resolution) for structure/function study of impulse generation and propagation. Canine coronary perfused preparations (n=4) contained SAN, right atrial free wall, superior and inferior vena cava, and interatrial septum and was immobilized with blebbistatin (5 μM).
Results: SAN region was identified by optical action potential morphologies with slow diastolic depolarization and multiple component upstrokes corresponding to different layers of conduction, including SAN and atrial tissue. Excitation originated in the center of SAN with a cycle length (CL) of 618±68 ms, spread anisotropically parallel to the crista terminalis (CT), and failed to conduct toward the CT and septum (see Fig⇓). Functional lines of block correlated with the location of sinus node arteries. Atrial breakthrough occurred 57±1μMs after the earliest SAN excitation 5.5±0.3 mm away. In all preparations, two different breakthrough locations were observed during the experiment separated by 14.8±1.5 mm. OCT demonstrated that these breakthrough sites correspond to two distinct fiber bundle structures connecting SAN and CT.
Conclusion: Using bimodal biophotonic imaging we demonstrated how structure of the atrial pacemaker complex determines the 3D pattern of excitation in the SAN region of the canine heart.