Spatial sampling requirements for the determination of the spatial distribution of repolarization in atrial tissue

The effect of spatial sampling resolution on estimates of properties of the action potential duration (APD90) field was studied in canine atria (n=8). Monophasic action potentials (MAPS) were recorded from the endocardium during Krebs-Henseleit perfusion (KH) (Δx=3.5 mm) and were repeated during perfusion with KH+0.5 μM acetylcholine (ACh). APD90 was estimated from MAP waveforms. Properties of the APD90 field were computed at spacings (Δx) of 3.5 mm, 5 mm, 7.1 mm, 10 mm, and 15 mm. Mean-APD90 and Std-APD90 at spacings greater than 3.5mm showed no significant difference from estimates based on 3.5 mm (control). Estimates of MeanGRAD and Std-GRAD (control) based on spacings more than 5 mm were significantly different from estimates based on 3.5 mm. In ACh data, the effect of spacing was similar. Spatial correlation length was similar for sites spaced 10 mm and closer (control & ACh). We conclude that accurate characterization of the APD90 field requires a resolution of at least 5 mm. Acetylcholine does not increase resolution requirements.