Figure 5.

APD restitution and short-term memory effect on APD dispersion. (A) Examples of APD restitution from LMC, LQT1, and LQT2 hearts using random stimulation protocol. Note that the restitution slope is greatest in LQT2 followed by LMC and LQT1. (B) Goodness of fit (R²) of multivariate analysis using $AP{D}_n=C+{\alpha }_{1}C{L}_{n-1}+{\alpha }_{2}C{L}_{n-2}+\cdots +{\alpha }_{k}C{L}_{n-k}$where k is the k^th previous beats. R² including previous 10 beats were 0.848 ± 0.043, 0.85 ± 0.002, and 0.792 ± 0.093 for LMC, LQT1, and LQT2 respectively. (C) Coefficients (α₁ & α₂) from multivariate regression analysis (* indicates p < 0.05, One-Way ANOVA tests were performed between three groups and significant difference were founded at the 0.05 level. The differences of α₁ in LMC vs LQT1, LQT1 vs LQT2 and LMC vs LQT2 are significant at the 0.05 level by Fisher test and the differences of α₂ in LMC vs LQT1 and LQT1 vs LQT2 are significant at the 0.05 level by Fisher test). (D) Spatial patterns of 1^st coefficients (α₁) in LMC, LQT1, and LQT2 hearts. Note that the map of α₁ from LQT2 shows greater spatial heterogeneities (0.09–0.39) compared to that of LMC and LQT1 hearts (standard deviation of slope map = 0. 064 ± 0.025 in LQT2 vs. 0.029 ± 0.008 and 0.030 ± 0.014 in LQT1 and LMC, n = 4 hearts each, p < 0.05, Student’s t-test where appropriate). (E) Spatial patterns of 1^st and 2^nd coefficients (α₁ & α₂) in LQT2. The map of α₂ shows a spatial gradient with higher slope at the apex than the base, different from the α₂ map. The α₁ vs. α₂ plot in the right panel shows negative correlation (−0.27 ± 0.10 in LQT2 vs. −0.07 ± 0.15 in LQT1, p < 0.05, n = 6 hearts, Student’s t-test where appropriate), indicating that the gradient direction in α₂ is opposite that in α₁.