3.2 AF rotors and the fibrotic tissue properties
NPAs were found in 61 (21%) of 287 segments and PAs were found in the remaining 226 (79%) segments. The distribution of the NPAs is shown in Figure 1. The NPAs were mostly found around the PV antrum (35%), subsequently anterior (18, and roof (12%) segments.
An ROC curve analysis yielded an optimal cutoff value of 5.7 and 10% for the LGE-entropy and LGE-volume ratio, respectively. As for the optimal LGE-entropy, the sensitivity, specificity, and positive and negative predictive values for the cutoff values were 75.4%, 41.6%, 25.8%, 86.2%, respectively. As for the optimal LGE-volume ratio, the sensitivity, specificity, and positive and negative predictive values for the cutoff values were 67.2%, 49.1%, 26.3%, 84.7%, respectively.
According to an LGE-entropy of 5.7 and LGE-volume ratio of 10%, the fibrotic tissue properties were classified into 4 groups: heterogenous healthy tissue (group 1 [G1]:LGE-entropy of ≧5.7 and LGE-volume ratio of < 10%), heterogenous fibrotic tissue (group 2 [G2]: LGE-entropy of ≧5.7 and LGE-volume ratio of ≧10% ), homogenous healthy tissue (group 3 [G3]: LGE-entropy of < 5.7 and LGE-volume ratio of <10%), and homogenous fibrotic tissue (group 4 [G4]: LGE-entropy of < 5.7 and LGE-volume ratio of ≧10%). Figure 2 shows the distribution of both the NPAs and PAs according to the LGE-entropy and LGE-volume ratio. Of interest, no NPAs could be found in regions with an LGE-volume ratio of ≧50%. Figure 3 shows the proportion of NPAs in each group. The proportion of NPAs was significantly higher in G2 than the other groups (38 [30%] of 126 vs. 23 [14%] of 161 segments, p = 0.001). Individually, the proportion of the NPAs in G2 was significantly higher than that in G3 and G4. The proportion of NPAs in G2 was higher but was not significant (8 [15.4%] of 52 segments in G1 vs. 38 [30.2%] of 126 segments in G2 vs. 12 [15.2%] of 79 segments in G3 vs. 3 [10.0%] of 30 segments in G4; p = 0.024). Although the LGE-entropy and LGE-volume ratio did not differ between the NPAs and PAs, the proportion of the tissue properties (G1 to G4) significantly differed between the NPAs and PAs. As shown in Figure 4, the NPAs could predominantly consist of G2, subsequently G3, but extremely less of G4, while the PAs could equally consist of G1, G2, and G3 (NPAs: 8 [13.1%] in G1, 38 [62.3%] in G2, 12 [20.0%] in G3, 3 [4.9%] in G4; PAs: 44 [19.5%] in G1, 88 [38.9%] in G2, 67 [29.6%] in G3, 27 [11.9%] in G4). Figure 5 shows a representative case. Five NPAs were continuously distributed on the anterior roof of the LA where both the LGE-entropy and LGE-volume ratio were higher than 5.7 and 10%, respectively. The fibrotic tissue properties could be considered heterogenous fibrotic properties (G2).