Atrial Lesion Set Analysis
Table 1 summarizes all atrial lesion sets by CTC cohort. LTC and HTC pre-ablation LIs were within the intended ranges for the attempted lesion sets. All LTC and HTC intercaval lines (Acute: LTC n=3, HTC n=2; Chronic: LTC n=1, HTC n=1) and PVIs (Acute: n=4 LTC, n=4 HTC; Chronic: n=1 LTC, n=1 HTC) resulted in acute and chronic conduction block. NTC intercaval lines (HTC lesions interposed by 1-2 NTC lesions, Acute: n=3) resulted in visible gaps where NTC lesions were placed, and 0% conduction block.
Figure 4 displays representative acute and chronic maps and chronic histology for LTC and HTC intercaval lines. In both cohorts, the low-voltage area (<0.1mV) produced acutely corresponded to persistent low voltage and expansion of the low-voltage area after 30 days, reflected in gross pathological width measurements (LTC acute: 21.8±4.5mm vs chronic: 37.8mm; HTC acute: 23.8±3.4mm vs chronic: 43.2mm). No statistical difference was identified between acute LTC and HTC intercaval widths (p=0.62). Histologically, sections showed similar morphological changes and tissue composition for LTC and HTC chronic atrial lesion sets. Acute atrial tissue showed necrotic cardiomyocytes, early-stage fibrosis, and sparing of blood vessels (Figure 4, 1B & 2B ). Chronic histological sections revealed complete transmural lesions and clear distinction between healthy and ablated myocardium at the border zone (Figure 4, 1D and 2D ) with complete fibrotic and fatty tissue replacement of the cardiomyocytes within the ablated region (Figure 4, 1E and 2E ).
Figure 5 shows an example of the NTC intercaval line. Pre-ablation LI was significantly different between NTC and HTC regions (∆10±4Ω vs ∆35±8Ω, p=0.03). The site of the NTC lesion shows a distinct unaffected high-voltage area (≥1mV) in comparison to the surrounding low-voltage ablated regions (<0.1mV) (Figure 5A ). Gross pathology of all NTC intercaval lines revealed unaffected myocardium in the areas of NTC lesions (Figure 5C ). Histological analysis revealed necrotic myocardium noted by contraction band necrosis, cell shrinkage, and irregular morphology on the transmural ablated HTC region (Figure 5B ) versus healthy myocardium on the NTC region (Figure 5D ).