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A multi-centre experience of ablation index for evaluating lesion delivery in cavotricuspid isthmus dependent atrial flutter
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  • Edd Maclean,
  • Ron Simon,
  • Richard Ang,
  • Gurpreet Dhillon,
  • Syed Ahsan,
  • Fakhar Khan,
  • Mark Earley,
  • Pier Lambiase,
  • James Rosengarten,
  • Anthony Chow,
  • Mehul Dhinoja,
  • Rui Providencia,
  • Vias Markides,
  • Tom Wong,
  • Ross Hunter,
  • Jonathan Behar
Edd Maclean
Queen Mary University of London
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Ron Simon
Barts Health NHS Trust
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Richard Ang
Saint Bartholomew's Hospital
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Gurpreet Dhillon
Saint Bartholomew's Hospital
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Syed Ahsan
Saint Bartholomew's Hospital
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Fakhar Khan
Barts Health NHS Trust
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Mark Earley
Barts Health NHS Trust
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Pier Lambiase
Saint Bartholomew's Hospital
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James Rosengarten
Saint Bartholomew's Hospital
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Anthony Chow
Barts Health NHS Trust
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Mehul Dhinoja
Barts and The London NHS Trust
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Rui Providencia
Saint Bartholomew's Hospital
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Vias Markides
Royal Brompton and Harefield NHS Foundation Trust
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Tom Wong
Royal Brompton and Harefield NHS Foundation Trust
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Ross Hunter
Barts Health NHS Trust
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Jonathan Behar
Royal Brompton and Harefield NHS Foundation Trust
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Abstract

Introduction Anatomical studies demonstrate significant variation in cavotricuspid isthmus (CTI) architecture. We hypothesised that ablation index (AI) may further our understanding of energy delivery across the CTI. Methods 38 patients underwent CTI ablation at two Cardiothoracic hospitals. Operators delivered 682 lesions in total with a target AI of 600Wgs. Ablation parameters were recorded every 10-20ms. Post hoc, Visitags were trisected according to CTI position: inferior vena cava (IVC), middle (Mid), or ventricular (V) lesions. Results There were no complications. 97.4% of patients (n=37) remained in sinus rhythm at 6.6±3.3 months’ follow-up. For the whole CTI, peak AI correlated with mean impedance drop (ID) (R2=0.89, p<0.0001). However, analysis by anatomical site demonstrated a non-linear relationship Mid CTI (R2=0.15, p=0.21). Accordingly, whilst mean AI was highest Mid CTI (IVC: 473.1±122.1 Wgs, Mid: 539.6±103.5 Wgs, V: 486.2±111.8 Wgs, ANOVA p<0.0001), mean ID was lower (IVC: 10.7±7.5Ω, Mid: 9.0±6.5Ω, V: 10.9±7.3Ω, p=0.011), and rate of ID was slower (IVC: 0.37±0.05 Ω/s, Mid: 0.18±0.08 Ω/s, V: 0.29±0.06 Ω/s, p<0.0001). Mean contact force was similar at all sites, however temporal fluctuations in contact force (IVC: 19.3±12.0mg/s, Mid: 188.8±92.1mg/s, V: 102.8±32.3mg/s, p<0.0001) and catheter angle (IVC: 0.42°/s, Mid: 3.4°/s, V: 0.28°/s, p<0.0001) were greatest Mid CTI. Use of a long sheath attenuated these fluctuations and improved ablation efficacy. Conclusions Ablation characteristics vary across the CTI. At the Mid CTI, operators should appreciate that higher AI values do not necessarily deliver more effective ablation; this may be explained by localised fluctuations in catheter angle and contact force.