1. Dynamic Ranges of Contact Force During Radiofrequency Ablation
U. Boles MD, A. Enriquez MD, D. Riegert PhD, A. Ghassemian B.H. Sc, H.Abdollah MD, C. Simpson MD, B Glover MD, K. Michael MD, A. Baranchuk MD, D. Redfearn MD
Division of Cardiology, Heart Rhythm Service, Queen’s University, Kingston, Ontario, Canada.
Background and Objective: Catheter-tissue contact is an important criterion for lesion formation during ablation, the role of dynamic range is poorly understood. We aimed to assess the dynamic ranges for contact force (CFdf) in order to achieve effective lesions according to anatomic variables under conscious sedation.
Methods:
We retrospectively studied 674 radiofrequency lesions (21 procedures) at Kingston General Hospital. A force-sensing catheter was used to continuously record CF data and force time integral (FTI) during each lesion.
For each RF application the following data were extracted: application duration, average CF, temperature, maximum CF, minimum CF and force – time integral (FTI). Dynamic range for contact force represents the difference between maximum and minimum contact force through the whole lesion.
Dynamic range for contact force (CFdf) represents the difference between the highest and lowest recorded contact force for each RF application.
We included lesions when duration of ablation reached 20 seconds or more.
Figure 2: Differences between median and mean dynamic range of contact force in a) Left atrium and right atrium; b) left pulmonary vein and right pulmonary vein; c) roof of left atrium and cavo tricuspid isthmus.
Figure 1: This represents the mean ± SD of contact force dynamic ranges in different right and left anatomical locations. R.LW = right lateral wall, L.RF = left atrial roof, L.PW= left atrial posterior wall, LPV= left pulmonary vein antrum, RPV = right pulmonary vein antrum.
Results:
Of 674 applications, 438 (65 %) met the inclusion criterion.
CF df were significantly greater in the left atrium compared with the right (36.6 ± 20.3 Vs ± 16.4, p < 0.01).
Except CTI, when comparing FTI lesions achieving 400 g/s or not, achieving a value > 400g/s was associated with higher CFdf in all anatomical locations, reaching statistical significance on the right atrial free wall, left atrial posterior wall and right pulmonary vein antrum (P = 0.011, 0.007, and <0.001).
However when examined as a whole, higher CFdf was an independent predictor for less successful lesions in stepwise regression model.
Left atrial enlargement above 46 mm was associated with lower CFdf, CFav and CFmax (p = 0.04, <0.001 and 0.02 respectively)
LA diameter
≤ 46 mm
(N = 214)
> 46 mm
(N = 168)
P value
LAVI ≤ 33 ml/m3
LAVI > 33 ml/m3
CF df (g)
35.07 ± 16.23
± 14.77
0.04
31.36 ± 15.94
34.08 ± 15.46
0.23
CF av (g)
± 8.20
± 6.98
< 0.001
17.86 ± 8.77
± 7.45
0.01
CF max (g)
42.52 ± 17.23
± 15.57
0.02
36.74 ± 16.42
42.01 ± 16.41
0.03
Conclusion:
A significant variation in the dynamic ranges of contact forces were associated with different anatomic locations. We found that the greater the dynamic range the less likely the lesion would reach 400g/s. Smaller atria were associated with higher dynamic ranges and greater peak and average forces.
Table: Comparison of the dynamic range (CF df) average (CF av) and maximum (CF max) contact force according to the left atrial size in (mm) and left atrial volume index (LAVI) (ml/m3).