Comparison of ablation index versus time-guided radiofrequency energy dosing using normal and half-normal saline irrigation in a porcine left ventricular model

J Cardiovasc Electrophysiol. 2022 Apr;33(4):698-712. doi: 10.1111/jce.15379. Epub 2022 Jan 30.


Background: Ablation Index (AI) is a multiparametric quality marker to assess the durability of radiofrequency (RF) lesions. The comparative effectiveness and safety of AI versus time-based energy dosing for ablation of ventricular arrhythmias are unknown.

Objective: We compared AI and time-based RF dosing strategies in the left ventricles (LVs) of freshly harvested porcine hearts.

Methods: Ablation was performed in vitro with an open-irrigated ablation catheter (Thermocool ST/SF), 40 W, contact force 10-15 g. Tissue samples were stained in triphenyltetrazolium chloride for the measurement of lesion dimensions.

Results: A total of 560 lesions were performed (AI-group: [n = 360]; time-group: [n = 200]). Using normal saline (NS) (n = 280), growth in lesion depth slowed after 30 s and AI > 550 in comparison to width, volume, and magnitude of impedance drops which continued to increase with longer RF duration. Risk of steam pop (SP) was higher for RF > 30 s (RF < 30 s:1 SP [2.5%] vs. RF > 30 s: 15 SP [25%]; p = .002) or AI targets >550 (AI: 350-550: 2 SP [2%] vs. AI 600-750: 15 SP [19%]; p = .001). Using half-normal saline (HNS) (n = 280), lesion dimension and impedance drops were larger and growth in lesion depth slowed earlier (AI: 500). Risk of SPs was higher above AI 550 (AI: 350-550: 7 [7%] SPs vs. AI 600-750: 28 [35%] SPs; p < .00001). While codependent variables, correlation between AI and time was modest-to-strong but decreased with longer RF duration.

Conclusion: In this ex vivo study, AI was a better predictor of lesion dimensions than ablation time and magnitude of impedance drop in the LV using NS and HNS irrigation. AI targets above 550 led to a higher risk of SPs. Future trials are required to verify these findings.

Keywords: ablation index; catheter ablation; half normal saline; ventricular tachycardia.

MeSH terms

  • Animals
  • Catheter Ablation* / adverse effects
  • Catheter Ablation* / methods
  • Equipment Design
  • Heart
  • Heart Ventricles / pathology
  • Heart Ventricles / surgery
  • Saline Solution*
  • Swine
  • Therapeutic Irrigation / adverse effects
  • Therapeutic Irrigation / methods


  • Saline Solution