Combined Local Impedance and Contact Force for Radiofrequency Ablation Assessment.

BACKGROUND: The combination of contact force (CF) and local impedance (LI) may improve tissue characterization and lesion prediction during radiofrequency (RF) ablation. OBJECTIVE: To evaluate the utility of LI combined with CF in assessing radiofrequency ablation efficacy. METHODS: A LI catheter with CF-sensing was evaluated in swine (n=11) and in vitro (n=14). The relationship between LI and CF in different tissue types was evaluated in vivo. Discrete lesions were created in vitro and in vivo at a range of forces, powers, and durations. Finally, an intercaval line was created in three groups at 30W: 30s, Delta20Omega, and Delta30Omega. In the Delta20Omega and Delta30Omega groups, the user ablated until a 20Omega or 30Omega LI drop. In the 30s group, the user was blinded to LI. RESULTS: In vivo, distinction in LI was found between bloodpool and myocardium (bloodpool: 122+/-7.02Omega, perpendicular contact: 220+/-29Omega, parallel contact: 207+/-31Omega). LI drop correlated with lesion depth both in vitro (R=0.84) and in vivo (R=0.79), informing sufficient lesion creation (LI drop>20Omega) and warning of excessive heating (LI drop>65Omega). When creating an intercaval line, total RF time was significantly reduced when using LI guidance (6.4+/-2min in Delta20Omega, 8.1+/-1 min in Delta30Omega) compared to a standard 30s workflow (18+/-7min). Acute conduction block was achieved in all Delta30Omega and 30s lines. CONCLUSION: Addition of LI to CF provides feedback on both electrical and mechanical load. This provides information on tissue type and catheter-tissue coupling, feedback on whether volumetric tissue heating is inadequate, sufficient, or excessive, and reduces ablation time.