EHRA educational review and preparatory course for accreditation examination Invasive Cardiac Electrophysiology examination preparatory course Basic concepts, techniques and safety issues of arrhythmia ablation Prof. Dr. M. Antz Oldenburg Heart Center, Germany European Heart House Sophia-Antipolis, France 25th of February, 2011: 9:00-10:30 Matthias Antz
RFC is passed through the patient circuit. The tissue around the probe tip is heated by the electric current. How RF ablation works Power The rise in tissue temperature causes a lesion and interrupts transmission of myocardial signals. The tip does not get hot itself. The temperature rise takes place directly in the tissue and is measured in the tip by a Thermocouple: exactly in the center of a full metal tip for best thermal conductivity or Thermistor: compatible with older generator technologies
Tissue Heating Heat lost to circulating blood Electrode tip heated from the tissue Zone of resistive heating Zone of conductive heating Huang and Wilber: Radiofrequency Catheter Ablation of Cardiac Arrhythmias Futura Publishing 2000
Current flow The current follows two pathways: blood and tissue, each with different impedance (R) R Blood is smaller than R Tissue most current ist lost to blood Good wall contact more contact area more current enters the tissue
Temperature controlled ablation Effects of low and high blood flow Low blood flow: target temperature reached with 15 W small lesion High blood flow: target temperature reached with 30 W large lesion
Conventional Electrodes: 4 mm vs 8 mm Tip 18 W 35 W* 60 60 4 mm Tip 8 mm Tip Electrode Electrode Blood Flow: 350 ml/min * p<0.05 vs 4mm Tip Otomo et al: JCE 1998;9:47-54
Experimental Experience 1) High blood flow allows higher power delivery to the tissue and this results in deeper lesions 2) Larger electrodes provide greater electrode cooling allowing higher power delivery and this results in deeper lesions 3) Small electrodes have a higher recording resolution
Different electrodes 4mm 8mm irrigated Recording resolution high low high Risk of thrombus high high low Large lesions possible no yes yes
Irrigated tip ablation Lesion size
Irrigated Tip Ablation Lesion shape
Ablations using irrigated tip (Oldenburg) Irrigation flow - mapping: 2 ml/min - ablation: 17 ml/min (<30W) - ablation: 30 ml/min ( 30W) Power control - CS/MCV: 10 W (increase in 5 W steps) - other parts: 30 W (max. 40 W, caveat 50W) Temperature limit: 43 C Duration of ablation: 120 sec Cave: volume overload due to irrigation fluid
Matsudaira, Nakagawa et al., NASPE 1999 Effect of Irrigation Flow on Ablation (50W, 60s) 3.5 mm Irrigated Tip Electrode (7F) Irrigation Flow 10ml/min 17ml/min 30ml/min 60ml/min Electrode Temp. 59 6 C* 47 5 C* 39 3 C* 34 2 C* Thrombus 85%* 33%* 0% 0% Impedance Rise 46%* 13% 0% 0% * p<0.05 between flow rates
Nakagawa et al., Circulation 1998; 98: 458-465 2 mm versus 5 mm Irrigated Electrode 30 26 W 30 36 W W Irrigated Tip Irrigated Tip 2 mm 5 mm
Nakagawa et al., Circulation 1998; 98: 458-465 Circuit for RF Ablation RF Generator 50 V Ablation Electrode Blood R Tissue RBlood Blood Tissue R Remote perpendicular 2 mm 5 mm R Remote 30 W 30 W R Tissue 199 W 198 W R Blood 103 W 50 W
Summary RFC heats the tissue, which then heats the ablation electrode Blood flow and electrode-tissue contact have the largest impact on lesion formation during conventional RFC ablation During ablation the electrode temperature, power and impedance should be monitored Risk of thrombus formation is increased at high electrode temperatures High electrode temperatures predominantely occur at high power and can be avoided by using an irrigated tip electrode Matthias Antz
Literature 1. Antz M, Otomo K, Yamanashi WS, Nakagawa H, Jackman WM, Kuck KH: Radiofrequency current catheter ablation with the split tip electrode in the temperature controlled mode. Pacing Clin Electrophysiol 2001: 24(12):1765-1773. 2. Dorwarth U, Fiek M, Remp T, Reithmann C, Dugas M, Steinbeck G, Hoffmann E: Radiofrequency Catheter Ablation: : Different Cooled and Noncooled Electrode Systems Induce Specific Lesion Geometries and Adverse Effect Profiles. PACE 2003;26:1438-45 3. Huang and Wilber: Radiofrequency Catheter Ablation of Cardiac Arrhythmias Futura Publishing 2000 4. Matsudaira K, Nakagawa H, Wittkampf FH, Yamanshi WS, Imai S, Pitha JV, Lazzara R, Jackmann WM, High incidence of thrombus formation without impedance rise during radiofrequency ablation using electrode temperature control. Pacing Clin Electrophysiol 2003;26(5):1227-37 5. Nakagawa H, Wittkampf FHM, Yamanashi WS, Pitha JV, Imai S, Campbell B, Arruda M, Lazzara R, Jackman.WM Inverse Relationship Between Electrode Size and Lesion Size During Radiofrequency Ablation With Active Electrode Cooling. Circulation. 1998;98:458-465 6. Otomo K, Yamanashi WS, Tondo C, Antz M, Bussey J, Pitha JV, Arruda M, Nakagawa H, Wittkampf FH, Lazzara R, Jackman WM: Why a large tip electrode makes a deeper radiofrequency lesion: effects of increase in electrode cooling and electrode-tissue interface area. J Cardiovasc Electrophysiology 1998;9(1):47-54. 7. Petersen HH, Chen X, Pietersen A, Svendsen JH, Haunso S: Lesion Dimensions During Temperature-Controlled Radiofrequency Catheter Ablation of Left Ventricular Porcine Myocardium: Impact of Ablation Site, Electrode Size, and Convective Cooling. Circulation 1999;99:319-25 8. Rodriguez LM, Nabar A, Timmermans C, Wellens HJJ: Comparison of results of an 8-mm split-tip versus a 4-mm Tipp ablation catheter to perform radiofrequency ablation of type I atrial flutter. Am J Cardiol 2000;85(1):109-112 9. Rosenbaum R, Greenspon AJ, Smith M, Walinsky P: Advances radiofrequency catheter ablation in canine myocardium. Am Heart J 1994;127(4):851-857 10. Weiss C, Antz M, Eick O, Eshagzaiy K, Meinertz T, Willems S: Radiofrequency catheter ablation using cooled electrodes: impact of irrigation flow rate and catheter contact pressure on lesion dimensions. Pacing Clin Electrophysiol 2002;25(4):463-469 Matthias Antz