Relationship between catheter contact force and radiofrequency lesion size and incidence of steam pop in the beating canine heart: electrogram amplitude, impedance, and electrode temperature are poor predictors of electrode-tissue contact force and lesion size.
BACKGROUND
Electrode-tissue contact force (CF) is believed to be a major factor in radiofrequency lesion size. The purpose of this study was to determine, in the beating canine heart, the relationship between CF and radiofrequency lesion size and the accuracy of predicting CF and lesion size by measuring electrogram amplitude, impedance, and electrode temperature.


RESULTS
Eight dogs were studied closed chest. Using a 7F catheter with a 3.5 mm irrigated electrode and CF sensor (TactiCath, St. Jude Medical), radiofrequency applications were delivered to 3 separate sites in the right ventricle (30 W, 60 seconds, 17 mL/min irrigation) and 3 sites in the left ventricle (40 W, 60 seconds, 30 mL/min irrigation) at (1) low CF (median 8 g); (2) moderate CF (median 21 g); and (3) high CF (median 60 g). Dogs were euthanized and lesion size was measured. At constant radiofrequency and time, lesion size increased significantly with increasing CF (P<0.01). The incidence of a steam pop increased with both increasing CF and higher power. Peak electrode temperature correlated poorly with lesion size. The decrease in impedance during the radiofrequency application correlated well with lesion size for lesions in the left ventricle but less well for lesions in the right ventricle. There was a poor relationship between CF and the amplitude of the bipolar or unipolar ventricular electrogram, unipolar injury current, and impedance.


CONCLUSIONS
Radiofrequencylesion size and the incidence of steam pop increase strikingly with increasing CF. Electrogram parameters and initial impedance are poor predictors of CF for radiofrequency ablation.
From the Heart Rhythm Institute (A.I., H.N., T.S., R.L., W.M.J.) and Department of Pathology, Veterans Administration Medical Center (J.V.P.), University of Oklahoma Health Sciences Center, Oklahoma City; St. Jude Medical GVA, Geneva, Switzerland (H.L., E.F., A.Y.); and University of Geneva, Geneva, Switzerland (D.C.S.).
Atsushi
A
Ikeda
From the Heart Rhythm Institute (A.I., H.N., T.S., R.L., W.M.J.) and Department of Pathology, Veterans Administration Medical Center (J.V.P.), University of Oklahoma Health Sciences Center, Oklahoma City; St. Jude Medical GVA, Geneva, Switzerland (H.L., E.F., A.Y.); and University of Geneva, Geneva, Switzerland (D.C.S.). hiroshi-nakagawa@ouhsc.edu.
Hiroshi
H
Nakagawa
From the Heart Rhythm Institute (A.I., H.N., T.S., R.L., W.M.J.) and Department of Pathology, Veterans Administration Medical Center (J.V.P.), University of Oklahoma Health Sciences Center, Oklahoma City; St. Jude Medical GVA, Geneva, Switzerland (H.L., E.F., A.Y.); and University of Geneva, Geneva, Switzerland (D.C.S.).
Hendrik
H
Lambert
From the Heart Rhythm Institute (A.I., H.N., T.S., R.L., W.M.J.) and Department of Pathology, Veterans Administration Medical Center (J.V.P.), University of Oklahoma Health Sciences Center, Oklahoma City; St. Jude Medical GVA, Geneva, Switzerland (H.L., E.F., A.Y.); and University of Geneva, Geneva, Switzerland (D.C.S.).
Dipen C
DC
Shah
From the Heart Rhythm Institute (A.I., H.N., T.S., R.L., W.M.J.) and Department of Pathology, Veterans Administration Medical Center (J.V.P.), University of Oklahoma Health Sciences Center, Oklahoma City; St. Jude Medical GVA, Geneva, Switzerland (H.L., E.F., A.Y.); and University of Geneva, Geneva, Switzerland (D.C.S.).
Edouard
E
Fonck
From the Heart Rhythm Institute (A.I., H.N., T.S., R.L., W.M.J.) and Department of Pathology, Veterans Administration Medical Center (J.V.P.), University of Oklahoma Health Sciences Center, Oklahoma City; St. Jude Medical GVA, Geneva, Switzerland (H.L., E.F., A.Y.); and University of Geneva, Geneva, Switzerland (D.C.S.).
Aude
A
Yulzari
From the Heart Rhythm Institute (A.I., H.N., T.S., R.L., W.M.J.) and Department of Pathology, Veterans Administration Medical Center (J.V.P.), University of Oklahoma Health Sciences Center, Oklahoma City; St. Jude Medical GVA, Geneva, Switzerland (H.L., E.F., A.Y.); and University of Geneva, Geneva, Switzerland (D.C.S.).
Tushar
T
Sharma
From the Heart Rhythm Institute (A.I., H.N., T.S., R.L., W.M.J.) and Department of Pathology, Veterans Administration Medical Center (J.V.P.), University of Oklahoma Health Sciences Center, Oklahoma City; St. Jude Medical GVA, Geneva, Switzerland (H.L., E.F., A.Y.); and University of Geneva, Geneva, Switzerland (D.C.S.).
Jan V
JV
Pitha
From the Heart Rhythm Institute (A.I., H.N., T.S., R.L., W.M.J.) and Department of Pathology, Veterans Administration Medical Center (J.V.P.), University of Oklahoma Health Sciences Center, Oklahoma City; St. Jude Medical GVA, Geneva, Switzerland (H.L., E.F., A.Y.); and University of Geneva, Geneva, Switzerland (D.C.S.).
Ralph
R
Lazzara
From the Heart Rhythm Institute (A.I., H.N., T.S., R.L., W.M.J.) and Department of Pathology, Veterans Administration Medical Center (J.V.P.), University of Oklahoma Health Sciences Center, Oklahoma City; St. Jude Medical GVA, Geneva, Switzerland (H.L., E.F., A.Y.); and University of Geneva, Geneva, Switzerland (D.C.S.).
Warren M
WM
Jackman
D000818:Animals; D062906:Cardiac Catheters / Q000009:adverse effects*; D017115:Catheter Ablation / Q000009:adverse effects* / Q000295:instrumentation*; D004285:Dogs; D017097:Electric Impedance; D004566:Electrodes; D022062:Electrophysiologic Techniques, Cardiac; D006352:Heart Ventricles / Q000473:pathology / Q000601:surgery*; D006358:Hot Temperature / Q000009:adverse effects*; D023421:Models, Animal; D009622:Noise; D011237:Predictive Value of Tests; D012307:Risk Factors; D013227:Steam / Q000009:adverse effects*; D013314:Stress, Mechanical; D013817:Thermography; D013997:Time Factors
D013227:Steam
atrial fibrillation; catheter ablation; radiofrequency; ventricular tachycardia