Radiofrequency ablation: Effect of pharmacologic modulation of hepatic and renal blood flow on coagulation diameter in a VX2 tumor model.
OBJECTIVE
To determine whether pharmacologic agents can be used to modulate blood flow in hepatic and renal tumors sufficiently to alter the extent of radiofrequency (RF)-induced coagulation.


METHODS
VX2 tumors (8-15 mm) were implanted in the liver (n = 25) or kidney (n = 8) of 33 New Zealand White rabbits. RF was applied to tumors for 6 minutes with use of conventional electrodes (125 mA +/- 35; 90 degrees C +/- 2 degrees C tip temperature). In the hepatic model, blood flow was modulated with use of halothane, epinephrine, or arsenic trioxide (2-6 mg/kg). Laser Doppler flowmetry was used to quantify changes in hepatic blood flow. Correlation of blood flow with induced coagulation diameter was performed. RF ablation was then performed in a renal model with and without arsenic trioxide.


RESULTS
For liver tumors, halothane and arsenic trioxide reduced blood flow to 40.3% +/- 17.8% and 29% +/- 15% of normal, respectively, whereas epinephrine increased blood flow to 207.8% +/- 97.9%. Correlation of blood flow to coagulation diameter was demonstrated (R(2) = 0.40). Coagulation measured 7 mm +/- 1 with epinephrine, 10 mm +/- 1 with normal blood flow, 12 mm +/- 3 with halothane, and 13 mm +/- 3 with arsenic trioxide (P <.04 compared with controls). In the renal model, arsenic trioxide decreased blood flow (44% +/- 16%) and increased coagulation diameter (10.9 mm +/- 1) compared with controls (84% +/- 11% and 7.6 mm +/- 1; P <.01, both comparisons).


CONCLUSIONS
RF-induced coagulation necrosis in rabbit hepatic and renal tumors is affected by tumor blood flow. Pharmacologic modulation of tumor blood flow may provide a noninvasive way to decrease blood flow during thermally mediated ablation therapy, potentially enabling the creation of larger zones of coagulation necrosis.
Horkan
Clare
C
Laboratory for Minimally Invasive Tumor Therapy, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, Massachusetts 02215, USA.
Ahmed
Muneeb
M
Liu
Zhengjun
Z
Gazelle
G Scott
GS
Solazzo
Stephanie A
SA
Kruskal
Jonathan B
JB
Goldberg
S Nahum
SN
D000322:Adrenergic Agonists / Q000494:pharmacology; D018685:Anesthetics, Inhalation / Q000494:pharmacology; D000818:Animals; D000970:Antineoplastic Agents / Q000494:pharmacology; D000077237:Arsenic Trioxide; D001152:Arsenicals / Q000494:pharmacology; D002277:Carcinoma / Q000098:blood supply / Q000601:surgery; D017115:Catheter Ablation / Q000295:instrumentation / Q000379:methods; D004195:Disease Models, Animal; D004837:Epinephrine / Q000494:pharmacology; D006221:Halothane / Q000494:pharmacology; D007668:Kidney / Q000098:blood supply; D007680:Kidney Neoplasms / Q000098:blood supply* / Q000601:surgery; D017078:Laser-Doppler Flowmetry; D008099:Liver / Q000098:blood supply; D008113:Liver Neoplasms / Q000098:blood supply* / Q000601:surgery; D010087:Oxides / Q000494:pharmacology; D011817:Rabbits; D012039:Regional Blood Flow / Q000187:drug effects
D000322:Adrenergic Agonists; D018685:Anesthetics, Inhalation; D000970:Antineoplastic Agents; D001152:Arsenicals; D010087:Oxides; D000077237:Arsenic Trioxide; D006221:Halothane; D004837:Epinephrine