Radio-frequency tissue ablation: effect of pharmacologic modulation of blood flow on coagulation diameter

Abstract

Purpose: To determine whether vasoactive pharmacologic agents can alter radio-frequency (RF)-induced coagulation necrosis by modulating hepatic blood flow.

Materials and methods: RF ablation was performed in normal, in vivo porcine liver with 1.5-cm internally cooled electrodes and a standardized RF application (i.e., 500 mA for 10 minutes). Ablation was performed without (n = 9) and with pharmacologic modulation of blood flow with halothane (n = 7), vasopressin (n = 6), or epinephrine (n = 7). Laser Doppler techniques were used to quantify changes in hepatic blood flow. Remote thermometry was also performed. Blood flow was correlated with both induced coagulation necrosis and tissue temperatures.

Results: Halothane reduced mean blood flow (+/- SD) to 46.1% +/- 8.5 of normal, and vasopressin increased mean blood flow to 132.7% +/- 13.9. Epinephrine caused increased hepatic blood flow centrally (171.1% +/- 31.7) but not peripherally (102.8% +/- 15.4). Mean coagulation diameter was 1.4 cm +/- 0.3 with vasopressin, 2.2 cm +/- 0.4 with normal blood flow, and 3.2 cm +/- 0.1 with halothane (P < .01). After epinephrine infusion, mean coagulation measured 2.3 cm +/- 0.3 peripherally and 1.4 cm +/- 0.5 centrally (P < .01). A linear correlation between coagulation diameter and blood flow was demonstrated (r2 = 0.78). Temperatures 10 and 15 mm from the electrode correlated with both blood flow and coagulation diameter (r2 = 0.65 and 0.60, respectively).

Conclusion: The coagulation necrosis achieved for a standardized RF application correlates with relative tissue perfusion. Pharmacologic reduction of blood flow during thermally mediated percutaneous ablation may induce greater coagulation necrosis.