Fig. 6.

Typical trial in experimental group 4, internal irrigation design, blood flow =0.26 m/sec. Note that T₀ rises rapidly to boiling, at which point it abruptly deflects downward. This deflection was coincident with the sudden elaboration of echocardiographic bubbles at the electrode–endocardial interface and an audible “pop,” not associated with a significant impedance rise. Trials stopped at this instant (data not shown) showed displacement of the interface thermocouple to a site adjacent to the interface. After a few seconds, T₀ resumes its rise, but at a much slower rate. Note that despite the evidence of electrode–endocardial interfacial boiling, continued RF application is associated with progressive rise in intramural temperatures. Impedance rise subsequently reaches 10 ohms, precipitating premature generator shutoff.