Vacuum-stabilized ablation system

A tissue ablation catheter comprising:

• an elongate catheter body having a central longitudinal axis, the elongate catheter body having at least a first lumen and a second lumen extending through the catheter body, wherein the catheter body is deflectable;
• an ultrasound ablation element positioned within a distal region of the elongate catheter body, the ultrasound ablation element comprising:
• an ultrasound transducer;
• and
• a membrane extending over at least a portion of the ultrasound transducer, thereby defining a cavity between the membrane and the ultrasound transducer,
• wherein the second lumen is coupled to the cavity to define a fluid pathway;
• a first orifice in the elongate catheter body proximal of the ultrasound ablation element and open to the first lumen to define a first vacuum pathway;
• a second orifice in the elongate catheter body distal of the ultrasound ablation element and open to the first lumen to define a second vacuum pathway,
• wherein the fluid pathway is coupled to the second vacuum pathway;
• a flow control apparatus positioned to regulate flow through the second vacuum pathway independent of flow through the first vacuum pathway;
• and
• a fluid flow control apparatus positioned to regulate flow through the fluid pathway into the second vacuum pathway.

A tissue ablation catheter comprising:

• an elongate tubular body having a central longitudinal axis, the elongate tubular body having a proximal end and a distal region, wherein the elongate tubular body is deflectable;
• a vacuum lumen extending through the elongate tubular body from the proximal end to the distal region;
• an irrigation lumen extending through the elongate tubular body from the proximal end to the distal region;
• an ultrasound ablation element positioned within the distal region of the elongate tubular body, the ultrasound ablation element comprising:
• an ultrasound transducer;
• and
• a membrane extending over at least a portion of the ultrasound transducer, thereby defining a cavity between the membrane and the ultrasound transducer,
• wherein the irrigation lumen discharges into the cavity;
• a first vacuum orifice through the elongate tubular body into the vacuum lumen proximal of the ultrasound ablation element;
• a second vacuum orifice through the elongate tubular body into the vacuum lumen distal of the ultrasound ablation element,
• a fluid discharge orifice in communication with the cavity and proximate a junction between the second vacuum orifice and the vacuum lumen;
• and
• at least one means for controlling a flow through one of the first vacuum orifice, the second vacuum orifice, and the fluid discharge orifice independent of others of the first vacuum orifice, the second vacuum orifice, and the fluid discharge orifice.