Abstract: A method and apparatus for improving blood flow to an ischemic region (e.g., myocardial ischemia) a patient is provided. An ultrasonic transducer is positioned proximate to the ischemic region. Ultrasonic energy is applied at a frequency at or above 1 MHz to create one or more thermal lesions in the ischemic region of the myocardium. The thermal lesions can have a gradient of sizes. The ultrasound transducer can have a curved shape so that ultrasound energy emitted by the transducer converges to a site within the myocardium, to create a thermal lesion without injuring the epicardium or endocardium.

Abstract: Systems and methods for assessing the formation of an ice ball during a cryoablation procedure are disclosed. The system includes a reference electrode that is placed in contact with the patient and a cryocatheter having a cryotip. An electronic circuit is connected to both the cryotip and the reference electrode to measure the impedance therebetween which can be used to assess the formation of an ice ball during a cryoablation procedure. An exemplary measurement signal has a frequency of approximately 20 khz and an RMS voltage of approximately 0.5V. With the cryotip positioned proximate the target tissue, a reference impedance is measured. Next, the conductive tip member is placed in contact with the target tissue and cooled to form an ice ball. During cooling, impedance measurement(s) are taken and compared with the reference impedance to assess the formation of the ice ball.

Abstract: A method and apparatus for improving blood flow to an ischemic region (e.g., myocardial ischemia) a patient is provided. An ultrasonic transducer is positioned proximate to the ischemic region. Ultrasonic energy is applied at a frequency at or above 1 MHz to create one or more thermal lesions in the ischemic region of the myocardium. The thermal lesions can have a gradient of sizes. The ultrasound transducer can have a curved shape so that ultrasound energy emitted by the transducer converges to a site within the myocardium, to create a thermal lesion without injuring the epicardium or endocardium.

Abstract: A catheter for ablating internal tissue using radiofrequency (rf) or ultrasonic energy includes a mechanism to cool the catheter's distal tip. The catheter also includes either an rf electrode or an ultrasonic transducer positioned at the tip to direct energy into the internal tissue for tissue ablation. With the distal tip of the catheter positioned adjacent the target tissue, a refrigerant is introduced into the catheter and allowed to expand near the catheter's distal tip. During expansion, the fluid refrigerant transitions from a liquid state to a gaseous state. Latent heat absorbed during the phase transition cools the tip of the catheter to a temperature sufficient to prevent tissue charring and coagulum formation during ablation. In another implementation, the catheter tip is cooled to a temperature sufficient to freeze tissue and create an ice-ball at the catheter tip that stabilizes the tip relative to the target tissue.

Abstract: A method and apparatus for improving blood flow to an ischemic region (e.g., myocardial ischemia) a patient is provided. An ultrasonic transducer is positioned proximate to the ischemic region. Ultrasonic energy is applied at a frequency at or above 1 MHz to create one or more thermal lesions in the ischemic region of the myocardium. The thermal lesions can have a gradient of sizes. The ultrasound transducer can have a curved shape so that ultrasound energy emitted by the transducer converges to a site within the myocardium, to create a thermal lesion without injuring the epicardium or endocardium.