Prediction of atrial wall electrical reconnection based on contact force measured during RF ablation

Abstract

A method and device for determining the transmurality and/or continuity of an isolation line formed by a plurality of point contact ablations. In one embodiment, a method for determining the size of a lesion (width, depth and/or volume) is disclosed, based on contact force of the ablation head with the target tissue, and an energization parameter that quantifies the energy delivered to the target tissue during the duration time of the lesion formation. In another embodiment, the sequential nature (sequence in time and space) of the ablation line formation is tracked and quantified in a quantity herein referred to as the “jump index,” and used in conjunction with the lesion size information to determine the probability of a gap later forming in the isolation line.

1 . A method for automatically controlling an ablation catheter, comprising:
 providing an elongate flexible catheter, said catheter including a distal portion having an ablation head and a force sensor and operatively coupled with an energy source and an energization parameter measuring device;   providing instructions for introducing said catheter into a patient during a medical procedure and guiding said distal portion of said catheter so said ablation head of said catheter is exerted against a first target tissue location;   automatically energizing said ablation head with said energy source over a period of time while said ablation head is exerted against said first target tissue location;   measuring a sequence of energization parameters with said energization parameter measuring device while said ablation head is energized;   measuring a sequence of contact forces with said force sensor while said ablation head is energized, said contact forces being in reaction to said ablation head exerted against said target tissue;   automatically determining a lesion size based on said sequence of contact forces and said sequence of said energization parameters over said period of time; and   automatically generating control information based on said lesion size for use in guiding said ablation head to a second and subsequent target tissue location.   
     
     
         2 . The method of  claim 1 , wherein said determination of lesion size includes determining a joule heating component and a diffusive heating component. 
     
     
         3 . The method of  claim 1 , wherein the energization parameter of said sequence of energization parameters is electrical current. 
     
     
         4 - 11 . (canceled) 
     
     
         12 . A method for determining the continuity of an isolation line formed by point contact ablation in a region of the human heart, comprising:
 providing an elongate flexible catheter, said catheter including a distal portion having an ablation head operatively coupled with an energy source, a force sensor and a position sensing device, said energy source, said force sensor and said position sensing device being operatively coupled with a processor;   configuring said processor to:
 provide instructions for forming a plurality of lesions substantially along a desired ablation line with said ablation head, 
 sense the location of each of said plurality of lesions with said position sensing device during the forming of said plurality of lesions, 
 determine if a jump occurred between each consecutively formed pair of lesions of said plurality of lesions, said jump being defined by a predetermined criteria of spatial separation between the lesions of said consecutively formed pairs of lesions, and 
 increment a jump index for each jump detected in the formation of said plurality of lesions; and 
   determining a probability of gap formation along said isolation line based on said Limp index and said force data.   
     
     
         13 . The method of  claim 12 , wherein said predetermined criteria for determining if a jump occurred is based on a zoned accounting method wherein said isolation line is divided into adjacent zones and said jump is established when consecutively formed lesions are created in non-adjacent zones. 
     
     
         14 . A method of forming an isolation line in a region of a human heart, comprising:
 providing an elongate flexible catheter adapted to be introduced into a patient during a medical procedure, said catheter including a distal portion having an ablation head operatively coupled with a force sensor, a position sensing device and a control system having a processor, said processor being operatively coupled with said force sensor, said position sensing device and a receiving device, said processor having access to a storage medium that contains programming instructions to be executed by said processor, said programming instructions including:   determining an actual location of a first lesion of said isolation line;   calculating a desired location for a second lesion, said desired location of said second lesion being proximate to and based on said actual location of said first lesion;   generating an instruction to position said ablation head at said desired location of said second lesion; and   sending said instruction to position said ablation head at said desired location of said second lesion to said receiving device.   
     
     
         15 . The method of  claim 14 , further comprising:
 providing an energy source operatively coupled with an energization parameter measuring device, said energy source further being operatively coupled with said ablation head and said processor; and   additional programming instructions contained on said storage medium to be executed by said processor, said additional programming instructions including:
 energizing said ablation head with said energy source for formation of said second lesion; 
 acquiring position data from said position sensing device during formation of said second lesion; 
 acquiring force data from said force sensor during formation of said second lesion; 
 acquiring energization parameter data from said energization parameter measuring device during formation of said second lesion; and 
 acquiring duration time data for formation of said second lesion. 
   
     
     
         16 . The method of  claim 15 , wherein said first and second lesions are formed sequentially in time, without formation of other lesions therebetween. 
     
     
         17 . The method of  claim 15 , further comprising storing said position data, said force data, said energization parameter data and said duration time data to a data storage device. 
     
     
         18 . The method of  claim 15 , wherein said energization parameter measuring device provided in said step of providing said energy source is adapted to measure electrical current. 
     
     
         19 . The method of  claim 15 , wherein said programming instructions further comprise:
 determining an actual location of said second lesion from said position data acquired during formation of said second lesion,   calculating a desired location for a third lesion, said desired location of said third lesion being proximate to and based on said actual location of said second lesion;   generating an instruction to position said ablation head at said desired location of said third lesion; and   sending to said receiving device said instruction to position said ablation head at said desired location of said third lesion.   
     
     
         20 . The method of  claim 19 , further comprising
 inferring an estimated size of said second lesion based on said force data and said duration time data; and   calculating said desired location for said third lesion based on said estimated size of said second lesion.   
     
     
         21 . The method of  claim 14 , wherein said location of said first lesion is proximate a desired ablation line, and wherein said desired location for said second lesion is based on a location of said desired ablation line. 
     
     
         22 . The method of  claim 14 , further comprising:
 after said step of sending said instruction, monitoring said position sensing device to track movement of said distal portion of said elongate flexible catheter; and   from said monitoring of said position sensing device, determining when said ablation head is within a predetermined distance of said desired location of said second lesion.   
     
     
         23 . The method of  claim 14 , wherein said receiving device is a robotic manipulator. 
     
     
         24 . The method of  claim 14 , wherein said desired location of said second lesion is sufficiently close to said first lesion for continuity between said first and second lesions if said second lesion is formed at said desired location. 
     
     
         25 . The method of  claim 24 , wherein said second lesion physically overlaps said first lesion if said second lesion is formed at said desired location. 
     
     
         26 . The method of  claim 14 , wherein said first lesion is located proximate a pulmonary vein.