Ultrasound cardiac stimulator

Abstract

An ultrasound cardiac stimulation system comprising: a spatially selective ultrasound source comprising at least one ultrasound transducer located outside the circulatory system; and a controller; where the controller generates an electrical response in the heart by directing the ultrasound source to transmit a high enough power level of ultrasound to one or more locations in the heart.

1 . A method of stimulating at least one location in the heart of a patient, comprising:
 selecting at least one location in the heart;   selecting an ultrasound source configured to transmit at least one ultrasound pulse to said at least one location, said at least one ultrasound pulse configured to create a propagating action potential in cardiac tissue;   aiming said ultrasound source at said at least one location; and   transmitting said at least one ultrasound pulse to said at least one location, said transmitting causing said action potential at said at least one location such that said action potential propagates.   
   
   
       2 . A method according to  claim 1 , wherein timing of said transmitting is coordinated with at least one particular phase of a cardiac cycle of the heart. 
   
   
       3 . A method according to  claim 2 , wherein said timing is coordinated with more than one particular phase of the cardiac cycle of the heart. 
   
   
       4 . A method according to  claim 1 , wherein said propagating action potential produces a mechanical response in the heart. 
   
   
       5 . A method according to  claim 1 , wherein each of said at least one location has a diameter having a measurement approximately equal to that of one wavelength of said ultrasound. 
   
   
       6 . A method according to  claim 1 , wherein each of said at least one location is elliptical. 
   
   
       7 . A method according to  claim 6 , wherein each of said at least one location is 1 to 2 mm in diameter and 4 to 6 mm in length in the direction of propagation. 
   
   
       8 . A method according to  claim 1 , wherein each of said at least one location is 0.5 to 4 mm in diameter and 2 to 10 mm in diameter and 4 to 6 mm in length in the direction of propagation. 
   
   
       9 . A method according to  claim 1 , wherein said ultrasound has a frequency in the range of from 0.5 MHz to 6 MHz. 
   
   
       10 . A method according to  claim 1 , wherein said ultrasound has a frequency of at least 1 MHz. 
   
   
       11 . A method according to  claim 10 , wherein said ultrasound has a wavelength of no more that 1.5 mm. 
   
   
       12 . A method according to  claim 1 , wherein said ultrasound has a peak acoustic pressure in the range of 1 to 5 MPa. 
   
   
       13 . A method according to  claim 1 , wherein said ultrasound has a peak acoustic pressure of greater than 1 MPa. 
   
   
       14 . A method according to  claim 12 , wherein said ultrasound has an acoustic pressure, outside each of said at least one location, which is significantly lower than said peak acoustic pressure. 
   
   
       15 . A method according to  claim 1 , wherein said at least one ultrasound pulse has a duration in the range of 1 to 10 milliseconds long. 
   
   
       16 . A method according to  claim 1 , wherein said at least one ultrasound pulse comprises a sequence of pulses. 
   
   
       17 . A method according to  claim 16 , wherein said sequence of pulses is transmitted to said at least one location at selected phases in a cardiac cycle of the heart, said selected phases being selected to cause cardiac pacemaking. 
   
   
       18 . A method according to  claim 1 , wherein said at least one ultrasound pulse is transmitted to a plurality of locations in the heart approximately simultaneously. 
   
   
       19 . An ultrasound cardiac stimulation system comprising:
 an ultrasound source configured to transmit at least one ultrasound pulse to at least one location in a heart, said at least one ultrasound pulse configured to create a propagating action potential in cardiac tissue.   
   
   
       20 . The system of  claim 19 , wherein said ultrasound source comprises an array of ultrasound transducers. 
   
   
       21 . The system of  claim 20 , wherein said array of ultrasound transducers are disposed at one of outside a chest, between the ribs, below the rib cage, and in the esophagus of a patient. 
   
   
       22 . The system of  claim 20 , wherein said array of ultrasound transducers comprises an imaging system. 
   
   
       23 . The system of  claim 20 , further comprising an imaging system separate from said array of ultrasound transducers. 
   
   
       24 . The system of  claim 1 , wherein said at least one location comprises a plurality of locations. 
   
   
       25 . A method according to  claim 1 , wherein no agent for enhancing said stimulation has been introduced into the heart prior to said transmitting.