Method for stimulating heart muscle activity during the refractory period

Abstract

A system and method for improving heart contractions during a heart function cycle (heartbeat) of a patient requires detecting a local electrical event (depolarization) during the cycle. This local electrical event is then used to trigger a stimulation interval Δt at a time t 0 . Importantly, the stimulation interval Δt is set to end at a time t 1 during the absolute refractory period of the heart function cycle. At the time t 1 , a stimulator is triggered to stimulate a local sympathetic nerve on the epicardial surface of the heart. With this stimulation the sympathetic nerve secretes norepinephrine to improve a subsequent contraction of the heart.

What is claimed is: 
     
         1 . A method for electrically stimulating a sympathetic nerve of a patient to improve heart function, the method comprising the steps of:
 positioning an electrode in an epicardial vein, on the epicardial surface of the heart adjacent the sympathetic nerve;   detecting a local electrical event with the electrode/sensor, wherein the local electrical event occurs near the electrode/sensor and results from the patient's natural heart muscle cycle;   using the detected local electrical event to trigger a start time t 0 ;   waiting a predetermined time interval Δt after the start time t 0 , until a time t 1 , wherein t 1  is in the absolute refractory period of the patient's natural heart muscle cycle (t 1 −t 0 =Δt); and   activating a stimulator at the time t 1  to electrically stimulate the sympathetic nerve with at least one electrical pulse to improve contractions of the patient's heart muscle.   
     
     
         2 . The method as recited in  claim 1  wherein Δt constitutes a stimulation interval, and the method further comprises the step of consecutively repeating the stimulation interval. 
     
     
         3 . The method as recited in  claim 1  further comprising the steps of:
 deferring the detecting step and the using step; and 
 implementing a pacing device to trigger the start time t 0 . 
 
     
     
         4 . The method as recited in  claim 1  wherein Δt is in a range of 100-120 msec. 
     
     
         5 . The method as recited in  claim 1  wherein the electrical pulse for stimulating the sympathetic nerve has a predetermined intensity less than three times the intensity required for activating a contraction of the heart muscle. 
     
     
         6 . The method as recited in  claim 1  wherein the start time t 0  is triggered by a local electrical event in the patient's heart muscle during a contraction of the heart muscle. 
     
     
         7 . The method as recited in  claim 1  wherein the start time t 0  is triggered by an electrical event in the patient's heart muscle during diastole of the heart muscle. 
     
     
         8 . A device for electrically stimulating a sympathetic nerve of a patient to improve heart function which comprises:
 a sensor for detecting an electrical event of the heart at a time t 0  during the patient's natural heart muscle cycle;   a timer for measuring a stimulation interval having a predetermined time interval Δt between the start time t 0  and a time t 1 , wherein t 1  is in the absolute refractory period of the patient's heart cycle (Δt=t 1 −t 0 ); and   a stimulator connected with an electrode for stimulating the sympathetic nerve with at least one electrical pulse at the time t 1 , to improve a contraction of the heart muscle.   
     
     
         9 . The device as recited in  claim 8  further comprising a deployment catheter for positioning the electrode in an epicardial vein, on the epicardial surface of the heart adjacent the sympathetic nerve. 
     
     
         10 . The device as recited in  claim 8  further comprising:
 a pacing device selectively connected with the stimulator to electronically establish t 0 ; and 
 a switch to selectively alternate between a connection of the stimulator with the sensor and with the pacing device. 
 
     
     
         11 . The device as recited in  claim 10  further comprising:
 a voltage source to generate the electrical pulse at the time t 1 ; and 
 a computer for coordinating an operation of the stimulator with respective operations of the sensor, the pacing device, the switch, and the timer. 
 
     
     
         12 . The device as recited in  claim 8  wherein the electrical pulse for stimulating the sympathetic nerve has a predetermined intensity less than three times the intensity required for activating a contraction of the heart muscle. 
     
     
         13 . The device as recited in  claim 8  wherein Δt constitutes a stimulation cycle, and the stimulation interval is continuously repeated. 
     
     
         14 . The device as recited in  claim 8  wherein the stimulation interval Δt is in a range of 100-120 msec. 
     
     
         15 . The device as recited in  claim 8  wherein the start time t 0  is triggered by an electrical event in the patient's heart muscle during a contraction of the heart muscle. 
     
     
         16 . The device as recited in  claim 8  wherein the start time t 0  is triggered by an electrical event in the patient's heart muscle during diastole of the heart muscle. 
     
     
         17 . A non-transitory, computer readable medium having executable instructions stored thereon that direct a computer system to perform a process which comprises: detecting an electrical event of the heart at a time t 0  during the patient's natural heart muscle cycle; measuring a stimulation interval having a predetermined time interval Δt between the start time t 0  and a time t 1  wherein t 1  is in the absolute refractory period of the patient's heart cycle (Δt=t 1 −t 0 ); and stimulating the sympathetic nerve with at least one electrical pulse at the time t 1  to improve a contraction of the heart muscle, wherein the electrical pulse has a predetermined intensity less than three times the intensity required for activating a contraction of the heart muscle. 
     
     
         18 . The non-transitory, computer-readable medium as recited in  claim 17  further comprising instructions for: selectively alternating between a connection and a disconnection of a sensor for detecting the electrical event, with a stimulator for stimulating the sympathetic nerve; and using a pacing device for establishing t 0  when the sensor is disconnected from the stimulator. 
     
     
         19 . The non-transitory, computer-readable medium as recited in  claim 18  wherein Δt constitutes a stimulation interval, and the stimulation interval is continuously repeated for successive heart muscle cycles, and further wherein the stimulation interval Δt is in a range of 100-120 msec. 
     
     
         20 . The non-transitory, computer-readable medium as recited in  claim 18  wherein the start time t 0  is triggered by an electrical event in the patient's heart muscle during a time period including contraction and diastole.