Patent ID: 6501989
Filing Date: 2002-12-31
Classification: A61B,A61N

Abstract:
A heart stimulator comprising:a pulse generator which emits stimulation pulses, each having an amplitude; an electrode lead connected to said pulse generator and adapted for introduction into a patient to deliver said stimulation pulses to the patient's heart, and for picking up respective signals representing polarization of the heart immediately after each of said stimulation pulses; a control unit connected to said pulse generator for controlling said pulse generator to emit said stimulation pulses with respectively different amplitudes, including a high amplitude stimulation pulse preceding a low amplitude stimulation pulse, said low amplitude stimulation pulse having an amplitude equal to a known stimulation threshold voltage plus a predetermined voltage step, and said high amplitude stimulation pulse having an amplitude above the amplitude of said low amplitude stimulation pulse; an evoked response detector including a measurement and memory unit connected to said electrode lead, a calculating unit connected to an output of said measurement and memory unit, and an analyzing unit connected to an output of said calculating unit; said measurement and memory unit measuring and storing respective signals picked up by said electrode lead immediately after said high amplitude stimulation pulse and said low amplitude stimulation pulse, as well as measuring and storing respective signals picked up said electrode lead immediately following respective subsequent stimulation pulses emitted after said low amplitude stimulation pulse; said calculating unit determining a first difference between the respective signals picked up by said electrode lead immediately after said high amplitude stimulation pulse and said low amplitude stimulation pulse, a second difference between the amplitude of said high amplitude stimulation pulse and the amplitude of said low amplitude stimulation pulse, and a quotient of said first difference and said second difference; and said analyzing unit determining whether an evoked response has occurred to respective ones of said subsequent stimulation pulses by, for each subsequent stimulation pulse, determining a polarization signal by multiplying the amplitude of the subsequent stimulation pulse by said quotient, and subtracting said polarization signal from the signal picked up by the electrode lead immediately following the subsequent stimulation pulse.