Control of arbitrary waveforms for constant delivered energy

• US 7,151,963 B2
• Filed: 12/03/2002
• Issued: 12/19/2006
• Est. Priority Date: 12/03/2001
• Status: Active Grant

• Current Assignee: Medtronic Incorporated (Medtronic Plc)
• Original Assignee: Medtronic Incorporated (Medtronic Plc)
• Inventors: Havel, William J., DeGroot, Paul J., Kemmetmueller, Gary, Kuehn, Kevin, Sinner, Thomas W., Wold, Warren W.
• Primary Examiner(s): Pezzuto, Robert E.
• Assistant Examiner(s): Patel, Joy
• Application Number:
  US10/308,832
• Publication Number:
  US 20030125773A1
• Time in Patent Office: 1,477 Days
• Field of Search: 607/28, 600/547
• US Class Current: 607/5
• CPC Class Codes: A61N 1/3906 characterised by the form of the shockwave
• CPC Class Codes: A61N 1/3912 Output circuitry therefor, e.g. switches
• CPC Class Codes: A61N 1/3937 Monitoring output parameters

Abstract

The present invention outlines structures and methods for delivering a controllable amount of energy to a patient by automatically compensating for the load impedance detected by an implantable-cardioverter defibrillator (ICD). The invention employs high speed, switching power converter technology for the efficient generation of high energy, arbitrary waveforms. Unlike a linear amplifier, switching power converters deliver high-energy waveforms with an efficiency that is independent of the size and amplitude of the desired waveform. An ICD that uses a switching power converter to deliver the desired energy to the patient stores the energy to be delivered in a storage capacitor. The converter then transforms this energy into an arbitrarily shaped output voltage-controlled or current-controlled waveform by switching the storage capacitor in and out of the output circuit at a high rate of speed. Preferably, the waveform comprises a ramp-type waveform.

Claims

1. A system for controlling waveform to deliver constant energy from a device to terminate a cardiac fibrillation condition, the system comprising:

means for measuring a load impedance of a subsystem between at least a pair of electrodes over a duration to deliver an initial portion of energy via a mono-phasic ramp-type waveform beginning from an essentially null amplitude;

means for measuring a length of time it takes a storage capacitor voltage to decay by a certain percentage; and

means for calculating the impedance of the load that a voltage-controlled or current-controlled output mono-phasic ramp-type waveform is delivered into based on the length of time;

means for extending a delivery time interval that the voltage-controlled or current-controlled output waveform requires to deliver a pre-programmed total amount of energy irrespective of the load impedance, wherein said amount of energy includes the initial portion of energy; and

means for truncating the mono-phasic ramp-type waveform to the essentially null amplitude.

2. A system according to claim 1, wherein said means for extending comprises a power converter circuit.

3. A system according to claim 1, wherein said one of said at least a pair of electrode comprises a portion of an electrically conducting canister for an implantable medical device.

4. A system according to claim 1, wherein said pre-programmed amount of energy is a set of discrete pro-programmed energy levels and each successive member of said set has a greater magnitude than the previous member of said set.

5. A system according to claim 1, wherein said voltage-controlled or current-controlled output waveform is at least a one of the following waveforms:

an ascending amplitude waveform or a descending amplitude waveform.

6. A system according to claim 1, wherein said means for extending the voltage-controlled or current-controlled output waveform comprises a switching converter.

7. A system according to claim 6, wherein the switching converter comprises at least a one of the following:

a step-down (buck) converter, a step-up (boost) converter, a combined step-down/step-up (buck-boost) converter.

8. A system according to claim 1, wherein the pair of electrodes comprises at least one of the following:

a percutaneous electrode, a subcutaneous electrode, an epicardial electrode, an endocardial electrode, a transcutaneous electrode, a surface electrode, a canister electrode, a coil electrode, a ring electrode.