Implantable cardioverter defibrillator designed for use in a magnetic resonance imaging environment

Abstract

An implantable cardioverter defibrillator includes a communication interface operable to receive a communication signal from an external programmer. The communication signal includes a command to switch the ICD from a first mode to a second mode. A processor is in electrical communication with the communication interface and configured to switch the ICD between the first and second modes. A battery is configured to supply low DC voltage. A converter is configured to convert the low DC voltage to a high DC voltage. An energy storage capacitor is electrically coupled to the converter and configured to store a therapeutic energy or high DC voltage including at least 15 joules. The second mode includes activating the converter to convert the low DC voltage to the high DC voltage and storing the therapeutic energy or at least 15 joules within the energy storage capacitor during a period of time of the second mode.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS[0001]This utility application claims priority to provisional application 61 / 525,235 filed on Aug. 19, 2011.DESCRIPTION FIELD OF THE INVENTION[0002]The present invention generally relates to implantable cardioverter defibrillators. More particularly, the present invention relates to an implantable cardioverter defibrillator that can operate during medical diagnostic procedures such as magnetic resonant imaging.BACKGROUND OF THE INVENTION[0003]Magnetic resonance imaging (MRI) is an efficient technique used in the diagnosis of many disorders, including neurological and cardiac abnormalities and other diseases. MRI has achieved prominence in both the research and clinical arenas. It provides a non-invasive method for examining internal body structures and functions. Because MRI has become such a useful diagnostic tool, it now is used extensively in hospitals and clinics around the world.[0004]Magnetic resonance imaging equipment produces three mai...

AI Technical Summary

Benefits of technology

The patent describes an implantable cardioverter defibrillator (ICD) that can be switched between different modes using an external programmer. The ICD includes a housing and a communication interface for receiving the programming signals. The processor within the housing switches between the modes based on the programming signals. The ICD also includes a battery, a DC to AC converter, a transformer, a rectifier, a high voltage switch, a bleed off circuit, and an energy storage capacitor to store and deliver the necessary defibrillation energy. The ICD can provide therapeutic cardioversion or defibrillation shocks while in the presence of an MRI field. The patent also describes variations of the ICD that include a magnetic field sensor to automatically terminate the secondary mode and a timer to measure the period of time in the second mode. The communication interface can receive a second communication signal from the external programmer to switch the ICD between the modes. Overall, the patent provides technical means for switching between different modes and providing effective defibrillation therapy in an implantable medical device.

Problems solved by technology

These strong electromagnetic fields produced by MRI systems can cause problems for implantable medical devices and as a result, both the U.S. Food and Drug Administration (FDA) and many pacemaker manufacturers have issued warnings against pacemaker recipients undergoing MRIs.

More specifically, it has been documented that implantable cardioverter defibrillators (ICDs) can exhibit a number of malfunctions when placed inside of a clinical MRI scanner bore.

In the presence of the main static B0 field of the MR scanner, these ferrite or iron materials saturate and become very inefficient.

It has been documented, that the charging transformer of an ICD will saturate during an MRI scan thereby making it impossible to charge up the ICD's high energy storage capacitor to a high enough voltage level.

In this case, the ICD senses a chaotic heart rhythm, however, due to the saturation of the ferrite element(s), the ICD energy storage capacitor is only charged to a relatively low voltage.

In fact, there have been cases of the ICD attempting to deliver so many shocks that it depletes its own battery before the MRI scan is even completed.

In addition, the MRI environment can be a very stressful environment for many patients.

In a high risk patient, the chance for a dangerous arrhythmia increases when the patient is in the MRI bore.

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