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

1. A method of performing a magnetic resonance imaging (MRI) scan on a patient having an implanted cardioverter defibrillator (ICD), the method comprising the steps of:

a) determining that the ICD comprises a ferrite core high voltage power supply transformer;

b) with the ICD not being in the presence of an MRI field generated by an MRI scanner, sending a communication signal from an external programmer to the ICD, the communication signal being a command pre-charging a high energy storage capacitor of the ICD before the patient undergoes the MRI scan, the command also switching the ICD into an MRI mode, the MRI mode turning off the ICD's sensing functions detecting a dangerous ventricular arrhythmia; connecting sensors to the patient monitoring vital signs of the patient, the sensors displaying the vital signs to an operator on at least one display;

c) moving the patient into the MRI scanner;

d) performing the MRI scan while also monitoring the vital signs of the patient;

e) the operator determining from the display whether the patient requires a defibrillation shock;

f) when the patient requires the defibrillation shock, the operator sending a second communication signal from the external programmer to the ICD, the second communication signal being a second command delivering the defibrillation shock from the pre-charged high energy storage capacitor of the ICD to the patient while in the presence of the MRI field;

g) removing the patient from the MRI scanner after the MRI scan is completed or after the operator has sent the second command where the ICD delivered the defibrillation shock to the patient while in the presence of the MRI field; and

h) moving the patient substantially away from the MRI main static field.

2. The method of claim 1 , including the step of the operator sending a third communication signal from the external programmer to the ICD, wherein the third communication signal comprises a third command to switch the ICD to a non-MRI mode, the non-MRI mode turning on the ICD's sensing functions detecting a dangerous ventricular arrhythmia.

3. The method of claim 2 , including the step of if the ICD has not delivered the defibrillation shock then allowing the ICD to automatically bleed off the charge stored in the high energy storage capacitor, or if the ICD has delivered the defibrillation shock then determining that additional therapy is needed and allowing the ICD to automatically sense the dangerous ventricular arrhythmia and recharge the high energy storage capacitor and automatically delivering a second defibrillation shock to the patient.

4. The method of claim 1 , wherein the second command includes switching the ICD to a non-MRI mode, the non-MRI mode turning on the ICD's sensing function detecting a dangerous ventricular arrhythmia.

5. The method of claim 1 , wherein the second command includes sending an MRI communication signal from the external programmer to the MRI scanner, where the MRI communication signal comprises a command to turn off the RF and gradient fields.

6. The method of claim 1 , wherein the ICD comprises a magnetic field sensor in electrical communication with a processor for the ICD, the processor switching the ICD to a non-MRI mode when the magnetic field sensor detects a lack of a static magnetic field, the non-MRI mode turning on the ICD's sensing function detecting a dangerous ventricular arrhythmia.

7. The method of claim 6 , including the step of if the ICD has not delivered the defibrillation shock then allowing the ICD to automatically bleed off the charge stored in the high energy storage capacitor, or if the ICD has delivered the defibrillation shock then determining that additional therapy is needed and allowing the ICD to automatically sense the dangerous ventricular arrhythmia and recharge the high energy storage capacitor and delivering a second defibrillation shock to the patient.

8. The method of claim 1 , wherein the ICD comprises a magnetic field sensor in electrical communication with a processor for the ICD, the second command directing the processor to switch the ICD to a non-MRI mode when the magnetic field sensor detects a lack of a static magnetic field, the non-MRI mode turning on the ICD's sensing function detecting a dangerous ventricular arrhythmia.

9. The method of claim 8 , including the step of if the ICD has not delivered the defibrillation shock then allowing the ICD to automatically bleed off the charge stored in the high energy storage capacitor, or if the ICD has delivered the defibrillation shock then determining that additional therapy is needed and allowing the ICD to automatically sense the dangerous ventricular arrhythmia and recharge the high energy storage capacitor and delivering a second defibrillation shock to the patient.

10. The method of claim 8 , wherein the static field sensor is selected from the group consisting of a Hall effect sensor, a reed switch, and a MEMS-based magnetic field sensor.

11. The method of claim 1 , wherein monitoring the vital signs of the patient comprises monitoring EKG or pulse oxygen level of the patient.

12. The method of claim 1 , wherein the second command includes the step of sounding an alarm for emergency personnel.

13. The method of claim 1 , wherein the step of performing the MRI scan comprises more than 20 minutes.

14. The method of claim 1 , wherein the defibrillation shock or second defibrillation shock comprises at least 15 joules.

15. The method of claim 1 , wherein the defibrillation shock or second defibrillation shock comprises at least 30 joules.

16. A method of performing a magnetic resonance imaging (MRI) scan on a patient having an implanted cardioverter defibrillator (ICD), the method comprising the steps of:

a) determining that the ICD comprises a ferrite core high voltage power supply transformer;

b) with the ICD not being in the presence of an MRI field generated by an MRI scanner, sending a communication signal from an external programmer to the ICD, the communication signal being a command pre-charging a high energy storage capacitor of the ICD before the patient undergoes the MRI scan, the command also switching the ICD into an MRI mode, the MRI mode turning off the ICD's sensing functions detecting a dangerous ventricular arrhythmia;

c) connecting sensors to the patient monitoring vital signs of the patient, the sensors displaying the vital signs to an operator on at least one display;

d) moving the patient into the MRI scanner;

e) performing the MRI scan while also monitoring the vital signs of the patient;

f) the operator determining from the display whether the patient requires a defibrillation shock;

g) when the patient requires the defibrillation shock, the operator sending a second communication signal from the external programmer to the ICD, the second communication signal being a second command delivering the defibrillation shock from the pre-charging high energy storage capacitor of the ICD to the patient while in the presence of the MRI field;

h) removing the patient from the MRI scanner after the MRI scan is completed or after the operator has sent the second command where the ICD delivered the defibrillation shock to the patient while in the presence of the MRI field;

i) moving the patient substantially away from the MRI main static field;

j) the operator sending a third communication signal from the external programmer to the ICD, wherein the third communication signal comprises a third command to switch the ICD to a non-MRI mode, the non-MRI mode turning on the ICD's sensing functions detecting a dangerous ventricular arrhythmia; and

k) in the non-MRI mode if the ICD has not delivered the defibrillation shock then allowing the ICD to automatically bleed off the charge stored in the high energy storage capacitor, or in the non-MRI mode if the ICD has delivered the defibrillation shock then determining that additional therapy is needed and allowing the ICD to automatically sense the dangerous ventricular arrhythmia and recharge the high energy storage capacitor and automatically delivering a second defibrillation shock to the patient.

17. A method of performing a magnetic resonance imaging (MRI) scan on a patient having an implanted cardioverter defibrillator (ICD), the method comprising the steps of:

a) determining that the ICD comprises a ferrite core high voltage power supply transformer;

b) with the ICD not being in the presence of an MRI field generated by an MRI scanner, sending a communication signal from an external programmer to the ICD, the communication signal being a command pre-charging a high energy storage capacitor of the ICD before the patient undergoes the MRI scan, the command also switching the ICD into an MRI mode, the MRI mode turning off the ICD's sensing functions detecting a dangerous ventricular arrhythmia;

c) connecting sensors to the patient monitoring vital signs of the patient, the sensors displaying the vital signs to an operator on at least one display;

d) moving the patient into the MRI scanner;

e) performing the MRI scan while also monitoring the vital signs of the patient;

f) the operator determining from the display whether the patient requires a defibrillation shock;

g) when the patient requires the defibrillation shock, the operator sending a second communication signal from the external programmer to the ICD, the second communication signal being a second command delivering the defibrillation shock from the pre-charging high energy storage capacitor of the ICD to the patient while in the presence of the MRI field, where the ICD comprises a magnetic field sensor in electrical communication with a processor for the ICD, the second command directing the processor to switch the ICD to a non-MRI mode when the magnetic field sensor detects a lack of a static magnetic field, the non-MRI mode turning on the ICD's sensing function detecting a dangerous ventricular arrhythmia;

h) removing the patient from the MRI scanner after the MRI scan is completed or after the operator has sent the second command where the ICD delivered the defibrillation shock to the patient while in the presence of the MRI field; and

i) moving the patient substantially away from the MRI main static field.

18. The method of claim 17 , including the step of if the ICD has not delivered the defibrillation shock then allowing the ICD to automatically bleed off the charge stored in the high energy storage capacitor, or if the ICD has delivered the defibrillation shock then determining that additional therapy is needed and allowing the ICD to automatically sense the dangerous ventricular arrhythmia and recharge the high energy storage capacitor and delivering a second defibrillation shock to the patient.