Implantable lead for sensing a physiologic parameter of the body

• US 5,438,987 A
• Filed: 05/28/1993
• Issued: 08/08/1995
• Est. Priority Date: 06/14/1991
• Status: Expired due to Fees

• Current Assignee: Pacesetter Incorporated (Abbott Laboratories)
• Original Assignee: Pacesetter Incorporated (Abbott Laboratories)
• Inventors: Thacker, James R., Moaddeb, Shahram, Weinberg, Alvin H.
• Primary Examiner(s): Cohen, Lee S.
• Assistant Examiner(s): Casler, Brian L.
• Application Number:
  US08/068,454
• Time in Patent Office: 802 Days
• Field of Search: 128/634, 128/637, 128/700, 607/17, 607/18, 607/22, 607/9, 607/122, 606/12, 606/14
• US Class Current: 600/337
• CPC Class Codes: A61N 1/056 Transvascular endocardial electrode systems
• CPC Class Codes: A61N 1/36557 controlled by chemical substances in blood
• CPC Class Codes: A61N 1/3702 Physiological parameters A61N1/365 takes precedence; evoked response A61N1/371
• CPC Class Codes: Y10T 29/49117 Conductor or circuit manufacturing

Abstract

The present invention includes a body implantable lead having a multipolar proximal connector, at least a first conductor coupled to at least one stimulating electrode, a sensor for sensing at least one physiologic parameter of the body, and a second and a third conductor coupled to the sensor. The sensor is hermetically sealed in a D-shaped housing. Sensor components are mounted onto a microelectronic substrate which is advantageously placed on an inner flat portion of the D-shaped housing. End caps having sealing rings, either glass frit or metal, are used to seal the ends of the shell. A hermetic seal is easily achieved by heating the sealing material until they re-flow between the end caps and the shell. Advantageously, the sensor terminals are sized to fit snugly within a narrow bore of the end cap which is then circumferentially welded closed. The D-shaped sensor is placed on a carrier having at least two lumens. At least the first and second conductors pass through the lumens for connection with the stimulating electrode and the distal end of the sensor. Advantageously, the D-shaped housing reduces the area that needs to be hermetically sealed by more than half, and thus reduces the overall diameter of the lead. Advantageously, the conductors coupled to the sensor function independently from the stimulation conductors so that interference with basic operation of the pacemaker is prevented.

Claims

1. A body implantable sensor, comprising:

optical sensing means for sensing a specified characteristic of the body, the sensing means having a first and a second sensor terminal;

an optically clear, tubular shell having a D-shape, the shell having a flat surface with the optical sensing means mounted thereon, the shell having two open ends;

two end caps dimensioned to fit into the two open ends of the shell, respectively, each end cap having a channel to allow one of the sensor terminals to pass therethrough; and

means for hermetically sealing the end caps to the shell.

2. The sensor, as recited in claim 1, wherein the shell comprises one of glass, glass ceramic, or an optically clear ceramic.

3. The sensor, as recited in claim 2, wherein the optically clear ceramic comprises a selected one of alumina, sapphire, ruby, quartz or silica ceramic.

4. The sensor, as recited in claim 2, wherein the hermetic sealing means comprises:

a glass frit seal ring at each end of the shell, the glass frit seal rings forming a leakproof seal between each of the two end caps and the shell after being exposed to a high temperature.

5. The sensor, as recited in claim 2, wherein the hermetic sealing means comprises:

a metal seal ring at each end of the shell, the metal seal ring forming a leakproof seal between each of the two end caps and the shell after being exposed to a high temperature.

6. The sensor, as recited in claim 1, wherein at least one of the two end caps has engaging means for mating one end of each end cap to the shell.

7. The sensor, as recited in claim 6, wherein:

the engaging means includes a protruding portion at one end of the at least one end cap and a shoulder adjacent to each protruding portion, the protruding portion having dimensions so as to provide a snug fit when mated within the shell.

8. The sensor, as recited in claim 1, wherein:

at least one of the two end caps includes an inner cap and an outer cap, the inner cap and the outer cap having dimensions so as to provide a snug fit when mated with each other, the inner cap having a channel dimensioned to slidably receive the optical sensing means, the outer cap having a narrow opening at one end for passing one of the sensor terminals therethrough; and

the hermetic sealing means includes means for sealing the inner cap to the shell, means for sealing the inner cap and the outer cap at the point where the inner cap and the outer cap mate, and means for sealing the outer cap to the sensor terminals at the narrow opening of the outer cap.

9. The sensor, as recited in claim 8, wherein:

the means for sealing the inner cap to the outer cap comprises a seal formed by circumferentially welding the inner cap to the outer cap.

10. The sensor, as recited in claim 8, wherein:

the means for sealing the outer cap to the sensor terminals includes one of a glass seal ring or a seal formed by circumferentially welding the sensor terminals to the outer cap.

11. The sensor, as recited in claim 8, wherein:

the means for sealing the inner cap to the shell comprises one of a glass frit seal ring or a metal braze seal ring which forms a leakproof seal after being exposed to a high temperature, the inner cap being sealed to the shell prior to mounting the sensing means, thereby preventing excessive heat from damaging the sensing means.

12. The body implantable sensor, as recited in claim 11, wherein the sensing means comprises:

light-emitting means for emitting light to body tissue through the shell;

light-receiving means for receiving light reflected from the body tissue through the shell, the amount of the light reflected back to the light-receiving means having a proportional relationship with blood oxygen content; and

a substrate having the light-emitting means and the light-receiving means electrically and mechanically mounted thereon, the substrate having pre-attached sensor terminals so that the substrate can be slidably mounted within the D-shaped shell.

13. The body implantable sensor, as recited in claim 12, wherein the sensing means further comprises:

a D-shaped light barrier mounted onto the substrate between the light-emitting means and the light-receiving means for blocking light directly therebetween, the light barrier having an outer perimeter dimensioned to slidably fit within the D-shaped shell.

14. The body implantable sensor, as recited in claim 13, wherein the light barrier has an L-shaped support structure, the support structure having conductive mounting means for mounting the light-emitting means thereon, so that the light barrier and the light-emitting means can be electrically and mechanically mounted onto the substrate.

15. The body implantable sensor, as recited in claim 14, wherein the L-shaped support structure has a desired thickness, so that the light-emitting means can be mounted closer to the body tissue.

16. A body implantable lead, the lead including a first, second, third and fourth proximal terminals, a tip electrode and a ring electrode at a distal end, and two conductors separately connecting the tip and the ring electrode to the first and second proximal terminals, respectively, the two conductors being insulated within an inner lead body, the implantable lead further comprising:

sensing means for sensing a specified characteristic of the body, the sensing means having a first and a second sensor terminal;

a tubular, D-shaped shell having a flat surface with the sensing means mounted thereon, the shell having two open ends;

two end caps dimensioned to fit into the two open ends of the shell, respectively, each end cap having a channel therethrough to allow one of the sensor terminals to pass therethrough;

means for hermetically sealing the end caps to the shell;

means for mounting the D-shaped shell onto the inner lead body;

a third conductor, coaxially wound about the inner lead body, electrically connected between the third proximal terminal and the first sensor terminal;

a fourth conductor, electrically insulated from the third conductor, coaxially wound about the inner lead body, the fourth conductor being electrically connected between the fourth proximal terminal and the second sensor terminal; and

an outer insulating means for encapsulating the shell, the inner lead body, and the third and fourth conductors.

17. The body implantable lead, as recited in claim 16, wherein the mounting means comprises:

a semicircular clip attached to the shell, the clip having an inside diameter approximately equal to an outside diameter of the inner lead body so that the shell remains in a fixed position.

18. The body implantable lead, as recited in claim 16, wherein the mounting means comprises:

a circular ring attached to the shell, the ring having an inside diameter approximately equal to an outside diameter of the inner lead body so that the inner lead body can slide therethrough.

19. The body implantable lead, as recited in claim 16, wherein the mounting means comprises potting material.