Cardiac monitoring apparatus and monitor

• US 4,172,459 A
• Filed: 10/17/1977
• Issued: 10/30/1979
• Est. Priority Date: 10/17/1977
• Status: Expired due to Term

• Current Assignee: Medtronic Incorporated (Medtronic Plc)
• Original Assignee: Medtronic Incorporated (Medtronic Plc)
• Inventors: Hepp, Dennis G.
• Primary Examiner(s): Kamm, William E.
• Application Number:
  US05/842,388
• Time in Patent Office: 743 Days
• Field of Search: 128/2.06 A, 128/2.06 E, 128/2.06 R, 128/2.1 A, 128/419 PG, 128/419 PT, 128/419 PS
• US Class Current: 600/510
• CPC Class Codes: A61B 5/0031 Implanted circuitry
• CPC Class Codes: A61B 5/7203 for noise prevention, reduction or removal
• CPC Class Codes: A61N 1/3625 External stimulators
• CPC Class Codes: A61N 1/3706 Pacemaker parameters stimulation threshold A61N1/371
• CPC Class Codes: A61N 1/3727 characterised by the modulation technique

Abstract

Cardiac monitoring apparatus comprising a first external unit for transmitting electromagnetic energy within the patient'"'"'s body to be received by a second, surgically implanted unit within the patient'"'"'s body and adapted to be solely powered by the transmitted electromagnetic energy. The internal unit includes a monitoring circuit connected via electrodes coupled to first and second sites of the patient'"'"'s heart, for providing corresponding first and second signals to be first time multiplexed and then pulse-width modulated before being re-transmitted to the external unit. The external unit decodes the transmitted signals to provide diagnostic quality signals indicative of the patient'"'"'s EKG.

Claims

1. Cardiac monitoring apparatus for monitoring a patient'"'"'s heart activity, said cardiac monitoring apparatus comprising:

(a) a first unit disposed externally of the patient'"'"'s body and including means for transmitting electromagnetic energy within the patient'"'"'s body;

(b) a second unit adapted to be surgically implanted within the patient'"'"'s body, said second unit including first means responsive to the externally generated electromagnetic energy for providing the sole energization of said second unit, second means coupled to sense first and second conditions of the patient'"'"'s heart for providing first and second electrical signals indicative of the first and second sensed conditions respectively, and third means for pulse-width modulating and transmitting one of said first and second electrical signals externally of the patient'"'"'s body to said first unit without distortion due to environmental noise or relative movement of said first and second unit, said third means sequentially transmits said first and second electrical signals externally of the patient'"'"'s body in first and second sequential time slots, respectively; and

(c) said first unit comprising decoding means responsive to said one modulated signal from said second unit for providing a third signal indicative of the sensed heart condition, and means responsive to said third signal for providing a manifestation of the patient'"'"'s heart activity.

2. Cardiac monitoring apparatus as claimed in claim 1, wherein said first unit includes means for receiving and demodulating the third signal transmitted from said third means of said second unit.

3. The cardiac monitoring and stimulating apparatus as claimed in claim 2, wherein said third means of said second unit effects the timing of each of said first and second time slots at a rate and of a duration so as to repeatedly sample each of the conditions of the first and second sites of the patient'"'"'s heart.

4. Cardiac monitoring apparatus as claimed in claim 1, wherein said third means of said second unit comprises clock means for sequentially transmitting a third timing, reference signal in a third timing slot after said second time slot, said third timing, reference signal disposed in a known relationship to said first and second time slots, said decoding means responsive to the third timing, reference signal for time demultiplexing the transmitted first and second signals.

5. Cardiac monitoring apparatus as claimed in claim 4, wherein said first unit comprises decoding means for receiving said first, second and third signals and for providing first and second output signals indicative of the first and second conditions of the patient'"'"'s heart.

6. Cardiac monitoring apparatus as claimed in claim 1, wherein said second unit includes inductive coupling means connected to said third means for transmitting the pulse-width modulated first signal to said first unit.

7. Cardiac monitoring apparatus as claimed in claim 1, wherein said transmitting means of said first unit transmits electromagnetic energy for a first, relatively short period, and said first means of said second unit comprises means responsive to the externally generated electromagnetic energy for generating and providing energization to said third means for a second, relatively long period.

8. Cardiac monitoring apparatus as claimed in claim 1, wherein said first unit includes means for transmitting a series of bursts of RF electromagnetic energy within the patient'"'"'s body, said first means of said second unit responsive to the bursts of RF electromagnetic energy for providing the sole energization of said second unit.

9. Cardiac monitoring apparatus for monitoring the first and second activities at the first and second sites of a patient'"'"'s heart, each of the first and second heart activities occuring periodically normally, and each such occurence being of a limited duration, said monitoring apparatus comprising:

(a) a first unit disposed externally of the patient'"'"'s body and including means for transmitting electromagnetic energy within the patient'"'"'s body;

(b) a second unit adapted to be surgically implanted within the patient'"'"'s body, said second unit including means responsive to the externally generated energy for providing the sole energization of said second unit, second means coupled to sense the first and second activities of the patient'"'"'s heart for providing first and second electrical signals indicative of the first and second heart activities and of a corresponding limited duration, and third means for sequentially sampling the first and second electrical signals at a rate and of a duration to ensure repeated sampling of each of the first and second electrical signals and for pulse-width modulating the sampled first and second electrical signals for transmission in first and second time slots, respectively, whereby the modulated first and second electrical signals are transmitted without distortion due to extraneous noise or to relative movement of said first and second units; and

(c) said first unit comprising decoding means responsive to said modulated first and second electrical signals from said second unit for providing third and fourth signals indicative of the sensed first and second heart activities, and means responsive to said third and fourth signals for providing manifestations of the patient'"'"'s first and second heart activities.

10. Cardiac monitoring apparatus as claimed in claim 9, wherein said third means of said second unit comprises clock means for sequentially transmitting a third timing, reference signal in a third timing slot after said second time slot, said third signal disposed in a known relationship with respect to said first and second timing slots.

11. Cardiac monitoring apparatus as claimed in claim 10, wherein said decoding means receives said first, second and third signals and is responsive to the third timing, reference signal for time demultiplexing the first and second signals to provide first and second output signals indicative of the first and second heart activities.

12. Cardiac monitoring apparatus as claimed in claim 9, wherein said second unit comprises inductive coupling means connected to said third means for transmitting the pulse-width modulated first and second electrical signals to said first unit.

13. Cardiac monitoring apparatus as claimed in claim 9, wherein said transmitting means of said first unit transmits electromagnetic energy for a first, relatively short period, and said first means of said second unit comprises means responsive to the externally generated electromagnetic energy for generating and applying energization to said third means for a second, relatively long period.

14. Cardiac monitoring apparatus for monitoring a patient'"'"'s heart activity, said cardiac monitoring apparatus comprising:

(a) a first unit disposed externally of the patient'"'"'s body and including means for transmitting electromagnetic energy within the patient'"'"'s body;

(b) a second unit adapted to be surgically implanted within the patient'"'"'s body, said second unit including first means responsive to the externally generated electromagnetic energy for providing the sole energization of said second unit, second means coupled to sense first and second conditions of the patient'"'"'s heart for providing first and second electrical signals indicative of the first and second sensed heart conditions respectively, and third means for frequency modulating and transmitting one of said first and second electrical signals externally of the patient'"'"'s body to said first unit without distortion due to environmental noise or relative movement between said first and second units, said third means sequentially transmits said first-mentioned and said second signal externally of the patient'"'"'s body in first and second sequential time slots, respectively; and

(c) said first unit comprising decoding means responsive to the one modulated signal from said second unit for providing a third signal indicative of the sensed heart condition, and means responsive to said third signal for providing a manifestation of the patient'"'"'s heart activity.