Portable EKG monitoring device for ST deviation

• US 4,546,776 A
• Filed: 09/13/1984
• Issued: 10/15/1985
• Est. Priority Date: 09/13/1984
• Status: Expired due to Fees

• Current Assignee: Cortec Association
• Original Assignee: Cortec Association
• Inventors: Bellin, Howard T., Tchorbajian, Nichan, Fellner, Donald
• Primary Examiner(s): Kamm, William E.
• Application Number:
  US06/650,108
• Time in Patent Office: 397 Days
• Field of Search: 128/702-704, 128/706
• US Class Current: 600/517
• CPC Class Codes: A61B 5/349 Detecting specific parameters of the electrocardiograph cycle
• CPC Class Codes: A61B 5/358 Detecting ST segments

Abstract

A portable cardiac monitor analyzes the PQ and ST portions of an electrocardiogram waveform and establishes a "normal" or standard ST ratio deviation of the difference between the ST and PQ levels. When a subsequently measured ST ratio deviation exceeds the previously stored normal value, an alarm is indicated indicating a possible ischemic condition. The pulse rate may also be monitored to provide an alarm whenever the pulse rate rises above or falls below a predetermined value.

Claims

1. A cardiac monitoring unit comprising sensing means adapted to be attached to the body of an individual to produce an analog representation of the individual'"'"'s electrocardiogram waveform;

means coupled to said sensing means for establishing and storing an ST deviation signal corresponding to the ST deviation of said electrocardiogram waveform;

said ST deviation signal establishing means comprising means for locating the QR portion of the waveform, means for sampling a first portion of the waveform at a predetermined period prior to the Q portion of the waveform, means for measuring the slope of the waveform at the sampled points in said first portion, means for determining a first voltage of the waveform at which the measured slope is nearest to zero, means for sampling a second portion of the waveform at a predetermined period subsequent to the S portion of the waveform, means for measuring the slope of the waveform at the sampled points in said second portion, means for determining a second voltage of said second portion of the waveform at which the measured slope is nearest to zero, and means for determining the ST deviation signal as the difference between said first and second voltages;

means for thereafter continuously monitoring the ST deviation signal of said electrocardiogram waveform and for comparing the monitored ST deviation signal with the stored normal ST deviation signal; and

means for activating an alarm when the monitored ST deviation signal bears a predetermined relation to the stored normal ST deviation signal.

2. The cardiac monitoring device of claim 1, further comprising means coupled to said sensing means for converting said analog representation to a corresponding digital signal, and a microprocessor including said establishing and storing means and said comparing means coupled to said converting means.

3. The cardiac monitoring device of claim 2, in which said microprocessor further comprises means for identifying and characterizing a normal heartbeat shape for the individual from said electrocardiogram waveform.

4. The cardiac monitoring device of claim 1, further comprising means for actuating an alarm whenever the rate of sensed heartbeats exceeds or is lower than a predetermined rate.

5. A method for monitoring an individual'"'"'s cardiac condition comprising the steps of:

(a) sensing the individual'"'"'s electrocardiogram waveform;

(b) providing an analog voltage representative of said electrocardiogram waveform, said step of establishing said standard ST deviation value comprising the steps of (i) locating the QR portion of the waveform, (ii) sampling a first portion of the waveform at a predetermined period prior to the Q portion of the waveform, (iii) measuring the waveform at the sampled points of said first portion, (iv) determining a first voltage of said first portion of the waveform at which the measured slope is nearest to zero, (v) sampling a second portion of the waveform at a predetermined period subsequent to the S portion of the waveform, (vi) measuring the scope of the waveform at the sampled points of said second portion;

(vi) determining a second voltage of said second portion at which the slope is closest to zero, and (viii) determining the ST deviation signal as the difference between said first and second voltages;

(c) said deviation evaluation step including the steps of establishing a standard ST deviation value for said electrocardiogram waveform;

(d) storing said standard ST deviation value;

(e) thereafter continuously measuring the ST deviation value of the individual'"'"'s electrocardiogram waveform;

(f) comparing the measured ST deviation value with said standard ST deviation value; and

(g) actuating an alarm whenever the measured ST deviation value bears a predetermined relationship to said standard ST deviation value.

6. The method of claim 5, further comprising the step of identifying and characterizing a normal heartbeat of the individual.