Low distortion ECG filter

• US 6,785,573 B2
• Filed: 12/09/2002
• Issued: 08/31/2004
• Est. Priority Date: 07/20/2000
• Status: Expired due to Term

• Current Assignee: Cardiac Pacemakers Incorporated (Boston Scientific Corporation)
• Original Assignee: Cardiac Pacemakers Incorporated (Boston Scientific Corporation)
• Inventors: Bange, Joseph E., Kovtun, Vladimir V., Dodson, Randall
• Primary Examiner(s): MANUEL, GEORGE C
• Application Number:
  US10/313,714
• Publication Number:
  US 20030083583A1
• Time in Patent Office: 631 Days
• Field of Search: 600/323, 600/508, 600/509, 600/513, 600/516, 600/520, 128/901
• US Class Current: 600/509
• CPC Class Codes: A61B 5/30 Input circuits therefor
• CPC Class Codes: A61B 5/308 for electrocardiography [ECG]
• CPC Class Codes: A61B 5/725 using specific filters therefor, e.g. Kalman or adaptive filters A61B5/316 take precedence
• CPC Class Codes: Y10S 128/901 Suppression of noise in electric signal

Abstract

A low pass filter especially adapted for use with ECG equipment designed to negate any noise energy that may be superimposed upon the ECG signal itself. A plurality of low-pass FIR filter stages are connected in tandem between a signal input point and a signal output point where each of the stages has a distinct cut-off frequency characteristic. Means are provided for selectively turning ones of the plurality of stages on or off.

Claims

1. A method of processing ECG signals comprising the steps of:

(a) applying amplified analog waveforms representative of ecg vectors to an analog-to-digital converter;

(b) obtaining digital values from the analog-to-digital converter representative of the amplitude of the ecg vector signals at discrete sampling times;

(c) storing the digital values in a multi-stage time delay buffer;

(d) computing from the stored digital values a scaled noise signal falling within a first predetermined frequency band;

(e) dynamically determining upper and lower limits for the scaled noise signal computed in step (d); and

(f) subtracting the signal computed in step (d) from a data sample stored in a predetermined stage of the time delay buffer to yield an output signal devoid of noise falling within said first predetermined frequency band.

2. The method of claim 1 and further including the steps of applying said output signal to a further time delay buffer and repeating steps (d), (e) and (f) on the stored digital values in the further time delay buffer, step (d) involves a second predetermined frequency band different from said first predetermined frequency band.