Discrimination of supraventricular tachycardia and ventricular tachycardia events

• US 6,223,078 B1
• Filed: 03/12/1999
• Issued: 04/24/2001
• Est. Priority Date: 03/12/1999
• Status: Expired due to Term

• Current Assignee: Cardiac Pacemakers Incorporated (Boston Scientific Corporation)
• Original Assignee: Cardiac Pacemakers Incorporated (Boston Scientific Corporation)
• Inventors: Marcovecchio, Alan F.
• Primary Examiner(s): Jastrzab, Jeffrey R.
• Assistant Examiner(s): EVANISKO, GEORGE ROBERT
• Application Number:
  US09/267,307
• Time in Patent Office: 774 Days
• Field of Search: 600/515, 600/518, 607/4, 607/5, 607/14
• US Class Current: 607/5
• CPC Class Codes: A61B 5/35 by template matching
• CPC Class Codes: A61N 1/3956 Implantable devices for applying electric shocks to the heart, e.g. for cardioversion

Abstract

A method and system for discrimination of supraventricular tachycardia and ventricular tachycardia events. Morphological features points are extracted from normal sinus rhythm (NSR) complexes and used to generate a NSR template. A numerical convolution is performed using the NSR template and the feature points for each sensed NSR to give a NSR filter output. Using a plurality of NSR complexes, a median NSR filter output template is determined, where the median NSR filter output template has a median value for each value in the NSR filter output. The median NSR filter output template is then used during a tachycardia event to distinguish tachycardia events as either ventricular tachycardia events or supraventricular tachycardia events.

Claims

1. A method comprising:

sampling a normal sinus rhythm (NSR) QRS-complex from a NSR cardiac cycle;

locating a plurality of feature points on the NSR QRS-complex based on morphological features of the NSR QRS-complex;

determining a NSR template for plurality of the NSR cardiac cycles, wherein the NSR template includes a median value for each of the plurality of feature points;

producing a NSR filter output from a numerical convolution of the NSR template and the plurality of feature points for each of the plurality of the NSR cardiac cycles;

for the plurality of the NSR cardiac cycles, determining a median NSR filter output template, where the median NSR filter output template has a median value for each value in the NSR filter output;

detecting a tachycardia event sampling a QRS-complex from a tachycardia complex during the tachycardia event;

locating the plurality of feature points on the QRS-complex from the tachycardia complex based on morphological features of the QRS-complex;

producing a tach-ycardia complex output from a numerical convolution of the NSR template with the plurality of feature points on the QRS-complex from the tachycardia complex; and

summing a numerical difference between the values of the tachycardia complex output and the median NSR filter output template.

2. The method of claim 1, including classifying the tachycardiac complex as a ventricular tachycardia complex when the sum of the difference between the values of the tachycardia complex output and the median NSR filter output template is greater than or equal to a predetermined sum of residual threshold value.

3. The method of claim 2, including determining an absolute value of the difference between the values of the tachycardia complex output and the median NSR filter output template;

and

classifying the cardiac complex as a supraventricular tachycardia complex when the absolute value of the difference between the values of the tachycardia complex output and the median NSR filter output template is less than the predetermined sum of residual threshold value.

4. The method of claim 3, including sampling a plurality of tachycardiac complexes, classifying each of the plurality of tachycardiac complexes as either a ventricular tachycardia complex or a supraventricular tachycardia complex, and determining whether the number of ventricular tachycardia complexes exceeded a predetermined threshold value.

5. The method of claim 4, including declaring a ventricular tachycardia event when the number of ventricular tachycardia complexes exceeded the predetermined threshold value.

6. The method of claim 5, including providing a signal to a cardioversion/defibrillation output circuit and delivering a ventricular tachycardia therapy from the output circuit to a heart when the ventricular tachycardia event is declared.

7. The method of claim 4, including declaring a supraventricular tachycardia event when the number of supraventricular tachycardia complexes exceeded the predetermined threshold value.

8. The method of claim 7, including providing a signal to a cardioversion/defibrillation output circuit and delivering a supraventricular tachycardia therapy from the output circuit to a heart when the supraventricular tachycardia event is declared.

9. The method of claim 1, wherein summing a numerical difference includes summing an absolute value of the difference between the values of the tachycardia complex output and the median NSR filter output template.