Method for extracting timing parameters using a cardio-mechanical sensor

• US 20070293771A1
• Filed: 06/19/2006
• Published: 12/20/2007
• Est. Priority Date: 06/19/2006
• Status: Active Grant

• Current Assignee: St. Jude Medical AB (Abbott Laboratories Incorporated)
• Original Assignee: St. Jude Medical AB (Abbott Laboratories Incorporated)
• Inventors: Noren, Kjell, Holmstrom, Nils
• Granted Patent: US 7,569,020 B2
• Time in Patent Office: Days
• US Class Current: 600/481
• CPC Class Codes: A61B 5/0031 Implanted circuitry
• CPC Class Codes: A61B 5/02416 using photoplethysmograph signals, e.g. generated by infrared radiation A61B5/14552 takes precedence
• CPC Class Codes: A61B 5/083 Measuring rate of metabolism by using breath test, e.g. measuring rate of oxygen consumption
• CPC Class Codes: A61B 5/1116 Determining posture transitions
• CPC Class Codes: A61B 5/349 Detecting specific parameters of the electrocardiograph cycle
• CPC Class Codes: A61B 5/686 Permanently implanted devices, e.g. pacemakers, other stimulators, biochips A61B5/6861 takes precedence
• CPC Class Codes: A61B 5/7239 using differentiation including higher order derivatives
• CPC Class Codes: A61N 1/36514 controlled by a physiological quantity other than heart potential, e.g. blood pressure controlled by two or more physical parameters A61N1/36585
• CPC Class Codes: A61N 1/36578 controlled by mechanical motion of the heart wall, e.g. measured by an accelerometer or microphone

Abstract

In a method and apparatus for measuring the ejection fraction in a mammalian heart, the opening and closing of a heart valve is sensed with an implanted sensor, and a pre-ejection period is measured as a function of the sensed opening and closing of the heart valve. The ventricular ejection time also is measured, and the ejection fraction is determined as a function of the measured pre-ejection period and the ejection time.

Claims

1. A method for measuring ejection fraction in a mammalian heart, comprising:

sensing the opening and closing of a heart valve with an implanted sensor;

measuring a pre-ejection period as a function of the sensed opening and closing of the heart valve;

measuring ventricular ejection time; and

determining an ejection fraction as a function of the measured pre-ejection period and ejection time.

2. The method according to claim 1, further comprising:

measuring the pre-ejection period a plurality of times during a predetermined time period;

measuring the ventricular ejection time a corresponding plurality of times during the predetermined time period;

determining the ejection fraction a corresponding plurality of times during the predetermined time period; and

storing the plurality of determined ejection fractions in memory.

3. The method according to claim 1, further comprising transmitting the stored plurality of determined ejection fractions to a determined location to permit the stored fractions to be read.

4. The method according to claim 1 further comprising filtering a measured pre-ejection period signal;

squaring the filtered signal to obtain a representation of the power value of the filtered signal;

filtering the squared signal a second time to obtain a smoothed output signal;

and calculating the derivative of the smoothed output signal to obtain the ejection fraction.

5. The method according to claim 1, further comprising controlling an implantable cardiac device as a function of the determined ejection fraction.

6. An apparatus for measuring ejection fraction in a mammalian heart, comprising:

a sensor that senses opening and closing of a heart valve;

a unit that measures a pre-ejection period as a function of the sensed opening and closing of the heart valve;

a unit that measures ventricular ejection time; and

a calculation unit that determines an ejection fraction as a function of the measured pre-ejection period and ejection time.

7. An apparatus according to claim 6, further comprising a memory for storing a plurality of determined ejection fractions in memory;

and an arrangement for transmitting the stored ejection fractions to a determined location to permit the stored fractions to be read.

8. An apparatus according to claim 6, further comprising:

a first filter for filtering a measured pre-ejection period signal;

a unit that squares the filtered signal to obtain a representation of the power value of the filtered signal;

a second filter for filtering the squared signal a second time to obtain a smoothed output signal; and

a unit that calculates the derivative of the smoothed output signal to obtain the ejection fraction.

9. An apparatus according to claim 6, further comprising a control unit that controls an implantable cardiac device as a function of the determined ejection fraction.