QT-based system and method for detecting and distinguishing dilated cardiomyopathy and heart failure using an implantable medical device

• US 7,672,716 B1
• Filed: 04/03/2006
• Issued: 03/02/2010
• Est. Priority Date: 04/03/2006
• Status: Expired due to Fees

• Current Assignee: Pacesetter Incorporated (Abbott Laboratories)
• Original Assignee: Pacesetter Incorporated (Abbott Laboratories)
• Inventors: Koh, Steve
• Primary Examiner(s): Evanisko; George R
• Assistant Examiner(s): Dietrich; Joseph M
• Application Number:
  US11/397,066
• Time in Patent Office: 1,429 Days
• Field of Search: 600/509, 600513-516
• US Class Current: 600/515
• CPC Class Codes: A61B 5/02405 Determining heart rate variability
• CPC Class Codes: A61B 5/349 Detecting specific parameters of the electrocardiograph cycle
• CPC Class Codes: A61B 5/36 Detecting PQ interval, PR interval or QT interval
• CPC Class Codes: A61B 5/7275 Determining trends in physiological measurement data; Predicting development of a medical condition based on physiological measurements, e.g. determining a risk factor
• CPC Class Codes: A61N 1/3627 for treating a mechanical deficiency of the heart, e.g. congestive heart failure or cardiomyopathy

Abstract

Techniques are provided for detecting dilated cardiomyopathy within a patient using a pacemaker or other implantable medical device. Briefly, values representative of QT duration and QT dispersion are detected within the patient and then the risk of dilated cardiomyopathy is evaluated based on the values of QT duration and QT dispersion. In one particular example, the implanted device calculates an index representative of the extent to which individual QT duration and QT dispersion values deviate from a daily mean. The device then compares the index against a threshold indicative of a substantial likelihood of the presence of dilated cardiomyopathy within the patient. Additional techniques described herein relate to distinguishing dilated cardiomyopathy from heart failure within patients that may have one or both conditions.

Claims

1. A method for detecting an increased risk of dilated cardiomyopathy within a patient for use by an implantable medical device for implant within the patient, the method comprising:

detecting values representative of both QT duration and QT dispersion within the patient using the implantable medical device;

generating a QT dispersion histogram (H_{QT-dispersion}) based on a plurality of QT dispersion values detected over one day;

generating a QT duration histogram (H_QT-duration) based on a plurality of QT duration values detected over one day; and

calculating a QT dispersion daily mean and a QT duration daily mean using the histograms

calculating an index (QT_INDEX) representative of an amount of deviation in QT duration and in QT dispersion values from their respective daily means as follows;

subtracting the QT dispersion daily mean from each bin value in the QT dispersion histogram (H_{QT-dispersion});

subtracting the QT duration daily mean from each bin value in the QT duration histogram (H_QT-duration) and multiplying each of the bin values in the QT duration histogram (H_QT-duration) by a corresponding QT duration histogram (H_QT-duration) bin count; and

subtracting the QT dispersion daily mean from each bin value in the QT dispersion histogram (H_{QT-dispersion}) and multiplying each of the bin values in the QT dispersion histogram (H_{QT-dispersion}) by a corresponding QT dispersion histogram (H_{QT-dispersion}) bin count; and

combining the amount of deviation and dispersion to yield the index value (QT_INDEX); and

detecting an increased risk of dilated cardiomyopathy within the patient by comparing the index (QT_INDEX) against a threshold (DC_THRESHOLD) indicative of dilated cardiomyopathy.

2. The method of claim 1 wherein combining the amount of deviation and dispersion to yield the index value (QT_INDEX) includes:

summing the resulting bin values within the QT duration histogram (H_QT-duration) together with the resulting bin values within the QT dispersion histogram (H_QT-duration) to yield the index value (QT_INDEX).

3. The method of claim 1 further including evaluating the severity of dilated cardiomyopathy, if present within the patient, based on the index value (QT_INDEX).

4. The method of claim 3 further including tracking changes in the severity of dilated cardiomyopathy by detecting differences between index values (QT_INDEX) generated based on QT data collected at different times.

5. The method of claim 1 further comprising controlling delivery of therapy by the implantable medical device in response to the detection of an increased risk of dilated cardiomyopathy.

6. The method of claim 5 wherein the implantable medical device is capable of delivering cardiac pacing and wherein controlling delivery of therapy comprises controlling the delivery of pacing therapy to the heart of the patient in a manner effective to address dilated cardiomyopathy.

7. The method of claim 5 wherein an implantable drug pump is provided and wherein controlling delivering therapy comprises delivering medications effective to address dilated cardiomyopathy to the patient using the drug pump.

8. The method of claim 1 wherein an implantable warning device is provided and wherein the method further comprises generating warning signals using the implantable warning device based on the detection of an increased risk of dilated cardiomyopathy.

9. The method of claim 1 wherein an external warning device is provided and wherein the method further comprises transmitting appropriate signals to the external warning device indicative of an increased risk of dilated cardiomyopathy.

10. The method of claim 1 further comprising controlling storage of diagnostic information indicative of the increased risk of dilated cardiomyopathy.