Systems and methods for detecting arrhythmias

1 . A system for improving arrhythmia detection in a patient, comprising:

a sensor circuit configured to sense physiologic information from the patient;

an arrhythmia detector circuit configured to:

receive user-programmed values of arrhythmia detection parameters including (i) a first time period and an associated onset condition for detecting an onset of an arrhythmia event, and (ii) a second time period subsequent to and longer than the first time period, and an associated exit condition different from the onset condition, for detecting a termination of the arrhythmia event, the different onset and exit conditions and time periods configured to improve arrhythmia detection;

receive the physiologic information from the sensor circuit, sensed from the patient over time, including during the first and the second time periods;

determine, based on the received physiologic information during the first time period, whether the onset condition is satisfied, and to detect the arrhythmia onset in response thereto;

in response to the detected arrhythmia onset, determine, based on the received physiologic information during the second time period, whether the exit condition is satisfied, and to detect the arrhythmia termination in response thereto; and

detect an arrhythmia episode based on an arrhythmia duration between the detected arrhythmia onset and the detected arrhythmia termination; and

an output unit configured to provide the detected arrhythmia episode to a user or a process.

2 . The system of claim 1 , wherein the first time period includes a first time window, and the second time period includes two consecutive time windows subsequent to the first time window, and

wherein the arrhythmia detector circuit is configured to detect the arrhythmia termination when respective physiologic information in each of the two consecutive time windows of the second time period separately satisfy the exit condition.

3 . The system of claim 2 , wherein the two consecutive time windows each have a time duration substantially equal to a duration of the first time window.

4 . The system of claim 2 , wherein the onset condition includes an initial criterion and a confirmation criterion, and the arrhythmia detector circuit is configured to detect the arrhythmia onset when the received physiologic information in the first time window satisfies both the initial detection criterion and the confirmation criterion.

5 . The system of claim 4 , wherein the arrhythmia detector circuit is configured to:

generate a first signal metric and a different second signal metric from the received physiologic information in the first time window; and

determine that the received physiologic information in the first time window satisfies the initial criterion using the first signal metric, and satisfies the confirmation criterion using the second signal metric.

6 . The system of claim 5 , wherein the arrhythmia episode includes atrial tachyarrhythmia, the first metric includes at least one of an atrial heart rate or a ventricular heart rate variability, and the second metric includes at least one of:

a ventricular rate cluster;

a Wenckebach score;

a double-decrement ratio; or

a cardiac signal morphology.

7 . The system of claim 2 , wherein the exit condition includes an initial criterion and a confirmation criterion for each of the two consecutive time windows, and

wherein the arrhythmia detector circuit is configured to detect the arrhythmia termination (i) when the respective physiologic information in at least one of the two consecutive time windows fails the initial criterion, or (ii) when the respective physiologic information in each of the two consecutive time windows separately fail the confirmation criterion.

8 . The system of claim 7 , wherein the arrhythmia detector circuit is configured to:

generate a first signal metric and a different second signal metric from the respective physiologic information in each of the two consecutive time windows; and

for each of the two consecutive time windows, determine that the respective physiologic information in the corresponding time window fails the initial criterion using the first signal metric, or fails the confirmation criterion using the second signal metric.

9 . The system of claim 8 , wherein the arrhythmia episode includes atrial tachyarrhythmia, the first metric includes at least one of an atrial heart rate or a ventricular heart rate variability, and the second metric includes at least one of:

a ventricular rate cluster;

a Wenckebach score;

a double-decrement ratio; or

a cardiac signal morphology.

10 . The system of claim 1 , wherein the arrhythmia detector circuit is configured to detect the arrhythmia episode including a sustained arrhythmia episode if the arrhythmia duration exceeds a threshold, or a non-sustained arrhythmia episode if the arrhythmia duration is below the threshold.

11 . The system of claim 1 , comprising an implantable cardiac monitor that includes the arrhythmia detector circuit.

12 . The system of claim 1 , comprising a therapy unit configured to provide therapy to the patient in response to the detected arrhythmia episode.

13 . A method for improving arrhythmia detection in a patient, the method comprising:

sensing physiologic information from the patient using a sensor circuit;

receiving user-programmed values of arrhythmia detection parameters including (i) a first time period and an associated onset condition for detecting an onset of an arrhythmia event, and (ii) a second time period subsequent to and longer than the first time period, and an associated exit condition different from the onset condition, for detecting a termination of the arrhythmia event;

receiving the physiologic information from the sensor circuit, sensed from the patient over time, including during the first and the second time periods;

via an arrhythmia detector circuit, determining, based on the received physiologic information during the first time period, whether the onset condition is satisfied, and detecting the arrhythmia onset in response thereto;

in response to the detected arrhythmia onset, via the arrhythmia detector circuit, determining, based on the received physiologic information during the second time period, whether the exit condition is satisfied, and detecting the arrhythmia termination in response thereto;

detecting an arrhythmia episode based on an arrhythmia duration between the detected arrhythmia onset and the detected arrhythmia termination; and

providing the detected arrhythmia episode to a user or a process.

14 . The method of claim 13 , wherein the first time period includes a first time window, and the second time period includes two consecutive time windows subsequent to the first time window each having a time duration substantially equal to a duration of the first time window, and

wherein detecting the arrhythmia termination occurs when respective physiologic information in each of the two consecutive time windows of the second time period separately satisfy the exit condition.

15 . The method of claim 14 , wherein the onset condition includes an initial criterion and a confirmation criterion, and

wherein detecting the arrhythmia onset occurs when the received physiologic information in the first time window satisfies both the initial detection criterion and the confirmation criterion.

16 . The method of claim 15 , comprising:

generating a first signal metric and a different second signal metric from the received physiologic information in the first time window; and

determining that the received physiologic information in the first time window satisfies the initial criterion using the first signal metric, and satisfies the confirmation criterion using the second signal metric.

17 . The method of claim 14 , wherein the exit condition includes an initial criterion and a confirmation criterion for each of the two consecutive time windows, and

wherein detecting the arrhythmia termination occurs (i) when the respective physiologic information in at least one of the two consecutive time windows fails the initial criterion, or (ii) when the respective physiologic information in each of the two consecutive time windows fails the confirmation criterion,

wherein the method includes:

generating a first signal metric and a different second signal metric from the respective physiologic information in each of the two consecutive time windows; and

for each of the two consecutive time windows, determining that the respective physiologic information in the corresponding time window fails the initial criterion using the first signal metric, or fails the confirmation criterion using the second signal metric.

18 . The method of claim 13 , wherein detecting the arrhythmia episode includes detecting a sustained episode if the arrhythmia duration exceeds a threshold, and detecting a non-sustained episode if the arrhythmia duration is below the threshold.

19 . The method of claim 13 , comprising delivering a therapy to the patient in response to the detected arrhythmia episode.

20 . A system for improving arrhythmia detection in a patient, the system comprising:

an implantable or ambulatory medical device for detecting cardiac arrhythmia in a patient, the device comprising:

a sensor circuit configured to sense physiologic information from the patient;

an arrhythmia detector circuit of the implantable or ambulatory medical device, the arrhythmia detector circuit configured to:

receive user-programmed values of arrhythmia detection parameters including (i) a first time period and an associated onset condition for detecting an onset of an arrhythmia event, and (ii) a second time period subsequent to and longer than the first time period, and an associated exit condition different from the onset condition, for detecting a termination of the arrhythmia event, the different onset and exit conditions and time periods stored in a memory of the implantable or ambulatory medical device and configured to improve arrhythmia detection or implantable or ambulatory medical device performance;

receive the physiologic information from the sensor circuit, sensed from the patient over time, including during the first and the second time periods;

determine, based on the received physiologic information during the first time period, whether the onset condition is satisfied, and to detect the arrhythmia onset in response thereto;

in response to the detected arrhythmia onset, determine, based on the received physiologic information during the second time period, whether the exit condition is satisfied, and to detect the arrhythmia termination in response thereto; and

detect an arrhythmia episode based on an arrhythmia duration between the detected arrhythmia onset and the detected arrhythmia termination.