Abstract:
A system and method for the efficient implementation of a complex exercise test is disclosed. A rule interpreter synthesizes interpretation statements based upon the processing of collected physiological data and user entered data with a series of exercise test interpretation rules. These statements aid a clinician in interpreting exercise test results by identifying detected abnormal or borderline conditions.

Description:
BACKGROUND OF THE INVENTION  
       [0001]     Computerized electrocardiographic (ECG) interpretation has become widely accepted in the medical field. Physicians frequently utilize this technique as a back-up to their own interpretation of ECG results, or as a check to ensure that abnormal ECG waveform morphologies have not been overlooked. The interpretation of ECG waveforms is difficult and even physicians may be misled due to the complexity of the analysis that must be performed. In many instances, multiple tests or algorithms must be utilized to obtain a conclusive result as the result of a single test may fail to distinguish correctly between healthy and pathological ECGs or between different ECG pathologies.  
         [0002]     Exercise tests utilizing a treadmill or a stationary bicycle have increased in popularity as a useful diagnostic tool of cardiac health. One advantage of exercise tests over resting ECG tests is the increased number of physiological measurement values that may be obtained as the body is put under a stress and then recovers from that stress. These physiological measurement values have the power to predict morbidity/mortality rates, coronary artery disease, and also can describe the functional exercise response of a patient. An ideal physician would take all of these physiological measurements from the exercise stress test and compare the measurements to the known limits for each of these values as determined by scientific experiments to come to a complete assessment of the patient&#39;s health as determined by the exercise test.  
         [0003]     Due to recent increases in the number of useful physiological measurement values and applicable analysis algorithms and limits, it has become very difficult for a physician to know and apply everything that is needed for a complete assessment of the exercise test. Additionally, it is increasingly difficult for the physician to understand the meaning of an algorithm result and to identify pathologies that are identified with combinational algorithms that compare limits of multiple measurement values. Therefore, it is desirable in the field of ECG analysis for a system that provides a complete assessment of an exercise test to help a physician manage the high number of physiological measurement values with increasingly complex diagnostic algorithms.  
       SUMMARY OF THE INVENTION  
       [0004]     Due to the increasing numbers of exercise test analysis options and the complexity of these diagnostic algorithms, it is therefore advantageous to develop a computerized exercise test interpretation system as in the present invention. A database of exercise test interpretation rules is created whereby a rule interpreter may take the physiological measurement values recorded from an exercise test combined with additional clinician-entered data and process this information with the desired exercise test interpretation rules to produce an exercise test interpretation. This interpretation may comprise interpretation statements along with additional reasoning texts that particularize and point out the specific exercise test interpretation rules that were the cause for the resultant interpretation.  
         [0005]     The present invention facilitates the implementation of an exercise stress test by allowing the rule interpreter to guide the interpreting physician with the exercise test measurements by pointing out patient conditions that the physician should further investigate, providing support to physician interpretations of exercise measurement values, and ensuring that abnormal exercise measurement values are not overlooked by the physician. In an embodiment of the present invention, the interpretation statements also include physiological location information to supplement the interpretation statements regarding cardiac fitness. In a still further embodiment of the present invention, an exercise test interpretation may comprise either the interpretation statements or the reasoning texts as selected by the physician.  
         [0006]     Various other features, objects and advantages of the invention will be made apparent from the following description taken together with the drawings.  
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0007]     The drawings illustrate the best mode presently contemplated of carrying out the invention. In the drawings:  
         [0008]      FIG. 1  is a schematic diagram of the operation of the exercise test interpretation of the present invention;  
         [0009]      FIG. 2  depicts a generalized depiction of an embodiment of the exercise test interpretation display; and  
         [0010]      FIG. 3  depicts a graphical display of an embodiment of the exercise test interpretation of the present invention. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0011]      FIG. 1  depicts a flowchart of the operation of the present invention. A clinician&#39;s analysis of the results recorded from a patient&#39;s exercise stress test is facilitated by the exercise test interpretation system of the present invention  10 . This analysis is provided through the use of a rule interpreter  12 . The rule interpreter  12  uses exercise test interpretation rules stored in a rule database  14  to interpret the results of an exercise stress test based upon both the measured physiological data  16  recorded from the patient during the exercise test as well as additional patient information  18  that is added by the clinician. The rule interpreter  12  applies the selected rules from the rule database  14  to the physiological data  16  and the clinician-entered data  18  to create an interpretation  20  of the results of the exercise test.  
         [0012]      FIG. 2  depicts an interpretation  20  of an embodiment of the present invention. The interpretation  20  comprises a plurality of interpretation statements depicted here as statements A-C,  24 - 26  respectively, and a plurality of associated reasoning texts  27 - 30 , respectively. In an embodiment of the present invention, the interpretation statements  24 - 26  are divided into three statement groups for analysis. These statement groups may comprise, but are not limited to, risk prediction statements, cardiac functional response statements, and coronary artery disease statements. Additionally, an overall summary statement  32  may be included in the interpretation  20 .  
         [0013]     An exercise test interpretation  20  may comprise any number of interpretation statements  24 - 26  from any statement grouping as is identified by the rule interpreter  12  in analyzing the physiological and entered data  16 ,  18 . Each rule that is stored in the rule database  14  represents a pathological condition resulting in an abnormal or borderline exercise test. This rule may comprise value limits and/or ranges for physiological data values or may comprise a Boolean statement combining one or more values and/or value ranges or limits.  
         [0014]     The fulfillment of a rule results in the textual display of an interpretation statement  24 - 26 . The rule that was fulfilled to trigger the display of the statement  24 - 26  is displayed as the associated reasoning text  27 - 30 . Often, as with statement A, each statement has one reasoning text, Reasoning A  27 . However, for example, statement C  26  is supported by two reasoning texts, Reasoning C  29  and Reasoning D  30 . This depicts a situation in which two rules were fulfilled that resulted in the same diagnostic statement. Additionally, in an embodiment of the invention, in cases of the detection of coronary artery disease, where it is possible to determine the location of the detected abnormality, in an embodiment of the present invention this location is also displayed as a location statement  34  in the interpretation statement  24 . If, for example, the exercise test was performed with a traditional 12-lead ECG, then the affected areas of the heart may be determined by comparing the signals of the precordial electrodes. In an embodiment of the present invention, the overall statement  32  indicates if any abnormal or borderline condition has been detected by the exercise test, or if the physiological data appears to be normal.  
         [0015]     Referring back to  FIG. 1 , the clinician enters information about the patient and the exercise test to the rule interpreter for use in analyzing the exercise test. This clinician-entered data  18  may comprise standard physiological data such as age, gender, race, height, and weight but may also include, in an embodiment of the invention, patient information such as whether the patient is currently using a beta blocker or if the patient is or has experienced angina. In an embodiment of the invention, additional information may be included such as the type of the test being performed as well as the test equipment and the test duration. These additional test information values provide information for the selection of the proper exercise test rules from rule database  14  to apply in the current test. This may be important as some exercise test algorithms such as the Duke Treadmill Score (DTS) or the Metabolic Equivalent (MET) require this additional test information, to compute the values associated with these tests.  
         [0016]     As the patient undergoes the exercise test, physiological measurements  16  are recorded and then reported to the rule interpreter  12 . The physiological measurements  16  may include recorded data such as the detected raw 5-lead or 12-lead ECG measurements but may also include a variety of calculated values representing additional physiological measurements. These calculated values may also include information processed from the recorded ECG waveforms. This processed information may include ST depression, detection of arrhythmia, or the direction of the ST/HR loop, but many other processed values are envisioned as being within the present invention. It is understood that the necessary physiological measurements  16  that are recorded and sent to rule interpreter  12  is dependent upon the requirements of the rules in the exercise test rule database  14 .  
         [0017]     As stated above, the exercise test rules in rule database  14  are comprised of physiological measurement limits or ranges that signify a particular pathology. These rules may also comprise Boolean statements comprising one or more physiological measurement limit statements or user entered data values. In an embodiment of the present invention, the rules are divided into groups based upon the types of pathology to which they are directed. In the risk prediction group, rules such as a DTS of less than −10 or heart rate recovery of less than 12 bpm, indicate a risk of morbidity or mortality. On the other hand, if T-wave alternans are greater than or equal to 30 μV, then there exists an increased risk of malignant arrhythmias. In the group of rules for determining cardiac functional response, an embodiment of the present invention may use a rule such as if MET&#39;s are ≦ to 5, then the patient has an insufficient exercise capacity. Alternatively, if the heart rate used is less ≦0.8, then the patient is experiencing chronotropic incompetence. Finally, rules that address the likelihood of coronary artery disease may include an ST depression of ≧1 millimeter, an ST/HR slope of ≧2.4 microvolts per BPM, or an ST/HR loop that is counterclockwise, or ST/HR hysteresis that is ≧0.25 millimeters. The rules for likelihood of coronary artery disease also include specific location indicators based upon the ECG leads in which the rules are fulfilled to also indicate the relative location of the CAD. It is understood that these values and descriptions are not intended to be limiting on the scope of he present invention, but rather are exemplary of the rules that may be used with the present invention.  
         [0018]      FIG. 3  is an exemplary depiction of a graphical user interface (GUI)  36  of an embodiment of the present invention. The GUI  36  comprises sections for clinician-entered data  18 , physiological measurement data  16 , and the resulting exercise test interpretation  20 . The clinician-entered data  18  includes information regarding the patient&#39;s age  38 , gender  40 , race  42 , height  44 , and weight  46 . Clinician-entered data  18  includes additional information, such as use of a beta blocker  48  and angina experience  50 , as well as exercise test information, such as test type  52  and test equipment  54 . Physiological measurement data  16  may include total exercise time  56 , as well as data such as heart rate  58 , blood pressure  60 , arrhythmia detection  62 , ST/HR hysteresis  68 , HR recovery  70 , and Maximum TWA  72 .  
         [0019]     The exercise test interpretation section  20  depicts in exemplary detail the diagram depicted in  FIG. 2 . In reading the interpretation  20 , statement  24  indicates that the patient has an increased risk of morbidity/mortality. The associated reasoning  27  states that this conclusion is based upon a DTS of ≦=−10, which was previously stated as a potential exercise test interpretation rule. In the statement concerning CAD risk  26 , there are multiple reasoning statements  29 ,  30  that indicate that multiple CAD detection rules were fulfilled. Additionally, location indication  34  identifies the areas of the heart affected by CAD. Finally, the overall statement  32  identifies that this patient has had an abnormal exercise test response.  
         [0020]     Referring back to  FIG. 1 , in an embodiment of the present invention, a clinician and/or hospital administrator may include exercise rule updates  22  to the exercise test rule database  14 . These exercise rule updates would allow the rule database to improve along with the science in this field. It would also allow for an institution to determine desirable standardized tests to be performed in similar situations as well as allow a clinician the freedom and/or flexibility to include his own additional rules.  
         [0021]     In a still further embodiment of the present invention, the clinician is allowed to select the desired rules from the exercise test rule database  14  to be used in the rule interpreter  12  for each exercise test there is performed. This allows for the clinician to create a more individually tailored test for each patient based upon the condition of the patient and/or the medical concern surrounding that patient.  
         [0022]     In a further embodiment of the present invention, the exercise test interpretation may include only the interpretation statements  24  or only the reasoning statements  26 . This option allows the clinician to tailor the results of the exercise test interpretation to be presented in a way that is most desirable for his overall diagnosis of the patient&#39;s condition.  
         [0023]     This written description uses examples to disclose the invention, including the best mode and also to enable any person skilled in the art to make and use the invention. The patentable scope of the invention is defined by the claims, and may include other examples that occur to those skilled in the art. Such other examples are intended to be within the scope of the claims if they have structural elements that do not differ from the literal language of the claims, or if they include equivalent structural elements of insubstantial differences from the literal language of the claims.  
         [0024]     Various alternative and embodiments are contemplated as being within the scope of the following claims, particularly pointing out and distinctly claiming the subject matter regarded as the invention.