System and method for indicating coronary artery disease risk based on low and high frequency bands

A system for detection of frequency power for diagnosing of coronary artery disease (CAD), comprising:

• an acoustic sensor adapted to be placed on the chest of a patient, and to generate acoustic signals SA;
• at least one memory adapted to store acoustic signals SA from the acoustic sensor;
• and
• a control unit adapted to receive said acoustic signals SA from the memory;
• wherein the control unit further comprises:
• an identification unit adapted to identify diastolic or systolic periods in a predetermined time period of the stored acoustic signals SA, and to generate a period signal SP indicating said identified periods;
• a filtering unit adapted to apply at least one filter to said identified periods and to generate a low frequency band signal SLFB indicating low frequency bands of said identified periods, and to generate a high frequency band signal SHFB indicating high frequency bands of said identified periods;
• and
• a calculation unit adapted to estimate the power in said low frequency band of said identified periods, and that said calculation unit is adapted to normalize said estimated power over other, higher frequency band, said calculation unit is further adapted to calculate a low frequency power measure based upon said estimated and normalized power and to generate a low frequency power measure signal SLFP indicating said low frequency power measure, and wherein said calculation unit in addition is adapted to calculate a high frequency feature measure based upon an estimated feature in high frequency bands of said periods and to generate a high frequency feature measure signal SHFF indicating said high frequency feature measure;
• wherein said system further comprising a risk determining unit adapted to determine a risk of coronary artery disease (CAD) by combining said low frequency power measure and said high frequency power measure and to compare a resulting combined power ratio value with a further feature reference value for CAD and to generate a combined risk-of-CAD-signal S′CAD indicating said risk in dependence of said comparison.

A method for detecting frequency power for diagnosing of coronary artery disease (CAD) using a system for detection of low frequency power, the method comprising:

• recording acoustic data with said system having an acoustic sensor placed on the chest of a patient and generating acoustic signals SA indicating said data;
• identifying diastolic or systolic periods in a predetermined time period of the stored acoustic data, and generating a period signal Sp indicating said identified periods;
• applying at least one filter to the period signal Sp and generating a low frequency band signal SLFB indicating low frequency bands of said identified periods and generating a high frequency band signal SHFB indicating high frequency bands of said identified periods;
• estimating the power in said low frequency bands of said identified periods;
• normalizing said estimated power over other, higher frequency band;
• calculating a low frequency power measure based upon said estimated and normalized power, and generating a low frequency power measure signal SLFP indicating said low frequency power measure;
• calculating a high frequency feature measure based upon an estimated feature in high frequency bands of said periods and to generate a high frequency feature measure signal SHFF indicating said high frequency feature measure, and
• combining said low frequency power measure and said high frequency power measure and comparing a resulting combined power ratio value with a further feature reference value for CAD to generate a combined risk-of-CAD-signal S′CAD indicating said risk in dependence of said comparison.