Microphone placement evaluation for acoustic detection of coronary artery disease

Coronary artery disease (CAD) is the leading cause of death in the United States yet no screening tool exists. The acoustic approach detects CAD noninvasively with microphones placed at the chest. Identifying ideal microphone placement on the body may improve accuracy. Here we examine measurements from acoustic recordings taken on the chest at three positions: the base, middle and apex level of the heart. Eight CAD positive and 13 negative subjects were used. Approximate entropy (ApEn) and largest Lyapunov exponents (LLE) were used to analyze measurements. Using these features the apex recording produced 88%-54% sensitivity-specificity while the middle and base positions produced 63%-77% and 0%-92% sensitivity-specificity respectively. These results show LLE and ApEn to be sensitive to CAD related signals and suggest that the best location for analysis is above the apex of the heart.