title: Assessing aortic stenosis using sample entropy of the phonocardiographic signal in dogs.
abstract: In aortic valve stenosis (AS), heart murmurs arise as an effect of turbulent blood flow distal to the obstructed valves. With increasing AS severity, the flow becomes more unstable, and the ensuing murmur becomes more complex. We hypothesize that these hemodynamic flow changes can be quantified based on the complexity of the phonocardiographic (PCG) signal. In this study, sample entropy (SampEn) was investigated as a measure of complexity using a dog model. Twenty-seven boxer dogs with various degrees of AS were examined with Doppler echocardiography, and the peak aortic flow velocity ( V(max)) was used as a reference of AS severity. SampEn correlated to V(max) with R = 0.70 using logarithmic regression. In a separate analysis, significant differences were found between physiologic murmurs and murmurs caused by AS ( p << 0.05), and the area under a receiver operating characteristic curve was calculated to 0.96. Comparison with previously presented PCG measures for AS assessment showed improved performance when using SampEn, especially for differentiation between physiological murmurs and murmurs caused by mild AS. Studies in patients will be needed to properly assess the technique in humans.
authors.affiliation: Department of Biomedical Engineering, Linköping University, SE-581 83 Linköping, Sweden. christer@imt.liu.se
authors.forename: C
authors.initials: C
authors.lastname: Ahlstrom Ast
authors.forename: K
authors.initials: K
authors.lastname: Höglund
authors.forename: P
authors.initials: P
authors.lastname: Hult
authors.forename: J
authors.initials: J
authors.lastname: Häggström
authors.forename: C
authors.initials: C
authors.lastname: Kvart
authors.forename: P
authors.initials: P
authors.lastname: Ask
mesh_terms: D000465:Algorithms; D000818:Animals; D001024:Aortic Valve Stenosis / Q000175:diagnosis* / Q000503:physiopathology*; D003936:Diagnosis, Computer-Assisted / Q000379:methods*; D004285:Dogs; D019277:Entropy; D010363:Pattern Recognition, Automated / Q000379:methods*; D010701:Phonocardiography / Q000379:methods*; D015203:Reproducibility of Results; D018401:Sample Size; D012680:Sensitivity and Specificity; D013018:Sound Spectrography / Q000379:methods*