The Unique Heart Sound Signature of Children with Pulmonary Artery Hypertension

Abstract

We hypothesized that vibrations created by the pulmonary circulation would create sound like the vocal cords during speech and that subjects with pulmonary artery hypertension (PAH) might have a unique sound signature. We recorded heart sounds at the cardiac apex and the second left intercostal space (2LICS), using a digital stethoscope, from 27 subjects (12 males) with a median age of 7 years (range: 3 months-19 years) undergoing simultaneous cardiac catheterization. Thirteen subjects had mean pulmonary artery pressure (mPAp) < 25 mmHg (range: 8-24 mmHg). Fourteen subjects had mPAp ≥ 25 mmHg (range: 25-97 mmHg). We extracted the relative power of the frequency band, the entropy, and the energy of the sinusoid formants from the heart sounds. We applied linear discriminant analysis with leave-one-out cross validation to differentiate children with and without PAH. The significance of the results was determined with a t test and a rank-sum test. The entropy of the first sinusoid formant contained within an optimized window length of 2 seconds of the heart sounds recorded at the 2LICS was significantly lower in subjects with mPAp ≥ 25 mmHg relative to subjects with mPAp < 25 mmHg, with a sensitivity of 93% and specificity of 92%. The reduced entropy of the first sinusoid formant of the heart sounds in children with PAH suggests the existence of an organized pattern. The analysis of this pattern revealed a unique sound signature, which could be applied to a noninvasive method to diagnose PAH.Keywords: pulmonary hypertension, congenital heart disease, auscultation, machine learning, language recognition. Untreated pulmonary artery hypertension (PAH) is a progressive, fatal disease. 1 It complicates many conditions and may affect up to 100 million people worldwide. 2,3 PAH is difficult to diagnose because symptoms appear late in the disease course and the findings on clinical examination are missed easily.The finding on auscultation of a loud pulmonary component of the second heart sound (S2) in PAH has led to the exploration of phonocardiographic associations between S2 and pulmonary artery pressure (PAp) in the time domain. 4-10 However, precise demarcation, timing, and segmentation of the components of S2 remain challenging. [7][8][9][11][12][13] We have explored instead quantitative information in the frequency domain of heart sounds that distinguish between subjects with and without PAH. 14 The relative power of the frequencies between 21 and 22 Hz of the heart sounds recorded at the second left intercostal space (2LICS) was significantly reduced in subjects with PAH. 14 However, there was a 22% error in detecting PAH. Therefore, by investigating further the recordings in these same subjects, we sought to explore other features of the heart sounds in this specific frequency domain that might contain a unique feature that would identify subjects with PAH.Normal speech patterns have a unique signature related to vocal cord vibration, which can be used, for example, to recognize a speaker as male or female...

Speech Encoding Scheme for the Extra-Cochlear Pulsed Electrical Stimulation System

“…Table 1 lists the signal processing parameters used in the program. These analytic parameters were identical to previous researches [11] [12] [13], and which allows us to compare our data with these results. After formant frequencies extraction, click train with a repetition rate similar to the formant frequencies were generated.…”

“…First formant (F1) and second formant (F2) frequencies were extracted by a publicly available MATLAB-based script. The program was commonly used and described in several previous studies [11] [12] [13]. It implements liner predictive coding (LPC) analysis, and LPC was calculated every 2.7 ms over 5.4 ms Hanning windowed segments at 8 kHz sampling rate with an LPC order equal to 8.…”

Acoustic diagnosis of pulmonary hypertension: automated speech- recognition-inspired classification algorithm outperforms physicians

“…We suggest that automated digitally acquired heart sound recordings may be used to screen for PH in the community and prompt referral to specialist centers for echocardiography and cardiac catheterization to reduce the delay in diagnosis and treatment experienced by many patients 3 4 5 16 . The high false positive and negative rates need to be reduced and might be accomplished with an expanded training set or an algorithm that incorporates both our current algorithm and other features that differentiate heart sounds of patients with PH such as reduced entropy 9 .…”

“…However, precise automated localization of the second heart sound and measurement of the splitting interval between the components of the second heart sound have proved difficult. We have taken an alternative approach and investigated the diagnosis of PH by harnessing electronic stethoscope recordings with advanced signal processing and the application of speech and language recognition algorithms 8 9 10 . Automated speech-recognition-inspired-classification algorithms simultaneously take into account many aspects of a heart sound signal, including the shape, frequency components, and amplitude.…”

Digital stethoscopes in paediatric medicine

“…Frequency analysis on heart sound recordings displayed distinct characteristics found in children with PAH when compared to controls . This analysis allowed for the non‐invasive demonstration of a unique visual signature for this specific condition , demonstrating that digital auscultation may be effective in differentiating children with PAH from those with a normal pulmonary artery pressure. This could prove to be useful as a diagnostic tool.…”