Absent fourth heart sound as a marker of adverse events in hypertrophic cardiomyopathy with sinus rhythm.

BACKGROUND: Patients with hypertrophic cardiomyopathy (HCM) in sinus rhythm commonly show the fourth heart sound (S4). The lack of S4 may be a marker of impaired atrial function in HCM patients with sinus rhythm. METHODS AND RESULTS: This retrospective study consisted of 47 patients with HCM who had undergone phonocardiography and a cardiopulmonary exercise test. The primary outcome was a composite of cardiac death, stroke, hospitalization for worsening heart failure, and newly developed atrial fibrillation (AF). S4 was detected in 38 of 43 patients with sinus rhythm (88%). Peak oxygen consumption was the highest in 38 sinus rhythm patients with S4 (23.6 ± 5.6 mL/kg/min), middle in five sinus rhythm patients without S4 (19.3 ± 6.7 mL/kg/min), and lowest in four patients with AF (15.7 ± 3.3 mL/kg/min, p = 0.01). After a median of 40.5 months, the incidence of the primary outcome was higher in patients without S4 than in those with S4 (33% vs. 8%; hazard ratio, 6.17; 95% confidence interval, 1.02 - 37.4; p = .04) and higher in sinus rhythm patients without S4 than in those with S4 (60% vs. 8%; hazard ratio, 12.05; 95% confidence interval, 2.31 - 71.41; p = .007). CONCLUSIONS: The absence of S4 on phonocardiography was associated with impaired exercise tolerance and adverse cardiac events in HCM patients with sinus rhythm.

Heart Sound Analysis in Individuals Supported With Left Ventricular Assist Devices.

OBJECTIVE: LVADs are surgically implanted mechanical pumps that improve survival rates of individuals with advanced heart failure. LVAD therapy is associated with high morbidity, which can be partially attributed to challenges with detecting LVAD complications before adverse events occur. Current methods used to monitor for complications with LVAD support require frequent clinical assessments at specialized LVAD centers. Analysis of recorded precordial sounds may enable real-time, remote monitoring of device and cardiac function for early detection of LVAD complications. The dominance of LVAD sounds in the precordium limits the utility of routine cardiac auscultation of LVAD recipients. In this work, we develop a signal processing pipeline to mitigate sounds generated by the LVAD. METHODS: We collected in vivo precordial sounds from 17 LVAD recipients, and contemporaneous echocardiograms from 12 of these individuals, to validate heart valve closure timings. RESULTS: We characterized various acoustic signatures of heart sounds extracted from in vivo recordings, and report preliminary findings linking fundamental heart sound characteristics and level of LVAD support. CONCLUSION: Mitigation of LVAD sounds from precordial sound recordings of LVAD recipients enables analysis of intrinsic heart sounds. SIGNIFICANCE: These findings provide proof-of-concept evidence of the clinical utility of heart sound analysis for bedside and remote monitoring of LVAD recipients.

Diseño, elaboración y validación de un simulador realista y de bajo costo para exploración cardiaca / Design, assembly and validation of a low-cost, high-fidelity simulator for heart exploration

Resumen Introducción: La exploración cardiaca es una competencia clínica fundamental que requiere exposición o entrenamiento continuo. La baja disponibilidad y accesibilidad de pacientes con patología cardiaca constituye una barrera para adquirir esta competencia. Se han documentado inadecuadas habilidades de auscultación cardiaca en estudiantes de medicina, residentes y médicos graduados. Objetivo: Elaborar y validar un simulador de alta fidelidad y bajo costo para exploración cardiaca. Métodos: Se diseñó y elaboró un simulador para exploración cardiaca, realista y de bajo costo capaz de reproducir ruidos cardiacos normales. Posteriormente se realizó la validación del simulador por un grupo de expertos que emitieron su opinión de acuerdo con una escala tipo Likert. Resultados: El 94 % afirmó que el simulador motiva el aprendizaje de la exploración cardiaca y 92 % lo consideró un modelo realista; 91 % consideró que el simulador es una herramienta atractiva para fortalecer el aprendizaje y 98 % recomendó seguir utilizándolo. Conclusiones: El uso del simulador facilita la adquisición de competencias y estimula el aprendizaje en el estudiante, lo cual puede ser atribuido a la práctica deliberada, a un mayor tiempo de exposición y a la interacción cognitiva.

Abstract Introduction: Heart exploration is an essential clinical competence that requires continuous training and exposure. Low availability and accessibility to patients with heart disease constitutes a barrier to acquiring this competence. Inadequate cardiac auscultation skills in medical students, residents, and graduate physicians have been documented. Objective: To develop and validate a low-cost, high-fidelity simulator for heart exploration. Methods: A low-cost, high-fidelity heart examination simulator capable of reproducing normal cardiac sounds was designed and developed. Subsequently, the simulator was validated by a group of experts who gave their opinion according to a Likert scale. Results: Ninety-four percent agreed that the simulator motivates the learning of heart exploration, and 92 % considered it to be a realistic model; 91 % considered that the simulator is an attractive tool to reinforce learning and 98 % recommended its further use. Conclusions: The use of the simulator facilitates the acquisition of skills and stimulates learning in the student, which can be attributed to repeated practice, longer exposure time and cognitive interaction.

Tele-Clinic Visits in Pediatric Patients with Marfan Syndrome Using Parentally Acquired Echocardiography.

OBJECTIVE: To test feasibility of tele-clinic visits using parentally acquired vital signs and focused echocardiographic images in patients with Marfan syndrome. STUDY DESIGN: We included patients with Marfan syndrome aged 5-19 years followed in our clinic. We excluded patients with Marfan syndrome and history of previous aortic root (AoR) surgery, cardiomyopathy, arrhythmia, or AoR ≥4.5 cm. We trained parents in-person to acquire focused echocardiographic images on their children using a hand-held device as well as how to use a stadiometer, scale, blood pressure (BP) machine, and a digital stethoscope. Before tele-clinic visits, parents obtained the echocardiographic images and vital signs. We compared tele-clinic and on-site clinic visit data. Parental and clinic echocardiograms were independently analyzed. RESULTS: Fifteen patient/parent pairs completed tele-clinic visits, conducted at a median of 7.0 (IQR 3.0-9.9) months from the in-person training session. Parents took a median of 70 (IQR 60-150) minutes to obtain the height, weight, heart rate, BP, cardiac sounds, and echocardiographic images before tele-clinic visits. Systolic BP was greater on-site than at home (median +13 mm Hg, P = .014). Height, weight, diastolic BP, heart rate, and AoR measurements were similar. CONCLUSIONS: This study provides information for implementing tele-clinic visits using parentally acquired vital signs and echocardiographic images in patients with Marfan syndrome. The results show that tele-clinic visits are feasible and that parents were able to obtain focused echocardiographic images on their children. TRIAL REGISTRATION: ClinicalTrials.gov: NCT03581682.

Gated recurrent unit-based heart sound analysis for heart failure screening.

BACKGROUND: Heart failure (HF) is a type of cardiovascular disease caused by abnormal cardiac structure and function. Early screening of HF has important implication for treatment in a timely manner. Heart sound (HS) conveys relevant information related to HF; this study is therefore based on the analysis of HS signals. The objective is to develop an efficient tool to identify subjects of normal, HF with preserved ejection fraction and HF with reduced ejection fraction automatically. METHODS: We proposed a novel HF screening framework based on gated recurrent unit (GRU) model in this study. The logistic regression-based hidden semi-Markov model was adopted to segment HS frames. Normalized frames were taken as the input of the proposed model which can automatically learn the deep features and complete the HF screening without de-nosing and hand-crafted feature extraction. RESULTS: To evaluate the performance of proposed model, three methods are used for comparison. The results show that the GRU model gives a satisfactory performance with average accuracy of 98.82%, which is better than other comparison models. CONCLUSION: The proposed GRU model can learn features from HS directly, which means it can be independent of expert knowledge. In addition, the good performance demonstrates the effectiveness of HS analysis for HF early screening.

Bilateral multiple pulmonary artery aneurysms associated with cavitary pulmonary tuberculosis: a case report.

BACKGROUND: Pulmonary artery aneurysms constitute <1% of aneurysms occurring in the thoracic cavity. Congenital cardiac defects are responsible for the majority (>50%) of cases, however, pulmonary artery aneurysm is a rare sequelae of pulmonary tuberculosis reported in about 5% of patients with chronic cavitary tuberculosis on autopsy. The natural history of this potentially fatal condition remains poorly understood and guidelines for optimal management are controversial. CASE PRESENTATION: A 24-year-old man, a nursing student of African descent, was referred to us from an up-country regional hospital with a 4-week history of recurrent episodes of breathlessness, awareness of heartbeats and coughing blood 3 weeks after completing a 6-month course of anti-tuberculosis drugs. A physical examination revealed conjuctival and palmar pallor but there were no stigmata of connective tissue disorders, systemic vasculitides or congenital heart disease. An examination of the cardiovascular system revealed accentuated second heart sound (S2) with early diastolic (grade 1/6) and holosystolic (grade 2/6) murmurs at the pulmonic and tricuspid areas respectively. Blood tests showed iron deficiency anemia, prolonged bleeding time, and mild hyponatremia. A chest radiograph revealed bilateral ovoid-shaped perihilar opacities while a computed tomography scan showed bilateral multiple pulmonary artery pseudoaneurysms with surrounding hematoma together with adjacent cystic changes, consolidations, and tree-in-bud appearance. Our patient refused to undergo surgery and died of aneurismal rupture after 9 days of hospitalization. CONCLUSIONS: The presence of intractable hemoptysis among patients with tuberculosis even after completion of anti-tuberculosis course should raise an index of suspicion for pulmonary artery aneurysm. Furthermore, despite of its rarity, early recognition and timely surgical intervention of pulmonary artery aneurysm is crucial to reducing morbidity and preventing the attributed mortality.

Usefulness of the second heart sound for predicting pulmonary hypertension in patients with interstitial lung disease / Utilidade da segunda bulha cardíaca na predição de hipertensão pulmonar em portadores de doenças intersticiais pulmonares

CONTEXT AND OBJECTIVE: P2 hyperphonesis is considered to be a valuable finding in semiological diagnoses of pulmonary hypertension (PH). The aim here was to evaluate the accuracy of the pulmonary component of second heart sounds for predicting PH in patients with interstitial lung disease. DESIGN AND SETTING: Cross-sectional study at the University of Brasilia and Hospital de Base do Distrito Federal. METHODS: Heart sounds were acquired using an electronic stethoscope and were analyzed using phonocardiography. Clinical signs suggestive of PH, such as second heart sound (S2) in pulmonary area louder than in aortic area; P2 > A2 in pulmonary area and P2 present in mitral area, were compared with Doppler echocardiographic parameters suggestive of PH. Sensitivity (S), specificity (Sp) and positive (LR+) and negative (LR-) likelihood ratios were evaluated. RESULTS: There was no significant correlation between S2 or P2 amplitude and PASP (pulmonary artery systolic pressure) (P = 0.185 and 0.115; P= 0.13 and 0.34, respectively). Higher S2 in pulmonary area than in aortic area, compared with all the criteria suggestive of PH, showed S = 60%, Sp= 22%; LR+ = 0.7; LR- = 1.7; while P2> A2 showed S= 57%, Sp = 39%; LR+ = 0.9; LR- = 1.1; and P2 in mitral area showed: S= 68%, Sp = 41%; LR+ = 1.1; LR- = 0.7. All these signals together showed: S= 50%, Sp = 56%. CONCLUSIONS: The semiological signs indicative of PH presented low sensitivity and specificity levels for clinically diagnosing this comorbidity.

RESUMO CONTEXTO E OBJETIVO: Hiperfonese de P2 tem sido considerada como achado valoroso no diagnóstico semiológico de hipertensão pulmonar (HP). O objetivo foi de avaliar a acurácia do componente pulmonar da segunda bulha cardíaca em predizer HP nos pacientes portadores de doenças intersticiais pulmonares. TIPO DE ESTUDO E LOCAL: Estudo transversal na Universidade de Brasília e Hospital de Base do Distrito Federal. MÉTODOS: Os sons cardíacos foram adquiridos com estetoscópio eletrônico e analisados por fonocardiografia. Os sinais clínicos sugestivos de HP, como B2 mais intensamente audível em área pulmonar que aórtica, P2 > A2 na área pulmonar e P2 presente em área mitral foram confrontados com parâmetros cardiográficos no exame de Doppler sugestivos de HP. Sensibilidade (S), especificidade (E), razões de verossimilhança positiva (RV+) e negativa (RV-) foram avaliados. RESULTADOS: Não houve correlação significativa entre amplitude de B2 e P2 e a PSAP (pressão sistólica arterial pulmonar) (P = 0,185 e 0,115; P = 0,13 e 0,34; respectivamente). A análise da presença de B2 mais intensa na área pulmonar que aórtica, quando comparada a todos os critérios sugestivos de HP, mostrou S = 60%; E = 22%; RV+ = 0,7; RV- = 1,7; enquanto P2 > A2 mostrou: S = 57%; E = 39%; RV+ = 0,9; RV- = 1,1; e P2 no foco mitral mostrou: S = 68%; E = 41%; RV+ = 1,1; RV- = 0,7. Todos os sinais juntos mostraram S = 50%; E = 56%. CONCLUSÃO: Os sinais semiológicos indicativos de HP apresentam baixos valores de especificidade e sensibilidade para diagnóstico clínico dessa comorbidade.

Segmentação automática para classificação digital de sinais de fonocardiograma / Automatic segmentation for signal classification of digital phonocardiogram

Com o avanço tecnológico surgem novas ferramentas que auxiliam os médicos no diagnóstico de diversas doenças. Na área cardiovascular, após permanecer por um longo período em segundo plano, a ausculta cardíaca voltou a ser muito utilizada devido ao surgimento, no mercado, de estetoscópios digitais. Tais aparelhos contam com novos recursos tecnológicos que permitem a captação e a análise de dados de forma automática, oferecendo mais informações ao profissional da área. Levando em conta essa nova ascensão da área de Fonocardiografia,o presente trabalho se dedicou à separação das bulhas S1 e S2 por meio de ferramentas computacionais, com o propósito de auxiliar médicos não especialistas em Cardiologia a verificar a existência de possíveis anormalidades no som cardíaco. Acreditando na possibilidade de este procedimento vir a ser utilizado posteriormente para auxiliar no reconhecimento de padrões dos sons cardíacos, este trabalho se propôs a criar um algoritmo para detecção automática de anormalidades que afetam as bulhas S1 e S2. Assim, aplicou-se a técnica de Wavelet sobre uma base de dados de sons cardíacos constituída de 1209 bulhas...

Can we predict the presence of coronary lesions from blood pressure measurement? A new clinical method.

The roles of arterial function and structure in cardiovascular physiology have expanded with the development of a variety of parameters that evaluate arterial stiffness. Markers of arterial stiffness have been correlated with cardiovascular outcomes. We aimed to find a simple, clinical, noninvasive method to predict atherosclerosis that leads to the development of coronary artery disease (CAD). We aimed to find a simple, clinical, noninvasive method to predict atherosclerosis that leads to the development of CAD. We included 100 cases that underwent coronary angiography in our center owing to different indications. The blood pressure in all cases was measured by two different observers. The oscillatory systolic blood pressure (OSBP) was defined as the point at which the mercury began to oscillate to a minimum level of 1 mm Hg. The auscultatory systolic blood pressure (AUSBP) was defined as the first Korotkoff sound. The difference between OSBP and AUSBP was calculated and called the oscillatory gap (OG). The correlation between the OG and the presence of coronary lesion in coronary angiography was statistically calculated. The study populations had a mean age of 57.3±9 years. The mean±s.d. OG was 14.44±10.44. There was a highly significantly positive correlation between the OG and the presence of coronary artery lesions (r=0.399 and P-value <0.000). There was also a significantly positive correlation between the presence of hypertension and the OG (r=0.376 and P-value <0.000). The difference between OSBP and AUSBP could be used as a simple method to detect atherosclerotic arterial changes. This method could indicate the degree of arterial stiffness. There was a significantly positive correlation between this new indicator of arterial stiffness and the presence of CAD. Any patient with a wide gap between OSBP and AUSBP should be treated early with antihypertensive drugs and statins before the development of CAD.

Monitoring cardiac stress using features extracted from S1 heart sounds.

It is known that acoustic heart sounds carry significant information about the mechanical activity of the heart. In this paper, we present a novel type of cardiac monitoring based on heart sound analysis. Specifically, we study two morphological features and their associations with physiological changes from the baseline state. The framework is demonstrated on recordings during laparoscopic surgeries of 15 patients. Insufflation, which is performed during laparoscopic surgery, provides a controlled, externally induced cardiac stress, enabling an analysis of each patient with respect to their own baseline. We demonstrate that the proposed features change during cardiac stress, and the change is more significant for patients with cardiac problems. Furthermore, we show that other well-known ECG morphology features are less sensitive in this specific cardiac stress experiment.

Assessment of time-frequency representation techniques for thoracic sounds analysis.

A step forward in the knowledge about the underlying physiological phenomena of thoracic sounds requires a reliable estimate of their time-frequency behavior that overcomes the disadvantages of the conventional spectrogram. A more detailed time-frequency representation could lead to a better feature extraction for diseases classification and stratification purposes, among others. In this respect, the aim of this study was to look for an omnibus technique to obtain the time-frequency representation (TFR) of thoracic sounds by comparing generic goodness-of-fit criteria in different simulated thoracic sounds scenarios. The performance of ten TFRs for heart, normal tracheal and adventitious lung sounds was assessed using time-frequency patterns obtained by mathematical functions of the thoracic sounds. To find the best TFR performance measures, such as the 2D local (ρ(mean)) and global (ρ) central correlation, the normalized root-mean-square error (NRMSE), the cross-correlation coefficient (ρ(IF)) and the time-frequency resolution (res(TF)) were used. Simulation results pointed out that the Hilbert-Huang spectrum (HHS) had a superior performance as compared with other techniques and then, it can be considered as a reliable TFR for thoracic sounds. Furthermore, the goodness of HHS was assessed using noisy simulated signals. Additionally, HHS was applied to first and second heart sounds taken from a young healthy male subject, to tracheal sound from a middle-age healthy male subject, and to abnormal lung sounds acquired from a male patient with diffuse interstitial pneumonia. It is expected that the results of this research could be used to obtain a better signature of thoracic sounds for pattern recognition purpose, among other tasks.

Spectral analysis of the heart sounds in children with and without pulmonary artery hypertension.

BACKGROUND: Pulmonary artery hypertension (PAH) is difficult to recognize clinically. Digital stethoscopes offer an opportunity to re-evaluate the diagnosis of PAH. We hypothesized that spectral analysis of heart sound frequencies using recordings from a digital stethoscope would differ between children with and without PAH. METHODS: We recorded heart sounds using a digital stethoscope from 27 subjects (12 males) with a median age of 7 years (3 months to 19 years) undergoing simultaneous cardiac catheterization. 13 subjects had a mean pulmonary artery pressure (mPAp)<25 mm Hg (8-24 mm Hg). 14 subjects had a mPAp≥25 mm Hg (25-97 mm Hg). We applied the fast Fourier transform, power spectral analysis, separability testing, and linear discriminant analysis with leave-one-out cross-validation to the heart sounds recorded from the cardiac apex and 2nd left intercostal space (LICS) to examine the frequency domain. The significance of the results was determined using a t-test and rank-sum test. RESULTS: The relative power of the frequencies 21-22 Hz of the heart sounds recorded at the 2nd LICS was decreased significantly in subjects mPAp≥25 mm Hg versus<25 mm Hg. CONCLUSIONS: Heart sound signals of patients with PAH contain significantly less relative power in the band 21-22 Hz compared to subjects with normal PAp. Information contained in the frequency domain may be useful in diagnosing PAH and aid the development of auscultation based techniques for diagnosing PAH. In the future, utilizing the diagnostic information contained in heart sounds recordings may require analysis of both the time and frequency domains.

A floating right heart thrombus in transit across tricuspid valve causing an endocardial friction rub.

We report a 42-year-old lady on combined oral contraceptive pills with deep venous thrombosis and mild pulmonary embolism, who developed shock, while being treated with heparin. On auscultation, there was an unexpected loud, superficial, squeaky, triphasic friction rub over the left lower parasternal area. Simultaneous echocardiogram revealed a large serpiginous, freely floating mass in right atrium, prolapsing freely to right ventricular inlet across the tricuspid valve. The endocardial friction rub persisted for about 24 h as long as the thrombus was intracardiac and disappeared when the thrombus disappeared from right heart, occluding the proximal left pulmonary artery. She died due to shock awaiting surgery. We highlight that such a rub in a patient with deep venous thrombosis, though rare, may be an important clue to impending pulmonary embolism.

Clinical evaluation of the 3M Littmann Electronic Stethoscope Model 3200 in 150 cats.

Detection of murmurs and gallops may help to identify cats with heart disease. However, auscultatory findings may be subject to clinically relevant observer variation. The objective of this study was to evaluate an electronic stethoscope (ES) in cats. We hypothesized that the ES would perform at least as well as a conventional stethoscope (CS) in the detection of abnormal heart sounds. One hundred and fifty consecutive cats undergoing echocardiography were enrolled prospectively. Cats were ausculted with a CS (WA Tycos Harvey Elite) by two observers, and heart sounds were recorded digitally using an ES (3M Littmann Stethoscope Model 3200) for off-line analysis. Echocardiography was used as the clinical standard method for validation of auscultatory findings. Additionally, digital recordings (DRs) were assessed by eight independent observers with various levels of expertise, and compared using interclass correlation and Cohen's weighted kappa analyses. Using the CS, a heart murmur (n = 88 cats) or gallop sound (n = 17) was identified in 105 cats, whereas 45 cats lacked abnormal heart sounds. There was good total agreement (83-90%) between the two observers using the CS. In contrast, there was only moderate agreement (P <0.001) between results from the CS and the DRs for murmurs, and poor agreement for gallops. The CS was more sensitive compared with the DRs with regard to murmurs and gallops. Agreement among the eight observers was good-to-excellent for murmur detection (81%). In conclusion, DRs made with the ES are less sensitive but comparably specific to a CS at detecting abnormal heart sounds in cats.

The clinical value of echocardiography and acoustic cardiography to monitor patients undergoing anthracycline chemotherapy.

BACKGROUND: Investigate the usefulness of echocardiography and acoustic cardiography to monitor patients exposed to anthracycline chemotherapy. HYPOTHESIS: Serial echocardiographies to monitor systolic function may not be neccessary in all patients undergoing anthracycline chemotherapy. METHODS: In a prospective study, consecutive patients undergoing anthracycline-containing chemotherapy were evaluated with echocardiography and acoustic cardiography at baseline, after completion of chemotherapy, and after a median follow-up of 3.8 years. Systolic dysfunction was defined as a left ventricular ejection fraction≤50%. RESULTS: A total of 187 patients (83% female) with a mean age of 55±14 years underwent chemotherapy for breast cancer (73%), malignant lymphoma (23%), and sarcoma (4%). None of the patients had systolic dysfunction at baseline. Patients were treated with doxorubicin 276±74 mg/m2 or epirubicin 317±55 mg/m2. After chemotherapy, 170 (91%) had normal systolic function, 8 (4%) developed systolic dysfunction, and 9 (5%) had died. Of those 8 patients with systolic dysfunction, 4 (50%) improved to normal systolic function, 1 (13%) remained unchanged, and 3 (37%) died. Patients with normal systolic function after chemotherapy had a mortality rate of 3.5%, and 1.8% developed late systolic dysfunction. Acoustic cardiography-derived percent electromechanical activation time>12.4% had a sensitivity of 88% and a specificity of 84% to identify patients with systolic dysfunction (area under the receiver operating characteristic curve 0.87). CONCLUSIONS: Patients with systolic dysfunction early after anthracycline treatment had worse outcome. Acoustic cardiography was able to identify these patients with a high sensitivity and specificity. Based on the findings of this study, we propose a simple algorithm to monitor patients undergoing anthracycline-containing chemotherapy.

The use of pneumoperitoneum during laparoscopic surgery as a model to study pathophysiologic phenomena: the correlation of cardiac functionality with computerized acoustic indices--preliminary data.

BACKGROUND: Induction of pneumoperitoneum during laparoscopic surgery leads to diverse cardiovascular changes that can be used as a model to study pathophysiologic phenomena. Application of novel signal processing and figure extraction enabled searching for correlation between various signals and pathophysiologic setting. Our aim was to quantitatively correlate cardiac functionality (as expressed by cardiac output) with the spectral energy of the first heart sound (S1) obtained from the phonocardiogram, during laparoscopic surgery. PATIENTS AND METHODS: Patients who were scheduled for elective laparoscopic operations were enrolled in the study. Cardiac output was maximally changed during anesthesia and abdominal insufflation and was obtained from the arterial pressure wave (FloTrac™ sensor and Vigileo™ monitor [Edwards Lifesciences Ltd.]). Heart signals were recorded during surgery from each subject by a computerized digital data acquisition system. The automatic analysis of the heart sounds included segmentation that was based on the energy envelope of the heart sounds together with analysis of the electrocardiogram signal. We analyzed the morphology of the sounds using hierarchial cluster analysis to remove those sounds that were not reliably recorded. The magnitude of the amplitude of heart sounds was obtained by using the Hilbert transform for each heartbeat. Statistical analysis was based on linear regression. RESULTS: Following exclusion of 3 patients (mainly because of technical reasons), we were left with 7 patients who demonstrated statistically significant positive correlation between cardiac index and the amplitude of S1 (regression coefficient between 0.4 and 0.9, P<.05). Linear regression analysis was done on the normalized values of all 7 patients and was found to be highly significant. CONCLUSIONS: In this study we have demonstrated significant linear correlation between the acoustic amplitude (spectral energy) of S1 and cardiac functionality, through sophisticated computerized analysis, using the pneumoperitoneum model for changing the cardiac output.