A Markov-Switching Model Approach to Heart Sound Segmentation and Classification.

OBJECTIVE: We consider challenges in accurate segmentation of heart sound signals recorded under noisy clinical environments for subsequent classification of pathological events. Existing state-of-the-art solutions to heart sound segmentation use probabilistic models such as hidden Markov models (HMMs), which, however, are limited by its observation independence assumption and rely on pre-extraction of noise-robust features. METHODS: We propose a Markov-switching autoregressive (MSAR) process to model the raw heart sound signals directly, which allows efficient segmentation of the cyclical heart sound states according to the distinct dependence structure in each state. To enhance robustness, we extend the MSAR model to a switching linear dynamic system (SLDS) that jointly model both the switching AR dynamics of underlying heart sound signals and the noise effects. We introduce a novel algorithm via fusion of switching Kalman filter and the duration-dependent Viterbi algorithm, which incorporates the duration of heart sound states to improve state decoding. RESULTS: Evaluated on Physionet/CinC Challenge 2016 dataset, the proposed MSAR-SLDS approach significantly outperforms the hidden semi-Markov model (HSMM) in heart sound segmentation based on raw signals and comparable to a feature-based HSMM. The segmented labels were then used to train Gaussian-mixture HMM classifier for identification of abnormal beats, achieving high average precision of 86.1% on the same dataset including very noisy recordings. CONCLUSION: The proposed approach shows noticeable performance in heart sound segmentation and classification on a large noisy dataset. SIGNIFICANCE: It is potentially useful in developing automated heart monitoring systems for pre-screening of heart pathologies.

A Novel and Cost-Effective Method for Evaluating Cardiopulmonary Auscultation Skills in Student Physical Therapists.

Sophisticated high-fidelity human simulation (HFHS) manikins allow for practice of both evaluation and treatment techniques in a controlled environment in which real patients are not put at risk. However, due to high demand, access to HFHS by students has been very competitive and limited. In the present study, a basic CPR manikin with a speaker implanted in the chest cavity and internet access to a variety of heart and breath sounds was used. Students were evaluated on their ability to locate and identify auscultation sites and heart/breath sounds. A five-point Likert scale survey was administered to gain insight into student perceptions on the use of this simulation method. Our results demonstrated that 95% of students successfully identified the heart and breath sounds. Furthermore, survey results indicated that 75% of students agreed or strongly agreed that this manner of evaluation was an effective way to assess their auscultation skills. Based on performance and perception, we conclude that a simulation method as described in this paper is a viable and cost-effective means of evaluating auscultation competency in not only student physical therapists but across other health professions as well.

Continuous cardiotocography (CTG) as a form of electronic fetal monitoring (EFM) for fetal assessment during labour.

BACKGROUND: Cardiotocography (CTG) records changes in the fetal heart rate and their temporal relationship to uterine contractions. The aim is to identify babies who may be short of oxygen (hypoxic) to guide additional assessments of fetal wellbeing, or determine if the baby needs to be delivered by caesarean section or instrumental vaginal birth. This is an update of a review previously published in 2013, 2006 and 2001. OBJECTIVES: To evaluate the effectiveness and safety of continuous cardiotocography when used as a method to monitor fetal wellbeing during labour. SEARCH METHODS: We searched the Cochrane Pregnancy and Childbirth Group Trials Register (30 November 2016) and reference lists of retrieved studies. SELECTION CRITERIA: Randomised and quasi-randomised controlled trials involving a comparison of continuous cardiotocography (with and without fetal blood sampling) with no fetal monitoring, intermittent auscultation intermittent cardiotocography. DATA COLLECTION AND ANALYSIS: Two review authors independently assessed study eligibility, quality and extracted data from included studies. Data were checked for accuracy. MAIN RESULTS: We included 13 trials involving over 37,000 women. No new studies were included in this update.One trial (4044 women) compared continuous CTG with intermittent CTG, all other trials compared continuous CTG with intermittent auscultation. No data were found comparing no fetal monitoring with continuous CTG. Overall, methodological quality was mixed. All included studies were at high risk of performance bias, unclear or high risk of detection bias, and unclear risk of reporting bias. Only two trials were assessed at high methodological quality.Compared with intermittent auscultation, continuous cardiotocography showed no significant improvement in overall perinatal death rate (risk ratio (RR) 0.86, 95% confidence interval (CI) 0.59 to 1.23, N = 33,513, 11 trials, low quality evidence), but was associated with halving neonatal seizure rates (RR 0.50, 95% CI 0.31 to 0.80, N = 32,386, 9 trials, moderate quality evidence). There was no difference in cerebral palsy rates (RR 1.75, 95% CI 0.84 to 3.63, N = 13,252, 2 trials, low quality evidence). There was an increase in caesarean sections associated with continuous CTG (RR 1.63, 95% CI 1.29 to 2.07, N = 18,861, 11 trials, low quality evidence). Women were also more likely to have instrumental vaginal births (RR 1.15, 95% CI 1.01 to 1.33, N = 18,615, 10 trials, low quality evidence). There was no difference in the incidence of cord blood acidosis (RR 0.92, 95% CI 0.27 to 3.11, N = 2494, 2 trials, very low quality evidence) or use of any pharmacological analgesia (RR 0.98, 95% CI 0.88 to 1.09, N = 1677, 3 trials, low quality evidence).Compared with intermittent CTG, continuous CTG made no difference to caesarean section rates (RR 1.29, 95% CI 0.84 to 1.97, N = 4044, 1 trial) or instrumental births (RR 1.16, 95% CI 0.92 to 1.46, N = 4044, 1 trial). Less cord blood acidosis was observed in women who had intermittent CTG, however, this result could have been due to chance (RR 1.43, 95% CI 0.95 to 2.14, N = 4044, 1 trial).Data for low risk, high risk, preterm pregnancy and high-quality trials subgroups were consistent with overall results. Access to fetal blood sampling did not appear to influence differences in neonatal seizures or other outcomes.Evidence was assessed using GRADE. Most outcomes were graded as low quality evidence (rates of perinatal death, cerebral palsy, caesarean section, instrumental vaginal births, and any pharmacological analgesia), and downgraded for limitations in design, inconsistency and imprecision of results. The remaining outcomes were downgraded to moderate quality (neonatal seizures) and very low quality (cord blood acidosis) due to similar concerns over limitations in design, inconsistency and imprecision. AUTHORS' CONCLUSIONS: CTG during labour is associated with reduced rates of neonatal seizures, but no clear differences in cerebral palsy, infant mortality or other standard measures of neonatal wellbeing. However, continuous CTG was associated with an increase in caesarean sections and instrumental vaginal births. The challenge is how best to convey these results to women to enable them to make an informed decision without compromising the normality of labour.The question remains as to whether future randomised trials should measure efficacy (the intrinsic value of continuous CTG in trying to prevent adverse neonatal outcomes under optimal clinical conditions) or effectiveness (the effect of this technique in routine clinical practice).Along with the need for further investigations into long-term effects of operative births for women and babies, much remains to be learned about the causation and possible links between antenatal or intrapartum events, neonatal seizures and long-term neurodevelopmental outcomes, whilst considering changes in clinical practice over the intervening years (one-to-one-support during labour, caesarean section rates). The large number of babies randomised to the trials in this review have now reached adulthood and could potentially provide a unique opportunity to clarify if a reduction in neonatal seizures is something inconsequential that should not greatly influence women's and clinicians' choices, or if seizure reduction leads to long-term benefits for babies. Defining meaningful neurological and behavioural outcomes that could be measured in large cohorts of young adults poses huge challenges. However, it is important to collect data from these women and babies while medical records still exist, where possible describe women's mobility and positions during labour and birth, and clarify if these might impact on outcomes. Research should also address the possible contribution of the supine position to adverse outcomes for babies, and assess whether the use of mobility and positions can further reduce the low incidence of neonatal seizures and improve psychological outcomes for women.

Cardiotocography versus intermittent auscultation of fetal heart on admission to labour ward for assessment of fetal wellbeing.

BACKGROUND: The admission cardiotocograph (CTG) is a commonly used screening test consisting of a short (usually 20 minutes) recording of the fetal heart rate (FHR) and uterine activity performed on the mother's admission to the labour ward. This is an update of a review published in 2012. OBJECTIVES: To compare the effects of admission cardiotocography with intermittent auscultation of the FHR on maternal and infant outcomes for pregnant women without risk factors on their admission to the labour ward. SEARCH METHODS: We searched the Cochrane Pregnancy and Childbirth Group's Trials Register to 30 November 2016 and we planned to review the reference list of retrieved papers SELECTION CRITERIA: All randomised and quasi-randomised trials comparing admission CTG with intermittent auscultation of the FHR for pregnant women between 37 and 42 completed weeks of pregnancy and considered to be at low risk of intrapartum fetal hypoxia and of developing complications during labour. DATA COLLECTION AND ANALYSIS: Two authors independently assessed trial eligibility and quality, and extracted data. Data were checked for accuracy. MAIN RESULTS: We included no new trials in this update. We included four trials involving more than 13,000 women which were conducted in the UK and Ireland and included women in labour. Three trials were funded by the hospitals where the trials took place and one trial was funded by the Scottish government. No declarations of interest were made in two trials; the remaining two trials did not mention declarations of interest. Overall, the studies were assessed as low risk of bias. Results reported in the 2012 review remain unchanged.Although not statistically significant using a strict P < 0.05 criterion, data were consistent with women allocated to admission CTG having, on average, a higher probability of an increase in incidence of caesarean section than women allocated to intermittent auscultation (risk ratio (RR) 1.20, 95% confidence interval (CI) 1.00 to 1.44, 4 trials, 11,338 women, I² = 0%, moderate quality evidence). There was no clear difference in the average treatment effect across included trials between women allocated to admission CTG and women allocated to intermittent auscultation in instrumental vaginal birth (RR 1.10, 95% CI 0.95 to 1.27, 4 trials, 11,338 women, I² = 38%, low quality evidence) and perinatal mortality rate (RR 1.01, 95% CI 0.30 to 3.47, 4 trials, 11,339 infants, I² = 0%, moderate quality evidence).Women allocated to admission CTG had, on average, higher rates of continuous electronic fetal monitoring during labour (RR 1.30, 95% CI 1.14 to 1.48, 3 trials, 10,753 women, I² = 79%, low quality evidence) and fetal blood sampling (RR 1.28, 95% CI 1.13 to 1.45, 3 trials, 10,757 women, I² = 0%) than women allocated to intermittent auscultation. There were no differences between groups in other secondary outcome measures including incidence and severity of hypoxic ischaemic encephalopathy (incidence only reported) (RR 1.19, 95% CI 0.37 to 3.90; 2367 infants; 1 trial; very low quality evidence) and incidence of seizures in the neonatal period (RR 0.72, 95% CI 0.32 to 1.61; 8056 infants; 1 trial; low quality evidence). There were no data reported for severe neurodevelopmental disability assessed at greater than, or equal to, 12 months of age. AUTHORS' CONCLUSIONS: Contrary to continued use in some clinical areas, we found no evidence of benefit for the use of the admission CTG for low-risk women on admission in labour.Furthermore, the probability is that admission CTG increases the caesarean section rate by approximately 20%. The data lacked power to detect possible important differences in perinatal mortality. However, it is unlikely that any trial, or meta-analysis, will be adequately powered to detect such differences. The findings of this review support recommendations that the admission CTG not be used for women who are low risk on admission in labour. Women should be informed that admission CTG is likely associated with an increase in the incidence of caesarean section without evidence of benefit.Evidence quality ranged from moderate to very low, with downgrading decisions based on imprecision, inconsistency and a lack of blinding for participants and personnel. All four included trials were conducted in developed Western European countries. One additional study is ongoing.The usefulness of the findings of this review for developing countries will depend on FHR monitoring practices. However, an absence of benefit and likely harm associated with admission CTG will have relevance for countries where questions are being asked about the role of the admission CTG.Future studies evaluating the effects of the admission CTG should consider including women admitted with signs of labour and before a formal diagnosis of labour. This would include a cohort of women currently having admission CTGs and not included in current trials.

Prognostic value of acoustic cardiography in patients with chronic heart failure.

BACKGROUND: Rapid risk stratification in patients with heart failure is critically important but challenging. The aim of our study is to ascertain whether acoustic cardiography can identify heart failure (HF) patients at high risk for mortality. METHODS: A total of 474 HF patients were enrolled into our study (76±11years old). Acoustic cardiographic parameters included S3 score (ie, third heart sound exists) and systolic dysfunction index (SDI) (correlated closely with left ventricular systolic dysfunction). The event-free survival curves were plotted by Kaplan-Meier method. Cox regression analysis was used to identify independent predictors for all-cause mortality. RESULTS: During a mean follow-up of 484days, 169 (35.7%) patients died and 126 (26.6%) were due to cardiac causes. After controlling for age, systolic blood pressure, hemoglobin, blood urea nitrogen, albumin, as well as ACEI and beta-blocker treatment in multivariate Cox regression analysis, SDI ≥5 and S3 score ≥4 were both independent predictors for all-cause mortality. Kaplan-Meier analysis showed that HF patients with SDI ≥5 or S3 score ≥4 had a significantly lower survival (52.2% vs. 69.2%, Log-rank χ(2)=18.07, P<0.001; 56.8% vs. 68.6%, Log-rank χ(2)=10.58, P=0.001, respectively) than those with lower SDI or S3 score. CONCLUSIONS: Acoustic cardiography could serve as a cost-effective and time-efficient tool to identify HF patients at high risk for mortality who might benefit from aggressive monitoring and intervention. It may improve assessment and initial disposition decisions in HF management.

Why should you model time when you use Markov models for heart sound analysis.

Auscultation is a widely used technique in clinical activity to diagnose heart diseases. However, heart sounds are difficult to interpret because a) of events with very short temporal onset between them (tens of milliseconds) and b) dominant frequencies that are out of the human audible spectrum. In this paper, we propose a model to segment heart sounds using a semi-hidden Markov model instead of a hidden Markov model. Our model in difference from the state-of-the-art hidden Markov models takes in account the temporal constraints that exist in heart cycles. We experimentally confirm that semi-hidden Markov models are able to recreate the "true" continuous state sequence more accurately than hidden Markov models. We achieved a mean error rate per sample of 0.23.

Pediatric heart sound segmentation using hidden Markov model.

Recent advances in technology have enabled automatic cardiac auscultation using digital stethoscopes. This in turn creates the need for development of algorithms capable of automatic segmentation of heart sounds. Pediatric heart sound segmentation is a challenging task due to various confounding factors including the significant influence of respiration on children's heart sounds. The current work investigates the application of homomorphic filtering and Hidden Markov Model for the purpose of segmenting pediatric heart sounds. The efficacy of the proposed method is evaluated on the publicly available Pascal Challenge dataset and its performance is compared with those of three other existing methods. The results show that our proposed method achieves an accuracy of 92.4%±1.1% and 93.5%±1.1% in identifying the first and second heart sound components, respectively, and is superior to three other existing methods in terms of accuracy or computational complexity.

Continuous cardiotocography (CTG) as a form of electronic fetal monitoring (EFM) for fetal assessment during labour.

BACKGROUND: Cardiotocography (known also as electronic fetal monitoring), records changes in the fetal heart rate and their temporal relationship to uterine contractions. The aim is to identify babies who may be short of oxygen (hypoxic), so additional assessments of fetal well-being may be used, or the baby delivered by caesarean section or instrumental vaginal birth. OBJECTIVES: To evaluate the effectiveness of continuous cardiotocography during labour. SEARCH METHODS: We searched the Cochrane Pregnancy and Childbirth Group Trials Register (31 December 2012) and reference lists of retrieved studies. SELECTION CRITERIA: Randomised and quasi-randomised controlled trials involving a comparison of continuous cardiotocography (with and without fetal blood sampling) with (a) no fetal monitoring, (b) intermittent auscultation (c) intermittent cardiotocography. DATA COLLECTION AND ANALYSIS: Two review authors independently assessed study eligibility, quality and extracted data from included studies. MAIN RESULTS: Thirteen trials were included with over 37,000 women; only two were judged to be of high quality.Compared with intermittent auscultation, continuous cardiotocography showed no significant improvement in overall perinatal death rate (risk ratio (RR) 0.86, 95% confidence interval (CI) 0.59 to 1.23, n = 33,513, 11 trials), but was associated with a halving of neonatal seizures (RR 0.50, 95% CI 0.31 to 0.80, n = 32,386, nine trials). There was no significant difference in cerebral palsy rates (RR 1.75, 95% CI 0.84 to 3.63, n = 13,252, two trials). There was a significant increase in caesarean sections associated with continuous cardiotocography (RR 1.63, 95% CI 1.29 to 2.07, n = 18,861, 11 trials). Women were also more likely to have an instrumental vaginal birth (RR 1.15, 95% CI 1.01 to 1.33, n = 18,615, 10 trials).Data for subgroups of low-risk, high-risk, preterm pregnancies and high-quality trials were consistent with overall results. Access to fetal blood sampling did not appear to influence the difference in neonatal seizures nor any other prespecified outcome. AUTHORS' CONCLUSIONS: Continuous cardiotocography during labour is associated with a reduction in neonatal seizures, but no significant differences in cerebral palsy, infant mortality or other standard measures of neonatal well-being. However, continuous cardiotocography was associated with an increase in caesarean sections and instrumental vaginal births. The challenge is how best to convey these results to women to enable them to make an informed choice without compromising the normality of labour.

Cardiotocography versus intermittent auscultation of fetal heart on admission to labour ward for assessment of fetal wellbeing.

BACKGROUND: The admission cardiotocograph (CTG) is a commonly used screening test consisting of a short (usually 20 minutes) recording of the fetal heart rate (FHR) and uterine activity performed on the mother's admission to the labour ward. OBJECTIVES: To compare the effects of admission CTG with intermittent auscultation of the FHR on maternal and infant outcomes for pregnant women without risk factors on their admission to the labour ward. SEARCH METHODS: We searched the Cochrane Pregnancy and Childbirth Group's Trials Register (17 May 2011) (CENTRAL) (The Cochrane Library 2011 Issue 2 of 4), MEDLINE (1966 to 17 May 2011), CINAHL (1982 to 17 May 2011), Dissertation Abstracts (1980 to 17 May 2011) and the reference list of retrieved papers. SELECTION CRITERIA: All randomised and quasi-randomised trials comparing admission CTG with intermittent auscultation of the FHR for pregnant women between 37 and 42 completed weeks of pregnancy and considered to be at low risk of intrapartum fetal hypoxia and of developing complications during labour. DATA COLLECTION AND ANALYSIS: Two authors independently assessed trial eligibility and quality, and extracted data. Data were checked for accuracy. MAIN RESULTS: We included four trials involving more than 13,000 women. All four studies included women in labour. Overall, the studies were at low risk of bias. Although not statistically significant using a strict P < 0.05 criterion, data are consistent with women allocated to admission CTG having, on average, a higher probability of an increase in incidence of caesarean section than women allocated to intermittent auscultation (risk ratio (RR) 1.20, 95% confidence interval (CI) 1.00 to 1.44, four trials, 11,338 women, T² = 0.00, I² = 0%). There was no significant difference in the average treatment effect across included trials between women allocated to admission CTG and women allocated to intermittent auscultation in instrumental vaginal birth (RR 1.10, 95% CI 0.95 to 1.27, four trials, 11,338 women, T² = 0.01, I² = 38%) and fetal and neonatal deaths (RR 1.01, 95% CI 0.30 to 3.47, four trials, 11339 infants, T² = 0.00, I² = 0%).Women allocated to admission CTG had, on average, significantly higher rates of continuous electronic fetal monitoring during labour (RR 1.30, 95% CI 1.14 to 1.48, three trials, 10,753 women, T² = 0.01, I² = 79%) and fetal blood sampling (RR 1.28, 95% CI 1.13 to 1.45, three trials, 10,757 women, T² = 0.00, I² = 0%) than women allocated to intermittent auscultation. There were no differences between groups in other secondary outcome measures. AUTHORS' CONCLUSIONS: Contrary to continued use in some clinical areas, we found no evidence of benefit for the use of the admission cardiotocograph (CTG) for low-risk women on admission in labour.We found no evidence of benefit for the use of the admission CTG for low-risk women on admission in labour. Furthermore, the probability is that admission CTG increases the caesarean section rate by approximately 20%. The data lacked power to detect possible important differences in perinatal mortality. However, it is unlikely that any trial, or meta-analysis, will be adequately powered to detect such differences. The findings of this review support recommendations that the admission CTG not be used for women who are low risk on admission in labour. Women should be informed that admission CTG is likely associated with an increase in the incidence of caesarean section without evidence of benefit.

Estimación auscultatoria de la presiónsistólica de arteria pulmonar: ¿Es factible?. Correlación con determinación ecocardiográfica / Heart auscultatory assessment of pulmonary artery systolic pressure

The clinical assessment of pulmonary artery systolic pressure (PASP) by means of heart auscultation may be comparable to the measures obtained by Doppler echocardiography. Aim: To compare PASP estimated by heart auscultation and echocardiography. Material and Methods: Thirty consecutive patients aged 70 ± 16 years (68 percent women) were evaluated prospectively, all of whom had an echocardiogram requested by their attending physician. Echocardiographic evaluation of PASP was made by tricuspid regurgitation velocity plus right a trial pressure estimate. Two trained clinicians, blinded for the clinical history and rest of physical examination, auscultated the patients. PASP was estimated from the auscultatory intensity of the pulmonary component in comparison to the aortic component of the second heart sound and its propagation towards the apex, in accordance to a pre-established algorithm. Correlation between auscultatory and echocardiographic measures of PASP was made by Pearson test. Variability between both methods and among observers was evaluated with Bland-Altman analysis. Results: Fifty two per cent of patients were hypertensive and 20 percent diabetic. Admission diagnoses were heart failure in 50 percent of cases, exacerbation of chronic obstructive pulmonary disease in 20 percent, pulmonary thromboembolism in 10 percent and other clinical entities in 20 percent. A significant correlation was found between auscultatory and echocardiographic estimation of PASP (r = 0.64, p = 0, 01). Bland-Altman analysis showed a mean difference between both determinations of 7.6 ± 7.6 mmHg. Bland-Altman analysis between both operators showed an average difference of 5.4 ± 8.4 mm Hg. Conclusions: Heart auscultatory evaluation allows a precise and reproducible estimation of PASP and compares favorably with echocardiographic assessment.

Segmentation of heart sound recordings by a duration-dependent hidden Markov model.

Digital stethoscopes offer new opportunities for computerized analysis of heart sounds. Segmentation of heart sound recordings into periods related to the first and second heart sound (S1 and S2) is fundamental in the analysis process. However, segmentation of heart sounds recorded with handheld stethoscopes in clinical environments is often complicated by background noise. A duration-dependent hidden Markov model (DHMM) is proposed for robust segmentation of heart sounds. The DHMM identifies the most likely sequence of physiological heart sounds, based on duration of the events, the amplitude of the signal envelope and a predefined model structure. The DHMM model was developed and tested with heart sounds recorded bedside with a commercially available handheld stethoscope from a population of patients referred for coronary arterioangiography. The DHMM identified 890 S1 and S2 sounds out of 901 which corresponds to 98.8% (CI: 97.8-99.3%) sensitivity in 73 test patients and 13 misplaced sounds out of 903 identified sounds which corresponds to 98.6% (CI: 97.6-99.1%) positive predictivity. These results indicate that the DHMM is an appropriate model of the heart cycle and suitable for segmentation of clinically recorded heart sounds.

[Heart auscultatory assessment of pulmonary artery systolic pressure]. / Estimación auscultatoria de la presiónsistólica de arteria pulmonar: ¿Es factible?. Correlación con determinación ecocardiográfica.

BACKGROUND: The clinical assessment of pulmonary artery systolic pressure (PASP) by means of heart auscultation may be comparable to the measures obtained by Doppler echocardiography. AIM: To compare PASP estimated by heart auscultation and echocardiography. MATERIAL AND METHODS: Thirty consecutive patients aged 70 ± 16 years (68% women) were evaluated prospectively, all of whom had an echocardiogram requested by their attending physician. Echocardiographic evaluation of PASP was made by tricuspid regurgitation velocity plus right a trial pressure estimate. Two trained clinicians, blinded for the clinical history and rest of physical examination, auscultated the patients. PASP was estimated from the auscultatory intensity of the pulmonary component in comparison to the aortic component of the second heart sound and its propagation towards the apex, in accordance to a pre-established algorithm. Correlation between auscultatory and echocardiographic measures of PASP was made by Pearson test. Variability between both methods and among observers was evaluated with Bland-Altman analysis. RESULTS: Fifty two per cent of patients were hypertensive and 20% diabetic. Admission diagnoses were heart failure in 50% of cases, exacerbation of chronic obstructive pulmonary disease in 20%, pulmonary thromboembolism in 10% and other clinical entities in 20%. A significant correlation was found between auscultatory and echocardiographic estimation of PASP (r = 0.64, p = 0, 01). Bland-Altman analysis showed a mean difference between both determinations of 7.6 ± 7.6 mmHg. Bland-Altman analysis between both operators showed an average difference of 5.4 ± 8.4 mm Hg. CONCLUSIONS: Heart auscultatory evaluation allows a precise and reproducible estimation of PASP and compares favorably with echocardiographic assessment.

Avaliação de um modelo de parâmetros distribuídos aplicado à estimação da geometria arterial na hipertensão / Evaluation of a distributed parameter model applied to arterial geometry estimation in hypertension

A hipertensão arterial provoca adaptações estruturais nas artérias, principalmente pelos processos de hipertrofia e remodelagem, as quais antecedem lesões de órgãos-alvo. A determinação de variáveis mecânicas e geométricas associadas ao sistema arterial possibilita ao clínico identificar precocemente as adaptações que decorrem da hipertensão arterial sistêmica no paciente, permitindo a intervenção terapêutica mais adequada. Este trabalho apresenta a avaliação de um modelo eletro-hidráulico e seu método associado para a determinaçãodos parâmetros geométricos do segmento arterial do antebraço. O método proposto requer somente a aquisição não-invasiva de ondas de pulso em dois sítios distintos. Séries de ondas de pulso da artéria radial foram simuladas a partir de ondas de pulso reais da artéria braquial, empregandoum modelo de parâmetros distribuídos simplificado das artérias do antebraço. O modelo é composto por três seções,representando os segmentos arteriais braquial, radial e a mão. As artérias braquial e radial foram representadas por componentes resistivos (atrito local), indutivos (massa do sangue) e capacitivos (complacência arterial), enquanto a mão foi representada por elementos resistivos (resistências de pequenos vasos da mão e periféricos) e capacitivos (complacência de pequenos vasos). Os resultados mostram um erro médio de estimação que pode ser considerado pequeno (3,7%) quando comparado aos valores de adaptação arterial in vivo (alterações de até 15%), indicando a utilização deste procedimento para estimar o processo de remodelagem das artérias de médio calibre observado na hipertensão arterial sistêmica.

Arterial hypertension leads to structural adaptation of arteries, mainly hypertrophy or remodeling, which precedes target-organ injuries. Determination of both mechanical and geometrical variables related to arterial system allows physicians to identify early arterial adaptation derived from systemic hypertension and to propose therapeutics. This work presents the evaluation of an electric-hydraulic model, and associated method, for determination of geometrical and mechanical parameters of forearm arteries. The proposed method requires only noninvasive acquisition of two pressure pulses at distinct sites. Series of pressure pulses from radial artery were simulated using acquired brachial artery pulses and a simplified distributed-model of the forearm arteries. The model presents three sections, representing brachial, radial, and hand vasculature. Brachial and radial arteries were represented with resistive (friction), inductive (blood mass), and capacitive (arterial compliance) elements. The hand was modeled with resistive (small vessels and capillaries) and capacitive elements (small vessels compliance). The results show that an average estimation error of 3.7% is small compared to “in vivo” findings (changes up to 15%), indicatingthat the procedure can be used to assess the remodeling of medium-sized arteries on primary systemic arterial hypertension.

A computer-aided MFCC-based HMM system for automatic auscultation.

Auscultation, the act of listening to the sounds of internal organs, is a valuable medical diagnostic tool. Auscultation methods provide the information about a vast variety of internal body sounds originated by various organs such as heart, lungs, bowel, vascular disorders, etc. In this study, a cardiac sound registration system has been designed incorporating functions such as heart signals segmentation, classification and characterization for automated identification and ease of interpretation by the users. Considering a synergy with the domain of speech analysis, the authors introduced Mel-frequency cepstral coefficient (MFCC) to extract representative features and develop hidden Markov model (HMM) for signal classification. This system was applied to 1381 data sets of real and simulated, normal and abnormal domains. Classification rates for normal and abnormal heart sounds were found to be 95.7% for continuous murmurs, 96.25% for systolic murmurs and 90% for diastolic murmurs by a probabilistic comparison approach. This implies a high potential for the system as a diagnostic aid for primary health-care sectors.

Continuous cardiotocography (CTG) as a form of electronic fetal monitoring (EFM) for fetal assessment during labour.

BACKGROUND: Cardiotocography (sometimes known as electronic fetal monitoring), records changes in the fetal heart rate and their temporal relationship to uterine contractions. The aim is to identify babies who may be short of oxygen (hypoxic), so additional assessments of fetal well-being may be used, or the baby delivered by caesarean section or instrumental vaginal birth. OBJECTIVES: To evaluate the effectiveness of continuous cardiotocography during labour. SEARCH STRATEGY: We searched the Cochrane Pregnancy and Childbirth Group Trials Register (March 2006), CENTRAL (The Cochrane Library 2005, Issue 4), MEDLINE (1966 to December 2005), EMBASE (1974 to December 2005), Dissertation Abstracts (1980 to December 2005) and the National Research Register (December 2005). SELECTION CRITERIA: Randomised and quasi-randomised controlled trials involving a comparison of continuous cardiotocography (with and without fetal blood sampling) with (a) no fetal monitoring, (b) intermittent auscultation (c) intermittent cardiotocography. DATA COLLECTION AND ANALYSIS: Two authors independently assessed eligibility, quality and extracted data. MAIN RESULTS: Twelve trials were included (over 37,000 women); only two were high quality. Compared to intermittent auscultation, continuous cardiotocography showed no significant difference in overall perinatal death rate (relative risk (RR) 0.85, 95% confidence interval (CI) 0.59 to 1.23, n = 33,513, 11 trials), but was associated with a halving of neonatal seizures (RR 0.50, 95% CI 0.31 to 0.80, n = 32,386, nine trials) although no significant difference was detected in cerebral palsy (RR 1.74, 95% CI 0.97 to 3.11, n = 13,252, two trials). There was a significant increase in caesarean sections associated with continuous cardiotocography (RR 1.66, 95% CI 1.30 to 2.13, n =18,761, 10 trials). Women were also more likely to have an instrumental vaginal birth (RR 1.16, 95% CI 1.01 to 1.32, n = 18,151, nine trials). Data for subgroups of low-risk, high-risk, preterm pregnancies and high quality trials were consistent with overall results. Access to fetal blood sampling did not appear to influence the difference in neonatal seizures nor any other prespecified outcome. AUTHORS' CONCLUSIONS: Continuous cardiotocography during labour is associated with a reduction in neonatal seizures, but no significant differences in cerebral palsy, infant mortality or other standard measures of neonatal well-being. However, continuous cardiotocography was associated with an increase in caesarean sections and instrumental vaginal births. The real challenge is how best to convey this uncertainty to women to enable them to make an informed choice without compromising the normality of labour.

[Is transmission of heart murmurs via e-mail cost saving?]. / Er overføring av hjertebilyder via e-post kostnadsbesparende?

BACKGROUND: The use of pre-recorded heart murmur in an electronic referral for a remote consultation can save children and their parents from having to travel to the nearest out-patient clinic. The heart sound can be recorded by the GP at the local health clinic and sent by e-mail to the specialist. 41 clinics in the North Norway healt region have invested in equipment that makes pre-recorded sound referrals possible. This study analyses whether this investment is a cost-saving technology or not. METHODS: A yearly average of 50 children with a heart murmur are referred to a specialist in Troms. The costs of using pre-recorded telemedicine were compared to the costs of patient travelling to the nearest secondary care centre. RESULTS: Pre-recorded heart sound referrals cost from 216 000 NOK more per year than the alternative of bringing patients to the out-patient clinic. The number of children with a heart murmur needed in order to break even must exceed 195 per year, i.e. 1.7 children per GP per year. INTERPRETATION: The number of children with a heart murmur in Troms is too low for this method to be a cost-saving approach.

Heart murmurs recorded by a sensor based electronic stethoscope and e-mailed for remote assessment.

BACKGROUND: Heart murmurs are common in children, and they are often referred to a specialist for examination. A clinically innocent murmur does not need further investigation. The referral area of the University Hospital is large and sparsely populated. A new service for remote auscultation (telemedicine) of heart murmurs in children was established where heart sounds and short texts were sent as an attachment to e-mails. AIM: To assess the clinical quality of this method. METHODS: Heart sounds from 47 patients with no murmur (n = 7), with innocent murmurs (n = 20), or with pathological murmurs (n = 20) were recorded using a sensor based stethoscope and e-mailed to a remote computer. The sounds were repeated, giving 100 cases that were randomly distributed on a compact disc. Four cardiologists assessed and categorised the cases as having "no murmur", "innocent murmur", or "pathological murmur", recorded the assessment time per case, their degree of certainty, and whether they recommended referral. RESULTS: On average, 2.1 minutes were spent on each case. The mean sensitivity and specificity were 89.7% and 98.2% respectively, and the inter-observer and intra-observer variabilities were low (kappa 0.81 and 0.87), respectively. A total of 93.4% of cases with a pathological murmur and 12.6% of cases with an innocent murmur were recommended for referral. CONCLUSION: Telemedical referral of patients with heart murmurs for remote assessment by a cardiologist is safe and saves time. Skilled auscultation is adequate to detect patients with innocent murmurs.