Showing papers by "Manuel J. Antunes published in 2007"

Allograft aortic root replacement in complex prosthetic endocarditis

Abstract: Objective: To evaluate perioperative and long-term results of complex prosthetic valve endocarditis treated by allograft aortic root replacement. Methods: From April 1988 through February 2006, 41 patients diagnosed as prosthetic valve endocarditis (PVE) complicated by root abscess and/or periprosthetic leak, underwent fresh allograft valve replacement by root replacement. There were 37 males (89.7%) and the mean age was 51.5 13.7 years. The NYHA functional class was 3.0 0.1. Thirty-seven patients (90%) had a mechanical prosthesis and in 10 (25.6%) the PVE was recent (<3 months). Ten patients (24.4%) underwent emergency valve replacement and four (9.8%) presented with chronic renal failure. The patients were followed for a mean of 54.3 (2—166) months and the end-points were death of the patient or allograft failure. Results: There were two hospital deaths (4.8%), both in patients with perioperative low cardiac output. Nine patients had transient acute renal failure (22.0%) but none required dialysis. Three patients (7.3%) needed pacemaker for complete A—V block. Eight patients (19.5%) died late; two died of cardiac reasons, four of non-cardiac reasons (stroke-one; acute colecystitis-two; traffic accident-two) and two of unknown cause. Two patients needed reoperation due to allograft failure at 61 and 82 months. In no case was there evidence of recurrence of endocarditis during the follow-up.The10-yearsurvivalwas79%.Conclusions:Allograftaorticrootreplacementinprostheticendocarditiscomplicatedbyabscessand/or periprosthetic leakage carries low morbidity and mortality and, in this series, no recurrence of infection. In our experience, these results are superior to those obtained with other valvular substitutes. # 2007 European Association for Cardio-Thoracic Surgery. Published by Elsevier B.V. All rights reserved.

Third Heart Sound Detection Using Wavelet Transform-Simplicity Filter

Abstract: Heart failure and heart valvar diseases are chronic heart disorders which are potentially diagnosed using heart sound characteristics. Heart sound components S1 and S2 exhibit significant characteristics for valvar dysfunction while pathological S3 sound is a prominent sign for heart failure in elderly people. In this paper, a new automatic detection method of the S3 heart sound is proposed. The method is build upon wavelet transform-simplicity filter which separates S1, S2 and S3 sounds from background noise enabling heart sound segmentation even in the presence of heart murmurs or noise sources. The algorithm uses physiologically inspired criteria to assess the presence of S3 heart sound components and to perform their segmentation. Heart sound samples recorded from children as well as from elderly patients with heart failure were used to test the method. The achieved sensitivity and specificity were 90.35% and 92.35%, respectively.

Acute mitral regurgitation due to ruptured ePTFE neo-chordae.

Abstract: Chordal replacement with expanded polytetrafluoroethylene (ePTFE) sutures has proven to be a simple, versatile, and durable technique for the treatment of prolapsed cusps causing mitral valve regurgitation. ePTFE is known for its strong resistance to tension, and is judged to be unbreakable under physiological conditions. Herein are reported two cases of rupture of synthetic chordae tendineae; the possible causes of this extremely rare finding are analyzed.

Work in progress report - Cardiac general Mortality risk prediction in coronary surgery: a locally developed model outperforms external risk models

Abstract: This study aimed at assessing the performance of three external risk-adjusted models – logistic EuroSCORE, Parsonnet score and Ontario Province Risk (OPR) score – in predicting in-hospital mortality in patients submitted to coronary artery bypass graft (CABG) and to develop a local risk-score model. Data on 4567 patients who underwent isolated CABG (1992–2001) were extracted from our clinical database. Hospital mortality was 0.96% (44 patients). For the three external systems, observed and predicted mortalities were compared, and discrimination and calibration were assessed. A local risk model was developed and validated by means of logistic regression and bootstrap analysis. The EuroSCORE predicted a mortality of 2.34% (P-0.001 vs. observed), the Parsonnet 4.43% (P-0.0001) and the OPR 1.66% (P-0.005). All models overestimated mortality significantly in almost all tertile risk groups. The areas under the ROC curve (AUC) for EuroSCORE, Parsonnet and OPR were 0.754, 0.664 and 0.683, respectively. The local model exhibited good calibration and discrimination AUC, 0.752. In conclusion, the three risk-score systems analyzed do not accurately predict in-hospital mortality in our coronary surgery patients; hence their use for risk prediction may not be appropriate in our population. We developed a risk-prediction model that can be used as an instrument to provide accurate information about the risk of in-hospital mortality in our patient population. 2007 Published by European Association for Cardio-Thoracic Surgery. All rights reserved.

Mortality risk prediction in coronary surgery: a locally developed model outperforms external risk models.

Abstract: This study aimed at assessing the performance of three external risk-adjusted models - logistic EuroSCORE, Parsonnet score and Ontario Province Risk (OPR) score - in predicting in-hospital mortality in patients submitted to coronary artery bypass graft (CABG) and to develop a local risk-score model. Data on 4567 patients who underwent isolated CABG (1992-2001) were extracted from our clinical database. Hospital mortality was 0.96% (44 patients). For the three external systems, observed and predicted mortalities were compared, and discrimination and calibration were assessed. A local risk model was developed and validated by means of logistic regression and bootstrap analysis. The EuroSCORE predicted a mortality of 2.34% (P<0.001 vs. observed), the Parsonnet 4.43% (P<0.0001) and the OPR 1.66% (P<0.005). All models overestimated mortality significantly in almost all tertile risk groups. The areas under the ROC curve (AUC) for EuroSCORE, Parsonnet and OPR were 0.754, 0.664 and 0.683, respectively. The local model exhibited good calibration and discrimination AUC, 0.752. In conclusion, the three risk-score systems analyzed do not accurately predict in-hospital mortality in our coronary surgery patients; hence their use for risk prediction may not be appropriate in our population. We developed a risk-prediction model that can be used as an instrument to provide accurate information about the risk of in-hospital mortality in our patient population.

Choosing real-time predictors for ventricular arrhythmia detection

Abstract: The risk of developing life-threatening ventricular arrhythmias in patients with structural heart disease is higher with increased occurrence of premature ventricular complex (PVC). Therefore, reliable detection of these arrhythmias is a challenge for a cardiovascular diagnosis system. While early diagnosis is critical, the task of its automatic detection and classification becomes crucial. Therefore, the underlying models should be efficient, albeit ensuring robustness. Although neural networks (NN) have proven successful in this setting, we show that kernel-based learning algorithms achieve superior performance. In particular, recently developed sparse Bayesian methods, such as, Relevance Vector Machines (RVM), present a parsimonious solution when compared with Support Vector Machines (SVM), yet revealing competitive accuracy. This can lead to significant reduction in the computational complexity of the decision function, thereby making RVM more suitable for real-time applications.

Myxoma in the right ventricular outlow tract.

Abstract: We present a patient with dyspnea, cyanosis and presyncope during exercise related to intermittent obstruction of the right outflow tract by a myxoma of the right ventricle attached to the membranous interventricular septum by its pedicle. We also review the specific medical and surgical features of such tumors. Right ventricular myxomas are rare benign tumors and clinical manifestations depend mainly on size and site of attachment. They can cause obstructive events, and embolism is also possible. Both forms of clinical presentation are potentially fatal and surgical removal should be urgently. scheduled. This is usually curative, although recurrences have been reported, generally when these tumors are part of the Carney complex. The best surgical approach is individualized, and transesophageal echocardiography is an important tool in the decision. In our case right atriotomy was considered the best option.

An ECG compression approach based on a segment dictionary and bezier approximations

Abstract: This paper proposes a methodology for ECG (electrocardiograms) data compression based on R-R segmentation. An ECG can be seen as a quasi-periodic signal, where it is possible to find many similarities between heart beats. These similarities are explored by the proposed compression scheme through the use of a segment dictionary combined with an efficient form of progressive error codification. The dictionary is able to incorporate new patterns, in order to assure the algorithm adapts to changes in signal morphology. Experimental results reveal that high compression ratios are possible for highly regular signals, with irregular signals still achieving acceptable results.

Near real time noise detection during heart sound acquisition

Abstract: Heart sound is a valuable biosignal for early detection of a large set of cardiac diseases Ambient and physiological noise interference is one of the most usual and high probable incidents during heart sound acquisition It tends to change the prominent and crucial characteristics of heart sound which may possess important information for heart disease diagnosis In this paper, we propose a new method to detect ambient and internal body noises combined with heart sound The algorithm is based upon the periodic nature of heart sounds and physiologically inspired criteria A small segment of clean heart sound exhibiting periodicity in time as well as in the frequency domain is first detected and applied as a reference signal in sorting noise from the sound The achieved average sensitivity and specificity are 94% and 97%, respectively

Ventricular Arrhythmias Assessment

Abstract: An integrated framework for ventricular arrhythmias (VA) assessment, composed of two levels, is proposed in this work. The first level consists of four independent neural networks (NN), designed for specific detection tasks: signal quality, premature ventricular contractions (PVC), ventricular tachycardia (VT) and ventricular fibrillation (VF). Time and frequency domain features, obtained from the electrocardiogram (ECG) and selected through a correlation analysis procedure, form the inputs to the neural modules. The outputs feed the second layer, which consists of a global classifier (ANFIS structure), returns the global result for the VA assessment scheme. Sensitivity and specificity values, evaluated from public MIT- BIH databases, show the effectiveness of the proposed strategy.

Aneurisma da Aurícula Direita : Caso Clínico

Abstract: We report the case of a 49-year-old patient, with recent onset of fatigue, who was diagnosed with atrial fibrillation, which was cardioverted electrically. A diagnosis of right atrial aneurysm, with no other cardiac pathology, was made. An aneurysmectomy was performed. Both surgery and postoperative recovery were uneventful.

Acute Mitral Regurgitation due to Ruptured ePTFE

Abstract: Chordal replacement with expanded polytetrafluoroethylene (ePTFE) sutures has proven to be a simple, versatile, and durable technique for the treatment of prolapsed cusps causing mitral valve regurgitation. ePTFE is known for its strong resistance to tension, and is judged to be unbreakable under physiological conditions. Herein are reported two cases of rupture of synthetic chordae tendineae; the possible causes of this extremely rare finding are analyzed.

Origem ectópica da artéria coronária direita: a propósito de um caso clínico

Abstract: Coronary artery anomalies can occur in isolation or in association with other congenital heart defects. Clinical presentation ranges from asymptomatic forms to sudden cardiac death. The authors report a case of anomalous origin of the right coronary artery from the left sinus of Valsalva, diagnosed with multidetector computed tomography coronary angiography.

Primary cardiac angiosarcoma. Extended resection of the right atrial wall. Case report.

Abstract: We report the case of a 51-year-old patient who presented with tiredness and leg swelling, with recurrent pericardial effusion; a right atrial tumor, suggestive of sarcoma, was diagnosed, which responded poorly to chemotherapy. In the absence of metastases, surgery for excision of the tumor was undertaken. Two months after surgery she had a new recurrence of pericardial effusion and chemotherapy was reinitiated. She is currently well and asymptomatic, with no signs of recurrence ten months after surgery and nearly 24 months after the initial diagnosis.

ECG Compression through segment matching and progressive error encoding

Abstract: This work describes a lossy electrocardiogram (ECG) compression algorithm based on R-R segmentation and segment matching. An ECG can be thought of as a quasi-periodic signal, with many similarities existing between heartbeats acquired from the same source. Through the use of an adaptive dictionary, it is possible to explore the similarities between new and previously encountered patterns, incorporating new patterns when a significant change in morphology has been observed. Algorithm simulation reveals very high compression ratios are possible on very regular signals.