Biomedical subjects

P Laguna

Publications and source records attributed to P Laguna.

At least 19 recordsLinked to original sources

PubMed2006

[Laparoscopic pelvic surgery: Where do we stand in the year 2006?].

Laparoscopic radical prostatectomy has become an equivalent alternative to the open retropubic approach, offering the advantages of minimally invasive surgery. It is being applied increasingly in Germany and the rest of Europe. Whether the surgical robot da Vinci will be used for this procedure to the same extent as in the United States is unpredictable because of high investment and maintenance costs. Similarly, laparoscopic sacrocolpopexy has proven to be a viable option compared to open transabdominal or transvaginal surgery, showing a significant reduction in postoperative morbidity. The value of radical cystectomy is controversial despite proven feasability. On one hand, the technical difficulties of purely laparoscopic urinary diversion result in very long operating times, and in the case of the laparoscopically assisted creation of a neobladder, the advantage of this approach has to be questioned. On the other hand, a maximum rate of 30% of local recurrences and distant metastases indicates at least poor patient selection. In conclusion, this procedure should be limited to a few experienced centers.

Cystectomy↗

PubMed2005

Management of oral bleedings with recombinant factor VIIa in children with haemophilia A and inhibitor.

Dental extraction in patients with haemophilia A and high-titre inhibitor is always a high-risk procedure, which often presents a lot of problems associated with bleeding. Prothrombin complex concentrates or recombinant activated factor VII (rFVIIa) has been used to control bleeding. rFVIIa was administered to five boys with severe haemophilia A complicated with inhibitor, who underwent seven dental extractions. The age of the patients ranged between 8 and 13 years (median 10 years). The concentrate was administered in doses of 90-100 microg kg(-1) body weight. Duration in the therapy and intervals between rFVIIa doses depended on the severity of bleeding. rFVIIa was proven to be highly effective and no side-effects of the product were observed.

Blood Coagulation Factor Inhibitors↗

PubMed2004

Clinical efficacy, safety and pharmacokinetic properties of the factor VIII concentrate Haemoctin SDH in previously treated patients with severe haemophilia A.

Clinical efficacy, safety and pharmacokinetic properties of the high-purity double-virus inactivated plasma-derived factor VIII concentrate Haemoctin SDH (pdFVIII) were evaluated in three prospective open-label uncontrolled studies in previously treated patients (PTPs) with severe haemophilia A. The pharmacokinetic properties assessed at baseline and after 3 months of treatment are in accurate accordance with published data and remain unchanged over time (study A, n = 12). Mean terminal elimination half-life was 11.8 and 11.9 h, mean incremental recovery (IU dL(-1)/IU kg(-1)) was 2.3 and 2.0, respectively. Long-term efficacy and safety, in particular the potential immunogenicity, were investigated in a total of 53 PTPs (studies A and B) treated prophylactically and on-demand, as required. PdFVIII has shown to be effective in preventing and controlling bleeding episodes; 23.5% of patients were free of bleeding events. A total of 177 haemorrhages occurred with 74.0% resolving after a single infusion, 87.6% within two infusions. 98.3% of responses reported on haemorrhages were rated as 'excellent' or 'good'. Moreover, 'excellent' haemostatic efficacy has been demonstrated in 10 surgical procedures including general and severe orthopaedic interventions (study C). No complication occurred in any surgery. Few adverse events were reported, one patient developed a high-titre FVIII inhibitor without clinical relevance. In all three studies, over 6 million units were administered in nearly 4300 infusions, approximately 94% units or infusions were given for prophylaxis and only 6% for treatment on-demand. In conclusion, pdFVIII has shown to be effective, safe and well tolerated in long-term prophylaxis and treatment on-demand as well as after minor and major surgical procedures.

Adolescent↗

PubMed2004

Time course of ECG depolarization and repolarization changes during ischemia in PTCA recordings.

OBJECTIVES: In this work we studied the temporal evolution of changes in the electrocardiogram (ECG) as a consequence of the induced ischemia during prolonged coronary angioplasty, comparing the time course of indexes reflecting depolarization and those reflecting repolarization. METHODS: We considered both local (measured at specific points of the ECG) and global (obtained from the Karhunen-Loève transform) indexes. In particular, the evolution of Q, R and S wave amplitudes during ischemia was analyzed with respect to classical indexes such as ST level. As a measurement of sensitivity we used an Ischemic Changes Sensor (ICS), which reflects the capacity of an index to detect changes in the ECG. RESULTS: The results showed that, in leads with low-amplitude ST-T complexes, the S wave amplitude was more sensitive in detecting ischemia than was the commonly used index ST60. It was found that in such leads the S wave amplitude initially exhibited a delayed response to ischemia when compared to ST60, but its performance was better from the second minute of occlusion. The global indexes describing the ST-T complex were, in terms of the ICS, superior to the S wave amplitude for ischemia detection. CONCLUSIONS: Ischemic ECG changes occur both at repolarization and depolarization, with alterations in the depolarization period appearing later in time. Local indexes are less sensitive to ischemia than global ones.

Action Potentials↗

PubMed2003

Detection of body position changes using the surface electrocardiogram.

A method for detecting body position changes that uses the surface vectorcardiogram (VCG) is presented. Such changes are often manifested as sudden shifts in the electrical axis of the heart and can erroneously be interpreted as acute ischaemic events. Axis shifts were detected by analysing the rotation angles obtained from the alignment of successive VCG loops to a reference loop. Following the rejection of angles originating from noise events, the detection of body position changes was performed on the angle series using a Bayesian approach. On a database of ECG recordings from normal subjects performing a predefined sequence of body position changes, a detection rate of 92% and a false alarm rate of 7% was achieved.

Adult↗

PubMed2003

Coronary artery disease diagnosis based on exercise electrocardiogram indexes from repolarisation, depolarisation and heart rate variability.

Several indexes have been reported to improve the accuracy of exercise test electrocardiogram (ECG) analysis in the diagnosis of coronary artery disease (CAD), compared with the classical ST depression criterion. Some of them combine repolarisation measurements with heart rate (HR) information (such as the so-called ST/HR hysteresis); others are obtained from the depolarisation period (such as the Athens QRS score); finally, there are heart rate variability (HRV) indexes that account for the nervous system activity. The aim of this study was to identify the best exercise ECG indexes for CAD diagnosis. First, a method to automatically estimate repolarisation and depolarisation indexes in the presence of noise during a stress test was developed. The method is divided into three stages: first, a preprocessing step, where QRS detection, filtering and baseline beat rejection are applied to the raw ECG, prior to a weighted averaging; secondly, a post-processing step in which potentially noisy averaged beats are identified and discarded based on their noise variance; finally, the measurement step, in which ECG indexes are computed from the averaged beats. Then, a multivariate discriminant analysis was applied to classify patients referred for the exercise test into two groups: ischaemic (positive coronary angiography) and low-risk (Framingham risk index < 5%). HR-corrected repolarisation indexes improved the sensitivity (SE) and specificity (SP) of the classical exercise test (SE = 90%, SP = 79% against SE = 65%, SP = 66%). Depolarisation indexes also achieved an improvement over ST depression measurements (SE = 78%, SP = 81%). HRV indexes obtained the best classification results in our study population (SE = 94%, SP = 92%) by means of the very high-frequency power (VHF) (0.4-1 Hz) at stress peak.

Adult↗

PubMed2003

Estimation of the respiratory frequency using spatial information in the VCG.

A new method for extracting respiratory signals from the ECG/VCG is presented. The method is based on the alignment of an observed VCG loop to a reference loop with respect to the transformations of rotation and time synchronisation. The resulting series of estimated rotation angles reflects respiratory-induced changes in the electrical axis of the heart. The respiratory frequency is estimated by power spectral analysis of the derived respiration signal. The value of respiratory modulation of the heart rate is considered by analysing the cross power spectrum of the signals related to rotation angles and heart rate. For comparison, a respiratory signal derived from the QRS area of two different leads is implemented. The performance of the methods is validated on a database with simultaneously recorded VCG and respiratory signals acquired from 20 healthy subjects. The agreement between the respiratory frequencies obtained from the derived and the respiratory signals is presented. The angle-based respiratory signal is found to produce the best agreement with a gross median error of only 4.2%.

Algorithms↗

PubMed2002

[Control of the endotracheal cuff balloon pressure as a method of preventing laryngotracheal lesions in critically ill intubated patients].

OBJECTIVES: To study the development of tracheal stenosis after endotracheal intubation, percutaneous tracheotomy or both; to assess risk factors for tracheal stenosis and the relation of risk to endotracheal cuff pressure. PATIENTS AND METHODS: A prospective study enrolling patients sustaining endotracheal intubation longer than 8 hours and/or undergoing percutaneous tracheotomy. Cuff pressure was recorded at the moment of intubation and every 8 hours thereafter; a ceiling of 25 mm Hg was targeted. The patients were examined 6 months after discharge. RESULTS: Sixteen percutaneous tracheotomies were performed in the 95 patients enrolled (58 men, 37 women). The mean age was 54.1 +/- 19.7 years. The mean APACHE II score for all patients was 16.3 +/- 7.7 and the mean intubation time was 7.3 +/- 11 days, whereas the respective means for patients undergoing percutaneous tracheotomy were 18.4 +/- 7.6 and 20.5 +/- 19 days. Six months after discharge, 55 patients were examined for laryngotracheal lesions by fiberoptic endoscopy. Twenty-three of the remaining patients had died, 7 were lost to follow-up and 10 were only interviewed by telephone. Fiberoptic laryngotracheal endoscopy revealed minimal scarring and reduction of the endotracheal lumen. Reduction of the lumen was observed only in patients who had undergone percutaneous tracheotomy. CONCLUSIONS: Monitoring cuff pressure three times per day seems to contribute to preventing ischemic lesions and tracheal stenosis.

Adult↗

PubMed2001

Correlation between clinical, radiological and ultrasonographical image of knee joints in children with haemophilia.

The aims of the study were to evaluate the clinical, radiological and ultrasonographical images of knee joints in children with severe haemophilia and von Willebrand's disease, to determine the correlation between these images and to assess the usefulness of ultrasonography (USG) in evaluating the intensity of haemophilic arthropathy. Thirty-nine boys were included in the study, all of them with a past history of knee bleeds. The average age of the children was 10.02 +/- 3.01 years. In patients with slight (1-3 points) and moderate (4-7 points) radiological changes in knee joint bones, an increase in synovial fluid, considerable hypertrophy and inflammation of the synovium were observed in USG. In haemophilic patients with severe (8-13 points) bone changes, the amount of fluid was usually normal and there was slight inflammation but considerable hypertrophy of the synovium. Radiological evaluation of haemophilic arthropathy was made according to the Pettersson classification. A good correlation between the degree of cartilage damage in USG and the progression of bone changes in radiographs was found. Cartilage and bone damage progressed with the increase in the number of intra-articular haemorrhages into the knee joint. In our opinion USG is useful in evaluating the fluid, synovium and cartilage of joints in haemophiliacs.

Adolescent↗

PubMed2001

Control group and maintenance treatment with bacillus Calmette-Guerin for carcinoma in situ and/or high grade bladder tumors.

PURPOSE: Intravesical instillations of bacillus Calmette-Guerin have demonstrated satisfactory results in the treatment of vesical carcinoma in situ and high grade superficial bladder tumors. We designed a protocol to evaluate the decrease in tumor recurrence with maintenance therapy. MATERIALS AND METHODS: Between June 1989 and May 1995 an initial course of 6 intravesical instillations of Connaught strain bacillus Calmette-Guerin was administered in patients with carcinoma in situ and/or high grade superficial bladder tumors. Six months later 131 disease-free patients were randomly assigned to a control group or a maintenance therapy group that received 6 instillations every 6 months (6 x 6) for a 2-year period. RESULTS: Of the 126 evaluable patients at a mean followup of 79 months there were no significant differences in recurrence nor progression. A total of 16 patients (26.2%) in the control and 10 (15.1%) in the maintenance group had superficial relapse at a mean of 24 and 20 months, respectively (p = 0.07). Eight patients underwent radical cystectomy due to bladder contraction in 1, high grade superficial recurrence in 4 and disease progression in 3. Of the 65 patients on maintenance therapy 22 (33.85%) completed the planned 2-year treatment. CONCLUSIONS: Six-month maintenance therapy in patients treated initially for carcinoma in situ and/or high grade superficial bladder tumors who are disease-free at 6 months did not significantly decrease recurrence or progression.

Adult↗

PubMed2000

Grazing collisions of black holes via the excision of singularities.

We present the first simulations of non-head-on (grazing) collisions of binary black holes in which the singularities are excised from the simulation. Initially equal mass m black holes (spinning or not) are separated by approximately 10m and with impact parameter approximately 2m. Evolutions to t approximately 35m are obtained where two separate horizons are present for t approximately 3.8m; then a single enveloping horizon forms indicating that the holes merged. Apparent horizon area estimates suggest gravitational radiation of about 2%-3% of the total mass. The evolutions end after a moderate amount of time because of instabilities.

Journal Article↗

PubMed2000

Sampling rate and the estimation of ensemble variability for repetitive signals.

The measurement of ensemble variability in time-aligned event signals is studied in relation to sampling rate requirements. The theoretical analysis is based on statistical modelling of time misalignment in which the time resolution is limited by the length of the sampling interval. For different signal-to-noise ratios (SNRs), the sampling rate is derived which limits the misalignment effect to less than 10% of the noise effect. Each signal is assumed to be corrupted by additive noise. Using a normal QRS complex with a high SNR (approximately equal to 30 dB), a sampling rate of approximately 3 kHz is needed for accurate ensemble variability measurements. This result is surprising since it implies that the Nyquist rate is far too low for accurate variability measurements. The theoretical results are supplemented with results obtained from an ECG database of 94 subjects for which the ensemble variability is computed at different sampling rates using signal interpolation. The ensemble variability is substantially reduced (40%) when increasing the rate from 1 to 3 kHz, thus corroborating the results suggested by the theoretical analysis.

Electrocardiography↗

PubMed2000

Temporal evolution of traditional versus transformed ECG-based indexes in patients with induced myocardial ischemia.

The time course of changes in the electrocardiogram as a result of myocardial ischemia induced during prolonged coronary angioplasty has been studied. We have analyzed the electrocardiogram evolution during the occlusion in terms of the Ischemic Changes Sensor, which is a parameter that describes the capacity of different indexes to detect induced changes. Traditional indexes at specific time locations (ST level, T wave amplitude and position, and durations of QT interval and QRS complex) and global indexes (based on the Karhunen-Loève transform as applied to the QRS complex, ST-T complex, ST segment and T wave) have been considered. The global indexes better detected ischemic changes than the traditional indexes. The most sensitive were the index for the ST-T complex (89%) in the Karhunen-Loève transform-derived group and for the ST level (61%) in the traditional group. Changes in the ventricular repolarization period usually appeared earlier (77% of patients) than changes in the depolarization period (23% of patients). A similar percentage of patients exhibited the earliest ischemic changes in the T wave (41%) and in the ST segment (36%). The evolution of the Ischemic Changes Sensor parameters showed that the majority (60%) of the total changes occurred during the first minute of occlusion. The results suggest that the use of global electrocardiogram indexes better reflect ischemic changes than do traditional indexes, such as the ST segment deviation.

Angioplasty, Balloon, Coronary↗

PubMed2000

Prostate specific antigen and benign prostatic hyperplasia.

Benign prostatic hyperplasia is a common condition in males over 50 years, but prostate cancer can develop in the same population. Prostate specific antigen, the best marker for prostate cancer, is also produced by benign epithelial cells, and there is an overlapping phenomenon between both conditions. The better we understand the relationships between benign prostatic hyperplasia and prostate specific antigen, the higher will be the discrimination power of prostate specific antigen measurement as a marker for prostate cancer. Our scope includes a review of the latest published material to date on this subject.

Age Factors↗

PubMed2000

Vectorcardiographic loop alignment and the measurement of morphologic beat-to-beat variability in noisy signals.

The measurement of subtle morphologic beat-to-beat variability in the electrocardiogram (ECG)/vectorcardiogram (VCG) is complicated by the presence of noise which is caused by, e.g., respiration and muscular activity. A method was recently presented which reduces the influence of such noise by performing spatial and temporal alignment of VCG loops. The alignment is performed in terms of scaling, rotation and time synchronization of the loops. Using an ECG simulation model based on propagation of action potentials in cardiac tissue, the ability of the method to separate morphologic variability of physiological origin from respiratory activity was studied. Morphologic variability was created by introducing a random variation in action potential propagation between different compartments. The results indicate that the separation of these two activities can be done accurately at low to moderate noise levels (less than 10 microV). At high noise levels, the estimation of the rotation angles was found to break down in an abrupt manner. It was also shown that the breakdown noise level is strongly dependent on loop morphology; a planar loop corresponds to a lower breakdown noise level than does a nonplanar loop.

Action Potentials↗

PubMed2000

Improved heart rate variability signal analysis from the beat occurrence times according to the IPFM model.

The heart rate variability (HRV) is an extended tool to analyze the mechanisms controlling the cardiovascular system. In this paper, the integral pulse frequency modulation model (IPFM) is assumed. It generates the beat occurrence times from a modulating signal. This signal is thought to represent the autonomic nervous system action, mostly studied in its frequency components. Different spectral estimation methods try to infer the modulating signal characteristics from the available beat timing on the electrocardiogram signal. These methods estimate the spectrum through the heart period (HP) or the heart rate (HR) signal. We introduce a new time domain HRV signal, the Heart Timing (HT) signal. We demonstrate that this HT signal, in contrast with the HR or HP, makes it possible to recover an unbiased estimation of the modulating signal spectra. In this estimation we avoid the spurious components and the low-pass filtering effect generated when analyzing HR or HP.

Analysis of Variance↗

PubMed2000

Automatic detection of ST-T complex changes on the ECG using filtered RMS difference series: application to ambulatory ischemia monitoring.

A new detector is presented which finds changes in the repolarization phase (ST-T complex) of the cardiac cycle. It operates by applying a detection algorithm to the filtered root mean square (rms) series of differences between the beat segment (ST segment or ST-T complex) and an average pattern segment. The detector has been validated using the European ST-T database, which contains ST-T complex episodes manually annotated by cardiologists, resulting in sensitivity/positive predictivity of 85/86%, and 85/76%, for ST segment deviations and ST-T complex changes, respectively. The proposed detector has a performance similar to those which have a more complicated structure. The detector has the advantage of finding both ST segment deviations and entire ST-T complex changes thereby providing a wider characterization of the potential ischemic events. A post-processing stage, based on a cross-correlation analysis for the episodes in the rms series, is presented. With this stage subclinical events with repetitive pattern were found in around 20% of the recordings and improved the performance to 90/85%, and 89/76%, for ST segment and ST-T complex changes, respectively.

Algorithms↗

PubMed1999

Identification of the occluded artery in patients with myocardial ischemia induced by prolonged percutaneous transluminal coronary angioplasty using traditional vs transformed ECG-based indexes.

We have studied the spatial properties of ischemic changes as induced by prolonged angioplasty and how the changes are related to different ECG indexes. Indexes based on measurements at specific points in time (ST level at J + 60 ms point, maximal T wave amplitude and position, QT interval, and QRS duration) and global indexes (based on the Karhunen-Loève transform and applied to the QRS complex, ST-T complex, ST segment, and T wave), considering both repolarization and depolarization information, were analyzed. The changes during the occlusion period of the different indexes were used as variables in a multivariate discriminant analysis to determine which indexes showed the best discrimination of the three major occlusion sites (corresponding to LAD, RCA, and LCX coronary arteries). Occlusions in LCX artery were the most difficult to classify. With three local indexes (ST60 level measured in lead V3, T wave amplitude in I, and ST60 in III) it was possible to correctly classify 76% of patients by the occlusion site, and with three KLT-derived indexes (first-order KLT index for ST-T complex in I and for QRS in leads V3 and I) 83% of correct classification was obtained. Using six indexes for local and KLT-derived indexes the correct classification was increased to 85 and 90% of patients, respectively. The use of different ECG indexes (from different intervals) on quasiorthogonal leads permitted the identification of the occluded artery in patients undergoing PTCA and may be extended to more general use.

Angioplasty, Balloon, Coronary↗