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Biomedical subjects

P Laguna

Publications and source records attributed to P Laguna.

At least 37 records · Page 2Linked to original sources
PubMed1999

Analysis of the ST-T complex of the electrocardiogram using the Karhunen--Loève transform: adaptive monitoring and alternans detection.

The Karhunen-Loève transform (KLT) is applied to study the ventricular repolarisation period as reflected in the ST-T complex of the surface ECG. The KLT coefficients provide a sensitive means of quantitating ST-T shapes. A training set of ST-T complexes is used to derive a set of KLT basis vectors that permits representation of 90% of the signal energy using four KLT coefficients. As a truncated KLT expansion tends to favor representation of the signal over any additive noise, a time series of KLT coefficients obtained from successive ST-T complexes is better suited for representation of both medium-term variations (such as ischemic changes) and short-term variations (such as ST-T alternans) than discrete parameters such as the ST level or other local indices. For analysis of ischemic changes, an adaptive filter is described that can be used to estimate the KLT coefficient, yielding an increase in the signal-to-noise ratio of 10 dB (u = 0.1), with a convergence time of about three beats. A beat spectrum of the unfiltered KLT coefficient series is used for detection of ST-T alterans. These methods are illustrated with examples from the European ST-T Database. About 20% of records revealed quasi-periodic salvos of ischemic ST-T change episodes and another 20% exhibit repetitive, but not clearly periodic patterns of ST-T change episodes. About 5% of ischemic episodes were associated with ST-T alterans.

Electrocardiography↗
PubMed1998

[Detection of human herpesvirus 8 in patients with Kaposi's sarcoma or Castleman's disease associated with AIDS].

A new herpesvirus provisionally termed as KSHV or HHV-8 has been detected in lesions from AIDS-based Kaposi's sarcoma (KS) and from other KS clinical forms, and also in other tumors such as body cavity-based lymphomas or Castleman's disease (CD). We have assessed the presence of this novel herpesvirus in specimens from patients diagnosed with either AIDS and KS or AIDS and CD. DNA samples from skin lesions and peripheral blood obtained from 8 patients diagnosed with AIDS, seven with KS and one with multicentric CD were analyzed; skin specimens and peripheral blood samples from volunteer blood donors or from KS and CD free HIV seronegative patients were used as controls. Detection of the virus was done by PCR amplification of KS330 region, one of the HHV-8 sequences first reported. All skin lesions analysed tested positive for KS330; peripheral blood samples from 5 of the patients, including the one diagnosed with CD, showed also the virus sequence. All skin specimens and peripheral blood samples from controls were negative. From our results it can be concluded that the novel herpesvirus HHV-8 can also be detected in patients with AIDS-associated KS and AIDS-associated CD in Spain.

Acquired Immunodeficiency Syndrome↗
PubMed1998

Comparative study of local and Karhunen-Loève-based ST-T indexes in recordings from human subjects with induced myocardial ischemia.

In this work we studied ST-T complex changes in the ECG as result of induced ischemia. The principal aim was to determine whether global changes in the ST-T complex were more sensitive markers of ischemic alterations than those based on measurements of changes at specific locations on ST segment or T wave. High-resolution ECGs from patients undergoing percutaneous transluminal coronary angioplasty in one of the major coronary arteries were analyzed to give a description of the period from the end of active depolarization (QRS complex) to the end of active repolarization (T wave). During artery occlusion traditional local measurements of the ST-T complex were compared to global measurements based on the Karhunen-Loève transform. An ischemic change sensor parameter was estimated for each of the studied indexes showing that global measurements detected changes better in the repolarization period in a larger number of leads and with higher sensitivity (more than 85%) than was done using local measurements (sensitivity of 64% with ST level, 33% with T-wave maximum position, and 37% with T-wave maximum amplitude). Using these global indexes it was found that most cases of ST-segment changes were accompanied by T-wave changes (72% of patients). With the use of traditional indexes 23% of patients showed no changes in the repolarization period, whereas with global indexes this percentage decreased to 8%. Thus a global representation of the entire ST-T complex appears to be more suitable than local measurements when studying the initial stages of myocardial ischemia.

Algorithms↗
PubMed1998

Power spectral density of unevenly sampled data by least-square analysis: performance and application to heart rate signals.

This work studies the frequency behavior of a least-square method to estimate the power spectral density of unevenly sampled signals. When the uneven sampling can be modeled as uniform sampling plus a stationary random deviation, this spectrum results in a periodic repetition of the original continuous time spectrum at the mean Nyquist frequency, with a low-pass effect affecting upper frequency bands that depends on the sampling dispersion. If the dispersion is small compared with the mean sampling period, the estimation at the base band is unbiased with practically no dispersion. When uneven sampling is modeled by a deterministic sinusoidal variation respect to the uniform sampling the obtained results are in agreement with those obtained for small random deviation. This approximation is usually well satisfied in signals like heart rate (HR) series. The theoretically predicted performance has been tested and corroborated with simulated and real HR signals. The Lomb method has been compared with the classical power spectral density (PSD) estimators that include resampling to get uniform sampling. We have found that the Lomb method avoids the major problem of classical methods: the low-pass effect of the resampling. Also only frequencies up to the mean Nyquist frequency should be considered (lower than 0.5 Hz if the HR is lower than 60 bpm). We conclude that for PSD estimation of unevenly sampled signals the Lomb method is more suitable than fast Fourier transform or autoregressive estimate with linear or cubic interpolation. In extreme situations (low-HR or high-frequency components) the Lomb estimate still introduces high-frequency contamination that suggest further studies of superior performance interpolators. In the case of HR signals we have also marked the convenience of selecting a stationary heart rate period to carry out a heart rate variability analysis.

Cardiac Pacing, Artificial↗
PubMed1998

[Abscess of the psoas muscle: analysis of 11 cases and review of the literature].

BACKGROUND: Abscess of the psoas muscle (AP) is an infrequent disease of difficult diagnosis, developing spontaneously (primary AP) or by extension of a subjacent infection (secondary AP). In recent years changes have been observed in its etiology, advances in its diagnosis and modifications in the treatment schedules. METHODS: The cases of AP diagnosed from 1983-1996 were retrospectively studied. RESULTS: The cases included 11 AP, 5 (45%) primary and 6 (55%) secondary, of which the source of origin were: spondylitis in four, sacroiliac arthritis in one and intestinal in another. The clinical presentation was characterized by its prolonged course (evolution of symptoms greater than 30 days in 64% of the cases), with the most frequent symptoms being flank/abdominal pain (82%) and hip/inguinal pain (45%), with fever being presented in only 36%. The diagnostic profitability of echography and computerized tomography (CT) were 57% (4/7) and 91% (10/11), respectively. One case was diagnosed with magnetic resonance. The causal microorganisms were: Mycobacterium tuberculosis (36% of the cases), Staphylococcus aureus (18%), polymicrobian flora (18%) and Salmonella enteritidis, Streptococcus intermedius and Escherichia coli in 9% each. Eight cases (73%) underwent percutaneous (5 cases) and surgical (3 cases) drainage, with the evolution being favorable in 10 (91%) and death in one despite adequate medicosurgical treatment. CONCLUSIONS: The clinical presentation of AP is often unspecific, thereby delaying its diagnosis, and thus, CT is the procedure of choice. The tuberculous etiology continues to be frequent in our environment. Ultrasonographic or CT guided percutaneous drainage is a valid therapeutic alternative versus surgery.

Adolescent↗
PubMed1997

Automatic measurement of corrected QT interval in Holter recordings: comparison of its dynamic behavior in patients after myocardial infarction with and without life-threatening arrhythmias.

This study was designed to determine the value of automatic corrected QT-interval measurement in Holter tapes in patients after myocardial infarction as a marker of life-threatening ventricular arrhythmias. We compared the corrected QT interval, automatically measured in 24-hour Holter recordings, in two groups of patients after myocardial infarction: group I was composed of 14 patients admitted consecutively to our hospital for documented sustained ventricular tachycardia or out-of-hospital cardiac arrest. Group II consisted of 28 patients with previous myocardial infarction with characteristics similar to those of group I, but without malignant ventricular arrhythmias in the follow-up. The global mean 24-hour corrected QT interval was longer in group I (425 +/- 20 msec) than in those patients after myocardial infarction without arrhythmias (group II) (405 +/- 17 msec; p < 0.01). Furthermore, a significant proportion of patients of group I (seven of 14) exhibited more peaks of corrected QT longer than 500 msec compared with patients of group II (two of 28; p < 0.005). A circadian rhythm of corrected QT peaks was observed in group I, having a significantly higher incidence from 11 PM to 11 AM (p < 0.05). We conclude that automatic corrected QT-interval measurement on Holter electrocardiogram is now available and feasible. Our results suggest that this is a marker for risk assessment of life-threatening ventricular arrhythmias. Large-scale trials are needed to confirm these results and to determine the predictive value of this technique for risk stratification.

Algorithms↗
PubMed1997

Treatment options for distal ureteral stones.

OBJECTIVE: To review the currently available treatment modalities for distal ureteral stones and outline our protocol for management. METHODS: Current literature on each treatment modality, from expectant management to open ureterolithotomy, and special procedures were analyzed. RESULTS: Our treatment protocol for distal ureteral stones is based mainly on the stone size. Distal ureteral stones that measure 5 mm or less are best managed initially by ureteroscopy. Stones greater than 5 mm are treated initially by ESWL, with a success rate of at least 80%. CONCLUSION: The initial choice of treatment must be dictated by the practical concerns of available equipment, experience of the surgeon and cost of treatment. The trend is initial management by ESWL, although recent studies show better results in terms of cost for ureteroscopy.

Humans↗
PubMed1997

[Detection of cognitive deterioration in elderly patients attending an emergency hospital service].

BACKGROUND: An increasing proportion of patients attended at hospital emergence departments (HED) are elderly people. OBJECTIVES: a) To check the reliability of the usual medical assessment to detect the cognitive deterioration in elderly people attended at HED, compared with that performed systematically by means of an evaluation test of cognitive functions; b) to study the applicability of such a test in HED, on the basis of the time necessary for its administration, and c) to describe the deterioration prevalence in that group of patients and identify the possible associated risks for its detection in patients. PATIENTS AND METHODS: Prospective study including patients aged > or = 60 years attended at a HED, using the orientation, memory and concentration test (OMC) to perform the cognitive assessment. RESULTS: A total of 352 patients who had no exclusion criteria out of the 536 attended during the study period were included. Cognitive deterioration was not detected in 111 patients (31.5%); it was mild in 147 (41.8%), moderate in 71 (20.2%) and severe in 23 (6.5%). In patients with moderate-severe deterioration according to the OMC test, such a deterioration was detected by the usual medical evaluation in 7% of cases. The mean time in completing the test was 2.6 +/- 0.9 minutes. An age > or = 80 years was associated with an increased relative risk for detecting moderate-severe cognitive deterioration (1.98; 95% CI, 1.42-2.78; p < 0.001), whereas the discharge diagnosis of respiratory disease was associated with a decrease of the relative risk (0.41; 95% CI, 0.19-0.89; p < 0.05). No association was observed with other factors, such as gender, home residence or final destination from the emergency department. CONCLUSIONS: The prevalence of cognitive deterioration in elderly people attended at HED is high and increases with age. The OMC test can be administered at HED to detect cognitive deterioration, which is not frequently detected by the usual medical assessment.

Age Factors↗
PubMed1996

Adaptive estimation of QRS complex wave features of ECG signal by the Hermite model.

The most characteristic wave set in ECG signals is the QRS complex. Automatic procedures to classify the QRS are very useful in the diagnosis of cardiac dysfunctions. Early detection and classification of QRS changes are important in real-time monitoring. ECG data compression is also important for storage and data transmission. An Adaptive Hermite Model Estimation System (AHMES) is presented for on-line beat-to-beat estimation of the features that describe the QRS complex with the Hermite model. The AHMES is based on the multiple-input adaptive linear combiner, using as inputs the succession of the QRS complexes and the Hermite functions, where a procedure has been incorporated to adaptively estimate a width related parameter b. The system allows an efficient real-time parameter extraction for classification and data compression. The performance of the AHMES is compared with that of direct feature estimation, studying the improvement in signal-to-noise ratio. In addition, the effect of misalignment at the QRS mark is shown to become a neglecting low-pass effect. The results allow the conditions in which the AHMES improves the direct estimate to be established. The application is shown, for subsequent classification, of the AHMES in extracting the QRS features of an ECG signal with the bigeminy phenomena. Another application is highlighted that helps wide ectopic beats detection using the width parameter b.

Electrocardiography↗
PubMed1996

In situ transitional cell carcinoma involvement of prostatic urethra: bacillus Calmette-Guérin therapy without previous transurethral resection of the prostate.

OBJECTIVES: Bacillus Calmette-Guérin (BCG) has demonstrated both the efficacy in patients with carcinoma in situ (CIS) of the bladder and the penetration in the prostate (granulomas) after endovesical treatment. We treated patients with CIS of the prostatic urethra with bladder instillations of BCG without previous transurethral resection to assess the local therapeutic effect. METHODS: Eighteen patients with CIS of the prostatic urethra (15 multifocal CIS and 15 associated to superficial bladder carcinoma) were treated with endovesical instillations of 81 mg of BCG Connaught weekly for 6 weeks. RESULTS: After a mean follow-up of 31 months, 14 of 18 patients had complete response, 3 had progression (2 in the prostate and 1 in the bladder); diffuse CIS of the bladder persisted in 1 patient. Three patients required cystectomy and 1 underwent palliative transurethral resection. Fifteen patients are alive with no evidence of disease, 2 patients died due to progression of the disease, and 1 is alive with tumor. CONCLUSIONS: The presence of CIS in the prostatic urethra can be managed with endovesical BCG as initial treatment with fairly good success. There is no need for transurethral resection, even though a loop biopsy may have to be obtained at the first control examination to make sure there is no stromal invasion.

Administration, Intravesical↗
PubMed1996

[Utilization of antibiotics in a hospital emergency department. Quality of prescription].

OBJECTIVES: To know the frequency of antibiotic prescription, the conditions that motivate their usage, and to evaluate the quality of such therapies in a hospital emergency department (HED). METHODS: Retrospective study of 2,677 patients attended at a HED for a one-month period including those who had antibiotics prescribed in the discharge report. The parameters used to evaluate the therapeutic quality included the condition amenable to antibiotic therapy, appropriate antibiotic, dosage, interval of administration, and duration. Each parameter had a score which was used to quantitate the quality in a 0 to 100 scale. RESULTS: A total of 288 patients (10.7%) had antibiotics prescribed for treatment of respiratory tract infections (53.8%) and urinary tract infections (19.4%). The antibiotic group that accounted for most prescriptions was broad-spectrum penicillins (45%), followed by quinolones (12.8%), and urinary antiseptics (11.4%). Only 100 (50.3%) treatments were considered correct for all parameters analyzed. The most inadequate parameters were: non-appropriate antibiotic in 17.1% of cases and incorrect length of administration in 39.9%. The average quality according to scale was 89.6 (SD = 20.3). A lower quality was observed for treatments prescribed when on duty compared with normal working time (p = 0.006). CONCLUSIONS: Antibiotics are drugs frequently prescribed in HED. Errors were detected in choosing antibiotic therapies and antibiotic course duration in our department, which makes the adoption of intervention measures for its correction necessary.

Drug Prescriptions↗
PubMed1995

Karhunen-Loève transform as a tool to analyze the ST-segment. Comparison with QT interval.

The spatial and temporal courses of ventricular repolarization are quite sensitive to the biochemical and biophysiologic environment of the myocardial cells, and are therefore often an early marker of heart disease, particularly of ischemia. The detailed morphology of the surface electrocardiogram contains considerable information about the repolarization process. The ST-segment changes with ischemia, injury, and drugs. The QT interval is affected by drugs, heart rate, and autonomic tone, and in some situations may identify individuals at high risk for arrhythmias and sudden death. Variability in the shape, including duration, of the ST-T waves reflects autonomic nervous system activity and may identify high-risk patients. Automated methods for quantitatively characterizing ST-T complexes are important in studying long-term electrocardiographic records. Two computer-based measurement procedures for characterizing the repolarization period were comparatively analyzed: Karhunen-Loève (KL) transform representation of the ST-T shape and measurement of beat-to beat durations of repolarization (QT intervals). The results of KL transform representation and time-domain QT measurement algorithms for studying the repolarization period of the electrocardiogram on the European ST-T database are presented. It was found that about 20% of the records present a quasiperiodic KL pattern of ischemic ST-T activity and another 20% exhibit repetitive but not clearly periodic patterns of ischemic ST-T changes. From these ischemic records, 50% showed QT variations in at least one lead associated with the ischemic episodes.

Algorithms↗
PubMed1995

[Open surgery of calculus of the kidney pelvis. Results and complications in the era of extracorporeal lithotripsy].

From 1989 to 1993, 11,535 extracorporeal shock wave lithotripsy (ESWL) sessions were performed in 6,066 patients in our centre. In contrast, simple or extended pyelolithotomy was the treatment of choice in a small group of patients. The object of this paper is to review the results and complications of this type of operation. A total of 57 pyelolithotomies was performed, including 33 extended pyelolithotomies, in 55 patients (26 men and 29 women). The mean age of the series was 50 years (range: 5-77). The operated kidney was the left kidney in 34 cases and the right kidney in 23 cases. The mean interval between the diagnosis and the operation was 31 months. 64% of the patients had history of stone disease (33 ipsilateral and 2 bilateral). Thirteen patients had already been treated by ESWL (10 patients), percutaneous nephrolithotomy (PNL) (2 cases) and one case had previously undergone pyelolithotomy. A urinary tract infection was observed in 26 patients (47%). The incision consisted of lumbotomy in 40 patients (71%), or a subcostal incision in 12 cases. The mean operating time was 161 minutes (range: 90-245) and the mean intraoperative bleeding was 500 ml. Thirteen patients were transfused (23%). The renal artery had to be clamped in 9 cases (for an average of 19 minutes). After a mean follow-up of 20 month, 50.8% of patients were stone-free. 49% of patients presented residual caliceal fragments on the immediate postoperative X-ray. One patient had to be treated by percutaneous nephrolithotomy and ESWL. 12 cases (41% of patients with residual fragments) required subsequent treatment by ESWL and the remaining patients with residual fragments were asymptomatic and did not receive any further treatment. The immediate postoperative complication rate was 17% and 10% of patients developed late postoperative complications. Simple or extended pyelolithotomy remains an effective treatment for stones of the renal pelvis, either on its own or associated with ESWL. However, the possibility of serious complications demands meticulous patient selection.

Adolescent↗