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R C Sousa

Publications and source records attributed to R C Sousa.

12 recordsLinked to original sources
PubMed2003

Quasiballistic magnetization reversal.

We demonstrate a quasiballistic switching of the magnetization in a microscopic magnetoresistive memory cell. By means of time resolved magnetotransport, we follow the large angle precession of the free layer magnetization of a spin valve cell upon application of transverse magnetic field pulses. Stopping the field pulse after a 180 degrees precession rotation leads to magnetization reversal with reversal times as short as 165 ps. This switching mode represents the fundamental ultrafast limit of field induced magnetization reversal.

Journal Article↗
PubMed2003

Phase coherent precessional magnetization reversal in microscopic spin valve elements.

We evidence multiple coherent precessional magnetization reversal in microscopic spin valves. Stable, reversible, and highly efficient magnetization switching is triggered by transverse field pulses as short as 140 ps with energies down to 15 pJ. At high fields a phase coherent reversal is found revealing periodic transitions from switching to nonswitching under variation of pulse parameters. At the low field limit the existence of a relaxation dominated regime is established allowing switching by pulse amplitudes below the quasistatic switching threshold.

Journal Article↗
PubMed1995

[The contribution and usefulness of routine intraoperative transesophageal echocardiography in cardiac surgery. An analysis of 130 consecutive cases].

PURPOSE: To assess the value of routine intraoperative transesophageal echocardiography (TEE) in unselected patients (P) undergoing cardiac surgery. DESIGN: Routine intraoperative TEE in unselected patients undergoing cardiac surgery and evaluation of its usefulness and contribute to a successful surgery. PATIENTS: In-hospital patients from cardiology, cardiac surgery and intensive care departments of a general hospital classified as a reference medical centre in cardiovascular pathology. MATERIAL AND METHODS: From February 1994 to May 1994 an intraoperative TEE was routinely performed in patients undergoing cardiac surgery. A total of 130 TEE studies were made corresponding to 128 patients, 69 males and 61 females, with a mean age of 49.4 +/- 12.1 years. Indications for surgery were as following: a) Coronary artery bypass grafting (C.A.B.G.)-39; b) Valvular surgery-76; c) C.A.B.G. and valvular surgery-5; d) Thoracic aorta pathology associated or not to aortic valve surgery and/or coronary arteries re-implantation-6; e) Other-4. TEE performed using either a monoplane, biplane or multiplane probe and the images acquisition was made before thoracotomy and cardiopulmonary bypass (CPB) and after CPB with hemodynamic stabilization. RESULTS: Pre CPB imaging yielded unsuspected findings in 11 P (8.5%) that changed the planned surgery in 7 cases (5.4%). Post CPB echo study, which was performed after hemodynamic stabilization, modified the surgical strategy in 13 cases (10.9%) avoiding 1 predetermined surgical procedure (tricuspid ring annuloplasty) and a new surgery in another case, leading to a 3 non-predetermined surgical procedures (by showing significative tricuspid regurgitation), to a further surgery in the same valve in 6 patients (mitral paravalvular leak with significative regurgitation in 1P, another mitral prosthesis dysfunction in 1P, residual mitral valve insufficiency after mitral valve repair in 3 P and aortic prosthesis dysfunction in 1 P), to a intraaortic counterpulsation balloon device in 1 P and to new CPB due to an insufficient extraction of calcified pericardium in one case of constrictive pericarditis. In 23 cases (17.7%) TEE has modified the anesthetic procedure by demonstrating signs of hemodynamic changes before Swan-Ganz catheter, thus prompting changes in the administrations of fluids and either in inotropic or vasodilator agents. In total, intraoperative TEE has changed the surgical and/or anesthetic plan in 43 cases (33.0%). There was no difficulties or complications related to the procedure. CONCLUSION: These data indicate that intraoperative TEE is useful in formulating the surgical plan and assessing immediate operative results as well as a guide to anesthetic procedures. Its high rentabillity in modifying the surgical and/or anesthetic plans lead us to believe that it must be used as a routine procedure in patients undergoing cardiac surgery.

Adult↗
PubMed1995

[The echocardiographic assessment of wall regurgitant jets in prosthetic mitral valves: the superiority of multiplanar transesophageal sections over standard sections].

OBJECTIVES: The purpose of this study was to determine whether multiplanar (MP) transesophageal echocardiographic views were superior to standard views (ST), in the evaluation of mitral prosthesis regurgitation (MR), particularly in presence of wall regurgitant jets. METHODS: We studied all mitral prostheses (n = 43) in which pathological mitral regurgitation had been detected by multiplanar TEE between January 1993 and March 1994. Regurgitant prostheses were classified in two groups according to the presence of wall regurgitant jets and maximum turbulent color flow areas (Amax.) were measured on standard (0 and 90 degrees) and MP (0 to 180 degrees) views. RESULTS: The Amax. detected on ST views were 5.80 +/- 4.60 cm2 and on MP 7.42 +/- 5.13 cm2. Student's test was used to compare both areas and significant differences were found: 1.61 cm2; 95% confidence interval from 0.94 to 2.28 cm2; p = 0.000025. The sample was divided in two groups, A (n = 33): with wall jets and B (n = 10): without wall jets. The Amax. for group A was 5.64 +/- 4.30 cm2 in ST views, and 7.51 +/- 5.12 cm2 in MP. The difference was statistically significant: 1.86 cm2, 95% c.i. from 1.04 to 2.68 cm2; p = 0.00009. Differences for group B were also statistically significant: 0.68 cm2; p = 0.0172. MP views detected a bigger regurgitant area in 26 of the 43 cases (60%). The difference between ST and MP views was significantly bigger for group A than for group B: mean 1.18 cm2; p = 0.0176. MP views detected a severer degree of MR, classified as mild moderate and severe according to the color flow area, than ST views in 8 patients. All of them had wall regurgitant jets. Three had been considered normal on ST views. CONCLUSION: We conclude that MP transesophageal views are significantly superior to ST in the assessment of regurgitant prosthetic mitral valves, particularly in presence of wall regurgitant jets. Our data strongly suggest that multiplanar TEE is the procedure of choice in the assessment of wall regurgitant mitral prostheses.

Adult↗
PubMed1995

[Mitral valve with double orifice. Report of a clinical case].

Double mitral valve orifice is an uncommon congenital heart defect. The isolated occurrence of this anomaly is exceptional and, more often, is encountered in association with other congenital cardiac abnormalities. We present a case of a functionally normal double mitral valve orifice, an "incomplete bridge" type, diagnosed by two-dimensional transthoracic echocardiography in a ten years old patient. Due to its rarity we have reviewed and discussed this entity and the echocardiographic features of its types.

Child↗
PubMed1994

[Multiplanar transesophageal echocardiography: technique, methodology, and applications].

OBJECTIVE: To present the experience of transesophageal echocardiography with a multiplane probe, its methodology, the advantages, disadvantages and diagnostic improvements of this type of probe. SETTING: Laboratory of Echocardiography of the General Hospital Gregorio Marañon. MATERIAL AND METHODS: Analysis of the first 1000 examinations performed on hospitalized patients and outpatients, in most cases to study either native valvular heart disease and valvular prosthesis or to search for embolic sources. We evaluate the advantages, disadvantages, initial difficulties and complications of this type of probe. RESULTS: Multiplane probe provides continuous imaging from 0 degree to 180 degrees without need of intraesophagic movements. This type of probe increases the diagnostic capability of transesophagic echocardiography because it performs as a scanning of anatomy and pathological features of cardiac chambers and great vessels. Pulmonary artery and its branches, right heart chambers and tricuspid valve, inferior and superior vena cava, outflow tract of both ventricles, aortic root, pulmonary veins and segmental views of both ventricles are well analyzed. Also in native and prosthetic regurgitants jets, cardiac tumors and other masses, diagnosis and complications of endocarditis, aortic dissection and in anomalous return of pulmonary veins, multiplane probe proves to be more informative. There was no difficulties in the intubation despite the bigger size of the transducer. No severe complications occurred. The higher price and the initial more difficult understanding of the images are the only disadvantages we have found. CONCLUSIONS: Multiplane probe contributes to increase diagnostic capability of transesophageal echocardiography without significant risk and it is an important and promising refinement of the transesophageal technique.

Echocardiography, Transesophageal↗
PubMed1994

[Value of transesophageal echocardiography in the assessment of blunt chest trauma: correlation with electrocardiogram, heart enzymes, and transthoracic echocardiogram].

OBJECTIVE: To asses the feasibility, usefulness and clinical rentability of the transesophageal echocardiography (TEE) in the evaluation of patients suffering a severe blunt chest trauma as well as to correlate the TEE findings with those provided by the conventional electrocardiogram (ECG), cardiac isoenzymes assay and transthoracic echocardiography (TTE). DESIGN: Prospective study using ECG, blood cardiac enzymes assay, TTE and TEE. SETTING: Intensive care unit of a general hospital. PATIENTS: We studied 34 patients admitted with blunt chest trauma and suspected cardiac contusion in spite of the existence of other traumatic injuries in some of them. There were 23 (67.6%) males and 11 females, with a mean age of 37.1 +/- 19.4 years (range: 16-69 years). MATERIAL AND METHODS: Patients with a previous history of cardiovascular or chronic pulmonary disease, cardiac arrest upon admission or positive cocaine or amphetamine levels in the urine were excluded from the study. Suspected cardiac contusion was established by clinical data, electrocardiographic findings, enzymes blood values (CPK-total and MB-fraction) and TTE findings. Additionally, a TEE was performed in each patient. Patients were stratified into two groups according to the TEE findings: Group A patients had signs compatible with cardiac contusion and in Group B patients there was a lack of evidence to substantiate this diagnosis. Those tests were evaluated in respect to their accuracy in the diagnosis of cardiac contusion when compared to transesophageal echocardiography and TEE findings were compared, whenever possible, to surgical or necropsic findings. RESULTS: We found TEE signs of cardiac injury in 22 (64.7%) patients and a wide spectrum of traumatic cardiac abnormalities were identified. TEE signs of ventricular injury were found in 15 pts of Group A (68.2%) being the right ventricle the most frequent affected. There were also two cases of mitral leaflet rupture, one case of tricuspid valve prolapse (with severe tricuspid regurgitation and associated with right ventricle wall motion abnormalities) and seven cases of pericardial effusion as well as one case of thoracic aortic dissection. In every patient submitted to cardiothoracic surgery or necropsy the TEE findings were confirmed. TEE provided significant information, sometimes crucial, to the patient evaluation and management, it was performed without any difficulty and it doesn't carried out any related complication. TTE was technically suboptimal in 53% and fail to demonstrate many cases of cardiac contusion and the thoracic aorta lesion, being the number of cardiovascular injuries demonstrated by TEE significantly higher (p = 0.029). No statistically significant difference was found between the number of patients with either an abnormal ECG or high values of CPK-MB in each group. Neither clinical findings, cardiac enzymes values, serial ECG's nor TTE predicted all the patients who had traumatic cardiac injury and those would subsequently developed complications related to cardiac contusion. CONCLUSIONS: A severe blunt chest trauma frequently results in cardiac injury. The ECG and the CPK-MB measurements appears both to be fairly sensitive and specific tests in the cardiac contusion diagnosis. TTE has shown to have important limitations in these patients, thus not allowing neither a complete echo evaluation nor a reliable one. TEE plays an important role in the evaluation and management of this type of patients providing rapid diagnostic information and being of high value in the rule out cardiac contusion as well as in the establishment of a specific diagnosis of cardiac and/or thoracic aorta injuries with a consequent better assessment and treatment strategy in these patients.

Adolescent↗
PubMed1994

[Transesophageal echocardiography assessment of regurgitant jets of eccentric geometry in mitral valve prosthesis: superiority of multiplanar sections over standard sections].

OBJECTIVE: The purpose of this study was to determine whether multiplanar (MP) transesophageal echocardiographic views were superior to standard views (ST) at 0 degree and 90 degrees in the evaluation of mitral prosthesis regurgitation (MR), particularly in presence of wall regurgitant jets. DESIGN: Comparison between MP and ST views in the evaluation of mitral prosthesis regurgitation. SETTING: Laboratory of Echocardiography of the General Hospital Gregorio Marañon. MATERIAL AND METHODS: Study of all mitral prostheses in which pathological mitral regurgitation had been detected by multiplanar TEE, between January 1993 and March 1994. Regurgitation prosthesis were classified in two groups according to the presence of wall regurgitation jets and maximum turbulent color flow areas (MAX) were measured on standard (0 degree and 90 degrees) and MP (0 degree to 180 degrees) views. The sample was divided in two groups, A (n = 33): with wall jets and B (n = 10): without wall jets. Students' t test was used to compare both areas using a 95% confidence interval (95% c.i.). RESULTS: MAX detected on ST views were of 5.80 +/- 4.60 cm2 and on MP were of 7.42 +/- 5.13 cm2 being the difference statistically significant: 1.61 cm2, 95% c.i. from 0.94 to 2.28 cm2, p = 0.000025. MAX for group A was of 5.64 +/- 4.30 cm2 in ST views and of 7.51 +/- 5.12 cm2 in MP views, being the difference 1.86 cm2, 95% c.i. from 1.04 to 2.68; p = 0.00009. Differences for group B were also statistically significant: 0.68 cm2, p = 0.0176. Mitral regurgitation (MR) was classified as mild, moderate and severe according to the color flow area. MP views detected a severer degree of MR than ST views in 8 patients, all of them with wall regurgitation jets. Three of these cases had been considered normal on ST views. CONCLUSIONS: Multiplanar transesophageal views are significantly superior to standard views in the assessment of regurgitant prosthetic mitral valves, particularly in presence of wall regurgitant jets. Our data strongly suggest that multiplanar TEE is the procedure of choice in the assessment of wall regurgitant mitral prostheses.

Adult↗
PubMed1993

Abdominal myomectomy in the treatment of infertility.

OBJECTIVE: To determine the effect of abdominal myomectomy as a treatment for infertility in women with uterine leiomyoma. METHODS: Records were reviewed for 37 women at Johns Hopkins Hospital who underwent myomectomy as a primary procedure for infertility between 1975 and 1990. RESULTS: Kaplan-Meier life-table analysis demonstrated a cumulative pregnancy rate of 57% and live birth rate of 48%. The size or number of myomas did not affect either the pregnancy rate or the myoma recurrence rate. The presence of pelvic adhesions at the time of myomectomy significantly reduced the chance of conception (P < 0.05). Adhesions were documented in 13 (68%) of 19 patients who underwent abdominal surgery at a later date. CONCLUSIONS: Nearly half of the infertile women with uterine leiomyoma were able to bear children following abdominal myomectomy. Adhesion formation appears to be a common occurrence following myomectomy and reduces its effectiveness when present before surgery.

Adult↗
PubMed1993

[Dilated cardiomyopathy in a patient with Becker's muscular dystrophy. A clinical case report].

The authors report a case of dilated cardiomyopathy caused by a muscular dystrophy, namely Becker's disease. The peculiarity of this case is the fact that the patient has lived enough time to have clinical manifestations of myocardiopathy because, in general, in this myopathy, the affected males have a short life and the early myocardial involvement is rare. A particular attention is paid to the need of consulting the cardiac patients not forgetting an eventual causal systemic disease and to the crucial importance of the genetic counselling in that kind of diseases.

Adult↗
PubMedDate not supplied

[Benign prostatic hyperplasia. Guidelines and recommendations in urological clinical practice].

After reviewing the clinical, diagnostic and therapeutic attitudes related to benign prostatic hyperplasia, the authors present guidelines for generalists in what concerns practical attitudes and when and how to refer their patients to the urologist. Based on the criteria presented, generalists must refer their patients to a urologist in the presence of mild or severe symptoms, ages below 50, diabetes or neurological perturbations, dysfunctional voiding, palpable bladder, palpable nodule or a diffusely hardened or asymmetric gland revealed by digital rectal examination, haematuria, urinary tract infection, renal impairment or PSA above 4 ng/ml in patients under 70 years of age.

Adult↗