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Biomedical subjects

R W Vieira

Publications and source records attributed to R W Vieira.

At least 19 recordsLinked to original sources
PubMed2003

Standardization of an isolated pig heart preparation with parabiotic circulation: methodological considerations.

In the present study we standardized an experimental model of parabiotic circulation of isolated pig heart. The isolated heart was perfused with arterial blood from a second animal as support and submitted to regional ischemia for 30 min, followed by total ischemia for 90 min and reperfusion for 90 min. Parameters for measurement of ventricular performance using different indices measured directly or indirectly from intraventricular pressure were defined as: maximum peak pressure, final diastolic pressure, pressure developed, first derivative of maximum pressure (dP/dt max), first derivative of minimum pressure (dP/dt min), systolic stress of the left ventricle (sigmas), and maximum elastance of the left ventricle. Isolated hearts subjected to regional and global ischemia presented significant worsening of all measured parameters. Less discriminative parameters were dP/dt max and dP/dt min. Elastance was the most sensitive parameter during the reperfusion period, demonstrating an early loss of ventricular function during reperfusion. The model proved to be stable and reproducible and permitted the study of several variables in the isolated heart, such as ischemia and reperfusion phenomena, the effects of different drugs, surgical interventions, etc. The model introduces an advantage over the classical models which use crystalloid solutions as perfusate, because parabiotic circulation mimics heart surgery with extracorporeal circulation.

Analysis of Variance↗
PubMed2000

Mitral valve repair with a malleable bovine pericardium ring.

OBJECTIVE: To describe a surgical procedure utilizing a malleable bovine pericardium ring in mitral valve repair and clinical and Doppler echocardiographic results. METHODS: Thirty-two (25 female and 7 male) patients, aged between 9 and 66 (M=36.4+/-17.2) years, were studied over a 16-month period, with 100% follow-up. In 23 (72%) of the patients, the mitral approach was the only one applied; 9 patients underwent associated operations. The technique applied consisted of measuring the perimeter of the anterior leaflet and implanting, according to this measurement, a flexible bovine pericardium prosthesis for reinforcement and conformation of the posterior mitral annulus, reducing it to the perimeter of the anterior leaflet with adjustment of the valve apparatus. RESULTS: The patient survival ratio was 93.8%, with 2 (6.2%) fatal outcomes, one from unknown causes, the other due to left ventricular failure. Only one reoperation was performed. On Doppler echocardiography, 88% of the patients had functional recovery of the mitral valve (50% without and 38% with mild insufficiency and no hemodynamic repercussions). Of four (12%) of the remaining patients, 6% had moderate and 6% had accented insufficiency. Twenty-eight percent of class II patients and 72% of class III patients passed into classes I (65%), II (32%), and III (3%), according to NYHA classification criteria. CONCLUSION: Being flexible, the bovine pericardium ring fit perfectly into the valve annulus, taking into account its geometry and contractility. Valve repair was shown to be reproducible, demonstrating significant advantages during patient evolution, which did not require anticoagulation measures.

Adolescent↗
PubMed1999

Invasive hemodynamic monitoring in the postoperative period of cardiac surgery.

OBJECTIVE: To assess the hemodynamic profile of cardiac surgery patients with circulatory instability in the early postoperative period (POP). METHODS: Over a two-year period, 306 patients underwent cardiac surgery. Thirty had hemodynamic instability in the early POP and were monitored with the Swan-Ganz catheter. The following parameters were evaluated: cardiac index (CI), systemic and pulmonary vascular resistance, pulmonary shunt, central venous pressure (CVP), pulmonary capillary wedge pressure (PCWP), oxygen delivery and consumption, use of vaso-active drugs and of circulatory support. RESULTS: Twenty patients had low cardiac index (CI), and, 10 had normal or high CI. Systemic vascular resistance was decreased in 11 patients. There was no correlation between oxygen delivery (DO2) and consumption (VO2), p = 0.42, and no correlation between CVP and PCWP, p = 0.065. Pulmonary vascular resistance was decreased in 15 patients and the pulmonary shunt was increased in 19. Two patients with CI < 2 L/min/m2 received circulatory support. CONCLUSION: Patients in the POP of cardiac surgery frequently have a mixed shock due to the systemic inflammatory response syndrome (SIRS). Therefore, invasive hemodynamic monitoring is useful in handling blood volume, choice of vasoactive drugs, and indication for circulatory support.

Cardiovascular Surgical Procedures↗
PubMed1998

[High output heart failure due to coronary fistula].

A 45 year-old woman complaining of heart failure symptoms (New York Heart Association--class III) and a non typical thoracic pain was submitted to a transthoracic echocardiogram which showed a very dilated coronary artery and a fistula to the right atrium. The angiograms confirmed the same findings. She underwent open heart surgery which confirmed the diagnosis. Fistula ligation was then undertaken. She remains symptom-free three years after the operation.

Arteriovenous Fistula↗
PubMed1997

[Use of a thin retrocardiac drain after open heart surgery. Description of the technique].

PURPOSE: To describe a technique with a thin drainage system placed behind the heart, avoiding reoperation caused by tamponade due to pericardial effusion in patients who undergo open heart surgery. METHODS: We studied 59 patients, average age of 50 years. Twenty-six (44%) patients had undergone CABG, 25 (42%) valvar procedures and 8 (14%) different procedures. The control group were 20 patients, average age 44 years. Nine (45%) underwent CABG, 6 (30%) valvar procedures and 5 (25%) other procedures. Every patient was submitted to echocardiographic study to verify presence of pericardial effusion after operation. RESULTS: There was one patient with pericardial effusion with 8mm in the study group. Six patients showed pericardial effusion in the control group. The control group had mean drainage flow of 320 +/- 110ml and average permanence time was 45 +/- 10h. The study group had mean drainage flow of 410 +/- 122ml, the average permanence time was 46 +/- 10h. There was statistic difference between both groups when we compared the frequency of pericardial effusion. CONCLUSION: This drainage system reduces pericardial effusion comparing with the literature and causes little discomfort to the patient. The fixed rule to remove the drains did not present more discomfort to the patient and there were no complications related to its permanence.

Adult↗
PubMed1996

-Rate-responsive pacemaker with an unexpected chronotropic response-.

The pacemaker with rate-responsiveness was a great advance in cardiac stimulation, however, the choice of the best biosensor is still object of research. A 35 year-old woman with a responsive pacemaker implanted due to a complete heart block after interventricular septal defect surgical correction was admitted. The pacemaker showed improper cronothropic response with high frequency due to biosensing malfunction. Malfunction related to muscle stimulation in the generator pocket and a high response rate. A palliative procedure was made until the end of pregnancy, by reducing the sensitivity of biosensing.

Adult↗