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Biomedical subjects

M V Santana

Publications and source records attributed to M V Santana.

10 recordsLinked to original sources
PubMed2001

Deterministic variability and stability in detuned bimanual rhythmic coordination.

We examined the effects of crossing different degrees of cooperation and competition on inphase and antiphase 1:1 frequency locked coordination of left- and right-hand-oscillated pendulums. Degree of cooperation was manipulated through the joint frequency of oscillation specified by a metronome (the higher the frequency, the weaker the cooperation), and degree of competition by length (and, therefore, preferred frequency) differences between the two pendulums (the greater the difference, the stronger the competition). Increasing competition was accompanied by either decreasing cooperation (for six participants) or increasing cooperation (for six different participants). On each trial, a participant attempted to produce a steady-state phase relation phi for a given combination of competition and cooperation. Numerical simulations of the extended Haken-Kelso-Bunz (HKB) equation were used to predict (a) the patterns of shift in phi from either 0 or pi radians due to the different competition-cooperation relations and (b) the patterns of variability in phi. It was expected that the HKB equation would be successful in respect to (a), which it was, but not in respect to (b). The observed failure to confirm (b) was expected from the variability due to the different nonharmonic dynamics of the component oscillators, a source of variability not included in the HKB equation. The experimental results together with simulations and analyses of the phase-plane trajectories of the component oscillators suggest the operation of deterministic in addition to stochastic variability in the phase relation of contralateral limbs.

Adult↗
PubMed2001

New percutaneous techniques for perforating the pulmonary valve in pulmonary atresia with intact ventricular septum.

We report new percutaneous techniques for perforating the pulmonary valve in pulmonary atresia with intact ventricular septum, in 3 newborns who had this birth defect. There was mild to moderate hypoplastic right ventricle, a patent infundibulum, and no coronary-cavitary communications. We succeeded in all cases, and no complications related to the procedure occurred. The new coaxial radiofrequency system was easy to handle, which simplified the procedure. Two patients required an additional source of pulmonary flow (Blalock-Taussig shunt) in the first week after catheterization. All patients had a satisfactory short-term clinical evolution and will undergo recatheterization within 1 year to define the next therapeutic strategy. We conclude that this technique may be safely and efficiently performed, especially when the new coaxial radiofrequency system is used, and it may become the initial treatment of choice in select neonates with pulmonary atresia and intact ventricular septum.

Catheter Ablation↗
PubMed1998

New approach in partial cavopulmonary connection.

The development of pulmonary arteriovenous fistulas after bidirectional cavopulmonary operations, such as the bidirectional Glenn shunt and Kawashima's procedure, has raised concern. Development of these fistulas, which are more frequent than initially thought, can represent a limiting factor in the late outcome of these patients and may even limit the indication for these types of surgery. Whether the fistulas can be reversed by transforming the surgical procedures has yet to be established. In the hope of avoiding this kind of complication, thought to be caused by the lack of passage of a hypothetical hepatic factor through the pulmonary circulation, we have developed an inverted type of bidirectional cavopulmonary connection in which the blood coming from the liver perfuses immediately both lungs. This is made possible by shunting via an intra-atrial tunnel the blood from the superior caval vein directly to the left atrium, and the blood from the inferior caval vein to the right branch of the pulmonary trunk (keeping its bifurcation intact). We describe findings in two patients undergoing successful surgery with this technique. Serial follow-up with contrast echocardiography did not show evidence of arteriovenous pulmonary fistulas. Despite our numbers being small, and the time of follow-up being limited, we believe that it is important to document these and similar cases.

Angiography↗
PubMed1998

[Initial experience in percutaneous closure of interatrial communication with the amplatzer device].

PURPOSE: To evaluate our initial experience with percutaneous closure of secundum type atrial septal defects (ASD) with the Amplatzer septal occluder. METHODS: Seven patients underwent occlusion by anterograde approach, under general anesthesia and transesophageal echocardiography (TEE) guidance. One child had 2 ASD and a patent ductus arteriosus (PDA). The ASD size ranged from 8.7 to 20 mm as measured by TEE. A transthoracic echocardiogram was performed in the morning after the procedure. RESULTS: Eight devices were successfully implanted in 7 patients and the PDA was occluded with a Gianturco coil at the same session. In this patient, there was an episode of supraventricular tachycardia during the occlusion of one ASD which was reverted with adenosin. All patients were discharged the day after, with complete occlusion of all defects. CONCLUSION: The procedure is safe, effective and versatile. It can be applied as an initial alternative to the treatment of selected patients with ASD.

Adolescent↗
PubMed1998

[Overall experience with percutaneous occlusion of patent ductus arteriosus].

PURPOSE: To evaluate the overall experience of our institution with percutaneous occlusion of the patent ductus arteriosus. METHODS: Since December/92, 150 patients underwent 178 procedures (85-Rashkind technique; 87-Gianturco coils; 6-Duct Occlud). Median age was 6.5 years (1 to 57). Mean minimum ductal diameter was 3.05 +/- 1.24 mm (1 to 8). Clinical and echocardiographic evaluations were performed periodically. RESULTS: Adequate implantation was achieved in 143 (95.3%) patients. Prevalence of immediate residual shunting was 52.1%, falling to 15.9% during follow-up. This figure decreased to 5.2% after new additional procedures. Umbrella and coil embolization occurred in 1 and 12 procedures, respectively. Hemolysis and mild stenosis of left pulmonary artery were observed in one patient each. There was no mortality. CONCLUSION: This therapeutic modality is safe and efficacious with good follow-up results.

Child, Preschool↗
PubMed1996

Selective perception by dynamic touch.

Perceiving the length of a rod by dynamic touch is tied to the inertia tensor Iij, a quantification of its resistance to rotational acceleration. Perception of the portion extending in front of the grasp has previously been ascribed to decomposing one component of Iij by attention. The tensorial nature of dynamic touch suggests that this ability must be anchored wholly in the tensor. Three experiments show that perceived partial length is a function of two components of the tensor, one tied primarily to magnitude and the other tied primarily to direction, whereas perceived whole length is a function of a magnitude component alone. Dynamic touch is characterized in terms of a haptic perceptual instrument that softly assembles to exploit Iij differently depending on the intention, producing 1:1 maps that are appropriately scaled for each intention.

Adult↗
PubMed1995

[Pulmonary atresia with intact ventricular septum. Valvar perforation by radiofrequency].

Six days old neonate with pulmonary atresia and intact ventricular septum is reported in which a communication was established between the right ventricle and the pulmonary artery. The membraneous atresia was perforated with a special radiofrequency catheter 2F connected to a Hat 200S radiofrequency generator (Osypka). The energy necessary to perforation was 15W. After perforation of the atresia, balloon dilation was performed (balloon diameter: 2, 3, 4mm of coronary angioplasty and 5, 8mm Penta Medi-tech). The valve was completely opened giving the continuity between right ventricle and pulmonary artery.

Angiography↗
PubMedDate not supplied

[The percutaneous closure of patent ductus arteriosus with the Rashkind technic. The initial experience of the Instituto Dante Pazzanese de Cardiologia, São Paulo, Brazil].

The authors report their experience with the percutaneous closure of the patent ductus arteriosus with the Rashkind technique. They performed 42 procedures with a success of 97.6% and one embolization episode. The mean age was 8.7 +/- 6.7 years, the mean weight was 25.0 +/- 15.8 Kg and the minimum diameter of the ductus was 4.0 +/- 1.3 mm. The immediate overall prevalence of residual shunt was 48.8% falling to 21% in a mean follow-up of 17 +/- 13 months in 29 cases. Two patients underwent late reocclusion: one with a new umbrella and the other with a coil. Another patient had an immediate severe residual shunt and it was reoccluded in the same procedure with a coil. The anatomical type and minimum internal diameter of the ductus, age and weight, size of the umbrella and the rotation of the umbrella were not predictors of residual shunt. There were no deaths, hemolysis, endarteritis or fracture of the umbrella's arms. One patient remained with a slight gradient in the left pulmonary artery. The authors conclude that the Rashkind technique is safe and efficient and has good long term results. It should be considered as the first line therapeutic modality in the treatment of selected patients with persistent ductus arteriosus.

Academies and Institutes↗