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Biomedical subjects

M Marcolongo

Publications and source records attributed to M Marcolongo.

11 recordsLinked to original sources
PubMed2001

Comparison of defibrillation thresholds using monodirectional electrical vector versus bidirectional electrical vector.

BACKGROUND: Currently, two main lead configurations are used for implantable cardioverter-defibrillators (ICD). One generates a monodirectional electrical vector by using the can surface as an active part (hot can) together with a right ventricular defibrillation coil. The other one (TRIAD) produces a bidirectional electrical vector by adding a proximal defibrillation electrode on the same lead. The purpose of this prospective study was to determine whether there is a difference between these configurations in terms of the acute defibrillation threshold (DFT). The secondary objective was to evaluate the possible sequential effect of successive arrhythmia induction and defibrillation shocks on the final DFT value. METHODS: In 44 patients (37 males, 7 females, mean age 59.18 +/- 12.05 years; mean ejection fraction 35.21 +/- 11.69%), a Hot Can Ventak family ICD (Guidant, St. Paul, MN, USA) was implanted in a left pectoral pocket. During the implant procedure, step-down to failure DFT testing was performed twice in each patient using the two different above-mentioned configurations: the bidirectional and the monodirectional. The first configuration to be tested was determined by a 1:1 randomization by center. RESULTS: The step-down DFT protocol was followed in 35 patients. The average DFT was 8.6 +/- 4.0 J for TRIAD and 10.4 +/- 4.3 J for the monodirectional (p = 0.009) lead configuration; this represents a 16.3% decrease in the DFT using a bidirectional configuration. Furthermore, no relationship between the final DFT and the number of ventricular fibrillation inductions and shocks received was observed, confirming the secondary objective. CONCLUSIONS: Compared to the monodirectional electrical vector, the bidirectional electrical vector is clearly more beneficial for the patient.

Adult↗
PubMed1998

Bioactive glass fiber/polymeric composites bond to bone tissue.

Bioactive glass fibers were investigated for use as a fixation vehicle between a low modulus, polymeric composite and bone tissue. In an initial pilot study, bioactive glass fiber/polysulfone composites and all-polysulfone control rods were implanted into the rabbit tibia; the study was subsequently expanded with implantation into the rabbit femur. Bone tissue exhibited direct contact with the glass fibers and adjacent polymer matrix and displayed a mechanical bond between the composite and bone tissue after six weeks implantation. Interfacial bond strengths after six weeks implantation averaged 12.4 MPa, significantly higher than those of the all-polymer controls. Failure sites for the composite at six weeks generally occurred in the bone tissue or composite, whereas the failure site for the polymer implants occurred exclusively at the implant/tissue interface. The bioactive glass fiber/polysulfone composite achieved fixation to bone tissue through a triple mechanism: a bond to the bioactive glass fiber, mechanical interlocking between the tissue and glass fibers, and close apposition and possible chemical bond between the portions of the polymer and bone tissue. This last mechanism resulted from an overspill of bioactivity reactions from the fibers onto the surface of the surrounding polymer which we call the "halo" effect.

Animals↗
PubMed1997

Surface reaction layer formation in vitro on a bioactive glass fiber/polymeric composite.

In order to provide a fixation vehicle between a polymeric composite femoral hip prosthesis and bone tissue, we fabricated bioactive glass fibers. The glass fibers had a tensile strength of 596 MPa, 14 times that of bulk bioactive glass. After immersion in protein-free simulated body fluid for 10 days, we observed the development of a calcium phosphate layer (specifically, partially crystallized, calcium-deficient carbonated hydroxyapatite) on the surface of the glass fibers. The stages of the surface reaction layer formation were similar to those of 45S5 bioactive glass although the kinetics of the reaction layer formation were slower. We combined the bioactive glass fibers with a polymeric matrix to form a fiber-reinforced composite material and observed the formation of a calcium phosphate layer on the surface of the glass fibers within the composite material after immersion in both protein-free and protein-containing simulated body fluids. The rate of reaction layer formation was reduced in the presence of proteins. In both protein-free and protein-containing solutions, a "halo" of bioactivity reactions was observed on the surface of the polymer in regions surrounding the glass fibers. Our results suggest these glass fibers and glass fiber composites will exhibit bioactivity reactions in vivo.

Biocompatible Materials↗
PubMed1989

[Effects of simvastatin on plasma levels of lipids, lipoproteins and apolipoproteins in primary hypercholesterolemia].

To evaluate the effectiveness, tolerance and safety of simvastatin (MK 733), a new HMG-CoA reductase inhibitor, a 28-week, single blind study with placebo was carried out on 10 patients suffering from primary hypercholesterolaemia. All patients followed the AHA Phase 1 or Phase 2 diet and underwent active treatment for 24 weeks with increasing doses of simvastatin from 10 to 40 mg in a single evening administration. A reduction in plasma levels of total cholesterol (-29%, p less than 0.001 and -41%, p less than 0.001), LDL cholesterol (-35%, p less than 0.001 and -49%, p less than 0.001), VLDL cholesterol (-9%, ns and -38%, ns), Apo-B (-27%, p less than 0.005 and -37%, p less than 0.001), Apo-A2 (-3%, ns and -3%, ns), and triglycerides (+2%, ns and -10%, ns), was obtained in the VIth and XXIVth week. There was also an increase in HDL cholesterol (+4%, ns and +17%, p less than 0.05), HDL2 subfractions (+9%, p less than 0.05 and +36%, p less than 0.05), HDL3 (+3%, ns and +11%, ns) and Apo-A1 (+7%, ns and +4%, ns). In all patients, simvastatin was generally tolerated and there were no clinical, laboratory or ophthalmological side-effects related to the drug. If long-term studies confirm its safety, simvastatin will offer excellent prospects for the prevention of ischaemic cardiopathy.

Anticholesteremic Agents↗
PubMed1986

[Bicameral stimulation in a case of corrected transposition of the great vessels].

A patient with Corrected Transposition of the Great Arteries (CTGA), mild incompetence of left A-V valve, complete atrioventricular block without associated anatomic lesions, in whom a bicameral permanent pace maker has been implanted, is described. The procedure of implantation did not present any particular problem; the stability of the electrocatheters was good. The exercise tolerance with DDD mode stimulation was normal and definitively better as compared to that achieved with ventricular stimulation at progressively higher stimulation frequency. The patient is now well and attending a normal physical activity.

Adult↗
PubMed1979

[The electrocardiogram and arterial hypertension in primary hyperparathyroidism].

Cardiovascular conditions of 27 patients with primary hyperparathyroidism have been examinated. Hypertension has been found to be the only alteration significantly present (33,33% of patients), while heart disease are uncommon. Hypertension is often present without concomitant disease of the kidney. Blood pressure became normal in only one case over nine (11,11%) after parathyroidectomy.

Adult↗