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Biomedical subjects

J R Monties

Publications and source records attributed to J R Monties.

At least 19 recordsLinked to original sources
PubMed1999

Multiple valve replacement increases the risk of reoperation for structural degeneration of bioprostheses.

BACKGROUND AND AIM OF THE STUDY: The study aim was to analyze the results of reoperations for structural degeneration of bioprostheses, and to define a high-risk population for reoperative procedures. METHODS: A series of 524 consecutive patients who had undergone a first reoperative replacement for a failed bioprosthesis between 1978 and 1998 was reviewed retrospectively. The reoperative procedure comprised 363 single valve replacements, and 161 multiple valve replacements. During the original procedure, 648 bioprostheses had been implanted in the mitral (n = 403), aortic (n = 220) and tricuspid (n = 25) positions. RESULTS: The mean interval between the original procedure and reoperation was 8.8 +/- 3.3 years. Tissue valve failure was revealed by recurrence of cardiac insufficiency in 70% of cases. The overall early mortality rate was 8%, but early mortality rates for elective single mitral and aortic reoperative valve replacements were only 3.9% and 4%, respectively. Early mortality following reoperation for single and multiple valve replacement was 6.0% and 12.4% respectively (p = 0.02). Other significant multivariable predictors for early mortality were old age (p = 0.003), NYHA functional class (p = 0.007), presence of ascites (p = 0.02) and reoperation performed before 1988 (p = 0.013). CONCLUSIONS: The risk of reoperation for structural degeneration of bioprostheses is acceptable for elective single reoperative valve replacement as opposed to multiple reoperative valve replacement. This may limit the use of bioprostheses during the original procedure when multiple valve replacement is required.

Bioprosthesis↗
PubMed1998

Dynamic aortomyoplasty: clinical experience and thoracoscopic surgery feasibility study.

BACKGROUND: Surgical procedures using the latissimus dorsi (LD) muscle to assist chronic heart failure inflict major trauma on severely sick patients. A less invasive approach may prove beneficial. The aim of this article is to review our clinical and experimental approaches of dynamic aortomyoplasty (AMP) and emphasize the necessity to reorient surgical technique towards new directions and a less invasive thoracoscopic approach. MATERIALS AND METHODS: A clinical pilot study on dynamic descending AMP started in June 1995 and included four patients. Two of them could benefit from LD counterpulsation, surviving 6 months and 18 months. Following this clinical experience, we investigated, on an animal model, minimally invasive thoracoscopic surgery for this procedure. Twelve goats underwent endoscopic LD harvest and video-assisted aortic wrap, and were studied after surgical recovery from an anatomical and functional standpoint. RESULTS: Clinical AMP using open techniques provided extraaortic counterpulsation in NYHA Class IV patients contraindicated for other surgical therapies. However, surgical technique and strategy needed improvements for optimal cardiac assistance and better patient outcome. Minimally invasive thoracoscopic surgery was feasible and reproducible in goats, achieving improved anatomy and physiology as compared to the open technique in humans. When appropriate the wrapping technique and stimulation protocol were used, an optimal counterpulsation was demonstrated. We concluded that thoracoscopic AMP may provide a minimally invasive approach to cardiac assistance and thus, a new surgical option for patients presenting with chronic heart failure.

Animals↗
PubMed1997

Aortic valve or root replacement with cryopreserved homograft for active infectious endocarditis.

Active aortic endocarditis is a serious condition that carries a high mortality and morbidity. The aim of this study was to analyse results obtained from 24 patients who underwent aortic valve or root replacement with cryopreserved homograft for aortic endocarditis. Eleven patients had native valve endocarditis, and 13 had prosthetic valve endocarditis. The mean age was 47.7 years: there were seven women and 17 men. Causative organisms were staphylococci (12), streptococci (four), serratia (one), candida (one), pneumococci (one), while no organisms were isolated in the remaining five patients. Complete reconstruction of the aortic annulus with homograft conduits was necessary in 20 patients (six total root and 14 mini-root). Infracoronary homograft aortic valve replacement was performed in the remaining patients. One patient died 1 day after the operation from ventricular failure, and two others died after 4 and 6 months as a result of arrhythmia. One patient died of recurrent endocarditis 1 year after surgery. The actuarial survival rate at 3 years was 83.4%. All survivors are symptom-free, with no evidence of recurrent endocarditis. Doppler echocardiography showed minimal aortic regurgitation in four patients.

Adult↗
PubMed1997

Physico-chemistry and cytotoxicity of ceramics: part I: characterization of ceramic powders.

The morphology of Al2O3, ZrO2/Y2O3, AIN, B4C, BN, SiC, Si3N4, TiB2, TiC, TiN ceramic, graphite and diamond powders has been studied by scanning electron microscopy (SEM) and the specific area of each powder was determined with the BET method. X-ray diffraction (XRD) investigations have been carried out in order to evaluate the crystallinity and determine the constitutive phases. The chemical composition was assessed by classical chemical analyses and by X-ray microprobe; some powders were studied by the laser micro-Raman technique. Correlations have been established between all these results.

Journal Article↗
PubMed1997

Bone mineral density in patients given oral vitamin K antagonists.

BACKGROUND: Divergent results have been obtained in studies of bone mineral density in patients under oral vitamin K antagonists. OBJECTIVE: To gather prospective data on bone mineral density and bone metabolism in 70 aortic valve replacement patients. STUDY DESIGN: 49 patients who had been under oral vitamin K antagonists for at least one year after implantation of a mechanical aortic valve were compared with 21 recipients of a tissue aortic valve that did not require anticoagulant therapy. The following investigations were done in all patients: (1) dual-energy X-ray absorptiometry measurement of bone mineral density at the lumbar spine and femoral neck; (2) roentgenograms of the spine and pelvis; (3) serum assays of calcium, phosphate, creatinine, alkaline phosphatase, osteocalcin, 25-OH-vitamin D3, and parathyroid hormone. RESULTS: The two groups were comparable regarding age and sex ratio. No differences were found in lumbar or femoral neck bone mineral density even after adjustment for age and sex. A trend toward an increase in bone mineral density at both sites with increasing duration of vitamin K antagonist therapy was demonstrated. The only bone turnover marker difference between the two groups was a significantly lower serum osteocalcin level in the group under vitamin K antagonist therapy (P < 0.0001). CONCLUSIONS: Long-term vitamin K antagonist therapy does not affect bone mineral density at the lumbar spine or femoral neck and also fails to modify bone turnover markers, with the exception of osteocalcin.

Administration, Oral↗
PubMed1996

Cora valveless pulsatile rotary pump: new design and control.

For decades, research for developing a totally implantable artificial ventricle has been carried on. For 4 to 5 years, two devices have been investigated clinically. For many years, we have studied a rotary (but not centrifugal) pump that furnishes pulsatile flow without a valve and does not need external venting or a compliance chamber. It is a hypocycloidal pump based on the principle of the Maillard-Wankel rotary compressor. Currently made of titanium, it is activated by an electrical brushless direct-current motor. The motor-pump unit is totally sealed and implantable, without noise or vibration. This pump was implanted as a left ventricular assist device in calves. The midterm experiments showed good hemodynamic function. The hemolysis was low, but serious problems were encountered: blood components collecting on the gear mechanism inside the rotor jammed the pump. We therefore redesigned the pump to seal the gear mechanism. We used a double system to seal the open end of the rotor cavity with components polished to superfine optical quality. In addition, we developed a control system based on the study of the predicted shape of the motor current. The new design is now underway. We hope to start chronic experiments again in a few months. If the problem of sealing the bearing could be solved, the Cora ventricle could be used as permanent totally implantable left ventricular assist device.

Animals↗
PubMed1996

Biological evaluation of mechanical circulatory support systems in calves.

Data from animal experiments with mechanical circulatory support systems (MCSS) performed in Groningen and Marseille over the past years were used to obtain normal values of hematological, coagulation, rheological and blood chemistry parameters in calves. These parameters were divided between two groups: a limited number of parameters necessary to assess biocompatibility properties of MCSS quickly and a more extensive number of parameters suitable for more detailed biological evaluation of blood pumps. All applied tests can be examined in calf blood as well as in human blood. Parameters were selected on clinical relevance and usefulness for standardization procedures. The obtained data were compared with normal values in human beings derived from the literature.

Animals↗
PubMed1994

Right-sided aortic arch: surgical treatment of an aneurysm arising from a Kommerell's diverticulum and extending to the descending thoracic aorta with an aberrant left subclavian artery.

The case of a 44-year-old black man who presented with severe dysphagia, cough and chest pain caused by a 12-cm aneurysm developing from a Kommerell's diverticulum at the origin of an aberrant retro-oesophageal left subclavian artery is reported. The aortic arch and descending thoracic aorta were right sided. Diagnosis was established before operation by computed tomography, magnetic resonance imaging and arteriography. The aneurysm extended a considerable distance down the descending aorta and therefore the risk of postoperative paraplegia was considered to be high. Accordingly selective arteriography was performed to locate the Adamkievicz's artery which arose only 2 cm below the end of the aneurysm. Resection grafting of the aneurysm including the upper third of the descending aorta via right thoractomy was performed. The patient made an uneventful recovery and was discharged 20 days later. This case appears to be the first successful operation for this pathology.

Adult↗
PubMed1993

TiN coating: surface characterization and haemocompatibility.

The left ventricular assist device under consideration is based on the principle of the Maillard-Wankel rotary pump. The construction materials must meet stringent requirements. Titanium nitride was chosen for its surface properties and graphite for its bulk characteristics. The purpose of this study was to characterize the chemical vapour deposition titanium nitride coating via morphology, roughness, crystallinity, chemical composition, to report and discuss the results of in vitro haemocompatibility tests (protein adsorption, platelet retention, haemolysis) and to discuss physico-chemical and biological results. This chemical vapour deposition titanium nitride coating is well tolerated by the blood despite its surface irregularities, and appears as a good candidate material after improvements.

Absorption↗
PubMed1993

Blood haemolysis by ceramics.

Ceramics are more and more frequently under consideration for construction of blood-contacting devices, i.e. cardiac valves or cardiac assist devices. This study evaluated the haemolysis eventually initiated in vitro by ceramic powders (Al2O3, ZrO2/Y2O3, AlN, B4C, BN, SiC, Si3 N4, TiB2, TiN, TiC), graphite and diamond. The chemical composition of the powders was studied by X-ray microprobe and various other methods, and BET specific areas were determined. The haemolysis was almost zero for all powders, except AlN which showed slight haemolysis and TiB2 which had high haemolytic power.

Aluminum↗
PubMed1993

Haemocompatibility of Ti6A14V alloy.

Ti6A14V alloy has been mainly used as a biomaterial in the orthopaedic field. The present study describes the surface state of the Ti6A14V material and evaluates its in vitro haemocompatibility in terms of protein adsorption, platelet retention and haemolysis. The behaviour of the Ti6A14V alloy towards albumin and fibrinogen was compared to that of a reference medical-grade elastomer. The platelet retention test gave better results than those achieved with the elastomer. The haemolysis percentage of the alloy was almost zero. These results indicate that the Ti6A14V alloy is well tolerated by blood.

Adsorption↗
PubMed1993

Diagnosis of prosthetic heart valve thrombosis. The respective values of transthoracic and transoesophageal Doppler echocardiography.

Early diagnosis of acute prosthetic thrombosis remains a challenge. In 20 patients with 23 thrombosed cardiac valves, we evaluated the respective value of transthoracic (TTE) and transoesophageal (TEE) Doppler echocardiography. According to the presence or absence of prosthetic obstruction by continuous-wave Doppler, prostheses were separated into two groups. Group 1 included nine thrombosed prostheses (8 mitral, 1 aortic) with severe obstruction. All patients presented with severe symptoms of heart failure. Transthoracic Doppler echocardiography allowed immediate diagnosis of prosthetic thrombosis, even in critically ill patients, showing (1) eccentric transprosthetic colour flow jets in all eight mitral prostheses, (2) severe obstruction on Doppler examination (mean gradient = 18 to 36 mmHg in eight mitral prostheses, and 69 mmHg in one aortic valve), and (3) direct echocardiographic evidence of thrombosis (i.e. thrombus or abnormal disc or leaflet motion) in four patients. All nine patients were immediately treated by surgery (n = 8) or fibrinolysis (n = 1) on the basis of TTE results only. TEE allowed better visualization of thrombus and restricted leaflet or disc motion, but had little influence on patient management. Group 2 included 14 thrombosed prostheses (10 mitral, 4 aortic) with mild or absent obstruction. In three patients with massive mitral prosthetic thrombosis, an associated minimal thrombosis of a prosthetic aortic valve was found at surgery, but was detected neither by TTE, nor by TEE. The 11 remaining patients with isolated partial mitral (n = 10) or aortic (n = 1) thrombosis. Clinical presentation was fever, cerebral embolism, or mild dyspnoea, but no heart failure. TTE was normal in all.(ABSTRACT TRUNCATED AT 250 WORDS)

Aortic Valve↗