Browsing by Author "Valiathan, MS"

Now showing 1 - 9 of 9
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    Biomaterials: An overview
    (NATIONAL MEDICAL JOURNAL OF INDIA, 1999) Valiathan, MS; Krishnan, VK
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    Cerium levels are elevated in the serum of patients with endomyocardial fibrosis (EMF)
    (BIOLOGICAL TRACE ELEMENT RESEARCH, 1997)
    The geochemical hypothesis on endomyocardial fibrosis (EMF) links causation of the disease to increased levels of cerium in the heart. Since cardiac tissues are not easily accessible from patients, we explored whether cerium can be detected in the serum using neutron activation analysis (NAA). Cerium levels in serum of EMF patients were significantly elevated (p < 0.05) compared to controls.
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    Chitra heart valve: Results of a multicenter clinical study
    (JOURNAL OF HEART VALVE DISEASE, 2001)
    Background and aim of the study: The Chitra tilting disc valve was developed in India to meet the need for a low-cost cardiac valve. The valve has an integrally machined cobalt-based alloy cage, an ultrahigh molecular-weight polyethylene disc, and a polyester suture ring. An important feature of this valve is its soft closing sound, by virtue of a plastic occluder.Methods: Between December 1990 and January 1995, 306 patients underwent isolated aortic MR, n = 101) or mitral valve replacement (MVR, n = 205) at six institutions in India. The early mortality rate was 6.9% (seven after AVR; 14 after MVR). A total of 285 survivors was followed up until September 1998; total follow up was 1212 patient-years (pt-yr) (AVR, 445 pt-yr; MVR, 767 pt-yr).Results: There were 52 late deaths (4.3%/pt-yr; AVR 2.2%/pt-yr; MVR 5.5%/pt-yr). Thirty-five deaths were valve-related (23 were due to unknown causes). One AVR patient (0.2%/pt-yr) and 12 MVR patients (1.6%/pt-yr) developed valve thrombosis, and embolic episodes occurred in 25 patients (seven after AVR, 1.6%/pt-yr; 18 after MVR, 2.4%/pt-yr). Bleeding events and infectious endocarditis occurred infrequently (AVR 0.9 and 0.7%/pt-yr; MVR 0.4 and 0.5%/pt-yr, respectively). There was no incidence of paravalvular leak or structural dysfunction of the valve. Actuarial survival rates at seven. years were 82.4 +/- 4.0% for AVR and 65.2 +/- 5.0% for MVR. During the same interval, thrombus-free and embolism-free survival after AVR and MVR occurred in 98.9 +/- 1.1% and 94.1 +/- 1.9%, and 92.3 +/- 2.8% and 82.1 +/- 5.7% of patients, respectively. Freedom from all valve-related mortality and morbidity at seven years was 81.5 +/- 4.1% after AVR, and 64.2 +/- 5.1% after MVR.Conclusion: The Chitra valve appears to be safe and to have performance comparable with that of other currently used tilting disc valves. This valve costs substantially less than other valves, and is therefore within reach of a larger subset of Indian patients.
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    Country Profile: India
    (Lancet, 1998) Nath, I; Reddy, KS; Dinshaw, KA; Bhisey, AN; Krishnaswami, K; Bhan, MK; Ganguly, NK; Kaur, S; Panda, SK; Jameel, S; Srinivasan, K; Thankappan, KR; Valiathan, MS
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    Development of the chitra tilting disc heart valve prosthesis
    (JOURNAL OF HEART VALVE DISEASE, 1996) Bhuvaneshwar, GS; Muraleedharan, CV; Vijayan, GA; Kumar, RS; Valiathan, MS
    Background nun aims of the study: The high prevalence of rheumatic valvular disease in the young population and the high cost of imports necessitated the development of an Indian valve. The development of a tilting disc prosthesis was successfully concluded in February 1995, when the third model completed its clinical trial. The tilting disc valve has an integrally machined cobalt alloy cage, an ultra high molecular weight polyethylene disc and a polyester suture ring. The choice of design was based on its superior hydrodynamics and the age distribution of patients, the majority of whom were below 30 years. The polymer-metal combination was selected for its extremely low wear rate and proven durability in the human body. Materials and methods: The hydrodynamic performance was tested under steady and pulsatile flow conditions. The accelerated durability of nine test valves was evaluated at 800-840 cycles/min for over 350 million cycles each. Size 23mm valves mere implanted in the mitral position of five sheep. In a clinical trial, 306 patients with isolated mitral or aortic valve replacements were followed up for a total of 371 patient years (mean 1.37 years and range 0-4 years). Results: The hydrodynamic performance was comparable to that of proven clinical models. The accelerated testing indicated lifetimes in excess of 50 years and the animal trials showed the valve to be safe. In the clinical trial, there was no incidence of structural failure or paravalvular leak. The linearized rate of late thromboembolism was 6.2 %/patient-year (pty), anticoagulant related hemorrhage 0.54 %/pty and infective endocarditis 0.54 %/pty. At two years, the total actuarial survival was 89.5%. The higher incidence of thromboembolism and the very low incidence of anticoagulant related hemorrhage illustrate the difficulty in the management of anticoagulant therapy in a developing country, while the low incidence of endocarditis reflects their greater resistance to infection. Conclusion: These data clearly showed the valve to be safe and comparable to other similar valves in clinical use.
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    Effect of rare earth elements on growth and nutrition of coconut palm and root competition for these elements between the palm and Calotropis gigantea
    (JOURNAL OF PLANT NUTRITION, 2000) Wahid, PA; Valiathan, MS; Kamalam, NV; Eapen, JT; Vijayalakshmi, S; Prabhu, RK; Mahalingam, TR
    Absorption of rare earth elements (REEs) namely lanthanum (La), cerium (Ce), praseodymium (Pr), and neodymium (Nd) by coconut, competition between coconut and Calotropis gigantea L. for these elements in mixed culture and the effects of the REEs on growth and nutrition of the palm were studied in a pot culture. Ata low rate of application, REEs promoted root growth in coconut, but at a higher level, absorption of phosphorus (P) and zinc (Zn) by the palm was reduced significantly. Absorption of REEs by the palm tended to increase with increasing application rates, but the increases were not statistically significant. Although Calostropis gigantea accumulated more REEs per unit dry matter than coconut, it failed to compete effectively for REEs in mixed culture with coconut. However, in mixed culture, coconut depressed the absorption of REEs by Calostropis gigantea.
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    Levels of cerium in the tissues of rats fed a magnesium-restricted and cerium-adulterated diet
    (BULLETIN OF ENVIRONMENTAL CONTAMINATION AND TOXICOLOGY, 1996)
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    Materials for Chitra heart valve prosthesis - A review
    (METALS MATERIALS AND PROCESSES, 1995) Muraleedharan, CV; Bhuvaneshwar, GS; Valiathan, MS
    Materials used in an artificial heart valve, for that matter any implant device, has to be compatible to the biological environment apart from being suitable in terms of physical and engineering properties. This limits the spectrum of materials available for such applications. The course of development of Chitra Heart Valve Prosthesis at Sree Chitra Tirunal institute for Medical Sciences and Technology, Trivandrum was a fascinating study of various aspects of material science, processing and evaluation. A review of different materials tried at various stages of valve development, evaluation of these materials and problems encountered are outlined in this paper.
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    Structural studies on bovine bioprosthetic tissues and their in vivo calcification: Prevention via drug delivery
    (BIOMATERIALS, 1996)
    Cardiovascular calcification, the formation of calcium phosphate deposits in cardiovascular tissue, is a common end-stage phenomenon affecting a wide variety of bioprostheses. To study the process of calcification in tissue prosthetics, glutaraldehyde-treated bovine pericardium, dura mater and fascialata were implanted subcutaneously in rats and retrieved 21 days later and thereby morphological findings were correlated with biochemically determined levels of calcium. Transmission electron microscopy showed that calcification primarily involved the surface of collagen fibrils and the interfibrillar spaces. The deposition of calcium was higher with dura and fascia prostheses compared to pericardium. However, the release of Fe3+ ions from chitosan matrix had substantially inhibited the deposits of calcium in all implanted tissues. It seems that the structural and anatomical features of the tissue is one of the important factors for tissue-associated calcification. It is also confirmed that glutaraldehyde-preserved pericardium is the most suitable material for the development of cardiac prosthesis, with an appropriate drug combination therapy for prevention of pathological calcification.