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Intraaortic Balloon pump (IABP)
This is a simpler mechanical circulatory device used to provide temporary cardiac assistance. It is much less complicated than a total heart replacement. The material of choice is polyurethane.
Percutaneous Transluminal Coronary Angiplasty (PTCA)
Coronary-artery bypass surgery is an effective means of myocardial revascularisation. PTCA is less invasive technique for the treatment of obstructive coronary-artery disease, is also safe and effective method. PTCA utilizes a special balloon dialation catheter introduced through a peripheral artery and directed across the obstructing plaque in the coronary artery to relieve the obstruction. Dilating catheters have a fixed guide wire at the tip are made p of PVC or polyethylene, it has a central lumen through which a movable guide wire is used.
Vascular Grafts
Patients undergoing coronary revascularisation may not have suitable autologous vessels for artery grafting and may need vascular prostheses. The highly porous PTFE Vascular grafts 4mm in diameter have been used in coronary-artery bypass surgery and 6mm dia. are used in artificial kidney patients. Polyester is used as alternative material for the same purpose.
Heart valves and pacemakers
Diseased aortic and mitral valves were first replaced with mechanical ball and cage prostheses. The artificial heart valve contains the following components silicone ball of 17mm dia, silicone soft ball seating, PTFE stiffener and polyamide6 fiber net. The housings of pacemakers contain epoxy resins and silicone rubbers have been used in electrical conduits. Seamless trileaflet valves have been made of polyurethane.
Extracorporal Heart-Lung Machines (Oxygenators)
In open heart operations , the heart is temporarily replaced with an extracorporeal heart–lung machine. In the bubble type oxygenator, blood is directly exposed to oxygen . The oxygenating section is made up of soft PVC film or rigid polycarbonate. In the membrane type oxygenator, the blood is oxygenated through a polymeric membrane - propylene, silicone rubber, polysulfone or PTFE. A safe and effective microporous polypropylene hollow fiber oxygenator has become popular.
Renal Applications
Artificial kidneys
Artificial kidneys often referred to as hemodialysis units, remove waste products from the blood with polymeric semi permeable membrane. Hemodialysis and hemofilteration depend on membrane technique. Polymeric materials used as dialysis membranes are cellulose acetate, polymethyl methacrylate, polyacrylonitrile, polysulfone and ethylene-vinyl acetate copolymer. They are used in the form hollow fibers or integrated plates.
Continuous Ambulatory Peritoneal Dialysis (CAPD)
CAPD keeps the dialysate a longer time in the peritoneum. Which uses a silicone rubber tube and PVC plastic bag for the dialysate.
(to be cont’d)
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