Cardiovascular medical devices

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Information about Cardiovascular medical devices

Published on September 2, 2008

Author: muralicv


Cardiovascular Devices : Cardiovascular Devices Muraleedharan CV Division of Artificial Organs, Biomedical Technology Wing Sree Chitra Tirunal Institute for Medical Sciences & Technology Trivandrum – 695 012 Agenda : Agenda Heart and circulatory system Working of heart Devices for Rhythm management Septal defects & management Artificial heart valves Coronary heart disease management Congestive heart failure Cardiopulmonary bypass system Heart and circulatory system : Heart and circulatory system Transport system of the body Blood as the media Oxygen / CO2 Nutrients to cells Waste removal Heart acts as the pump Positive displacement pump Heart muscles – drive Rhythmic contraction and expansion of muscles controlled by electrical signals Blood vessels acts as the pathways – tubular structures Heart - anatomy : Heart - anatomy Has four chambers Two pumping chambers Four non return valves Two valves on either side Right side pumps through the lungs (pulmonary circulation) Left side pumps through the entire body (systemic circulation) Left heart & its valves are more susceptible to damage, since it works against the entire vascular resistance of systemic circulation Blood vessels : Blood vessels Arteries carry blood from the heart to various organs Transfer of oxygen, carbon dioxide and nutrients occur in the capillary network at various organs Veins collect the blood and returns to the heart for pumping again Blood flow controlled by the vessel resistances and pressure generated by the heart Circulatory system - revisited : Circulatory system - revisited LA and RA are the collection chambers LV and RV are the pumping chambers Two valves, at the inlet and outlet of the pumping chambers Tricuspid valve Pulmonary valve Mitral valve Aortic valve Working of heart : Working of heart The natural pacemaker of the heart is the Sinoatrial (SA) node The electrical impulse leaves the SA node and travels to the right and left atria, causing them to contract together The electrical impulse subsequently reaches Atrio ventricular Node (AV node) and travels through the Bundle of His where it rapidly spreads using Purkinje Fibers to the muscles of the Right and Left Ventricle, causing them to contract at the same time Electrical subsystem complications : Electrical subsystem complications When the natural conduction pathways does not perform correctly, or the natural pacing system fails, the heart does not beat at the appropriate rates In such cases, implantable pacemakers are used for regulating the cardiac rhythm Called ventricular resynchronization therapy Pacemakers : Pacemakers An electronic circuit senses the ECG and generates signals to resynchronize the heart rhythm. The heart rhythm is controlled to achieve the required heart rate; depending on the condition of the patient Provided with a battery (with typical 10 year life) and is totally implantable device Pacemaker : Pacemaker Antenna is used for external programming of the pacemaker subsequent to implantation Septal defects in heart : Septal defects in heart Atrial septal defect (ASD) relates to a communication between the two atria chambers giving rise to mixing of oxygenated and unoxygenated blood Ventricular septal defect (VSD) relates to a communication between the two ventricles. These congenital defects, can lead to growth retardation and in certain patients fatal consequences ASD VSD Septal defects - management : Septal defects - management Normally fabric patches made of Polyethylene Terephthalate (PET) and Poly tetra flouroethylene (PTFE) are employed to close these defects Currently, catheter based closure devices using shape memory alloys are being available to treat this abnormality The SMA alloys have properties to change its shape based on the temperature of the environment Catheter based ASD closure devices : Catheter based ASD closure devices ASD Closure device Heart valve defects : Heart valve defects The heart valves, normally due to certain diseases, fail to function as unidirectional check valves; they either become too leaky in the closed state (Regurgitation) or very narrow and offer resistance to blood flow in the open state (Stenosis) Mostly, rheumatic fever and associated complications cause valvular defects Many modes of management are feasible for valvular defects – depending on the state of the valve and the patient Heart valve defects - management : Heart valve defects - management Corrections : The state of the valve is improved, either using a catheter and balloon or using surgical intervention on valve using annulaoplasty rings Balloon expansion is employed in the case of stenosis Annularplasty rings are mostly for valve leaks Correction procedure cannot be performed in all cases Annularplasty ring Artificial heart valves : Tilting Disc Bileaflet Caged Ball Tissue Valve Artificial heart valves Artificial heart valves are devices used for replacing damaged or diseased natural valves of the heart. The natural valves are excised out and replacements are implanted Tissue valves Homorafts Xenografts Mechanical valves Caged ball Tilting disc Bileaflet Coronary heart disease : Coronary heart disease Coronary arteries supply blood to the heart muscles Plaque deposition in arteries – lesions, inflammation Narrowing and reduction in blood flow Causes ischemia , myocardial infarction (cardiac attack) Major killer disease in the nation & world Coronary heart disease - management : Coronary heart disease - management Open heart bypass surgery Plaque removal Plaque control by drug administration Revascularisation Angioplasty (PTCA) – catheter based Coronary Stenting – metal stent is deployed through a catheter Coronary artery bypass grafting : Coronary artery bypass grafting Patient’s own mammary artery or saphaneous veins are employed for grafting Synthetic grafts (tubes) developed till date are not very successful Researchers around the world are working to develop suitable small diameter synthetic grafts to replace coronary arteries Mammary artery grafting Saphaneous vein grafts Revascularization : Revascularization creation of channels in myocardium using Laser beams Laser myocardial revascularization techniques uses laser energy to create new myocardial channels and produce effects which lead to improved myocardial blood supply and reduction in angina. Revascularization using drugs and capillary promoting agents are also being tried Plaque removal : Plaque removal Catheter loaded with a diamond rotary blade 12,000 to 15,000 rpm rotation speed Debris generated may be collected using a collection system to eliminate the possibility of thrombus formation Yet, not very popular PTCA : PTCA Percutaneous Transluminal Coronary Angioplasty (PTCA), uses a balloon to open a clogged vessel The PTCA catheter is guided to the required site. When the balloon is inflated, this presses the plaque against the artery wall and opens up the lumen of the artery to achieve near normal blood flow Restenosis is the major failure mode Coronary Stents : Coronary Stents A type of wire mesh that fits within the artery. Inserted during the PTCA procedure When the balloon opens up to press the plaque against the artery wall, the stent opens up, too. Once the balloon is deflated and pulled out of the artery, the stent stays open and keeps the plaque in place Bare metal stents Drug eluting stents Grafts for large blood vessels : Grafts for large blood vessels When large diameter blood vessels (> 6 mm diameter) need to replaced, synthetic grafts are successfully employed Mainly two types Woven or knitted polyethylene terphthalate (PET) grafts Expanded poly tetra flouro ethylene (PTFE) grafts Congestive heart failure : Congestive heart failure Develops as a result of damage to the heart muscle Can occur following a heart attack or coronary artery disease Can also result from strain and pressure placed on the heart following years of untreated heart valve disease or high blood pressure Congestive heart failure - management : Congestive heart failure - management Cardiac support devices Intra aortic balloon pumps (IABP) Left ventricular assist devices (LVAD) Total artificial heart (TAH) Heart transplantation : a patient’s heart is replaced with a donor’s heart Cardiac support devices : Cardiac support devices Multi-filament yarn knit fabric support Provides ventricular support to reduce wall stress and myocardial stretch Reverse progressive dilation and improve cardiac function and patient functional status Mostly acts as bridge to recovery Intra aortic balloon pumps - IABP : Intra aortic balloon pumps - IABP IABP uses a balloon mounted on a catheter, which is inserted into the  aorta through the femoral artery in the leg The inflation and deflation of the balloon is synchronized to the heart’s pumping and is controlled from a console Balloon supports the heart indirectly, augmenting the blood flow Left ventricular assist devices - LVAD : Left ventricular assist devices - LVAD LVAD is a surgically implanted mechanical device that helps the heart pump blood Used as Bridge to heart transplantation Bridge to recovery permanent implants Two types Positive displacement type Centrifugal pump type Total artificial heart - TAH : Total artificial heart - TAH Natural heart is replaced with artificial twin pump Still in development stage Used only when Have end-stage heart failure. Have a life-expectancy of less than 30 days. Are not eligible for a natural heart transplant. Have no other viable treatment options Cardiopulmonary bypass : Cardiopulmonary bypass used to support patients during open-heart surgery. Patients' blood is diverted outside the body through the CPB circuit This allows for the patient's heart and lungs to bypassed facilitating surgery CPB machine artificially adds oxygen to the blood and then recirculates the blood back Extracorporeal cardiac devices : Extracorporeal cardiac devices Blood oxygneators Bubble Membrane Blood reservoirs Venous reservoir Cardiotomy reservoir CPB Pump Arterial filter Cardioplegia delivery system Hemo concentrator Oxygenator : Oxygenator Acts as lung during CPB Three functions are performed Adds oxygen and removes excessive carbon dioxide from patients blood Allows cooling and rewarming of the patient during surgery Acts as a reservoir of blood to be infused back to the patient as and when required Oxygenator Venous reservoir CPB Pump : CPB Pump Intended for pumping blood back to the patient with minimal damage to blood cells Two types Roller pump Centrifugal pump Roller pumps use positive displacement tubing pump technology Centrifugal pumps creates less damage to blood cells Roller Pump Centrifugal Pump Cardioplegia delivery system : Cardioplegia delivery system Intended deliver cardioplegia solution to the heart to stop its beating during open heart surgery A cooling coil is provided to cool the solution to around 5C The solution stops the heart and protects its muscles during the CPB period Arterial filters & hemo concentrators : Arterial filters & hemo concentrators Arterial filters are used for removing any blood clots that could have formed in the CPB circuit, prior to infusing back to the patient. Hemo concentrators are used for removing excess fluid present in the CPB circuit. Employed mainly in pediatric surgical procedures Cardiovascular devices - Future : Cardiovascular devices - Future Tissue engineering of cardiovascular devices offer immense opportunity Research in the area is in primitive stages One day world may see totally tissue engineered devices working in human heart …… but the day seems far away Heart : Heart Typically beats 3000000000 times in person’s life time Any attempt by man to repair, augment, replace …. are only suboptimal till now and never performs like the one nature created !! Slide 39:  Thank you

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