BME 501Advanced Topics in Biomedical SystemsSpring 2014Dr. KayOverview of BME Applicationsto Cardiovascular SystemDiagnostic modalitiesChest X-Ray ECG/EKG (electrocardiogram)Echocardiogram• High-frequency sound waves bounce off heart's walls and valves• Returning echoes are electronically plotted to produce a picture of the heartUltra Fast Computed Tomography (CT)• Uses combination of x-rays and computer technology • Produces cross-sectional images (slices) horizontally and vertically• Standard x-rays: beam of energy aimed at part of body being studied• Plate behind body part captures variations of energy beam after it passes through skin, bone, muscle, and other tissue • Ultrafast CT scans: can take multiple images of heart within span of single heartbeat• Provides much greater detailed about heart’s function and structures• Decreases amount of time required for studyUltrafast Radiation Detector for CT Scanning • Used as a sectional X-ray imaging procedure for analyzing trans-axial slices in the human body• Fan beam is collimated from the radiation cone emitted by X-ray tube• Permeates a thin slice of examined area• During scan, high-performance X-ray tube revolves around the patient • Associated X-ray detector in linear array measures attenuated radiation through object being examined• Computer converts these signals into attenuation values relative to reference attenuation object (water) and displays them as a gray scale image.Cardiovascular MRI • Medical diagnostic technique• Utilizes radio waves and a strong magnetic field to create images of heart without use of X-rays• Can generate multi-planar images of heart• Enables structure and function of heart to be studied• Movie-like images of beating heart can be used for diagnosis, e.g.: - Blockage of blood flow - Damage of heart muscles• Non-invasive procedure, no known side or after effects, painlessExternal DefibrillatorExternal DefibrillatorPacemakersImplantable DefibrillatorIntra-Aortic Balloon Pump(IABP)• Balloon inflates during diastole at same time as closure of aortic valve –increases coronary artery blood flow (blood flow to heart)• Balloon deflates just before systole – decreases afterload that heart must push against to send blood to bodyAngioplasty• Medical procedure used to restore blood flow through narrowed/blocked artery in heart• Coronary arteries (arteries of heart) can become narrowed/blocked due to buildup of plaque on inner walls• Narrowing reduces flow of blood through artery, can lead to coronary artery disease and heart attack• Thin tube with balloon or other device on the end is introduced through a blood vessel in arm or groin (upper thigh) • Device is threaded up to site of narrowing or blockage in a coronary artery• Balloon is then inflated to push the plaque outward against the wall of the artery, widening artery and restoring blood flowIllustration shows cross-section of coronary artery with plaque buildup. Figure A: deflated balloon catheter inserted into narrowed coronary artery. Figure B: balloon is inflated, compressing the plaque and restoring the size of the artery. Figure C: normal blood flow restored in the widened artery.Cardiac Catheterization LabAngioplastyCoronary arteriesA. Catheter fed into femoral artery of upper legB. Catheter threaded up through aorta to area of blockage in coronary arteryC. Dye released, allowing visualization of blockageD.Balloon at tip of catheter inflated, opening blocked artery and expanding stentE. Stent holds artery open after catheter is removedStents• incorporated to prevent elastic recoil and reduce chances of coronary artery re-occluding soon after balloon inflation• Stent - Tiny cage of surgical grade stainless steel- Surrounds outside of balloon - As balloon is inflated, stent expands and locks into place - Scaffold of stent holds artery open once balloon has been removedStenting• Stents coated in biocompatible or drug-eluting material reduce growth of the scar tissue and reduce rate of re-occlusion• Drug-eluting materials often use immunosuppressive drug to prevent vascular smooth muscle cells from dividing and proliferating• Aspirin and other anti-clotting agents used to reduce risk of thrombus (clot) formationBare-Metal vs. Coated StentsVentricular Assist Device (VAD)• Ventricular assist devices often used to keep patients alive while they await a heart transplant• Assist devices take over the majority of the heart's pumping function, allowing the heart to rest, heal, and grow stronger• Patients with often become healthier and stronger before they undergo transplant surgery.Prosthetic Heart Valves• Heart valves play key role in regulating blood flow in the heart, opening and closing in sequence with each heartbeat• Cardiac valves act like one-way doors, allowing blood to flow either forward into the next chamber, or out of the heart into the pulmonary artery or aorta• Valves close to prevent back flow• Two main types of prosthetic valves:- Mechanical- Bioprosthetic (tissue)Mitral valveTricuspid valvePulmonic valveAortic