BME 501 Advanced Topics in Biomedical Systems Spring 2014 Dr. Kay 1BME 501 Lecture Notes – Apr 28 BME Applications for Cardiovascular Pathologies • Heart Failure • Insufficient Coronary Blood FlowHeart Failure: Types of Heart Failure • Systolic dysfunction – Heart muscle of ventricle does not contract with sufficient force – Less oxygen-rich blood pumped throughout body • Diastolic dysfunction – Heart contracts normally – Ventricles do not relax/expand properly during diastole – Insufficient ventricular fillingHeart Failure: Types of Heart Failure • Can have failure of left, right, or both ventricles • Typically, left ventricle fails first • LV failure affects pulmonary circuit; RV failure affects systemic circuit • Feedback mechanisms cause increased HR, vasoconstriction, fluid retention to compensateHeart Failure: Left-Ventricular Assist Device Three Uses for LVAD • Bridge to transplant – Temporary – Sustains patient until heart transplant available • Bridge to recovery – Temporary – Sustains patient while heart recovers from acute shock • Destination therapy – Permanent – Alternative to transplant if patient not eligibleHeart Failure: Left-Ventricular Assist Device • Aids LV in pumping blood to aorta: takes blood from LV and pumps blood into aorta • Takes some of workload off heart • Works in parallel with LV (not a replacement)Heart Failure: Left-Ventricular Assist Device Three Major Components • Mechanical pump – Located internally – Placed in chest or abdomen • System controller – Located externally – Monitors and adjusts pumping • Power supply – Located externallyHeart Failure: Left-Ventricular Assist Device Two Kinds of Pumps • Axial flow impeller-driven pump – Magnetically levitated and controlled motor – Accelerates blood in direction of rotor’s axis • Centrifugal pump – Magnetically levitated and controlled, bearing-less motor – Accelerates blood to outer rim of pumpHeart Failure: Left-Ventricular Assist Device Complications • Infection • Hemolysis • Mechanical failure • No pulse in continuous flow models • Thrombogenesis • LV collapse Percutaneous site Preparation of LV implantation siteHeart Failure: Artificial Heart • Used to replace failed heart • Bridge to transplant when VAD not sufficient • Destination therapy when donor heart not available or patient not eligible for transplant Total Artificial Heart (TAH)Heart Failure: Artificial Heart • TAH replaces ventricles and all four valves • Pulsatile pumping results in rhythmic pulse • Can pump up to 10 liters per minute • Two main TAHs: CardioWest & AbioCorHeart Failure: Artificial Heart CardioWest • Two tubes run from TAH, through holes in abdomen to outside of body • Tubes are connected to external power source and control system • Compressed air pumped through tubes inflates/deflates diaphragms in each “ventricle”Heart Failure: Artificial Heart CardioWest • “Ventricles” fill partially (based on venous return) and eject fully • When body more active, more blood returns to “ventricles” • “Ventricular” filling determines CO • Both chambers ejected simultaneouslyHeart Failure: Artificial Heart AbioCor • Completely contained inside chest • Battery that powers TAH charged through skin • Energy from external charger reaches internal battery via transcutaneous energy transmission (TET)Heart Failure: Artificial Heart AbioCor • Hydraulic pump generates unidirectional flow of hydraulic fluid • Porting valve opens and closes to allow hydraulic fluid to flow from one side of TAH to other (alternating) • When fluid pushed to right, blood pumped into pulmonary circuit • When fluid pushed to left, blood pumped into systemic circuitHeart Failure: Artificial Heart Design Considerations • Biocompatible material – Non-allergenic and non-toxic – Non-thrombotic • Power source for pump – Transcutaneous power source increases risk of infection – Need battery for mobility • Control system – Monitor and adjust pumping to meet needs of patient • Durability – Undergoes ~100,000 cycles per day – Needs to last ~10 yearsInsufficient Coronary Blood Flow: Angioplasty & Stent Indications • Within 1 to 1.5 hours of a heart attack to restore blood flow to ischemic region • If coronary artery is observed to be blocked due to plaque build-up • Stabilization of re-opened artery usually necessary via stentInsufficient Coronary Blood Flow: Angioplasty & Stent Procedure • Guiding catheter threaded up femoral artery into coronary artery • Radio-opaque dye injected into coronary artery • Real-time x-ray used to assess disease state and location • Guide wire passed through guiding catheter • Tip of guide wire passed through/across blocked region LAD coronary artery stenosis 95% occlusion treated with PCI Before treatment After treatmentInsufficient Coronary Blood Flow: Angioplasty & Stent Procedure • Angioplasty catheter threaded along guide wire • Balloon with stent around it aligned with region of atherosclerotic plaque • Balloon inflated to compress plaque and stretch artery wall • Expanded stent remains behind to support newly stretched artery from insideInsufficient Coronary Blood Flow: Stent • Incorporated to prevent elastic recoil and reduce chances of re-occlusion • Components: – Tiny cage of surgical grade stainless steel – Mesh locks into place when expanded by balloon inflation – Can be coated with drug-eluting polymerInsufficient Coronary Blood Flow: Stent Two Types of Stents • Bare-metal stents – Used for  Acute MI  Vessels with larger diameters  Patients who cannot be on long-term anti-platelet therapy • Drug-eluting stents – Help prevent restenosis via scarring/tissue regrowth – Used for  Longer stented regions  Vessels with smaller diameters  Diabetic patientsInsufficient Coronary Blood Flow: Intra-Aortic Balloon Pump Indications • Cardiogenic shock (e.g., following MI) • Unstable angina • Following cardiothoracic surgery • Pre-operatively for coronary artery bypass graft (CABG) surgery Counter-Indications • Severe aortic valve insufficiency • Aortic dissectionInsufficient Coronary Blood Flow: Intra-Aortic Balloon Pump • Mechanical device • Consists of cylindrical balloon mounted on a catheter in aorta • Counterpulsates heart: deflates during systole, inflates during diastole •