Slide 1BME 501 Lecture Notes – Apr 23Electrical Conduction Abnormalities: PacemakersElectrical Conduction Abnormalities: PacemakersElectrical Conduction Abnormalities: PacemakersElectrical Conduction Abnormalities: PacemakersElectrical Conduction Abnormalities: PacemakersElectrical Conduction Abnormalities: PacemakersElectrical Conduction Abnormalities: PacemakersElectrical Conduction Abnormalities: PacemakersElectrical Conduction Abnormalities: PacemakersElectrical Conduction Abnormalities: PacemakersElectrical Conduction Abnormalities: AICDElectrical Conduction Abnormalities: AICDElectrical Conduction Abnormalities: AICDElectrical Conduction Abnormalities: AICDLeaky and Stenotic Valves: Valve Repair or ReplacementLeaky and Stenotic Valves: Valve ReplacementLeaky and Stenotic Valves: Valve ReplacementOpen-Heart Surgery: Heart-Lung MachineOpen-Heart Surgery: Heart-Lung MachineOpen-Heart Surgery: Heart-Lung MachineOpen-Heart Surgery: Heart-Lung MachineOpen-Heart Surgery: Heart-Lung MachineBME 501Advanced Topics in Biomedical SystemsSpring 2014Dr. Kay1BME 501 Lecture Notes – Apr 23BME Applications forCardiovascular Pathologies•Electrical Conduction Abnormalities•Leaky or Stenotic Valves•Open-Heart Surgery2Electrical Conduction Abnormalities:PacemakersIndications•Sinus Node Dysfunction–Malfunctioning SA node provides improper or zero pacing•Degrees of Heart Block–Signal propagation problems between chambers•De-Synchronization–Poor coordination between contraction of atria and ventricles3Electrical Conduction Abnormalities:PacemakersOld Pacemakers: 1950’s and 1960’sThe “Bakken”Bulky, internalStreamlined4Electrical Conduction Abnormalities:PacemakersProblems with old pacemakers•Batteries–Power source (external, bulky)–Poor longevity–Hermetic sealing and corrosion•Leads–Inefficiency (coating, tip design)–Fixation designs•Physiology–Invasive placement (epicardial vs. transvenous)–Ventricular synchronization–No rate responsivity •Environmental Issues–Electrical interference–Waste (nuclear, incineration/cremation)5Electrical Conduction Abnormalities:PacemakersNew Pacemaker Design•Implantability–Size–Packaging•Longevity–Power supply–Lead design–Power-saving algorithms•Monitoring–Sensing–Computational power6Electrical Conduction Abnormalities:PacemakersPower Supply•Batteries–Lithium iodide–10-15 years (0.8 to 3.0 amp-hours)•Reliability–Linear discharge, drops off quickly at ~ 14 years–Elective Replacement Indicator (3-4 Months)volts7Electrical Conduction Abnormalities:PacemakersEKG Sensing•Intracardiac electrogram–Uses principles of EKG to sense heart’s electrical activity–Sensed from “perspective” of pacemaker•Pacemaker intervenes when irregularities detected•Most common pathology–Sinus block–3rd degree AV block–Bundle branch block8Electrical Conduction Abnormalities:PacemakersComputational Improvements•Collection and storage of pacing information between follow-up visits•Sensing algorithms that only step in when necessary•Regular adjustment of pacing to minimize amount of power required (optimization)•Automatic capture verificationCaptureCurveDuration (ms)Amplitude (V)9Electrical Conduction Abnormalities:PacemakersCapture Curve10Electrical Conduction Abnormalities:PacemakersLead Implantation•Electrical Issues–Contact surface area–Transmission line efficiency•Biological Issues–Products of inflammation increase lead resistance–Bacterial infections (high mortality of endocarditis)•Mechanical Issues–Microfractures introduced during insertion (poor technique)–Fixation of leads (passive and active)Steroid-ElutingLeadsPassive-Fixation:Hook into trabeculaeActive-Fixation:Screw into myocardium11Electrical Conduction Abnormalities:PacemakersPlacement•Electrical leads guided through subclavian vein or cephalic vein Multiple possible lead configurations–Single-chamber pacing–Dual-chamber pacing–Bi-ventricular pacing•Pacing generator typically placed subcutaneously, below claviclePosterior of HeartCoronary sinus12Electrical Conduction Abnormalities:AICDAICD: Automatic Implantable Cardioverter-Defibrillator•Used to convert abnormal heart rhythms to normal ones•Indicated for people who have experienced–Ventricular tachycardia (VT) or fibrillation (VF)–Cardiac arrest or arrhythmia that caused loss of consciousness–Pathology of the heart muscle (e.g., cardiomyopathy)13Electrical Conduction Abnormalities:AICD14Re-Entry can produce VT and/or VFElectrical Conduction Abnormalities:AICDCompared to Pacemaker:•Similar components: battery, processor, housing, leads•Increased battery requirements:–Must provide greater amplitude pulses to achieve cardioversion vs. just pacing–Effective battery live ~5-7 years•Larger battery, higher capacity leads (sometimes)15Electrical Conduction Abnormalities:AICDModes of Operation•VT/VF Detection–Monitor atria and ventricles for arrhythmias–Differentiate between types of arrhythmias–Store heart signals for physician evaluation•Anti-Tachycardia Pacing–Sequence of closely spaced pulses•Cardioversion–Single, medium-voltage pulse applied for arrhythmias that show temporal irregularities•Defibrillation–Single, high-voltage pulse of up to 800 volts16Leaky and Stenotic Valves:Valve Repair or Replacement•Improperly functioning valves make heart work harder (e.g., turbulence, backflow)•If more than only a minor irregularity, must be repaired or replaced•Valve repair desirable if possible (e.g., valve only slightly abnormal)•Valve replacement usually requires open-heart surgery17Leaky and Stenotic Valves:Valve Replacement•Mechanical valves–Long-lasting, made of durable materials–More likely to damage blood cells and produce clots•Tissue valves–Animal or human donor tissue–Break down more rapidly18Leaky and Stenotic Valves:Valve ReplacementReplacement Valve Considerations•Minimal thrombogenesis–Foreign material–Cellular maceration•Failure safety•Minimal leakage•Dynamic responsiveness•Wear•Trans-valvular pressure gradient•Blockage19Tissue ValveMechanical ValveOpen-Heart Surgery:Heart-Lung Machine•Open-heart surgery requires heart to be stopped•Must provide oxygenated blood to body and brain during operation•Cardiopulmonary bypass (CPB) allows for systemic delivery of oxygenated blood20Open-Heart Surgery:Heart-Lung Machine•Multiple cannulae sewn into