Basic Pacing Concepts 1 - BASIC PACING CONCEPTS CONCEPTS...

Unformatted text preview: BASIC PACING CONCEPTS CONCEPTS PART-I Electrophysiology Electrophysiology Pacing Systems Pacing Dr.M.Mohsin Hossain MBBS, FCPS,MD Assistant Professor of Cardiology Assistant Professor NICVD, Dhaka Electrophysiology The Heart Has an Intrinsic Pacemaker „ The heart generates electrical impulses that travel along a specialized conduction pathway „ This conduction process makes it possible for the heart to pump blood efficiently During Conduction, an Impulse Begins in the During Sinoatrial (SA) Node and Causes the Atria to Contract Sinoatrial Atria Sinoatrial (SA) Node Ventricles Atrioventricular (AV) Node Then, the Impulse Moves to the Atrioventricular (AV) Node and Down Then, the Bundle Branches, Which Causes the Ventricles to Contract the Atria SA node Ventricles AV node Bundle branches Impulse Formation and Conduction Normal Heart Function Normal Sinoatrial Node Normal Heart Function Normal Atrioventricular Node Normal Heart Function Bundle of HIS Normal Heart Function Normal Left Bundle Branch (LBB) Posterior Fascicle of LBB Anterior Fascicle of LBB Right Bundle Branch (RBB) Normal Heart Function Normal Purkinje Fibers Normal Heart Function Normal Normal Heart Function Normal Intervals Are Often Expressed in Milliseconds in „ One millisecond = 1 / 1,000 of a second Normal Sinus Rhythm Normal „ Atrial rate: 60-100 bpm – PR interval: 120-200 ms (.12-.20 seconds) – QRS interval: 60-100 ms (.06-.10 seconds) – QT interval: 360-440 ms (.36-.44 seconds) Diseased Heart Tissue May: „ Prevent impulse generation in the SA node „ Inhibit impulse conduction SA node AV node ARTIFICIAL CARDIAC PACING ARTIFICIAL • External energy sources can be used to stimulate the heart when disorder in impulse formation and/or conduction leading to symptomatic arrhythmias. • Pacemakers are integrated system that monitor cardiac rhythms as well as deliver electrical impulses to the myocardium • Cardiac pacing can be done to treat bradyarrhythmia and tachyarrhythmia. Pacemakers Perform Three Basic Functions Basic Pacing Pacing Sensing Sensing Timing Timing Pacing Systems Basic Components of Pacemaker System Lead wire(s) EPG IPG Pulse generator : - Power source - Electric circuitry Pacemaker Components Combine with Pacemaker Body Tissue to Form a Complete Circuit Body „ Pulse generator: power source or battery Lead „ Leads or wires „ Cathode (-ve electrode) „ Anode (+ve electrode) IPG Anode „ Body tissue Cathode The Pulse Generator: „ Contains a battery that provides the energy for sending electrical impulses to the heart „ Houses the circuitry that controls pacemaker operations Circuitry Battery Pacemaker Leads Leads Are Insulated Leads Wires That: Wires „ Deliver electrical impulses from the pulse generator to the heart „ Sense cardiac depolarization Lead Types of Leads „ Endocardial or transvenous leads „ Myocardial/Epicardial leads Cathode Cathode „ An electrode that is in contact with the heart tissue „ Negatively charged when electrical current is flowing Cathode Anode Anode „ An electrode that receives the electrical impulse after depolarization of cardiac tissue „ Positively charged when electrical current is flowing Anode Conduction Pathways Conduction „ Body tissues and fluids are part of the conduction pathway between the anode and cathode Anode Tissue Cathode During Pacing, the Impulse: Impulse onset „ Begins in the pulse generator „ Flows through the lead and the cathode (–) „ Stimulates the heart „ Returns to the anode (+) * Unipolar Pacing System Contains a Lead with Only One Electrode Within the Heart In This System, the Impulse: „ Flows through the tip electrode (cathode) „ Stimulates the heart „ Returns through body fluid and tissue to the IPG (anode) + Anode Cathode Bipolar Pacing System Contains a Lead with Two Electrodes Within the Heart Contains In This System, the Impulse: „ Flows through the tip electrode located at the end of the lead wire „ Stimulates the heart „ Returns to the ring electrode above the lead tip Anode Cathode Unipolar leads Unipolar „ Unipolar leads may have a smaller diameter lead body than bipolar leads „ Unipolar leads usually exhibit larger pacing artifacts on the surface ECG Bipolar leads Bipolar „ Bipolar leads are less susceptible to oversensing noncardiac signals (myopotentials and EMI) Coaxial Lead Design Single-Chamber Pacing System Single-Chamber „ The pacing lead is implanted in the atrium or ventricle, depending on the chamber to be paced and sensed Paced Rhythm Recognition Paced AAI / 60 Paced Rhythm Recognition Paced VVI / 60 Dual-Chamber Pacing System Dual-Chamber Systems Dual-Chamber Have Two Leads: Have „ One lead implanted in the atrium „ One lead implanted in the ventricle Paced Rhythm Recognition Paced DDD / 60 / 120 Paced Rhythm Recognition Paced DDD / 60 / 120 Paced Rhythm Recognition Paced DDD / 60 / 120 Paced Rhythm Recognition Paced DDD / 60 / 120 Most Pacemakers Perform Four Functions: „ Stimulate cardiac depolarization „ Sense intrinsic cardiac function „ Respond to increased metabolic demand by providing rate responsive pacing „ Provide diagnostic information stored by the pacemaker ...
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