Heart & Pacemaker Basics Zhihao Jiang mLab@University of - PowerPoint PPT Presentation

Heart & Pacemaker Basics Zhihao Jiang mLab@University of Pennsylvania 1

Heart Anatomy • 4 heart chambers Right Left Atria Ventricles Courtesy of Medtronic Medical Systems 2

Impulse Formation • Natural pacemaker: Periodic electrical impulses SA node Medical Systems 3

Atrial Contraction • Activation  Muscle contraction Atria Medical Systems 4

Delay At AV Node • Allows the ventricles to fill fully AV node Medical Systems 5

Ventricular Contraction • Pump blood out of the heart Ventricles Medical Systems 6

Bradycardia • Slow heart rate Formation Conduction Medical Systems 7

Dual Chamber Pacemaker • Two leads implanted in right atrium and ventricle Pacemaker Medical Systems 8

Electrogram (EGM) signals • Voltage change due to activation A V Pacemaker Medical Systems 9

Atrial Sensing (AS) • Generate sensed event when signal above threshold Threshold A V AS Pace Pacemaker Medical Systems 10

Ventricular Sense (VS) • Same for ventricular channel A V AS Pace Pacemaker VS Medical Systems 11

V-A deadline & Atrial Pacing (AP) • Pace atrium when no AS within deadline A V AS AP Pace V-A Pacemaker VS Medical Systems 12

A-V deadline and Ventricular Pacing (VP) • Pace ventricle if no VS happen within deadline A V AS AP Pace A-V V-A Pacemaker VS VP Medical Systems 13

V-V deadline • Minimum ventricular rate allowed A V AS AP Pace A-V V-A Pacemaker V-V VS VP Medical Systems 14

Minimum Ventricular Pacing Interval • Scheduled VP delayed if time since last ventricular event (VS, VP) is less than threshold A V AS AS Pace A-V V-A Pacemaker V-V VS VP Medical Systems 15

Minimum interval between Sensed events • Mimic refractory property of heart tissue Noise A V AS Pace Pacemaker ARP VRP VS Medical Systems 16

Post-Ventricular Atrial Blocking period (PVAB) • Preventing crosstalk between A and V channels Threshold A V AS AP Pace Pacemaker PVAB VS VP Medical Systems 17

Single Chamber Mode • Maintain ventricular rate V Pace Pacemaker V-V VRP VS VP Medical Systems 18

Pacemaker Mediated Tachycardia (PMT) • Pacemaker inappropriately increases ventricular rate – Normal ventricular rate without pacemaker – Ventricular Tachycardia with pacemaker • Two cases – Atrial Tachycardia Response – Endless Loop Tachycardia (ELT) Medical CPS 19

Atrial Tachycardia Response: Open-loop • Atrial Tachycardia: Abnormally fast atrial rate A V Medical Systems 20

Atrial Tachycardia Response: Open-loop • AV node enters Refractory period A V AV node Refractory Medical Systems 21

Atrial Tachycardia Response: Open-loop • Another early atrial contraction A V AV node Refractory Medical Systems 22

Atrial Tachycardia Response: Open-loop • Blocked by AV node during refractory A V AV node Refractory Medical Systems 23

Atrial Tachycardia Response: Open-loop • Third atrial contraction A V AV node Refractory Medical Systems 24

Atrial Tachycardia Response: Open-loop • Blocked by AV node again A V AV node Refractory Medical Systems 25

Atrial Tachycardia Response: Open-loop • AV node refractory finished A V AV node Refractory Finished Medical Systems 26

Atrial Tachycardia Response: Open-loop • 3:1 A-V conduction A V Medical Systems 27

Atrial Tachycardia Response: Open-loop • Normal Ventricular rate in contrast to fast atrial rate A V Within safe region Medical Systems 28

Atrial Tachycardia Response: Closed-loop • Inappropriately increase ventricular rate A V AS Pace Pacemaker Medical Systems 29

Atrial Tachycardia Response: Closed-loop • Mimic refractory property of heart tissue A V AS Pace Pacemaker AV node Refractory Medical Systems 30

Atrial Tachycardia Response: Closed-loop • Some of the fast atrial events are filtered A V AS [AR] Pace Pacemaker AV node ARP Refractory Medical Systems 31

Atrial Tachycardia Response: Closed-loop • VP when AV node in Refractory • AV node function bypassed A V AS [AR] Pace A-V Pacemaker AV node Refractory VP Medical Systems 32

Atrial Tachycardia Response: Closed-loop • Ventricular rate at Upper Rate Limit A V AS AS [AR] [AR] Pace A-V A-V At URL Pacemaker VP VP Medical Systems 33

Endless Loop Tachycardia (ELT): Closed-loop • Pre-mature Ventricular Contraction (PVC) A V AS PVC Pace A-V Pacemaker VS VP Medical Systems 34

Endless Loop Tachycardia (ELT): Closed-loop • Retrograde conduction causing atrial contraction A V AS AS Pace V-A A-V Pacemaker Retrograde conduction VS VP Medical Systems 35

Endless Loop Tachycardia (ELT): Closed-loop • VP after A-V deadline A V AS AS Pace V-A A-V A-V Pacemaker VS VP VP Medical Systems 36

Endless Loop Tachycardia (ELT): Closed-loop • The VP-AS-VP pattern persists, causing ELT A V AS AS AS Pace V-A V-A A-V A-V A-V Pacemaker VS VP VP VP Medical Systems 37