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Modes of Pacing Seoul National University Hospital

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Presentation on theme: "Modes of Pacing Seoul National University Hospital"— Presentation transcript:

1 Modes of Pacing Seoul National University Hospital
Department of Thoracic & Cardiovascular Surgery

2 Electrophysiology of Pacing
Stimulation & depolarization of myocardial tissue Sensing of intramyocardial electrical activity Current pacemaker technology Pulse generator

3 Stimulation & Depolarization of Myocardial Tissue
The myocardium must be excitable The stimulus current density (current per unit cross-sectional area) must be sufficiently high & of sufficient duration to depolarize a group of cells that is large enough to initiate impulse propagation in the myocardium The pacemaker-generated impulse then relies on the intrinsic properties of cardiac specialized conduction & myocardial tissue for depolarization of the entire heart

4 Factors affecting Sensing
Sensing is the detection of real or spontaneous cardiac depolarization Electrode size Configuration of electrode (unipolar, bipolar) Position of the lead tip within the heart

5 Pacing Lead Technology
Attachment of electrode Active fixation Passive fixation 1. Chronic ventricular pacing thresholds tend to be lower with passive lead, in part because of tissue injury with active fixation 2. Sensing characteristics are similar between active & passive leads 3. Epicardial electrodes historically have poorer performance over long term than endocardial lead

6 Pulse Generator Power source Time circuitry Sensing circuitry
Output circuitry for channels connected to the electrodes Transceiver for telemetric communication with programming device

7 Single Chamber Pacemaker

8 Single Chamber Pacemaker

9 Single Chamber Pacemaker

10 Intrinsic P and R waves

11 Atrial Sensing / Inhibition

12 Ventricular Sensing / Inhibition

13 Pacing Interval / Pacing Rate
The rate at which the pacemaker will pace if the patient does not have their own rhythm Expressed in either PPM or ms

14 Rate Conversion Conversion Pacing rate in PPM divided into 60,000 = ms
60,000 / 60 PPM = 1000 ms Interval in ms divided into 60,000 = PPM 60,000 / 1000 ms = 60 PPM

15 Ventricular Sensing / Inhibition
pacing interval

16 Capture Definition The depolarization and resultant contraction of the atria or ventricles in response to a pacemaker stimulus.

17 Threshold Stimulation Threshold Definition :
The minimum amount of electrical energy that consistently produces a cardiac depolarization

18 Atrial Capture Pacemaker Stimulus Atrial Capture

19 Ventricular Capture Ventricular Capture (paced ventricular
beats look like PVC’s or LBBB)

20 Refractory Period Refractory Period

21 Alert Period Definition The portion of timing cycle where the device senses electrical activity (e.g. cardiac) & responds in a preset or programmed manner

22 Alert Period Refractory Period Alert Period

23 Dual Chamber Pacemaker

24 Dual Chamber Pacemaker
DDD T / I * I

25 Atrial & Ventricular Pacing

26 Sense in Atrium & Pace in Ventricle

27 Pace & Sense in Atrium & Pace in Ventricle

28 Pace Atrium & Sense Ventricle

29 Pace and Sense in Atrium Sense in Ventricle

30 AV / PV Delay AV Delay PV Delay

31 Post Ventricular Atrial Refractory Period (PVARP)
Definition Timeframe the atrial channel is refractory, initiated when there is either a ventricular pacer spike or sensed R-wave. PVARP

32 Atrial Alert Period Definition Timeframe after PVARP when the sense amplifier is open and can see P-waves

33 Atrial Alert Period Alert Period PVARP AV Delay PV Delay

34 Ventricular Refractory Period

35 Ventricular Alert Period
Definition Timeframe after the ventricular refractory period that the sense amplifier is open looking for R-waves

36 Ventricular Alert Period
Ventricular Refractory Period Ventricular Alert Period

37 Dual Chamber Pacing Minimum Rate or Base Rate
Lowest rate that the pacemaker will pace in the Atrium Maximum length of time the Pacemaker will wait for intrinsic activity

38 Dual Chamber Pacing Minimum Rate

39 Dual Chamber Pacing Maximum Rate / Maximum Tracking Rate
The fastest rate that the Ventricular channel can track intrinsic P-waves

40 Maximum Tracking Rate

41 Pacemaker Follow-up Aim Interval
Verify appropriate pacemaker operation Optimize pacemaker functions Interval Immediate and POD # 1 day Postoperative 3, 6, 12 months

42 Pediatric Aspects of Cardiac Pacing
Ventricular epicardial leads Thoracotomy approach Transdiaphragmatic approach Subcostal or subxiphoid incision Atrial epicardial leads Base of left atrial appendage Transvenous leads All the leads have the problem with child growth and results in high threshold, exit block, lead fracture. Even when a loop of lead was left in the pericardium, adhesions frequently formed that prevented unwinding of the loop.

43 Interrogation

44 Assess Current Pacemaker Function
Compare the surface ECG to markers to determine appropriate pacing (capture) & sensing

45 Measured Data Provides information on:
-Magnet Information, -Lead Status, -Battery Status

46 Diagnostics

47 Pacemaker Testing Sensing and Capture testing
should be performed to insure adequate safety margins are programmed

48 Ventricular Threshold Test
Sensing and Capture testing should be performed to insure adequate safety margins are programmed

49 Loss of Capture Definition:
The emitted pacemaker stimulus does not cause depolarization and resultant cardiac contraction

50 Ventricular Loss of Capture
Programmed Rate Programmed Rate

51 Problem Solving Loss of Capture Causes Dislodged Lead Insulation Break
Program Voltage higher Program Pulse Width higher Reposition pacing electrode

52 Sensing Threshold The sensitivity number is increased until loss of sensing is seen Then the sensitivity number is decreased until sensing is regained This is the Sensing Threshold

53 Ventricular Sensitivity Test

54 Oversensing Definition :
The sensing of events other than P or R-waves by the pacemaker circuitry

55 Ventricular Oversensing
Pacing interval Pacing interval Pacing interval Pacing interval Pacing interval

56 Causes of Oversensing Insulation Break Intermittent Lead Fracture
Myopotentials EMI Problem Solving Program sensitivity to a higher number Program the refractory period longer

57 Undersensing Definition :
Failure of the pacemaker circuitry to sense intrinsic P- or R-waves

58 Ventricular Undersensing
non-sensed R-waves

59 Causes of Undersensing Dislodged Lead Insulation Break Problem Solving Program the sensitivity to a lower number

60 Testing of Chronic Pacing System
Current Voltage Resistance Threshold Threshold Dislodgement of electrode from endocardium H H N Perforation H H N Exit block (fibrosis around electrode tip) H H N Pulse generator malfunction N N N Lead/connector abnormality N N N Battery depletion N N N Partial lead fracture L to N H H F F Complete lead fracture N H H Lead insulation fracture H H L H; high, N; normal, L; low. F; fluctuating

61 Follow-up Check Interrogate Measure Impedance Check Diagnostics
Check Sensing Measure Threshold

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