植入性心臟電子儀器(CIEDs) 的基本原理及設定

高雄長庚醫院 心臟內科 陳煌中 醫師 2013.10.19 (W6) 蓮潭會館

Outlines

• Introduction of CIEDs (cardiovascular implantable electronic devices)

• General Setting of PPM

– Pacing, sensing, capture

– Low rate, upper rate

– Pacing mode

– Refractory and blanking period

– Other setting

Reference

Atria

Ventricles

Bundle branches

AV node

SA node

Cardiac Conduction Review

Implantable pulse generator (IPG) • Battery • Circuitry • Connector(s)

Lead wire(s)

Implantable Pacemaker System

Myocardial tissue

Circuitry

Battery

Connector Block

Lead Characterization

Bipolar coaxial lead

Passive Fixation Leads Active Fixation Leads

Epicardial Leads

Characteristics of an Electrical Circuit

• Voltage (V) – Voltage is the force, or “push,” that

causes electrons to move through a circuit

– Provided by the pacemaker battery

• Current (I) – Determined by the amount of

electrons that move through a circuit – Cause myocardial cells to depolarize

• Impedance (R or W) – The opposition to current flow – All resistance: conductor, electrode,

myocardium

V

I R

Battery Capacity and Longevity

Battery Capacity and Longevity

Voltage and Current Flow Electrical Analogies

Spigot (voltage) turned up, lots of water flows (high current drain)

Spigot (voltage) turned low, little flow (low current drain)

Water pressure in system is analogous to voltage – providing

the force to move the current

Lead Impedance, 300~1500 Ohm

High impedance Low impedance

Conductor failure, impedance >2500 Ohm Insulation defect, Impedance <300 Ohm

The Revised NASPE/BPEG Generic (NBG) Code for Antibradycardia Pacing

I II III IV V

Chamber(s) Paced

Chamber(s) Sensed

Response to Sensing

Rate Modulation

Multisite Pacing

O = None

A = Atrium

V = Ventricle

D = Dual (A + V)

S = Single (A or V)

O = None

A = Atrium

V = Ventricle

D = Dual (A + V)

S = Single (A or V)

O = None

T = Triggered

I = Inhibited

D = Dual (T + I)

O = None

R = Rate modulation

O = None

A = Atrium

V = Ventricle

D = Dual (A + V)

NASPE is the North American Society of Pacing and Electrophysiology BPEG is the British Pacing and Electrophysiology Group

BERNSTEIN, et al.; PACE 2002; 25:260–264

Indication • DDD(R)

• complete AV block

• sinus nodal dysfunction

• paroxysmal atrial fibrillation

• AAI(R)

• sinus nodal dysfunction

• VVI(R)

• permanent atrial fibrillation

DDD/DDDR

AAI/AAIR

Which mode is appropriate?

VVI/VVIR

Optimal Pacing Mode in Sinus Node Disease and AV Block

2013 ESC Guidelines on cardiac pacing and cardiac resynchronization therapy

Programmability

General Setting of Pacemaker

Parameter Description Setting Recommendation

Base Rate Pacing timing cycle •Depends on patient’s need •Nominal setting 60-70 bpm

Hysteresis Rest rate

Max. Sensor rate

Maximum Sensor Rate (MSR) is the highest pacing rate allowed by rate-modulated pacing

•Depends on patient’s age and activity (220-Age)X0.85

Max Tracking Rate

upper limit of the ventricular pacing rate in response to the patient’s intrinsic atrial activity

•Depends on patient’s age and activity (220-Age)X0.85 •Also has to consider the other cardiac disease

Parameter Description Setting Recommendation

AV/PV delay AV : internal of Ap to Vp PV : interval of As to Vp

• AVB : 200-150 • SSS : depends on the AV conductivity, nominal less than 300ms

Reduce unnecessary ventricular pacing VIP/AICS/AV hysteresis /MVP

Rate responsive AV/PV delay

shorten AV/PV Delay when the atrial rate is higer then 90 bpm, to mimic physical demand, also allows setting higher MTR

Off, slow, mid, high

Pulse Amplitude, Pulse width (A, V)

determines how much electrical potential is applied to the myocardium during the pacing stimulus

Nominal setting 2.5V@0.4ms

• 2-3 times of threshold to secure capture

• AutoCapture

A/V sensitivity

This parameter determines the amplitude of signals to which the device’s sense amplifiers will respond

• A : 0.5~1.0 mV • V : 2~3 mV

Higher level indicate less sensitive to P/R wave

General Setting of Pacemaker

• Very useful in helping you understand how the IPG is interpreting events

• Code: – AS Atrial Sense

– AP Atrial Pace

– AR Atrial Refractory

– VS Ventricular Sense

– VP Ventricular Pace

– VR Ventricular Refractory

Pacemaker Code

Sensing, Pacing, Capture

Pacemaker Sensing

Sensing Threshold

Output Pulse of Pacemaker

Pacing Threshold Pulse Amplitude and Width (Duration)

No Capture! No Capture!

Strength – Duration Curve

Safety Ratio for Capture

Safety Ratio for Capture

Automatic Stimulation Threshold Search

Lower rate, Rest rate, Upper rate

• The lowest rate the pacemaker will pace the heart in the absence of intrinsic events

Lower Rate Interval (LRI) - VVI

LRI LRI

Hysteresis

• Allows the rate to fall below the programmed lower rate following an intrinsic beat

60 bpm 50 bpm

Rest Rate

• Allows the pacemaker to decrease the base rate to the programmed auto rest rate during periods of inactivity.

• People spend about 7 hours, out of a 24 hour day, sleeping, therefore 29% of the time is spent sleeping.

• The pacemaker calculates where this 29% would occur based on the Activity Variance Histogram and establishes this point as threshold.

• When the need for oxygenated blood increases, the pacemaker ensures that the heart rate increases to provide additional cardiac output.

“R” = Rate Response

Rate-Adaptive Pacing

Accelerometer Circuit Board

Rate-Adaptive Pacing: Accelerometer

• Low current drain

• Easy to manufacture

• Rapid response to onset of activity

• Compatible with standard pacing leads

• Not responsive to pressure applied to can

• Used in all current St. Jude Medical pacemakers (began with Trilogy DR+)

Rate-Adaptive Pacing

• The Sensors—Physiology

– Evoked response

• The QRS depolarization decreases in area with exercise

• Works only when the device is pacing

– QT interval

• QT interval shortens with exercise

• Works only when the device is pacing

Rate-Adaptive Pacing: St. Jude

• Reactive time and recovery time

Upper Rate Response

• Dual-chambers pacemakers try to maintain 1:1 AV synchrony but this is not always possible

• In the presence of high intrinsic atrial rates, pacemakers may revert to upper rate responses

Upper Sensor Rate

• Defines the shortest interval (highest rate) the pacemaker can pace as dictated by the sensor (AAIR, VVIR modes)

Tracking

Upper Tracking Rate (UTR)

AS VP

AS VP

DDDR 60 / 100 (upper tracking rate) Sinus rate: 100 bpm

Lower Rate Interval {

Upper Tracking Rate Limit

SAV SAV VA VA

• The maximum rate the ventricle can be paced in response to sensed atrial events

Wenckebach No

Ventricular Pacing

UTR

Atrial Rate

Ve

ntr

icu

lar

Rat

e

LR 1:1 Atrial Tracking

2:1 Block

UTR LR TARP

= Ventricular Pacing

Upper Rate Behavior

Wenckebach Operation

DDD / 60 / 120 / 310

2:1 Block

DDD / 60 / 120 / 310

Upper Rate Behavior – 2:1 Block

Wenckebach vs. 2:1 Block

• If the upper tracking rate interval is longer than the TARP, the pacemaker will exhibit Wenckebach behavior first.

• If the TARP (total atrial refractory period) is longer than the upper tracking rate interval, then 2:1 block will occur.

Pacing Mode

AAI Mode

VVI Mode

DDD Mode

Benefits of Dual Chamber Pacing

• Provides AV synchrony

– Lower incidence of atrial fibrillation

– Lower risk of systemic embolism and stroke

– Lower incidence of new congestive heart failure

– Lower mortality and higher survival rates

The Magnet Test (VOO Mode)

Magnet ECG – St. Jude

Magnet ECG – Medtronic

Refractory & Blanking Period

Blanking and Refractory Periods

• Blanking Period – A period of time during which the sense amplifiers

are off, and the pacemaker is “blind”.

– Designed to prevent oversensing pacing stimulus

• Refractory Period – A period of time during which sensed events are

ignored for timing purposes, but included in diagnostic counters

– Designed to prevent inhibition by cardiac or non-cardiac events

Why Do We Use Refractory and Blanking Periods?

• Pacemaker sensing occurs when a signal is large enough to cross the sensing threshold

1.25 mV Sensitivity

Time

5.0 mV

2.5 mV

1.25 mV

Sensing does not tells us anything about the origin or morphology of the sensed event, only its “size.”

SENSE!

• By manipulating the sense amplifiers, we filter signals based on their relationship

The potential for digitizing these signals may someday allow pacemakers to discriminate signals based on morphology rather than just on their relationship.

Blanking Refractory

Time

5.0 mV

2.5 mV

1.25 mV

Sensing

Why Do We Use Refractory and Blanking Periods?

Blanking Periods

• Atrial Blanking (AB) – A non-programmable atrial blanking period (50-100 ms) from

atrial paces or senses.

– Avoid the atrial lead sensing its own pacing pulse or P wave (intrinsic or captured).

• Ventricular blanking (VB) – 50-100 ms in duration and is dynamic, based on signal strength.

– After a ventricular paced or sensed event to avoid sensing the ventricular pacing pulse or the R wave (intrinsic or captured).

• Post ventricular atrial blanking (PVAB) – Initiated by a ventricular pace or sensed event (220 ms)

– Avoid the atrial lead sensing the far-field ventricular output pulse or R wave.

Ventricular Blanking

• The first portion of the refractory period

• Pacemaker is “blind” to any activity

• Designed to prevent oversensing pacing stimulus

Lower Rate Interval

VP VP VVI / 60 Blanking Period Refractory Period

Blanking Periods

Post Atrial Ventricular

Blanking Ventricular Refractory Period

Ventricular Blanking

VRP

ARP PVARP

PVAB

Ventricular Refractory and Blanking Periods

AV Crosstalk

• Atrial pacing spike will be detected in the ventricle.

• Will inhibit ventricular pacing

Add PAVB to Prevent AV Crosstalk

ARP

Blanking Periods

Atrial Blanking

Atrial Refractory Period

Post Ventricular Atrial Blanking

Post Ventricular Atrial Refractory Period

PVARP

VRP

PVAB

Atrial Refractory and Blanking Periods

Refractory Periods

• VRP and PVARP are initiated by sensed or paced ventricular events.

– The VRP is intended to prevent self-inhibition such as sensing of T-waves.

– The PVARP is intended primarily to prevent sensing of retrograde P waves, far-field R wave, or premature atrial contractions.

• Pacemaker VRP avoids the sensing of :

– Its own stimulus

– The paced QRS complex

– The T wave

– (Excessive) afterpotential

– The combination of T wave and afterpotential

Ventricular Refractory Period

VP

VR

VP

VR

1000 ms 1000 ms

Blanking

Refractory

VRP 320 ms VRP 320 ms

Pacemaker Mediated Tachycardia (PMT)

Evaluation of Retrograde VA Conduction

PVARP

Prevention of PMT

• Prevention

– Extend PVARP (Post Ventricular Atrial Refractory Period)

– Program PVARP 50 ms longer than measured retrograde VA conduction (RVAC)

• Use VVIR mode to determine the RVAC

Algorithms for automatic Termination of PMT

AV Delays

The 4 Fundamental Timing Cycle of a DDD Pacemaker

AV Delay or AV Interval (AVI)

• AVI is the interval between an atrial event (either sensed or paced) and the scheduled delivery of a ventricular stimulus.

• Typical sAVI is 30-50 ms shorter than pAVI (sAVI < pAVI).

• The AV intervals may be programmed to fixed values or rate-adaptive (i.e. shortening with increasing atrial rates).

The Rate-Adaptive Interval

• The rate-adaptive AV interval mimics the physiologic response of the heart.

The 4 Fundamental Timing Cycle of a DDD Pacemaker

Other Setting

Automatic Mode Switching (AMS)

• AMS turns off atrial tracking in the presence of intrinsic atrial activity above a programmable atrial rate cutoff.

• Mode will switch from tracking mode (DDDR, DDD) to DDIR (non-tracking mode) when atrial arrhythmia is detected.

• AMS can cause a sudden rate decrease as atrial tracking.

• Ventricular pacing is decoupled from atrial events, but rate responsive pacing is matched to metabolic needs.

Mode Switch

• The device detects an atrial arrhythmia by constantly comparing intervals with the programmed mode switch detection rate.

DDD / 60 / 120 Mode Switch ON

MS

減少右心室電刺激 = 減少心衰竭住院及心房顫動

There is a 1% increase in the risk of AF for each 1%

increase in cumulative right ventricular pacing.

Cumulative % Ventricular Pacing

Within 95%

Confidence

Ris

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F R

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VP

=0

Risk of AF

Every incremental 1% of unnecessary VP increases the risk for Heart Failure Hospitalizations by 5.4% MOST study

Ventricular Intrinsic Preference (VIP)

• VIP activation

– Device extends AV delays by 160 ms searching for R-waves for up to 3 cycles in our example

– R-waves found within 1 cycle, therefore, AV delay remains at lengthened value

1 2 3

• VIP deactivation

– Device extends AV delays by 160 ms searching for R-waves for up to 3 cycles in our example

– No R-waves found within 3 cycle, therefore, AV delays returns to programmed values.

Ventricular Intrinsic Preference (VIP)

Ventricular Intrinsic Preference (VIP)

• VIP most beneficial

– Intermittent AV block

– Mild prolongation of AV conduction

• VIP not beneficial

– Complete permanent AV block

– Marked 1st degree AV block

– If CRT therapy is indicated

• VIP clinical benefits

– Less risk of heart failure progression

– Less risk of developing AF

– Better QoL trough improved hemodynamics

MVP AAI (R) to DDD(R) Operation

Switch from AAI(R) to Temporary DDD(R) Mode Ventricular support if loss of A-V conduction is persistent.

Switch to DDD(R) occurs after

back-up VP; programmed PAV/SAV are

used during this mode of operation

2 out of 4 Most Recent A-A Intervals with No Conducted VS Event

Ventricular Back-Up

Pace at 80 ms Post

the Scheduled AP

No VS

Conduction

Managed Ventricular Pacing (MVP)

Dual Coil Lead

Proximal

Shock

Electrode

Distal

Shock

Electrode

Hot Can

Single Coil Lead

Cold Can

Intracardiac Defibrillator (ICD)

Cardiac Resynchronization Therapy

Goal: Mitigate dyssynchrony through atrial synchronous biventricular pacing

Right Atrial

Lead

Right Ventricular

Lead

Left Ventricular

Lead

• LV lead site: lateral = posterior > apical • OptiVol thoracic impedance (MID-HeFT study): 和PCWP成反比

Thank You for Your Attention! Have a Nice Weekend~