HHS CPO Pacing

Pacing Indications

• Symptomatic Bradycardia/block

• Sinus node dysfunction

• Witnessed asystole

• Post-op open heart sx

• Overdrive pacing

Temporary Pacemaker Methods

• Transcutaneous

• Transvenous

• Epicardial

Transcutaneous Pacing

Emergent for severe symptomatic bradycardia as a bridge to transvenous pacing

Transvenous Pacing

Tip of pacing catheter is wedged in trabeculae of RV

Epicardial Pacing

Postop cardiac surgery patients only

Pacemaker Components

1. Pacing generator

2. Bridging cable

3. Leads/wires

Cable Connector Polarity

Distal → Negative

Proximal → Positive

Output

Energy delivered to myocardium (mA)

Stimualation Threshold

Minimum amount of energy (mA) needed to consistently depolarize the myocardium

Atrial Pacing

Ventricular Pacing

Atrioventricular Pacing

Capture

Myocardial depolarization with enough energy from the pacemaker

Fusion Beat

Sensing/Sensitivity

Set parameter allowing the pacemaker to “see” intrinsic events (mV)

• Defines height of P or R wave to be detected by the pacemaker lead

• Lower value → higher sensitivity

Synchronous Pacing

Pacemaker only paces when necessary, able to sense intrinsic beats and will not fire

Asynchronous Pacing

Constant pacing at set rate, no ability to sense intrinsic heart activity

Paced Interval (PI)

Length of time between a paced event and the next paced event

• Automatic with a set rate - should not change

Escape Interval (EI)

Distance from an appropriately senesed event to the next paced event without intervening sensed events

• EI should be equal to PI

Intrinsic Interval (II)

Measurement of how long it takes the heart to generate its own electrical impulse (from paced beat to next intrinsic depolarization)

Intrinsic Rate below Paced Rate

Inappropriately sensing intrinsic activity or loss of output

Types of Pacemaker Malfunctions

1. Loss of Output

2. Loss of Capture

3. Oversensing

4. Undersensing

Loss of Output

No energy from pacemaker generator, can be intermittent or continuous

• EI>PI

Loss of Output Causes

• Battery Depletion

• Generator turned off

• Faulty cable connection

• Dislodged/fractured lead (XR)

• Oversensing

Loss of Output Interventions (Transcutaneous)

• Reestablish skin contact

• Monitor turned on and in pacing mode

• Change pads or generator

• Reestablish pacing

Loss of Output Interventions (Transvenous/Epicardial)

• Ensure generator is on

• Reconnect broken connections

• Replace generator or bridging cable

• Initiate TCP

Loss of Capture

Pacemaker fires, but is unable to stimulate myocardium

• Pacer spike seen but does not cause depolarization

Loss of Capture Causes

• Increased threshold

• Faulty cable connection

• Dislodged/fractured lead

• Lead tip against infarcted tissue

• Tissue is refractory

• Battery depletion

• Fibrin or clot on lead tip

Loss of Capture Interventions (Transcutaneous)

• Increase mA

• Change pacer pads

• Change TCP unit

Loss of Capture Interventions (Transvenous/Epicardial)

• Replace generator or bridging cable

• Reconnect broken or loose connection

• Increase mA

• Reverse lead polarity

• Initiation of TCP

Oversensing

Oversensitive to electrical artifact, pacemaker misinterprets muscle artifact or P/T waves as intrisic activity and doesn’t fire

• Pacemaker can fire irregularly or not at all

• EI>PI

Oversensing Causes

Physiological:

• Myopotential inhibition (i.e. pec contraction)

• Electromagnetic interference

• Peaked T waves

Lead/Systems:

• Dislodged/fractured lead

• Lead/pad contact

• mV set too low

Oversensing Interventions (Transcutaneous)

• Change pacer pads

• Change generator

Oversensing Interventions (Transvenous/Epicardial)

• Under direct order → turn sensitivity dial to decrease sensitivity until normal pacing occurs

• Initiate TCP

Undersensing

Pacemaker fires despite intrinsic activity being present

• EI<PI

Undersensing Causes

• mV threshold set too high

• Battery depletion

• Dislodged/fractured elad

• Ventricular ectopic activity

• Change in native signal (i.e. antiarrythmatic meds)

• Fibrin/clot formation at lead tip

Undersensing Interventions (Transcutaneous)

• Change pacer pads

• Change out TCP unit

Undersensing Interventions (Transvenous/Epicardial)

• Replace generator, bridging cable

• Reverse lead polarity

• Turn sensitivity dial to lower mV and increase sensitivity