Pacemakers

Question 1

Indications for temporary pacemakers

Answer 1

• Symptomatic bradycardia unresponsive to medical therapy
  – 2nd Degree Type II and 3rd Degree Heart Block
  – Permanent pacemaker failure
  – Support cardiac output after cardiac surgery
  – Tachy dysrhythmias (overdrive pacing)
  – Diagnostic studies: Electrophysiology studies (EPS)

Question 2

Permanent pacemaker indications

Answer 2

– Sick Sinus Node Syndrome
– Symptomatic AV block
– Pan-conduction disease (often age related conduction tissue changes)
– Hereditary, idiopathic, or drug-related QT interval prolongation

Question 3

Permanent ventricular lead placement

Answer 3

 The ventricular lead is usually placed in the apex of the right ventricle and held in
with tines at the end to lead.

Question 4

Permanent Atrial Lead Placement

Answer 4

The atrial lead is harder to keep in place due to the smooth surface, therefore often a lead is used with a screw on the end to fix it within the atria
 Some leads emit steroids to reduce inflammation and scarring

Question 5

Pacemaker function: Pace

Answer 5

Electrical stimulus to the ventricle or atria
– Capture is the effective depolarization of the heart by the artificial pacemaker
– Capture threshold is the minimum pacemaker output setting required to pace the heart

Question 6

Pacemaker function: Sense

Answer 6

The pacemaker wire senses electrical activity in the chamber in which it is placed

Question 7

Pacemaker function: Pacing triggered

Answer 7

The pacemaker fires an electrical stimulus if it senses no electrical activity

Question 8

Pacemaker function: Pacing inhibited

Answer 8

The pacemaker inhibits electrical stimulus due to sensed intrinsic rhythm

Question 9

Pacemakers deliver a pacing stimulus only when…?

Answer 9

The hearts intrinsic pacemaker fails to function

Question 10

VVI

Answer 10

• The ventricular lead paces the ventricle and inhibits itself if it senses an intrinsic rhythm
• The patient loses atrial filling and atrial kick (loss of CO)

Question 11

DDD

Answer 11

– 1st D = both chambers are paced
– 2nd D = both chambers are sensed
– 3rd D = inhibits both atrial and ventricular pacing when sensing intrinsic rhythm; and triggers response to sensed atrial activity to allow for rate responsive pacing

Question 12

DDD: Atrial sensed with ventricular paced rhythm

Answer 12

– The SA node is intact and pacing normally

– AV synchrony remains intact

Question 13

DDD: Atrial Paced with intrinsic ventricular rhythm

Answer 13

• This strip shows loss of intrinsic SA node activity, the atrial lead then paces the atria
• The impulse travels normally through the AV node
• There is intrinsic BBB

Question 14

Limitations for DDD pacing

Answer 14

Atrial pacing cannot be achieved with chronic atrial fib

If a patient with a DDD pacer goes into Afib there are rate limitations set for the atrial and ventricular responses

Question 15

Pacemaker Codes

Answer 15

1. Chamber Paced
2. Chamber Sensed
3. Response to Sensing
4. Rate ResponsiveP

Question 16

Common occurrence: Fusion Beats

Answer 16

 Causes
– A paced and an intrinsic ventricular beat occur simultaneously
– Resulting QRS a mix between intrinsic and paced
Intervention : none

Question 17

Common occurrences: PVC

Answer 17

 Causes
– electrode causing irritable ventricular focus
– Note: PVC’s normally occur in the first 24h after lead placement
 Intervention
– May need to administer antiarrhythmic drugs – May need reposition of lead wire

Question 18

Complication: Battery Failure

Answer 18

Applying a magnet over the pacer will illicit fixed (asynchronous) pacing
If the battery is failing, the pacer will pace at a different rate than what’s programmed
If the battery of a DDD pacer begins to fail it will convert to VVI to conserve battery time

Question 19

Complication: Loss of output

Answer 19

 Possible Causes – Battery depletion – Pacemakeroff
– Oversensing
– Faulty cable connection
– Dislodged/fracturedlead

Question 20

Complication: Failure to capture

Answer 20

 The pacemaker spikes fail to initiate the depolarization of the ventricle
– EKG pacemaker spikes not followed by QRS complexes

Question 21

S/S Failure to capture

Answer 21

 Signs and Symptoms – bradycardia
– hypotension
– fatigue

Question 22

Failure to capture: Potential causes

Answer 22

– Displacement of the pacing
lead wire (most common)
– mA set too low
– fracture of the lead
– battery failure
– perforation of the myocardium by the lead wire
– edema or scar tissue formation at electrode tip
– fibrin formation at the lead tip

Question 23

Failure to capture interventions

Answer 23

 Intervention:
– Notify physician immediately
– The physician may need to reprogram the pacer, replace or reposition the pacing wire
– May reposition patient onto left side

Question 24

Less Common Causes of Noncapture May Include:

Answer 24

Twiddler’s syndrome Electrolyte abnormalities – e.g.,

hyperkalemia Myocardial infarction Drug therapy Battery depletion Exit block

Question 25

Accurate Sensing

Answer 25

The pacer needs to be able to “see” If the pacer can’t see the patient’s intrinsic it will fire indiscriminately  DANGER: R ON T Phenomenon Rare in today’s sophisticated pacers

Question 26

Complication: Failure to sense

Answer 26

 Pacemaker cannot see the patient’s intrinsic rhythm – EKG pacemaker spikes that fall where they shouldn’t; spikes may fall on T waves

Question 27

Failure to sense potential causes:

Answer 27

– misplacement of ventricular lead placement (most common) – inflammation or swelling around the electrode – battery failure – fracture of pacing lead wire

Question 28

Interventions for under-sensing

Answer 28

 Interventions: Notify physician – Reposition the patient to the left side – The physician may need to reprogram the generator or replace or reposition lead wire – Prepare for code situation

Question 29

Complications: Oversensing

Answer 29

 Lack of pacemaker activity – pacemaker does not pace or paces at a rate slower than the set rate  Symptoms depend on underlying rhythm and rate

Question 30

Probably causes of oversensing

Answer 30

– the pacemaker may sense or be inhibited by skeletal muscle contractions (more frequent with a unipolar lead) – electromagnetic interference – sensing of T waves or atrial activity – pacemaker sensitivity set too high

Question 31

Complication: Diaphragm pacing

Answer 31

``` Signs and Symptoms – hiccups – EKG artifact Possible causes – stimulation of phrenic nerve by the electrode tip – myocardial perforation by lead wire – excessive pacemaker voltage  Interventions – position patient on left side – surgery (reposition lead wire) – reduce mA ```

Question 32

Complications: : Chest or Abd. Muscle Stimulation

Answer 32

``` Signs and Symptoms – muscle twitching – pacemaker identification letters appear backward on chest x-ray Possible causes – high pacemaker output – lead fracture or insulation break – flipped pulse generator  Intervention – reduce pacemaker output – replace lead – reposition generator ```

Question 33

Founded Sources of EMI (Electrical magnetic interference)

Answer 33

1. Use of arc welding machinery 2. High-tension electrical wires 3. Carrying cellular phone in pocket near pacemaker generator 4. Magnetic resonance imaging (MRI) 5. Radiation therapy to the chest (pacemaker generator should be shielded) 6. Electrical cardioversion 7. Electrocautery use during surgical procedures (biggest problem in the hospital in regards to EMI) 8. Lithotripsy treatment 9. Transthoracic defibrillation 10. TENS Units

Question 34

Pacemaker Syndrome

Answer 34

Defined as:  Loss of AV synchrony  Retrograde ventriculoatrial (VA) conduction  Absence of rate response to physiological need S & S related to lower cardiac output. Treatment focuses on use of dual-chamber pacing as well as reprogramming timing.

Question 35

Transcutaneous Pacemaker

Answer 35

External pacemakers are built into portable cardiac monitor/defibrillators The impulse is conducted across the intact chest wall to activate the myocardium Used for emergent situations

Question 36

Energy and current for transcutaneous pacemaker

Answer 36

 The mean current required for electrical capture is usually 50 - 100 mA  IV analgesia and sedation is required for currents of 50 mA or more

Question 37

Transcutaneous pacing technique

Answer 37

 Place the pads on the patient  Set desired heart rate  Slowly increase mA until capture is obtained – Electrical capture is characterized by a pacer spike followed by a QRS – The QRS will change morphology – Cardiac capture is assessed by pulse – Assess hemodynamic response (BP, UO, skin)

Question 38

Transcutaneous pacing precautions

Answer 38

 Precautions – Failure to capture may occur due to electrode placement or patient size and body habitus (barrel-shaped chest) – Transcutaneous pacing contracts the chest muscle therefore: The rhythm strip could look like capture is occurring but just the chest wall is contracting – must check pulse for cardiac capture Failure to recognize the presence of treatable VF Failure to recognize that pacemaker is not capturing – Third degree burns can occur with prolonged use

Question 39

Antitachycardia overdrive pacing

Answer 39

– accomplished by pacing the heart for a few seconds at a rate faster than the tachycardia rate, then returning to the regularly paced or intrinsic rhythm – This is usually incorporated in implantable defibrillator devices

Question 40

Three lead pacing for BBB and CHF

Answer 40

– Pacing the atria and both ventricles to improve CO (cardiac resynchronization or CRT)

Question 41

Pacemaker mediated tachycardia

Answer 41

Can be stopped by placing a magnet over the generator | If SVT is in progress, the magnet will have little effect

Question 42

Pacemaker and magnet application

Answer 42

Magnet will result in asynchronous (DOO or VOO) pacing at either 65 or 85 BPM (for a Medtronic device) depending on battery status Application will not permanently affect the device (most devices)

Question 43

Analyzing pacemaker function

Answer 43

Identify the intrinsic rate and rhythm – are P waves present - what rate – are QRS complexes present - what rate Note evidence of paced activity: atrial, ventricular, both – measure the distance between two consecutive paced beats – determine the rate and regularity of the paced interval – measure the hysteresis - the period between an intrinsic beat and the next paced beat Evaluate the escape interval Evaluate the strip for failure to capture, failure to sense, oversensing, and failure to pace