1. Questions included for Critical Care Competency Day 2010 - 2011
Pacing Reference
Questions included for
Critical Care Competency Day

2. Pacemaker
Medtronic 5388 Dual Chamber (DDD)

3. Temporary Pacing Review
The following slides are designed to help you review some aspects of temporary pacing.
Other resources available include
pacing resource book in SICU
medtronic website: temporary pacing powerpoints

4. Indications for Temporary Pacing

5. Placement of Epicardial Wires

6. Transvenous Pacing Insertion Sites Internal Jugular Vein
External Jugular Vein
Internal Jugular
Subclavian Vein
Subclavian
Brachial Vein
Femoral
Femoral Vein

7. Transvenous Pacing Wire
Bipolar lead system
Transvenous wire is floated into the right ventricle
The negative and positive electrodes are in contact with the heart

8. Single Chamber Temporary Pacing
Pacer Settings:
Pacing rate (heart rate)
Output/stimulation threshold
Sensitivity

9. Model 5388 Dual Chamber Temporary Pacemaker
1. Pace/Sense LEDs
2. Lock/Unlock Key
3. Lock Indicators
4. Rate Dial
5. Atrial Output Dial
6. Ventricular Output Dial
7. Menu Parameter Dial
8. Parameter Selection Key
9. Menu Selection Key
10. Pause Key
11. Power On Key
12. Power Off Key
13. Emergency/Asynchronous
Pacing Key
14. Lower Screen
15. Ventricular Output Graphics
16. Atrial Output Graphics
17. Upper Screen
18. Rate Graphics
19. Setup Indicators
20. DDI Indicator
21. Low Battery Indicator
22. Setup Labels
Single chamber pacing: AOO, VOO, AAI, VVI
Dual chamber pacing: DDD, DDI, DVI, DOO
Bipolar or unipolar configuration
9-volt alkaline or lithium battery power
Three-dial operation to meet most patient needs
Lock/Unlock key to prevent accidental parameter changes
Emergency key for immediate high output asynchronous DOO pacing
Menus for pacing parameter adjustments
Rapid Atrial Pacing (RAP)

10. Lower Screen Menus Menu 1: Pacing Parameters Menu 2: Rate-Based
Menus are for manual adjustment of pacing parameters, RAP, and pacing mode selection.
Currently displayed parameters are based on the current pacing mode, rate, and output.
Parameters not selectable are dimmed.
MENU key: Activate lower screen and page through menus.
SELECT key: Scroll through and highlight parameters.
MENU PARAMETER dial: Adjust the value of the highlighted parameter.
Lower screen:
NBG pacing code appears in upper lefthand corner.
*MANUAL appears in the upper right-hand corner to indicate that a parameter has been manually adjusted.
Menu 3: Rapid
Atrial Pacing
Menu M:
Dial-A-Mode

11. NBG Codes 1st Letter 2nd Letter 3rd Letter Chamber paced
Chamber(s) Paced
A = atrium
V = ventricle
D = dual (both atrium and ventricle)
Chamber(s) Sensed
A = atrium
V = ventricle
D = dual
O = none
Response to Sensing
I = inhibit (Demand mode)
T = triggered
D = dual
O = none (Asynch)
Chamber paced
Chamber sensed
Action or response to a sensed event

12. Set Up Guide

13. Pacemaker EKG Strips Assessing Paced EKG Strips
Identify intrinsic rhythm and clinical condition
Identify pacer spikes
Identify activity following pacer spikes
Assess for Failure to capture
Assess for Failure to sense
EVERY PACER SPIKE SHOULD HAVE A P-WAVE OR QRS COMPLEX FOLLOWING IT.

14. Depolarization of cardiac muscle following an electrical stimulus
Capture
Depolarization of cardiac muscle following an electrical stimulus

15. Sensitivity
The degree that the pacing system “sees” or senses signals, controlled by the sensitivity setting which is graduated in millivolts (mV)
Sensitivity (mV)
5 (mV)
2.5 (mV)
1.25 (mV)

16. Sensitivity
The lower the setting, the more sensitive the pacemaker is to intracardial signals

17. Normal Pacing
Atrial Pacing
Atrial pacing spikes followed by P waves

18. Normal Pacing Ventricular pacing
Ventricular pacing spikes followed by wide, bizarre QRS complexes

19. Normal Pacing A-V Pacing
Atrial & Ventricular pacing spikes followed by atrial & ventricular complexes

20. Troubleshooting Pacing
Look for
Failure to Fire (No Output from Pacer)
Failure to Capture (pacer not followed by depolarization)
Failure to Sense
Undersensing: pacer not sensing all intrinsic activity so may misfire at inappropriate times
Oversensing: pacer sensing artifact as well as intrinsic activity so may not fire when necessary

21. Failure to Fire: No Output
Possible Causes Corrective Measures
Battery depletion •Replace battery
Pacemaker OFF •Verify pacemaker settings
Faulty cable connections •Check cable connections
Fractured/dislodged lead •Replace/reposition lead
Oversensing •Verify/adjust sensitivity
Possible Causes Corrective Measures
Battery depletion •Replace battery
Pacemaker OFF •Verify pacemaker settings
Faulty cable connections •Check cable connections
Fractured/dislodged lead •Replace/reposition lead
Oversensing •Verify/adjust sensitivity
Possible Causes
Battery depletion
Pacemaker off
Faulty cable connection
Dislodged/fractured lead Oversensing
Corrective Measures
Replace battery
Verify pacemaker settings
Check cable connections
Reposition/replace lead
Verify/adjust sensitivity

22. Failure to Fire
Indicated by absence of pacer spikes where they should be
Possible Causes: Solution:
Low battery Replace battery
Loose connections Check and secure connections
Oversensing Increase mV to lower sensitivity
Lead dislodged or Fractured Place skin wire or reposition transvenous wire

23. Factors that Affect Capture and Sensing

24. Failure to Capture Causes Danger - poor cardiac output
Insufficient energy delivered by pacer
Low pacemaker battery
Dislodged, loose, fibrotic, or fractured electrode
Electrolyte abnormalities
Acidosis
Hypoxemia
Hypokalemia
Danger - poor cardiac output

25. Failure to Capture Solutions Check connections
Increase pacer output (↑mA)
Change battery, cables, pacer
Reverse polarity

26. Loss of Ventricular Capture
Atrial/Ventricular Stimulation Thresholds
Capture
Loss of Ventricular Capture
Capture-Depolarization of cardiac tissue after a pacing pulse. (The ECG shows a P-wave or QRS complex after the pacing pulse.)
Loss of Capture-The ECG shows no heart response after the pacing pulse.
Stimulation Threshold-Minimum output (mA) needed to consistently capture the heart.
Safety Margin-Ensures consistent capture and accommodates a changing threshold. Provide a 2:1 safety margin by setting output to a value at least 2 times greater than the stimulation threshold value.
Procedure:
1. Set RATE at least 10 ppm above patient’s intrinsic rate.
2. Decrease output: Slowly turn OUTPUT dial counterclockwise until ECG shows loss of capture.
3. Increase output: Slowly turn OUTPUT dial clockwise until ECG shows consistent capture. This value is the stimulation threshold.
4. Set output to a value at least 2 times greater than the stimulation threshold value. This provides at least a 2:1 safety margin.
5. Restore RATE to previous value.
Caution: Monitor patient’s ECG and blood pressure during procedure.

27. Abnormal Pacing Atrial non-capture
Atrial pacing spikes are not followed by P waves

28. Abnormal Pacing Ventricular non-capture
Ventricular pacing spikes are not followed by QRS complexes

29. Capture Threshold testing
Capture Stimulation threshold
Definition: Minimum current necessary to capture & stimulate the heart
Testing
Set pacer rate 10 ppm faster than patient’s HR
Starting at 0 mA, increase mA until 100% capture is obtained
This is your pacing threshold
Set mA 2-3x greater than the pacing threshold
Example: Set output at mA if 100% capture was at 5mA

30. Failure to Sense : Undersensing
Causes
Pacemaker not sensitive enough to detect patient’s intrinsic electrical activity (mVset too high)
Asynchronous pacing
Insufficient myocardial voltage
Dislodged, loose, fibrotic, or fractured electrode
Mechanical failure: wires, bridging cables, pacemaker
Low battery
Danger
Potential (low) for paced ventricular beat to land on T wave and lead to Vtach

31. Undersensing Solutions Check all connections
Make sure pacer is not set for asynchronous pacing
Increase pacemaker sensitivity (↓mV) until pacer spikes move away from intrinsic beats
Change battery

32. Undersensing Possible Causes Battery depletion Decreased QRS voltage
Fusion beat
Dislodged/fractured lead
Ventricular ectopic activity
Corrective Measures
Change battery
Increase sensitivity (decrease number)
Reposition/replace lead
Reposition patient

33. Abnormal Pacing Atrial undersensing
Atrial pacing spikes occur irregardless of P waves
Pacemaker is not “seeing” intrinsic activity

34. Abnormal Pacing Ventricular undersensing
Ventricular pacing spikes occur regardless of QRS complexes
Pacemaker is not “seeing” intrinsic activity

35. Failure to Sense
Danger – potential for paced ventricular beat to land on T wave

36. Oversensing
Inhibition of the pacemaker by events it should ignore such as:
T waves
Artifact

37. Oversensing
Causes
Pacemaker inhibited due to sensing of “P” waves & “QRS” complexes that do not exist
Pacemaker too sensitive
Possible wire fracture, loose contact
Pacemaker failure
Danger – asystole or heart rate too low to maintain adequate cardiac output
If pacer “thinks” intrinsic heart rate is at or above set rate, then it won’t pace

38. Oversensing Solution Check connections
Decrease pacemaker sensitivity (↑mV)
Change cables, battery, pacemaker
Reverse polarity
Check electrolytes

39. Oversensing Possible Causes Myopotential inhibition EMI
T-waves outside refractory period
Dislodged/fractured lead
Corrective Measures
Eliminate interference
Reduce sensitivity (increase number)
Reposition/replace lead

40. One Last Thing to Consider: Fusion and Pseudofusion Beats
Occurs when pacer
fires just after
intrinsic depolarization
begins. Pacer spike will appear at middle to
end of R wave.
Beat will be intrinsic.
This is also not a
malfunctoning
pacemaker. The pacemaker has fired
too close to time of
depolarization to be able to detect it.
If this were undersensing the pacer spike would be at the end of QRS or later.
Fusion Beat:
When Intrinsic
Depolarization
Initiates at Same
Instant as Pacer
Fires: Beat is
A combination
Of a paced and
Intrinsic beat
This is NOT a
problem with
The pacemaker
Intrinsic Beat
Paced Beat
Intrinsic Beat
Paced Beat
Fusion Beat
Pseudofusion Beat
Fusion Beat
Pseudofusion Beat 34

41. Pacing Responsibilities
Check all connections are proper
Assess and troubleshoot pacing problems
Failure to fire
Failure to capture
Under or over sensing
Determine pacing threshold and set mA appropriately
Document threshold and setting

42. Pacing Responsibilities
Determine underlying rhythm and document
This can be done when you are determining pacing threshold
By turning down the mA to below the pacing threshold, the patient’s intrinsic rhythm will become apparent
Document sensitivity settings
Atrial is normally < 1 mV
Ventricular is usually between 2-7 mV
For patient attached to pacemaker but not actively pacing, thresholds still need to be checked and documented
It is important to know that the pacemaker will work if the patient needs it
Additionally for transvenous pacing
Check and document position of pacing wire

43. Pacing Questions Look at each of the following pacing strips ?fire
?capture
?sensing properly
if not, is it undersensing or oversensing
?what would you do if you saw this strip

44. Practice Strip #1

45. Practice Strip #2

46. Pacing Strip #3

47. Practice Strip #4

48. Practice Strip #5

49. Pacing Strip # 6

50. Pacing Strip # 7