SEM 2 Lab 1 Exercises: Vignette 1 Flashcards
What is Magnet Mode?
Applying a magnet to a pacemaker will initiate the magnet mode.
This mode varies with pacemaker set-up and manufacturer.
Usually initiates an asynchronous pacing mode – AOO, VOO, or DOO.
What is Asynchronous Mode and what are the risks associated? And how does this differ from Magnet application to an ICD?
Asynchronous modes deliver constant rate paced stimuli regardless of native rate of rhythm.
In asynchronous ventricle pacing there is a risk of pacemaker-induced ventricular tachycardia.
Note this differs from magnet application to an Implantable Cardioversion Defibrillator (ICD) which results in defibrillator deactivation.
What are the several common causes for a rapid pacemaker?
Common Causes include:
- a normal response to a patient’s intrinsic tachycardia,
- an atrial arrhythmia (e.g. atrial flutter),
- a pacemaker-mediated tachycardia,
- or a sensor-induced tachycardia (e.g. when the sensor indicated by position IV of the pacemaker code misfires due to other stimulation)
What are PPM and where is located?
Permanent Placement Pacemakers
Cardiac pacemakers may be temporary or permanent, with the latter commonly known by the acronym PPM (permanent pacemaker).
What are Cardiac pacemaker Categories?
Categorization depends on the number of electrodes and location of pacing:
- Single chamber cardiac pacers- lead terminates in the right ventricle
- Dual chamber cardiac pacers- leads terminate in the right atrial appendage and right ventricular apex
- Biventricular pacers - also known as cardiac resynchronisation therapy (CRT)
- a normal dual chamber system with an additional lead that is introduced along thecoronary sinus and wedged in a left ventricular cardiac vein overlying the left ventricle
Epicardial biventricular pacers - epicardial wires are usually placed during cardiac surgery and tend to be placed over the left ventricular apex, right atrial appendage, and right ventricular apex
Leadless cardiac pacers - implanted into the right ventricle with no leads, introduced in 2015 (should not be mistaken for loop recorders)
What are the two (2) types of cardiac conduction devices?
Pacemakers and Automatic Implatable Cardioverter-Defibrillation (AICD/ICD)
What are the differences between them (AICD vs ICD)?
Both have two major components:
P - pulse generator (battery pack and control unit)
-most commonly placed subcutaneously in the infraclavicular area, where the
lead wires with electrodes for contact with the endocardium or myocardium
How are Pacemakers classified?
By the Nature of their pacing mode.
Classifications are then followed by Pacemaker CODE.
The CODE (last revised in 2002) is made up of a series of up to 5 letters:
Position I:Chambers Paced - Refers to chambers paced.
Position II:Chambers Sensed - Refers to the location where the pacemaker senses native cardiac electrical activity.
Position III:Response to Sensing - Refers to pacemakers response to sensed native cardiac activity.
T = Sensed activity results in triggering of paced activity
I = Sensed activity results in inhibition of pacing activity
Position IV:Rate Modulation - Indicates ability for rate modulation designed to altered heart appropriately to meet physiological needs e.g. physical activity. Sensors may measure and respond to variables including vibration, respiration, or acid-base status.
Position V:Multisite Pacing - Allows indication of multiple stimulation sites within one anatomical area e.g. more than one pacing site within the atria or biatrial pacing
The appearance of the ECG in a paced patient is dependent on the pacing mode used, placement of pacing leads, device pacing thresholds, and the presence of native electrical activity. Features of the paced ECG are:Pacing spikes
Vertical spikes of short duration, usually 2 ms.
May be difficult to see in all leads.
Amplitude depends on position and type of lead.
Bipolar leads result in a much smaller pacing spike than unipolar leads.
Epicardially placed leads result in smaller pacing spikes than endocardially placed leads.
Atrial Pacing
Pacing spike precedes the p wave.
Morphology of p wave dependent of lead placement but may appear normal.
Ventricular Pacing
Pacing spike precedes the QRS complex.
Right ventricle pacing lead placement results in a QRS morphology similar toLBBB
Left epicardial pacing lead placement results in a QRS morphology similar toRBBB
ST segments and T waves should be discordant with the QRS complex i.e. the major terminal portion of the QRS complex is located on the opposite side of the baseline from the ST segment and T wave.
Dual Chamber Pacing
Dependent on areas begin paced.
May exhibit features of atrial pacing, ventricular pacing or both.
Pacing spikes may precede only p wave, only QRS complex, or both.
The absence of paced complexes does not always mean pacemaker failure as it may reflect satisfactory native conduction
Pacemakers can have leads, that pace:
Right atrium - tip of lead is located in atrial appendage.
Right ventrical - tip in apex.
Left ventricle - lead through the coronary sinus ends in posterior cardiac vein, used for cardiac synchronization therapy in patients with bundle branch blocks.
Epicardial - placed on ventricle mainly used in cardiac surgery.
Cardiac pacemakers may be temporary or permanent, with the latter commonly known by the acronym PPM (permanent pacemaker).
Categorization depends on the number of electrodes and location of pacing:
Single chamber cardiac pacers- lead terminates in theright ventricle
Dual chamber cardiac pacers- leads terminate in theright atrial appendage and right ventricular apex
Biventricular pacers - also known as cardiac resynchronisation therapy,a normal dual chamber system with an additional lead that is introduced along thecoronary sinus and wedged in a left ventricular cardiac vein overlying the left ventricle
Epicardial biventricular pacers - epicardial wires are usually placed during cardiac surgery and tend to be placed over the left ventricular apex, right atrial appendage, and right ventricular apex
Leadless cardiac pacers - implanted into the right ventricle with no leads, introduced in 2015 (should not be mistaken for loop recorders)
What is AAI?
AAI– Atrial pacing and sensing
If native atrial activity sensed then pacing is inhibited.
If no native activity sensed for pre-determined time then atrial pacing initiated.
Used in sinus node dysfunction with intact AV conduction.
Also termed atrial demand mode.
What is VVI?
VVI– Ventricle pacing and sensing
Similar to AAI mode but involving ventricles instead of the atrium.
Used in patients with chronic atrial impairment e.g. atrial fibrillation or flutter
What is DDD?
DDD– pacing and sensing the atria and ventricles
Commonest pacing mode.
*Atrial pacing occurs if no native atrial activity for set time.
*Ventricular pacing occurs if no native ventricle activity for set time following atrial activity.
*Atrial channel function is suspend during a fixed periods following atrial and ventricular activity to prevent sensing ventricular activity or retrograde p waves as native atrial activity.
How does an Pacing Spike appear?
The appearance of the ECG in a paced patient is dependent:
- on the pacing mode used,
- placement of pacing leads,
- device pacing thresholds,
- and the presence of native electrical activity.
Features of the paced ECG are:Pacing spikes
Vertical spikes of short duration, usually 2 ms.
May be difficult to see in all leads.
Amplitude depends on position and type of lead.
Bipolar leads result in a much smaller pacing spike than unipolar leads.
Epicardially placed leads result in smaller pacing spikes than endocardially placed leads.
Atrial Pacing
Pacing spike precedes the p wave.
Morphology of p wave dependent of lead placement but may appear normal.
Ventricular Pacing
Pacing spike precedes the QRS complex.
Right ventricle pacing lead placement results in a QRS morphology similar toLBBB
Left epicardial pacing lead placement results in a QRS morphology similar toRBBB
ST segments and T waves should be discordant with the QRS complex i.e. the major terminal portion of the QRS complex is located on the opposite side of the baseline from the ST segment and T wave.
Dual Chamber Pacing
Dependent on areas begin paced.
May exhibit features of atrial pacing, ventricular pacing or both.
Pacing spikes may precede only p wave, only QRS complex, or both.
The absence of paced complexes does not always mean pacemaker failure as it may reflect satisfactory native conduction
What is Pacemaker-mediated Tachycardia?
Pacemaker-mediated tachycardia is an endless-loop tachycardia, sustained, in part, by the presence of the pacemaker.
- requires the presence of retrograde ventriculoatrial conduction and a triggering event like premature ventricular contraction or loss of AV synchrony. P
** is similar to a re-entrant tachycardia, except that the pacemaker forms part of the re-entrant circuit; the tachycardia could therefore be avoided by programming a sufficiently long postventricular atrial refractory period (PVARP).
Treatment
Placing a magnet on the device during the PMT will change the pacemaker’s mode to dual-chamber pacing mode (in DOO, intrinsic P waves and R waves are ignored), which results in the termination of tachycardia by suspending the pacemaker’s sensing function
