Chapter 10 Flashcards
Electronic pacemakers
Artificial pacemakers, are devices that deliver an electrical impulse to the myocardium to cause the cells to depolarize. Provides small amount of electrical current in a predetermined interval to mimic the nl pacemaker of the heart.
How do pacemakers affect the atria
It aids in reestablishing nl electrical conduction of impulses, correct dysrhythmias
Standard rate of pacemakers
70-72 bpm
Where is the pacemaker placed
Atria, ventricles or both
Atrioventricular pacing
Provides direct stimulation of the atria and ventricles in a sequence patterns known as atrioventricular sequential pacing. It allows for an atrial kick. Used for pts with heart failure
Atrial kick
Provides the extra blood supply needed for approximately 10-30% of the normal cardiac output
Ventricular pacemaker
delivers direct stimulation to the ventricles and produces a ventricular contractions
Atrial pacemaker
Used alone when the conduction system from the atrioventricular node through the ventricles is intact and functioning
Evaluating Pacemaker Function
The most important aspect of care is to verity the effectiveness of the pacemaker and determine the presence of a pulse with each captured beat.
How is a capture seen in an ECG?
Captures are represented by a pacing spike immediately prior to the waveform
Pacing spike
Could be atria, ventricular, or both. It is an artifact indicating the stimulation of electrical current from the pacemaker generator. The current is a quick delivery and is reflected as a this pike followed by a P wave or a wide QRS complex or both.
Atrial pacing
Pacing spike will be followed by a P wave.
Ventricular pacing
Pacing spike will be followed by a wide QRS complex, which looks similar to a LBBB
LBBB pattern
Rhythm has a P wave and the QRS complex measures 0.12 sec or greater. L ventricle takes longer than the R to depolarize because of its size
AV Delay
Similar to the measurement of the PR interval on a nl rhythm tracing. Measured form the atrial spike to the ventricle spike.
AV delay programmed time frame
Somewhere between 0.12 to 0.20 seconds
Inherent rhythm
The pt’s own heart rhythm
7 steps to evaluate a pacemaker rhythm
- What are the rate and regularity of the paced rhythm? Paced spikes should be the same.
- What are the rate and regularity of the intrinsic rhythm (the pt’s own rhythm)? The faster rate will control the rhythm.
- Is the atrial lead sensing appropriate? (for AV sequential pacemakers only). Atrial spikes then P waves.
- (for atrial, AV sequential, and atriobiventricular pacemakers) Is atrial capture present? Atrial spike then P wave. The P wave after indicates that the atrial capture occurred.
- (for atrioventricular sequential and atriobiventribular pacemakers) Is atrioventricular delay appropriate? Atrioventricular delay is measured form the atrial spike to the ventricular spike, this should be the same as the rate set up for the pacemaker.
- Is ventricular sensing appropriate? There needs to be a ventricular spikes with a wide QRS following.
- Is ventricular capture present? Every ventricular spike should have a wide QRS complex after it.
Most common pacemaker rate setting
70 bpm
What battery to pacemakers use to create an impulse?
Lithium batteries
What are complications of the pacemaker?`
When the batteries are dying and need to be replaced which can cause slower firing rates than set, less effective sensing capabilities, and lower electrical current than predetermined
Gour pacemaker complications seen in the ECG
Malfunctioning
Malsensing
Loss of capture
Oversensing
Malfunctioning (failure to pace)
Caused by pacemakers not sending electrical impulses to the myocardium. Pacemaker intervals are irregular and impulse slower than set rate. No spike is seen. Pt will experience hypotension, lightheadedness, and blackout periods
Malsensisng (failure to sense)
Caused by pacemaker not sensing the pt’s own inherent rate. May send current to heart during relaxation phase; also known as pacemaker competition with the pt’s own heart. With atrial pacing, atrial fibrillation can occur; with ventricular pacing, ventricular tachycardia or ventricular fibrillation can occur.
Loss of capture (failure to depolarize)
Pacing activity occurs, but myocardium is not depolarized. Pacing spikes will occur without capture waveform, such as P wave or QRS complex. Symptoms depend on the basic dysrhythmia and the pt’s condition prior to the pacemaker insertion.
Oversensing
Pacemaker perceives electrical current from sources other than the heart. Either (1) the pt’s own heart rate is recorded and is slower than the set rate of the pacemaker or (2) the pacemaker spikes and captures at a slower rate than set. Pt may have signs and sx of low cardiac output.
What is BBB?
Occurs when one or both of the ventricular pathways are damaged or delayed due to cardiac disease, drugs, or other conditions.
What happens in the BBB?
When an area of one of the bundle branches is damaged, electrical current will not be able to travel through that tissue to reach the myocardial tissue in its usual fashion. Current will travel down the good bundle and will activate the myocardial tissue in that corresponding ventricle only. The other ventricle must then receive the impulse as current travels from one cell to the next until the entire myocardial contraction occurs.
What condition is similar to knocking down of a line of dominoes where each domino represents a cardiac cell?
BBB. The cell will not contract until the next cell delivers the energy.
How is the delay in ventricular contraction caused by BBB seen in an ECG?
A wider than nl QRS complex
RBBB
Impulse wil travel down the conduction pathway normally until after the bundle of His. Current travels down the L bundle branch to activate the ventricles.
LBBB
L conduction pathway is blocked. Current must travel down the R bundle branch to cause the R ventricle, the septum, then the L ventricle to contract.
How do we identify a BBB?
The appearance of a wide QRS complex with other atrial dysrhythmia properties.
How do we identify a RBBB?
Characteristics will be similar over monitoring leads I, II, and III as well as monitoring leads V1 and V6. QRS complex is positively deflected.
How to distinguish between RBBB or LBBB?
Seen in the precordial leads, lead VI is preferred. In LBBB the QRS complex is negatively deflected.
Signs and sx’s of BBB
Those of the basic rhythm. Ex: if the rhythm is sinus tachycardia with RBBB pt will have sx’s of fast hr. the BBB will further deteriorate the development of another bundle branch block, if the current becomes totally blocked and current cannot reach the myocardium, this is considered a complete heart block.
Tx to BBB
Monitoring, observation for deterioration. If further deterioration occurs, a temporary pacemaker may be applied. Further complications can lead to code blue and application of a permanent pacemaker.
