Clinical-Heart Block- Brandecker Flashcards
Which bundle conducts over to the left atrium from the right?
Bachman’s bundles
What is arrhythmia?
Any rhythm that is NOT normal sinus rhythm
What are the criteria for normal sinus rhythym?
originates from the sinus node in the right atrium.
Heart rate needs to be in the normal range (60 – 100).
Rate needs to be regular.
Normal upright P waves in lead 2
Which type of arrhythmia is normal in young healthy patients
demonstrates a Slight beat to beat variation
demonstrates heart rate increases on inspiration and slows down during expiration
sinus arrhythmia
As patients get older, they can develop which pathology which results in HR that is innappropriately fast or slow or results in a pause?
Sinus pause/sick sinus syndrome
Sinoatrial exit block is felt to be due to the impulse that in the SA node that is unable to exit the SA node and stimulate the . They basically result in the same process and there is a lack of P and wave. If the pauses is long enough the patient can have a loss of .
originates
atria
QRS
consciousness.
What is the treatment for Sinoatrial exit block?
Treatment will be pacemaker.
If the pause is too long in a sinoatrial exit block, it can result in what?
syncope (loss of consciousness) and is treated with pacemaker
There can be sinus arrest after episodes of atrial fibrillation that can result in .
paroxysmal
syncope
What is the first back up if SA node fails (60 - 100 bpm)?
AV node at 35-60 bpm
What is the next back up if SA and AV node fails or are blocked?
Purkinje cells (25-35 bpm) and Ventricular myocytes 35 bpm or less
What is overdrive suppression?
The fastest pacemaker (normally SA) sets the pace
What could it mean if the P wave maybe inverted, buried(not seen) or after QRS?
escape beats from AV node (AV junctional, junctional) taking over
-atria and ventricles may may be depolarized at same time
If the AV node produces an escape rhythm (35 to 60 bpm), how will the QRS interval appear?
QRS will appear normal since signal is originating in the AV node.
If the AV node produces an escape rhythm (35 to 60 bpm), how will the P wave appear?
The P wave is usually in the opposite direction from the normal P wave and can oftentimes be buried in the QRS complex.
Why can a P wave appear after the QRS complex in juncitonal escape rhythm?
nodal stimulus is frequently conducted back into the atria and a P wave and atrial contraction can occur.
How would you know if you have junctional tachycardia (AV node tachycardia) in an ECG?
no p waves (in lead II) or retrograde p waves in lead III
What is the bpm of a junctional (AV nodal) escape rhythm?
40-60bpm
What bpm is considered an accelerated junctional rhythm?
60-100bpm
What bpm is considered junctional tachycardia?
100+ bpm AV nodal rhythm
Slow rate of 35 beats/min could indicate which type of rhythm?
Can be seen after cardiac arrest
IDIOVENTRICULAR ESCAPE RHYTHM or from cardiac myocytes in ventricles (wide complex originating deep in ventricles)
What could a wide QRS complex indicate?
rhythm origination deep in ventricles
What would an accelerated idioventricular rhythm look like?
faster than 35 bpm, deep QRS complex, can occur after given thrombolytics or after an artery opened in cath lab
Can accelerated ACCELERATED IDIOVENTRICULAR RHYTHM perfuse the heart?
yes
What is the normal QRS duration?
Normal QRS duration equal to or < 120 milliseconds (ms)
What will happen to the normally left leaning vector axis in a right bundle branch block?
depolarization will take longer in the right ventricle and the forces at the end of the depolarization will be directed to the right ventricle.
What happens if there is a delay in ventricular signal due to bundle branch block?
-depolarization takes longer which widens QRS >100 ms and the QRS axis may change and the vector may shifted to last part of ventricles to be depolarized
What is the time frame of QRS complex to indicate a BBB?
BBB QRS complex > 120 ms (3 boxes)
With a bundle branch block (BBB), how does the depolarization of each ventricle compare?
The right and left ventricle are out of phase
One ventricle polarizes slightly later than the other ventricle, causing “two joined QRS’s”
The widened QRS is a combination of both QRS complexes with twin peaks
Which bundle block?
Right BBB, the right ventricular depolarization delayed
Which bundle branch?
Left BBB, left ventricle depolarization delayed
Right Bundle Branch occurs with conditions that affect which side of the heart?
right
Pulmonary disease, COPD, pulmonary hypertension, atrial septal defect
Pulmonary disease, COPD, pulmonary hypertension, atrial septal defect are all conditions that can lead to which type of BBB?
Right BBB
RBBB is not uncommon as may not be significant if less than seconds.
120 seconds
maybe see in children and young adults
What is could one see on ECG of V1 and V6 of RBBB?
rSR’ in lead V1, rabbits ears
▸ Slurred S wave in V6
Which BBB is usually a marker of underlying heart disease and degeneration of the conducting system?
Left BBB
left ventricular hypertrophy, valvular heart disease, mitral or aortic valve disease, cardiomyopathy, coronary artery disease, injury following cardiac surgery or valve replacement can all display which type of BBB morphology on ECG?
Left BBB
Anterior wall can damage the conducting system leading to a bundle branch block. This is a worrisome finding and patients need to be watched for development of heart block.
myocardial infarction
The presence of the left bundle branch block can changes of a myocardial infarction. If a patient presents with a new left bundle branch block and symptoms concerning for myocardial infarction then you treat/do not treat them as if the patient has a myocardial infarction.
obscure
treat
What type of QRS morphology will be demonstrated on ECG with L BBB?
lead V 1 shows a wide QS complex and lead V 6 shows a wide R wave
L BBB
no rabbit ears in V1 or V2
Atrioventricular block divided into 3 divisions, which are?
first, second, and third degree block
Which nodel tissue is considered the gatekeeper?
AV node
What is it called if the signal is going around AV node?
Bundle of Kent or accessory pathway
What is happening with conduction and PR interval as concerning a first degree heart block?
Delay in conduction between the atria and the ventricles
▸ Prolonged PR interval that exceeds 200 ms (5 boxes)
▸ Delay usually occurs in the area of the AV node
How can you tell the difference between a first degree and other degree heart block?
All atrial impulses are conducted to ventricles, each P wave has a corresponding QRS complex, even thought the PR interval is prolonged
What kind of treatment is needed for first-degree AV block?
By itself does not require any specific treatment, only stop treatment if causing first-degree block
What occurs with a second-degree AV block?
Not all atrial impulses are conducted to the ventricles
What are the two types of second-degree block called ?
Mobitz Type I (Wenckebach) second-degree AV block
▸ Mobitz Type II second-degree AV block
What is occuring with conduction in a Mobitz type I-(Wenckebach)-heart block?
Conduction of atrial impulses to the ventricles is progressively delayed because of AV node being refractory
P-R interval progressively lengthens
Eventual failure of conduction of an atrial impulse to the ventricles—dropped QRS
Grouping beating
Does Mobitz type I (Wenckebach) second degree heart block require treatment?
Does not require treatment
Describe the conduction of a Mobitz type II second degree heart block?
Atrial impulses intermittently fail to be transmitted to the ventricles, unpredictable
▸ P-R interval does not lengthen, no progressive conduction delay
Problem is usually located in the bundle of His or more distal
Requires pacemaker
When you see a dropped QRS with a stable PR interval (no progressive lengthening), think of which heart block?
mobitz type II
Does a Mobitz type II heart block require treatment?
Yes, pacemaker
Describe a third degree heart block (complete AV heart block):
No atrial impulses conduct to ventricle
Atria and ventricles are depolarized by their respective pacemakers which are independent of each other (can have regular rhythms seperate from eachother)—AV dissociation
Atrial rate almost always faster than ventricular rate
QRS/ventricular depolarization originates distal to the block
What is the treatment for a thrid degree (complete AV) heart block?
pacemaker
How is the morpholgy of QRS dependent on origin in the ventricles?
▸ Origin may be in a AV junction, his bundle, bundle branches or Purkinje system
Narrow complex, QRS <120 ms (more proximal in the ventricle)
Wide complex, QRS > 120 ms (further down in the ventricle)
In reference to the diagram, do not forget to look for hidden P waves in the QRS complex
How does an MI possibly cause a heart block?
By damaging the AV node
Causes of Heart Block:
Myocardial infarction
▸ Electrolyte abnormalities, hyperkalemia
▸ Medications, digoxin, beta blocker, calcium channel blocker
▸ Iatrogenic, cardiac surgery, ablation near AV node
▸ Degeneration of conducting system, don’t get old!!!!!
▸ Lyme disease
Lyme disease is classic for causing which cardiac morphology?
Heart Block
What are some possible treatements for heart block:
- Discontinue medication that could be inducing heart block
- Correct electrolyte abnormalities (correct elevated K+)
- Treat MI, reestablish perfusion
- transcutaneous pacer
- transvenous pacemaker
What are 3 types medications that could induce heart block?
digoxin, beta blocker, calcium channel blocker
Which coronary artery usually supplies the AV node?
right coronary artery
What type of process is considered when evaluating timing for putting in a pacemaker (emergency pacemaker placement or urgent such as the next day)?
It would depend on the hemodynamic compromise?
Normal BP- urgent, could wait a little
patient diaphoretic and pale with altered mental status and blood pressure of 70- emergency pacemaker placement
What medication could be given if treating a Mobitz type II or third-degree heart block that requires pacemaker?
atropine
-decreases refractory period of AV node- speeds up impulses through AV node
may be helpful if high vagal tone causing block-increases conduction through AV node
What medication to try if the block is occuring at His Bundle or more distal?
Try atropine but may need dopamine or epinephrine
What are the 3 types of pacemakers?
Transcutaneous pacing (emergency, acute need)
▸ Temporary transvenous pacemaker (normally in subclavian)
▸ Permanent pacemaker
What type of wave is the red arrow pointing to?
pacer spike from a pacemaker
What type of bundle branch block?
R BBB
rabbit ears in V2
Slurred S wave in V6
(can be associated with COPD)
At first glance patient has a right bundle branch block. On closer inspection patient has a second-degree block with a 2:1 ratio of P waves to QRS complexes. The P waves are buried in the T waves.
The QRS is wide due to right bundle branch block. This finding increases the likelihood that the block here may be infranodal, but does not prove it. This may likely be a second-degree type 2 block and require a pacemaker.
junctional block
no p wave
went form QRS to T wave
(if there is a QRS complex w/o P wave- think junctional rhythm block)
