Flashcards in Clinical treatment of Arrhythmias Deck (29):
Describe initiation of the cardiac cycle "P wave"
Initiation of the cardiac cycle normally begins with initiation of the impulse at the sinoatrial (SA) node.
A resulting wave of depolarization passes through the right and left atria, which produces the P wave on the surface ECG and stimulates atrial contraction.
Describe the physiology of what happens after the P wave
Following activation of the atria, the impulse proceeds to the atrioventricular (AV) node, which is the only normal conduction pathway between the atria and the ventricles.
The AV node slows impulse conduction which allows time for contraction of the atria and the pumping of blood from the atria to the ventricles prior to ventricular contraction.
Conduction time through the AV node accounts for most of the duration of the PR interval.
Which part of the PQRST beats is the impulse passing through the bundle of His?
Just below the AV node, the impulse passes through the bundle of His. A small portion of the last part of the PR interval is represented by the conduction time through the bundle of His.
Which part of the PQRST beats is the impulse passing through the bundle branches?
After the impulse passes through the bundle of His, it proceeds through the left and right bundle branches. A small portion of the last part of the PR interval is represented by the conduction time through the bundle branches.
What occurs during the QRS complex?
Atrial repolarization and relaxation
The T wave on the ECG represents the _____________
repolarization and relaxation of the ventricles.
Arrhythmias fall into two categories... _____ and ____
Either your rhythm is too slow or too fast.
Bradyarrhythmias and Tachyarrhythmias
Where in the conduction system can problems develop?
Below the AV node
Conditions that are examples of – sinus node dysfunction
* sinus bradycardia
* sinus arrest/pause
* tachy-brady syndrome
* chronotropic incompetence- inability to
mount age-appropriate HR with exercise
Where in the conduction system can problems of bradyarrhythmias develop?
1) SA node
2) AV node
- first degree AV block
- Mobitz I 2nd degree AV block (Wenkebach)
3) below the AV node (infranodal/His Purkinje system)
- Mobitz II 2nd degree AV block
- complete heart block
First-Degree AV Block
- AV conduction?
- PR interval?
AV conduction is delayed, and the PR interval is prolonged (> 200 ms or .2 seconds)
First-degree AV block can be thought of as a delay in AV conduction, but each atrial signal is conducted to the ventricles (1:1 ratio)!! Between P wave and QRS interval
Third degree heart block AKA
Complete Heart block
*complete dissoc. betwen waves thorough V node into the ventricles
Long term treatment of arrhythmias
Tachyarrhythmias fall into 2 categories:
1. Above Ventricle
- Supraventricular Tachycardias (SVT)
- Ventricular Tachycardia
- Ventricular Fibrillation
SVT can be classified under two categories:
What do they consist of?
- 1 P : 1 QRS
Atrial Fibrillation (AF)
A type of Irregular SVT where there are no discrete P waves
Multifocal Atrial Tachycardia
MAT: a type of irregular SVT where there are 3 or more P waves
Atrial flutter (AFL)
AFL: a type of irregular SVT where one would see variable conduction and flutter waves
Types of Regular SVT
1. sinus tachycardia,
2. AV nodal reentrant tachycardia,
3. atrioventricular reentrant
5. atrial flutter (can also be irreg)
6. atrial tachycardia,
7. junctional tachycardia
*management for these hinges on their diagnosis!
How are Irregular SVT treated?
control their rates (assess symptoms),
Then use antiarrhythmics, or cardiovert them (hemodynamic collapse)
How are regular SVT treated?
first step is both a diagnostic and treatment option, which is to use adenosine, a drug that blocks the AV node very transiently.
Treatment of Atrial fibrillation
? Cure: Ablation
What is the most common atrial arrhythmia?
- also the most complicated
Causes of A fib (AF)
Mitral valve Disease
Lone AF 14%
2 ways to control rhythm
- Class IC agents
- Class III agents
- anticoags (bc of risk for thrombo)
- DC shock
Ways to control rate
Amiodarone - can be used as a rate-controlling agent, especially in setting of decompensated heart failure.
What happens if pts fail medications for rhythm control?
Use catheter ablation - target triggers of atrial fib.
- 95% cure rate for Atrial flutter and low risk
If you are uncertain when making a diagnosis on an arrhythmia, what should you err on?
err on treating the arrhythmia as a ventricular arrhythmia
- If pt has coronary artery disease, 90% of the time the WCT is VT