136 Tachycardia Flashcards
1
Q
Diagram of slow and fast pathways in Sinus, Premature Atrial Beats, AV nodal echo, AVNRT
A
2
Q
Atrioventricular Nodal Reentrant Tachycardia (AVNRT)
A
- The myocardium surrounding the AV node is called the transitional zone
- electrical properties are intermediate between atrial and AV nodal cells
- This zone can have variable conduction properties leading to different “pathways” of the AV node
- Fast pathway: Rapid conduction, long refractory period
- Slow Pathway: Slow conduction, short refractory period
AV nodal reentry initiation
- Sinus rhythm normally conducts through the fast pathway to the ventricle
- A premature beat (usually atrial) occurs while the fast pathway is still refractory
- The slow pathway is able to conduct this beat to the ventricle
- When the activation reaches the end of the slow pathway, the fast pathway has recovered and can then conduct retrograde (backwards) to the atrium
3
Q
Paroxysmal Supraventricular Tachycardia (PSVT)
A
- REGULAR, NARROW-QRS TACHYCARDIA
- AV nodal reentrant tachycardia (AVNRT)
- Atrio-ventricular reentrant tachycardia (AVRT)
- Ectopic atrial tachycardia (AT)
- Symptoms
- wNone
- wHeart Racing
- wChest discomfort
- wDyspnea
- wLoss of Consciousness (syncope)
- wHeart failure
- wIncessant tachycardia can cause a tachycardia mediated cardiomyopathy
- wAborted Sudden Death
4
Q
Atrioventricular Reentrant Tachycardias (AVRT)
A
AVRT Uses Atrioventricular Accessory Pathways
- Anomalous muscle bundles that connect the atrium and ventricle across the valve (tricuspid or mitral)
- Also known as bypass tracts, Kent bundles
- Congenital but may lose conduction with age
- Can sometimes be seen on ECG (“preexcitaion” “delta wave”)
- Ventricle is activated earlier than expected
- Slurring of QRS complex
- Circuit includes the accessory pathway, AV node/conduction system and intervening atrial and ventricular tissue between these structures
- Slow conduction zone is usually the AV node
- Circuit can spin in either direction
5
Q
delta wave
A
6
Q
Atrial Tachycardia + Other atrial atachycardias
A
- Focal tachycardia confined to the atrium
- does not require the AV node
- Can be sustained or not, paroxysmal or incessant
- Mechanisms
- Triggered
- Automatic
- Micro-reentry: Small circuit that appears focal
Others:
- Sinus Tachycardias (usually have a physiologic cause)
- Inappropriate Sinus Tachycardia if no cause
- Multifocal AT
- 3 or more P wave morphologies, irregular
- can be confused with atrial fibrillation
- usually seen in pulmonary disease
7
Q
Atrial Fibrillation and Atrial Flutter
A
- Atrial fibrillation is the most common arrhythmia and comprises about half of all supraventricular tachyarrhythmias seen clinically
- Atrial flutter comprises about 10%
- Atrial fibrillation is often seen in patients with atrial flutter
- Fibrillation: atrial rate >350 bpm, very irregular and disorganized
- Flutter: atrial rate generally 240-350 bpm, organized an regular
- Can be slower on antiarrhythmic drugs or after ablation
8
Q
Atrial Fibrillation Mechanisms (3)
A
9
Q
Definitions of V Tach (and categories)
A
- Non-sustained Ventricular Tachycardia: ≥ 3 beats, <30 seconds, hemodynamically tolerated
- Sustained: > 30 seconds
The significance of ventricular arrhythmia is dependent on the rhythm and the substrate
10
Q
Idiopathic Ventricular Tachycardia
A
11
Q
Torsades de Pointes
A
- Subset of Polymorphic VT
- Polymorphic VT in setting of long QT interval
- Translation “twisting of points”
12
Q
LONG QT Syndrome
A
13
Q
VENTRICULAR FIBRILLATION
A
- §Primary
- §non-reversible causes (cardiomyopathy, congenital electrical disorders)
- §Secondary
- §Acute myocardial infarction
- §Ischemia
- §Electrocution
- §Severe electrolyte disturbances
- §Drugs
- §Symptoms- syncope/sudden death
- §Usually does not self-terminate
- §Treatment
- §Treat cause, if secondary
- §Implantable cardioverter defibrillator(ICD)
- §Agents to control recurrences (mostly in conjunction with ICD)
- Mechanism
- •Depends on substrate
- Cardiomyopathy: Scarring causes reentry
- Primary electrical abnormalities: Functional reentry (see later slides)
- Same for secondary VF