Tachycardia lecture and module

Question 1

What causes a wide tachycardia?

Answer 1

Electrical signal has to travel through the slowly conducting ventricular cells, which takes a longer time

Question 2

How does increased automaticity work?

Answer 2

Decreased parasympathetic drive
Increased phase 4 slope
The threshold is more negative, and the resting membrane potential is more positive – more easy to get an AP

Question 3

Atrial fibrillation

Answer 3

Most common sustained arrhythmia
Atria depolarize at 400-600 BPM with irregular conduction to the ventricles
Irregular RR intervals
No P waves (can’t see atrial activity)

Question 4

What is triggered activity

Answer 4

During the partial refractory period, oscillations in the membrane potential can trigger abnormal APs which can lead to a tachy

Question 5

Atrial flutter

Answer 5

Re-entry circuit that occurs entirely in the R atria
Around 300 BPM
Can be regular or irregular (usually conducts about 2:1)
Sawtooth pattern
Characteristics: > 100BPM, regular rhythm, sawtooth P waves

Question 6

Orthodromic vs antidromic

Answer 6

Ortho: conduction down the AV node is normal
Anti: conduction is backwards through the AV node

Question 7

Wolf-Parkinson-White

Answer 7

Palpitations + pre-excitation
Congenital accessory path (antegrade AV conduction) and tachycardia episodes
Accessory pathway is the Bundle of Kent (antegrade and retrograde)

Question 8

Pre-excitation

Answer 8

Presence of an antegradely conducting accessory path that can pre-depol the ventricles
Will see a delta wave on ECG
Shortened PR interval and widened QRS complex

Question 9

Pre-excited atrial fibrillation

Answer 9

Atrial rate 400-600 BPM
Ventricular rate dictated by the refractory period of the accessory path
Can be so fast that it results in cardiac risk

Question 10

Symptoms associated with tachycardia

Answer 10

Palpitations
Pre-syncope
Syncope
Fatigue
Poor exercise tolerance
Chest pain
Sweating (diaphoresis)
Shortness of breath

Question 11

Everyone with SVT should have what investigation?

Answer 11

Echocardiogram

Want to rule out mitral valve prolapse and congenital valve abnormalities

Question 12

5 waves to evaluate/measure tachycardia

Answer 12

ECG
Holter monitor
Event monitor
Implantable cardiac monitors
Echocardiogram

Question 13

Treatment during a tachy episode

Answer 13

Valsalva
Carotid sinus massage
Diving reflex (face in cold water)
Adenosine
IV AV nodal blocker (beta blocker, calcium channel blocker)
Cardioversion (extreme circumstances)

Question 14

How to prevent tachy episodes

Answer 14

Nothing and treat as they come
AV nodal blocker (beta blocker, calcium channel blocker)
Ablation

Question 15

3 general mechanisms of tachycardia

Answer 15

Re-entry
Automaticity
Triggered activity

Question 16

Where is the origin of impulse in
1. Narrow
2. Wide
QRS complexes?

Answer 16

1. Supraventricular

2. May be ventricular

Question 17

3 types of supraventricular tachycardias

Answer 17

Ectopic atrial tachycardia
AVNRT
AVRT

Question 18

Ectopic atrial tachycardia

Answer 18

A form of tachyarrhythmia originating from within the atria, but outside of the SA node
Usually due to a single ectopic focus
Characteristics: HR > 100, regular rhythm, abnormal P wave morphology (not from the SA node)

Question 19

Multifocal atrial tachycardia

Answer 19

More than one ectopic focus of automaticity outside the SA node
At least 3 ectopic foci of automaticity evident on ECG
Characteristics: HR > 100, irregular rhythm, 3 or more unique P waves

Question 20

AVNRT

Answer 20

Both the slow and fast pathways are located in the AV node

Only the AV node is an obligate part of the circuit

Question 21

AVRT

Answer 21

2 arms of the re-entry circuit
One is the AV node, the other is an accessory pathway
The AV node, atrium, and ventricles are all a part of the pathway
P waves can be buried in the QRS complexes (atria being depolarized at the same time as the ventricles)

Question 22

What does it mean if P waves come after the QRS

Answer 22

They are retrograde P waves that come from the bottom of the atrium (not the SA node)