lecture 2:

Basic cardiac arrhythmia and their sources

1. Anatomy of the heart

2. Normal function of the heart

Normal rhythm 60 beats/min: determined by the SA node

=> 100.000 beats per day.

:delay of the signal

2. Normal function of the heart

conduction of a wavefront
refraction: during the wavefront: no new wave can be excited
resting state: new wave can arrive

Single cell

2D tissue

2. Normal function of the heart

Colliding waves annihilate

2. Normal function of the heart

During normal rhythm => ECG

2. Normal function of the heart

3. Cardiac arrhythmia

Ischaemic heart disease: includes sudden cardiac death which is caused by arrhythmias
Stroke can also be caused by cardiac arrhythmia: e.g. atrial fibrillation

3. Cardiac arrhythmia: 3 main different types of mechanisms

A. Rotors or functional reentry

Rotors are waves of cardiac excitation like a tornado causing cardiac arrhythmia (Pandit and Jalife, Circulation research (2013))

Rotors act like a source and take over the normal rhythm

Anatomical reentry are waves of cardiac excitation rotating around an obstacle (scar tissue, veins, etc )

B. Anatomical reentry

3. Cardiac arrhythmia: 3 main different types of mechanisms

Focal sources are waves with most likely a centrifugal activation pattern

C. Focal sources

3. Cardiac arrhythmia: 3 main different types of mechanisms

3. Cardiac arrhythmia: fast and slow

Reentry: the period is usually much faster than the period of the SA node and takes over the normal rhythm (mechanism A-B)
Focal source: can also be very fast, but depends on the type of arrhythmia (mechanism C)
There exist also slow arrhythmia: bradyarrhytmia, but they have different mechanims

3. Cardiac arrhythmias: treatment

Functional and anatomical reentry

Rotation is only possible is the lenght of the ring (L) is longer than the product of the refracory period and velocity of the wave: L> Rv

3. Cardiac arrhythmias: treatment

Functional and anatomical reentry: drugs

L > Rv

so we need a drug which

increases R: Class III anti-arrhythmtic class

increases v:? Some drugs decrease v

3. Cardiac arrhythmias: treatment

Functional and anatomical reentry: ablation

Ablation: cut the reentry path

3. Cardiac arrhythmias: treatment

Focal source: ablation

Ablation: ablate the source

3. Cardiac arrhythmias: types

A. Supraventricular arrhthymias

A1. Atrial Flutter & Atrial Tachycardia

A2. Atrial fibrillation

A3. AV nodal reentrant tachycardia

etc

3. Cardiac arrhythmias: types

A1. Atrial Tachycardia:

AT is a regular arrhythmia
Symptoms may include palpitations, feeling lightheaded, sweating, shortness of breath, and chest pain.
AT is a common cardiac arrhythmia: incidence of 2.3 per 1000 people. Also, radiofrequency ablation of AF may result in AT.
Ablation of cardiac arrhythmia is one of the most often performed procedures in cardiac electrophysiology.
Different types of sources possible for this type of arrhythmia:

focus
functional reentry or localized reentry
macro-reentry

real example of 1 .localized reentry

A1. Atrial Tachycardia

Focal sources (3)

Anatomical reentry (2)

(e.g. reentry around mitral valve)

A1. Atrial Tachycardia

Atrial fibrillation (AF): will be the most common disease in the West causing a sixfold increase in stroke risk, leading to anxiety, depression, and reduces individuals' quality of life
Treatment: ablation: burning away different areas of the heart: only about 50% success rate!
Reason for poor success: the underlying mechanism is heatedly debated
Is AF due to rotors? World leading groups have opposing views:

A2. Atrial fibrillation

Treatment is unclear:
E.g. FIRM (Focal Impulse and Rotor Modulation) approach is being used in the clinical practice to detect rotors by using phase mapping (Narayan et at J Am Coll Cardiol, 2014)
Initially very high success rates (90%) were reported for patients with persistent AF.
The company which developed FIRM for clinical practice (Topera Inc.) was sold for 250 million dollar to Abbott
However, newest results show that FIRM does not work, results are again back to 50% success rate for persistent AF