lecture 2:

Basic cardiac arrhythmia and their sources

1. Anatomy of the heart

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

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:
  1. focus
  2. functional reentry or localized reentry
  3. 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

A2. Atrial fibrillation

A2. Atrial fibrillation

A2. Atrial fibrillation

A2. Atrial fibrillation

B. Ventricular arrhthymias

B1. Ventricular tachycardia

B2. Ventricular fibrillation

3. Cardiac arrhythmias: types

4. Computer modeling: integrative model of the human heart

4. Computer modeling: integrative model of the human heart

  • Velocity (value,+-)
  • How initiate wave
  • Spiral properties (wavelength,period)
  • Vortex dynamics + chaos
  • Mechanisms of initiation of spirals
  • Control (remove from the heart)
  • Not only heart