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Arrhythmias. Cardiac dysrhythmia. Cardiac dysrhythmia (arrhytmia) Abnormal electrical activity in the heart. Electrical conduction system of the heart. Sinus node. AV node. Bundle of His. Left bundle branch. Internodal pathways. Right bundle branch. Purkinje fibers.

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cardiac dysrhythmia
Cardiac dysrhythmia
  • Cardiac dysrhythmia (arrhytmia)
  • Abnormal electrical activity in the heart
electrical conduction system of the heart
Electrical conduction system of the heart

Sinus node

AV node

Bundle of His

Left bundle branch

Internodal pathways

Right bundle branch

Purkinje fibers

the effect of autonomic nervous system
The effect of autonomic nervous system

sympathetic parasympathetic

heart rate (chronotropic) b1 increases decreases

contractility (inotropic) b1 increases decreases

conduction in AV node b1 increases decreases

(dromotropic)

excitability (bathmotropic) increases decreases

slide7

Phase 4

Phase 4

phases of the cardiac action potential
Phases of the cardiac action potential
  • Phase 0 – rapid depolarization phase - Na+ channels
  • Phase 1 – K+ and Cl- channels
  • Phase 2 – „plateau“ - Ca2+ channels
  • Phase 3 – rapid repolarisation - K+ channels
  • Phase 4 – resting potential (diastole) - K+ channels, 3Na+-2K+-ATPase, Ca2+-ATPase, 3Na+-1Ca2+-exchager
sa node action potential
SA node action potential

Phase 4

spontaneous diastolic depolarisation

Ca2+ channels

slide10
ECG

P wave – atrial depolarisation

PR segment – delay in the AV node

QRS complex – ventricular depolarisation

T wave – ventricular repolarisation

ethiology
Ethiology
  • Ischaemia, acidosis – coronary artery disease
  • Ion disbalance – hypo-/hyperkalemia...
  • Heart diseases – myocarditis, cardiomyopathies
  • Autonomic nervous system dysbalance
  • Thyroid diseases – hypo-/hyperthyreosis
  • Toxins and drugs – caffeine, digitalis
  • Other diseases – anaemia
  • Genetic mutation
  • Age
mechanisms of arrythmias
Mechanisms of arrythmias
  • Increased automaticity
    • Increased normal automaticity (in SA node)
    • Abnormal automaticity (ectopic focus)
  • Triggerd activity
    • Early afterdepolarization
    • Delayed afterdepolarization
  • Reentry
increased automaticity
Increased automaticity
  • Increased automaticity - classification
    • Increased normal automaticity (in SA node)
    • Abnormal automaticity (ectopic focus)

Automaticity –ability to generate impuls

  • Increased normal automaticity– hyperirritability of SA node – faster activation of SA node
  • Abnormal automaticity (ectopic focus) – hyperirritability of other myocardial cells (e.g. ventricular cells)
slide14

threshold membrane potential

  • Mechanisms

Faster spontaneous depolarization

(catecholamines)

More rapid slope of spontaneous depolarization (SA) or resting potential (e.g. ventricular cells)

Increased resting membrane potential

(ischemia – lower activity of Na/K-ATPase)

 resting potential leads to earlier threshold membrane potential

Decreased threshold membrane potential = earlier threshold membrane potential

triggerd activity
Triggerd activity

Characterization: abnormal phase of repolarization in the previous impuls leads to earlier new depolarization

2 types:

Early afterdepolarization

  • New depolarization appears in phase 3 of previous action potential
  • Cause: slower repolarization – e.g. because of hypokaliemia

Delayed afterdepolarization

  • New depolarization appears in phase 4 of previous action potential but sooner than normal
  • Cause:  intracellular Ca concentration (digitalis)
reentry
Reentry
  • Circulation of the impulse

Possible mechanisms

  • Shorter refractory period
  • 2 places in the heart are connected with 2 ways for impulse. In the case of blocade of one way (extra beat, scar) – impulse is conducted by one way, returns by the second one and starts circulate
  • The way for impulse is longer than refractory period (hyperthrophy)
  • Atrioventricular reentry

impulse returns through accessory pathway

(WPW syndrome)

inherited arrhytmias
Inherited arrhytmias

Long QT syndrome

  • Mutations (AD) of ion channels (K+, Na+, Ca2+ ) genes
  • Ventricular extra beats, ventricular tachycardia
  • Unconsciousness, synkope, ventricular fibrilation, sudden death
  • SADH – sudden arrhytmia

death syndrome

signs
Signs
  • Electrical
    • Changes in the ECG
  • Haemodynamic
    • Decreased preload
    • Decreased minute heart output
  • Clinical
    • Syncope
    • Palpitation
    • Sudden cardiac death
classification
Classification
  • Mechanism
    • Disorders of impulse generation
    • Disorders of impulse conduction
    • Combined
  • Site of origin
    • Supraventricular
      • Sinus
      • Atrial
      • Junctional
    • Ventricular
  • Rate
    • Tachycardia
    • Bradycardia
sinus arrhytmias
Sinus arrhytmias
  • Sinus tachycardia
    • rate > 100 bites/min. (normal 60 – 100bites/min.)
    • physiological – newborns and children, physical activity, stress
    • drugs – catecholamines
    • diseases – hyperthyreosis, anaemia...
  • Sinus bradycardia
    • rate < 60 bites/min.
    • physiological – sportsmen
    • diseases – hypothyreosis...
sinus arrhytmias1
Sinus arrhytmias
  • Premature sinus contraction (Sinus extra beat)
  • Sinus arrhytmia
    • physiological – breathing
  • Sick sinus syndrome
    • inherited
    • coronary artery disease
    • hypertension
    • idiopathic
  • Sinus arrest
atrial arrhytmias
Atrial arrhytmias
  • Premature atrial contraction (extra beat)
  • Atrial rhythm
  • Atrial (supraventricular) tachycardia
  • Atrial flutter
  • Atrial fibrilation
junctional arrhytmias
Junctional arrhytmias
  • Premature junctional contraction (extra beat)
  • Junctional rhythm
  • Junctional (supraventricular) tachycardia
ventricular arrhytmias
Ventricular arrhytmias
  • Premature ventricular contraction (extra beat)
  • Accelerated idioventricular rhythm
  • Ventricular tachycardia
  • Polymorphic ventricular tachycardia
  • Ventricular fibrilation
heart blocks av blocks
Heart blocks (AV blocks)
  • 1st degree
  • 2nd degree
    • type 1 (Mobitz I, Wenckenbach)
    • type 2 (Mobitz II)
  • 3rd degree
slide28

Left bundle branch block

Right bundle branch block