Arrhythmias * Flashcards
What’s bradycardia?
Abnormally slow rhythms.
What’s tachycardia?
Abnormally fast rhythm.
Supraventricular – involving AV node
Ventricular – involving His-Purkinje system
What’s the native pacemaker?
SA node. It sets the heart rate.
What’s a latent pacemaker?
Harbours potential to act as pacemakers if needed.
What’s overdrive suppression?
Cells with the fastest rhythm dominate and directly suppress other automatic cells.
What 3 factors determine the intrinsic firing rate of the conduction pathway?
- Rate of phase 4
- Maximum Negative RMP
- Threshold Potential
What are the main abnormalities of impulse initiation that leads to arrhythmias?
- altered automatic
- abnormal automaticity
- triggered activity
What happens when there’s increased SA automaticity?
There’s a steeper depolarization during phase 4. AP is shifted to a more negative voltage, reaching threshold earlier.
It’s controlled by the automatic nervous system. (Sympathetic Nervous System)
What happens when there’s decreased SA automaticity?
There’s a more gradual and longer phase 4 depolarization. There’s a more negative diastolic potential. Less negative threshold potential.
It’s controlled by reduced sympathetic and increased parasympathetic.
What’s an escape beat?
It’s an impulse initiated by a latent pacemaker - due to a slow SA node rate.
What’s an escape rhythm?
It’s a continued series of escape beats due to persistently impaired SA node.
Increased PNS yields what?
At the SA node leads to decreased Simms activity. So AV node takes over. Ventricular pacemaker sites take over.
What’s an ectopic beat?
It’s an enhanced impulse firing in a latent pacemaker.
What’s ectopic rhythm?
It’s a sequence of ectopic beats.
What’s the difference between an ectopic beat and an escape beat?
An ectopic beat is a premature impulse whereas an escape beat is late neared which terminated a pulse caused by slow sinus rhythm.
What’s abnormal automaticity?
Arise from cells that do not usually possess automaticity. Myocardial cells outside of the specialized conduction system acquire automaticity and spontaneously depolarize