45 Arrhythmias Flashcards
In the SA node is there fast action Na channels?
No–Inward funny current cause low slope then inward Ca does upslope
What is ohm’s law?
current= voltage / resistance
Does the the extracellular current and intracellular current run in the same direction in cell to cell conduction?
No–opposite direction
What are the 2 factors that effect the voltage difference in cell to cell conduction ?
- The amplitude and rate of rise of the action potential
2. The resting membrane potential
What 2 factors that effect the resistance include in cell to cell conduction?
- Gap junctions
2. Myocyte anatomy
What reflects sinus node automaticity?
Heart Rate
What reflects AV nodal conduction time?
PR-interval
What reflects conduction time in ventricles?
QRS duration
What reflects ventricular action potential duration?
QT interval
What is the time from the beginning of an action potential until cell is able to conduct another action potential?
effective refractory period (absolute)
What is the time from end of effective refractory period until cell regains normal excitability?
Relative refractory period
All cardiac arrhythmias occur because of what? 6 examples
perturbed ion channel function
[mutation, ischemia, electrolyte abnormalities, abnormal autonomics, drugs, lightning!]
What is diastolic depolarization? what types of cells can do this?
- automaticity - altered in pathology
2. any cardiac myocyte is capable of it
What type of depolarization occurs before end of previous action potential?
Early afterdepolarization
What type of depolarization occurs after previous action potential is completely finished?
delayed after depolarization
A prolonged action potential can cause what type of abnormal depolarization? How? what can it lead to?
EAD through reactivation of Ca channels
run of spontaneous activity
What specific type of arrhythmia can EAD lead to?
torsades de pointes
Are EAD induced arrythmias more common with fast heart rate?
slow heart rate
K channel genetic mutations lead to? What are these patients predisposed to?
- congenital long QT syndrome 2
2. EADs, arrhythmias, syncope, and sudden cardiac death
What is the main cause of delayed afterpolarizations?
abnormal intracellular Ca handling
Are delayed afterpolarizations more common with slow heart rate?
Fast heart rate–also associated with ischemia
cardiac arrhythmias are due to what?
abnormal impulse conduction
What are the three requirements for re-entry?
- geometry for a conduction loop
- unidirectional conduction block
- slow conduction (the effective refractory period must by less than propagation time around loop)
