Question | Answer |
Arrythmia | an abnormality of impulse initiation, impulse conduction or both |
SA node rate of pacemaking | 60-100 bpm |
AV junction rate of pacemaking | 40-60 bpm |
Purkinje fibers | 20-40 bpm |
Tachycardia | >100 bpm |
Bradycardia | <60 bpm |
Abnormal automaticity | Arrythmia associated with non-pacemaker cells that develop automaticity |
Triggered activity | Oscillations in membrane potential that trigger an action potential |
Sinus arrythmia | Inspiration causes an acceleration and Expiration causes a deceleration, NORMAL |
Abnormal automaticity depolarizes tissues by | inactivating fast Sodium channels |
Can you overdrive suppress abnormal automaticity? | NO |
Early afterdepolarization can lead to a | Torsades de pointes |
Delayed afterdepolarization leads to a | ITI- Calcium driven, transient inward current |
1st degree block | Consistent prolongation of the PR interval but all impulses get through. |
Two types of 2nd degree block | Wenckebach (also MobitzI) and Mobitz (also called MobitzII) |
Wenckeback | Progressive prolongation through the AV node with an eventual dropped beat----prolonged PR interval |
Mobitz | Dropped beats without prolongation of the PR interval |
Wenckebach reflects an abnormality in which region? | AV node |
Mobitz reflects an abnormality in which region? | His bundle and/or bundle branches, usually an anatomical lesion and much worse! |
3rd degree block | Complete block through the AV node and another latent pacemaker takes over |
What can cause an AV block | Increased vagal tone, Calcium channel block, Beta-blocker, Digitalis, Hyperkalemia |
Re-entry | An arrhythmogenic mechanism in which the impulse does not die out but instead continues to circulate and re-excite tissue |
Conditions for re-entry to occur | Unidirectional block, Slowed conduction over an alternate pathway, Re-excitation of tissue proximal to the block |
Re-entry is promoted by things that | Slow conduction velocity, shorten the refractory period or a combination of both |
Wolf-Parkinson-White syndrome | Patients have an accessory pathway that uses Sodium channels (fast!) instead of the normal Calcium channels (slow) used by the AV node- causes premature excitement and tachycardia |
Wolf-Parkinson-white EKG | Delta wave, retrograde P waves and wdie QRS intervals |