| Question |
 |
|
| Answer |
|
|
| Arrhythmia |
an abnormality of impulse initiation, impulse conduction or both |
| Normal automaticity |
arrhythmias associated with normal automatic pacemakers |
| abnormal automaticity |
arrhythmias associated with non pacemaker cells that develop automaticity |
| triggered activity |
oscillations in membrane potential that trigger an action potential |
| Normal SAN pacemaker |
60-100 bpm |
| Atrial conduction fibers |
60-80 bpm |
| AV junction |
40-60 |
| Ventricular Purkinje |
20-40 |
| True normal pacemaker |
SA node |
| What makes the latent pacemakers emerge? |
High parasympathetic tone
High catecholamine concentration
hypoxemia
ischemia
electrolyte distrbances
drug toxicities |
| Abnormal automaticity |
tissue that is not normally automatic becomes automatic; often cannot be overdrive suppressed |
| Triggered activity |
early afterdepolarizations
delayed afterdepolarizations |
| EAD |
occur before full phase 3 repolarization |
| DAD |
occur after phase 3 repolarizations |
| Digoxin |
Blocks Na/K pump. Dig toxicity will lead to DADs and has increase in intracellular Na+ which will inhibit Na/Ca pump leading to increased Ca in the SR. |
| 1st degree block |
every pulse conducts |
| 2nd degree block |
some, not all pulses conduct |
| 3rd degree block |
no pulses conduct |
| 2nd degree type I |
Wenkebach; progressive prolongation thru the av node with an eventual dropped beat |
| 2nd degree type II |
Mobitz II; dropped beats without the prolongation of the PR interval |
| 2:1 Morbitz block |
dropping every other beat. Every other P wave has a QRS |
| 3:1 Morbitz |
3 P's for every QRS |
| What are some of the mechanisms that could contribute to block in the AV node? |
block Ca+ channel
Increase vagal outflow
Digitalis
Hyperkalemia
Adenosine |
| Re-entry |
circus movement; an impulse that does not die out, it instead continues to circulate and re-excite tissue |
| Conditions that are necessary for re-entry to occur. |
1. unidirectional block, or transient block
2. slowed conduction over an alternate pathway
3. Proximal re-excitation |
| Re-entry may be promoted by ______________ |
things that slow conduction velocity, shorten the refractory period or a combination of both |
| Examples of random re-entry |
Ventricular Fibrillation |
| Is re-entry ordered or random? |
both |
| Re-entry may accur around _______ or it may be ______________. |
anatomical;functional |
| Classic example of re-entry |
wolff-parkinson-white syndrome |
| WPW |
pre-excitation; has an accessory pathway; result is supraventricular tachycardia |
| Pre-excitation shows what kind of wave? |
Delta wave |
| 3 Examples of re-entry |
V-Fib
A-Fib
WPW |
Poultry
