EP I and II Flashcards
what starts cardiac rhythms?
automaticity, triggered activity or reentry
what are examples of abnormalities in automaticity?
increased: inappropriate sinus tachycardia, junctional tachycardia
decreased: sick sinus syndrome (tachy-brady and syndrome of chronotropic incompetence)
no intrinsic automatic activity: ectopic atrial tachycardia and accelerated idioventricular rhythms
what are early after depolarizations?
after potentials occurring soon after initiation of AP
causes: acidosis, hypoxia, hypokalemia
what are delayed after depolarizations?
occur after EAD in phase 4
causes: digitalis toxicity, exercise induced tachycardia in normal
what is reentry?
sudden initiation and termination of tachycardia
major cause of SVT (other than AFib) and almost all VT
what are the three key elements needed for reentry occurrence?
common upper and lower pathways with two separate limbs
different signal conduction velocities in the two limbs
longer refractory period in faster conducting limb
describe innervation of SA node
right sided sympathetic and parasympathetic with parasympathetic predominating (atropine leads to increased HR)
describe innervation of AV node
left sided sympathetic and parasympathetic vagus
what is orthodromic tachycardia?
left posterior AP in patients with WPW
narrow or normal QRS - normal ventricular activation uses AV node for antegrade conduction and accessory for retrograde
most common type of AV reentry tachycardia
what is antidromic tachycardia?
left posterior AP in patients with WPW
wide or pre-excited QRS
uses accessory pathway for antegrade limb and AV node for retrograde
what are causes of sinus bradycardia?
meds (beta-blockers and digoxin)
metabolic problems (electrolyte abnormalities and hypothyroidism)
hyper vagal state
sinus or AV nodal dysfunction (late sequelae of cardiac surgery, cancer chemotherapy, radiation therapy)
what are causes of sinus tachycardia?
stress, fever, pain or blood loss/deyhdration
thyroid disease and drug use
what is sick sinus syndrome?
tachy-brady
sinus pauses greater than 3 seconds occasionally occur in sinus node unable to increase HR in response to exercise
how can you treat atrial flutter?
pace termination and curative ablation in region of isthmus
what is atrioventricular nodal reentry tachycardia?
a paroxysmal SVT consequence of reentrant circuit formed by two inputs into AV node and upper and lower pathway
it has a very short QRS to P wave
