Dysrhythmias Flashcards
dysrhythmias
alterations in cardiac rhythm
arrhythmias
loss of rhythm
cardiac dysrhythmias appears as what in ECG?
appear as variations
when is dysrhythmias harmful
when it interfers w/ heart’s pumping ability
what cells possess automaticity
cells of SA node, AV node and purkinje fibers
automaticity
ability to spontaneously generate action potential
normal dysrhythmias include
sinus bradycardia & tachycardia
sinus bradycardia
seen in trained athletes or during sleep
may occur in acute MI or respiratory depression
sinus tachycardia
seen w/ exercise or fever
may occur w/ CHF, MI, hyperthyroidism, certain drugs, hypovolemia
atrial dysrhythmias result from?
abnormal electrical activity in atrium
atrial dysrhythmias causes
mitral stenosis
ischemia
cardiac surgery
hyperthyroidism
alcohol or caffeine consumption
atrial dysrhythmias include
premature atrial contraction
atrial flutter
atrial fibrillation
premature atrial contraction is
d/t
↑automaticity in cells other than SA or AV node (ectopic foci)
atrial flutter
rapid, regular atrial ectopic tachycardia
atrial fibrillation is d/t
multiple uncontrolled, depolarizations of atrium
heart block occurs when?
when there is conduction defect in AV node or bundle branches
kinds of heart block
1st degree AV block
2nd degree AV block
3rd degree AV block
Bundle Branch block
1st degree AV block
delayed conduction through AV node
but
impulses are conducted through ventricles
2nd degree AV block
when some impulses from atria are NOT conducted to ventricles
localized MI in 2nd degree block
infarction in His bundle that has a poor prognosis d/t fewer ventricular contractions => ↓CO
3rd degree AV block
complete AV block
NO atrial impulses are conducted to ventricle
requires pacemaker
stroke-adams attack
sudden brief loss of consciousness from a large drop in cardiac output
bundle branch block
interruption of conduction through bundle branches
- carries impulses to myocardium of ventricles
how does bundle branch block appear in ECG?
wider QRS complex since it DOES NOT affect rhythm, and cells DO NOT contract together
kinds of ventricular dysrhythmias
premature ventricular contraction (PVC)
ventricular tachycardia
ventricular fibrillation
pulseless electrical activity
asystole
PVC cause
ventricular ectopic pacemakers
PVC often occurs when?
secondary to ischemia, infarction or electrolyte imbalances
PVC characterization
broad, distorted QRS complexes and large T waves followed by a compensatory pause where ventricles are unable to respond to incoming SA node impulses
ie. are refractionary
ventricular tachycardia & ventricular fibrillation are considered what?
considered cardiac arrest rhythm since they often DO NOT generate a cardiac output or palpable pulse
ventricular tachycardia treatment
treated immediately w/ defibrillation and CPR
ventricular tachycardia cause
caused by re-entry secondary to ischemia, infarction, fibrosis, dilated myopathy, electrolyte imbalance
ventricular tachycardia characterization
broad, tall QRS complexes, inverted T-waves
rate of 70-250beats/min
ventricular tachycardia can progress to what?
progress to ventricular fibrillation especially if following an MI
when does ventricular fibrillation occur
occurs w/ firing of multiple ectopic foci in ventricles
ventricles in ventricular fibrillation
ventricles quiver but DO NOT contract => no CO
ventricular fibrillation results to what?
=> unconsciousness, absence of pulse, apnea, death
ventricular fibrillation characterization
grossly distorted w/ shallow, unidentifiable waves
pulseless electrical activity
shows electrical activity, but there is no mechanical ventricular fixation or pulse
have corrective and uncorrectable causes
poor prognosis unless corrected
pulseless electrical activity corrective causes
hypovolemia
hypoxemia
hypothermia
acidosis
pulseless electrical activity uncorrectable causes
massive infarction
ischemia during resuscitation
pulmonary embolism
asystole
total absence of ventricular electrical activity and contraction (flat line)
no ventricular depolarization
poor prognosis
ST segment of ECG represents what?
represents repolarization phase of ventricular myocytes
current that creates ST segment is sensitive to what?
sensitive to changes in coronary blood flow and is therefore used to assess myocardial ischemia and infarction
two kinds of ST segment
ST segment depression & elevation
ST segment depression occurs as a result of what?
result of myocardial ischemia
ST segment depression occurs d/t what?
occur d/t slowed repolarization rate secondary to ↓cellular ATP or potassium efflux
mechanism of ST depression
exact mechanism for ST segment depression is not known
cardiac dysrhythmias indicate what?
may indicate alterations in automaticity, excitability, conductivity or refraction d/t ischemia and infarction, electrolyte imbalances, drug effects or defects in conduction
what is common in atrial dysrhythmias
palpitations and tachycardia
premature atrial contraction in ECG
appears as an abnormal P wave - abnormal conduction pathway and irregular heart beat
atrial flutter cause
caused by large circular re-entrant current in atrium at a rate of 300beats/min
- current creates a “sawtooth” pattern
what happens to atrial contribution in arrhythmias?
atrial contribution to ventricular filling is lost and quite often ↓CO
how does ventricle contract in atrial flutter?
ventricle contract regularly but ↑rate (150beats/min) => ↓CO and possibly myocardial ischemia, HF
how does atria contract in atrial fibrillation?
atria contract in a continuous, uncoordinated fashion at 350-600beats/min
ventricle in atrial fibrillation
ventricle do not fill or contract properly => ↓CO, may cause syncope or cardiac arrest
how is blood flow in atrial fibrillation
stasis of blood in atrium => ↑risk of cerebral embolism
heart blocks may be what?
may be:
normal - vagal tone
pathological - ischemia, infarction, fibrosis, inflammation, surgery, potassium imbalance
rhythm in 1st degree AV block
regular
cause of 1st degree AV block
caused by ischemia or MI of AV node, rheumatic fever, myocarditis
how is each region in 3rd degree AV block?
each region controlled by independent pacemakers => regular but dissociated rates
ventricular rhythm in 3rd degree AV block
ventricular rhythm is slow (30-40beats/min)
3rd degree AV block can arise from?
impaired conduction at AV node, His bundle or purkinje fibers
3rd degree AV block results in?
results in ↓CO w/ syncope (stroke-adams attack), dizziness, episodes of acute HF
how does 1st degree AV block appear in ECG?
prolonged PR interval
how does 2nd degree block appear in ECG?
some P waves w/ no corresponding QRS complexes
ST segment elevation occurs during?
occurs during myocardial infarction
ST segment elevation results from what?
loss of potassium from cells - ie. hyperrepolarization and ↓resting membrane potential
accumulation of intracellular sodium - ie. delayed depolarization
