cardiac arrhythmias Flashcards
what does the P wave of an ECG represent
atrial depolarization - initiates contraction of the atrial vasculature
what does the QR portion of an ECG represent
ventricular depolarization - conduction electrical impulses into the ventricles bypassing the av - His purkinje system
what does the T wave of an ECG represent
ventricular repolarization - cell experiences an efflux of K+ ions along its electrochemical gradient
what is the normal heart rate
60-100 bpm
a normal sinus rhythm on an ECG will show one __ wave preceding each QRS
P
_____ is some of the most distressing types of heart malfunctions. occurs because of abnormal rhythm of the heart i.e. lack of coordination between the beat of the atria and the ventricles
cardiac arrhythmia
what causes cardiac arrhythmias
- abnormal rhythmicity of the pacemaker
- shift of the pacemaker from the sinus node to another place in the heart
- blocks at different points in the spread of the impulse through the heart (e.g ischemia)
-abnormal pathways of impulse transmission through the heart - spurious impulses in any part of the heart
_____ means fast heart rate; usually > 100 bpm in an adult
tachycardia
what causes tachycardia
- increase in body temp
- stimulants (drugs, caffeine, alcohol)
- stimulation of the heart by the sympathetic nerves
______ means slow heart rate; usually < 60 bpm
bradycardia
in bradycardia is the R-R interval longer or shorter
longer
what causes bradycardia
- athletes due to increased endurance
- beta blockers
- vagal stimulation (carotid sinus syndrome)
______ is the impulse from the sinus node is blocked before it enters the atrial muscle. the ventricles spontaneously pick up a new rhythm (av node), therefore the rate is slowed but not otherwise altered
sinoatrial block
what are some causes of AV block
- ischemia of the AV node/bundle ~ coronary insufficiency
- compression of the AV bundle ~ scar tissue/calcification
- inflammation of the AV node/bundle ~ fevers
- extreme stimulation of the heart by the vagus nerves ~ carotid sinus syndrome
a type of reflex syncope or near-syncope with symptoms (eg, syncope (fainting), lightheadedness) caused by CSH (carotid sinus hypersensitivity) manifesting during activities of daily life that put pressure on the carotid sinus (eg, turning the neck, looking upward).
carotid sinus syndrome
____ occurs when the P-R or P-Q interval increases to >0.20 seconds
first degree block
what is the normal length of a P-Q interval
0.16 seconds
______ occurs when conduction through the A-V bundle is slowed enough to increase the P-R interval to 0.25-0.45 seconds. can often have a “dropped” or missing ventricular beat
second degree block
_____ occurs when the condition causing poor conduction in the AV node or AV bundle becomes severe. dissociated P and QRS-T complexes. rhythm of atria is >100 bpm, and ventricular beat is <40 bpm
third degree (complete) block
_____ occurs when the sinus node fails to produce an impulse. another focus in the heart takes over the duty to produce a rhythym
escape rhythym
_____ occurs when the sinus node fails to produce an impulse. another focus in the heart takes over the duty to produce a rhythym
escape rhythym
_____ occurs when the sinus node fails to produce an impulse. another focus in the heart takes over the duty to produce a rhythym
escape rhythym
_____ occurs when the sinus node fails to produce an impulse. another focus in the heart takes over the duty to produce a rhythym
escape rhythym
what are the two types of escape rhythms
junctional escape and ventricular escape
this rhythm originates in the AV node (Rate of 40-60 bpm)
junctional escape
______ occurs when AV total block comes and goes. impulses are conducted from the atria into the ventricles for a period of time and then suddenly impulse are not conducted. the duration of the block may be a few seconds to a week or longer before conduction returns. occurs in hearts with borderline ischemia of the conductive system
stokes-adams syndrome
this rhythm originates in the purkinje fibres (rate of 15-40 bpm with an abnormally wide QRS)
ventricular escape
______ is a block in the peripheral ventricular purkinje system. usually caused by tachycardia, ischemia, digitalis myocarditis. every second beat is a different altitude
electrical alternans: incomplete atrioventricular block
______ is a contraction of the heart before the time that normal contraction would have been expected. AKA ectopic beat
premature contractions
what causes premature contractions/ectopic beats
- local areas of ischemia
- small calcified plaques
- infection, drugs nicotine, caffeine
- mechanical stimulation (cardiac catherterization)
_____ has a shortened P-R interval; this is the origin of ectopic foci
premature atrial contractions
are abnormal pacemaker sites within the heart (outside of the SA node) that display automaticity.
ectopic foci
_____ has a superimposed P wave onto QRS-T complex
AV node/bundle premature contractions
_____ has prolonged QRS, high voltage QRS and an inverted T wave
premature ventricular contractions
_____ is a premature beat, a pause, and then another beat with a long QT interval. it may trigger arrhythmias, tachycardia and in some instances ventricular fibrillation
torsades de pointes
______ is a disorder of cardiac depolarization caused by prolonged ventricular action potentials. high risk for torsades de pointes
long QT syndrome (LQTS)
what causes LQTS
- congenital: mutations in Na+/K+ channel genes
- electrolytes: hypomagnesemia, hypokalemia and hypocalcemia
-drugs: anti arrhythmic (quinidine) and antibiotics (fluoroquinolone and erythromycin)
what are the symptoms of LQTS
- fainting
-ventricular arrhythmias - fibrillations and sudden death
*some may not even show any symptoms
how is acute LQTS treated
magnesium sulfate
how is long term LQTS treated
beta blockers and cardiac defibrillator
______ is abnormalities in the atria, purkinje system, or ventricles, that can cause rapid rhythmical discharge of impulses that spread in all directions throughout the heart. most frequently caused by “circus movement”. because of the rapid rhythm in the irritable focus, thus focus becomes the pacemaker of the heart
paroxysmal tachycardia
what are the two reasons ventricular paroxysmal tachycardia is a serious condition
- frequently initiates v-fib
- does not occur unless considerable ischmic damage is present in the ventricles
what causes ventricular paroxysmal tachycardia
digitalis intoxication
how is ventricular paroxysmal tachycardia treated
amiodarone, lidocaine and AED
______ is the most serious cardiac arrhythmia (1-3 mins). lack of coordination of muscle contraction, negligible/no blood is pumped, fainting occurs within 4-5 seconds, tissue death begins within mins
ventricular fibrillation
what triggers v-fib
- sudden electical shock of the heart
- ischemia of the heart muscle, conducting system or both
what triggers v-fib
- sudden electical shock of the heart
- ischemia of the heart muscle, conducting system or both
what are the three conditions leading to re-entry
- the impulse pathway is much longer than normal
- decreased velocity of impulse conduction
- shorten refractory period (adrenaline does this)
_____ has the same mechanism of v-fib. most common cause is atrial enlargement, valve lesions and ventricular failure
atrial fibrillation
________ characteristics include: the electrical signal travels as a single large wave always in one direction around and around. causes a rapid rate of contraction of the atria (200-350 bpm). the amount of blood pumped by the atria is slight. not all impulses make it through there AV node
atrial flutter
