ECG Part III Flashcards
what are the effects of cardiac arrhythmias?
syncope
weakness
decompensation of CHF
reduced blood flow
death
arrhythmias are more concerning in animals with ________________________________
advanced heart disease
how can you identify arrhythmias?
auscultation
ECG
what are the three mechanisms of arrhythmia?
altered automaticity
triggered activity
re-entry
where do all sinus rhythms originate?
sinoatrial node
what is normal sinus rhythm?
normal P wave coming in regular intervals
typically normal P-QRS-T complexes
normal heart rate
normal relationship between the P-QRS-T complexes
in sinus arrhythmia, there is cyclic/rhythmic variation in _______________________
P-P intervals
in whom is sinus arrhythmia normal?
dog
horse
what is the P-QRS-T complex like in sinus arrhythmia?
typically normal
what are the cutoffs for sinus bradycardia in dogs, cats, bovine, and equine in rates?
dog: 60/min
cat: 160/min
bovine: 46/min
equine: 24/min
what are the rate cutoffs for sinus tachycardia in dogs, cats, and equids?
dog: 160/min
cat: 240/min
equine: 60/min
what is the rhythm like typically with sinus tachycardia?
regular, with normal P-QRS-T complex
what happens in supraventricular premature depolarizations?
regular rhythm is interrupted by a premature depolarization from the atria or AV junctional tissue
what is the appearance of the supraventricular premature depolarization?
fairly normal QRS-T appearance
what is a compensatory pause?
pause during premature beat is equal to twice the normal R-R interval
what is supraventricular tachycardia?
runs or paroxysms of ectopic complexes
>= 3 in number
originate from atria or AV junctional tissue
what is atrial tachycardia?
atrial tissue alone is utilized for origination and maintenance of arrhythmia
____________________ is an unstable rhythm that often leads to atrial fibrillation
atrial flutter
what is atrial fibrillation?
chaotic, disjointed atrial activation
what is the heart rate in atrial fibrillation?
usually a rapid rat
what is the morphology of the QRS-T in atrial fibrillation?
usually fairly normal
often some beat-to-beat variation in QRS height
what are ventricular premature depolarizations?
premature ectopic impulses originating from the ventricles
what is the appearance of the ECG with ventricular premature depolarizations?
wide and bizarre appearance of QRS-T
large T wave in opposite direction of QRS
ST segment slurring
compensatory pause
what happens in ventricular premature depolarizations?
spontaneous depolarization in the ventricle
fires before sinus node impulse reaches ventricle
what is a fusion beat?
complex formed when the normally conducted impulse and a ventricular ectopic beat simultaneously depolarize the ventricle
what is coupling?
fixed relationship between a premature beat and the beat that precedes it
how can you differentiate between unifocal and multifocal?
unifocal: all premature beats look the same
what is ventricular tachycardia?
a run or paroxysm of >= 3 premature ectopic impulses originating from the ventricles
what is a compensatory pause?
pause during premature beat is equal to 2x the normal R-R interval
what is sustained ventricular tachycardia?
ventricular tachycardia lasting more than 30 seconds
why are VPCs not good?
do not generate a good blood pressure
what is accelerated idioventricular rhythm?
ventricular origin beats that are not tachycardia
what is ventricular fibrillation?
chaotic, disorganized activation of the ventricles
irregular undulations in the baseline
what is cardiac output in ventricular fibrillation?
drops to zero
what do IKr blocking drugs cause?
QT prolongations, setting up lethal arrhythmias
where do junctional escape rhythms originate from?
AV junction
where do ventricular escape rhythms originate from?
purkinje fibers
what is sinus arrest?
failure of the sinus node to discharge for a period more than twice the normal R-R interval
what do long pauses in sinus arrest often result in?
syncope
what is sick sinus syndrome?
syndrome often characterized by bradycardia and tachycardia resulting in clinical signs
periods of sinus arrest often followed by paroxysm of supraventricular tachycardia
what is atrial standstill?
atrial activity is absent
no P waves anywhere on ECG strip
what can atrial standstill result from?
severe hyperkalemia
atrial muscular dystrophy
how can you recognize severe hyperkalemia on an ECG?
atrial standstill
peaked T wave
bradycardia
what does a first degree AV block look like on an ECG?
minor delay in AV conduction
prolonged P-R interval
what is happening in third degree AV block?
no conduction through the AV node
no P waves conducted to thee ventricles
atria and ventricles beat in independent fashion
what can be the cause of first degree AV block?
physiologic
drugs
pathologic
what is second degree AV block?
more advanced conduction disturbance
some P waves are not conducted to the ventricles
what is mobitz type I second degree AV block?
progressive P-R prolongation before the block
what is mobitz type II second degree AV block?
fixed P-R interval: often more advanced form of AV block
who can have physiologic second degree AV block?
dog
horse
what can cause third degree AV block?
pathologic
drugs in overdose
what are the rates in third degree AV block?
atrial rate normal or fast
ventricular rate usually slow
the ST segment should not be depressed more than ______________
0.2mV
the ST segment should not be elevated more than ______________
0.1 to 0.15mV
what can ST segment alterations indicate?
ischemia or hypoxia
electrolyte changes
conduction disturbance
myocardial infarction
accessory pathways lead to ___________________________________
supraventricular tachycardia
what does a wandering pacemaker look like?
variable P wave height or appearance
what varies with respiration in respiratory sinus arrhythmia?
rate
is sinus bradycardia usually a regular rhythm?
yes
what type of pause do supraventricular premature depolarizations have?
non-compensatory
what can supraventricular premature depolarizations have with P waves?
may have ectopic prior to, within, or following QRS-T
what type of tachycardia does supraventricular tachycardia usually cause?
often very regular
what does atrial fibrillation look like on an ECG?
irregularly irregular R-R intervals
usually baseline undulations due to atrial fibrillation
lack of organized P waves, no consistent relationship between waves and following QRS-T
what type of pause is associated with ventricular premature depolarizations?
compensatory
what are the T waves like in ventricular premature depolarizations?
large, opposite direction of QRS
what is the ST like in ventricular premature depolarizations?
slurring: no real ST segment shelf
what does an accelerated idioventricular rhythm look like?
ventricular origin beats that are not tachycardic
what is the rate with ventricular escape rhythms?
24-40/min
what is the rate with junctional escape rhythms?
60-100/min
what are periods of sinus arrest often followed by?
paroxysm of supraventricular tachycardia
who can have physiologic second degree AV block?
dogs
horses
what is the ventricular activation usually in third degree AV block?
junctional or ventricular escape rhythm
