ECG and Dysrhythmias in Small Animals Flashcards
1
Q
what is the P wave
A
atrial depolarization
2
Q
what occurs during the P wave (5)
A
- SA node cells in RA spontaneously depolarize –> depolarizes adjacent RA cells
- wave of depolarization moves towards the left
- cells in left atrium are at rest and a dipole is created –> positive end is closer to the positive electrode so get a upward trace
- when all RA and LA are depolarized the trace returns to base line
- next delay is the wave of depolarization passing through the atrioventricular node to the ventricles
3
Q
what is the Q wave
A
early ventricular depolarization
4
Q
what occurs in the Q wave
A
- wave of depolarization passes down the interventricular septum
- wave of depolarization spreads from left to right creating a dipole
- negative end of the dipole is closer to the + electrode so it creates a negative deflection on the ECG trave
5
Q
what is the R wave
A
ventricular depolarization
6
Q
what occurs in the R wave (4)
A
- endocardium depolarizes before the epicardium
- dipole is created which is very large since the number of cardiomyocytes within the left ventricle are numerous
- the positive end of the dipole is closer to the + electrode so it creates an upward deflection on ECG trace
- a dipole is created towards the left since the ventricular apex is directed towards the left and the left ventricle is much larger than the right and dominates
7
Q
what is the S wave
A
late ventricular depolarization
8
Q
what occurs in the S wave (3)
A
- the wave of depolarization finishes spreading from the endocardium to the epicardium of both ventricles
- the ECG returns to baseline and can sometimes go negative
- the negative end of the dipole is closer to the + electrode –> downward deflection in trace
9
Q
what is the T wave
A
ventricular repolarization
10
Q
what occurs in the T wave (3)
A
- the epicardium is the last to depolarize but the first to repolarize
- epicardial cells are now positive on the extracellular surface and create a dipole with the endocardial cells which are still depolarized
- positive end of the dipole is closer to the + electrode –> upward deflection in ECG occurs
11
Q
what is the PR interval
A
PR: time between atrial depolarization and ventricular depolarization
12
Q
what is the QT interval
A
length of time between the ventricles remain depolarized
13
Q
what is the QRS complex interval
A
time take for the ventricular depolarization to occur once the wave of depolarization has passed through the AVN from the atria
14
Q
what is the PP interval
A
time between atrial depolarizations
15
Q
what is the RR interval
A
time between ventricular depolarizations
16
Q
what are the uses of the ECG (4)
A
- diagnosis of arrhythmias noted on clincal exam
- rule in/out arrythmias in animals with a history of collapse
- provide info regarding chamber enlargement
- information on certain electrolyte disturbances (K+)
17
Q
how are ECGs analyzed (8)
A
- heart rate (slow/normal/fast)
- heart rhythm (regular/irregular/chaotic)
- P:QRS ratio (1:1)
- relationship of P to Q-P-Q interval
- P and QRS complex variation
- normal complex measurement
- QT interval, ST segment & T waves
- assess the significance of any arrhythmias detected
18
Q
how is the heart rate measured
A
count Y beats in 6s
Y x 10 = beats/min
with 25 mm/s paper speed (need to know)
19
Q
what can you look for when assessing the rhythm (4)
A
- early beats
- delays
- fibrillation
- ectopic beats
20
Q
what do you look at when looking at P:QRS ratio and relationship (3)
A
- check distance between P wave and the QRS complex. Is it too long?
- is there a P wave before the QRS
- is there a P wave without QRS
21
Q
what is wandering pacemaker
A
P wave variation: tall wave and short wave
22
Q
what are QRS complex variations
A
- venticular ectopies either from left ventricle or right ventricle
23
Q
what occurs during an abnormal ventricular activation pattern from the left ventricle
A
sometimes called a right bundle branch block pattern QRS complex
electrical signal spreads through in an abnormal direction –> spread cranially –> negative QRS
wide bizarre QRS
24
Q
what is an abnormal ventricular activation pattern from the right ventricle
A
sometimes called a left bundle branch block pattern QRS complex.
electrical activity travels from the right ventricle and travels from cranial to caudal which creates a positive QRS
25
what are the differences between premature and escape beats
26
what are P wave changes (3)
1. absent: atrial standstill
2. wide P waves: left atrial dilation
3. tall P waves: right atrial dilation
27
what change is shown here
atrial standstill
absent P wave
28
what is shown here
wide P waves
left artial dilation
29
what abnormality is shown here
tall P waves
right atrial dilation
30
what are common QRS changes (4)
1. tall R: left ventricular enlargement
2. deep S: right ventricular enlargement
3. small complexes: pleural effusion, obesity
4. small variable height complexes: pericardial effusion
31
what is shown here
tall R left ventricular enlargement (also T wave is large)
32
what change is shown here
deep S
right ventricular enlargement
33
what is shown here
small complexes
pleural effusion, obesity
34
what is shown here
small variable height complexes
pericardial effusions
35
what could be causes of a prolonged QT interval (4)
1. hypocalcemia
2. hypokalemia
3. hypothermia
4. drugs (sotalol)
36
what are causes of shortened QT intervals (3)
1. hypercalcemia
2. hyperkalemia
3. drugs (digoxin)
37
what does a prolonged QT cause
excessive intracellular calcium and possibly a rapid, fatal ventricular tachycardia called Torsade de Pointes
38
what does ST segment depression indicate
hypoxia
39
what is shown here
ST segment depression
40
what does ST segment coving indicate
left ventricular enlargement
41
what is shown here
ST segment coving
left ventricular enlargement
42
when are arrhythmias treated (3)
1. causing signs in their own right (syncope)
2. potentially life-threatening (ventricular tachycardia)
3. no underlying immediately treatable cause
43
what are the classifications of rhythms (3)
1. normal
2. bradyarrhythmias
3. tachyarrhythmias
44
what are normal rhythms (2)
1. sinus rhythm
2. sinus arrythmia (normal for dogs)
45
what rhythm is shown here
sinus rhythm
46
what rhythm is shown here
sinus arrhythmia
47
what are bradyarrhythmias (8)
1. sinus arrest
2. sick sinus syndrome
3. sinus bradycardia
4. atrial standstill
5. primary AV block
6. second degree AV block: mobitz type 1
7. second degree AV block: mobitz type 2
8. 3rd degree/complete AV block
48
what are the causes of a sinus arrest (2)
1. medication: sedatives, beta blockers, calcium channel blockers, digoxin
2. diseases: high vagal tone, atrial disease, hypothyroidism
49
what is sinus arrest
complete sessation SA node activity
normal beats but there is a pause --\> followed by a ventricular ectopic beat which would be an escape because it follows a pause
50
what are arrhythmia is shown
sinus arrest
51
how do you treat sinus arrhythmias
address underlying problem
52
what breed might sinus arrest be normal for
brachycephalic
53
what can sinus arrest be accentuated by
general anesthesia
54
what rhythm is shown here
sick sinus syndrome
sinus tachycardia?
55
what breeds have a hereditary component to sick sinus syndrome
mini schnauzer
west highland white terrier
56
what diseases cause sick sinus tachycardia
idiopathic
may also have spells of tachycardia
57
how is sick sinus syndrome treated (3)
1. pacemaker
2. sympathomimetics: theophylline, propentofylline, terbutaline
3. parasympathomimetics: propantheline
58
what is sinus bradycardia
sinus rhythm --\> but very slow \<60 in dogs, \<100-120 in cats
beats of normal sinus origin and conduction, often regular
59
when can sinus bradycardia be normal (3)
1. excessive vagal tone
2. athletic animals
3. normal rhythm under GA if not too slow if BP is acceptable
60
what are the causes of sinus bradycardia (3)
1. medication: sedatives (ACP), drugs used to treat tachyarhythmias
2. disease: hypothyroidism, increased intracranial pressure, dysautonomia, eletrolyte imbalances
3. metabolic: hypothermia
61
how is sinus bradycardia treated
address the underlying problem
62
what is shown here
sinus bradycardia
63
what is atrial standstill
no P wave, regular QRS, followed by large spikey T waves
64
what rhythm is shown
atrial standstill
no P wave, regular QRS followed by large spikey T waves
65
what are the causes of atrial standstill (2)
1. persistent: idiopathic, presumed atrial cardiomyopathy, muscular dystrophies, treated by pacing but prognosis is poor
2. temporary: hyperkalemia (hypoadrenocorticism, oliguric renal failure)
66
how is atrial standstill treated
address underlying problem
67
what is first degree AV block
P wave then a delay before QRS complex
68
when is a first degree AV block normal
can be normal in dogs with slow heart rates esp during sleep
69
what can cause a first degree AV block (2)
1. drugs: sedatives, tachyarrhythmia drugs
2. disease: high vagal tone, fibrosis of AV node
70
what is a second degree AV block mobitz type 1
occasional P wave occurs without QRS-T complex
71
what rhythm is shown here
first degree AV block
delay after P wave
72
when can 2nd degree AV block mobitz type 1 be normal
in dogs with high vagal tone or alseep
normal in horses
73
what are the causes of 2nd degree AV block mobitz type 1 (2)
1. diseases causing high vagal tone
2. regular cycle of (several) dropped beats is more likely to be associated with progressive myocardial disease and may progres to 3rd degree AV block
74
how are 2nd degree AV block mobitz type 1 treated
address the underlying problem if possible but not usually symptomatic
75
what is the atropine response test
record ECG
give atropine s/c 0.04 mg/kg
approx 30 min later record a second ECG
if the arrythmia is gone --\> then it is vagal in origin (HR usually \>150)
76
what is a 2nd degree AV block mobitz type 2
Don’t see progressive lengthening of the PR interval and there is much more frequent dropping of beats and more frequent isolated P waves often in a an irregular (alternating between conductive and dropped beats)
77
what does a 2nd degree AV block mobitz type 2 indicate
significant and indicates AV node disease
78
what are the causes of 2nd degree AV block mobitz type 2
1. diseases: AV node fibrosis, infiltration
79
how is 2nd degree AV block mobitz type 2 treated
pace if symptomatic often progresses to 3rd degree block
80
what rhythm is shown here
2nd degree AV block mobitz type 2
81
what is a 3rd degree/complete AV block
P waves and QRS-T complexes are completely dissocaited
normal P waves occur but the ventricles are activated at a slower rate from a junctional or ventricular focus --\> escape beats look bizarre
82
what is the arrhythmia shown here
3rd degree/complete AV block
P waves and QRS-T complexes are completely dissociated
83
what are the causes of 3rd degree/complete AV block
1. diseases: AV node fibrosis, AV node infiltration, lyme disease
84
what is the treatment of 3rd degree/complete AV block (3)
1. pacemaker
2. sypathomimetics: theophylline, propentofylline, terbutaline
3. parasympatholytics: propantheline
85
what can a 3rd degree/complete AV block represent
serious myocardial disease or toxemia or conduction system degeneration but often myocardial function is otherwise preserved
86
what arryhthmia is shown here
3rd degree/complete AV block with no escape beats
87
what are the tachycarrythmias (7)
1. sinus tachycardia
2. supraventricular premature beat
3. atrial fibrillation
4. supraventricular/atrial tachycardia
5. ventricular premature complex (VCP)
6. ventricular tachycardia
7. rapid ventricular tachycardia
88
what is sinus tachycardia
normal P-QRS-T complexes of SA node origin but at a higher than normal rate, regular rhythm
can be normal finding in nervous or excitable dogs (even up to 280-300)
89
what are the causes of sinus tachycardia
1. medication: drugs used to treat bradycardia
2. disease: anemia, pain, pyrexia, resp distress or in response to hypovolemia, shock, dehydration, septicemia, decreased CO, hyperthyroidism, hypertension under GA or due to cardiac failure
90
how is the sinus tachycardia treated
address underlying problem but not usually treated
91
what arrhythmia is this
sinus tachycardia
92
what is supraventricular premature beat
ectopic beat from the myocardium
can't see P wave and if its there its abnormal in conformation
QRS-T complex is normal
93
what arryhthmia is shown
supraventricular premature beat
94
what causes supraventricular premature beats
1. disease: atrial fibrillation, atrial fibrosis, systemic diseases such as pyrexia, neoplastic diseases
95
how is supraventricular premature beat treated
address underlying problem, but not treated specifically
96
what is atrial fibrillation
absent P waves which are replaced by fibrillation waves
QRS-T complexes are normal in conformation but are rapid and erratic (chaotic) rhythm
97
what are the causes of atrial fibrillation
1. disease: atrial dilation, atrial infiltration, atrial fibrosis, occult dilated cardiomyopathy/lone atrial fibrillation
2. larger dogs, uncommon in cats
98
what is the most common treated atrial arrhythmia in dogs
atrial fibrillation
99
how is atrial fibrillation treated
slow down ventricular rate, slow conduction through AV node
1. digoxin
2. usually with diltiazem
3. (atenolol)
100
what is supraventricular/atrial tachycardia
bursts of atrial ectopic beats
101
what are the causes of supraventricular/atrial tachycardia
1. congenital: by-pass tract (Wolf-Parkinson-White syndrome) --\> bridging the atrial to the ventricular myocardium and bypassing the AV node and allowing rapid circuit of impulses going down the AV node and going back up the bypass tract
2. disease: atrial dilation, atrial infiltration, atrial fibrosis, systemic disease
102
what is the treatment of supraventricular/atrial tachycardia (4)
1. digoxin
2. diltiazem
3. atenolol
4. sotalol ablation of by-pass tract
103
what is shown here
atrial fibrillation
104
what is shown here
supraventricular/atrial tachycardia
105
what is ventricular premature complex (VCP)
no P wave present (except by coincidence)
QRS-T complex is premature and prolonged duration and bizarre in shape often with a large, slurred S-T segment and T wave
106
what is paroxysmal ventricular tachycardia
ventricular premature complexes can occur as single or pairs or as rapid bursts
107
what is shown here
ventricular premature complexes (VCP)
108
what are the causes of ventricular premature complex (3)
1. disease: ventricular myocardial dilation, inflammation, infiltration, fibrosis
2. systemic disease: anemia, septicemia, splenic mass, gastric dilation, pyometra
3. metabolic: electrolyte imbalance (hypokalemia)
109
how is ventricular premature complex treated
address underlying problem, but not treated specifically
110
what is ventricular tachycardia
runs of ectopic beats
can cause syncope and is life threatening
111
what is shown here
ventricular tachycardia
112
what are the causes of ventricular tachycardia
1. disease: ventricular myocardial dilation, inflammation, infiltration, fibrosis
2. systemic disease: anemia, septicemia, splenic mass (if rate in dogs is between 60 & 160/min, called accelerated idioventricular rhythm and NOT usually treated)
113
how is ventricular tachycardia
if runs \>180/min, symptomatic, multiform R-on-T
lidocaine, magnesium, mexilitine, sotalol, amoidarone
114
what is shown here
rapid ventricular tachycardia
115
what are the causes of ventricular tachycardia
ventricular myocardial dilation
inflammation
infiltration
fibrosis
trauma
hypoxia
116
what is ventricular escape beat
ventricular ectopic following a pause are called escape beats
rescue beat: look for underlying cause of bradycardia
117
what is shown here
ventricular escape beat
