Arrhythmias Flashcards
On a 6 lead ECG (3 standard + augmented leads), which one is inverted?
aVR (right arm)
How do Bundle Branch blocks affect the mean electrical axis?
LBBB –> deviates to left and up
RBBB –> deviates right
Name 2 differentials for decreased voltage on ECG
- pericardial effusion
- myocardial damage (infarction or decreased mass)
How does Hypertrophy affect the ECG?
deviates MEA towards the hypertrophy
hypertrophy will require longer time for electrical impulse traveling through and more muscle mass will create greater electrical impulse
longer travel time (prolonged conduction) –> prolonged QRS
How does a bundle branch block affect the T wave?
LBBB - T wave inverted
RBBB - upright
What are the 2 types of 2nd degree AV block?
Mobitz type I (Wenkebach) - PR interval increases with every beat until it finally drops
Mobitz type II - suddenly P without QRS
What is the idioventricular rate?
less than 40
Explain Stokes-Adams Syndrome
total AV block that comes and goes - when AV node is suddenly blocked ventricular escape needs 5-30 seconds to kick in due to overdrive suppression from previous sinus impulse
How does the T wave change after a VPC?
inverted to the polarity of the QRS
What are causes of QT prolongation, what does a prolonged QT interval predispose to?
hypocalcemia, hypokalemia, hypomagnesemia
predisposes to torsades de pointes
Describe the difference between atrial fibrillation and atrial flutter
atrial fibrillation alway have an irregularly irregular beat, impulses travel uncoordinated from different ectopic niduses
atrial flutter - can be irregular or regular, electrical impulse continues to travel through atrium - circus movement
How can you differentiate an ectopic beat of a VPC coming from the right side or the left side of the heart?
L-side - RBBB morphology, deep S wave
R-side - LBBB morphology, upright
What rate is considered VT in cats versus dogs?
over 180 (dogs), over 240 (cats)
Name 3 breed-related heart conditions commonly leading to ventricular arrhythmias
- Dobermann Pincher, DCM
- Boxer, ARVC
- German Shepherd, IVAGSD
What are the beta-1 and beta-2 effect proportions of atenolol, esmolol, and propranolol
atenolol, beta-1 and beta-2 but more beta 1
esmolol, beta-1 selective
propranolol - nonselective beta blockade
Why are class II antiarrhythmics contraindicated in CHF?
because of further suppression of systolic function (negative inotropic), can worsen HF
What class effects does Sotalol have?
II, III
beta-blocking
K-channel blocking (main effect)
What class effects does amiodarone have?
all I, II, III, IV
Why do VPCs have wider QRS complexes than sinus beats?
because they don’t use the normal conduction system - sinus beat ventricular depolarization initiated through Purkinje Fibers which have an extremely fast conduction velocity - will be slower to travel through ventricular myocytes
Describe the physiologic AV block
means that atrial rate is too high and the AV node “purposefully” filters out impulses to slow the ventricular rate, protective
What group of tachyarrhythmias are more responsive to vagal maneuvers?
SVTs - VT almost never repsond to vagal maneuvers
Describe how you would perform a vagal maneuver
carotid massage - between mandibular arch and atlas wings - apply pressure from ventrally to the neck for 5-10 seconds
ocular - apply gentle pressure to the closed eye
What is the recommended ergency treatment for SVTs?
Diltiazem and/or beta-blockers
Name 3 oral treatment options for VTs.
Sotalol, mexiletin, amiodarone
Describe how you would perform an atropine response test
give 0.04 mg/kg atropine IV or IM
if IV - recheck ECG 15 min later
if IM - recheck 30 min later
rate should increase by 50-100%??
Name long term oral treatment options for atropine-responsive bradyarrhythmias. What are the MOAs of these drugs?
theophylline - methylanthine bronchodilator
terbutaline - beta-2 agonist (bronchodilator)
List 4 drug classes that may induce bradycardia
sedative
opioids
antiarrhythmics
anesthetics
What classifies a second-degree AV block as high degree?
if there are more lone Ps than conducted QRS
or consecutive non-conducted atrial impulses
What are typical escape rates in dogs and cats
20-60 dogs
80-140 cats
Explain overdrive suppression in SSS
ventricles are overdriven by the previous sinus rhythm (often tachycardia if tachycardia-bradycardia syndrome) - when the sinus block/arrest happens ventricular escape can not “kick in” as fast because of the overdrive - long pause and often syncope
Explain the steps of temporary transvenous pacing
femoral or left jugular vein (R jug preserved for potential permanent pacemaker insertion)
depending on patient temperament with or without sedation (e.g., opioid + parasympatholytic), sterile prep of the left neck, insertion of introducer catheter large enough to fit electrode –> advanced into the right ventricle, apex
optional: balloon at end inflate once RA, deflate once past the
confirm correct placement via fluoroscopy or echocardiogram
set desired heart rate
gradually increase pacing output (mA) until capture is noted on ECG
pacing: VVI (ventricle paced, ventricle sensed, pacing inhibited during sensed event)
starting sensitivity 2-4 mV
What are typical sensitivity settings for temporary pacing?
2-4 mV
How long do pauses in heart beat usually last before causing syncope (e.g., in SSS or sinus arrest)
longer than 6-8 seconds
How do you differentiate sinus block and sinus arrest?
often difficult to differentiate, some references say block is one beat and arrest is longer
other references: sinus arrest - no sinus impulse initiated, sinus block: electrical impulse happens but can’t leave the SA node because not conducted
What is a wandering pacemaker?
changes in P wave amplitude corresponding to breathing cycles, when vagally mediated bradycardia
higher P waves during higher HR during inspiration
Explain the Bezold-Jarish reflex
increased activity/excitement/coughing/vomiting –> tachycardia and hypercontractile ventricle –> intraventricular receptors (C vagal fibers) –> causes reflex simiar to vasovagal reflex
vagal afferent nerves –> medulla –> vagal efferent nerve –> slowing HR suddenly after tachycardia
At what PR interval length is the interval considered prolonged in dogs or cats?
dog > 130 ms
cat > 90 ms
How can you use an atropine response test to differentiate Mobitz type 1 from type 2 AV block?
mobitz 2 will not respond or get worse
What are the adverse effects of parasympatholytics/
dry mouth, constipation, mydriasis, urinary retention, neurologic signs
What is the most likely diagnosis in a young/middle-aged dog with paroxysmal SVT that is not systemically ill?
Atrioventricular accessory pathway - congenital muscular bundles penetrating the normal fibrous skeleton between atria and ventricles
more often concealed to only move retrograde from ventricle to atria
Name 3 proposed mechanisms of myocardial dysfunction from sustained SVTs
- increased HR - increased work –> impaired myocardial energy utilization + energy depletion
- increased HR –> impaired coronary blood flow –> ischemia
- abnormal Ca handling
List differentials for SVTs with an irregular rhythm
- atrial fibrillation
- atrial flutter (can be regular too)
- multifocal atrial tachycardia
SVTs usually have QRS durations of less than XXXX in dogs and YYYYY in cats
70 ms (dogs), 40 ms (cats)
List ways to differentiate SVTs and VTs
- wide QRS VT, narrow QRS SVT (exception SVT with BBB)
- irregular SVT (both VT and SVT can be regular)
- atrioventricular dissociation VT
- abnormal mean electrical axis VT
- fusion beat VT
- VT opposite direction T wave, SVT either positive or negative
- distinct J point SVT
- response to vagal maneuver SVT
- response to lidocaine VT
What is the in-hospital goal for rate control of the ventricular repsonse rate in afib?
160-180
Define ventricular tachycardia
ventricular rhythm with HR >180
Define sustained versus nonsustained VT
sustained > 30 seconds
