Conduction disorders Flashcards
What do the PQRST of an ECG represent
P: atrial depolarization PR: AV node delay QRS: Ventricular depolarization ST: beginning of repolarization T: Ventricular repolarization
“How to read a rhythm strip”
Assess rate
Regular or irregular
Wide or narrow QRS
P wave to QRS relationship
What is the big box method for counting HR
300 150 100 75 60 50 (5 boxes= 1 second)
What is bradycardia due to
defect in impulse formation (SA) or impulse conduction (heart block)
What constitutes “NSR”
rate 60-100
one P for every QRS, one QRS for every P
P waves have same morphology
QRS (in same leads) have same morphology
What are symptoms of rhythm disorders
fatigue, palpitations, syncope, dizzy spells
Whats important to check on PE
thyroid exam; hypothyroid can cause bradycardia
Hyperthyroid can cause arrhythmia
What must you fix in order to correct chronic hypokalemia
Mg levels
What is the initial survey of ACLS
Circulation
Airway
Breathing
What are the class I anti-arrhythmic drugs
Na channel blockers;
1a: Mod Na block, some K & Ca. Prolong QRS
1b: weak Na block. Min ECG changes. used for Ventricular arrhythmias
* 1c: Strong Na block. wide QRS, SA node depression. NOT for CAD
What are the Class II anti-arrhythmic drugs
Beta blockers: decrease sinus rate, prolong PR
What are the Class III anti-arrhythmic drugs
K channel blockers: prolong QT
*amiodarone prolongs QT but side effects aren’t as bad
What are the class IV anti-arrhythmic drugs
Ca channel blocker: decrease sinus rate, prolong PR
decrease contractility and cause edema
What are other anti-arrhythmic drugs
Digoxin: increase vagal tone/ AV block
Adenosine: AV node blocker (half life 10 seconds)
What is sick sinus syndrome
chronic SA node dysfunction diagnosed by symptoms (brady, sinus arrest, tacky-brady) plus ECG findings)
-Usually d/t fibrosis form aging
What is sinus bradycardia
Normal rate and rhythm but HR under 60
Caused by fibrosis, acute injury, or med s/e
What are symptoms of bradycardia
fatigue, SOB, syncope
When would you place a pacemaker in a bradycardia patient
If symptomatic and d/t irreversible cause
How do you treat sick sinus syndrome
Treat tacky if sx
stop offending agents if brady
Permanent pacemaker to control tachy-brady
What is sinus arrest
failure of sinus node to initiate impulse causing pause >2 seconds
When would you pace a sinus arrest patient
if pause is > 6 seconds
What is tachy-brady syndrome
intermittent fast and slow rates from SA node or atria (<60, >100)
-periods of AFib,
When would you pace a tachy-brady patient
If Afib is present as well
What is first degree AV block
PR interval >200 sec (one big box)
patient asymptomatic, no treatment
What is second degree AV block, Mobitz I
Wenkeback! progressive prolongation until failure to conduct and ventricular beat dropped
site of block is in AV node
How do you treat Wenkebach
Not dangerous, so no treatment
usually asymptomatic
What is second degree AV block, Mobitz II
Fixed PR interval, but dropped QRS
Block is in the HIS (below AV)
EMERGENCY! can lead to complete heart block
What is complete heart block
no conduction from atria to ventricles
P wave independent form QRS with ventricular escape rhythm
EMERGENCY! must pace
What are symptoms of complete heart block
syncope, SOB, HF, fatigue
What are QRS width measurements of bundle branch blocks
Incomplete: 0.10-0.12
Complete: 0.12 or more
(wider QRS= more extensive block)
How do you treat a bundle branch block
No treatment
but look further in ECG to find other indicators for conduction problems
What is RBBB
Rabbit ears; LV depolarizes first, then RV (passively)
Can have RAD
What does a LBBB look like on ECG
V1: negative, big Q wave
V6: positive with LAD
ST and T waves usually opposite (if Q is largely downwards, ST will be elevated)
What can you not diagnose if the patient has LBBB
an MI! Because ST will be elevated if Q is negative
LBBB associated with underlying cardiac dz until disproven
What is always indicated in a tachy patient that is NOT hemodynamically stable
Shock!! (light em up like a christmas tree……. smh)
When should you NOT use adenosine
If patient has WPW or is in Afib
if block is not in AV node, adenosine wont do anything
What is a PAC
early atrial depolarization with different P wave morphology (coming from different site)
What are symptoms of PAC
usually asymptomatic but can cause palpitations
How do you treat PAC
BB or CCB for symptoms.
dont need to treat if asymptomatic
What is SVT
narrow QRS (140-120 bpm) due to accessory pathway cause palpitations and syncope
What does SVT look like on ECG
P wave morphology different but buried in QRS
How do you treat SVT
Unstable: cardioversion
Acute setting: Adneosine and vagal maneuver
**First line tx: ablation
anti-arrhythmics BB CCB for long term
What is WPW syndrome
Type of SVT- Conduction goes through accessory pathway AND AV node. Can lead to FATAL Afib (sending into VFib)
To be syndrome, must have delta wave, Sx, and SVT
What is seen on WPW ECG
Delta wave (slurred upstroke of QRS) Narrow PR In tachycardia, delta wave disappears
How do you treat WPW
same as SVT: cardioversion, adenosine, BB, CCB, anti-arrhythmics
If patient has WPW plus AFib, what should you avoid
AV node blockers (digoxin, adenosine)
What is AFib
No discernible P waves (300-600 bpm)- Irregularly irregular. Ventricles can fire normal or 100+
Associated w/ other heart disease, do thorough workup
What are RF for AFib
age, HTN, CAD, valve dz, obesity, sleep apnea
What are symptoms of AFib
asymptomatic
fatigue, dyspnea, CP, palpitations, syncope, HF
What will you see on AFib ECG
QRS morphology same but can vary in interval length
P waves not discernible and irregular
What are the 3 types of AFib
Paroxysmal: terminates spontaneously w/in 7 days
Persistent: fails to terminate after 7 days
Longstanding persistent: longer than 12 mo
Permanent: talk about rhythm treatment
-Valvular AFib: patient also has mitral stenosis or rheumatic valve dz
What is the CHADSVASC scoring system
Risk stratification for CVA (stroke): C: congestive HF H: HTN A: age 65-74 (1) D: diabetes (1) S: stroke (2) V: A: Age 75+ (2) SC: Sex, female (1)
How do you read a CHADSVASC score
2+ qualify for anticoagulation (NOAC/Warfarin)
1: grey zone, talk to patient depending on points
0: aspirin
Who does CHADSVASC not apply to
Valvular Afib patients
They require WARFARIN (only)
What is warfarin
Vitamin K antagonist
takes 2-3 days to be theraputic (higher doses dont help)
*only anticoag for valvular Afib and mechanical heart valves
Reversible with vitamin K
What is NOAC
novel oral anticoagulant, renally cleared
$$$- but no monitoring!
Onset in 2 hours
What are the types of NOAC
Direct thrombin inhibitor
Factor Xa inhibitor (Eliquis best safety profile)
What are contraindications to taking anticoagulants
Bleeding
Previous ICH
thrombocytopenia
severe HTN
What is the treatment of Afib
Acute: AV node blocker (metoprolol, diltiazem, digoxin)
Cardioversion (24-48 hr window if not on anti-coags- do TEE to check for LAA thrombus)
Anticoag: all undergoing cardioversion, regardless of CHADSVASC (& 4 wks after)
How can you control rhythm and rate in AFib
Rhythm: anti-arrhythmic drug, catheter ablation, surgical maze
Rate: BB, CCB, digoxin (AV node block)- pacemaker or AV node ablation for permanent AFib
What is atrial flutter
Short re-entrant circuit in RA going at 300 bpm, but ventricular response is normal (2:1, 3:1, 4:1)
Carries risk of CVA, assess chadsvasc
What does na atrial flutter ECG look like
SAW TOOTH PATTERN in inferior leads (II, III, aVF)
-Atypical flutter doesn’t have saw tooth
What are the symptoms for atrial flutter
same as AFib: fatigue, dyspnea, CP, palpitations
How do you treat Atrial flutter
Acute: cardioversion/TEE
Chronic: catheter ablation
-Class Ic or III anti-arrhythmic if patient cant do ablation
What is atrial tachycardia
tachy from atria but not SA node. Faster than SA, so it takes over (140-220). Benign
Caused by atrial scarring/drugs (digoxin) and can lead to AFib
What can you find on Atrial tachy ECG
P wave hard to find (in T waves) but rhythm is regular
How do you treat Atrial tachycardia
treat based on symptoms (BB, CCB, class Ic or III)
Adenosine won’t work (not from AV node)
Rarely need cardioversion
What are symptoms of Atrial tachy
palpitations
What is a PVC
Early ventricular depolarization causing wide QRS WITHOUT preceding P wave (bigeminal or trigeminal patterns)
Can be monomorphic or polymorphic
What are symptoms of PVC
palpitations
What will you see on PVC PE
irregular pulse Effective bradycardia (electric beat on ECG w/o perfusion or pulse to match)
How do you treat PVCs
holter monitor to determine burden of PVC
Initial: BB or CCB
Antiarrhythmics (sotalol)
If PVC causes cardiomyopathy, Ablation
What is VTach
3 or more PVC (160-200 bpm), usually d/t CAD/MI causing scar
Non sustained: >3 beats, less than 30 seconds before spontaneous termination
Sustained: >30 seconds, need cardioversion
What are symptoms of VTach
syncope, dizziness, palpitations, CP
May be stable or unstable on PE
How do you treat VTach
full cardiac work up and cardiac cath
What are the types of VTach
Monomorphic: due to re-entrant circuit in ventricle d/t scar
Polymorphic: more electrically unstable, ominous (similar to Torsades and VF)
Is wide complex tachycardia always VT
yes until proven otherwise. Check 12 lead
If unstable, cardiovert!
How do you treat VT acutely
If unstable, cardiovert
Stable with pulse: acutely, IV amiodarone or BB. electrical cardioversion if SR not restored
How do you treat VT chronically
BB
ICD
Class III for long term anti-arrhythmic use
If all fails, ablation
Do anti-arrhythmic improve survival
NOOOOOPE
What is Torsades
A polymorphic VT with LONG QT INTERVAL
“twisting” QRS along isoelectric baseline
**Can occur in complete heart block
How do you treat Torsades
Emergent Cardioversion, can lead to sudden cardiac death
**Use Mag after cardioversion
If unstable, defibrillate
What are symptoms of Torsades
Syncope!
patient may be hemodynamically unstable
Why would you want to temporarily pace a Torsades patient at 100 bpm
To shorten the QT interval
How do you treat long term Torsades
Long term BB and ICD
stop offending agents
What is VFib
Pulseless, no discernable ventricular activity (200-300!)
If untreated, causes systole (DEATH)
What must you emergently do in VFib
Defibrillate! Epinephrine, chest compressions, secure airway
(Rapid resuscitation to prevent anoxic brain injury)
What is the most common cause of VFib
CAD
How are VFib patients most commonly found
Found down, or witnessed out of hospital arrest (3-5% survival)
