Arrhythmias Flashcards
week 4
What is the normal duration for:
QRS
PR interval
QRS: 40-100ms
PR interval= 120-200ms
What is the ECG of of a sinus brachycardia and what are the common causes?
HR< 60
sinus rhythm
Increased PNS
Increased SV
Sleep, drugs
Acute HTN
what is a sinus rythym?
normal pattern
sinus node –> atria (contract) –> AV –> onwards
Describe a sinus rhythm on a ECG
- P waves with a consistent shape BEFORE QRS
- { waves in postive leads I, II and aVF and negative lead aVR
What is the treatment for a sinus bradycardia rythym?
Sympathomimetic drugs
Parasympatholytic drugs
SV vs CO
SV= blood per beat
CO= blood per minute
SV= 50-100ml/beat
CO= 4-8L/min
what is the ECG and cause of Sinus tachycardia?
HR> 100bpm
sinus rhythm
causes:
- increased SNS
- increased metabolic rate
-decreased BP
What are the treatments and possible complications of sinus tachycardia?
treatments
- sympathetic drugs
-Ca2+ channel blockers
Complication
- decreased CO due to less time for ventricular filling = decreased SV
What occurs in sick sinus syndrome and what is its treatment?
SA node oscillates between tachycardia and bradycardia
treatment
-artificial pacemaker
What is sinus arrhythmia and what are its associated causes?
- variability in sinus Rhythm (P-P interval)
- Ventilation and fluctuations in ANS tone
What is sinus arrest and what is its complication?
No SA node
-His-Purkinje system restores at a slower rate
No CO
What are escape rythyms?
Latent pacemakers escape inhibition of more active SA node
(SA node can’t generate effective impulses)
what is abnormal atrioventricular conduction?
Disturbance of sinus impulse from atria to ventricles.
What are the characteristics of a first degree AV block ECG/
P-wave precedes QRS
PR intervals > 25ms/5ss
What are the characteristics of a second degree I AV block ECG?
PR interval progressively lengthens until a P wave is not conducted to V ( Not all P is associated with QRS)
QRS clustered
PP intervals are constant but RR intervals vary
What are the characteristics of a second degree II AV block ECG?
P waves intermittently non-conducted = constant PR intervals
Prolonged QRS complex
What are the characteristics of a third degree AV block ECG/
All P waves non-conducted = complete absence of AV conduction
Ventricular escapes control rhythm of QRS
Cause and treatment of First Degree AV conduction block.
MI
Drugs (digitals and digoxin)
Congenital heart defects
Manage underlying cause
Cause and treatment of Second Degree I AV conduction block.
Reversible ischemia of AV node
Acute MI
Treatment
Only if progresses to Mobtiz II
What are the causes of Second degree II AV conduction block and what are its complications and treatment options?
Anterior septal MI
Damage to BoH/ RBB
Fibrosis of conduction system
Complications
Bradycardia compromises CO
Progress to CHB?
treatment
Artificial pacemaker
What is the complication and treatment option for a thrid-degree AV conduction block?
Complication
Bradycardia compromises CO
Treatment
Artificial pacemaker
Describe the access pathway associated with WPW syndrome.
Accessory pathways pass from A –> V without passing through AV node
ECG of WPW syndrome
PR interval short
delta wave (abnormal start to QRS)
Prolonged QRS complex
Associated complication and treatment options for WPW dyndrome
accessory pathways may allow reentry → VT/ VF
Treatments
antiarrhythmic drugs -
surgical ablation of the accessory pathway
disruption of the conduction pathway
What are the three common mechanisms tha give rise to ectopic sites?
Abnormal automaticity
Triggered activity
Re-entry
What is Abnormal automaticity?
Atrial/ ventricular cells lacking automaticity spontaneously depolarise = AP
What is Triggered activity?
extra AP spontaneously triggered during/immediately after repolarisation.
What are the causes and predispositions for Re-enrty mechanism of ectopic sites?
Caused by: slow conduction, part of elec conduction has a long pathway, unidirectional conduction blcok or ARP of re-enerty segment is shorter than time around loop.
Predisposed: myocardial infarction, electrolyte imbalance or ischemia.
How do premature atrial complex (PACs) present on an ECG?
atrial ectopic focus initiates atrial depolarisation rather than SA node pacemaker cells
abnormal P wave (inverted or fused with preceding T wave)
blocked PAC followed by compensatory pause where EDV is enhanced
ECG and cause of Atrial Flutter
-240-350bpm atrial depolarisation rate
- saw-toothed pattern of P waves
- ventricular rate < atrial rate
cause
- reentry circuit in RA
ECG and cause of Atrial Fibrillation?
ECG
chaotic atrial depolarisation accompanied by irregular ventricular depolarisation
absent P waves
Cause
multiple and constantly changing reentry waves
AF treatment and complications
Complications
asynchronous atrial contraction/ relaxation fails to pump blood → stagnation → clots
Treatments
electrical cardioversion
anti-arrhythmic drugs
Premature Ventricular Complexes ECG and causes
Broad QRS complex
Prolonged and inverted T waves
excitation encompasses V but not A
CHD
Electrolyte imbalance
Drug overdose
Premature Complexes treatment and compicatioons
Complications
Frequent PVCs may diminish CO –> VT/VF
Treatment
Antiarrhythmic drugs
VT ECG and causes
≥3 consecutive QRS complexes HR >100bpm
QRS complex blend into ST-T waves at higher rates → large undulating waves
MI
high catecholamine levels
electrolyte imbalances
ischemia
complications and treatment of VT
complications
serious and potentially fatal dysrhythmia due to compromised CO
Treatments
CPR
electrical cardioversion
antiarrhythmic drugs
cause and ECG of VF
rapid chaotic rhythm which is completely uncoordinated
ventricular muscle quivers rather than contracting in a coordinated manner
Cause
reentry
Complications and treatment of VF
Complications
severely compromised CO
Treatments
electrical cardioversion
antiarrhythmic drugs
what rhythms can you use a defib on?
VF
pVT
what are the types of Re-entry?
Functional re-entry
Part of elec conduction is abnormally slow
Anatomical re-entry
Electrical conduction goes through abnormally long pathway
What are the requirements for re-entry?
Functional/ anatomical loop
ARP of re-entered segment is shorter than conduction time around loop
Unidirectional conduction block within loop
What are the 3 classes of dysrthmias and what are their subgroups?
Abnormal rates of sinus rhythm
(sinus brachy cardia, tachycardia, arrest or sick sinus syndrome)
Disturbances of the conduction system (Escape rhythms and conduction blocks)
Abnormal Sites of Impulse initiation (inappropriate automaticity, triggered activity and re-entry)
cardoversion vs defib
what rhythms do you use cardioversion on?
Cardioversion is synchronized with the heart’s electrical activity, while defibrillation is not.
Cardioversion uses lower-energy shocks compared to defibrillation.
Defibrillation is typically an emergency procedure, while cardioversion can be planned or urgent
what rhythms do you use cardioversion on?
Atrial fibrillation (AFib)
Atrial flutter
Atrial tachycardia
Supraventricular tachycardia
What is the cause of Abnormal Automaticicty?
Leaky Na/Ca in phase 4
Ischaemia and Low ATP (can’t maintain ion gradients)
Electrolyte imbalance
What are EADs?
second AP triggered early in RRP (P3)
VG Ca channels recover form inactivation before membrane potential is below threshold
What are DADs?
dep after rep is complete
high CA and SR Va = CA release from SR to evoke AP
Mobitz TI vs TII
1- progressive fatigue of AV node
2- sudden failure of His-Purkinje system
1- PR progressively lengthens
2- Constant PR interval
1- junctional escape rythym
2- ventricular escape rythym
How does ischemia compromise ability of contractile myoctyes to maintain RMP
decreased ATP production as changes to anaerobic condition, impaired ion pump and altered ion gradient
How does elevated Ca in myoplasm and SR trigger DADs?
SR overloaded with Ca and is spontaneously released –> sudden increased in Ca activates NCX –> forward mode pumps out Ca and Na –> depolarisation in Phase 4 –> reaches threshold –> DAD
