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Arrhythmias 1 Flashcards

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1
Q

What are the 2 main indications for doing an ECG?

A
  1. Arrhythmias, tachy or bradycardia i.e HB too fast, slow or eratic
  2. For monitoring anaesthesia
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2
Q

Other indications for ECG

A

Cardiac/ cardiotoxic drugs

Electolyte disturbances or after IV electrolytes

Reperfusion

Enlarged cardiac chambers

Pericardiocentesis

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3
Q

What is the physio rhythm?

A

Originates in SA node (nomotop)

Resp rhythm is physio in dogs because have higher vagal tone, sinus rhythm is physio in cats

Escape beats- from outside sinus, lower pacemakers at lower frequencies

Sometimes AV blocks can be physio in dogs

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4
Q

Normal sinus= sinus arrhythmia

A

Is this the normal PQRS complex?

P wave: atrial depol- followed by a small break of the AV node where NO wave form is visible

QRS complex- the impulse travelsv quiclkly to the ventric fibres

ALL depol is followed by repol (T-wave) but T-wave of atrial repol is. not seen on ecg

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5
Q

Physio sinus arr and wandering pacemaker

A

This is resp arr!! insp shorter distances that exp

Atria can be activated from different points hence the variation

heart beats are at the end and beginning of systole

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6
Q

Classification of arr

A

1.Impulse form:

  • normal or incr HR
  • abnormal automaticity
  • Triggered activity
  • Reentry or block

Conduction

  • slow, block can be uni or bidirectional
  • Normal or decr HR

Arr- dysrhythmias

  • tachy, brady, arr
  • Ectopic beats (except physio escape beats)
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7
Q

Impulse formative disorders, what are the 2 origins?

A

Nomtop- when from the sinus node

Heterotop/ectopic- from outsude the node!

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8
Q

Nomtop

A

Sinus tachycard

Sinus bradycard

Arrest

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9
Q

Hterotop/ectopic

A

Supra vetric:

  • Atrial extrasystolde (outside atria)
  • Foacal atrial tachycard
  • Atrial fibrillation= disorganised
  • atrial flutter= large reentry
  • junctional tachycard
  • junctional extrasystole

Ventricular:

  • extrasystole
  • Tachycard
  • Fibrillation, flutter

When is both supraventric and ventric : uses bypass tracts or bypass tachycard: atrioventric reciprocating tachycard

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10
Q

Ectopic/ extrasystole/ premature contractions

A

From anywhere outside the primary!!

Cannot distinguish whether it is coming from atria or ventricles via ausc

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11
Q

Ectopic escape beats

A

From outside the sinus node

  • big pause when there is no sinus node activity
  • in one example- there are no P-waves just QRS complexes, the HR is slow
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12
Q

Premtaure supraventric extrasystole

A

The extra beat is very similar to the sinus beat. there appears to be a very small distance btw the QRS complexes

The QRS complex is NARROW!!

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13
Q

Premature ventric contraction, ventricular extrasystole

A

Early beat is visible

The QRS complex is WIDE!! (how to distinguish from supraventric extrasystole)

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14
Q

Supraventricular premature beat, Non-compensated pause, resetting

A

If supraventric comes too early- there may be a conduction block!

Measure the distances btw the abnormal beats

Supra (originates in sinus) also depolarizes the atria. Sinus beat will come normally

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15
Q

Ventricular premature contraction, fully compensated pause, no resetting

A

It is exactly 2 QRS complexes i.e 2 cardiac cycles

Does not depol the atria therefore the next sinus beat will be a bit abnormal

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16
Q

IImpulse formative disorders- how to distinguish btw supraventric and ventric tachycardia

A

Supraventric will have positive deflections

Ventric tachycard will have negative deflections

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17
Q

Points to look out for if diagnosing ventricular extrasystole (VPC)

A
  • wide QRS
  • No P-wave
  • Abnormal T-wave
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18
Q

Diagnosing Supraventricular extrasystole?

A

Appearance of typical sinus beat

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19
Q

Supraventricular escape beat diagnosis

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A

In this case it was originating from the AV node so there was no P-wave!

20
Q

Diagnosing ventricular escape beats

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A

V. slow rhythm

All beats are abnormal

If sinus in origin then no P-wave (can you conclude that if the origin is SA or AV node that there will be no P-wave?)

LArge, wide, negative QRS complexes

21
Q

Impulse conductive disorders: SA blocks

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A

1st degree: slow conduction

2nd degree: maybe conduction

3rd degree: no conduction

Bundle branch block (BBB) can be left or right

Intraventricular conduction blocks!

22
Q

Blocks can be…

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A

Functional: R bundle branch block is frequent! or when the beat comes too early, before the tissues have regained conductivity

Physio: premature ventric beat with aberrant conduction

Blocked premature supraventricular beat-completely blocked T-wave! In these cases the block is physio but the premature stimulus of the atria is patho!

23
Q

3 main Causes of arr

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A
  1. Structural HD/HF
  2. Systemic illness
  3. Primary: congenital or acquired
24
Q

Structural HD/HF causing arr

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A

Remodelling of heart

Neurohormonal: symp/parasymp, RAAS, Endothelin

Inflamm mediators and FR’s

Hypoxia: atrial fibrillation, in CHF ventric arr are seen

25
Systemic illnesses as cause of arr
Hypoxia, veg tone, temp, electrolytes (Na and K), drugs and toxins * Kidney failure, obstruction of urethra (electrolyte disturbances?) * Addisons * Digoxin OD * Anaesth!!!! * Sepsis, trauma, hypovolaemic shock * Splenic tumour/torsion * Gastric torsion * Brain/SC injury * Pancreatitis * Ileus
26
Congenital/ acquired i.e primary causes of arr
Channelopathies Fibrosis, infarcts, amyloidosis Boxer/bulldog/cat: arrhythmogenic cardiomyopathy- hyper or hypothyreoisis Mini shnauzer and westie: SSS Cocker spaniel: AV block Lab, Boxer: Wolf Parkinson White syndrome- AV acc pathways
27
Consequences of arr
Mostly none! Weakness and syncope if there is interference with the HR Ventric or brady may result in sudden death Worsening of already exisitng HF Bradyarr can cause HF or tachiocariomyopathy (dont know how it would tho?) May damage the myocard-- dilated cardiomyopathy
28
Treatment of arr
first must DIAGNOSE!!! via eCG Cardiac vs extracradiac No treatment if no signs or haemodynamic changes Remember that most antiarr are proarr
29
treatable vs non treatable
Treatable: tachy/brady, supraventric and ventric Usually we don't treat: * atrial or ventric infrequent extrasystoles * Slow idioventricular or junctionsl rhythms * Lone atrial fibrillation * 1st/2nd degree AV blocks * BBB's * Intraventricular blocks * Ventric arr caused by extracardiac cause
30
How to treat the arr
1. Treat the cause! e.g if CHF give diuretics, O2, Pimobendan 2. By Phys methods! Ocular pressire/vagal maneuver- to induce a high vagal tone to overcome the symp tone. Usually in combo with drugs Carotis massage, chest thump 3. Drugs 4. Artificial pacemaker 5. Electric cardioversion 6. Radiofrequency catheter ablation 7. External defibrillators
31
Using catheter mapping and ablation to treat atrial flutter
Occurs when there is re-entry into either the R or L atrium, the AV node tries to filter it out!! Catheter places in the isthmus btw the tricuspid valve and the eustacian valve of the IVC There are multiple pairs of electrodes on the catheter - can locate the circuit when the position correlates with conduction! Heat and E is used to destroy the piece of muscle- no conducting ability anymore!
32
Classes of anti-arr drugs according to the Vaughan-Williams classification
1. Na channel blockers (membrane stabilizers) 2. Beta blockers 3. K channels blockers- delay repol 4. Ca channel blockers 5. Digoxin 6. Atropine
33
Na channel blockers
Reduce slope of phase O and reduce peak of AP Works on cells that use Na for depol ie the atrial and ventric working and purkinje but not on SA or AV nodes treat VENTRIC ARR!! They delay depol and shorten repol SE's: hypoT, convulsions, decr liver metab Will not work if there is hypokalaemia
34
Na channel blockers: 1a
Procainamide - SVT (bypass tract) - Ventric arr
35
Na channel blockers: 1b
Lidocaine and mexiletin - Ventric arr - (some SVT) Rapid binding and dissociation Refractory channels Ischaemic areas Usually dilate vessels therefore would decr BP SE: convulsions
36
Na channel blockers
Flecainide and Propafenon -SVT- bypass tract, atrial flutter! Slow binding and dissociation
37
Beta blockers
Used to treat supraventric arr (they slow the HR0 and ventric arr (in combo) Block the symp discharge to the heart and therefore slow impulse conduction in the AV node (-) ino, chrono, bathmo, dromo
38
Beta blockers: 1st gen
Non-selective Propranolol
39
Beta blockers: 2nd gen
Selective beta 1: Atenolol and Metoprolol
40
3rd gen beta blockers
Carvedilol and bucindolol Non-selective aplha blockade Antiox
41
Repolarization delaying drugs- K channel blockers
Amiodarone and Sotalol Have multiple class effect (I, II, III and IV for amiodarone) Prolong AP and therefore refractory state (are good for reentry?) Treat both atrial and ventric arr
42
Calcium channel blockers
Dihydropyrimidines: Amlopdipine Used to treat hyperT as it dilates the vessles. Used at the end of HF Non-dihydropyrimidines: Verapamil and Diltiazem Slow AV conduction Heart\>vessels Cardiac specific: verapamil\>diltiazem\>amlodipine Treat: SVT arr! they decr the ventric rate in atrial fibrill (-) ino: verapamil\>diltiazem If OD: give IV calcium
43
Digoxin
decr symp and incr parasymp tone Restore baroreceptor function (+) ino- mild Not IV- sympathomimetic effect! maybe proarr Treats: SVT by decr the speed of AV conduction
44
Atropine response test
Record baseline eCG Admin 0.04mg/kgbw of atropine SC Wait for 30 mins Record eCG for min of 2 mins Result: dogs with vagally mediated bradycard will have sinus tachycard\>140 bpm (i.e parasymp induced brady) Some dogs with sinus node disease or patho AV blocks will aslo respond to this test
45
Protocol for a new arr case
Diagnose with eCG Exclude HD Full work up- include electrolytes Atropine responce test 1. O2 2. Sympto: fluids and diuretics 3. treat the arr 4. treat the cause if you know it?? 5. find out if its cardiac (phys, echo, BP) or extracardiac (general parameters, electrolytes, Lyme?) 6. Imaging of abd and thorax
46
Case study of 10yr old male boxer
Syncope Detected arr during phys Echo was normal Labs: LOW BG Abd US: focal lesion in the pancreas Diagnosis: INSULINOMA! i.e a severe systemic disease- mind immediately jumps to the fact that boxers are predisposed to R ventric exntrasystole
47

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