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41 Cards in this Set
- Front
- Back
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Is SVT bad?
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Not that bad. We typically just aim to reduce symptoms and prevent the dreaded: tachycardia induced cardiomyopathy
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How do we differentiate SVT from Sinus Tachycardia?
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Sinus tachycardia comes on gradually. SVT is sudden on, sudden off.
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SVT is usually a narrow complex. What are some reasons we could get a wide complex?
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- Diseased bundle
- Bundle of Kent/bipass (pre-excitation) - QRS can naturally widen at fast heart rates |
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What do we need in order to get AVNRT?
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Two pathways:
One fast with long refractory period One slow with short refractory period |
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What is the most common SVT in adults?
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AVNRT
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What percentage of SVT does AVNRT account for?
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60%
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Wait.. what is the most common SVT in adults?
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AVNRT
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AVRT is due to what?
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An accessory pathway
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What are the two states of AVRT?
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Antidromic or orthodromic
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Which type gives you a wider QRS and why?
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Antidromic gives a wide QRS because the impulse has to travel down and depolarize through the muscle. Orthodromic follows the normal pathway so it depolarizes together.
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What is a common type of orthodromic one that leads to pre-excitation?
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Wolf-Parkinson-White. We see pre-excitation on the ECG
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In order to have "Wolf parkinson white syndrome" you need:
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ECG findings AND symptoms
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What is Atrial Tachycardia
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A tachycardia that develops from a focus within the atrium. Is is the least common type of SVT.
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What does it mean if you see an ECG with missed conduction?
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Probably not an AVNRT or AVRT. These will always conduct to the ventricles. You may lose P waves in AVNRT, but it will still conduct.
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What is the basis for diagnosing SVT?
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Disturb the AV node and see what happens.
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What are some mechanisms of disturbing the AV node?
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Valsalva, Carotid Massage,
Adenosine |
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We slow conduction in the AV node. Basically blocking it.
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If it stops, then we know the AV node is in the circuit. IT could be AVRT or AVNRT.
If it does not stop then the AV node is not involved in the circuit and it's probably Atrial Tachycardia |
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We tend to be conservative for SVT. Really only treat for symptomatic relief and prevention of:
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Tachycardia induced cardiomyopahy
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An accessory pathway (WPW) with AFib can be very bad.
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If there is an accessory pathway that can conduct every beat, we're in trouble. If each beat is conducted we can get Vfib.
If we see a wide complex with irregularly irregular beats and a slurred upstroke, this is very very bad. don't miss this |
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WPW does have a small risk of sudden death if Afib develops
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yes
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Pre-excitation AFib is bad bad bad
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it is bad
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What are some treatments for SVT?
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AV node blocking: betablockers for rate control, Cablockers
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Generally try to ablate.
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It is a good first line in many places. We don't want ot have to try antiarrhythmics if we can avoid it.
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How can Afib lead to heart failure?
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Tachycardia Induced Cardiomyopathy
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Where does most atrial fibrilation originate?
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In the pulmonary veins
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If we pace the heart fast, we can induce Afib
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it is the gift that keeps on giving
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What are the classifications of Afib?
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Paroxysmal <week
Pesistant >1week Permanent more than a year, refractory to cardioversion |
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What is the mainstay of treatment for Afib?
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Thromboembolism protection
SYmptom control Prevention of Tachycardia induce cardiomyopathy |
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If we are cardioverting someone, do they need embolism protection?
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If they have had Afib for more than 48hours, they should have protection
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CHADS2 score
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is a score
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Is dibigatran good for people with mechanical valves?
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NOPE NOPE NOPE POOP
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In Afib, there is no mortality benefit for Rate vs. rhythm control. Which do we usually start wiht?
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Rate control. If they are still symptomatic, maybe switch the rhythm control.
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What are some factors that favour rate control over rhythm control?
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Persistant AF
Recurrent AF Less symptomatic Older >65 HTN |
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In patients with paroxysmal AF, or more symptomatic,
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consider rhythm control
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What do we commonly use for Rate Control?
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Beta blockers, Calcium channel blockers
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What are the first line type of drugs for rhythm control?
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Antiarrhythmics are first line control for rhythm. Catheter ablation is also first line if available.
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What classes of antiarrhythmics should be used for rhythm control here?
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Class IC
Sotalol (class III K blocker) - prolongs repolarization |
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When should amiodarone be used?
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amiodarone should be a second line treatment
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Is ablation good for AFib?
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it is 70-85%. so it can work but definitely not as well as in SVT where it is first line
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Rhythm control has not been shown to alter mortality. it is for
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symptoms only
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What is most common circuit for A flutter?
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Around the tricuspid valve
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