TOPIC23: supraventricular arrhythmias Flashcards
types of arrythmias
- bradycardias: HR<60/min
- sinus bradycardia
- sino-atrial blocks
- AV-blocks
- bradycardia absoluta
- tachycardia: HR >100/min
-regular/irregular
-narrow QRS/ wide QRS
SVT:
-FOCAL: abnormal automaticity or triggered activity
-REENTRY: simple/complex
Supraventricular arrhythmias originate in the atria or the AV node.
symptoms can come suddenly and may go away without treatment. They can last a few minutes or as long as 1-2 days.
The rapid beating of the heart during SVT can make the heart less effective as a pump–> CO is decreased and BP drops.
symptoms of arrythmias (5)
- palpitation (most common symptoms in cardio):
- regular/irregular
- sudden/gradual
- fast/slow - fatigue/weakness/dizziness
- dyspnea, syncope
- angina pectoris
- cardiac arrest
SVTs from a SINOATRIAL source
- Sinus tacchycardia
- inappropriate sinus tachycardia
- SANRT
SVTs from a ATRIAL source
- (Unifocal) Atrial tacchycardia (AT)
- multifocal atrial tacchycardia (MAT)
- atrial flutter
SVTs from an ATRIOVENRTICULAR source
- AVNRT
- AVRT
- Junctional ectopic tacchycardia
SVTs from a ATRIAL source : MAT
- irregular rhythm occurring at 100-200bpm
- random firing of several different ectopic atrial foci
- common in people with lung disease
- rarely requires treatment
- P waves originate from multiple sites–> at least 3 different P wave morphologies, PR intervals vary aswell
SVTs from an ATRIOVENRTICULAR source: AVNRT
- reentry circuit inside the AV node
- ventricular (anterograde) and atrial (retrograde) activation in the same time.
- the retrograde P wave is hidden in the QRS or it may deform the terminal part of the QRS.
SVTs from an ATRIOVENRTICULAR source: AVRT
- conduction through the accessory pathway
- retrograde P wave is the ST-T
- PR interval is shortened (<0,12 sec)
- narrow QRS: orthodromic
- wide QRS: antidromic
SVTs from a SINOATRIAL source: Sinus tacchycardia
-sinus rate >100bpm
-sinus P wave possibly hidden in T or ST segment
A)may be physiologic:
-exercise
- pregnancy
- emotion
B) pathologic:
- anemia
-drugs (caffeine, cocaine)
-hyperthyroidism
-pain, hypoxia, fever, infection, sepsis, shock
-hypovolemia, cardiac tamponade
-AHF
-Pheochromocytoma
-CALLED inappropriate sinus tacchycardia if no underlying cause found–> treated with beta blockers
SVTs from a SINOATRIAL source: SANRT
- a rare cause of narrow complex tacchycardia due to micro-reentrant circuit within the SA-node
- P wave on the ECG is identical to sinus tacchycardia making it difficult to diagnose.
- beta blockers or Ca channel blockers are first line treatment.
- TREAT: modification of SA-node by RADIOFREQUENCY ABLATION (RFA)
SVTs from a ATRIAL source: Atrial tachycardia
- regular atrial rhythm with a P rate >100
- an automatic focus of atrial cells firing faster than the SA node
- P wave morphology (not sinus P) and axis of the P wave can be used to predict the location of the source.
- treatment is needed only for symptomatic patients or permanent tachycardia:
- beta blockers or calcium blockers slow the atrial rate and ventricular response by AV blockade.
- class I or III antiarrythmics suppress tachycardia
- some may be terminated by IV adenosine or be curative by RFA (ablation)
- occurs in normal hearts or in digitalis toxicity, pulm disease or cardiac disease.
SVTs from a ATRIAL source: Atrial flutter
- reentry in the right atrium, around the annulus of the tricuspid valve.
- P wave rate >240bpm
- The ventricular rate depends on the AV node function
- absence of an isoelectric baseline between deflections
- Saw-tooth like F waves. F waves may be masked by the QRS
treatment:
- synchronized direct current cardioversion effectively restores sinus rhythm but if often reoccurs
- drug therapy not very effective( large doses needed that have side effects)
- RFA is the most effective way of maintaining sinus rhythm and can be curative.
- anticoagulation medications like AF
- the ablation of the AV node and implantation of a permanent pacemaker is a palliative solution
SVTs from an ATRIOVENRTICULAR source : AVNRT
-approximately 200 bpm
-immediate onset
-often triggered by an atrial extrasystole
-most common cause of a narrow complex tachycardia in pts with normal hearts, typically in young adults. more common in women than men.
-causes paroxysms of severe palpitations with a pounding in the neck due to reflux of blood into the jugular veins caused by simultaneous atrial and ventricular contraction.
- the circuit most often involves two tiny pathways , one faster and one slower within the AV node
-both atria and ventricles stimulated simultaneously meaning that a retrogradely conducted p wave is buried within or occurs after the regular narrow QRS complexes.
IMPORTANT: to differentiate from junctional tachycardia HR>140bpm , in junctioncal it’s <140bpm
treatment:
- IV adenosine
- vagal maneuver
- first line treatment for recurrent symptomatic episodes is RFA, which can be curative.
SVTs from an ATRIOVENRTICULAR source: AVRT
-one portion of the circuit is usually the AV node and the other an abnormal accessory pathway from the atria to the ventricle.
syndromes with accessory pathways:
- Wolff-Parkinson White syndrome:
- bundle of Kent
- lies parallel to the AV node and conducts impulses faster than the AV node, meaning the PR interval will be < 0.12sec
- orthodromic vs antidromic
- antidromic is very dangerous in AF as all atrial impulses (300bpm) will pass down to the ventricles initiating VT–>VF - Lown-Ganon-Levine Syndrome:
- James bundle (intranodal fibers that bypasses AV nodal delay)
- QRS appears more or less normal as the accessory pathway is similar to the AV node
- no delta waves
treatment:
- RFA (radiofrequency ablation) of the slow pathway
- drugs such as flecainide and propafenone slow conduction in the accessory pathway.
SVTs from an ATRIOVENRTICULAR source : Junctional tachycardia
<140bpm–> differentiated from AVNRT
-treat with beta-blockers, Flecainide and Propafenone
