Tachyarrhythmias Flashcards
Questions to ask
- Rate
- Regularity
- Narrow or wide QRS
- Atrial activity
- P and QRS relationship
- Onset gradual or sudden and rate variation
SVT rate range
150-200bpm
VT rate range
usually >170
MAT rate range
<160bpm
Reg irr could mean:
a flutter, SVT Type I 2 degree AV Block
Irr irr could mean:
a fib, MAT, Polymorphic VT, a flutter with variable AV block
Narrow QRS means
We can exclude VT
Wide QRS means
We consider VT, aberrancy, preexcitation, hyperkalemia
When looking at P waves, consider:
Are they the same? Yes, then it’s Sinus Tach. Retrograde p waves? Yes, SVT. Flutter waves? No discernable atrial activity? If irr, a fib. If reg, SVT or VT.
What does it mean when P waves are after QRS?
Highly suggestive of SVT.
AV dissociation
Highly suggestive of SVT.
Fusion beats means and what is it indicating?
Supraventricular impulse and ventricular impulse coincide making a hybrid complex. Highly suggestive of VT.
Capture beats
Normal QRS in midst of AV dissociation. Highly suggestive of VT. SA node “captures” electrical activity.
Possible arrhythmias with abrupt onset w/o rate variation.
a-flutter, SVT, and VT.
Possible arrhythmias w/ rate variation.
a-flutter w/ variable block or MAT.
Possible arrhythmias with gradual onset.
VT, Atrial Tach. Has to be >10s.
Phases of normal automaticity
SA node:
Phase zero- Inward Ca2+
Phase 3- Outward K+
Phase 4- Slow inward Na+ and Ca2+
Automaticity rates
Sinoatrial node 50-90, latent pacemakers in atria 4-60, Atrioventricular Junction (AV node) 40-60, His/Purkinje 15-40.
What is an escape rhythm?
Any form of electrical activity that causes impulses that doesn’t derive from the SA node.
What causes (normal) increase automaticity?
Increase SNS, decrease PSNS, digoxin toxin, hypokalemia.
What causes (abnormal) increase automaticity?
Acute ischemia/reperfusion, CHF
What is the general concept of reentry mechanism?
reexciting the heart as a self-propagating mechanism.
Examples of macro-reentry mechanisms.
Large enough to be mapped:
Atrial flutter and AVRT
Examples of micro-reentry mechanisms.
Too small to be mapped:
A-fib, Atrial tachycardia.
Triggered activity means:
depolarization oscillation of membrane potential occurs after an action potential. One is strong enough to create an action potential. “Afterdepolarization”.
Pre-excitation means:
Has an accessory pathway. An early activation of ventricles due to electrical activity bypassing the AV node. These pathways are formed during fetal development. WPW or AVRT.
Types of tachyarrhythmia mechanisms:
Reentry, pre-excitation, and triggered activity.
In the field, what is the biggest thing to differentiate with tachyarrhythmias?
Whether it is SVT or VT. VT is mono/polymorphic. SVT includes every tachyarrhythmia involved above the ventricles. From there, you can deduce what type of SVT it is. Is it a fib, a tach, a flutter, MAT, AVRT, AVNRT etc.?
Orthodromic AVRT mechanism
Signal conducts down normal pathway and retrograde up accessory pathway. Re-entrant begins. An example is WPW.
Orthodromic AVRT EKG signs
Narrow QRS, retrograde P wave (upside down), P wave after QRS
Antidromic AVRT mechanism
Impulse moves down accessory pathway and works retrograde up normal pathway. Reentrant begins. Rare.
Antidromic AVRT ECG signs
Wide QRS (probably due to slow conduction of accessory), P waves not discernable. QRS in same direction as delta wave in NSR.
Brugada criteria to help diagnose VT.
Go through the checklist, if yes, no need to continue down.
- RS complex absent in all precordial leads. Either all S or R waves.
- RS interval in one precordial lead is >100ms
- AV dissociation
- Look for VT morphology in V1,2, and 6.
VT morphology in V1, V2 and V6 when RBBB morphology.
V1: Smooth monomorphic R waves, Notched left side R wave, qR pattern.
V6: QS morphology (no R), R/S ratio <1 (w/ LAD present).
VT morphology in V1, V2, and V6 when LBBB morphology.
V1: initial R wave is >30-40ms, notching or slurring of S wave, RS interval >60-70ms (start of R to nadir of S).
V6: QS (absent R), qR pattern (small q, large R, no s). (Remember that absent Q waves in V6 with top notching indicates LBBB).
Vereckei Algorithm (additional advanced help to distinguish VT).
aVR with initial dominant R wave indicates VT. Dominant R’ indicates SVT with LBBB (most commonly seen in tricyclic antidepressant poisoning).
