Tachyarrhythmias

Question 1

Questions to ask

Answer 1

1. Rate
2. Regularity
3. Narrow or wide QRS
4. Atrial activity
5. P and QRS relationship
6. Onset gradual or sudden and rate variation

Question 2

SVT rate range

Answer 2

150-200bpm

Question 3

VT rate range

Answer 3

usually >170

Question 4

MAT rate range

Answer 4

<160bpm

Question 5

Reg irr could mean:

Answer 5

a flutter, SVT Type I 2 degree AV Block

Question 6

Irr irr could mean:

Answer 6

a fib, MAT, Polymorphic VT, a flutter with variable AV block

Question 7

Narrow QRS means

Answer 7

We can exclude VT

Question 8

Wide QRS means

Answer 8

We consider VT, aberrancy, preexcitation, hyperkalemia

Question 9

When looking at P waves, consider:

Answer 9

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.

Question 10

What does it mean when P waves are after QRS?

Answer 10

Highly suggestive of SVT.

Question 11

AV dissociation

Answer 11

Highly suggestive of SVT.

Question 12

Fusion beats means and what is it indicating?

Answer 12

Supraventricular impulse and ventricular impulse coincide making a hybrid complex. Highly suggestive of VT.

Question 13

Capture beats

Answer 13

Normal QRS in midst of AV dissociation. Highly suggestive of VT. SA node “captures” electrical activity.

Question 14

Possible arrhythmias with abrupt onset w/o rate variation.

Answer 14

a-flutter, SVT, and VT.

Question 15

Possible arrhythmias w/ rate variation.

Answer 15

a-flutter w/ variable block or MAT.

Question 16

Possible arrhythmias with gradual onset.

Answer 16

VT, Atrial Tach. Has to be >10s.

Question 17

Phases of normal automaticity

Answer 17

SA node:
Phase zero- Inward Ca2+
Phase 3- Outward K+
Phase 4- Slow inward Na+ and Ca2+

Question 18

Automaticity rates

Answer 18

Sinoatrial node 50-90, latent pacemakers in atria 4-60, Atrioventricular Junction (AV node) 40-60, His/Purkinje 15-40.

Question 19

What is an escape rhythm?

Answer 19

Any form of electrical activity that causes impulses that doesn’t derive from the SA node.

Question 20

What causes (normal) increase automaticity?

Answer 20

Increase SNS, decrease PSNS, digoxin toxin, hypokalemia.

Question 21

What causes (abnormal) increase automaticity?

Answer 21

Acute ischemia/reperfusion, CHF

Question 22

What is the general concept of reentry mechanism?

Answer 22

reexciting the heart as a self-propagating mechanism.

Question 23

Examples of macro-reentry mechanisms.

Answer 23

Large enough to be mapped:

Atrial flutter and AVRT

Question 24

Examples of micro-reentry mechanisms.

Answer 24

Too small to be mapped:

A-fib, Atrial tachycardia.

Question 25

Triggered activity means:

Answer 25

depolarization oscillation of membrane potential occurs after an action potential. One is strong enough to create an action potential. “Afterdepolarization”.

Question 26

Pre-excitation means:

Answer 26

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.

Question 27

Types of tachyarrhythmia mechanisms:

Answer 27

Reentry, pre-excitation, and triggered activity.

Question 28

In the field, what is the biggest thing to differentiate with tachyarrhythmias?

Answer 28

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.?

Question 29

Orthodromic AVRT mechanism

Answer 29

Signal conducts down normal pathway and retrograde up accessory pathway. Re-entrant begins. An example is WPW.

Question 30

Orthodromic AVRT EKG signs

Answer 30

Narrow QRS, retrograde P wave (upside down), P wave after QRS

Question 31

Antidromic AVRT mechanism

Answer 31

Impulse moves down accessory pathway and works retrograde up normal pathway. Reentrant begins. Rare.

Question 32

Antidromic AVRT ECG signs

Answer 32

Wide QRS (probably due to slow conduction of accessory), P waves not discernable. QRS in same direction as delta wave in NSR.

Question 33

Brugada criteria to help diagnose VT.

Answer 33

Go through the checklist, if yes, no need to continue down.

1. RS complex absent in all precordial leads. Either all S or R waves.
2. RS interval in one precordial lead is >100ms
3. AV dissociation
4. Look for VT morphology in V1,2, and 6.

Question 34

VT morphology in V1, V2 and V6 when RBBB morphology.

Answer 34

V1: Smooth monomorphic R waves, Notched left side R wave, qR pattern.
V6: QS morphology (no R), R/S ratio <1 (w/ LAD present).

Question 35

VT morphology in V1, V2, and V6 when LBBB morphology.

Answer 35

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).

Question 36

Vereckei Algorithm (additional advanced help to distinguish VT).

Answer 36

aVR with initial dominant R wave indicates VT. Dominant R’ indicates SVT with LBBB (most commonly seen in tricyclic antidepressant poisoning).