Chapter 22 & 23 - Arrhythmias and Antiarrhythmics

Question 1

What is the blood supply of the SA node?

Answer 1

RCA (55%) LCx (45%)

Question 2

What is blood supply of the AV node?

Answer 2

RCA (90%), LCx (10%)

Question 3

What does and LAD infarct rarely result in a LPFB?

Answer 3

The LPIF receives blood from the AVN along in 50% and AVN and LAD in other 50%, as opposed to the RBB and LASP which get LAD 50% and LAD/AVN 50%. Therefore an LAD lesion could result in RBBB/LAFP but not LPFB

Question 4

What are three mechanisms of tachyarrythmia?

Answer 4

1) Increase automaticity 2) Reentry 3) Afterdepolarization

Question 5

Draw a reentry circuit and explain.

Answer 5

See diagram.

Question 6

What are normal intervals:

Pwave

PR

QRS

QTc

Answer 6

P: <0.1sec/0.3mv

PR: 0.12-0.20 sec

QRS <90ms

QTc <0.39-0.45 (men) 0.46 (women)

Question 7

What is the risk of embolic stroke in cardioversion in chronic afib?

Answer 7

1.2-1.5% (off anticoag)

Question 8

What are concerning historical features that palptiations could be VT?

Answer 8

Dizzyness, syncope, presyncope

Question 9

List features of sinus arrthymia

Answer 9

>0.12sec difference between shortest and longest P-P intervals

Rate increases with inspiration and decreases with expiration due to change in vagal tone (Bainbridge reflex)

Question 10

List characteristics of PACs

Answer 10

Appear before next expected beat

P have different shape/axis

May or may not be conducted

Associated conditions: lung disease, IHD, dig toxic, tobacco, caffiene

Question 11

List causes of sinus bradycardia

Answer 11

Physiologic - athlete, vagal, sleep

Pharmacologic - BB, CCB, Dig, opiod,

Pathologic -inferior MI, high ICP, hypothyroid

Question 12

What is Sick Sinus Syndrome?

Answer 12

Abnormal impulse generation and conduction

Results in various tachy and bradyarrhythmias

Junctional tach, Afib, AFL, SVT, sinus brady, SA block