C245: BRADYARRHTYMIAS: DISORDERS OF AV NODE

Question 1

• electrical gatekeeper to the ventricle

Answer 1

AV node

Question 2

Depolarization of AV node is mediated by ________ influx vs ventricular myocytes which are mediated by ________influx

Answer 2

Depolarization of AV node is mediated by CALCIUM influx vs ventricular myocytes which are mediated by SODIUM influx

Question 3

AV NODE AUTOMATICITY = ________ beats/ min

Answer 3

AV NODE AUTOMATICITY = 20-60 beats/ min

Question 4

PARTS of AV JUNCTIONAL AREA (3)

Answer 4

PARTS of AV JUNCTIONAL AREA (3)
- transition cell zone
- compact AV node
- penetrating part of His bundle

Question 5

LOCATION OF AV NODE:
- beneath the _____
- posterior: ________
- anterior: ________
- superior: ___________

Answer 5

LOCATION OF AV NODE:
- beneath the R atrial endocardium at the apex of triangle of Koch (3 landmarks…)
- posterior: coronary sinus ostium
- anterior: septal tricuspid valve annulus
- superior: tendon of Todaro

Question 6

TWO FUNCTIONAL PATHWAYS IN AV NODE:

Answer 6

TWO FUNCTIONAL PATHWAYS IN AV NODE:
- SLOW pathway. - inferior node extension
- FAST pathway

Question 7

What is decremental conduction

Answer 7

DECREMENTAL CONDUCTION
- slowing pf conduction with increasingly rapid rates of stimulation

Question 8

The most rapid conduction in the heart is observed in what part

Answer 8

The most rapid conduction in the heart is observed in Purkinje cells (1–3 m/s)

Question 9

BLOOD SUPPLY TO THE PENETRATING AV BUNDLE (2)

Answer 9

BLOOD SUPPLY TO THE PENETRATING AV BUNDLE:
- AV nodal artery
- first septal perforator of the left anterior descending coronary artery

Question 10

tThe AV node is highly innervated with postganglionic sympathetic and parasympathetic nerves; however, these parts (2) are minimally influenced by autonomic tone.

Answer 10

The AV node is highly innervated with postganglionic sympathetic and parasympathetic nerves; however, the bundle of His and distal conducting system are minimally influenced by autonomic tone.

Question 11

Mobitz II block has more serious implications, including a risk of sudden death. It is infranodal in location and associated with a less reliable escape rhythm
**likely infranodal if (2)

Answer 11

1. PR interval < 160ms prior to the AV conduction
   2. QRS is wider than normal (VS narrow QRS suggestive of block in the AV node or proximal His)

Question 12

________heart block involves complete AV dissociation with a ventricular rate that is slower than the atrial rate

Answer 12

Complete heart block (third-degree block) involves complete AV dissociation with a ventricular rate that is slower than the atrial rate

Question 13

• most common causes of acquired conduction disease (2)

Answer 13

Fibrosis and Sclerosis

Question 14

LEV’S DISEASE VS LENEGRE’S DISEASE

Answer 14

• LEV’S DISEASE - results from proximal bundle branch fibrosis
• LENEGRE’S DISEASE- from sclerodegeneragive process that pccurs in a younger age group and involves more DISTAL portiona of the bundle branches

Question 15

What is Bejold -Jarisch reflex

Answer 15

• triad of responses (apnea, bradycardia, and hypotension)
• an inhibitory reflex usually denoted as a cardioinhibitory reflex defined as bradycardia, vasodilation, and hypotension resulting from stimulation of cardiac receptors.

Question 16

Lyme carditis is due to what organism

Answer 16

Borrelia burgdoferi

Question 17

Where is the location of HEART block in LYME CARDITIS

Answer 17

• AV block is typically at the level of the AV node with narrow junctional escape rhythm >40 beats/min

Question 18

AV block in the setting of infective endocarditis should raise concern for _________

Answer 18

AV block in the setting of infective endocarditis should raise concern for perivalvular abscess

Question 19

Refers to the degenerative changes in the summit of the ventricular septum, central fibrous body, and aortic and mitral annuli

Answer 19

Sclerosis of the left cardiac skeleton

Question 20

what decade does sclerosis of left cardiac skeleton begins

Answer 20

begins at 4th decade of life

Question 21

most common cause of AV node dysfunction:

Answer 21

• age-dependent progressive fibrosis of the conduction system

Question 22

Diagnostic testing in the evaluation of AV block is aimed at_______ what objective

Answer 22

determining the level of conduction block

Question 23

EFFECT OF EXERCISE in AV Node dyfunction (heart rate)
- narrow QRS complex VS wide QRS complex level

Answer 23

EFFECT OF EXERCISE in AV Node dyfunction
- narrow QRS complex: level of AV node/ proximal His
- Exercise increases HR
- Wide QRS complex: distal eme
- Exercise does not affect HR

Question 24

• provides information about conduction at all levels of the AV conduction axis

Answer 24

His bundle electrogram

Question 25

AH interval vs HV interval

Answer 25

AH interval
- time from the most rapid deflection of the atrial electrogram in the His bundle recording to the His electrogram
- represents conduction through the AV node and is normally <130 ms

HV interval
- time from the His electrogram to the earliest onset of the QRS on the surface ECG
- represents the conduction time through the His-Purkinje system and is normally ≤55 ms

Question 26

Mobitz I second-degree AV block at short atrial paced cycle lengths is a normal response. When is it abnormal….

Answer 26

when it occurs at atrial cycle lengths >500 ms (<120 beats/min) in the absence of high vagal tone, it is abnormal

Question 27

In a general sense, the lower in the conduction system that an escape rhythm is occurring, the HIGHER is the reliability of the escape rhythm

True or False

Answer 27

FALSE, kasi dapat…

In a general sense, the lower in the conduction system that an escape rhythm is occurring, the LOWER is the reliability of the escape rhythm

Question 28

permanent pacing is recommended regardless of symptoms ( in these 3 types of AV Blocks)

Answer 28

permanent pacing is recommended regardless of symptoms ( in these 3 types of AV Blocks)
- acquired Mobitz type II AV block
- high-grade AV block
- third-degree AV block

Question 29

Permanent pacing is also indicated in the ff:
- neuromuscular disease and other progressive cardiomyopathies
- symptomatic bradycardia and irreversible second- or thirddegree AV block, regardless of the cause or level of block in the conducting system
- block is demonstrated to be intra- or infra-His or is associated with a wide QRS complex.

Answer 29

:)

Question 30

The circumstances in which pacing is indicated in acute MI are: (2)

Answer 30

The circumstances in which pacing is indicated in acute MI are:
- persistent second- or third-degree AV block, particularly if symptomatic,
- and transient second- or third-degree AV block associated with bundle branch block

Question 31

Fascicular blocks that develop in acute MI in the absence of other forms of AV block require pacing.
True or False?

Answer 31

False kasi…

it does not require pacing

Question 32

________involves placement of an additional pacing lead in a lateral or anterolateral branch of the coronary sinus to allow for simultaneous right ventricle and lateral left ventricle pacing leading to a more physiologic left ventricular contraction

Answer 32

Cardiac resynchronization therapy (CRT)