C245: BRADYARRHTYMIAS: DISORDERS OF AV NODE Flashcards
- electrical gatekeeper to the ventricle
AV node
Depolarization of AV node is mediated by ________ influx vs ventricular myocytes which are mediated by ________influx
Depolarization of AV node is mediated by CALCIUM influx vs ventricular myocytes which are mediated by SODIUM influx
AV NODE AUTOMATICITY = ________ beats/ min
AV NODE AUTOMATICITY = 20-60 beats/ min
PARTS of AV JUNCTIONAL AREA (3)
PARTS of AV JUNCTIONAL AREA (3)
- transition cell zone
- compact AV node
- penetrating part of His bundle
LOCATION OF AV NODE:
- beneath the _____
- posterior: ________
- anterior: ________
- superior: ___________
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
TWO FUNCTIONAL PATHWAYS IN AV NODE:
TWO FUNCTIONAL PATHWAYS IN AV NODE:
- SLOW pathway. - inferior node extension
- FAST pathway
What is decremental conduction
DECREMENTAL CONDUCTION
- slowing pf conduction with increasingly rapid rates of stimulation
The most rapid conduction in the heart is observed in what part
The most rapid conduction in the heart is observed in Purkinje cells (1–3 m/s)
BLOOD SUPPLY TO THE PENETRATING AV BUNDLE (2)
BLOOD SUPPLY TO THE PENETRATING AV BUNDLE:
- AV nodal artery
- first septal perforator of the left anterior descending coronary artery
tThe AV node is highly innervated with postganglionic sympathetic and parasympathetic nerves; however, these parts (2) are minimally influenced by autonomic tone.
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.
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)
- 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)
________heart block involves complete AV dissociation with a ventricular rate that is slower than the atrial rate
Complete heart block (third-degree block) involves complete AV dissociation with a ventricular rate that is slower than the atrial rate
- most common causes of acquired conduction disease (2)
Fibrosis and Sclerosis
LEV’S DISEASE VS LENEGRE’S DISEASE
- 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
What is Bejold -Jarisch reflex
- 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.
Lyme carditis is due to what organism
Borrelia burgdoferi
Where is the location of HEART block in LYME CARDITIS
- AV block is typically at the level of the AV node with narrow junctional escape rhythm >40 beats/min
AV block in the setting of infective endocarditis should raise concern for _________
AV block in the setting of infective endocarditis should raise concern for perivalvular abscess
Refers to the degenerative changes in the summit of the ventricular septum, central fibrous body, and aortic and mitral annuli
Sclerosis of the left cardiac skeleton
what decade does sclerosis of left cardiac skeleton begins
begins at 4th decade of life
most common cause of AV node dysfunction:
- age-dependent progressive fibrosis of the conduction system
Diagnostic testing in the evaluation of AV block is aimed at_______ what objective
determining the level of conduction block
EFFECT OF EXERCISE in AV Node dyfunction (heart rate)
- narrow QRS complex VS wide QRS complex level
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
- provides information about conduction at all levels of the AV conduction axis
His bundle electrogram
AH interval vs HV interval
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
Mobitz I second-degree AV block at short atrial paced cycle lengths is a normal response. When is it abnormal….
when it occurs at atrial cycle lengths >500 ms (<120 beats/min) in the absence of high vagal tone, it is abnormal
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
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
permanent pacing is recommended regardless of symptoms ( in these 3 types of AV Blocks)
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
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.
:)
The circumstances in which pacing is indicated in acute MI are: (2)
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
Fascicular blocks that develop in acute MI in the absence of other forms of AV block require pacing.
True or False?
False kasi…
it does not require pacing
________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
Cardiac resynchronization therapy (CRT)
