Bradyarrhythmias Flashcards
Percent of SA nodal artery arises from RCA
55-60%
Percent of SA nodal artery arises from Lcx
40-45%
SA node cells exhibit the most rapid __ phase of depolarization
4
Absence of autonomic influence of SA node leads to an intrinsic HR that is normally ___ bpm
100-110 bpm
Intrinsic HR declines ___ bpm for each decade of age
5-6 bpm
Most common cause of tachycardia in tachy-brady syndrome
AF
Formula for max HR
208- (0.7x age)
Sinus bradycardia is common in ___ and ___ MI
acute inferio and posterior
Principal tx for sinus node dysfunction
Permanent pacemaker
Class I indication for pacing in SA node dysfunction (3)
documented symptomatic bradycardia, SND associated long term drug therapy for which there is no alternative and symptomatic chronotropic incompetence
Normal automaticity rate of AV node
20-60 bpm
Channels responsible for phase 0
ICa-L (L type Calcium channels)
Channels responsible for phase 4 (4)
If, ICa-L, ICa-T,Incx
Percent Av node artery arises from RCA
90%
Percent Av node artery arises from Lcx
10%
Grouped beating is seen in what type of AV block
Mobitz Type 1 Av block
Most common causes of acquired conduction disease accounting for 50% of av block
Fibrosis and sclerosis
Highest risk of causing iatrogenic Av block
AV and TV valve surgery
AV block transiently develops in __ % of patients
10-25%
Second degree and higher grade AV block tends to occur more often in inferior rather than anterior acute MI
High grade AV block associated with inferior wall MI is often located PROXIMAL to bundle of his in ___ % of px
90%. Temporary pacing often not required
On the other hand, high grade av block in the setting of ANTERIOR MI is typically indicative of extensive infarction , is more often DISTAL to AV node and has high mortality rate. Temporary pacing typically indicated
Most common infectious cause of AV block
Lyme disease due to Borrelia burdorferi
In patients with congenital complete heart block, exercise typically _____ HR
increases
By contrast those with ACQUIRED particularly with wide QRS do not respond to exercise with an increased HR
Time from the most rapid deflection of the atrial electrogram in the his bundle to the His electrogram
AH interval
Normal AH interval
< 130 ms
Time from His electrogram to the earliet onset of QRS
HV interval
Normal HV interval
<= 55 ms
First line strategies for management of AV block
Eliminate reversible causes and determine the imediate safety and reliability of the heart rhythm
the lower the conduction system that an escape rhythm is occurring, the lower is the reliability of the escape rhythm
Permanent pacing is recommended regardless of ssx for which subset of patients with AV node dse?
ACQUIRED Mobitz type II, high grade AV block or 3rd degree av block that is NOT reversible/ physiologic
Only instance where in it is a Class I recommendation to do permanent pacing in a patient with Mobitz Type 1
If it is associated with neuromuscular disease associated with progressive conduction tissue disorder