Intracardiac Intervals Flashcards
What is the normal PA interval Range
20-40msec
What is the normal AH interval
50-120 msec
What affects AH interval
Autonomic tone, drugs, pacing
What causes prolongation of the PA interval
Disease of Atrium or Drugs
What is a normal HV interval
35-55msec
What 3 signals make up the PR interval
PA + AH + HV
How is the AH interval measured?
A to HIS spike
What does the AH interval represent?
AV Node conduction time
What does the PA interval represent
Intra-atrial conduction time
How is the PA interval measured
P to A on His catheter
What does the steady lengthening of AH interval represent
Decremental conduction
Do accessory pathways decrement?
No - They’re all or nothing
‘Longest coupling interval that cannot initiate depolarisation’ - Describes……
Effective refractory period
‘Longest coupling interval that that still depolarises…. but gives slowed conduction’ - Describes……
Relative refractory period
‘Smallest possible time between two conducted impulses’ - Describes…….
Functional Refractory period
Does the effective refractory period decrease at faster rates - YES/NO
Yes - Refractory rates decrease with quicker HR’s
What is the normal effective refractory period of the Atrium
170 - 300ms
What is the effective refractory period of the AVN
230 - 430ms
What is the functional refractory period of the AVN
330ms - 500ms
What is the effective refractory period of the Ventricle
180 - 280ms
What is a normal SNRT
<1500ms
How do you calculate cSNRT
SNRT - BCL
What is a normal cSNRT
<525ms
What are the positions in a 4 wire study
HRA
HIS
CS
RVA
Where is the HRA and what does it give you
High RA / Gives you SN information and BCL
Where is the HIS and what does it give you
Straddles TV - Records A, H and V signals
Where is the CS and what does it give you
CS or AV Groove - Records LA & LV signals
Where is the RVA and what does it give you
RV Apex - Records RV signals
How do you measure BCL
A to A signal on HRA catheter
What does the HV interval represent
Time in His-Purkinje system
How do you measure the HV interval
H signal to earliest V
