Bradycardia assessment
Bradycardia basics
Purpose
Rarely performed in the current times.
Previously performed for patients with unexplained syncope.
May be utilised if any suspicion of damage to sinus or AV node during an EP procedure.
Sinus node assessment
Equipment
1 venous sheath
Requires a minimum of 1 high right atrial catheter (JSN)
Sinus node recovery time (SNRT) procedure
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Burst pacing at a set rate for 30 seconds is performed at different rates (600ms, 500ms and 400ms)
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The PPI on the HRA catheter is measured immediately after pacing termination.
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A normal SNRT response is <1600ms.
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A corrected SNRT (cSNRT) can be calculated to account for differences in basic cycle length
-cSNRT = SNRT - BCL
-a normal cSNRT is <525ms
Sinoatrial conduction time (SACT) procedure
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Vary rarely used
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An estimate of time needed from the sinus activation to the atrial tissue
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If prolonged suggests a degree of sinus exit block
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Can be measured with a burst of atrial pacing (Narula method) or with a single APB- sensed APB - S2 (Strauss method)
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Strauss method: (S2-PPI) - ACL /2
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Normal SACT <120ms
AV node assessment
Equipment
1 venous sheath
Requires a minimum of 1 JSN catheter to measure HIS region signals (AH, HV)
AV wenckebach thresholds can be checked and may be compared to pre ablation numbers if there is suspicion of damage to the AVN
Measurements
Normal AH interval: 55-140ms
Normal HV interval 35-60ms