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A jump in the atrioventricular conduction curve is not caused by a switch from fast pathway to slow pathway
Youhua Zhang1,2
1Departments of Cardiovascular Medicine and Molecular Cardiology, The Cleveland Clinic, Cleveland, OH, United States.
Insights
A jump in the atrioventricular (AV) conduction curve does not indicate a fast pathway to slow pathway (FP-SP) switch. Instead, AV conduction jumps are likely caused by intranodal/nodal-atrial reentry, challenging current electrophysiology criteria.
Area of Science:
- Electrophysiology
- Cardiovascular Research
Background:
- The clinical criterion for dual-pathway electrophysiology relies on a jump in the atrioventricular (AV) conduction curve.
- The assumption that this jump signifies a fast pathway (FP) to slow pathway (SP) conduction switch is unconfirmed.
Purpose of the Study:
- To investigate if an AV conduction jump indicates an FP to SP conduction transition.
- To identify the underlying cause of AV conduction jumps if not an FP-SP switch.
Main Methods:
- Analysis of 81 rabbit AV nodal preparations with AV conduction curves and His electrogram alternans.
- Inclusion of intracellular action potential recordings from AV nodal fibers in most cases.
Main Results:
- 13% of preparations (11/81) exhibited a jump in the AV conduction curve.
- Jumps occurred after FP-SP transition, but were associated with intranodal/nodal-atrial reentry.
- The beat with a jump showed SP-FP or SP-SP patterns, not a simple FP-SP transition.
Conclusions:
- A transition from FP to SP conduction does not cause a jump in the AV conduction curve.
- AV conduction jumps are most likely caused by intranodal/nodal-atrial reentry and its subsequent conduction.
Abstract:
Background: A jump in the atrioventricular (AV) conduction curve is the current clinical criterion of dual-pathway electrophysiology. However, the assumption that a jump indicates a switch from fast pathway (FP) to slow pathway (SP) conduction remains unconfirmed. This study was carried out to investigate whether a jump indeed indicates a transition from FP to SP conduction, and if not, what the potential cause is. Methods: Eighty-one experimental records from rabbit AV nodal preparations containing the following data were analyzed: 1) had at least one AV conduction curve and 2) had recording of His electrogram alternans (a validated new index of dual-pathway conduction). Most cases also had intracellular action potential recordings from the AV nodal fibers. Results: Of the 81 preparations, 11 (13%) showed a jump in the AV conduction curve. The jumps always occurred after the FP to SP transition. The FP-SP transition occurred at prematurity at 196 ± 39 ms versus the jump at 114 ± 13 ms (p < 0.001). The beat with a jump showed an SP-FP pattern in seven and an SP-SP pattern in four preparations. The jumps were always associated with and most likely caused by the formation of intranodal/nodal-atrial reentry and its subsequent conduction, rather than a switch from FP to SP conduction. Conclusion: Contrary to what has been assumed, a transition from FP to SP conduction does not produce a jump in the AV conduction curve. A jump in the AV conduction curve is most likely caused by the formation of intranodal/nodal-atrial reentry and its subsequent conduction.
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