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Characterization of the excitable gap in human type I atrial flutter
D J Callans1, D Schwartzman, C D Gottlieb
1Philadelphia Heart Institute and the Sidney Kimmel Cardiovascular Research Center, Pennsylvania 19029, USA. callans@auhs.edu
Journal of the American College of Cardiology
|December 31, 1997
Summary
This study found a fully excitable gap in most type I atrial flutter circuits, with the isthmus being most prone to conduction delay. These findings advance understanding of atrial flutter reentrant circuits.
Area of Science:
- Electrophysiology
- Cardiology
- Cardiac Arrhythmias
Background:
- The electrophysiologic substrate of typical atrial flutter remains incompletely understood.
- The specific role and properties of the tricuspid valve isthmus within the reentrant circuit are not well-defined.
Purpose of the Study:
- To characterize the excitable gap within the reentrant circuit of typical atrial flutter.
- To investigate potential differences in electrophysiologic properties between the tricuspid valve isthmus and other parts of the circuit.
Main Methods:
- Resetting protocols were applied at two sites (proximal and distal to the isthmus) in 14 patients with type I atrial flutter.
- Analysis focused on resetting response patterns and the location of interval-dependent conduction slowing.
Main Results:
- A flat resetting response, indicating a fully excitable gap, was observed in 13 of 14 patients.
- Interval-dependent conduction delay predominantly occurred in the isthmus during the increasing portion of the resetting curve.
- Resetting responses were generally similar at both pacing sites, though significant differences in three patients suggested transient changes in conduction or circuit path.
Conclusions:
- Most cases of type I atrial flutter exhibit a fully excitable gap across the entire reentrant circuit.
- The tricuspid valve isthmus is the region most susceptible to interval-dependent conduction delay at short coupling intervals.