Published Online
on June 6, 2008

A more recent version of this article appeared on August 1, 2008

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Original Article

The Atrial Septopulmonary Bundle of the Posterior Left Atrium Provides a Substrate for AF Initiation in a Model of Vagally Mediated Pulmonary Vein Tachycardia of the Structurally Normal Heart

Matthew Klos¹, David Calvo², Masatoshi Yamazaki³, Sharon Zlochiver³, Sergey Mironov³, José-Angel Cabrera⁴, Damian Sanchez-Quintana⁵, José Jalife³, Omer Berenfeld³ and Jérôme Kalifa^3,6

¹ SUNY Upstate Medical University, Syracuse, NY;
² Hospital Universitario Central de Asturias, Area del Corazón, Spain;
³ Center for Arrhythmia Research, University of Michigan, Ann Arbor, MI;
⁴ Universidad Europea de Madrid, Madrid, Spain;
⁵ Departamento de Anatomía Humana, UEX, Badajoz, Spain

Correspondence: ⁶ E-mail: jeromekalifa{at}gmail.com

Background—The posterior left atrium (PLA) and pulmonary veins (PVs) have been shown to be critical for atrial fibrillation (AF) initiation. However, the detailed mechanisms of reentry and AF initiation by PV impulses are poorly understood. We hypothesized that PV impulses trigger reentry and AF by undergoing wavebreaks as a result of sink-to-source mismatch at specific PV-PLA transitions along the septopulmonary bundle (SPB), where there are changes in thickness and fiber direction.

Methods and Results—In 7 Langendorff-perfused sheep hearts AF was initiated by a burst of 6 pulses (CL 80-150ms) delivered to the left inferior or right superior PV ostium 100-150 ms after the sinus impulse in the presence of 0.5 µM acetylcholine. The exposed septal-PLA endocardial area was mapped with high spatio-temporal resolution (DI-4-ANEPPS, 1000-fr/s) during AF initiation. Isochronal maps for each paced beat preceding AF onset were constructed to localize areas of conduction delay and block. Phase movies allowed the determination of the wavebreak sites at the onset of AF. Thereafter, the PLA myocardial wall thickness was quantified by echocardiography, and the fiber direction in the optical field of view was determined after peeling off the endocardium. Finally, isochrone, phase and conduction velocity maps were superimposed on the corresponding anatomical pictures for each of the 28 episodes of AF initiation. The longest delays of the paced PV impulses, as well as the first wavebreak, occurred at those boundaries along the SPB that showed sharp changes in fiber direction and the largest and most abrupt increase in myocardial thickness.

Conclusions—Waves propagating from the PVs into the PLA originating from a simulated pulmonary vein tachycardia triggered reentry and vagally mediated AF by breaking at boundaries along the SPB where abrupt changes in thickness and fiber direction resulted in sink-to-source mismatch and low safety for propagation.

Key Words: electrophysiology • mapping • reentry • atrial thickness • fiber direction

Related Article

Atrial Septopulmonary Bundle of the Posterior Left Atrium Provides a Substrate for Atrial Fibrillation Initiation in a Model of Vagally Mediated Pulmonary Vein Tachycardia of the Structurally Normal Heart

Matthew Klos, David Calvo, Masatoshi Yamazaki, Sharon Zlochiver, Sergey Mironov, José-Angel Cabrera, Damian Sanchez-Quintana, José Jalife, Omer Berenfeld, and Jérôme Kalifa
Circ Arrhythmia Electrophysiol 2008 1: 175-183. [Abstract] [Full Text] [PDF]