Abstract
Background: Sole pulmonary vein (PV) isolation by ablation therapy prevents atrial fibrillation (AF) in patients with short episodes of AF and without comorbidities. Since incomplete PV isolation can be curative, we tested the hypothesis that the PV in the absence of remodeling and comorbidities contains structural and functional properties that are proarrhythmic for AF initiation by reentry.Methods: We performed percutaneous transvenous in vivo endocardial electrophysiological studies and quantitative histological analysis of PV from healthy sheep.Results: The proximal PV contained more myocytes than the distal PV and a higher percentage of collagen and fat tissue relative to myocytes than the left atrium. Local fractionated electrograms occurred in both the distal and proximal PVs, but a large local activation (>0.75 mV) was more often present in the proximal PV than in the distal PV (86 vs. 50% of electrograms, respectively, p = 0.017). Atrial arrhythmias (run of premature atrial complexes) occurred more often following the premature stimulation in the proximal PV than in the distal PV (p = 0.004). The diastolic stimulation threshold was higher in the proximal PV than in the distal PV (0.7 [0.3] vs. 0.4 [0.2] mA, (median [interquartile range]), p = 0.004). The refractory period was shorter in the proximal PV than in the distal PV (170 [50] vs. 248 [52] ms, p < 0.001). A linear relation existed between the gradient in refractoriness (distal-proximal) and atrial arrhythmia inducibility in the proximal PV.Conclusion: The structural and functional properties of the native atrial-PV junction differ from those of the distal PV. Atrial arrhythmias in the absence of arrhythmia-induced remodeling are caused by reentry in the atrial-PV junction. Ablative treatment of early paroxysmal AF, rather than complete isolation of focal arrhythmia, may be limited to inhibition of reentry.
Highlights
Atrial fibrillation (AF) is a common cardiac arrhythmia in humans, which decreases the quality of life and increases the risk of ischemic stroke and heart failure (Jenkins and Bubien, 1996; Kannel and Benjamin, 2009)
We evaluated the morphology of the local electrograms in the distal and proximal pulmonary vein (PV) during sinus rhythm to investigate a correlation with the histological findings
Local fractionated electrograms (LFE)+B was more often observed in the proximal PV than in the distal PV (86 and 50% of total electrograms in the proximal PV (n = 28) and the distal PV (n = 28), respectively, p = 0.017)
Summary
Atrial fibrillation (AF) is a common cardiac arrhythmia in humans, which decreases the quality of life and increases the risk of ischemic stroke and heart failure (Jenkins and Bubien, 1996; Kannel and Benjamin, 2009). Since a focal mechanism for PV ectopy is often suggested, drug-resistant paroxysmal AF (duration of AF episode < 1 week) has been treated with ablative therapy using “spot-on” targeted PV ablation (Haissaguerre et al, 1998) or complete PV isolation (PVI) lesions (Pappone et al, 1999). The highest success rate of sole PVI exists in patients with short episodes of AF (paroxysmal AF), with low extent of structural fibrotic AF remodeling, and without comorbidities (Themistoclakis et al, 2008; Marrouche et al, 2014; Kis et al, 2017). Sole pulmonary vein (PV) isolation by ablation therapy prevents atrial fibrillation (AF) in patients with short episodes of AF and without comorbidities. Since incomplete PV isolation can be curative, we tested the hypothesis that the PV in the absence of remodeling and comorbidities contains structural and functional properties that are proarrhythmic for AF initiation by reentry
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