Architecture of the pulmonary veins: relevance to radiofrequency ablation

Abstract

Background-Radiofrequency ablation of tissues in pulmonary veins can eliminate paroxysmal atrial fibrillation. Objective-To explore the characteristics of normal pulmonary veins so as to provide more information relevant to radiofrequency ablation. Methods-20 structurally normal heart specimens were examined grossly. Histological sections were made from 65 pulmonary veins. Results-The longest myocardial sleeves were found in the superior veins. The sleeves were thickest at the venoatrial junction in the left superior pulmonary veins. For the superior veins, the sleeves were thickest along the inferior walls and thinnest superiorly. The sleeves were composed mainly of circularly or spirally oriented bundles of myocytes with additional bundles that were longitudinally or obliquely oriented, sometimes forming mesh-like arrangements. Fibrotic changes estimated at between 5% and 70% across three transverse sections were seen in 17 veins that were from individuals aged 30 to 72 years. Conclusions-The myocardial architecture in normal pulmonary veins is highly variable. The complex arrangement, stretch, and increase in fibrosis may produce greater non-uniform anisotropic properties. (Heart 2001;86:265-270) Keywords: arrhythmias; catheter ablation; fibrillation; cardiac veins Studies from various groups of investigators have suggested that certain forms of atrial fibrillation are related to the existence of an ectopic discharging focus which is frequently located within the pulmonary veins.1-4 Radiofrequency catheter ablation carried out in the pulmonary veins can eliminate paroxysmal atrial fibrillation in many cases. Stenosis of the vein is a recognised complication following catheter ablation.5 Recurrence of the arrhythmia is also a common problem.4 Both drawbacks of current techniques of catheter ablation in these patients may be avoidable if there is better understanding of the architecture of the pulmonary veins in the human heart.In this study, we explored the walls of the pulmonary veins from the venoatrial junction to the hilum in normal specimens. We then reconstructed our findings so as to provide a three dimensional impression of the architecture of the cardiac muscle, which reinforces to a varying extent the outer layer of the pulmonary veins at their junction with the left atrium. To standardise the orientation of the left and right pulmonary veins, and to emphasise the potential significance of the diVerences in the anatomical arrangements, we viewed the orifices of the veins as they would be seen in a simulated left anterior oblique projection, and used the clock face to describe the sectors of the walls. MethodsWe harvested 65 veins from 20 structurally normal heart specimens that were collected in

Pulmonary Vein Ostium Geometry

“…[1][2][3] Therefore, electrical isolation of these ostia by catheter ablation is presently used as a treatment modality for patients with this problem. This isolation can be achieved by discrete lesions at the rim of the ostium, guided by perimetric mapping with a multipolar loop catheter like the Lasso (Biosense Webster, Inc) or by lesions in the left atrium encircling multiple PV ostia.…”

Treatment of Paroxysmal Atrial Fibrillation by Pulmonary Vein Isolation

“…Less radiofre- quency energy is needed to isolate the right inferior pulmonary vein because there is less muscle surrounding this vein than the other pulmonary veins. 2,3 During follow-up, a repeat ablation procedure was performed in 11% of patients. Among the 176 patients with paroxysmal AF, the proportion who were free of recurrent AF in the absence of antiarrhythmic drug therapy was 72% at 12 months, and 70% at 24 months.…”

“…2,3 Although the underlying mechanisms are still unclear, the muscle within these sleeves may be arrhythmogenic. [4][5][6] There are at least 3 possible ways that the pulmonary veins may contribute to the generation of AF.…”

Catheter ablation of atrial fibrillation

“…Histological sections from PVs have demonstrated the high variability of myocardial architecture in the PVs. 33 The presence of gaps in the myocardial sleeves, and acquired areas of fibrosis (Fig. 3), suggests that ablation of the entire circumference of PV ostia may not be necessary and may only serve to increase the adverse effects.…”

“…It has been postulated that, with the anatomical arrangement of longitudinal fascicles, a focal lesion placed at the venoatrial junction will eliminate venous potentials detected distally. 33 Haïssaguerre et al have shown that PV isolation can be achieved by selective ablation of ostial sites where a PV potential is recorded. 34 Selective ablation of ostial sites where a PV potential is recorded provides an unambiguous endpoint and has the advantage of not requiring detailed mapping of spontaneous ectopy, as ostial PV potentials can be recorded during sinus rhythm or atrial pacing.…”