P5432Invasive assessment by atrial volume-pressure loops of the acute changes in left atrial function induced by pulmonary vein antral isolation
Authors: Karanasos A , Toutouzas K , Tsiachris D , Kordalis A , Tyrovolas K , Efremidis M , Karmpalioti M , Aggeli C , Karagiannis S , Prappa E , Stefanadis C , Gatzoulis K , Tousoulis D 
Published: October 2019

Abstract

Background
Atrial volume-pressure loops are considered the best method to assess left atrium (LA) function. Changes in atrial function induced by pulmonary vein (PV) antral isolation of atrial fibrillation (AF) have not been documented thus far using this approach.

Purpose
We aimed to evaluate changes in LA function in patients with paroxysmal atrial fibrillation (PAF) undergoing catheter ablation by atrial volume-pressure loops.

Methods
Patients undergoing for the first time catheter ablation of PAF by PV antral isolation and PV-LA junction ablation, as clinically indicated, were enrolled from 2 centers. Each center enrolled consecutive patients undergoing PV antral isolation using the same method i.e. radiofrequency or cryoballoon ablation. Patients with severe mitral stenosis or regurgitation, any prosthetic valve, left atrial thrombus or severe systolic or diastolic dysfunction of the left ventricle were excluded. Before and after the procedure, all patients underwent real-time three-dimensional transthoracic echocardiogram to evaluate volume changes of the LA during an entire cardiac cycle, while simultaneously recording LA pressure by a 6F angiographic catheter following transseptal puncture. After the procedure, LA volume and pressure recordings were gated offline by ECG, and were used to plot the LA pressure as a function of LA volume, thus creating a volume-pressure loop. The A loop area is a measure of the booster pump function of the LA. The V loop area expresses the reservoir function of the LA. Pressure and volume data at the clockwise ascending limb of the volume-pressure loop were fitted to the exponential function P = bxea·V, where P = instantaneous LA pressure; V = LA volume; a is the passive elastic chamber stiffness constant (cm–3) that determines the slope of the exponential curve, and b is the elastic constant (mm Hg).

Results
34 patients with PAF were analysed, 12 treated with radiofrequency ablation and 22 with cryoablation. The procedure was uneventful in all cases. Mean LA pressure, A-wave amplitude, and V-wave amplitude were all significantly increased post-procedurally (p<0.001 for all). The area of the A-loop decreased (Post: 40.69 ml·mm Hg [IQR 13.7–71.3] vs. Pre: 64.2 ml·mm Hg [IQR 30.9–86.9]; p=0.001), whereas the area of the V-loop increased (Post: 96.5 ml·mm Hg [IQR 45.1–230.5] vs. Pre: 79.2 ml·mm Hg [IQR 46.9–149.7]; p=0.016). Although the elastic constant increased (p<0.001), there was no significant difference in the passive chamber elastic constant (p=0.30).

Conclusion
Volume-pressure loops can assess procedural changes in LA function. Catheter ablation of AF is associated with a decrease the LA booster pump function of the LA, and in increase in the left atrial reservoir function. Moreover, there is an increase in LA pressures that is observed in the absence of change in LA stiffness.