Maximum diameter of LAA orifice and PDL
Imprecise assessment of LAA orifice, for example the selection of too small LAAC device size based on TEE measurement, at preoperative phase is one reason for the occurrence of PDL after the procedure. Other factors linked to PDL are also suggested[14]. LAA used to be considered to possess enough compliance to accommodate a larger size LAAC device. However, the remodeling of LA and LAA in AF patients may result in reduced compliance of LA and LAA, particularly in response to a compressible LAAC device that is deployed at relatively low radial force. Histological studies showed that the LAA specimens of AF patients existed obvious dilatation, stretching and reduction of pectinate muscle volume[15]. In addition, most patients with chronic AF will exhibit significant thickening of endocardium and deranged thickening elastic fibers extending to the epicardium[16]. All these changes will reduce the elasticity and compliance of LAA orifice, which increases the risk of postoperative PDL due to mismatch of LAAC device and LAA orifice.
The maximum diameter of LAA orifice and LAA volume are indirect evaluation indexes of LA remodeling. In this study, there were significant differences in the maximum diameter of LAA orifice (P = 0.009) and LAA volume (P = 0.006) between PDL group and no PDL group, suggesting that the remodeling and reduced compliance of LAA were related to the presence of PDL. Further, in the multivariate logistic regression analysis, the maximum diameter of LAA orifice served as the only significant indicator, which independently predicted the risk of PDL after LAAC procedure (OR, 1.31; 95% CI, 1.11-1.55; P = 0.002). The probability of postoperative PDL is 1.31 times higher with an increase of the maximum diameter of LAA orifice by 1 mm.
For those patients with larger size of LAA orifice and higher risk of PDL, the application of Watchman device may be suboptimal and relate to incomplete LAAC, since the available maximum diameter of the Watchman LAAC device is 33 mm now. Larger Watchman LAAC device is therefore warranted in the future to cover the need of these patients.