Discussion
Acute pericardial effusion and tamponade during deployment is a recognized though uncommon complication of LAAC. The incidence of pericardial effusion in both the EWOLUTION registry and the Boston Scientific manufacturer-compiled registry is less than 1%, significantly lower than reported in the original trials (3,4). Delayed pericardial effusion after LAAC is even less common (5). Regardless of timing, such effusions can lead to cardiac tamponade and even death. Avoidance and recognition of procedurally-related pericardial effusion are imperative to the LAAC operator.
As far as we know, this is the first case series to report delayed pericardial effusion following LAAC with WATCHMAN FLX™. The mechanism in both of these cases was likely microperforation during implantation. One plausible explanation would be that the J-shaped fixation anchors of the WATCHMAN FLX™ device caused appendage microperforations during the procedure, an etiology that has been theorized in the PINNACLE FLX trial (2). In both cases presented, the patient was in sinus rhythm at the time of the procedure and noted to have a hyperdynamic left atrial appendage on contrast injection. We hypothesize that this hyperdynamic state may have caused increased anchor tissue engagement leading to appendage microperforation.
The appearance of “auto-tug”—where the core wire moves automatically back and forth within a loosened hemostatic valve—is not an uncommon finding noted prior to WATCHMAN™ release. Tightening the hemostatic valve on the core wire in this situation may put strain upon the appendage, especially in the setting of a hypermobile or hyperdynamic appendage, causing the anchors to repeatedly pull upon appendage tissue. Therefore, we recommend loosening the hemostatic valve from the core wire, allowing the core wire to move freely in these situations until device release. When the “tug test” is performed, it should be performed very gently. Though the exact mechanism of microperforation is not well understood, attention to the interaction of the WATCHMAN™ device, delivery system, and the appendage may help to reduce the chance of inadvertent appendage perforation.