Figure 1. Flow chart depicting patient selection methodology.
The control cohort for this study was identified differently. The
control group included consecutive patients identified with the
following characteristics: a
CHA2DS2-VASc score of 3 or more,
documentation of NVAF, underwent screening TEE before Watchman LAA
closure device (Boston Scientific Corporation, St Paul MN) placement
from January 1, 2015, to December 31, 2019, and absence of LAA thrombus
on screening TEE. A total of 74 subjects were thus identified and
included in the control cohort. The control group was selected based on
prior Watchman screening for their elevated risk for LAA thrombus based
on an elevated CHA2DS2-VASc score, the
presence of prior TEE imaging, confirmed absence of LAA thrombus on TEE,
and prior confirmed history of AF. Additional subjects were added to the
control cohort with the following characteristics: CHA2DS2-VASc score of
3 or more, documentation of NVAF, underwent TEE prior to cardioversion
from February to October 2014, and absence of LAA thrombus on TEE. A
total of 43 subjects were thus identified and included in the control
cohort resulting in 117 total subjects (Figure 1). For all 117 control
subjects, imaging permitted orthogonal measurements of the LAA ostial
diameters. Primary TEE imaging and electronic medical record data were
confirmed by two study cardiologists (MB and AW).
Transesophageal echocardiography and measurement of clinical
parameters .
2D multiplane TEE was performed and interpreted by experienced
cardiologists using an EPIQ ultrasound system and X8-2t probe (Philips
Medical Systems, Andover, MA). Studies were performed according to the
American Society of Echocardiography guidelines. LAA peak exit
velocities were measured approximately 1 cm below the outlet of the LAA
cavity using pulse wave Doppler ultrasound in the 45° view. Peak exit
velocities were measured as the average of three consecutive cardiac
cycles in patients with normal sinus rhythm and five consecutive cardiac
cycles in patients with AF at the time of examination. The LAA imaging
was obtained at end-diastole when the LAA diameter and volume was
maximal; and was evaluated in four different mid-esophageal planes: 0°,
45°, 90°, and 135°. In each of the four planes, LAA ostial diameters
were measured from the inferior portion of the ostium at the level of
the circumflex coronary artery up to the point 2 cm from the tip of the
left superior pulmonary vein limbus. In each plane, LAA depth was
measured from the ostial line orthogonal to the LAA neck axis to the LAA
apex. Given the retrospective nature of the study, measurements at all
four mid-esophageal planes were not uniformly available. All TEE studies
were independently reviewed by two cardiologists. The final LAA ostial
diameter and length measurements were derived from an average of the
echocardiographers’ measurements. The orifice area was calculated using
two orthogonal measured ostial radiuses (a ) and (b ) using
the formula πab . Orthogonal LAA radiuses were measured at TEE
planes 0° and 90°, as well as 45°and 135°, provided all four planes were
available for review. Aggregate OA was calculated as the average of the
measured OAs for the subjects where all four mid-esophageal planes were
available (0° and 90°, as well as 45°and 135°). In the case that only
one pair of orthogonal measurements (0° and 90° or 45°and 135°) was
available then this value alone was used in the calculation of aggregate
OA. Similarly, regarding OA at the largest diameter, when all four
mid-esophageal planes were available (0° and 90°, as well as 45°and
135°) the largest diameter and its orthogonal plane was selected. 42 of
the 61 subjects in the thrombus group and 48 of the 61 subjects in the
control group had all four mid-esophageal planes available. LAA thrombus
was identified as independently mobile echo-densities that corresponded
with contrast echocardiography filling defects.
Chart review was completed for each patient to determine anticoagulation
status, underlying rhythm, and
CHA2DS2-VASc score all at the time
of TEE. Medical history was also reviewed for ischemic stroke or TIA
history.