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.