Background It is unclear if the WATCHMAN device (Boston Scientific, St. Paul, Minnesota) can be implanted without contrast to prevent complications in patients with advanced chronic kidney disease (CKD) or contrast allergy. Objective The efficiency and safety of WATCHMAN implantation under transesophageal echocardiography (TEE)-guidance and fluoroscopy without contrast use. Methods This was a retrospective single-center study at Albany Medical Center between June 2016 and June 2019. Consecutive procedure notes for all WATCHMAN devices implanted between June 2016 and June 2019 were screened to identify patients who did not receive contrast. Patients with incomplete information on the calculation of the 'Congestive heart failure, Hypertension, Age [>75 years], Stroke, Diabetes mellitus, Vascular disease, Age [65 to 74 years], Sex category' (CHA2DS2VASc)/'Hypertension, Abnormal renal/liver function, Stroke, Bleeding history, Labile international normalized ratio, Elderly, Drugs/alcohol' (HAS-BLED) score and reason(s) precluding safe contrast use were excluded. Efficiency was measured as i) accuracy of device size estimation based on TEE-measured left atrial appendage (LAA) dimensions were determined by the need to change the size of the device initially selected, ii) number of implantation attempts, irrespective of change in device size, iii) whether more than one device was used secondary to inaccurate initial size estimation or other procedural complexities, and iv) successful LAA seal on TEE immediately and 45-days post-implantation (peri-device leak of < 5 mm by color Doppler). Procedure-related complications, immediate and delayed (0-45 days), were recorded. Results Twelve patients received WATCHMAN without contrast. The mean age was 79.2 years, with male predominance (n=8). The mean CHA2DS2VASc and HAS-BLED scores were 5.50 (+/-1.24) and 4.08 (+/-1.08), respectively. Contrast was avoided because of a history of CKD stage IV (n=5), rapidly progressive CKD stage III (n=1), and contrast allergy (n=6). In 11 out of 12 patients, initial TEE-based device size estimation was accurate with successful implantation at 1 2 3 3