ABSTRACTIntroduction: The utility of routine balloon predilation in transcatheter aortic valve replacement (TAVR) with self-expanding valves is not established. Clinical outcomes at 30 days and 1 year post TAVR, deploying the ?no balloon predilation? strategy have not been systematically described.Methods: Between October 2011 and September 2016, all patients who underwent TAVR with self-expanding valves (CoreValve?, Medtronic, Inc., Minneapolis, MN, USA) were stratified into predilation and no predilation groups. Of the 564 patients in the study, predilation was performed in 410 (72.7%) patients.Results: The need for postdilation was less when predilation was performed (30.2%), compared with no predilation (39.0%; adjusted odds ratio [aOR]:0.741, 95% confidence interval [CI]: 0.493?1.114). ?Clinically significant? paravalvular leak (PVL) was similar in the predilation (5.9%) and no predilation (6.8%) groups (aOR: 0.886, 95% CI: 0.398?1.971). Permanent pacemaker implantation was higher following predilation (25.1%), compared with no predilation (15.6%; aOR:3.086, 95% CI:1.413?6.738). There were no differences in 30-day myocardial infarction, or 30-day and 1-year stroke and death. When patients undergoing predilation were further stratified into conservative predilation (predilation balloon size ≤ minimum annulus diameter) and aggressive predilation (predilation balloon size > minimum annulus) groups, need for postdilation was lowest with aggressive predilation. PVL, 30-day and 1-year stroke rates were similar in the aggressive, conservative and no predilation groups.Conclusion: Balloon predilation in TAVR with a self-expanding prosthesis was associated with a significant decrease in the need for balloon postdilation, and a significant increase in the need for a permanent pacemaker. There was no difference in PVL, and 30-day and 1-year stroke and death rates between the two groups.