Transcatheter aortic valve implantation (TAVI) is recommended for treatment of high-risk aortic stenosis patients. While measuring mean transaortic valve gradient (MG) is crucial in evaluating procedural success, echocardiographic measurements often overestimate direct invasive measurements. This study aimed to examine the discordance between echocardiographic and invasive MGs in TAVI patients and assess their prognostic value on long-term outcomes. This prospective registry included consecutive TAVI patients at a tertiary university hospital. Transthoracic or transoesophageal echocardiography was performed pre-TAVI, at discharge, 1 month, 1, and 5 years with invasive MG measurements obtained peri-procedurally. The primary endpoints were 5-year all-cause mortality and major adverse cardiac events. Among 1353 patients from 2011 to 2023, non-invasive MGs exceeded invasive MGs pre- and post-implantation (43 [36, 52] mmHg vs. 40 [30, 50] mmHg, p <
0.001
9 [6, 12] mmHg vs. 4 [2, 7] mmHg, p <
0.001) Pre-procedural MGs correlated better than post-procedural MGs (r = 0.70, p <
0.001 vs. r = 0.23, p <
0.001), particularly in self-expandable valves and smaller sinus of Valsalva diameter (SOVd) (r = 0.33, p <
0.001
r = 0.46, p <
0.001 vs R = 0.06, p = 0.701). Non-invasive MG remained stable from discharge (9 [6, 12] mmHg) to 5 years (9 [7, 12] mmHg). While structural valve deterioration and patient-prosthesis mismatch showed no impact, extreme invasive MGs (<
3 or >
6 mmHg) predicted worse outcomes (mortality hazard: 1.25 [1.06, 1.88] and 0.85 [0.8, 0.95], respectively), unlike non-invasive measurements. In conclusion, invasive as compared with non-invasive MGs correlated better before than after valve implantation, whereas invasive MGs were always lower than non-invasive MGs. Lower invasive MGs after TAVI appeared to be associated with favourable long-term outcomes.