Abstract Aims A new staging classification of aortic stenosis (AS) characterizing the extent of cardiac damage was established and validated in patients undergoing transcatheter aortic valve implantation (TAVI). We aimed to validate an updated classification system in patients undergoing TAVI. Methods and results In a prospective TAVI registry, AS patients were categorized into the following stages: no cardiac damage (Stage 0), left ventricular damage (Stage 1), left atrial or mitral valve damage (Stage 2), pulmonary vasculature or tricuspid valve damage (Stage 3), or right ventricular (RV) damage or low-flow state (Stage 4). Stage 3 was sub-divided into Stage 3a (≤moderate pulmonary hypertension) and Stage 3b (severe pulmonary hypertension). Stage 4 was sub-divided into Stage 4a (low-flow without RV dysfunction), Stage 4b (RV dysfunction without low-flow), and Stage 4c (RV dysfunction with low-flow). The primary endpoint was all-cause death at 1 year. Among 1156 eligible patients, 14 were classified as Stage 0, 38 as Stage 1, 105 as Stage 2278 as Stage 3, and 721 as Stage 4. There was a stepwise increase in mortality according to advancing stages of cardiac damage: 3.9% (Stage 0–1), 9.6% (Stage 2), 14.1% (Stage 3), and 17.4% (Stage 4) (P = 0.002). After multivariable adjustment, only Stage 3b, Stage 4b, and Stage 4c conferred a significantly increased risk of mortality compared to Stage 0–1. Conclusion More than one-third of patients had advanced cardiac damage (severe pulmonary hypertension or RV dysfunction) before TAVI, associating with a five- to seven-fold increased risk of mortality at 1 year. Clinical trial registration https://www.clinicaltrials.gov. NCT01368250.