Vanderheyden, Marc, et al. “Post-Extrasystolic Potentiation Differentiates “true” from ‘pseudo’ Low-Flow, Low-Gradient Aortic Stenosis”. Journal of Cardiology and Cardiovascular Medicine, vol. 5, no. 3, Dec. 2020, pp. 172-3, doi:10.29328/journal.jccm.1001105.