Henrick Joan Jooast (Hein) Wellens, M.D., (born 13 November 1935, The Hague) is a Dutch cardiologist who is considered one of the founding fathers of the cardiology subspecialty known as clinical cardiac electrophysiology. Clinical cardiac electrophysiology enables patients with cardiac arrhythmmias to be subjected to catheter electrode mapping and stimulation studies. Paul Puech, first in Mexico and later in France; Benjamin Scherlag and Onkar Narula in the USA; and Dirk Durrer and Philippe Coumel in Europe were the field's pioneers in the 1950s and 1960s. The field's second wave of innovators used these techniques to unravel the mechanisms of tachycardia in humans and set the bases for their treatment. Among them, Hein Wellens in Europe and Kenneth Rosen, John Gallagher, and Mark Josephson in the USA had the greatest impact as researchers and teachers. Josephson is the author of the first and most successful textbook of clinical cardiac electrophysiology, now in its fourth edition.
Wellens, known among European cardiologists as "the giant of Maastricht", has for many years been associated with the University of Limburg School of Medicine in Maastricht, Netherlands. At his department of cardiology, many future clinical cardiac electrophysiologists trained from 1976 until his retirement in 2002.
As a pupil and collaborator of the late Professor Dirk Durrer in Amsterdam, Dr. Wellens was involved in the early developments in programmed electrical stimulation of the heart in patients with the Wolff-Parkinson-White syndrome. In these patients, cardiac arrhythmias it was shown for the very first time that were first shown to be possibly initiated and terminated by critically timed premature beats. In 1971, he reported on the use of programmed electrical stimulation of the heart in patients with atrial flutter, AV nodal tachycardia, and accessory atrioventricular connections. In 1972, he showed that the arrhythmia of patients with ventricular tachycardia could also reproducibly be initiated and terminated by timed premature stimuli. These investigations were the basis for the new surgical and pacing approaches to the treatment of cardiac arrhythmias that became known as "cardiac electrophysiology". to be Wellens also demonstrated that the reproducible initiation and termination of arrhythmias by programmed electrical stimulation of the heart allowed the study of the effect of antiarrhythmic drugs on the mechanism of the arrhythmia. In 1977, he moved to the new University of Limburg in Maastricht, Netherlands, to develop academic cardiology there. Starting from scratch, he created an internationally known center for the study and treatment of cardiac arrhythmias.
Dr. Wellens has published more than 600 manuscripts in peer-reviewed journals and more than 200 book chapters, and has written or edited 18 books on cardiology. More than 150 cardiologists from abroad have come to Maastricht for six months to two years for postgraduate training in cardiac electrophysiology. At present, Dr Wellens directs a large academic cardiology department with a staff of 20 cardiologists and a well-known cardiology training program. He is also an internationally known teacher and lecturer and member of many international cardiological societies. For over 30 years, he has been coaching a high-yield "How to Approach Complex Arrhythmias" course for cardiologists  and EP fellows, together with Mark Josephson.
- Josephson, Mark E. Clinical Cardiac Electrophysiology: Techniques and Interpretations, Fourth Edition. Philadelphia: Lippincott Williams Wilkins, 2008.
- Smeets, Joep L.R.M., ed. Professor Hein J.J. Wellens: 33 Years of Cardiology and Arrhythmology. Amsterdam, the Netherlands: Kluwer Academic Publishers; 2000.
- Maloney, James. "Biography of Hein J. J. Wellens." Heart Rhythm Society Online, Internet, http://www.hrsonline.org/News/ep-history/notable-figures/heinwellens.cfm, May 19, 1995.