Our Team in Zurich – Vein Specialists & Doctors

The Team in Zurich

Dr. Johann C. Ragg, MD | Chief Physician more Info

I am both a physicist and a physician. I have been involved in the development of lasers and their applications since 1981. My specialty is diagnostic radiology, where I have focused on imaging techniques such as ultrasound. Having performed more than 250,000 ultrasound examinations of blood vessels, I find it easy to make accurate diagnoses. This allows me to give you sound advice.

Since 1990, I have focused exclusively on interventional vascular medicine . This involves using miniature instruments to treat veins and arteries without major surgery. I have performed more than 100,000 successful catheter interventions, giving me extensive experience and a basis for developing new methods.

I developed the angioclinic® vein therapy in Switzerland with the support of Swiss angioclinic® AG and Swiss VX GmbH, and it is specifically tailored to the needs of the Swiss population. . I have been living and working in Switzerland since 2009, but I also treat patients in Munich and Berlin.

My memberships in medical associations, in addition to the Swiss Society of Phlebology (SGP) and the Union of Swiss Societies for Vascular Diseases (USGG), can be found at www.venenragg.de

My scientific activities are accessible to professionals at www.venartis.org.

Dr. Sebastian Kreis, MD | Attending Physician Zurich

Dr. Sebastian Kreis, MD, is a General Practitioner FMH and a specialist in General Medicine (D) with a doctorate in Phlebology. He has collaborated scientifically with Dr. Ragg for many years and is an Attending Physician at the angioclinic® Vein Center Zurich.

Dr. Kreis holds DEGUM Level I certification for ultrasound diagnostics in the fields of Internal Medicine and General Medicine.
Previously, Dr. Kreis worked for five years at the Center da sandà Val Müstair (CSVM) in Graubünden, most recently as a Senior Physician.

Simon Grzelachowski | Phlebology Assistant

Simon Grzelachowski, whom most patients simply call “Mr. Simon,” has been working alongside Dr. Ragg for 18 years now. During this time, in addition to general venous medicine, he has gained in-depth knowledge of all the specialized phlebological procedures developed by Dr. Ragg and has been actively involved in all research projects.
Building on his initial training as a medical assistant, he completed advanced training in Germany to become a phlebology assistant (at the Training Academy of the German Society for Phlebology and Lymphology). In daily practice, he assists with the preparation and administration of medical and aesthetic therapies.
Thanks to his exceptional knowledge and skills, he supports our practices as a trainer for medical assistants and an ultrasound instructor for our physicians. In 2026, he was selected as the first partner candidate for the angioclinic® Vein Centers.

Birgit Marquardt | Member of the Management Board

Birgit Marquardt gained experience in dealing with people and managing finances at a major German bank when it was still headed by a well-known Swiss executive.
She is a founding member and co-owner of the angioclinic Group. Since 2010, she has been supporting our teams with organizational matters and personally addressing the specific concerns and requests of our patients.