A-Fib Physicians & Providers

John Johnkoski, MD

Dr. John A. Johnkoski has been a cardiothoracic surgeon with Aspirus Heart & Lung Surgery since 1999. Dr. Johnkoski received his medical degree from the University of Michigan Medical School. He performed a residency in General Surgery at State University of New York in Buffalo and completed his Cardiothoracic Surgery Residency in 1997 at the University of Washington Medical Center in Seattle, Washington.

Dr. Johnkoski is board certified by the American Board of Surgery and the American Board of Thoracic Surgery. Dr. Johnkoski has a particular interest in treatment of atrial fibrillation and started the Atrial Fibrillation Surgical Program at Aspirus Wausau Hospital in 2006.


Andrew Mykystey, MD                     

Dr. Andrew Mykytsey's specialties are electrophysiology and cardiology at
Aspirus Cardiology. Dr. Mykytsey received his medical degree from Ivano-Frankivsk State Medical Academy, Ivano-Frankivsk, Ukraine. He performed a residency in Internal Medicine at Advocate Illinois Masonic Medical Center, Chicago, IL and completed his Cardiovascular Medicine Fellowship at Michael Reese Hospital and Rush University Medical Center and his Cardiovascular Electrophysiology Fellowship at Rush University Medical Center in Chicago, IL.

Dr. Mykytsey holds board certifications by the American Board of Internal Medicine and in Clinical Cardiac Electrophysiology and Cardiovascular Disease.

Dr. Mykytsey enjoys spending time with his family, studying world history and culture, and skiing.

Ronnie Ortiz, MD 

Dr. Ronnie Ortiz' specialties are electrophysiology  and cardiovascular disease. 

Dr.Ortiz joined Aspirus Cardiology in 2018 and sees patients in both the Wausau and Wisconsin Rapids locations.  He recieved his Medical degree from UNIBE School of Medicine, Dominican Republic. He completed his Internal Medicine residency at Atlantic Health at Morristown Medical Center, Morristown NJ and his Cardiovascular Medicine  and Clinical Cardiac Electrophysiology fellowships at
LA State University School of Medicine in New Orleans, LA. 

When away from work, Dr. Ortiz enjoys history, traveling and spending time with his family.


Kevin Rist, MD, PhD

Dr. Kevin Rist's specialties are electrophysiology  and cardiovascular disease.
He has been with Aspirus Cardiology since 2010. Dr. Kevin Rist received his Doctor of Medicine from Dartmouth Medical School, Hanover, NH and his Doctor of Philosophy (PhD), Respiratory Physiology, Dartmouth Medical School, Hanover, NH. He performed his Cardiology Fellowship a the University of Minnesota, Minneapolis, MN and his Electrophysiology Fellowship at the University of Pittsburgh, Pittsburgh, PA.

Dr. Rist holds board certifications by the American Board of Internal Medicine and in Cardiovascular Disease and Clinical Cardiac Electrophysiology.

Dr. Rist enjoys his family's activities including playing soccer, ice hockey and track.  He participates in alpine racing, cross country skiing and hiking.



Kali S. Kann, PA-C   Physician Assistant - Cardiology  

Master of Science Physician Assistant - Massachusetts College of Pharmacy & Health Sciences, Manchester, NH







Megan Johnson, APNP  - Nurse Practitioner - Cardiology

Medical School - University of Wisconsin, Madison, WI                                                                                                                                  






Sabrina Weller, RN, BSN  - AFib Clinic Nurse

Sabrina has been a Nurse for over 10 years and most recently worked in the ACU and Cath Labs at Aspirus Wausau Hospital.  Sabrina works with both the EP Team and with Dr. Johnkoski delivering unified care for our patients dealing with atrial fibrillation.





Our providers are committed to providing thorough patient education on the latest atrial fibrillation treatment options. For information on AFib treatment or questions about your atrial fibrillation diagnosis, request a consultation at [email protected] or call the AFib Clinic at 715-843-1331.