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Our Providers

Continuous Care

Dr. Priyantha Ranaweera

Interventional Cardiologist





Caring for patients in the Manhattan area since 2007, he created Manhattan Medical Group in 2018 to provide an integrated care model with primary care and specialized care.

Under his leadership, Manhattan Medical Group is dedicated to the long-term success of patients’ health and the community.

Priyantha Ranaweera, MD, MHCM, FRACP, FACC, is a Harvard-trained interventional cardiologist. He started Heart and Vascular Clinics in 2012 to better serve the needs of the Flint Hills region.

Dr. Ranaweera completed his undergraduate work in Sri Lanka and an internal medicine residency in New Zealand and Australia. He continued his education with the following training:

  • Coronary angioscopy training in Japan

  • Coronary CT fellowship in Germany

  • Cardiology fellowship in Australia

  • Peripheral interventional fellowship at Harvard Medical School

  • Coronary interventional fellowship at Harvard Medical School

  • Master of science in healthcare leadership from Harvard University

Dr. Priyantha Ranaweera, Interventional Cardiologist

Dr. Ranaweera diagnoses and treats patients with peripheral artery disease, coronary artery disease, and arrhythmias among other cardiovascular diseases. He specializes in peripheral interventions, heart catheterizations, pacemaker and ICD implants, and general cardiology.


Dr. Ranaweera sees patients at our Manhattan, Junction City, Wamego, Abilene, Clay Center, and Council Grove clinic locations.

Dr. Robert Callahan


Robert Callahan, D.O., graduated from Santa Clara University, where he double majored in mathematics and combined sciences (a pre-med major). He also double minored in biology and chemistry. After completing his degree at Santa Clara University, Dr. Callahan earned his graduate degree from Touro University Nevada – School of Osteopathic Medicine. Dr. Callahan is board certified through the American Board of Family Medicine. He joined the Primary Care Team at Manhattan Medical Group in July of 2021.

Dr. Callahan was born in Glendale, California, and dreamt of becoming a police officer before falling in love with medicine. He is an avid fan of Olympic weightlifting and was a Division 1 water polo college athlete. Dr. Callahan is also one of the biggest Star Wars nerds in the Little Apple!

He met his wife in college, and they have two children: Liam and Isabella. They also have two pet dogs, Luna and Ava, and two cats, Winston and Lucy.

His care philosophy is creating a more holistic approach to the patient, focusing on educating and assisting patients in making well-informed choices. His patients keep him passionate about his work as a health care provider.

As a doctor who’s always looking out for his patients, Dr. Callahan’s favorite advice to patients is “BE KIND TO YOURSELF.”

Dr. Callahan Headshot.jpeg

Larry Pierce 

Physician Assistant

Larry Pierce Jr., PA-C, joined Manhattan Medical Group in March 2021 after serving 21 years in the United States Army. Larry has over ten years of experience in family medicine. He was awarded a Master’s Degree in Physician Assistant Studies from the University of Nebraska Medical Center.


Outside of work, Larry loves to hunt and is an expert at taekwondo. He currently volunteers at the Global Traditional Martial Arts (GTMA) school in Junction City, Kansas. Larry is also a big fan of the Kansas City Chiefs and the Colorado Avalanche professional hockey team.


Larry lives with his wife, Kathryn, and their four children in the local area. His family includes three dogs named Lacey, Link, and Coco. 


Last but not least, his advice to his patients is that we must enjoy life to the fullest as we have only one! 

PA-C Larry Pierce

Becca Haugaard

Nurse Practitioner

Becca Haugaard, APRN-FNP is certified in both wound care and foot care. Becca leads our Wound Care Clinic.


She specializes in;

  • Compression therapy

  • Sharps debridement

  • Adjunct therapy including human skin equivalents and wound vac.

She is also certified to do routine foot care and can provide diabetic foot checks and diabetic foot care.

Together with our vascular specialists, she also provides surgical debridement of non-healing wounds.

APRN-FNP Becca Haugaard

Abby Suddarth

Physician Assistant

Abby Suddarth, PA-C, is a certified Physician Assistant who is excited to offer virtual telehealth appointments.

She graduated from the Butler University Physician Assistant Program with a bachelor’s degree in health sciences. She initially joined Dr. Ranaweera at Mercy Regional in the fall of 2007 when her husband was stationed at Fort Riley. She has also worked in Internal Medicine and Soldier Readiness Processing.

She enjoys spending time with her family, homeschooling their three girls, practicing her photography skills, reading, and exercising.

Physician Assistant Abby Suddarth

Tyson Nickelson

Nurse Practitioner

Tyson Nickelson, MSN, FNP-C is an advanced practice nursing provider with extensive experience in healthcare, particularly in the care of cardiac patients and in the Intensive Care Unit.

He specializes in:

  • Cardiology

  • Diseases affecting veins

Tyson Nickelson, MSN, FNP-C

Hollie Hall

Nurse Practitioner

Hollie Hall, NP-C, specializes in cardiology and diseases affecting veins.

She specializes in:

  • Radio-frequency ablations

  • Sclerotherapy

She graduated from Baker University with a degree in nursing and received a master's degree from the University of Phoenix.

She began her career in the cardiology department of Via Christi Hospital in 2011. She joined Heart and Vascular Clinics in 2016.

She is married to former NFL and Kansas State football alum Joe Hall. They have 4 children: Joe, Jorryn, Joss, and Jagger. She enjoys spending time with her family and can be found cheering at her children's sporting events.

NP-C Hollie Hall

Joshua Wichman

Nurse Practitioner

Joshua Wichman, NP-C, is an advanced practice provider that specializes in cardiology and disease affecting the veins. 

He joined Manhattan Medical Group in 2021. Josh is currently accepting new patients at our cardiology practice.

Nurse Practitioner Joshua Wichman
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