Meet Our Leadership

Meet Our Leadership - Conroe Regional Medical Center

Standing Left to Right:
Toni Cotton - Chief Nursing Officer
Chad Christianson - Chief Operating Officer
Todd Caliva - Chief Executive Officer
Gregg Garrison - Chief Financial Officer

West Houston Medical Center, an HCA-affiliated hospital, is lead by a team of more than 1,000 employees and 500 physicians. Supporting this team is an impressive board of trustees that includes highly respected physician and community business leaders.

West Houston Medical Center's board of trustees helps evaluate the hospital's delivery of health care and helps develop new programs that ensure our patients receive the most advanced, cost-effective health care close to home.

Meet Our Board Members

Darius Wania, M.D.

Dr. Darius Wania is an Internal Medicine physician at West Houston Medical Center.

Dr. Wania was born in Karachi, Pakistan and received his medical degree from Dow Medical College in 1988. After completing his internships in General Surgery and Internal medicine, Dr. Wania served as Resident Medical Officer at Ziauddin Hospital in Karachi.  In 1992, Dr. Wania moved to Houston for an externship at Texas Children's Hospital followed by a residency at Cook County Hospital in Chicago, Illinois. Since 1995, Dr. Wania has provided his skills and expertise to the West Houston community at his Alief Medical Clinic. Dr. Wania is a Diplomate of the American Board of Internal Medicine and his practice philosophy is to provide direct personal patient care with an emphasis on preventative medicine.

Dr. Wania's achievements include being elected Chief of Staff at West Houston Medical Center in 2007, Chairman of Medicine at West Houston Medical Center in 2005, member in the Medical Advisory Committee for Amerigroup Insurance Company and member in the Peer Review Committee. Dr. Wania is also a member of the American Medical Association, the Texas Medical Association and the St. Lukes Hospital Independent Practice Association.

H.D. Chambers, Vice Chair


H.D. Chambers has devoted more than 25 years to public education in Texas. Prior to taking on a leadership role as superintendent of schools for Alief ISD in the spring of 2011, H.D. served as superintendent for Stafford Municipal School District.

H.D. began his career in education at Aldine ISD as a teacher and coach. He then served 14 years at Cypress-Fairbanks ISD in campus and central administration before joining Stafford in 2006.

H.D. holds leadership positions in the following:

  • Texas Association of Suburban/Mid-Urban Schools (TAS/MUS) – President International Management District – Board Member
  • Texas School Alliance – Board Member
  • Texas Select Committee on Student Performance and Accountability – Member Houston West Chamber of Commerce Governmental Affairs Committee – Member Houston Westchase Rotary Club – Member

Irma, Sanchez


Irma Sanchez is the vice president of projects for the Westchase District. Her current responsibilities include Image and Beautification, Mobility, and Long-range planning.

Irma is a member of Land Institute, West Houston Association, Scenic Houston, and Houston Galveston Area Council Ped-Bike Committee. She serves as board secretary for Houston West Chamber of Commerce, and on the board of directors for WHMC.

Houston has always been Irma’s home. She graduated from the University of Houston with a Bachelor degree in Liberal Arts. Irma, her husband and their daughter reside in northwest Houston, where they are active members of Willowbrook Christian Church.


Josier Nisnisan, M.D., Chief of Staff

Dr. Nisnisan is an Internal Medicine physician and Chief of Staff at West Houston Medical Center.

Dr. Nisnisan is a Diplomate of the American Board of Internal Medicine and has been practicing in Texas since 2004. He completed his undergraduate degree from the University of Santo Tomas in the Republic of Philippines. After receiving his license in Medicine and Surgery from Perpetual Help College of Medicine and Surgery, he completed his residency at Seton Hall University, Graduate Medical Education Program, at St. Michaele’s Medical Center in Newark, New Jersey.

Dr. Nisnisan started his Royal Oaks Medical Home and Wellness practice in 2002 in West Houston with the practice philosphy of, healing is an art, caring is a virture.  Dr. Josier Nisnisan is also a hospitalist and is credentialed at various locations in the Houston and Sugar Land areas.

In 2009, Dr. Nisnisan was awarded one of America's Top Physicians by Consumer Research Council of America. He is also a Past President of the Texas Association of Filipino Physicians and a member of the Texas Medical Association and Harris County Medical Society.

Magdy Rizk, M.D.


Dr. Magdy Rizk is an OB-GYN at West Houston Medical Center.

Dr. Rizk was born in Cairo, Egypt and received his medical degree from Cairo University, Faculty of Medicine in 1966. After completing his residency in Albany, NY, he practiced in various British hospitals throughout London. In 1991, Dr. Rizk brought his skill and expertise to the west Houston community and has been serving in the area ever since. His practice philosophy is to provide the best and latest medical care in the most compassionate and friendly atmosphere.

Dr. Rizk is a member of the American Congress of Obstetricians and Gynecologists, Royal College of OB/GYN London, England; Texas Medical Association and the American Fertility Society.

Maura Walsh, President, HCA Gulf Coast Division


As president of HCA Gulf Coast Division, Maura Walsh is committed to continuing HCA’s legacy of excellent and compassionate care. She began her healthcare career in 1980, holding executive roles at hospitals in Vermont, Arkansas, and Texas. She joined HCA in 1987, eventually serving as CEO for three different hospitals within the division. Today, she serves as the division’s president.

Maura has actively served as a board member for a number of local organizations, including the Greater Houston Partnership, the American Diabetes Association – Houston, and the American Heart Association – Houston. She is a Fellow of the American College of Healthcare Executives.

Under Maura's guidance, the division has grown to 12 hospitals, nine ambulatory surgery centers, five freestanding emergency centers and a regional transfer center that provides one-phone-call access and support for patient transfers into and out of HCA Gulf Coast Division affiliated hospitals.

Maura has a Bachelor degree from the University of Massachusetts and a Master degree from the University of Houston – Clear Lake. In 2010, UH-Clear Lake honored Maura with a Distinguished Alumni Award.

Neal Grossman, M.D.

Dr. Neal Grossman is a pediatrician at West Houston Medical Center.

Dr. Grossman was born in New York and raised in Miami. He earned a Bachelor degree from Emory University in Atlanta with Phi Beta Kappa honors. He received his medical degree from the School of Medicine at University of Miami.

Dr. Grossman completed his pediatric residency at Texas Children's Hospital in Houston. He has been in private practice in the west Houston area since 1977, most recently with Texas Children's Pediatric Associates. He has been an active member of West Houston Medical Center since its opening in 1985.

Dr. Grossman is board certified in pediatrics. He is a member of the Harris County Medical Society, the American Academy of Pediatrics and the Houston Pediatric Society.

Dr. Grossman is married with three children, one stepdaughter and three grandchildren. He loves to travel, scuba dive and ski.

Peter Curtis, M.D.

Dr. Peter Curtis is a general and vascular surgeon at West Houston Medical Center.

He is past Chief of Staff, past Chief of Surgery, past Chair of the Board of Trustees, and past Medical Director of ICU. He has also served as physician advisor for WHMC.

Dr. Curtis is a graduate of the University of Bristol in England. He is a member of the Texas Medical Association, Harris County Medical Society, Royal College of Surgeons of England, Singleton Surgical Society, and Southern Medical Association.



Rita Makhlouf, M. D., Chair


Dr. Rita Makhlouf is a neonatologist at West Houston Medical Center.

Born in Lebanon, Dr. Makhlouf earned her Bachelor degree and medical degree from the American University of Beirut. After relocating to North Carolina, she received specialty training in Neonatal-Perinatal Medicine at the University of North Carolina at Chapel Hill. She is board certified in Pediatrics and Neonatal-Perinatal Medicine.

Dr. Makhlouf is married to Dr. Fahim Farhat and they live with their two children in the west Houston area.



Sandie, Mullins


Sandie Mullins sits on the board of trustees for Houston Community College District VI.

She received her Master of Business Administration at St. Mary's University and was elected president of the Graduate Business Student Association.

Sandie has served as coordinator for Super Neighborhood 17, and co-chaired the Business and Education committee and the West Houston Public Safety committee at the Houston West Chamber of Commerce. She is currently a member of the chamber's Governmental Affairs, Economic, and Teacher of the Year committees.

Sandie regularly volunteers for the March of Dimes Walk America, American Heart Association, American Red Cross, Humana and Texas Children's Hospitals, the Collaborative for Children, West Houston Leadership Institute, and Grace Presbyterian Church.

Sandie is married and has six children.

Sol Hamburg, M.D.

Dr. Sol Hamburg is an ophthalmologist at West Houston Medical Center.

Dr. Hamburg is a graduate of City College of New York with a Bachelor degree in mathematics. He attended medical school at Yale University and graduated in 1981. He completed an internship in internal medicine at Norwalk Hospital, followed by a residency in ophthalmology at Baylor College of Medicine-Houston in 1985.

Dr. Hamburg is a member of the American Board of Ophthalmology and the Harris County Medical Association.


Stephen Mahoney, M.D.


Dr. Stephen Mahoney is a dermatologist at West Houston Medical Center.

The long-time Houstonian graduated from Memorial High School and went on to graduate with honors from the University of Notre Dame.

Dr. Mahoney received his medical degree from the University of Texas Southwestern in Dallas, and completed his dermatology residency at the University of Texas at Houston. He has received extensive training in medical, surgical and cosmetic dermatology. Dr.

Mahoney has been in private practice at West Houston Dermatology since July of 1993.

Dr. Mahoney is certified by the American Board of Dermatology and is a Fellow of the American Academy of Dermatology. He holds an academic appointment as Clinical Assistant Professor of Dermatology at the University of Texas Medical School at Houston.

He has served on several national dermatology advisory boards, and lectures regionally on a wide range of topics. He is the medical director of cosmetic services at Advanced Aesthetic Institute (AAI), an aesthetic laser leasing company.

Todd Caliva, Chief Executive Officer

Todd Caliva has been Chief Executive Officer at West Houston Medical Center since 2006. Prior to coming to West Houston he was CEO at East Houston Regional Medical Center for three and a half years. Todd's focus is on employee, patient and physician satisfaction. His philosophy is that high satisfaction will impact the delivery of care and the success of the hospital. Todd is a Certified Healthcare Executive and the recipient of Modern Healthcare's Up and Comer Award, an award bestowed on healthcare executives under the age of 40.

Todd is a graduate of the University of Houston with a Bachelors in Marketing and Masters in Business. He began his healthcare career while in college working in positions such as business development, marketing, managed care, and physician recruitment. While completing his masters, he was the Director of Business Development at Doctors Hospital East Loop; Physician Services Manager at Columbia SunBelt Medical Center; Director of Business Development and then Associate Administrator at HCA East Houston Medical Center and Chief Operating Officer at The Woman's Hospital of Texas.

In addition to managing the hospital, Todd is committed to serving the community. He is the 2009 President Elect for the Houston West Chamber of Commerce and a 2007 Graduate of the 2007 West Houston Leadership Institute Class.

Todd is an avid golfer having attended the University of Houston on a four year golf scholarship. He and his wife are the parents of two daughters.

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