Selective Intrauterine Growth Restriction (sIUGR) or Twin-Twin Transfusion Syndrome (TTTS)? (9 of 9)

Selective Intrauterine Growth Restriction (sIUGR) or Twin-Twin Transfusion Syndrome (TTTS)? (9 of 9)


>>SOMETIMES FAMILIES COME
TO US WITH THE DIAGNOSIS OF TTTS AND IT TURNS OUT
TO BE SOMETHING MORE LIKE SELECTIVE INTRAUTERINE
GROWTH RESTRICTION, OR SIUGR. TTTS AND SIUGR ARE RELATED
BECAUSE THEY INVOLVE THE SAME COMMON SHARED PLACENTA
BETWEEN THE TWO BABIES. WHAT DIFFERENTIATES THEM
IS THE VASCULAR CONNECTIONS BETWEEN THE TWO BABIES.>>OFTEN THE DIFFERENCES
BETWEEN SIUGR AND TWIN-TWIN TRANSFUSION SYNDROME CAN
IN FACT BE VERY SUBTLE. THROUGH THE USE OF DOPPLER
ULTRASOUND WE CAN HELP TEASE OUT THE FACTS THAT SUPPORT
ONE PARTICULAR DIAGNOSIS VERSUS ANOTHER. AND THROUGH DOPPLER
ECHOCARDIOGRAPHY WE CAN IDENTIFY THE DIRECTION
OF BLOOD FLOW, THE VELOCITY OF BLOOD FLOW,
AND ALSO DETERMINE PATTERNS OF BLOOD FLOW.>>ONE OF THE THINGS
THAT WE LOOK AT, OF COURSE,
IS CARDIAC CHANGES. IN TTTS THERE IS A VERY
CHARACTERISTIC PROGRESSIVE SERIES OF CHANGES THAT
HAPPENS IN THE LARGER TWIN DUE TO THE EXTRA VOLUME THAT
COMES FROM THE SMALLER TWIN TO THE LARGER TWIN.>>BLOOD IS EXCHANGED FROM
ONE TWIN, THE DONOR, INTO THE RECIPIENT. AND THEN AS A CONSEQUENCE
THERE’S A HUGE CASCADE OF HORMONAL CHANGES THAT TAKE
PLACE THAT THEN BRINGS ABOUT THE CARDIOVASCULAR
MANIFESTATIONS IN THE RECIPIENT.>>IN SELECTIVE IUGR THERE
ISN’T THIS TRANSFER OF VOLUME. YOU KNOW, THERE’S NOT
THIS NET SHIFT OF VOLUME FROM TWIN TO THE OTHER. IT’S MUCH MORE BALANCED,
BUT THAT BALANCE, YOU KNOW, CAN BE A
TENUOUS BALANCE.>>IN THE SMALLER TWIN
THERE IS AN ABNORMALITY OF PLACENTAL SHARING.>>THE SMALLER BABY HAS
A MUCH SMALLER PORTION OF THE PLACENTA.>>AND THE RESISTANCE IN
THE UMBILICAL ARTERY OF THAT PARTICULAR TWIN IS
MUCH HIGHER THAN NORMAL, RESULTING IN ALTERATIONS IN
GROWTH IN THE SMALLER TWIN.>>SELECTIVE INTRAUTERINE
GROWTH RESTRICTION HAS BEEN RECOGNIZED FOR A LONG TIME,
BUT IT’S ONLY BEEN IN THE LAST DECADE THAT WE’VE
BEEN ABLE TO SEE THAT THERE ARE DIFFERENT FORMS OF IT. THERE’S A MILDER FORM,
WHICH WE CALL TYPE I. THERE’S A MORE SEVERE
FORM THAT WE CALL TYPE II. AND THEN THERE’S A NEW
ENTITY THAT’S REALLY ONLY BECOMING UNDERSTOOD,
THAT’S COME OUT IN THE LAST FEW YEARS, THAT’S THE TYPE III
SELECTIVE IUGR. SO IF WE WERE TO LOOK AT A
NORMAL PLACENTA THERE WOULD PROBABLY BE A LARGE NUMBER
OF CONNECTIONS BETWEEN BOTH FETUSES. THERE’S KIND OF A SENSE
OF BALANCE THERE. SO THE SHIFTS IN BLOOD
IN ONE DIRECTION WOULD BE OFFSET BY SHIFTS IN BLOOD
IN THE OTHER DIRECTION. IN TYPE I SELECTIVE IUGR
WHAT YOU NOTICE IS PERHAPS A 60/40 DISTRIBUTION
OF PLACENTAL AREA. BUT YOU SEE A DECREASE IN
THE NUMBER OF CONNECTIONS THAT MEANS THAT THERE CAN’T
BE AS DYNAMIC A SHIFT IN BLOOD VOLUME
BETWEEN THE TWO TWINS. WHEN YOU GO TO THE TYPE II
SELECTIVE IUGR YOU START TO SEE A MUCH SMALLER PORTION
OF PLACENTA FOR THE ONE THAT DEVELOPS THE INTRAUTERINE
GROWTH RESTRICTION. YOU ALSO NOTICE THAT
THE NUMBER OF VESSELS, AGAIN, DECREASES EVEN MORE. THEY TEND TO BE BALANCED SO
THAT THE NUMBER OF ARTERY TO VEIN CONNECTIONS FROM
THE SMALLER TO THE BIGGER IS STILL OFFSET BY ARTERY
TO VEINS IN THE OTHER DIRECTION, BUT THE
NUMBERS ARE MUCH, MUCH FEWER. AND SO, AGAIN, IT’S THIS
IDEA OF DYNAMIC SHARING THAT IS MORE RESTRICTIVE. AND THAT FORCES THE FETUS
WITH THE SMALLER PORTION OF PLACENTA TO REALLY TRY TO
SURVIVE ON WHAT IT’S GOT AS FAR AS PLACENTAL MASS. AND THE LESS VOLUME
OF THE PLACENTA IT HAS, THE MORE IT STRUGGLES. IN THE TYPE III SELECTIVE
IUGR THEY HAVE JUST A SMALL, SMALL PROPORTION
OF THE PLACENTA. THERE TENDS TO BE A HIGHER
PROPORTION OF ARTERIES CONNECTING TO VEINS FROM THE
NORMAL BABY TO THE SMALLER BABY, BUT IT’S A VERY
SMALL PLACENTAL AREA. AND THAT’S LED TO
THE CONCEPT OF RESCUE TRANSFUSION, THE LARGER BABY
BEING ABLE TO SEND BLOOD TO THE OTHER SIDE
OF THE PLACENTA. AND SO THOSE CONNECTIONS
ARE ABSOLUTELY VITAL FOR THE SMALLER
BABY’S SURVIVAL. THE OTHER CHARACTERISTIC
FEATURE IN TYPE III SELECTIVE IUGR IS A VERY BIG
ARTERY TO ARTERY CONNECTION. THERE CAN BE RAPID SHIFTS IN
BLOOD IN EITHER DIRECTION. THESE HIGH VOLUME SHIFTS OF
BLOOD FROM ONE BABY TO THE OTHER RESULTS IN THE BLOOD
PRESSURE GOING UP AND GOING DOWN AND GOING UP
AND GOING DOWN, AND THAT APPEARS TO
RESULT IN INJURY. SO WHILE THIS CONNECTION IS
VITAL TO KEEPING THE SMALLER BABY ALIVE, IT CAN
POTENTIALLY RESULT IN A BRAIN INJURY TO THE NORMAL
BABY AND IT CAN ACTUALLY KILL THE SMALLER BABY
BECAUSE OF THIS JUST SUDDEN RAPID SHIFT IN BLOOD
PRESSURE AND VOLUME. SO IN TYPE III
SELECTIVE IUGR, IT’S A VERY, VERY
DEPENDENT AND VERY, VERY DYNAMIC RELATIONSHIP
BETWEEN THE TWO TWINS AND THE CONNECTIONS
IN THE PLACENTA.>>THE SCIENCE AND THE
PRACTICE OF MANAGING TWIN COMPLICATIONS SUCH AS
TWIN-TWIN TRANSFUSION SYNDROME OR SIUGR
PERHAPS, IN EFFECT, HAS ONLY EXISTED
FOR ABOUT A DECADE.>>UNDERSTANDING THE TTTS
STORY HAS BEEN VITAL IN OUR UNDERSTANDING OF HOW TO
DIFFERENTIATE THAT PROBLEM FROM THE SELECTIVE
IUGR PROBLEM.>>HIGH VOLUME EXPOSURE
TO THESE PATIENTS IS CRITICAL IN BEING ABLE TO
LEARN WHAT TO EXPECT.>>THAT HIGH
VOLUME, THAT EXPERIENCE, AND THAT COLLABORATION IS
WHAT MAKES US A REALLY GOOD PLACE AND ALLOWS US TO
REALLY TAILOR MANAGEMENT FOR EACH INDIVIDUAL PATIENT TO
OPTIMIZE AND TRY TO ACHIEVE THE BEST OUTCOME POSSIBLE.

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