>> 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.