May 2006
Cryoablation: A Safer Method for Treating Rhythm Disturbances
Cryoablation: A Safer Method for Treating Rhythm Disturbances
Volkan Tuzcu, M.D.; Director of Electrophsiology and Pacing, Arkansas Children's Hospital; Associate Professor of Pediatrics, University of Arkansas for Medical Sciences College of Medicine
Electrophysiology and catheter ablation procedures lead to permanent cure in the majority of patients with tachyarrhythmias. Until recently, RF catheter ablation has been the conventional technique of elimination of abnormal cells responsible for these problems. Using this approach, successful treatment can be achieved in more than 90 percent of patients. Because long-term medication management does not lead to cure and also due to the concerns with medication side effects, most patients and physicians prefer catheter ablation procedure as their treatment approach.
Lately, cryoablation has been used throughout the world for the ablation of tachyarrhythmias originating from the high-risk areas in the heart. Since cryoablation allows us to freeze at different temperatures and therefore reversible effect can be tested, the chance of adverse effects with the ablation in these risky spots has been virtually eliminated. This benefit is even more significant in young children.
We have been utilizing cryoablation as the primary choice of catheter ablation in children for the majority of problems, unlike other centers where it is used only in high-risk areas in the heart. Despite its safety profile, the freezing effect of cryoablation required modification of the technique in order to increase the success rates. Most of the recent studies have reported lower success rates with cryoablation compared to RF ablation, however due to the safety factor it is still utilized commonly. Using our three-dimensional mapping system to guide us in reaching the precise treatment spots, we have achieved similar acute success rates with cryoablation compared to RF ablation. Recent experience with the accessory pathways has revealed acute success rates of about 94 percent. So far, no complications have occurred with the procedure. Besides, no significant complications have been reported thus far in the world.
The future of the tachyarrhythmia management likely will be impacted significantly with the introduction of cryoablation. Catheter ablation is likely to be the primary choice of treatment for most patients and physicians. This is even more significant in children because adverse effects are more likely with the RF ablation in small hearts. Arkansas Children’s Hospital will continue to contribute to the medical and scientific community in the advancement of this new technique’s application in children.Near Infrared Spectroscopy (NIRS) and its application in the Heart Center
Adfnan T. Bhutta, MBBS, FAAP; Co-Medical Director, Cardiovascular Intensive Care Unit, Arkansas Children’s Hospital; Instructor, Pediatric Critical Care Medicine and Cardiology, University of Arkansas for Medical Sciences College of Medicine
In December 2005, the Heart Center started using a new monitor called the INVOS® cerebral
oximeter. Cerebral oximetery is a new patient safety monitor and management
tool that has been shown to significantly reduce adverse neurological outcomes.
The cerebral oximeters use near-infrared spectroscopy (NIRS) to non-invasively
and continuously monitor changes in blood oxygen saturation. It directly monitors
changes in the regional oxygen saturation (rSO2) of the predominately venous
blood in the brain, which is influenced by oxygen delivery and consumption.
When changes in oxygen delivery or consumption occur, the physician can respond
with simple interventions to minimize or prevent brain injury.
The use of NIRS technology was first described in humans in the 1970s. Since then, the NIRS based technology has found diverse applications in monitoring of deltoid muscle oxygen supply to guide resuscitation, monitoring of splanchnic circulation in neonates with acute abdomen, and in measurement of regional blood supply in skeletal muscles to assess effects of exercise.
However, the most common application of this technology has been in assessing
regional cerebral saturation. This application stems from the multiple
studies which have shown a positive correlation between cerebral oxygenation
as measured by NIRS and jugular venous saturation. One of theses studies was
conducted by members of our heart team at Arkansas Children’s Hospital.
Clinical studies in adults have suggested that a decline in rSO2 values of >20
percent from baseline or absolute values of less than 50 are associated with
decreased cognitive function and prolonged ICU stay . Such a sharp decline
from a baseline measurement or a low absolute value may affect long-term neurological
outcome.
As many as 50 percent of neonatal patients undergoing cardiac surgery on cardiopulmonary
bypass (CPB) are at risk for developing mild ischemic lesions, primarily in
the form of PVL, postoperatively. Therefore, a monitor that allows clinicians
to follow trends in cerebral oxygenation could identify critical periods associated
with inadequate oxygenation, which in turn could lead to early interventions
to minimize such periods.
After initially being utilized in the operating rooms, it is now increasingly being used as a non-invasive method to monitor regional oxygen saturations during post-operative period after cardiac surgery; and some experts have suggested that rSO2 should be routinely used to guide therapy to minimize periods of low oxygen delivery.
In November 2005, Somanetics Corporation (the makers of the only commercially available NIRS monitors in the United States) received clearance from the FDA to expand monitoring with the INVOS® system in regions of the body other than the brain. This allows monitoring of oxygen in skeletal muscle tissues and abdominal organs in addition to the brain (commonly referred to as regional somatic saturation) . When combined with brain oxygenation monitoring, additional information is available for clinical decision-making in infants and children in the operating room and critical care areas.
The non-invasive measurement is made with two sensors, called SomaSensors. Harmless near-infrared light passes through the skin into deeper tissue. With two detectors at different distances from the light source, two depths of penetration are measured. The difference in these measurements eliminates signals common to both, minimizing changes occurring in superficial tissue such as the skin.
Continuous visibility of cerebral and somatic oxygen saturation levels allows individualized patient care in real time and alerts the team members of a potential problem much earlier. This has been not as easily possible in the past, as it required placement of invasive catheters and lines inside the heart, veins or pulmonary arteries. We hope that the availability of this device at each bed in the CVICU and for selected patients on CV East will further enhance the ability of our team to provide the best possible care for our patients.
Early Detection of Heart Transplant Rejection: Room to Improve
R. Erik Edens, M.D., Ph.D.; Assistant Professor of Pediatric Cardiology, University of Arkansas for Medical Sciences College of Medicine; Arkansas Children’s Hospital Research Institute
Every year more than 25,000 organs are transplanted into patients in the United States, according to data from the United Network for Organ Sharing. This includes nearly 300 pediatric heart transplants. Organs transplanted from one person to another are continually at risk of being recognized by the recipient’s immune system and rejected. In patients who have received heart transplants, rejection may result in severe illnesses and even death.
Heart transplant rejection is challenging to diagnose. Essentially, two primary techniques are used to detect rejection: heart biopsy and echocardiogram. Heart biopsy is a procedure conducted in the catheterization laboratory during which tiny pieces of the heart are removed for examination under a microscope. When rejection occurs, we see a type of white blood cell called a lymphocyte amongst the heart muscle cells where normally no lymphocytes would be present (see pictures). Heart biopsies are procedures that children uniformly dislike. They also are somewhat invasive and carry some procedural risk. The development of new testing that could decrease or even eliminate the need for heart biopsies would be welcomed by patients, families and doctors alike.
The second method commonly used to detect rejection is echocardiography. An echo is an ultrasonic picture of the heart used in transplant patients to examine how well the heart is functioning and to determine the thickness of the heart muscle. Echo images can provide important clues about the possibility of rejection. Unfortunately, echo is not capable of detecting rejection at early stages and sometimes significant damage can occur to the transplanted heart before rejection can be detected by echo. Clearly, better methods to detect rejection early and easily are needed to improve the survival and health of these special patients.
Immunologists have recognized for decades that immune cells communicate with one another in our bodies by sending small proteins through the bloodstream to other cells. These protein messages are different depending on what the cell wants to communicate to the other cells. For example, there likely are different proteins released when infection occurs than when rejection occurs. It likely would be tremendously helpful to doctors and nurses caring for transplant patients to be able to detect and decode these protein messages and thus understand what the immune system is doing at any given time.
Until recent years we have had only very limited ability to test the blood of transplant patients for these protein messages. Most previous testing methods required several teaspoons of blood for each protein to be tested. A recent technological advance called Luminex Bead Array uses a dual laser detection system and is so sensitive that up to 100 proteins can be detected on as little as two drops of blood. The ACH Research Institute purchased one of these instruments in 2004, and it has been used in a variety of research projects conducted at ACHRI.
We have received grant funding to pay for testing of transplant patient serum using the Luminex instrument. A team of researchers from Cardiology, Microbiology & Immunology, Pathology and Biostatistics are assisting us in this endeavor. Our hope is that the Luminex technology will allow us to develop a safe and rapid blood test for transplant patients that will allow us to detect rejection at earlier stages, and thus to change treatment plans before any damage occurs to the transplanted heart.
Ventricular Assist Device (VAD) for Children
Michiaki Imamura, M.D., Ph.D .; Pediatric Cardiac Surgeon, Arkansas Children’s Hospital; Assistant Professor, Department of Surgery, University of Arkansas for Medical Sciences College of Medicine.
Management of Severe Heart Failure
The heart is the organ pumping blood in two directions: to the whole body and
to the lungs. The heart has two pumping chambers of the left and right ventricles. The
left ventricle is pumping blood to the whole body. The right ventricle is
pumping blood to the lungs.
When the people suffer severe heart failure (decrease in pumping ability of
the heart), medical treatment is instituted at first. After the medical
treatment is maximized or is expected not to be enough to control heart failure,
surgical treatment is considered. Occasionally, the mechanisms of this
heart failure are anatomical problems of holes inside the heart, narrow pathways
of the blood or malfunctioning valves. In these situations conventional operations
of closing holes, opening pathways or repairing valves are performed. In other
instances, the mechanism of heart failure is the heart muscle itself. This
problem may be temporary or permanent. If the patient is suffering severe
heart failure temporarily, the patient is treated with mechanical circulatory
support of ECMO or VAD. The use of this machine is called “bridge
to recovery”. If a child is suffering heart failure permanently,
the patient needs cardiac transplantation. While waiting for cardiac transplantation,
some patients experience further deterioration and need ECMO or VAD. This type
of usage is named “bridge to transplantation”.
Additionally, in some cases only the left or right ventricle gets severe heart
failure, in the other cases both right and left ventricles get severe heart
failure.
What is ECMO?
The ECMO is extracorporeal membrane oxygenation, and consists of tubes, artificial
heart (pump) and
lung (oxygenator). This modality has been used at our center for more
than 15 years. Our center has among the most experience in the world
in this modality. This system works great for relatively short
periods of up to two weeks. Occasionally, we need to continue this
usage more than two weeks. The benefits of this system are that it is a simple
procedure and it provides support for the lungs. ECMO is the only mechanism
able to provide support to both the heart and lungs. The deficits of this
support are high tendency of cerebrovascular event (stroke and cerebral bleeding),
necessity of periodical circuit change and inability of free mobilization.
With this system, children usually need mechanical ventilatory support with
an endotracheal tube and cannot eat by themselves.
What is VAD?
VADs consist of tubes, pumps and power sources and controllers. Blood
is sucked from the heart and returned to the circulation, and this can assist
the heart in pumping blood. There are several kinds of classification
of VADs. One is intracorporeal (pump is staying inside the body) or extracorporeal
(outside the body). The other is pulsatile and non-pulsatile. The last
is LVAD, RVAD and BiVAD. LVAD is the abbreviation of left ventricular assist
device: helps the left ventricle. RVAD is that of right ventricular assist
device: helps the right ventricle. BiVAD is that of biventricular assist device:
helps both the left and right ventricles. BiVAD is the support of two ventricles. Some
systems have the ability to be used as BiVAD. Others are only used as
LVAD.
In adults, several types of VADs such as HeartMate, Novacor, Abiomed, Thoratec
and DeBakey have been used for more than decade.
The advantages of VAD are that it is easy to mobilize the patient after implantation
and the durability of longer period support. The disadvantages of VAD
are bleeding, infection, thromboembolism (stroke), hemolysis (red blood cell
damage), and necessity of median sternotomyoperation (heart surgery). Previously,
several adolescent patients required these types of support in our hospital.
They were transferred to another adult hospital in town and had implantation
there. In our heart center, we have used two kinds of VAD in the last
two years. One is DeBakey VAD Child, and another is Berlin Heart.
What is DeBakey VAD Child?
DeBakey VAD Child is a miniaturized heart pump. This pump works by electromagnetic
energy, which
creates a magnetic field. The pump consists of an external part and an
internal part. The internal part with propels is rotating and blood flows
between these two parts. This heart pump is named after its designer
and renowned heart surgeon Michael DeBakey. This pump creates flow
continuously and does not create pulsation.
This machine was first manufactured for the adult. Recently, tubing parts of
this machine were modified to fit to children. DeBakey VAD Child has
the same actual pump part as the regular DeBakey VAD. In September 2004,
we performed the second implantation of this type of device in a 14-year-old
boy. Subsequently, this patient had successful cardiac transplantation.
What is Berlin Heart?
Berlin Heart is a paracorporeal (outside the body) pneumatic pump VAD. Blood
is sucked into the pump
and ejected into the artery. This pump produces pulsation. This VAD has
awide range of different sizes of pumps and cannulae. This pump has been
used in patients ranging from neonates to adults. This device currently
is not allowed by the FDA for use. For this system, usage permission
from the FDA is required each time. Since April 2005, we have used this
device four times. Two patients had BiVAD and others had LVAD. The second
patient had successful bridge to transplantation. The last two patients
were on support on April 14, 2006. A total of 41 pediatric patients inthe
United States had this device from 2000 through April 14, 2006.
What is the difference between DeBakey VAD Child and Berlin Heart?
DeBakey does not create pulsation, but Berlin Heart does. The pump of
the device is outside the body in Berlin Heart and is inside the body in DeBakey
VAD Child. DeBakey VAD Child has better ambulation after implantation. Berlin
Heart has an ability to be used as RVAD or BiVAD as well as LVAD. DeBakey
VAD Child is only used for LVAD.
What is the future direction of ACH Heart Center for Heart Failure
Management?
Because we have been taking care of a large number of heart failure patients
with ECMO, VAD and cardiac transplantation, we are one of theleading centers
for managing pediatric heart failure.
We have to keep up with new medical and surgical advancements in this field. We have to keep improving and evolving our team. Since 2004, six children’s hospitals in the United States, including our hospital, were chosen to use DeBakey VAD Child.
Luis M. Zabala, M.D.; Assistant Professor of Anesthesiology, section of Pediatric Cardiac Anesthesiology, University of Arkansas for Medical Sciences College of Medicine; Arkansas Children’s Hospital
Lynn Harness, C.C.P.; Department of Pediatric Perfusion, Arkansas Children’s Hospital
The repair of congenital heart defects in the pediatric population requires,
in many instances, extracorporeal circulation by means of cardiopulmonary
bypass (CPB). The CPB circuit must be primed with either blood or crystalloid
solution to provide an air-free circuit to be integrated with the patient’s
own circulation. Once on bypass, hemodilution takes place. Consequently,
the concentrations of all cellular and protein components in the intravascular
compartment decrease, thus decreasing plasma oncotic pressure. A decrease
in intravascular oncotic pressure causes fluid to move towards the extra
vascular space to tissues with higher oncotic pressure, producing edema.
This affects all organs, including kidneys, brain, liver, heart and lungs.
Another effect of CPB is the initiation of a complex sequence of humoral and cellular interactions responsible for a generalized inflammatory reaction which leads to increased vascular permeability and postoperative tissue edema. Such events occur during exposure of the patient’s blood to the surfaces of the CPB circuit. In addition to hemodilution, this inflammatory reaction is associated with increased bleeding, generalized edema, myocardial depression, low cardiac output, prolonged respiratory impairment and prolonged ICU stay.
Strategies intended to improve outcomes in pediatric patients following cardiopulmonary bypass (CPB) have been aimed primarily at improving surgical techniques, controlling the inflammatory response through anesthesia and perfusion interventions, and at limiting the degree of hemodilution during extracorporeal circulation.
Overwhelming improvements have unfolded in the field of pediatric congenital heart disease over the past two decades. A better understanding of the patient’s response to extracorporeal circulation has prompted the search for a “magic recipe” in an attempt to improve clinical outcomes. At our institution, the combination of superior surgical skills, patient-specific anesthesia techniques and innovative perfusion strategies has set us apart from other pediatric institutions. This brings us closer to our goal: the best outcome possible.
The addition of modified ultrafiltration (MUF) to the management strategy of our patients represents a step forward in achieving better clinical outcomes. MUF is a technique that removes excess fluid from the patient’s vascular system, thus increasing colloid oncotic pressure. By restoring intravascular colloid oncotic pressure, the fluid gradient generated by hemodilution reverses, creating a net movement of fluid back into the intravascular space, decreasing tissue edema.
MUF is performed after weaning the patient from CPB but before protamine administration and arterial decannulation. The mechanics of our circuit involve withdrawing blood from the aortic cannula, pumping the blood through a filtration unit and re-infusing warm hemoconcentrated blood into the patient through a venous cannula. The result is blood with a high oncotic pressure. This hemoconcentrated blood is then reinfused directly into the patient’s right heart/lungs before entering the systemic circulation. This helps reduce pulmonary edema.
MUF is usually instituted at a rate of 10-30 ml/kg with a target volume of
ultrafiltrate of 15-30/ml/kg/min over an interval of 10 to 15 minutes. Also,
blood from the venous reservoir of the CPB circuit is pumped to the MUF circuit;
this allows processing of the extracorporeal circuit volume and re-infusion
of this hemoconcentrated circuit volume along with the patient’s hemoconcentrated
blood through the venous cannula. End points of MUF vary among pediatric institutions
and can be defined by time, total volume removed, or goal hematocrit. At our
institution, we utilize MUF for a period of at least 10 minutes with great
success.
The use of this technique has provided consistent evidence of reduced postoperative
blood loss, decreased blood product transfusion and significant reduction in
the accumulation of total body water following CPB. The reduction in total
body water is associated with improved respiratory mechanics, improved myocardial
function, increased blood pressure and increased hematocrit following MUF.
In addition, some authors suggest that MUF attenuates the CPB induced coagulopathy
and significantly decreases certain pro and anti-inflammatory mediators responsible
for acute renal failure, prolonged mechanical ventilation, and capillary leak
syndrome, among others.
Social Work in the Heart Center
Janna Vandiver, LMSW; clinical social worker in the CVICU and Cardiology Clinic, Arkansas Children’s Hospital
Many times when families are admitted to the hospital, they do not expect to meet a social worker as part of their care team. However, here at ACH we have 25 master’s level social workers who serve our families. What does a medical social worker do? The goal of social work in the Heart Center is to recognize the impact of illness on patients and their families and to assist families in coping with the unpredictability of illness. Most patients admitted to the Heart Center are scheduled to undergo or have already undergone heart surgery or another procedure. This can be a frightening time for both the patient and his or her family. Depending on the age of the patient, a social worker will work with the patient and family members to assess their understanding of the patient’s diagnosis, condition and treatment. The social worker will complete an assessment to gather information about their social support and life outside the hospital. This information will help to determine what, if any, assistance they may need from social work, the hospital or outside agencies.
During the hospitalization, a social worker will continue to provide support to families as they experience the emotional ups and downs that often occur while their child is in the hospital. Some examples of interactions that a social worker would have with a family might be problem solving and conflict resolution, advocating for the family’s or patient’s needs or preferences, facilitating communication with other staff and providing encouragement to get involved and be informed about the care of their child.
Social work also performs a variety of other duties in the Heart Center. For example, a social worker is assigned to every heart transplant patient to provide support for the family throughout its journey. An assessment is conducted before a patient is listed for a heart, and emotional support is provided during the transplant process and post transplant during clinic visits. When a death occurs in the Heart Center, a social worker is present at the time of death to provide support and written grief materials, to assist with contacting a funeral home and also to follow up with bereavement support after the family returns home. Families may need concrete services during their hospitalization such as transportation or lodging arrangements, and a Family Services Assistant (who is also part of the Social Work department) can provide assistance and appropriate referrals for those needs.
When families come to ACH they are faced with new sights, new sounds, new people and in the Heart Center they may be learning a new vocabulary about their child’s heart condition. Any information we can obtain about a family to make the care we provide more personal and individualized will help us serve the families with care, love and hope. Our goal is for ACH to meet not only the medical needs of the family, but also the emotional and psychosocial needs, in order to make a potentially overwhelming experience more positive for the patient and his or her family.
Spotlight on Kris McCullough,
R.N.
Nurse in the CVICU
What is your role at ACH, and how long have you worked here?
I am an R.N. in CVICU – East. I have worked at ACH for two and
a half years.
Why is your job rewarding?
It is very fulfilling to see patients come in so sick and see them being discharged
able to walk without using oxygen or able to eat without working up a sweat
and running out of breath. Or when our patients come in for clinic visits
and take the time to come upstairs to see us, and they’re smiling and
doing so well, it makes everything we do worthwhile.
How did you become interested in pediatric cardiology or cardiovascular
surgery?
I was an adult-care cardiac nurse prior to coming to ACH. The heart has
always fascinated me because of all of the problems that can occur; whether
congenital or not, and still function. After taking a couple of years off from
nursing and getting a B.B.A. in Finance, I decided that I might be able to “handle” pediatrics,
and I really wanted to stay in cardiology. I didn’t realize that
adult cardiology and pediatric cardiology have absolutely NOTHING in common! I
haven’t regretted it yet!
What do you want people to know about the Heart Center at Arkansas
Children's Hospital?
That everything we do is for the patient. Our staff is knowledgeable and approachable.
From the surgeons to housekeeping, we all contribute a part in the patients’ care.
We do what we do because we enjoy it. We attempt to make the patient and family
as comfortable as we can so they can feel confident in the care their child
is getting.
What do you enjoy most about working with children?
The perks! There is nothing better than holding a baby and having them smile
up at you or fall asleep on your shoulder. When the family stops by to see
us after a clinic visit, you know that somehow, you have touched that family
in a positive way, and they are very grateful for that.
What has been your most memorable moment working in the Heart Center
at Arkansas Children's Hospital?
I have a bunch of good memories, but the most memorable would be one that happened
very recently. One of our patients, who had been through a couple of transplants
and had recently been put on comfort-care and then became one of our “miracles”,
had asked another nurse to come tell me “not to be afraid to come see” her.
It was wonderful to think that she had thought of me (along with many others,
but what an honor to be included in this group of people!) when she really
needed to be thinking about getting better. This “miracle” is why
I tell people that I became a nurse. No matter how bad it gets, the good always
outweighs the bad.
What is your greatest professional achievement?
Actually, my greatest professional achievement is non-nursing. It was
being chosen “Outstanding Student in General Finance” and being
asked to be a Marshal and walk at the head of the line at graduation.
Spotlight on Wes McKamie, C.C.P.
Perfusionist, Pediatric Cardiothoracic Surgery
What is your role at ACH, and how long have you worked here?
I am a cardiovascular perfusionist, and I will have my one-year anniversary
in June of 2006. This is my second time as an employee of ACH. I worked
as a Respiratory Therapist from 2000 to 2003.
How is your job rewarding?
I feel my job is rewarding in a number of ways. I not only get to do something
that I am fascinated by, but I also get to be a part of giving children second
chances at life.
How did you become interested in pediatric cardiology or cardiovascular surgery? During my time as a respiratory therapist, I became part of the ECMO team here, and that is what opened my eyes to the world of cardiac surgery and perfusion. I felt that this area of service would keep me consistently motivated and give me a chance to grow professionally.
What do you want people to know about the Heart Center at Arkansas
Children's Hospital?
It is a place that truly is filled with some of
the best individuals I have ever met. The amount of care and compassion
that I see given to the children we serve here is amazing.
What do you enjoy most about working with children?
Working with children is very rewarding because you know that you are helping
someone who has a lot of promise before them. These kids have been faced
with some tremendous challenges and to see them overcome those day in and
day out is a great feeling.
What has been your most memorable moment working in the Heart Center
at Arkansas Children's Hospital?
So far I would have to say the placement of the Berlin Heart into our hurricane
victim and then transplanting him would have to be my most memorable moment.
What is your greatest professional achievement?
My greatest achievement thus far is being hired to be a part of one of the
best heart centers in the country.
New Nurses in the Heart Center
During the last few months, the Heart Center at Arkansas Children’s Hospital welcomed 13 new nurses to the team. We are excited to have them on-board to help us better fulfill our mission of providing care, love and hope to the region’s youngest cardiac patients.
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