Fontan Operation and the Single Ventricle

Exercise-induced hypoxia predicts hypobaric hypoxia during flight in patients after Fontan operation

BACKGROUND

Hypobaric hypoxia (HH) during flight might be more detrimental to pulmonary circulation in Fontan patients compared healthy individuals. This study was designed to clarify whether exercise-induced hypoxia could predict HH during flight in Fontan patients.

METHODS AND RESULTS

Percutaneous oxygen saturation (SpO₂) was analyzed during flight in 11 Fontan patients and eight volunteers. SpO₂ was measured before taking off (S1), at the initial (S2), the end of stabilization (S3), and after landing (S4). The SpO₂-dynamics were compared with SpO₂-dynamics during cardiopulmonary exercise testing (CPX), pulmonary function, and hemodynamics in the Fontan patients. At all measurements, SpO₂ was lower in the Fontan patients than the volunteers during flight. The total SpO₂ decline from S1 to S3 was greater in the Fontan patients than the volunteers. While SpO₂ change from S2 to S3 was negative in the Fontan patients, it was stable in the volunteers. In the Fontan patients, the median value of exercise-induced SpO₂ decline (Ex-dSpO₂), SpO₂ at rest, and SpO₂ at peak was -6%, 93%, and 88%, respectively. In addition to exercise capacity and pulmonary function, the Ex-dSpO₂ was correlated strongly with SpO₂ at all phases during flight (r = 0.75-0.98, p < 0.01 for all). Flight-associated adverse events occurred in two patients with SpO₂ < 80% at S3.

CONCLUSIONS

Both the Fontan patients and the volunteers demonstrated similar SpO₂-dynamics during flight with a greater HH in the Fontan patients. CPX with SpO₂ monitoring is useful in predicting SpO₂-dynamics and adverse events during flight in these patients.

Epidural anesthesia for emergency cesarean section in a woman with Fontan circulation: A case report

RATIONALE

Anesthetic management of pregnant women with Fontan circulation remains challenging. There are few reports that describe the anesthetic management of cesarean section after Fontan surgery. Here, we present a case of successful epidural anesthesia in a woman with Fontan circulation who required emergency cesarean section.

PATIENT CONCERNS

A 29-year-old woman at gestational week 28 was scheduled for emergency cesarean section because of fetal distress. Her past medical history was significant for congenital transposition of the great arteries that had been treated by Fontan surgery 26 years earlier. Her postoperative course had been uneventful and she had reached a near normal level of activity with no arrhythmias or thrombotic complications. On presentation, her oxygen saturation was approximately 84% and she had digital clubbing. Arterial blood gas analysis showed a PCO2 of 35 mmHg, PO2 of 55.5 mmHg, and hemoglobin of 16.3 g/dL. Her blood coagulation parameters were within normal limits except for a high fibrinogen concentration (4.55 g/L).

DIAGNOSIS

The diagnosis was pregnancy requiring emergency cesarean section because of fetal distress.

INTERVENTIONS

Before anesthesia, a radial artery line was established for continuous measurement of blood pressure. An air pressure pump was placed on the patient's lower limbs and a low-dose dobutamine infusion was started. Next, epidural anesthesia was successfully performed at L2-3. Five milliliters of 2% lidocaine followed by 10 mL of 0.75% ropivacaine were injected. Dobutamine was infused to maintain a target blood pressure of 100-120/60-70 mmHg.

OUTCOMES

The procedure was uneventful with the patient maintaining a stable heart rate of 80 to 90 beats/min and an oxygen saturation of 90% to 94%. A male infant weighing 840 g was delivered. The Apgar score was 9 at 1 and 5 minutes. The patient was transferred to the intensive care unit for 20 hours of monitoring and discharged 9 days later. The neonate was discharged after 2 months of specialist neonatal treatment.

LESSONS

Epidural anesthesia may be used in women with Fontan circulation undergoing emergency cesarean section. Knowledge of the physiology of the heart lesion and that of pregnancy are critical to the outcome.

Cardiovascular management in pregnancy: congenital heart disease

The population of adults with CHD continues to expand,and thus the number of women with CHD who contemplate pregnancy or become pregnant is also growing. Mothers with low-risk defects can be managed by general cardiologist,whereas those with more complex defects should be managed by or with the assistance of ACHD cardiologists. It is important to acknowledge that all patients with CHD may have unique anatomy or physiology, despite their classification as having a simple, moderate, or complex defect. As such, clinicians evaluating these patients should have adequate knowledge and expertise when assessing patient's risk for pregnancy,when performing imaging or hemodynamic studies, and when managing these patients during pregnancy. The American Board of Medical Specialties has recently recognized ACHD as a subspecialty of cardiovascular disease to treat the specialized needs of these patients in adulthood. ACHD experts can provide expertise in the management of specific defects or lesions, imaging techniques, prepregnancy risk assessment,and can manage these patients or comanage them with other medical providers during their pregnancy. Because many of these ACHD patients are lost to follow-up in adulthood, pregnancy represents a time when these patients seek medical care(and for some, represents a time of vulnerability and increased risk). This represents an opportunity to establish or reestablish care with ACHD specialists and to reestablish continuing long-term care for their CHD. Pregnancy also provides an opportunity to create partnerships between primary care physicians,adult cardiologists, and ACHD specialists to provide optimal care for these women throughout their lives.

Patients with single-ventricle physiology: prognostic implications of stress testing

This study used a retrospective analysis of adults with single-ventricle physiology to ascertain the predictive power of cardiopulmonary stress-testing parameters in determining patients at increased risk of suffering from adverse clinical outcomes. We found that the specific parameters of percent of maximum predicted heart rate achieved and maximum oxygen consumption were significantly correlated with adverse clinical outcomes in patients with single-ventricle congenital heart disease.

Do neonates, infants and young children need a higher dose of enoxaparin in the cardiac intensive care unit?

BACKGROUND

Thromboembolic events are a serious complication occurring in critically ill children admitted to the cardiac intensive care unit. Although enoxaparin is one of the current anticoagulants of choice, dosages in children are extrapolated from adult guidelines. Recent data suggest that this population may need a higher dose than what is currently recommended to achieve target anti-factor Xa levels. The purpose of this study was to evaluate whether children less than 2 years old admitted to the cardiac intensive care unit require a higher enoxaparin dose than that currently recommended to achieve target anti-factor Xa levels.

METHODS

Retrospective chart review including patients who received enoxaparin for the treatment or prophylaxis of venous thrombosis between January, 2005 and October, 2007. Patients were classified as younger and older as well as prophylactic and therapeutic on the basis of age and enoxaparin dose, respectively. Younger patients were those 2 month old or less and older patients were those older than 2 months of age.

RESULTS

A total of 31 patients were identified; 13 (42%) were 2 months or younger and 25 (81%) were postoperative patients. Ten (32%) received prophylactic and 21 (68%) received therapeutic enoxaparin doses. To achieve optimal anti-factor Xa levels, enoxaparin dose was increased in all groups and reached statistical significance in all patients except those older than 2 months who received prophylactic enoxaparin. An average of 2.8 dosage adjustments was needed. No bleeding complications were reported.

CONCLUSIONS

Young children, infants, and neonates admitted to the cardiac intensive care unit required a significantly higher enoxaparin dose than that currently recommended to achieve target anti-factor Xa levels.

A novel heart structure and work mode hypothesis: parasitic ventricle theory

Parasitic ventricle hypothesis: a normal human heart is composed of four chambers that include two atria and two ventricles; the left ventricle is juxtaposed to the right ventricle. The left ventricle receives arterial blood from the left atrium and then ejects it into the general circulation, while the right ventricle receives venous blood from the right atrium and ejects it into the pulmonary circulation. So this structure restricts the arterial blood from mixing with the venous blood. But the heart of the patients suffering from single ventricle is composed of only one ventricle, and the patients can survive for several years, but eventually they die of hypoxemia induced by mixing up of arterial and venous blood in single ventricle. Based on these observations, we hypothesized that if an artificial akinesic ventricle device made of a biomaterial (such as pericardium autograft) (named as parasitic ventricle) is put into the single ventricle chamber of such patients, it would function as the right ventricle, and the single ventricle chamber is rendered to function as the left ventricle. Unlike the normal heart, this parasitic relationship enables to form a new type of heart structure. It has been found that the parasitic ventricle works relying on the function of the single ventricle, and the relationship of parasitism can be established between the two ventricles, "left ventricle" containing "right ventricle". This kind of heart structure can prevent the venous blood from mixing with the arterial blood; therefore, the patient in the absence of hypoxemia may survive longer. The theory is a completely new heart structure and work mode theory. We hope that this theory can open a new way to design a new operative procedure for effectively anatomically treating a patient with single ventricle. In addition, it may supply a new theory for designing a new total artificial heart with many advantages.

The adult with a Fontan operation

Since 1971, the Fontan operation has been performed for the repair of single-ventricle physiology. This ingenious operation commits a single ventricle to the systemic circulation and takes advantage of cardiovascular and respiratory physiology to propel deoxygenated blood to the lungs, thus minimizing right-to-left shunting and cyanosis. Initially performed as a right atrial to pulmonary artery anastomosis, the Fontan operation has gone through evolutionary steps that have resulted in progressive improvements in mortality, morbidity, and outcomes. Inclusion of the right atrium in the slow-flowing Fontan circuit results in progressive dilation and incessant arrhythmias. This spurred forth efforts to create modifications that partially or completely exclude the atrium from the Fontan circuit. The transcatheter completion of the Fontan operation has been performed in a small number of patients and we expect minimally invasive, transcatheter, and hybrid interventions to play an important role in the future management of these patients.