Systemic ventricular assist device support in Fontan patients: A report by ACTION.

BACKGROUND: The size of the Fontan population with end-stage heart failure is growing. In this population, heart transplantation has been the only option. This study sought to investigate the efficacy of ventricular assist device (VAD) support in Fontan patients. METHODS: We conducted a retrospective study of Fontan patients in the Advanced Cardiac Therapies Improving Outcomes Network. We evaluated patient characteristics, and the clinical and physiologic outcomes after VAD implantation. RESULTS: We identified 45 Fontan patients implanted with VAD. The average age of patients was 10 years (interquartile range: 4.5-18) and 30% were female. The majority had a morphologic right ventricle (69%), moderate or greater ventricular dysfunction (83%), and moderate or greater atrioventricular valve regurgitation (65%). The majority of implants were as a bridge to transplantation (76%), and the majority of patients were Interagency Registry for Mechanically Assisted Circulatory Support Profile 2 (56%). The most commonly employed device was the Medtronic HeartWare HVAD (56%). A total of 13 patients were discharged on device support, and 67% of patients experienced adverse events, the most common of which were neurologic (25%). At 1 year after device implantation, the rate of transplantation was 69.5%, 9.2% of patients continued to be VAD supported, and 21.3% of patients had died. Hemodynamically, VAD was effective in decreasing both Fontan and ventricular end-diastolic pressures in some individuals. CONCLUSIONS: VAD is effective in supporting patients with end-stage Fontan failure awaiting heart transplantation. Future research should focus on identifying clinical and physiologic characteristics predictive of a favorable response to VAD support.

A technique for maintenance of airway access in infants with a difficult airway following tracheal extubation.

Tracheal extubation of patients with a difficult airway represents a challenge to anaesthesiologists and intensive care physicians. While a variety of techniques designed to maintain access to the airway in case of the need for tracheal reintubation have been described in adults, no reports have been published in infants and young children. We describe an approach to this issue in a young child with severe micrognathia.

Outcome while awaiting heart transplantation in children: a comparison of congenital heart disease and cardiomyopathy.

BACKGROUND: Outcomes for children who undergo heart transplantation differ for children with congenital heart disease as compared to those with structurally normal hearts. Similar data have not been reported for these groups of patients for the morbidity and mortality associated with waiting for a donor. We report these data. METHODS: A retrospective review was performed for all pediatric patients who were listed for heart transplantation at Stanford from 1977 to 1996, comparing mortality and major morbidity for patients with congenital heart disease and those with cardiomyopathy and structurally normal hearts. RESULTS: There were 96 patients who met study criteria, of whom 67 were successfully transplanted. The median waiting time was 23 days. Survival at 30 days was 93% and at 90 days was 81%, with no difference between groups. Major complications were identified in 38% of patients with structurally normal hearts, vs 9% of patients with congenital heart disease (p < 0.001). CONCLUSIONS: Overall mortality is similar for patients with congenital heart disease and those with structurally normal hearts while listed for heart transplantation, but patients with congenital heart disease have fewer episodes of major morbidity during this time.

Safety and utility of the routine surveillance biopsy in pediatric patients 2 years after heart transplantation.

OBJECTIVES: The standard for diagnosing allograft rejection after heart transplantation is the endomyocardial biopsy, but the value of routine surveillance biopsies after 2 years after transplant is controversial. The objective of this study was to determine the necessity and safety of surveillance biopsies and to correlate rejection with signs and symptoms beyond the second post-transplant anniversary in pediatric patients. STUDY DESIGN: We reviewed the results of 899 biopsies and coincident clinical histories in 56 pediatric patients, comprising 314 patient-years of follow-up. Patients were classified as having symptoms or not based on a blinded review of their clinical status and echocardiograms. Biopsies were classified as negative or positive with established criteria. RESULTS: After biopsies performed less than 2 years after transplant or as a follow-up for a positive biopsy were excluded, 481 biopsies were available for analysis, of which 20 (4%) were positive. Positive biopsies were found in 15 (3%) of 456 biopsies in patients without symptoms compared with 5 (20%) of 25 biopsies in patients with symptoms. Patients with symptoms were 6 times more likely to have a positive biopsy compared with patients without symptoms. Of the positive rejection episodes, 75% occurred in patients without symptoms. CONCLUSION: Although rejection is uncommon in pediatric patients greater than 2 years after transplant, episodes of treatable allograft rejection can occur in the absence of clinical signs and symptoms. This study emphasizes the safety of and the need to continue to perform routine surveillance biopsies in patients without symptoms, even after the second post-transplant year.

Brachial artery reactivity: A modified technique with applicability to children.

Brachial artery reactivity noninvasively tests endothelial function. Cuff pressures of 180 to 300 mm Hg have been used. These pressures are ill advised in neonatal and premature infants. We therefore evaluated the use of substantially lower occlusive pressures. Fifteen adult subjects were enrolled. One arm was occluded to 200 mm Hg, and the other arm was occluded to 40 mm Hg above the resting systolic pressure. The occlusion time was 4.5 minutes. The brachial artery was measured at baseline and 1 minute after cuff deflation. Low pressure occlusions averaged 155.7 +/- 7.8 mm Hg versus 200 mm Hg for high pressure occlusions (P <.0001). One of 15 patients with low pressure occlusions reported discomfort versus 7 of 15 with high pressure occlusions (P <.05). Brachial artery reactivity increased by 8.0% +/- 2.5% with low pressure occlusions versus 7.5% +/- 2.7% with high pressure occlusions (P = not significant). Brachial artery reactivity can be assessed at lower occlusive pressures. This may extend the applicability of the technique to children and neonates.

QT dispersion predicts ventricular arrhythmia in pediatric cardiomyopathy patients referred for heart transplantation.

BACKGROUND: QT dispersion has been used in stratifying risk for sudden death in adults with dilated cardiomyopathy, but its role in the pediatric population has not been delineated. METHODS: We reviewed electrocardiograms in pediatric patients with dilated cardiomyopathy referred for heart transplantation, to evaluate the role of QT dispersion in predicting malignant arrhythmias in these patients. Three groups were defined: Group I (n = 13) had dilated cardiomyopathy and malignant ventricular arrhythmias, Group II (n = 13) had dilated cardiomyopathy with no ventricular arrhythmias and Group III (n = 30) consisted of normals. QT dispersion was defined as the duration of the shortest QT subtracted from that of the longest. In addition, the standard deviation of the QT intervals was calculated for each ECG, using 12 leads. RESULTS: QT dispersion was significantly prolonged in Group I (97 +/- 33 msec) compared to Group II (74 +/- 19 msec) and Group III (42 +/- 17 msec). QT standard deviation was also prolonged in Group I (30 +/- 11 msec) vs Group II (22 +/- 5 msec) and Group III (13 +/- 4 msec). Using a threshold value of 90 msec for QT dispersion or 25 msec for QT standard deviation, a sensitivity of 78% and a specificity of 70% was obtained for identifying patients who would subsequently develop ventricular arrhythmias. CONCLUSIONS: In pediatric heart transplant candidates with dilated cardiomyopathy, QT dispersion and QT standard deviation identify patients at higher risk for the development of malignant ventricular arrhythmia. This simple test can be helpful in the evaluation and management of these patients awaiting transplantation.

Arrhythmias and thromboembolic complications after the extracardiac Fontan operation.

BACKGROUND: Late morbidity and mortality after the Fontan operation are largely due to atrial arrhythmias, ventricular failure, and thrombus formation. The extracardiac Fontan procedure avoids extensive atrial manipulation and suture lines, theoretically minimizing the impetus for these events. We examined our experience with the extracardiac Fontan operation with particular attention to thromboembolism and arrhythmias. METHODS AND RESULTS: We retrospectively reviewed the medical and surgical records of all 16 patients who underwent an extracardiac Fontan operation between July 1993 and May 1996. Fifteen patients (94%) were in sinus rhythm before the operation. In the immediate postoperative period, seven (44%) had arrhythmias consisting of accelerated junctional rhythm and ectopic atrial rhythm. No associated hemodynamic compromise and no early deaths occurred. Patients were followed up for 3 to 34 months after the Fontan operation. Arrhythmias were detected in eight patients (50%) on surface electrocardiograms, and seven (44%) showed evidence of sinus node dysfunction on 24-hour Holter monitor studies. Thrombi were found in three patients (19%). All patients were asymptomatic, with no evidence of conduit obstruction by echocardiogram. CONCLUSIONS: The incidence of hemodynamically significant tachyarrhythmias appears to be reduced after the extracardiac Fontan operation. A significant percentage of patients have evidence of sinus node dysfunction, suggesting the presence of other surgical or nonsurgical factors responsible for this finding. Our incidence of thrombotic events is similar to previous reports with other Fontan modifications. It appears to be a reasonable option to maintain these patients on anticoagulation indefinitely.

ORK1, a potassium-selective leak channel with two pore domains cloned from Drosophila melanogaster by expression in Saccharomyces cerevisiae.

A K+ channel gene has been cloned from Drosophila melanogaster by complementation in Saccharomyces cerevisiae cells defective for K+ uptake. Naturally expressed in the neuromuscular tissues of adult flies, this gene confers K+ transport capacity on yeast cells when heterologously expressed. In Xenopus laevis oocytes, expression yields an ungated K(+)-selective current whose attributes resemble the "leak" conductance thought to mediate the resting potential of vertebrate myelinated neurons but whose molecular nature has long remained elusive. The predicted protein has two pore (P) domains and four membrane-spanning helices and is a member of a newly recognized K+ channel family. Expression of the channel in flies and yeast cells makes feasible studies of structure and in vivo function using genetic approaches that are not possible in higher animals.

Thromboembolic complications after Fontan operations.

BACKGROUND: Despite the increasing recognition of thromboembolic complications of the Fontan procedure, data characterizing such events are limited. The total cavopulmonary connection is believed to be less prone to this complication than other modifications of Fontan operations. We examined our experience with thromboembolism after Fontan operations to better characterize these events and their relation to the type of Fontan operation performed. METHODS AND RESULTS: We retrospectively identified 70 patients who underwent a Fontan operation between January 1978 and March 1994. Patients were divided into three groups: (1) total cavopulmonary connection, (2) atriopulmonary connection, and (3) conduit interposition. Fourteen patients (20%) developed a thromboembolic complication during a mean (+/- SD) follow-up of 5.2 +/- 4.7 years. The rate of thrombosis was similar in each group. The time from Fontan operation to thrombosis averaged 6.1 +/- 5.0 years. The overall rate of thromboembolic events was 3.9 per 100 patient-years. Twelve of the 14 thrombi were located within the venous circulation, 1 was in the left ventricle, and the location of 1 was undetermined. Six of the patients (43%) were asymptomatic, 3 (21%) presented with cerebrovascular events, and 5 (36%) presented with other symptoms. Thromboembolic events occurred from the perioperative period to 15 years after surgery. CONCLUSIONS: Thromboembolic complications occur frequently after the Fontan operation and its modifications and are a cause of significant morbidity. The time of presentation varies greatly. The rate of thrombosis appears to be similar in all modifications of the Fontan operation.