Passive performance evaluation and validation of a viscous impeller pump for subpulmonary fontan circulatory support

Patients with single ventricle defects undergoing the Fontan procedure eventually face Fontan failure. Long-term cavopulmonary assist devices using rotary pump technologies are currently being developed as a subpulmonary power source to prevent and treat Fontan failure. Low hydraulic resistance is a critical safety requirement in the event of pump failure (0 RPM) as a modest 2 mmHg cavopulmonary pressure drop can compromise patient hemodynamics. The goal of this study is therefore to assess the passive performance of a viscous impeller pump (VIP) we are developing for Fontan patients, and validate flow simulations against in-vitro data. Two different blade heights (1.09 mm vs 1.62 mm) and a blank housing model were tested using a mock circulatory loop (MCL) with cardiac output ranging from 3 to 11 L/min. Three-dimensional flow simulations were performed and compared against MCL data. In-silico and MCL results demonstrated a pressure drop of < 2 mmHg at a cardiac output of 7 L/min for both blade heights. There was good agreement between simulation and MCL results for pressure loss (mean difference - 0.23 mmHg 95% CI [0.24-0.71]). Compared to the blank housing model, low wall shear stress area and oscillatory shear index on the pump surface were low, and mean washout times were within 2 s. This study demonstrated the low resistance characteristic of current VIP designs in the failed condition that results in clinically acceptable minimal pressure loss without increased washout time as compared to a blank housing model under normal cardiac output in Fontan patients.

An in-vitro evaluation of the flow haemodynamic performance of Gore-Tex extracardiac conduits for univentricular circulation

OBJECTIVE(S)

The Fontan procedure is a common palliative intervention for sufferers of single ventricle congenital heart defects that results in an anastomosis of the venous return to the pulmonary arteries called the total cavopulmonary connection (TCPC). In patients with palliated single ventricular heart defects, the Fontan circulation passively directs systemic venous return to the pulmonary circulation in the absence of a functional sub-pulmonary ventricle. Therefore, the Fontan circulation is highly dependent on favourable flow and energetics, and minimal energy loss is of great importance. The majority of in vitro studies, to date, employ a rigid TCPC model. Recently, few studies have incorporated flexible TCPC models, without the inclusion of commercially available conduits used in these surgical scenarios.

METHOD

The methodology set out in this study successfully utilizes patient-specific phantoms along with the corresponding flowrate waveforms to characterise the flow haemodynamic performance of extracardiac Gore-Tex conduits. This was achieved by comparing a rigid and flexible TCPC models against a flexible model with an integrated Gore-Tex conduit.

RESULTS

The flexible model with the integrated Gore-Tex graft exhibited greater levels of energy losses when compared to the rigid walled model. With this, the flow fields showed greater levels of turbulence in the complaint and Gore-Tex models compared to the rigid model under ultrasound analysis.

CONCLUSION

This study shows that vessel compliance along with the incorporation of Gore-Tex extracardiac conduits have significant impact on the flow haemodynamics in a patient-specific surgical scenario.

Single ventricle: repair of atrioventricular valve using the bridging technique

Atrioventricular valve regurgitation is one of the predictors of adverse outcomes after the Fontan procedure. We describe our surgical technique of GoreTex (W. L. Gore & Associates, Inc., Flagstaff, AZ, USA) bridge to repair a common atrioventricular valve in single-ventricular circulation. The repair includes a GoreTex strip that is secured to the mid-line of both superior and inferior bridging leaflets and annulus to obtain a better coaptation of the leaflets and prevent further dilatation of the annulus. We have applied this technique for 7 consecutive patients with excellent outcomes.

Peristaltic hemodynamics of a new pediatric circulatory assist system for Fontan circulation using shape memory alloy fibers

Fontan procedure is one of the common surgical treatments of congenital heart diseases. Patients with Fontan circulation have single ventricle in the systemic circulation with the total cavopulmonary connection. We have been developing a pulmonary circulatory assist device using shape memory alloy fibers for Fontan circulation with total cavopulmonary connection. It consisted of the shape memory alloy fibers, the diameter of which are 100 µm. The fibers could wrap the ePTFE conduit for Fontan TCPC connection from the outside. We designed the sequential motion control system for sophisticated pulmonary hemodynamics by the pulsatile flow generation. In order to achieve pulsatile flow assistance in pulmonary arterial system, we fabricated a mechanical structure by sequential contraction of shape memory alloy fibers. Then, we developed a sequential contraction controller for the assist system, which could reproduce the wall contractile velocity at 6.0 to 20.0 cm/sec. We examined hemodynamic characteristic of its function using a mock circulatory system, which consisted of two overflow tanks representing venous and pulmonary arterial pressures in Fontan circulation. As a result, the pulmonary circulation assist device with sequential contraction could achieve effective promotion of the pulsatility in pulmonary arterial flow.

Simulating hemodynamics of the Fontan Y-graft based on patient-specific in vivo connections

BACKGROUND

Using a bifurcated Y-graft as the Fontan baffle is hypothesized to streamline and improve flow dynamics through the total cavopulmonary connection (TCPC). This study conducted numerical simulations to evaluate this hypothesis using postoperative data from 5 patients.

METHODS

Patients were imaged with cardiac magnetic resonance or computed tomography after receiving a bifurcated aorto-iliac Y-graft as their Fontan conduit. Numerical simulations were performed using in vivo flow rates, as well as 2 levels of simulated exercise. Two TCPC models were virtually created for each patient to serve as the basis for hemodynamic comparison. Comparative metrics included connection flow resistance and inferior vena caval flow distribution.

RESULTS

Results demonstrate good hemodynamic outcomes for the Y-graft options. The consistency of inferior vena caval flow distribution was improved over TCPC controls, whereas the connection resistances were generally no different from the TCPC values, except for 1 case in which there was a marked improvement under both resting and exercise conditions. Examination of the connection hemodynamics as they relate to surgical Y-graft implementation identified critical strategies and modifications that are needed to potentially realize the theoretical efficiency of such bifurcated connection designs.

CONCLUSIONS

Five consecutive patients received a Y-graft connection to complete their Fontan procedure with positive hemodynamic results. Refining the surgical technique for implementation should result in further energetic improvements that may help improve long-term outcomes.

Predictive modeling of the virtual Hemi-Fontan operation for second stage single ventricle palliation: two patient-specific cases

Single ventricle hearts are congenital cardiovascular defects in which the heart has only one functional pumping chamber. The treatment for these conditions typically requires a three-staged operative process where Stage 1 is typically achieved by a shunt between the systemic and pulmonary arteries, and Stage 2 by connecting the superior venous return to the pulmonary circulation. Surgically, the Stage 2 circulation can be achieved through a procedure called the Hemi-Fontan, which reconstructs the right atrium and pulmonary artery to allow for an enlarged confluence with the superior vena cava. Based on pre-operative data obtained from two patients prior to Stage 2 surgery, we developed two patient-specific multi-scale computational models, each including the 3D geometrical model of the surgical junction constructed from magnetic resonance imaging, and a closed-loop systemic lumped-parameter network derived from clinical measurements. "Virtual" Hemi-Fontan surgery was performed on the 3D model with guidance from clinical surgeons, and a corresponding multi-scale simulation predicts the patient's post-operative hemodynamic and physiologic conditions. For each patient, a post-operative active scenario with an increase in the heart rate (HR) and a decrease in the pulmonary and systemic vascular resistance (PVR and SVR) was also performed. Results between the baseline and this "active" state were compared to evaluate the hemodynamic and physiologic implications of changing conditions. Simulation results revealed a characteristic swirling vortex in the Hemi-Fontan in both patients, with flow hugging the wall along the SVC to Hemi-Fontan confluence. One patient model had higher levels of swirling, recirculation, and flow stagnation. However, in both models, the power loss within the surgical junction was less than 13% of the total power loss in the pulmonary circulation, and less than 2% of the total ventricular power. This implies little impact of the surgical junction geometry on the SVC pressure, cardiac output, and other systemic parameters. In contrast, varying HR, PVR, and SVR led to significant changes in theses clinically relevant global parameters. Adopting a work-flow of customized virtual planning of the Hemi-Fontan procedure with patient-specific data, this study demonstrates the ability of multi-scale modeling to reproduce patient specific flow conditions under differing physiological states. Results demonstrate that the same operation performed in two different patients can lead to different hemodynamic characteristics, and that modeling can be used to uncover physiologic changes associated with different clinical conditions.

Massive air embolism in a Fontan patient

Most institutions performing cardiopulmonary bypass for congenital heart disease patients use an integrated hard shell cardiotomy and venous reservoir attached to an oxygenator. It is of paramount importance that the integrated reservoir be vented so as not to cause pressurization. A pressurized sealed cardiotomy has been reported to occur secondary to issues with vacuum assisted venous drainage systems as well as improper venting in general. We report a case of air embolus caused by retrograde propulsion of air through the venous line secondary to a pressurized cardiotomy reservoir in a patient with Fontan circulation. The mechanism of cardiotomy pressurization is described, and the scenario simulated in a mock circuit.

Structural design of a newly developed pediatric circulatory assist device for Fontan circulation by using shape memory alloy fiber

Total cavopulmonary connection (TCPC) is commonly applied for the surgical treatment of congenital heart disease such as single ventricle in pediatric patients. Patients with no ventricle in pulmonary circulation are treated along with Fontan algorithm, in which the systemic venous return is diverted directly to the pulmonary artery without passing through subpulmonary ventricle. In order to promote the pulmonary circulation after Fontan procedure, we developed a newly designed pulmonary circulatory assist device by using shape memory alloy fibers. We developed a pulmonary circulatory assist device as a non-blood contacting mechanical support system in pediatric patients with TCPC. The device has been designed to be installed like a cuff around the ePTFE TCPC conduit, which can contract from outside. We employed a covalent type functional anisotropic shape memory alloy fiber (Biometal, Toki Corporation, Tokyo Japan) as a servo actuator of the pulmonary circulatory assist device. The diameter of this fiber was 100 microns, and its contractile frequency was 2-3 Hz. Heat generation with electric current contracts these fibers and the conduit. The maximum contraction ratio of this fiber is about 7% in length. In order to extend its contractile ratio, we fabricated and installed mechanical structural units to control the length of fibers. In this study, we examined basic contractile functions of the device in the mock system. As a result, the internal pressure of the conduit increased to 63 mmHg by the mechanical contraction under the condition of 400 msec-current supply in the mock examination with the overflow tank of 10 mmHg loading.

Cavopulmonary assist for the univentricular Fontan circulation: von Kármán viscous impeller pump

OBJECTIVE

In a univentricular Fontan circulation, modest augmentation of existing cavopulmonary pressure head (2-5 mm Hg) would reduce systemic venous pressure, increase ventricular filling, and thus substantially improve circulatory status. An ideal means of providing mechanical cavopulmonary support does not exist. We hypothesized that a viscous impeller pump, based on the von Kármán viscous pump principle, is optimal for this role.

METHODS

A 3-dimensional computational model of the total cavopulmonary connection was created. The impeller was represented as a smooth 2-sided conical actuator disk with rotation in the vena caval axis. Flow was modeled under 3 conditions: (1) passive flow with no disc; (2) passive flow with a nonrotating disk, and (3) induced flow with disc rotation (0-5K rpm). Flow patterns and hydraulic performance were examined for each case. Hydraulic performance for a vaned impeller was assessed by measuring pressure increase and induced flow over 0 to 7K rpm in a laboratory mock loop.

RESULTS

A nonrotating actuator disc stabilized cavopulmonary flow, reducing power loss by 88%. Disk rotation (from baseline dynamic flow of 4.4 L/min) resulted in a pressure increase of 0.03 mm Hg. A further increase in pressure of 5 to 20 mm Hg and 0 to 5 L/min flow was obtained with a vaned impeller at 0 to 7K rpm in a laboratory mock loop.

CONCLUSIONS

A single viscous impeller pump stabilizes and augments cavopulmonary flow in 4 directions, in the desired pressure range, without venous pathway obstruction. A viscous impeller pump applies to the existing staged protocol as a temporary bridge-to-recovery or -transplant in established univentricular Fontan circulations and may enable compressed palliation of single ventricle without the need for intermediary surgical staging or use of a systemic-to-pulmonary arterial shunt.

Transcatheter closure of extracardiac fontan fenestration in a cyanotic patient

Fontan operation is the connection of the systemic venous return to the pulmonary arteries, performed in patients with single ventricle physiology. The Fontan circuit is commonly fenestrated because of early postoperative risks such as high systemic venous pressure and low cardiac output. As it causes progressive cyanosis and increased risk of paradoxical embolism in the follow-up period, occlusion of these fenestrations is generally suggested. Successful closure of extracardiac Fontan fenestration with atrial septal occluder in a 10-year-old girl is reported herein. To our knowledge, this is the first such report from Turkey.

Evaluation of a novel Y-shaped extracardiac Fontan baffle using computational fluid dynamics

OBJECTIVES

The objective of this work is to evaluate the hemodynamic performance of a new Y-graft modification of the extracardiac conduit Fontan operation. The performance of the Y-graft design is compared to two designs used in current practice: a t-junction connection of the venae cavae and an offset between the inferior and superior venae cavae.

METHODS

The proposed design replaces the current tube grafts used to connect the inferior vena cava to the pulmonary arteries with a Y-shaped graft. Y-graft hemodynamics were evaluated at rest and during exercise with a patient-specific model from magnetic resonance imaging data together with computational fluid dynamics. Four clinically motivated performance measures were examined: Fontan pressures, energy efficiency, inferior vena cava flow distribution, and wall shear stress. Two variants of the Y-graft were evaluated: an "off-the-shelf" graft with 9-mm branches and an "area-preserving" graft with 12-mm branches.

RESULTS

Energy efficiency of the 12-mm Y-graft was higher than all other models at rest and during exercise, and the reduction in efficiency from rest to exercise was improved by 38%. Both Y-graft designs reduced superior vena cava pressures during exercise by as much as 5 mm Hg. The Y-graft more equally distributed the inferior vena cava flow to both lungs, whereas the offset design skewed 70% of the flow to the left lung. The 12-mm graft resulted in slightly larger regions of low wall shear stress than other models; however, minimum shear stress values were similar.

CONCLUSIONS

The area-preserving 12-mm Y-graft is a promising modification of the Fontan procedure that should be clinically evaluated. Further work is needed to correlate our performance metrics with clinical outcomes, including exercise intolerance, incidence of protein-losing enteropathy, and thrombus formation.

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.

Midterm follow-up of the status of Gore-Tex graft after extracardiac conduit Fontan procedure☆

OBJECTIVE

Extracardiac conduit Fontan procedure has some theoretical advantages over other types of Fontan procedures, such as optimized flow dynamics, a lower frequency of arrhythmias, and technical ease of procedure. However, lack of growth potential and thrombogenicity of the artificial conduit is the main concern and can possibly lead to reoperation for the conduit stenosis. In this study, we investigated the change and the status of the Gore-Tex graft used in extracardiac conduit Fontan procedure.

METHODS

Between 1996 and 2005, 154 patients underwent extracardiac conduit Fontan procedure using Gore-Tex graft. Among these, 46 patients underwent cardiac catheterization during follow-up period. We measured the internal diameter of the conduit and inferior vena cava angiographically.

RESULTS

Mean follow-up duration was 36.1+/-19.7 months. The conduit diameter used was 16 mm in 10 patients, 18 mm in 16, 20 mm in 14, 22 mm in 4, and 24 mm in 2 patients. The mean conduit-to-inferior vena cava cross-sectional area ratio was 1.25+/-0.33. According to the conduit size used, this ratio was 1.03+/-0.17 for 16 mm conduits, 1.33+/-0.37 for 18 mm, 1.33+/-0.36 for 20 mm, 1.28+/-0.26 for 22 mm, and 1.05+/-0.06 for 24 mm conduits (p<0.05, 16 mm vs 18 mm and 20 mm). The mean percent decrease of the conduit cross-sectional area was 14.3+/-8.5%, and this did not differ significantly according to the conduit size (p=0.82). Follow-up duration and the percent decrease of the conduit cross-sectional area did not show significant correlation (r=0.22, p=0.14). There was no reoperation due to conduit stenosis.

CONCLUSIONS

During midterm follow-up of about 3 years, the conduit cross-sectional area decreased by 14%, and this did not differ according to the conduit size used. The extent of decrease of the conduit cross-sectional area remained stable irrespective of the follow-up duration. Sixteen millimeters conduit showed no evidence of clinically significant stenosis, but careful follow-up is warranted because of the possible conduit stenosis relative to the patients' somatic growth.

Transcatheter closure of fenestration with detachable coils after the Fontan operation

We report our experience in 13 patients who underwent transcatheter closure of Fontan fenestration with the Cook detachable coils. These patients underwent the extracardiac type Fontan operation with a short conduit fenestration (n=7) or lateral tunnel type with a punch-hole fenestration (n=6). Fenestration closure was done at the mean age of 5.1+/-2.4 yr, average of 32 months after the Fontan operation. We used one to three coils depending on the fenestration type, size, and residual shunt. Aortic oxygen saturations increased by an average of 5.4 (2-9)% and mean pressures in the Fontan circuit increased by an average of 2.1 (0-6) mmHg. During follow-up (median of 23 months), five patients (4 in extracardiac, 1 in lateral tunnel) had complete occlusion of the fenestration on echocardiography. There was no immediate or late complication. Transcatheter closure of fenestration in Fontan operation using the Cook detachable coil is a safe and feasible technique. However, the coil was ineffective for closure of a punch-hole fenestration in the lateral tunnel type operation. In the conduit type fenestration, some modification of fenestration method instead of a short conduit for coil closure or use of new device is necessary to increase complete closure rate.

Combined DOR ventriculoplasty and aortic valve replacement in the treatment of post infarction ventricular aneurysm and aortic regurgitation

There has been only one other case of endoventricular circular patch plasty performed in conjunction with aortic valve replacement reported in the literature. We present the unique case of a patient suffering from congestive heart failure due to both post-infarct aortic regurgitation and ventricular aneurysm along with his successful surgical treatment.

Valveless pump models that laid a false but fortuitous trail on the way towards the total cavopulmonary connection

When Fontan and Baudet devised what has become known as the Fontan operation, they understandably assumed that inflow and outflow valves should be included to achieve a pump-like action of the subpulmonary right atrial cavity. Over the following years, however, it became apparent that valves did not function satisfactorily in this situation. Worse, the implanted valves had a tendency to become obstructive, which often lead to critical elevation of the already raised systemic venous pressure. Surgeons gradually realised that the outcomes of surgery designed to create the Fontan circulation were likely to be better without inclusion of valves in the subpulmonary right atrium, and they stopped putting them in.

Anesthetic Care During Modified Fontan Procedure Without Cardiopulmonary Bypass

OBJECTIVE

The purpose of this study was to report the anesthetic care of patients during performance of a Fontan procedure without cardiopulmonary bypass (CPB).

DESIGN

Retrospective chart review.

SETTING

Operating room of a university hospital.

PARTICIPANTS

Seven pediatric-patients undergoing inferior vena cava (IVC)-to-pulmonary artery (PA) anastomosis for completion of the Fontan procedure.

INTERVENTIONS

Charts were reviewed for anesthetic technique, hemodynamic and ventilatory changes occurring during the procedure, and anesthetic interventions that were provided.

MEASUREMENTS AND MAIN RESULTS

The off-bypass Fontan procedure was attempted in 7 patients (age: 26 months-7 years, weight: 13 to 28 kg). Exposure of the PA was not feasible in 1 patient because of a markedly enlarged right atrium. In the remaining 6 patients, before cross-clamping of the PA to allow for the proximal anastomosis between the PA and the conduit, alkalosis (pH > or =7.5) was maintained by the administration of sodium bicarbonate. After PA cross-clamping, fluid administration was necessary in 5 patients and dopamine (3-7 microg/kg/min) was necessary in 4 patients. The minute ventilation was increased by 18 +/- 7% to maintain baseline PaCO2 values. Before the placement of the PA cross-clamp, the end-tidal PaCO2 difference was 7 +/- 4 mmHg and the transcutaneous (TC)-PaCO2 difference was 3 +/- 2 mmHg. The end-tidal PaCO2 difference increased to 14 +/- 6 mmHg during cross-clamping of the PA, whereas no change was noted in the TC-PaCO2 difference. Once the proximal anastomosis was completed, a bridge was placed to redirect blood from the IVC to the right atrium while the IVC was clamped and attached to the distal end of the conduit. After placement of the distal end of the bridge into the IVC, fluid administration to maintain the blood pressure was necessary in 3 patients. In 1 patient, 20 minutes after placement of the bridge, the authors noted a progressive increase in the central venous pressure reading measured from the left femoral vein and the need for the administration of volume to maintain the mean arterial pressure. Examination of the bridge revealed occlusion with thrombus despite an activated coagulation time value of 250 to 300 seconds. The tracheas of 3 of the 6 patients were extubated in the operating room, whereas the other 3 were extubated in the pediatric intensive care unit within 4 hours of completion of the procedure. The 1 patient who required the use of CPB required reintubation and had a protracted intensive care unit course. The other 6 patients were discharged home on postoperative days 7 to 12.

CONCLUSIONS

With alteration of the anesthetic technique, the Fontan procedure can be performed in selected patients without the need for CPB.

[Closure of extrocardiac Fontan fenestration by using the Amplatzer duct occluder]

INTRODUCTION

A direct or tubular communication between the systemic venous system and the systemic atrium, generally called fenestration, is surgically created to improve the postoperative period of patients undergoing total cavopulmonary connection. However, a fenestration prompts a potentially deleterious right to left shunt, and is generally closed after the postoperative period. Direct fenestrations can be closed using coils, or devices designed for atrial septal defect closure. However, no devices have been designed for closure of extracardiac fenestrations. We report our experience concerning the closure of extracardiac Fontan fenestration by the Amplatzer duct occluder (ADO).

METHODS

From January 2001 to December 2002, we closed extracardiac Fontan fenestrations using the ADO device in 10 consecutive patients. Indications to fenestration closure were: low velocity shunt through the fenestration, mild desaturation, and absence of effusions.

RESULTS

All patients had a successful closure of the fenestration. The procedure was performed through the femoral vein in 7 cases and through the right jugular vein in 3. Mean central venous pressure increased not significantly from 12 to 13-mmHg. Mean oxygen saturation increased significantly from 90 to 97% (p<0.001). Immediate shut abolition was obtained in 9 cases. No complications were observed. At a median follow-up of 12 months (range 6-18 months), all patients are free of symptoms and have a normal oxygen saturation at rest as well as at exertion.

CONCLUSION

The ADO device allowed closing the extracardiac Fontan fenestration in all patients with no mortality, no morbidity and a rate of 100% of complete closure at mid-term follow-up.

A novel implantation technique for closure of an atypical fenestration connecting the right atrial appendage to an extracardiac conduit by use of a 15 mm Helex device in a patient with total cavopulmonary connection

We report on a 7-years old patient after total cavopulmonary anastomosis with an extracardiac conduit. An atypical fenestration was created during the operation connecting the right atrial appendage to the extracardiac conduit. Because of arterial desaturation, the fenestration connecting the anterior wall of the extracardiac conduit to the posterior wall of the right atrial appendage was successfully occluded with a 15 mm Helex device by use of a modified implantation technique.

Clipped tube fenestration after extracardiac Fontan allows for simple transcatheter coil occlusion

BACKGROUND

Expensive devices are increasingly used to close a patent fenestration after a modified Fontan operation. We report our 5-year institutional experience of clipped tube fenestration after extracardiac Fontan operation, which allows for simple transcatheter coil occlusion.

METHODS

We retrospectively reviewed 30 children, median age of 4.0 years (range, 2.4 to 8.8 years) who underwent extracardiac Fontan operation between May 1996 and May 2001, and were fenestrated using a 4- to 8-mm diameter clipped tube graft.

RESULTS

Ten children had a patent fenestration occluded by transcatheter placement of 15 detachable coils (5- to 8-mm diameter). Aortic oxygen saturations increased on average by 5.5% (2% to 14%) and mean pressures in the Fontan circuit by 2.5 mm Hg (0 to 3 mm Hg). Four had immediate complete occlusion angiographically and 6 had trivial residual shunt, but complete occlusion by echocardiography at follow-up. There have been no immediate complications, late coil embolizations, thromboembolic events, or documented hemolysis within a follow-up after coil implantation of 1.7 years (0.4 to 4.5 years). Spontaneous fenestration closure was documented in 8 patients at cardiac catheterization and 9 patients by echocardiography with consistent improvement in resting transcutaneous oxygen saturation. Two children with a patent fenestration have been considered inappropriate for closure, and there was one early surgical death. There have been no complications related to the tube fenestration modification within a follow-up postoperation of 2.6 years (0.1 to 5.5 years).

CONCLUSIONS

Clipped tube fenestration after extracardiac Fontan operation is a useful surgical modification that allows for simple transcatheter coil occlusion.

Depopulated vena caval homograft: a new venous conduit

OBJECTIVE

Completion of the Fontan procedure is frequently performed by using an extracardiac conduit between the inferior vena cava and the pulmonary artery. Most centers use a polytetrafluoroethylene graft for the extracardiac conduit, and because re-endothelialization is unlikely, anticoagulation is used for a variable period. This study explores the use of an alternate large-caliber venous conduit.

METHODS

The superior vena cava was replaced in 8 minipigs with either a polytetrafluoroethylene interposition graft (2 pigs) or a depopulated (acellular), cryopreserved superior vena caval homograft (6 pigs). After 6 months, the animals were killed, and the grafts were examined for patency and histology, including immunostaining. No anticoagulation was used.

RESULTS

Polytetrafluoroethylene grafts have a cross-sectional luminal narrowing, ranging from 16% to 40%. Histology showed only partial intimal ingrowth, with excessive subendothelial fibrosis and early calcification. In contrast, the depopulated venous homografts showed minimal luminal narrowing, ranging from 2% to 9%. These grafts were completely repopulated by the recipient with an endothelial lining, which stained positively for factor VIII, and a subendothelial region appropriately recellularized by myofibroblasts, which stained positively for smooth muscle actin and procollagen. There was no evidence of an immune response to the venous homografts, as judged by staining for T-cell surface antigen, CD4, and CD8. Thrombus was not seen in any of the grafts.

CONCLUSION

Depopulated, cryopreserved vena caval homografts might be superior conduits for cavopulmonary connection during completion of the Fontan operation by using the extracardiac conduit technique.

Management of coronary artery fistulae. Patient selection and results of transcatheter closure

OBJECTIVES

We report short-term findings in 33 patients after transcatheter closure (TCC) of coronary artery fistulae (CAF) and compare our results with those reported in the recent transcatheter and surgical literature.

BACKGROUND

Transcatheter closure of CAF has been advocated as a minimally invasive alternative to surgery.

METHODS

We reviewed all patients presenting with significant CAF between January 1988 and August 2000. Those with additional complex cardiac disease requiring surgical management were excluded.

RESULTS

Of 39 patients considered for TCC, occlusion devices were placed in 33 patients (85%) at 35 procedures and included coils in 28, umbrella devices in 6 and a Grifka vascular occlusion device in 1. Post-deployment angiograms demonstrated complete occlusion in 19, trace in 11, or small residual flow in 5. Follow-up echocardiograms (median, 2.8 years) in 27 patients showed no flow in 22 or small residual flow in 5. Of the 6 patients without follow-up imaging, immediate post-deployment angiograms showed complete occlusion in 5 or small residual flow in 1. Thus, complete occlusion was accomplished in 27 patients (82%). Early complications included transient ST-T wave changes in 5, transient arrhythmias in 4 and single instances of distal coronary artery spasm, fistula dissection and unretrieved coil embolization. There were no deaths or long-term morbidity. Device placement was not attempted in 6 patients (15%), because of multiple fistula drainage sites in 4, extreme vessel tortuosity in 1 and an intracardiac hemangioma in 1.

CONCLUSIONS

A comparison of our results with those in the recent transcatheter and surgical literature shows similar early effectiveness, morbidity and mortality. From data available, TCC of CAF is an acceptable alternative to surgery in most patients.

Closure of the fenestration in the extracardiac Fontan with the Amplatzer duct occluder device

We report the successful use of the Amplatzer duct occluder for the delayed closure of the fenestration in three patients who underwent an extracardiac modified Fontan procedure. At the moment of closure, the patients were 5.5, 2.7, and 3 years old (29 months, 3 months, and 14 months after the Fontan procedure, respectively). Immediate full occlusion was achieved in all cases. In addition, arterial saturation increased significantly (> 5%) with no hemodynamic deterioration. There were no complications during or after the procedure, and the patients were discharged in good conditions the day after and with uneventful follow-up. In conclusion, the Amplatzer duct is safe and effective for the closure of the fenestration in the extracardiac Fontan. Cathet Cardiovasc Intervent 2001;54:88-92.

Transcatheter closure of fenestrations and excluded hepatic veins after fontan: versatility of the Amplatzer device

BACKGROUND

The aim of this study was to evaluate the Amplatzer septal occluder (ASO) for transcatheter closure of fenestrations and excluded hepatic veins in patients after modified Fontan operations. Residual right-to-left shunts have improved surgical results of the Fontan operation. Shunt closure may eventually be desirable to eliminate hypoxemia and reduce risk of embolic complications.

METHODS AND RESULTS

Ten patients with hypoxemia caused by residual shunts after Fontan procedures were evaluated for closure. After favorable results of test occlusion, all shunts were closed with the use of the ASO. Eight ASOs were used to close fenestrations in 7 patients with 6F transvenous sheaths. Three ASOs were used to close excluded hepatic veins in 3 patients with 6F venous sheaths and transbaffle punctures. Fluoroscopy and transesophageal echocardiography were used to guide device placement. Device placement in all patients was successful. All shunts were closed by angiography after device placement. While breathing room air, systemic oxygen saturation rose from 87.9% +/- 3.0% to 96.3% +/- 0. 9% (P <.001) in the patients. There were no complications of the implant procedures and none noted in outpatient follow-up.

CONCLUSIONS

This experience suggests that the ASO is safe and effective for closing surgical shunts after Fontan procedures. The ASO design allows closure of excluded hepatic veins and has advantages over other devices in closure of fenestrations.

Right atrioventricular extracardiac conduit as a fontan modification: late results

BACKGROUND

The right ventricle, when incorporated in the Fontan circulation, might enlarge and function as a pump to the pulmonary circulation. Experience has shown that over the long-term, this operation can be associated with major difficulties.

METHODS

The late results, (13+/-6 years) after right atrioventricular connection as a Fontan modification, were reviewed in 14 patients with tricuspid atresia (11), ventricular septal-defect with small right ventricle (2), and double inlet left ventricle (1) to assess the long-term survival, the right ventricular size, and the need and timing of reoperations. Operations used a valved conduit (7), a valveless Dacron (E.L. Bard, Haverhill, PA) tube (5) and a direct right atrium-right ventricle anastomosis (2).

RESULTS

Death occurred in 5 by 8+/-5 years. Conduit obstruction occurred in 10 by 9+/-3 years equally in patients with valved (6 of 7) compared to patients with valveless conduits (4 of 5) and irrespective of right ventricular size (3 of 4 with enlarged right ventricle versus 4 of 6 with small ventricle). Patients with direct atrioventricular anastomosis had no obstruction. Reoperation was performed in 9 but failed to relieve the obstruction in 4 because of external compression (4) with or without thrombosis (1).

CONCLUSIONS

Right atrioventricular connection as a Fontan modification can provide good early palliation, but is a poor long-term solution, as it is associated with a high incidence and difficulties in relieving the obstruction.

Occlusion of Fontan fenestrations using the Amplatzer septal occluder

OBJECTIVE

To evaluate the efficacy and safety of the Amplatzer septal occluder device for occlusion of Fontan fenestrations.

SUBJECTS

Five children aged 5-10 years who had undergone a fenestrated Fontan operation.

SETTING

Tertiary paediatric cardiology centre.

METHODS

Each patient had right and left heart catheterisation to assess haemodynamic suitability for fenestration closure. Sizing of the defect was achieved with a balloon wedge catheter and transoesphageal echocardiography. Transcatheter occlusion of the fenestration was accomplished using a 4 mm device in three patients, and 5 mm or 9 mm devices in the other two patients. Residual shunting following occlusion was assessed using angiography and echocardiography.

RESULTS

100% occlusion rate of the fenestration was achieved in all patients. No complications or device failures were seen during the three month follow up period.

CONCLUSION

The Amplatzer septal occluder device is safe, and effectively occludes the Fontan fenestration.

Intermediate results of the extracardiac Fontan procedure

BACKGROUND

Fourteen children (ages 2 to 14 years) and 1 adult (32 years) have undergone a modification of the Fontan procedure in which an extracardiac lateral tunnel or conduit is used in combination with staged or simultaneous bidirectional Glenn shunt(s).

METHODS

Extracardiac lateral tunnels (n = 9) were constructed using a polytetrafluoroethylene patch (n = 7), pericardial patch (n = 1), or in situ pericardial flap (n = 1). Extracardiac lateral conduits (n = 6) were constructed using nonvalved homografts (n = 2) or polytetrafluoroethylene tube grafts (n = 4). Fenestrations were created in 4 patients (2 each in extracardiac lateral tunnel and extracardiac lateral conduit patients). Aortic cross-clamping was completely avoided in 12/15 patients (aortic cross-clamping in 2 patients for atrial septal defect enlargement and 1 for Damus-Kaye-Stansel procedure).

RESULTS

There have been no operative deaths. Prolonged postoperative chest tube drainage (> 2 weeks) has been rare (n = 1). At follow-up (range, 6 to 54 months; mean, 27.5 months), all patients are in New York Heart Association class I or II and remain in normal sinus rhythm. Late protein-losing enteropathy was seen in 1 patient and was successfully treated by percutaneous creation of a stented fenestration from the extracardiac tunnel to the systemic atrium. Late catheterizations reveal unobstructed extracardiac lateral tunnel function and low pulmonary pressures (range, 11 to 13 mm Hg). Advantages of the extracardiac Fontan include (1) avoidance of aortic cross-clamping in most patients, (2) the hemodynamic benefits of total cavopulmonary connection, (3) avoidance of atriotomy and intraatrial suture lines, (4) preservation of sinus rhythm and no arrhythmias at 2 year follow-up, (5) drainage of the coronary sinus to low pressure atrium, (6) allowance for early/late fenestrations, (7) prevention of baffle leaks and intraatrial obstruction, and (8) allowance for growth (tunnel procedures only).

CONCLUSIONS

We recommend this extracardiac procedure for all suitable patients undergoing surgical conversion to the Fontan circulation.

Transcatheter coil occlusion of surgical fenestration after Fontan operation

BACKGROUND

Fenestration of the Fontan circulation that results in a residual right-to-left shunt has improved operative survival rates among high-risk patients. Late closure of the fenestration by use of a transcatheter umbrella device has achieved separation of the systemic and pulmonary venous circulations, "completing" the Fontan pathway. Because use of umbrella devices is restricted, many institutions continue to perform only nonfenestrated Fontan procedures.

METHODS AND RESULTS

Five children 3.5 to 8.3 years old (mean, 5.1 years) underwent cardiac catheterization 0.5 to 24 months (mean, 10 months) after operation for the purpose of occluding a persistently patent Fontan fenestration. Once candidacy was determined, an 8-mm x 10-cm Gianturco coil was delivered to straddle the fenestration with established techniques for coil occlusion of patent ductus arteriosus. Complete occlusion occurred in 4 of 5 patients, in 2 of the 4 before they left the catheterization laboratory. One patient had a residual angiographic shunt but had complete closure within 24 hours by echocardiography. In 1 patient who had a residual shunt at 24 hours, the fenestration was completely closed at 1 month after coil placement. One patient had residual shunting at 2 months but saturations have increased 15% to 17% since coil placement. No embolizations (early or late), clinical hemolysis, thromboembolic events, or hemodynamic deterioration occurred among patients during 1- to 14-month follow-up periods.

CONCLUSIONS

A persistently patent fenestration after Fontan operation may be closed with a Gianturco coil. This universally available alternative to umbrella devices may make the fenestrated Fontan a more appealing option to centers that had not previously considered its use.

Modified Fontan procedure for left atrial isomerism: alternative technique

Anomalous systemic or pulmonary venous connections increase the risk and technical difficulty of the modified Fontan procedure. This report describes an alternative technique of total diversion of systemic venous return to the pulmonary artery in a child with left atrial isomerism, incorporating an extracardiac conduit between the hepatic veins and the right pulmonary artery.