Acute effects of embolizing systemic-to-pulmonary arterial collaterals on blood flow in patients with superior cavopulmonary connections: a pilot study

Contemporary Management of the Failing Fontan

Adult patients with congenital heart disease have now surpassed the pediatric population due to advances in surgery and improved survival. One such complex congenital heart disease seen in adult patients is the Fontan circulation. These patients have complex physiology and are at risk for several complications, including thrombosis of the Fontan pathway, pulmonary vascular disease, heart failure, atrial arrhythmias, atrioventricular valve regurgitation, and protein-losing enteropathy. This review discusses the commonly encountered phenotypes of Fontan circulatory failure and their contemporary management.

Relationship of Aortopulmonary Collaterals and Pulmonary Artery Development During Staged Single Ventricle Reconstruction

To evaluate the relationship of aortopulmonary collaterals and the development of central pulmonary arteries during staged palliation. A total of 287 patients, who underwent staged palliation with bidirectional cavopulmonary shunt and total cavopulmonary connection between 2008 and 2019, had available angiography. Pulmonary artery index was calculated using pulmonary angiography as described by Nakata and colleagues. Aortopulmonary collaterals were observed in 47 (16%) patients at stage II palliation, in 131 (46%) at total cavopulmonary connection, and afterwards in 49 (7%). The interventional closure of aortopulmonary collaterals was performed before stage II in 12 (4%) patients, before Fontan completion in 38 (13%), and afterwards in 39 (14%). Presence of aortopulmonary collaterals before stage II was not associated with the pulmonary artery index (129 vs. 150 mm2/m2, p = 0.176) at stage II. In contrast, aortopulmonary collaterals before the Fontan completion were associated with lower pulmonary artery index (154 vs. 172 mm2/m2, p = 0.005), and right pulmonary artery index (99 vs. 106 mm2/m2, p = 0.006). Patients who underwent interventional closure of aortopulmonary collaterals before total cavopulmonary connection had lower pulmonary artery index (141 vs. 169 mm2/m2, p < 0.001), lower right pulmonary artery index (93 vs. 106 mm2/m2, p = 0.007), and left pulmonary artery index (54 vs. 60 mm2/m2, p = 0.013) at Fontan completion. The presence of aortopulmonary collaterals did not influence pulmonary artery size by the time of stage II. However, presence of aortopulmonary collaterals was associated with under-developed pulmonary arteries at Fontan completion, especially in patients who needed interventional closure of aortopulmonary collaterals.

Impact of aortopulmonary collaterals on adverse events after total cavopulmonary connection

OBJECTIVES

Effects of aortopulmonary collaterals (APCs) on outcomes after the total cavopulmonary connection (TCPC) are unclear. This study evaluated the incidence of APCs before and after TCPC and analysed the impacts of APCs on adverse outcomes.

METHODS

A total of 585 patients, who underwent TCPC from 1994 to 2020 and whose preoperative angiographies were available, were included. Pre-TCPC angiograms in all patients were used for the detection of APCs, and post-TCPC angiograms were evaluated in selected patients. Late adverse events included late death, protein-losing enteropathy (PLE) and plastic bronchitis (PB).

RESULTS

The median age at TCPC was 2.3 (1.8-3.4) years with a body weight of 12 (11-14) kg. APCs were found in 210 patients (36%) before TCPC and in 81 (14%) after TCPC. The closure of APCs was performed in 59 patients (10%) before TCPC, in 25 (4.2%) at TCPC and in 59 (10%) after TCPC. The occurrences of APCs before and after TCPC were not associated with short-term or mid-term mortality. The APCs before TCPC were associated with chylothorax (P = 0.025), prolonged chest tube duration (P = 0.021) and PB (P = 0.008). The APCs after TCPC were associated with PLE (P < 0.001) and PB (P < 0.001). With APCs following TCPC, freedom from PLE and PB was lower than without (P < 0.001, P < 0.001).

CONCLUSIONS

APCs before TCPC were associated with chylothorax, prolonged chest tube duration and PB. APCs after TCPC were associated with both PLE and PB. The presence of APCs might affect the lymph drainage system and increase the incidence of chylothorax, PLE and PB.

Cerebral Blood Flow, Brain Injury, and Aortic-Pulmonary Collateral Flow After the Fontan Operation

Patients with a single ventricle develop aortopulmonary collaterals (APCs) whose flow has been shown to be inversely proportional to cerebral blood flow (CBF) in a previous cross-sectional study. Longitudinal CBF and APC flow in patients with Fontan physiology adjusting for brain injury (BI) has never been reported. Decreased CBF and BI may adversely impact neurodevelopment. A prospective longitudinal cohort of 27 patients with Fontan physiology (aged 10 ± 1.9 years, 74% male) underwent cardiac and brain magnetic resonance imaging 3 to 9 months and 6.0 ± 1.86 years after Fontan operation to measure the CBF and APC flow and to reassess the BI (focal BI, generalized insult, and hemorrhage). CBF was measured using jugular venous flow and APC flow was measured by the difference between aortic flow and caval return. Multivariate modeling was used to assess the relation between the change in APC flow and BI. A strong inverse relation was found between CBF/aortic flow change and APC flow/aortic flow and APC flow/body surface area change (R2 = 0.70 and 0.72 respectively, p <0.02). Overall, the CBF decreased by 9 ± 11% and the APC flow decreased by 0.73 ± 0.67 l/min/m2. The evolution of CBF and APC flow were significantly and inversely related when adjusting for time since Fontan operation, gender, and BI on the multivariate modeling. Every unit increase in APC flow change was associated with an 8% decrease in CBF change. In conclusion, CBF and APC flow change are inversely related across serial imaging, adjusting for time from Fontan operation, gender, and BI. CBF and APC aortic flow decrease over a 6-year period. This may adversely impact neurodevelopment. Because APCs can be embolized, this may be a modifiable risk factor. Clinical trials numbers: NCT02135081 and NCT02919956.

Quantification of systemic-to-pulmonary collateral flow in univentricular physiology with 4D flow MRI

PURPOSE

Systemic-to-pulmonary collateral flow is a well-recognised phenomenon in patients with single ventricle physiology, but remains difficult to quantify. The aim was to compare the reported formula's that have been used for calculation of systemic-to-pulmonary-collateral flow to assess their consistency and to quantify systemic-to-pulmonary collateral flow in patients with a Glenn and/or Fontan circulation using four-dimensional flow MRI (4D flow MR).

METHODS

Retrospective case-control study of Glenn and Fontan patients who had a 4D flow MR study. Flows were measured at the ascending aorta, left and right pulmonary arteries, left and right pulmonary veins, and both caval veins. Systemic-to-pulmonary collateral flow was calculated using two formulas: 1) pulmonary veins - pulmonary arteries and 2) ascending aorta - caval veins. Anatomical identification of collaterals was performed using the 4D MR image set.

RESULTS

Fourteen patients (n = 11 Fontan, n = 3 Glenn) were included (age 26 [22-30] years). Systemic-to-pulmonary collateral flow was significantly higher in the patients than the controls (n = 10, age 31.2 [15.1-38.4] years) with both formulas: 0.28 [0.09-0.5] versus 0.04 [-0.66-0.21] l/min/m2 (p = 0.036, formula 1) and 0.67 [0.24-0.88] versus -0.07 [-0.16-0.08] l/min/m2 (p < 0.001, formula 2). In patients, systemic-to-pulmonary collateral flow differed significantly between formulas 1 and 2 (13% versus 26% of aortic flow, p = 0.038). In seven patients, veno-venous collaterals were detected and no aortopulmonary collaterals were visualised.

CONCLUSION

4D flow MR is able to detect increased systemic-to-pulmonary collateral flow and visualise collaterals vessels in Glenn and Fontan patients. However, the amount of systemic-to-pulmonary collateral flow varies with the formula employed. Therefore, further research is necessary before it could be applied in clinical care.

Impact of Anatomical Sub-types and Shunt Types on Aortopulmonary Collaterals in Hypoplastic Left Heart Syndrome

This study aims to clarify the relation of development of aortopulmonary collateral arteries (APCs) with anatomical sub-types and the shunt types at Norwood procedure in patients with hypoplastic left heart syndrome (HLHS). A total of 140 patients with HLHS who completed 3 staged palliation between 2003 and 2019 were included. Incidence of APCs and corresponding interventions were examined using angiogram by cardiac catheterization, with respect to the anatomical sub-types and shunt types. Totally, APCs were observed in 87 (62%) of the patients; pre-stage II in 32 (23%), pre-stage III in 64 (46%), and after stage III in 40 (29%). The incidence of APCs before stage II was significantly higher in patients with aortic atresia/mitral atresia (AA/MA) compared with other sub-types (P = 0.022). Patients with right ventricle to pulmonary artery conduit (RVPAC) had a higher incidence of APCs originating from the descending aorta, compared with those with modified Blalock-Taussig shunt (20% vs 2%, P= 0.002). Interventions for APCs were performed in 58 (41%) patients; before stage II in 10 (7%), after stage II in 7 (5%), before stage III in 22 (16%), and after stage III in 32 (23%). Patients with AA/MA had more interventions before stage II (P= 0.019), and patients with aortic stenosis/mitral stenosis (AS/MS) had a lower incidence of interventions after stage III (P= 0.047). More than half of the patients with HLHS developed APCs. Before stage II, patients with AA/MA sub-type had a higher incidence of APCs, and those with RVPAC had significantly more APCs from the descending aorta.

Society for Cardiovascular Magnetic Resonance/European Society of Cardiovascular Imaging/American Society of Echocardiography/Society for Pediatric Radiology/North American Society for Cardiovascular Imaging Guidelines for the use of cardiovascular magnetic resonance in pediatric congenital and acquired heart disease : Endorsed by The American Heart Association

Cardiovascular magnetic resonance (CMR) has been utilized in the management and care of pediatric patients for nearly 40 years. It has evolved to become an invaluable tool in the assessment of the littlest of hearts for diagnosis, pre-interventional management and follow-up care. Although mentioned in a number of consensus and guidelines documents, an up-to-date, large, stand-alone guidance work for the use of CMR in pediatric congenital 36 and acquired 35 heart disease endorsed by numerous Societies involved in the care of these children is lacking. This guidelines document outlines the use of CMR in this patient population for a significant number of heart lesions in this age group and although admittedly, is not an exhaustive treatment, it does deal with an expansive list of many common clinical issues encountered in daily practice.

Society for Cardiovascular Magnetic Resonance/European Society of Cardiovascular Imaging/American Society of Echocardiography/Society for Pediatric Radiology/North American Society for Cardiovascular Imaging Guidelines for the Use of Cardiac Magnetic Resonance in Pediatric Congenital and Acquired Heart Disease: Endorsed by The American Heart Association

Cardiovascular magnetic resonance has been utilized in the management and care of pediatric patients for nearly 40 years. It has evolved to become an invaluable tool in the assessment of the littlest of hearts for diagnosis, pre-interventional management and follow-up care. Although mentioned in a number of consensus and guidelines documents, an up-to-date, large, stand-alone guidance work for the use of cardiovascular magnetic resonance in pediatric congenital 36 and acquired 35 heart disease endorsed by numerous Societies involved in the care of these children is lacking. This guidelines document outlines the use of cardiovascular magnetic resonance in this patient population for a significant number of heart lesions in this age group and although admittedly, is not an exhaustive treatment, it does deal with an expansive list of many common clinical issues encountered in daily practice.

Aortopulmonary Collaterals in Single Ventricle Physiology: Variation in Understanding Occlusion Practice Among Interventional Cardiologists

Although aortopulmonary collaterals (APCs) frequently develop in patients with single ventricle palliation, there is a lack of understanding of pathophysiology, natural history, and outcomes with no universal guidelines for management and interventional practice. We conducted a study to assess the views held by interventional congenital cardiologists regarding the hemodynamic impact of APCs in patients with single ventricle palliation, and their embolization practice. An electronic survey using the Pediatric Interventional Cardiology Symposium (PICS) mailing list was conducted between February and March 2019 with one reminder sent 2 weeks after initial invitation for participation. Of the 142 interventional cardiologist respondents, 95 (66.9%) reside in North America and 47 (33.1%) worldwide. We elected to exclude the data from interventionalists outside North America in this analysis as it was not representative of worldwide practice. Hypoxemia was considered to be the most common trigger for development of APCs by 56 (58.9%) respondents. After completion of total cavopulmonary connection, 30 (31.6%) respondents reported the APC burden stays the same while 31 (32.6%) feel it decreases. In evaluating the burden of APC flow, only 4 (4.2%) reported measuring oxygen saturation at different pulmonary artery segments, 21 (22.1%) perform segmental aortic angiograms, and 18 (19%) perform selective bilateral subclavian artery angiograms. A majority of respondents, 71 (74.7%), occlude the feeder vessel at different locations, while 10 (10.5%) occlude only the origin of the vessel. Our study demonstrates significant variation in the understanding of the cause and prognosis of APCs in patients with single ventricle palliation. Furthermore, there is variation in the approach for diagnosis and management among interventional cardiologists. Further studies are required to improve understanding of APCs and develop universal management guidelines.

Transplantation of the failing Fontan

Half a century has passed since the original Fontan palliation. In the interim, surgical and medical advancements have allowed more single ventricle patients to reach Fontan and long-term survival for Fontan patients to improve significantly. However, the risk for Fontan failure and need for heart transplantation remains. In this article we discuss mechanisms of Fontan failure, risk factors and special considerations for Fontan patients in both medical and surgical management around heart transplantation and provide an updated review of survival for Fontan patients after heart transplantation.

Determination of the Frequency of Right and Left Internal Mammary Artery Embolization in Single Ventricle Patients: A Two-Center Study

Embolization of systemic to pulmonary artery collaterals to regulate pulmonary arterial flow or pressure of the cavopulmonary circulation in patients with single ventricle is a common practice. The relative incidence and impact of this practice on future interventions like coronary artery bypass grafting is poorly understood. This study aims to evaluate the frequency and implications of internal mammary artery (IMA) embolization in the single ventricle (SV) population. A retrospective chart review was performed of SV patients who underwent cardiac catheterization before and after Fontan procedure between February 2007 and 2017. Data were collected from two tertiary care centers in the Midwest. Of the 304 SV patients, 62 (20.4%) underwent embolization of one or more IMAs, whereas 242 (79.6%) did not. The rate of embolization of IMA was 40.5% in one center and 14.5% in the second center. Among patients who received IMA embolization, left internal mammary artery (LIMA) embolization was seen in 6 (9.7%) patients. Majority of patients underwent either right internal mammary artery (RIMA) embolization (n = 25; 40.3%) or RIMA and LIMA embolization (n = 27; 43.5%). IMA embolization in SV patients is common. Embolizing IMAs early in life will likely eliminate a valuable graft option for coronary artery bypass grafting should it be required in the future care of these patients. Multi-center, prospective, nation-wide studies are warranted to examine coronary artery disease in the SV population and true frequency of IMA embolization. Delineation of which IMAs were embolized is a necessary in surgical and cardiac intervention national data, such as Society of Thoracic Surgeons (STS) database. All measures should be taken to preserve IMAs patency, if deemed feasible and safe.

Routine Cardiac Catheterization Prior to Fontan Operation: Is It a Necessity?

Prior to the Fontan procedure, patients with single ventricle physiology with Glenn shunt are typically referred for cardiac catheterization to assess hemodynamics and potentially provide interventional measures. Currently, echocardiography provides detailed information which together with other non-invasive imaging such as CT scan and MRI may obviate the need for routine cardiac catheterization prior to the Fontan procedure. In this study, we examine the findings in cardiac catheterization in this population to determine: (a) the accuracy of echocardiography in providing adequate information prior to the Fontan procedure, particularly in identifying those in need of per-catheter intervention, and (b) the percentage of patients requiring interventional procedures during cardiac catheterization. We performed a retrospective chart review of echocardiographic and cardiac catheterization data for patients who underwent pre-Fontan cardiac catheterization at our center in the period from 02/01/2008 to 02/28/2017. We aimed to re-examine the necessity of routine cardiac catheterization in all single ventricle patients. This was performed through examining pre-catheterization echocardiography reports and comparing them to findings of the subsequent cardiac catheterization reports. Echocardiography reports were evaluated for accuracy in identifying significant anatomical or hemodynamic findings, which may impact success of Fontan procedure as well as the ability of echocardiography to predict findings important to know prior to the Fontan procedure. In this cohort of 40 children, 3 patients were found to have significant hemodynamic findings through cardiac catheterization which were not previously known by echocardiography. In addition, 28 out of 40 patients (70%) required interventional procedures to address significant abnormalities (systemic to pulmonary arterial collaterals, pulmonary artery stenosis, aortic arch stenosis, etc.). All cases of aortic arch stenosis were detected by echocardiography, however, all patients who required systemic to pulmonary arterial or left SVC embolization were not detected by echocardiography. Furthermore, echocardiography did not detect the need for branch pulmonary artery stenosis in 50% of cases. Cardiac catheterization appears to be an essential part of patient assessment prior to Fontan completion in patients with single ventricle physiology. This current practice may change in the future if a non-invasive screening tool is found to have high positive and negative predictive values in identifying the subset of patients who require potential intervention in pre-Fontan cardiac catheterization.

Durable Benefit of Particle Occlusion of Systemic to Pulmonary Collaterals in Select Patients After Superior Cavopulmonary Connection

Systemic to pulmonary arterial collaterals (SPC) are commonly found in patients undergoing staged operative palliation for single ventricle heart disease. Occlusion of SPC as part of pre-Fontan catheterization has been shown to improve hemodynamics acutely. Anecdotally, the effect of this intervention appears to be transient, and to our knowledge there is no data supporting its durability in these patients. Between 1/1/2016 and 5/1/2017, 24 children underwent Glenn operations at our institution. Of these, 3 patients had signs and symptoms deteriorating clinical status suggestive of volume overload in the period between their Glenn operation and Fontan completion, prompting heart catheterization. SPC were occluded with a combination of polyvinyl alcohol embolization particles, and in some cases coils or vascular plugs. Clinical course and data from echocardiograms and serial catheterizations are presented. SPC occlusion was performed over 6 procedures in 3 subjects with technical success in each case. Hemodynamic evaluation was repeated in 2/3 patients with improvement in collateral burden and hemodynamics in both cases. One patient previously thought to be unsuitable for Fontan completion improved sufficiently to undergo late Fontan completion, which was ultimately successful. In all patients, there was improvement in clinical status. In patients with severe SPC collateral durable benefit was seen, suggesting that in certain cases intervention on SPC remote from Fontan completion may have clinical benefit.

Can the Pulmonary Artery Wedge Pressure be Used Reliably as a Surrogate for the Left Atrial Mean Pressure in Pre-Fontan Evaluation?

The correlation between mean pulmonary artery wedge pressure (PAWP) and left atrial mean pressure (LAMP) has been poorly studied in patients with single ventricle (SV) physiology (Bernstein et al. in Pediatr Cardiol 33: 15-20 2012). The aim of this study is to determine if the PAWP can be used safely as a surrogate to the LAMP to calculate the pulmonary vascular resistance (PVR) during the pre-Fontan evaluation. Also, we aimed to understand if the presence of significant systemic-to-pulmonary collaterals (SPCs) is a confounding factor for accurate estimation of the LAMP. From February 2007 to February 2017, forty-one patients were eligible for inclusion in the study. These patients were varied in terms of underlying cardiac malformation. Sex distribution was equal with 20 males and 21 females. Median weight was 11.8 kg, median body surface area was 0.51 m², median age at catheterization was 2 years, and the median age at Glenn surgery was 5 months. We found the left and right PAWP and LAMP correlated strongly and the differences in the measurements were negligible. Similar findings were observed when calculating PVRs using PAWP and LAMP. These findings were more pronounced in the absence of significant SPCs. PAWP and LAMP correlation was still valid in the presence of significant SPCs; however, the correlation among the calculated PVRs was more attenuated.

Simulation of aortopulmonary collateral flow in Fontan patients for use in prediction of interventional outcomes

PURPOSE

Patients with complex congenital heart disease may need to be converted to a Fontan circulation with systemic venous return surgically connected to the pulmonary circulation. These patients frequently form aortopulmonary collaterals (APC), that is arterial inflows to the pulmonary artery vascular tree. The aim of this study was to develop a method to calculate the effect of APC on the pulmonary flow distribution based on magnetic resonance imaging (MRI) measurements and computational fluid dynamics simulations in order to enable prediction of interventional outcomes in Fontan patients.

METHODS

Patient-specific models of 11 patients were constructed in a 3D-design software based on MRI segmentations. APC flow was quantified as the difference between pulmonary venous flow and pulmonary artery flow, measured by MRI. A method was developed to include the modulating effect of the APC flow by calculating the patient-specific relative pulmonary vascular resistance. Simulations, including interventions with a Y-graft replacement and a stent dilatation, were validated against MRI results.

RESULTS

The bias between simulated and MRI-measured fraction of blood to the left lung was 2·9 ± 5·3%. Including the effects of the APC flow in the simulation (n = 6) reduced simulation error from 9·8 ± 7·0% to 5·2 ± 6·3%. Preliminary findings in two patients show that the effect of surgical and catheter interventions could be predicted using the demonstrated methods.

CONCLUSIONS

The work demonstrates a novel method to include APC flow in predictive simulations of Fontan hemodynamics. APC flow was found to have a significant contribution to the pulmonary flow distribution in Fontan patients.

Life-threatening airway bleeding after palliation of single ventricle congenital heart disease

Objective

To describe acute and mid-term outcomes following presentation with, and treatment for, life-threatening airway bleeding (hemoptysis) in palliated single ventricle congenital heart disease (SV-CHD).

Methods

Case series of patients with SV-CHD who presented to a large congenital heart centre with hemoptysis between 2004 and 2015.

Results

Twenty-one episodes of hemoptysis occurred in 12 patients (58% female, median 10.5 (IQR 7.2, 16.4) years). First hemoptysis episode occurred after Fontan completion (n=8), after superior cavopulmonary anastomosis (SCPA, n=3) and in one shunt-dependent patient. Bronchoscopy was performed in conjunction with catheterisation in 14/21 (67%) initial catheterisations. A specific anatomic source of airway bleeding was identified in 95% of bronchoscopy cases and was uniformly distributed in all lobar segments. Transcatheter intervention with systemic-to-pulmonary collateral artery (SPC) occlusion was performed in 28/30 catheterisations. Apart from increased airway bleeding during interventional bronchoscopy (37%), there were no procedural complications. Median hospital length of stay was 9.0 (3.5, 14.5) days with patients undergoing 1.0 (1.0,2.0) catheterisations per episode of hemoptysis. Two SCPA patients did not survive to discharge. During a median follow-up of 32.5 (12.5, 87.5) months, freedom from mortality was 75%, with all three deaths occurring in the SCPA group by 4 months posthemoptysis. Recurrent hemoptysis occurred in 60% of patients.

Conclusions

Despite the potentially life-threatening nature of hemoptysis in patients with SV-CHD, a policy of bronchoscopic evaluation and transcatheter treatment is safe and may contribute to low mortality at mid-term follow-up in Fontan patients. Hemoptysis in SCPA patients may portend a poor prognosis. Recurrent hemoptysis is common.

Effective Cardiac Index and Systemic-Pulmonary Collaterals Evaluated by Cardiac Magnetic Resonance Late After Fontan Palliation

The regulation of cardiac output in the Fontan circuit is not completely understood. Systemic-pulmonary collaterals (SPCs) are frequent in patients with univentricular heart, and their clinical significance and management remain controversial. The aims of our study were to identify factors associated with SPCs' flow at late follow-up after Fontan and evaluate the relation between SPCs flow (QSPCs) and the effective cardiac index (CI). From our cardiac magnetic resonance database, we identified all Fontan patients with a complete set of flow measurements allowing calculation of QSPCs and effective CI. QSPCs was calculated as (left pulmonary veins flow + right pulmonary veins flow) - (right pulmonary artery flow + left pulmonary artery flow). Effective CI was calculated as (Aortic flow (QAo) - QSPCs)/BSA. Medical, surgical history, and clinical status were recorded. Sixty-four post-Fontan patients (36 male; mean age 19 ± 10 years) were included in the study. Median QSPCs was 0.7 L/min/m² (interquartile [IQ] range 0.386-0.983) accounting for a median of 21% (IQ range 13-28) of aortic flow. The effective CI in our population was 2.4 ± 0.6 L/min/m². QSPCs inversely correlate with left pulmonary artery area (r = -0.37, p = 0.004) and total antegrade pulmonary flow (r = -0.32, p = 0.01). QSPCs correlate with indexed aortic flow (r = 0.6, p <0.001) and inversely correlate with effective CI (r = -0.39, p = 0.002). Effective CI inversely correlates with age at study and age at the Fontan palliation (r = -0.35, p = 0.005, and r = -0.29, p = 0.02, respectively) and positively with ventricular ejection fraction (r = 0.3, p = 0.01). In conclusion, SPCs are common in Fontan patients, correlate inversely with effective CI, and are associated with a reduced antegrade pulmonary flow. In cardiac magnetic resonance evaluation of post-Fontan patients, effective CI should be taken into account rather than the total CI.

Frequency of Mammary Artery Coiling in Single-Ventricle Patients and Future Coronary Artery Grafting

Pre-Fontan coil closure of aorto-pulmonary collaterals decreases single-ventricle volume load and improves outcome. Coiling of right and left internal mammary arteries may present a challenge to cardiothoracic surgery teams caring for these patients when future coronary artery bypass grafting is needed for SV patients. The goal of this study was to determine the frequency of internal mammary artery coil closure in SV patients in a single tertiary care center. A retrospective review of all pediatric single-ventricle patients who underwent cardiac catheterization between March 2009 and October 2015 at Rush Center for Congenital Heart Disease was performed. Fifty-one patients' charts were reviewed. Twenty-five patients received coil closure of one or more internal mammary artery (coil group) and 26 received no coil closure (no-coil group). In the coil group, 21 (84 %) had their collateral vessels coiled in the pre-Fontan period and 4 (16 %) had their vessels coiled in the post-Fontan period. In the coil group, 18 (72 %) had their right internal mammary artery coiled and 7 (28 %) had both right and left internal mammary arteries coiled. None of the coil group had isolated coil closure of the left internal mammary artery. This study is the first to verify the frequency of right and/or left internal mammary artery coil closure in SV patients and the potential impact on future coronary artery bypass grafting. Extensive peri-Fontan coiling of the internal mammary arteries presents a significant potential challenge for subsequent management of SV patients as older adults.

Improved survival after heart transplant for failed Fontan patients with preserved ventricular function

BACKGROUND

Patients with a failing Fontan continue to have decreased survival after heart transplant (HT), particularly those with preserved ventricular function (PVF) compared with impaired ventricular function (IVF). In this study we evaluated the effect of institutional changes on post-HT outcomes.

METHODS

Data were retrospectively collected for all Fontan patients who underwent HT. Mode of failure was defined by the last echocardiogram before HT, with mild or no dysfunction considered PVF and moderate or severe considered IVF. Outcomes were compared between early era (EE, 1995 to 2008) and current era (CE, 2009 to 2014). Management changes in the CE included volume load reduction with aortopulmonary collateral (APC) embolization, advanced cardiothoracic imaging, higher goal donor/recipient weight ratio and aggressive monitoring for post-HT vasoplegia.

RESULTS

A total of 47 patients were included: 27 in the EE (13 PVF, 14 IVF) and 20 in the CE (12 PVF, 8 IVF). Groups were similar pre-HT, except for more PLE in PVF patients. More patients underwent APC embolization in the CE (80% vs 28%, p < 0.01). There was no difference in donor/recipient weight ratio between eras. There was a trend toward higher primary graft failure for PVF in the EE (77% vs 36%, p = 0.05) but not the CE (42% vs 75%, p = 0.20). Overall, 1-year survival improved in the CE (90%) from the EE (63%) (p = 0.05), mainly due to increased survival for PVF (82 vs 38%, p = 0.04).

CONCLUSIONS

Post-HT survival for failing Fontan patients has improved, particularly for PVF. In the CE, our Fontan patients had a 1-year post-HT survival similar to other indications.

Relationship of cerebral blood flow to aortic-to-pulmonary collateral/shunt flow in single ventricles

OBJECTIVE

Patients with single ventricle can develop aortic-to-pulmonary collaterals (APCs). Along with systemic-to-pulmonary artery shunts, these structures represent a direct pathway from systemic to pulmonary circulations, and may limit cerebral blood flow (CBF). This study investigated the relationship between CBF and APC flow on room air and in hypercarbia, which increases CBF in patients with single ventricle.

METHODS

106 consecutive patients with single ventricle underwent 118 cardiac magnetic resonance (CMR) scans in this cross-sectional study; 34 prior to bidirectional Glenn (BDG) (0.50±0.30 years old), 50 prior to Fontan (3.19±1.03 years old) and 34 3-9 months after Fontan (3.98±1.39 years old). Velocity mapping measured flows in the aorta, cavae and jugular veins. Analysis of variance (ANOVA) and multiple linear regression were used. Significance was p<0.05.

RESULTS

A strong inverse correlation was noted between CBF and APC/shunt both on room air and with hypercarbia whether CBF was indexed to aortic flow or body surface area, independent of age, cardiopulmonary bypass time, Po2 and Pco2 (R=-0.67--0.70 for all patients on room air, p<0.01 and R=-0.49--0.90 in hypercarbia, p<0.01). Correlations were not different between surgical stages. CBF was lower, and APCs/shunt flow was higher prior to BDG than in other stages.

CONCLUSIONS

There is a strong inverse relationship between CBF and APC/shunt flow in patients with single ventricle throughout surgical reconstruction on room air and in hypercarbia independent of other factors. We speculate that APC/shunt flow may have a negative impact on cerebral development and neurodevelopmental outcome. Interventions on APC may modify CBF, holding out the prospect for improving neurodevelopmental trajectory.

TRIAL REGISTRATION NUMBER

NCT02135081.

Aortopulmonary collateral flow is related to pulmonary artery size and affects ventricular dimensions in patients after the fontan procedure

BACKGROUND

Aortopulmonary collaterals (APCs) are frequently found in patients with a single-ventricle (SV) circulation. However, knowledge about the clinical significance of the systemic-to-pulmonary shunt flow in patients after the modified Fontan procedure and its potential causes is limited. Accordingly, the aim of our study was to detect and quantify APC flow using cardiovascular magnetic resonance (CMR) and assess its impact on SV volume and function as well as to evaluate the role of the size of the pulmonary arteries in regard to the development of APCs.

METHODS

60 patients (mean age 13.3 ± 6.8 years) after the Fontan procedure without patent tunnel fenestration underwent CMR as part of their routine clinical assessment that included ventricular functional analysis and flow measurements in the inferior vena cava (IVC), superior vena cava (SVC) and ascending aorta (Ao). APC flow was quantified using the systemic flow estimator: (Ao) - (IVC + SVC). Pulmonary artery index (Nakata index) was calculated as RPA + LPA area/body surface area using contrast enhanced MR angiography. The patient cohort was divided into two groups according to the median APC flow: group 1 < 0.495 l/min/m(2) and group 2 > 0.495 l/min/m(2).

RESULTS

Group 1 patients had significant smaller SV enddiastolic (71 ± 16 vs 87 ± 25 ml/m(2); p=0.004) and endsystolic volumes (29 ± 11 vs 40 ± 21 ml/m(2); p=0.02) whereas ejection fraction (59 ± 9 vs 56 ± 13%; p=0.38) differed not significantly. Interestingly, pulmonary artery size showed a significant inverse correlation with APC flow (r=-0.50, p=0.002).

CONCLUSIONS

Volume load due to APC flow in Fontan patients affected SV dimensions, but did not result in an impairment of SV function. APC flow was related to small pulmonary artery size, suggesting that small pulmonary arteries represent a potential stimulus for the development of APCs.

Accuracy of conventional oximetry for flow estimation in patients with superior cavopulmonary connection: a comparison with phase-contrast cardiac MRI

BACKGROUND

Cardiac catheterization is routinely used as a diagnostic tool in single ventricle patients with superior cavopulmonary connection. This physiology presents inherent challenges in applying the Fick principle to estimate flow. We sought to quantitatively define the error in oximetry-derived flow parameters using phase-contrast cardiac MRI (CMR) as a reference.

METHODS AND RESULTS

Thirty patients with superior cavopulmonary connection who underwent combined CMR and catheterization between July 2008 and June 2012 were retrospectively analyzed. Estimates of flow and resistance calculated using the Fick equation were compared with CMR measurements. Oximetry underestimated CMR-measured pulmonary blood flow (Qp) by an average of 1.1 L/min per m(2) or 32% of the CMR value (P<0.0001). Oximetry overestimated systemic blood flow (Qs) by an average of 0.5 L/min per m(2) or 15% of the CMR value (P=0.009). There was no correlation between the Qp:Qs ratio derived by Fick and that measured by CMR (ρ(c)=0.01). The error in the Fick Qp correlated moderately with the measured systemic-to-pulmonary arterial collateral flow (r=0.39). The median total oxygen consumption calculated using combined CMR and oximetry data was 173 mL/min per m(2), higher than the assumed values used to calculate flows by the Fick equation. The upper body circulation received on average 51% of systemic blood flow while conducting only 39% of total body metabolism.

CONCLUSIONS

Fick-derived estimates of flow are inherently unreliable in patients with superior cavopulmonary connections. Integrating flows measured by CMR and pressures measured by catheter will provide the best characterization of superior cavopulmonary connection physiology.