Extent of aortopulmonary collateral blood flow as a risk factor for Fontan operations

Norwood Operation with Right Ventricular-Pulmonary Artery Shunt Versus Comprehensive Stage II After Bilateral Pulmonary Artery Banding Palliation

As a strategy for the primary Norwood operation, the right ventricular-pulmonary artery shunt is associated with satisfactory early outcome. However, use of this shunt after bilateral pulmonary artery banding remains controversial. This study compared the operative outcomes and late hemodynamics in patients who underwent the Norwood operation, preceded by bilateral pulmonary artery banding, with a right ventricular-pulmonary artery shunt or with bidirectional Glenn anastomosis (comprehensive stage II strategy). We retrospectively reviewed 38 patients who underwent the Norwood operation preceded by bilateral pulmonary artery banding between 2004 and 2017. Of these, 17 underwent the Norwood operation with a right ventricular-pulmonary artery shunt (Group S), whereas 21 underwent the comprehensive stage II strategy (Group G). 5 years after the Norwood operation, 10 (60%) and 17 (81%) patients in Group S and Group G, respectively, underwent the Fontan procedure. Group S showed significantly lower pressure in the superior vena cava after bidirectional Glenn anastomosis than Group G (13 ± 2 mmHg vs. 18 ± 3 mmHg; p < 0.01), but pressures were similar after the Fontan procedure. The right ventricular end-diastolic volume at 1 year post-Fontan procedure was significantly higher in Group S than in Group G (142 ± 41% vs. 91 ± 28%; p < 0.01). In terms of early outcomes, the Norwood operation with a right ventricular-pulmonary artery shunt enabled low pressure in the superior vena cava, but in the long term, this shunt adversely influenced the right ventricular volume.

Comparison of definitive approaches for conotruncal defects following bidirectional Glenn procedure

BACKGROUND

Staged repair is common for complex conotruncal defects, often involving bidirectional Glenn (BDG) procedure. Following the cavopulmonary shunt, both Fontan completion and biventricular conversion (BiVC) serve as definitive approaches. The optimal strategy remains controversial.

METHODS

The baseline, perioperative and follow-up data were obtained for all paediatric patients with conotruncal defects who underwent BDG procedure as palliation in Fuwai Hospital from 2013 to 2022. Patients with single ventricle were excluded. The primary outcome was mortality. The secondary outcome was reintervention, including any cardiovascular surgeries and non-diagnostic catheterisations.

RESULTS

A total of 232 patients were included in the cohort, with 142 underwent Fontan (61.2%) and 90 underwent BiVC (38.8%). The median interstage period from BDG to the definitive procedure was 3.83 years (IQR: 2.72-5.42) in the overall cohort, 3.62 years (IQR: 2.57-5.15) in the Fontan group and 4.15 years (IQR: 3.05-6.13) in the BiVC group (p=0.03). The in-hospital outcomes favoured the Fontan group, including duration of cardiopulmonary bypass, aortic cross-clamp, mechanical ventilation and intensive care unit stay. Postoperative mortality was generally low and comparable, as was the reintervention rate (HR=1.42, 95% CI: 0.708 to 2.85, p=0.32). The left ventricular size was smaller at baseline and within the normal range at follow-up for both Fontan and BiVC groups; however, it was significantly larger with BiVC at follow-up.

CONCLUSION

In paediatric patients with conotruncal heart defects who underwent BDG procedure, BiVC is a feasible option, especially for patients with certain Fontan risk factors, and are not ideal candidates for successful Fontan completion.

Pre-Glenn aorto-pulmonary collaterals in single-ventricle patients

BACKGROUND

In single-ventricle patients undergoing staged-bidirectional Glenn, 36-59% have aorto-pulmonary collateral flow, but risk factors and clinical outcomes are unknown. We hypothesise that shunt type and catheter haemodynamics may predict pre-bidirectional Glenn aorto-pulmonary collateral burden, which may predict death/transplantation, pulmonary artery or aorto-pulmonary collateral intervention.

METHODS

Retrospective cohort study of patients undergoing a Norwood procedure for single-ventricle anatomy. Covariates included clinical and haemodynamic characteristics up to/including pre-bidirectional Glenn catheterisation and aorto-pulmonary collateral burden at pre-bidirectional Glenn catheterisation. Multivariable models used to evaluate relationships between risk factors and outcomes.

RESULTS

From January 2011 to March 2016, 104 patients underwent Norwood intervention. Male sex (odds ratio 3.36, 95% confidence interval 1.17-11.4), age at pre-bidirectional Glenn assessment (2.12, 1.33-3.39 per month), and pulmonary to systemic flow ratio (1.23, 1.08-1.41 per 0.1 unit) were associated with aorto-pulmonary collateral burden. Aorto-pulmonary collateral burden was not associated with death/transplantation (hazard ratio 1.19, 95% confidence interval 0.37-3.85), pulmonary artery (sub-hazard ratio 1.38, 0.32-2.61), or aorto-pulmonary collateral interventions (sub-hazard ratio 1.11, 0.21-5.76). Longer post-Norwood length of stay was associated with greater risk of death/transplantation (hazard ratio 1.22 per week, 95% confidence interval 1.08-1.38), but lower risk of aorto-pulmonary collateral intervention (sub-hazard ratio 0.86 per week, 95% confidence interval 0.75-0.98). Time to pre-bidirectional Glenn catheterisation was associated with lower risk of pulmonary artery (sub-hazard ratio 0.80 per month, 95% confidence interval 0.65-0.98) and aorto-pulmonary collateral intervention (sub-hazard ratio 0.79, 0.63-0.99). Probability of moderate/severe aorto-pulmonary collateral burden increased with left-to-right shunt (22.5% at <1.0, 57.6% at >1.4) and the age at pre-bidirectional Glenn catheterisation (10.6% at <2 months, 56.9% at >5 months).

CONCLUSIONS

Aorto-pulmonary collateral burden is common after Norwood procedure and increases as age at bidirectional Glenn increases. As expected, higher pulmonary to systemic flow ratio is a marker for greater aorto-pulmonary collateral burden pre-bi-directional Glenn; aorto-pulmonary collateral burden does not confer risk of death/transplantation or pulmonary artery intervention.

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.

Clinical Variables Associated with Pre-Fontan Aortopulmonary Collateral Burden

Aortopulmonary collaterals (APCs) develop universally, but to varying degrees, in patients with single ventricle congenital heart disease (CHD). Despite their ubiquitous presence, APCs remain poorly understood. We sought to evaluate the association between APC burden and common non-invasive clinical variables. We conducted a single center, retrospective study of patients with single ventricle CHD and previous Glenn palliation who underwent pre-Fontan cardiac magnetic resonance (CMR) imaging from 3/2018 to 3/2021. CMR was used to quantify APC flow, which was normalized to aortic (APC/QAo) and pulmonary vein (APC/QPV) blood flow. Univariate, multivariable, and classification and regression tree (CART) analyses were done to investigate the potential relationship between CMR-quantified APC burden and clinical variables. A total of 29 patients were included, all of whom had increased APC flow (APC/QAo: 26.9, [22.0, 39.1]%; APC/QPV: 39.4 [33.3, 46.9]%), but to varying degrees (APC/QAo: range 11.9-44.4%; APC/QPV: range 17.7-60.0%). Pulmonary artery size (Nakata index, at pre-Fontan CMR) was the only variable associated with APC flow on multivariable analysis (APC/QAo: p = 0.020, R2 = 0.19; APC/QPV: p = 0.0006, R2 = 0.36) and was the most important variable associated with APC burden identified by CART analysis (size inversely related to APC flow). APC flow is universally increased but highly variable in patients with single ventricle CHD and Glenn circulation. Small branch pulmonary artery size is a key factor associated with increased APC burden; however, the pathogenesis of APCs is likely multifactorial. Further research is needed to better understand APC pathogenesis, including predisposing and mitigating factors.

Pulmonary Vascular Sequelae of Palliated Single Ventricle Circulation: Arteriovenous Malformations and Aortopulmonary Collaterals

Children and adults with single ventricle congenital heart disease (CHD) develop many sequelae during staged surgical palliation. Universal pulmonary vascular sequelae in this patient population include two inter-related but distinct complications: pulmonary arteriovenous malformations (PAVMs) and aortopulmonary collaterals (APCs). This review highlights what is known and unknown about these vascular sequelae focusing on diagnostic testing, pathophysiology, and areas in need of further research.

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.

Aortopulmonary collateral flow quantification by MR at rest and during continuous submaximal exercise in patients with total cavopulmonary connection

BACKGROUND

Aortopulmonary collateral flow is considered to have significant impact on the outcome of patients with single ventricle circulation and total cavopulmonary connection (TCPC). There is little information on collateral flow during exercise.

PURPOSE

To quantify aortopulmonary collateral flow at rest and during continuous submaximal exercise in clinical patients doing well with TCPC.

STUDY TYPE

Prospective, case controlled.

POPULATION

Thirteen patients with TCPC (17 (11-37) years) and 13 age and sex-matched healthy controls (18 (11-38) years).

FIELD STRENGTH

1.5T; free breathing; phase sensitive gradient echo sequence.

ASSESSMENT

Blood flow in the ascending and descending aorta and superior vena cava were measured at rest and during continuous submaximal physical exercise in patients and controls. Systemic blood flow (Q_s ) was assumed to be represented by the sum of flow in the superior caval vein (Q_svc ) and the descending aorta (Q_AoD ) at the diaphragm level. Aortopulmonary collateral flow (Q_coll ) was calculated by subtracting Q_s from flow in the ascending aorta (Q_AoA ).

STATISTICS

Mann-Whitney U-test and Wilcoxon test for comparison between groups and between rest and exercise.

RESULTS

Absolute collateral flow in TCPC patients at rest was 0.4 l/min/m² (-0.1-1.2), corresponding to 14% (-2-42) of Q_s . Collateral flow did not change during exercise (difference -0.01 (-0.7-1.0) l/min/m² , P = 0.97). TCPC patients had significantly lower Q_s at rest (2.5 (1.6-4.1) vs. 3.5 (2.6-4.8) l/min/m² , P = 0.001) and during submaximal exercise (3.2 (2.0-6.0) vs. 4.8 (3.3-6.9) l/min/m² , P = 0.001), compared to healthy controls. The increase in Q_s with exercise was also significantly lower in patients than in healthy controls (median 0.6 vs. 1.2 l/min/m² , P < 0.02).

DATA CONCLUSION

Clinical patients doing well with TCPC have significant aortopulmonary collateral flow at rest (14% of Q_s ) compared to healthy controls, which does not change during submaximal exercise.

LEVEL OF EVIDENCE

2 Technical Efficacy: Stage 3 J. Magn. Reson. Imaging 2018;47:1509-1516.

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.

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.

Long-term follow-up of Fontan completion in adults and adolescents

BACKGROUND

The Fontan procedure is rarely performed in adults and adolescents in the present era. We review our results with the Fontan procedure in adolescents and young adults.

METHODS

Between 1974 and 2010, 79 consecutive patients underwent the Fontan procedure at an age ≥ 15 years (mean age at Fontan operation, 20.3 years ± 4.5 years). Forty-five patients underwent atriopulmonary connection, 11 underwent the Bjork procedure, and 23 underwent total cavopulmonary connection.

RESULTS

Ten hospital deaths (HDs) and/or early Fontan takedowns (TDs) occurred. The median follow-up period was 18.2 years (range, 0.6-37.6 years). The estimated freedom from death or TD rates was 79.7% at 5 years, 77.0% at 10 years, 73.9% at 15 years, and 63.9% at 20 years. Age was not a predictor of HD and/or TD. Freedom from death or TD after 1998 was 69.1% at 5 years, 69.1% at 10 years, and 69.1% at 15 years, and before 1997 was 82.3% at 5 years, 79.0% at 10 years, 75.5% at 15 years, and 65.1% at 20 years; there were no significant differences between the two groups. In 19 late-death patients, nine (47.4%) experienced sudden death. Among these patients, five had known arrhythmias before sudden death.

CONCLUSIONS

In patients who were ≥15 years old, the surgical results of the Fontan operation were acceptable. Approximately half of the late deaths were sudden deaths, mainly occurring 10-20 years postoperatively.

The Medtronic Micro Vascular Plug™ for Vascular Embolization in Children With Congenital Heart Diseases

OBJECTIVES

To describe the early multi-center, clinical experience with the Medtronic Micro Vascular Plug™ (MVP) in children with congenital heart disease (CHD) undergoing vascular embolization.

BACKGROUND

The MVP is a large diameter vascular occlusion device that can be delivered through a microcatheter for embolization of abnormal blood vessels.

METHODS

A retrospective review of embolization procedures using the MVP in children with CHD was performed in 3-centers. Occlusion of patent ductus arteriosus using the MVP was not included.

RESULTS

Ten children underwent attempted occlusion using the MVP. The most common indication to use the MVP was failed attempted occlusion using other embolic devices. Five, single ventricle patients (median age 3-years, median weight 14.9 kg) underwent occlusion of veno-venous collaterals following bidirectional Glenn operation. Three patients (Median age 8 years) underwent occlusion of coronary artery fistulae (CAF). Two patients (age 7 months and 1 year) underwent occlusion of large aorto-pulmonary collaterals. A 7-day-old child with a large CAF required 2 MVPs and an Amplatzer Vascular Plug (AVP-II) for complete occlusion. Occlusion of all other blood vessels was achieved using a single MVP. One MVP embolized distally in an 8-years-old child with a large CAF. There were no other procedural complications or during follow-up (median 9 months).

CONCLUSIONS

The MVP is a new, large-diameter vascular embolization device that can be delivered through a microcatheter. It may play an important role in providing highly effective occlusion of abnormal vessels in children.

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.

Anesthetic Implications of the Fontan Procedure for Single Ventricle Physiology

The Fontan procedure is the operation of choice for patients considered to be candidates for definitive palliation of single ventricle physiology. Anesthetic technique for the Fontan procedure is not well described in the literature, and the medical and surgical treatment of these patients is rapidly evolving. With an understanding of the anatomy and phys iology of the Fontan patient, a safe and effective anesthetic can be executed. An understanding of the changes that occur during the perioperative period is critical. This article focuses on a review of single ventricle physiology and Fon tan physiology, preoperative assessment and risk factors for the Fontan procedure, intraoperative management, and management of low cardiac output in the postbypass period.

Current status of brain protection during surgery for congenital cardiac defect

The long-term neurodevelopmental outcome has been a great concern for cardiac surgeons although it is still unclear. There are some risks regarding the neurological and neuropsychological deficits before, during and after cardiovascular surgery. Current status of brain protection during congenital heart surgery could be reported. The incidence of neurologic outcome and the appropriate CPB strategy for brain protection are stated, and the latest data of neurodevelopmental outcome after pediatric cardiac surgery are clarified.

Characterizing the angiogenic activity of patients with single ventricle physiology and aortopulmonary collateral vessels

OBJECTIVES

Patients with single ventricle congenital heart disease often form aortopulmonary collateral vessels via an unclear mechanism. To gain insights into the pathogenesis of aortopulmonary collateral vessels, we correlated angiogenic factor levels with in vitro activity and angiographic aortopulmonary collateral assessment and examined whether patients with single ventricle physiology have increased angiogenic factors that can stimulate endothelial cell sprouting in vitro.

METHODS

In patients with single ventricle physiology (n = 27) and biventricular acyanotic control patients (n = 21), hypoxia-inducible angiogenic factor levels were measured in femoral venous and arterial plasma at cardiac catheterization. To assess plasma angiogenic activity, we used a 3-dimensional in vitro cell sprouting assay that recapitulates angiogenic sprouting. Aortopulmonary collateral angiograms were graded using a 4-point scale.

RESULTS

Compared with controls, patients with single ventricle physiology had increased vascular endothelial growth factor (artery: 58.7 ± 1.2 pg/mL vs 35.3 ± 1.1 pg/mL, P < .01; vein: 34.8 ± 1.1 pg/mL vs 21 ± 1.2 pg/mL, P < .03), stromal-derived factor 1-alpha (artery: 1901.6 ± 1.1 pg/mL vs 1542.6 ± 1.1 pg/mL, P < .03; vein: 2092.8 pg/mL ± 1.1 vs 1752.9 ± 1.1 pg/mL, P < .02), and increased arterial soluble fms-like tyrosine kinase-1, a regulatory vascular endothelial growth factor receptor (612.3 ± 1.2 pg/mL vs 243.1 ± 1.2 pg/mL, P < .003). Plasma factors and sprout formation correlated poorly with aortopulmonary collateral severity.

CONCLUSIONS

We are the first to correlate plasma angiogenic factor levels with angiography and in vitro angiogenic activity in patients with single ventricle disease with aortopulmonary collaterals. Patients with single ventricle disease have increased stromal-derived factor 1-alpha and soluble fms-like tyrosine kinase-1, and their roles in aortopulmonary collateral formation require further investigation. Plasma factors and angiogenic activity correlate poorly with aortopulmonary collateral severity in patients with single ventricles, suggesting complex mechanisms of angiogenesis.

What radiologists need to know about the pulmonary-systemic flow ratio (Qp/Qs): what it is, how to calculate it, and what it is for

Cardiac magnetic resonance imaging (cMRI) provides abundant morphological and functional information in the study of congenital heart disease. The functional information includes pulmonary output and systemic output; the ratio between these two (Qp/Qs) is the shunt fraction. After birth, in normal conditions the pulmonary output is practically identical to the systemic output, so Qp/Qs = 1. In patients with « shunts » between the systemic and pulmonary circulations, the ratio changes, and the interpretation of these findings varies in function of the location of the shunt (intracardiac or extracardiac) and of the associated structural or postsurgical changes. We review the concept of Qp/Qs; the methods to calculate it, with special emphasis on cMRI; and the meaning of the results obtained. We place special emphasis on the relevance of these findings depending on the underlying disease and the treatment the patient has undergone.

Ratio between fms-like tyrosine kinase 1 and placental growth factor in children with congenital heart disease

Serum levels of soluble fms-like tyrosine kinase 1 (sFlt-1), an antiangiogenic factor, and its binding protein, placental growth factor (PlGF), are altered in women with preeclampsia. Recently, the sFlt-1/PlGF ratio has been shown to predict acute coronary syndrome in adults. However, few reports have described the use of the sFlt-1/PlGF ratio for evaluating an abnormal hemodynamic load in children with congenital heart disease (CHD). The sFlt-1/PlGF ratio was determined in 20 children with atrial septal defects (ASD), 26 children with ventricular septal defects (VSD), 57 children with tetralogy of Fallot (ToF), 35 children who were Fontan candidates (Fontan), and 14 controls. The preoperative sFlt-1/PlGF ratios in the ASD, VSD, and Fontan were significantly higher than those in the controls and were significantly decreased after surgical repair in the ASD and VSD. In the ToF, the sFlt-1/PlGF ratio was highest after first-stage repair and second-highest after final-stage palliation compared with the preoperative levels. The sFlt-1/PlGF ratio was highest after first-stage repair and much lower after final-stage palliation in the Fontan. Furthermore, these ratios correlated with the degree of the ventricular volume overload and hypoxia. Our study clearly demonstrated that the sFlt-1/PlGF ratio increases with volume overload and persistent hypoxia after surgery with CHD. These findings may prove useful in the management of CHD in children.

Risk Factors Associated with Prolonged Mechanical Ventilation after Corrective Surgery for Tetralogy of Fallot

INTRODUCTION

This study examined early postoperative results to identify perioperative factors that are associated with prolonged mechanical ventilation (PMV) in tetralogy of Fallot (TOF) patients undergoing corrective surgery.

METHODS

We retrospectively examined the role of perioperative variables in determining the period of mechanical ventilatory support in TOF patients undergoing corrective surgery. A total of 821 patients were included in the study. The cohort was divided into a PMV group that included patients with >90th percentile for duration of mechanical ventilation and a non-PMV group which included all other patients.

RESULTS

Non-PMV group consisted of 751 patients (454 males, 297 females; median age 12 months, interquartile range 8-19 months; mean weight 9.60 ± 2.98 kg). PMV group consisted of 70 patients (51 males, 19 females; median age 8 months, interquartile range 6.75-13 months; mean weight 8.64 ± 1.95 kg). No patients died in the non-PMV group compared with two deaths due to acute respiratory distress syndrome in the PMV group. Univariate risk factors for PMV included age, weight, left ventricular end-diastolic volume index (LVEDVI), McGoon ratio, Nakata index, previous palliative operations, cardiopulmonary bypass (CPB) time, aortic cross-clamp (ACC) time, preoperative major aortopulmonary collateral arteries (MAPCAs) occlusion by coils in hybrid procedure, postoperative right ventricular/left ventricular systolic pressure ratio, central venous pressure (CVP), left atrial pressure (LAP), endotracheal reintubation, vasoactive-inotropic score (VIS), renal replacement therapy, and early-onset ventilator-associated pneumonia (VAP). In a multivariable model, age, LVEDVI, McGoon ratio, Nakata index, previous palliative operations, CPB time, blood returning to left atrium during surgery as a surrogate marker for significant aortopulmonary collateral presence, and early-onset VAP were the independent risk factors for PMV.

CONCLUSIONS

The risk factors for PMV were age, LVEDVI, McGoon ratio, Nakata index, previous palliative operations, CPB time, VIS, LAP, blood returning to left atrium during surgery, and early-onset VAP.

Tetralogy of Fallot with pulmonary atresia and major aortopulmonary collateral vessels

Major aortopulmonary collateral arteries (MAPCAs) provide significant issues during cardiopulmonary bypass, including flooding of the surgical field which requires significant blood volumes to be returned to the extracorporeal circuit via handheld suckers. This has been shown to be the major source of gaseous microemboli and is associated with adverse neurological outcome. Use of pH-stat has been previously shown to decrease the shunt through MAPCAs via an unknown mechanism. Here, we report the associated benefits of pH-stat in decreasing sucker usage and gaseous microemboli in a patient with known MAPCAs presenting for repair of tetralogy of Fallot and pulmonary atresia.

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

BACKGROUND

The significance and optimal treatment of systemic-to-pulmonary arterial collateral (SPC) vessels in single ventricle patients are poorly understood. The acute efficacy of SPC embolization has not been demonstrated in a quantifiable fashion. We sought to assess the acute efficacy of SPC embolization on blood flow as quantified by phase contrast magnetic resonance imaging and hypothesized that embolization acutely decreases SPC flow and increases systemic blood flow (Q(S)).

METHODS AND RESULTS

Six superior cavopulmonary connection patients underwent SPC flow quantification by phase contrast magnetic resonance imaging, including quantification of superior and inferior caval, total pulmonary artery, total pulmonary vein, ascending and descending aortic flows (Q(SVC), Q(IVC), Q(PA), Q(PV), Q(Ao), and Q(Dao), respectively), both immediately before and after cardiac catheterization with coil and particle embolization of angiographically evident SPC vessels. All studies were performed under a single anesthetic. After embolization, we found a significant decrease in SPC flow of 0.9 (range, 0.6-1.3) L/(min·m(2)) (P=0.03); a median reduction of 47% (range, 32-60). There was a significant decrease in the median Q(P):Q(S) from 1.3 before to 0.8 after embolization (P=0.03), and an increase in Q(S) from a median of 3.4 to 4.4 L/(min·m(2)) (P<0.05), and Q(SVC) from a median of 1.7 to 2.3 L/(min·m(2)) (P=0.03).

CONCLUSIONS

We report on the acute efficacy of SPC embolization, demonstrating a significant decrease in SPC flow and Q(P):Q(S) and increase in Q(SVC) and Q(S). Further studies are needed to assess the durability of the procedure and the effect on Fontan and longer-term outcomes.

Aortopulmonary collateral flow volume affects early postoperative outcome after Fontan completion: a multimodality study

OBJECTIVE

Aortopulmonary collaterals are a frequent phenomenon in patients after bidirectional cavopulmonary connection. The aortopulmonary collateral flow volume can be quantified using cardiac magnetic resonance imaging. However, the significance of aortopulmonary collateral flow for the postoperative outcome after total cavopulmonary connection is unclear and was sought to be determined.

METHODS

The data from 33 patients were prospectively studied with cardiac magnetic resonance, echocardiography, and cardiac catheterization before the total cavopulmonary connection operation. The early postoperative outcomes after total cavopulmonary connection completion were recorded.

RESULTS

Aortopulmonary collateral flow was 1.59 L/min/m(2) ± 0.65 L/min/m(2) (range, 0.54 L/min/m(2)-3.34 L/min/m(2)), constituting 43% ± 13% (range, 12-87%) of pulmonary blood flow and 35% ± 12% (range, 11-62%) of the cardiac index, resulting in a pulmonary blood flow/systemic blood flow ratio of 1.06 ± 0.17 (range, 0.79-1.55). The aortopulmonary collateral flow correlated with pulmonary blood flow/systemic blood flow ratio (r = 0.69, P < .0001), oxygen saturation (r = 0.42, P = .018), and cardiac index (r = 0.53, P = .002). Of the 36 patients, 24 underwent fenestrated total cavopulmonary connection during the study period. The aortopulmonary collateral flow, relative to the cardiac index, correlated with the duration of hospital stay (r = 0.48, P = .02) and pleural drainage (r = 0.45, P = .03). Patients whose pleural drainage lasted 1 week or less had less aortopulmonary collateral flow before the Fontan operation than those with a longer period until chest tube removal (1.23 L/min/m(2) ± 0.38 L/min/m(2) vs 1.73 L/min/m(2) ± 0.76 L/min/m(2); P = .03). Compared with a contemporary group of total cavopulmonary connection patients with fenestration in their extracardiac conduit who were studied prospectively, with a similar protocol, the bidirectional cavopulmonary connection had a greater amount of aortopulmonary collateral flow (1.59 L/min/m(2) ± 0.65 L/min/m(2) vs 1.30 L/min/m(2) ± 0.57 L/min/m(2), P = .04).

CONCLUSIONS

Patients after bidirectional cavopulmonary connection routinely acquire a large amount of aortopulmonary collateral flow. The hemodynamic consequences of aortopulmonary collateral flow translate into adverse outcomes early after total cavopulmonary connection completion.

Relation of systemic-to-pulmonary artery collateral flow in single ventricle physiology to palliative stage and clinical status

Systemic-to-pulmonary collateral arteries (SPCs) are common in patients with single-ventricle physiology, but their impact on clinical outcomes is unclear. The aim of this study was to use retrospective cardiac magnetic resonance data to determine the relation between SPC flow and palliative stage and clinical status in single-ventricle physiology. Of 116 patients, 78 were after Fontan operation (median age 19 years) and 38 were at an earlier palliative stage (median age 2 years). SPC flow was quantified as aortic flow minus total caval flow or total pulmonary vein flow minus total branch pulmonary artery flow. Median SPC flow/body surface area (BSA) was higher in the pre-Fontan group (1.06 vs 0.43 L/min/m(2), p <0.0001) and decreased nonlinearly with increasing age after the Fontan operation (r(2) = 0.17, p <0.0001). In the Fontan group, patients in the highest quartile of SPC flow had larger ventricular end-diastolic volume/BSA (p <0.0001) and were older at the time of Fontan surgery (p = 0.04), but SPC flow/BSA was not associated with heart failure symptoms, atrial or ventricular arrhythmias, atrioventricular valve regurgitation, the ventricular ejection fraction, or peak oxygen consumption. In multivariate analysis of all patients (n = 116), higher SPC flow was independently associated with pre-Fontan status, unilateral branch pulmonary artery stenosis, a diagnosis of hypoplastic left-heart syndrome, and previous catheter occlusion of SPCs (model r(2) = 0.37, p <0.0001). In conclusion, in this cross-sectional study of single-ventricle patients, BSA-adjusted SPC flow was highest in pre-Fontan patients and decreased after the Fontan operation with minimal clinical correlates aside from ventricular dilation.

Systemic-to-pulmonary collateral flow, as measured by cardiac magnetic resonance imaging, is associated with acute post-Fontan clinical outcomes

BACKGROUND

Systemic-pulmonary collateral (SPC) flow occurs commonly in single ventricle patients after superior cavo-pulmonary connection, with unclear clinical significance. We sought to evaluate the association between SPC flow and acute post-Fontan clinical outcomes using a novel method of quantifying SPC flow by cardiac magnetic resonance (CMR) imaging.

METHODS AND RESULTS

All patients who had SPC flow quantified by CMR imaging before Fontan were retrospectively reviewed to assess for acute clinical outcomes after Fontan completion. Forty-four subjects were included who had Fontan completion between May 2008 and September 2010. SPC flow prior to Fontan measured 1.5±0.9 L/min/m(2), accounting for 31±11% of total aortic flow and 44±15% of total pulmonary venous flow. There was a significant linear association between natural log-transformed duration of hospitalization and SPC flow as a proportion of total aortic (rho=0.31, P=0.04) and total pulmonary venous flow (rho=0.29, P=0.05). After adjustment for Fontan type and presence of a fenestration, absolute SPC flow was significantly associated with hospital duration ≥7 days (odds ratio [OR]=9.2, P=0.02) and chest tube duration ≥10 days (OR=22.7, P=0.009). Similar associations exist for SPC flow as a percentage of total aortic (OR=1.09, P=0.048 for hospitalization ≥7 days; OR=1.24, P=0.007 for chest tube duration ≥10 days) and total pulmonary venous flow (OR=1.07, P=0.048 for hospitalization ≥7 days; OR=1.18, P=0.006 for chest tube duration ≥10 days).

CONCLUSIONS

Increasing SPC flow before Fontan, as measured by CMR imaging, is associated with increased duration of hospitalization and chest tube following Fontan completion.

Late catheter interventions in hypoplastic left heart syndrome

Interventional cardiology plays a key role in the diagnosis and management of patients with functionally univentricular physiology after the various stages of surgical palliation. The interventions performed are widely variable in type, including angioplasty of stenotic vessels and implantation of stents in stenotic vessels; closure of defects such as collaterals, leaks in baffles, and fenestrations; creation of fenestration; and more. In the setting of venous hypertension associated with stenosis at the Fontan baffle, conduit, or pulmonary arteries, stent implantation is often preferred, as the aim is to eliminate completely the narrowing, given that relatively mild stenosis can have a significant detrimental hemodynamic effect in patients with functionally univentricular circulation. The procedure is highly successful. In patients who fail after Fontan procedure, creation of a fenestration is often performed, with variable technique depending on the underlying anatomic substrate. To increase chances of patency of the fenestration, implantation of a stent is often required, particularly in the setting of an extracardiac conduit. For those patients with cyanosis and favorable Fontan hemodynamics, closure of the fenestration is performed using atrial septal occluder devices with high success rate. Coils compatible with magnetic resonance imaging are used widely to treat collateral vessels, although on occasion other specific embolization tools are required, such as particles or vascular plugs. Postoperative arch obstruction is successfully managed with angioplasty at a younger age, while implantation of a stent in the aorta is reserved for older patients. Specifics of these interventional procedures as applied to the population of patients with functionally univentricular hearts are described in this manuscript.

The role of cardiovascular magnetic resonance in candidates for Fontan operation: proposal of a new algorithm

BACKGROUND

To propose a new diagnostic algorithm for candidates for Fontan and identify those who can skip cardiac catheterization (CC).

METHODS

Forty-four candidates for Fontan (median age 4.8 years, range: 2-29 years) were prospectively evaluated by trans-thoracic echocardiography (TTE), Cardiovascular magnetic resonance (CMR) and CC. Before CC, according to clinical, echo and CMR findings, patients were divided in two groups: Group I comprised 18 patients deemed suitable for Fontan without requiring CC; group II comprised 26 patients indicated for CC either in order to detect more details, or for interventional procedures.

RESULTS

In Group I ("CC not required") no unexpected new information affecting surgical planning was provided by CC. Conversely, in Group II new information was provided by CC in three patients (0 vs 11.5%, p = 0.35) and in six an interventional procedure was performed. During CC, minor complications occurred in one patient from Group I and in three from Group II (6 vs 14%, p = 0.7). Radiation Dose-Area product was similar in the two groups (Median 20 Gycm(2), range: 5-40 vs 26.5 Gycm(2), range: 9-270 p = 0.37). All 18 Group I patients and 19 Group II patients underwent a total cavo-pulmonary anastomosis; in the remaining seven group II patients, four were excluded from Fontan; two are awaiting Fontan; one refused the intervention.

CONCLUSION

In this paper we propose a new diagnostic algorithm in a pre-Fontan setting. An accurate non-invasive evaluation comprising TTE and CMR could select patients who can skip CC.

Long-term results of total cavopulmonary connection with low ejection fraction

PURPOSE

The aim of this study was to investigate the surgical outcomes and change in cardiac performance after total cavopulmonary connection (TCPC) in patients with reduced ventricular ejection preoperatively.

METHODS

Among the 195 patients undergoing TCPC between 1990 and 2001 were 52 who had a preoperative ejection fraction of ≤50% (30%-50%, mean 44%). A dominant ventricle was of the morphologically right type in 81% of patients.

RESULTS

A total of 9 of the 52 patients died early. Two patients died in the intermediate term. Postoperative exercise testing showed maximum oxygen uptake of 26.4 ± 5.8 ml/kg/min (anaerobic threshold 18.3 ± 3.2 ml/kg/ min). The cardiac index was 3.1 ± 0.9 l/min/m(2) at 1 year after TCPC, with no fundamental change at 5 years (3.1 ± 0.8 l/min/m(2)). The end-diastolic volume of the dominant ventricle was 130% ± 74% of the anticipated normal value at 1 year and 93% ± 27% at 5 years after TCPC, with ejection fractions of 48% ± 13% and 49% ± 9%, respectively. When these parameters were plotted for the individual patients, the ejection fraction increased during the first postoperative year, with the percent end-diastolic volume decreasing in 31 survivors; the trend appeared atypical in the remaining 12 survivors. Even in these patients, however, the parameters eventually changed toward favorable circumstances 5 years after TCPC.

CONCLUSION

Change in ventricular function was not necessarily pessimistic after TCPC in patients with reduced ventricular contraction preoperatively.

The Fontan procedure: anatomy, complications, and manifestations of failure

The Fontan procedure refers to any operation that results in the flow of systemic venous blood to the lungs without passing through a ventricle. It is performed to treat several complex congenital heart abnormalities including tricuspid atresia, pulmonary atresia with intact ventricular septum, hypoplastic left heart syndrome, and double-inlet ventricle. The original Fontan procedure included direct anastomosis of the right atrium to the main pulmonary artery; however, multiple modifications have been employed. Creation of Fontan circulation is palliative in nature, with good results in patients with ideal hemodynamics and substantial morbidity and mortality in those with poor hemodynamics. Complications of Fontan circulation include exercise intolerance, ventricular failure, right atrium dilatation and arrhythmia, systemic and hepatic venous hypertension, portal hypertension, coagulopathy, pulmonary arteriovenous malformation, venovenous shunts, and lymphatic dysfunction (eg, ascites, edema, effusion, protein-losing enteropathy, and plastic bronchitis). Magnetic resonance imaging is best for postoperative evaluation of patients who underwent the Fontan procedure, and cardiac transplantation remains the only definitive treatment for those with failing Fontan circulation.

Practice variability and outcomes of coil embolization of aortopulmonary collaterals before Fontan completion: a report from the Pediatric Heart Network Fontan Cross-Sectional Study

BACKGROUND

The practice of coiling aortopulmonary collaterals (APCs) before Fontan completion is controversial, and published data are limited. We sought to compare outcomes in subjects with and without pre-Fontan coil embolization of APCs using the Pediatric Heart Network Fontan Cross-Sectional Study database which enrolled survivors of prior Fontan palliation.

METHODS

We compared hospital length of stay after Fontan in 80 subjects who underwent APC coiling with 459 subjects who did not. Secondary outcomes included post-Fontan complications and assessment of health status and ventricular performance at cross-sectional evaluation (mean 8.6 ± 3.4 years after Fontan).

RESULTS

Centers varied markedly in frequency of pre-Fontan APC coiling (range 0%-30% of subjects, P < .001). The coil group was older at Fontan (P = .004) and more likely to have single right ventricular morphology (P = .054) and pre-Fontan atrioventricular valve regurgitation (P = .03). The coil group underwent Fontan surgery more recently (P < .001), was more likely to have a prior superior cavopulmonary anastomosis (P < .001), and more likely to undergo extracardiac Fontan connection (P < .001) and surgical fenestration (P < .001). In multivariable analyses, APC coiling was not associated with length of stay (hazard ratio for remaining in-hospital 0.91, 95% CI 0.70-1.18, P = .48) or postoperative complications, except more post-Fontan catheter interventions (hazard ratio 1.74, 95% CI 1.04-2.91, P = .03), primarily additional APC coils. The groups had similar outcomes at cross-sectional evaluation.

CONCLUSION

Management of APCs before Fontan shows marked practice variation. We did not find an association between pre-Fontan coiling of APCs and shorter postoperative hospital stay or with better late outcomes. Prospective studies of this practice are needed.

Fontan "Ten Commandments" revisited and revised

Choussat's "Ten Commandments," which describes the components of an ideal Fontan candidate, was first published in 1977. Despite the wisdom in these commandments, it is clear from a historic perspective that total compliance with all criteria does not necessarily portend excellent long-term survival. I believe the end point of the original commandments should be modified to include improvement in long-term survival. I suggest the following single commandment: "Thou Shalt Be Perfect."

What is the clinical utility of routine cardiac catheterization before a Fontan operation?

Patients with single-ventricle circulation presenting for Fontan completion routinely undergo cardiac catheterization despite ongoing debate concerning its additive value. Increasing interest in noninvasive preoperative evaluation alone led the authors to analyze the utility of routine pre-Fontan catheterization and to determine whether a subset of patients could avoid this invasive procedure. Patients younger than 5 years referred for pre-Fontan evaluation were retrospectively reviewed. Medical records and catheter angiograms were examined, and catheterizations were categorized as "additive" based on predetermined criteria. Associations between precatheterization variables, catheterization findings, and short-term postoperative outcomes were evaluated. Cardiac catheterization was clinically nonadditive for 89 of 175 patients undergoing pre-Fontan evaluation (51%). There were no robust precatheterization predictors of a nonadditive catheterization. Echocardiography did not fully demonstrate the relevant anatomy of 115 patients (66%), most frequently due to inadequate visualization of the pulmonary arteries, and 22 patients had additive catheterizations due to new diagnostic findings alone. Interventions at catheterization were frequent and deemed "important" for 64 patients (37%). Catheterization hemodynamic data were not associated with early postoperative outcomes. Minor catheterization complications occurred for 51 patients (29%) and major complications for 4 patients (2%). Although at least 50% of the patients presenting for Fontan completion may be able to avoid routine catheterization safely, an echocardiography-based imaging strategy alone is insufficient to allow proper identification of those who could be evaluated noninvasively. A more comprehensive imaging strategy not based solely on echocardiography should be considered.

Vascular endothelial growth factor in children with cyanotic and acyanotic and congenital heart disease

INTRODUCTION

Vascular endothelial growth factor is a potent stimulator of angiogenesis. Children with cyanotic congenital heart disease often experience the development of widespread formation of collateral blood vessels, which may represent a form of abnormal angiogenesis resulting in increased morbidity and mortality. We undertook the present study to determine whether children with cyanotic congenital heart disease have elevated serum levels of vascular endothelial growth factor compared to children with acyanotic heart disease.

MATERIAL AND METHODS

Serum was obtained from 35 children with cyanotic congenital heart disease and 30 children with acyanotic heart disease. Vascular endothelial growth factor levels were measured in the serum of these patients by sandwich enzyme immunoassay.

RESULTS

Vascular endothelial growth factor was significantly elevated in children with cyanotic congenital heart disease compared to children with acyanotic heart disease (150.3 ±48.1 vs. 85.4 ±18.7 pg/ml, respectively, p < 0.001). In the cyanotic group, oxygen saturation (SaO(2)) was negatively correlated with VEGF (r=-0.631, p < 0.001) while haemoglobin was positively correlated (r=0.781, p = 0.007). No significant correlations were found in the acyanotic group.

CONCLUSIONS

Children with cyanotic congenital heart disease have elevated systemic levels of vascular endothelial growth factor directly related to the degree of cyanosis (SaO(2) and haemoglobin levels). These findings suggest that the widespread formation of collateral vessels in these children may be mediated by vascular endothelial growth factor.

Aortopulmonary collaterals after bidirectional cavopulmonary connection or Fontan completion: quantification with MRI

BACKGROUND

Aortopulmonary collaterals (APCs) have been associated with increased morbidity after the Fontan operation. We aimed to quantify APC flow after bidirectional cavopulmonary connections and Fontan completions, using phase-contrast MRI, and to identify risk factors for the development of APCs.

METHODS AND RESULTS

APC blood flow was quantifiable in 24 of 36 retrospectively analyzed MRI studies. Sixteen studies were performed after the bidirectional cavopulmonary connections (group A) and 8 after the Fontan operation (group B). APC blood flow was calculated by subtracting the blood flow volume through the pulmonary arteries from that through the pulmonary veins. The ratio of pulmonary to systemic blood flow (Qp/Qs) was 0.93+/-0.26 in group A and 1.27+/-0.16 in group B. APC flow was 1.42 (0.58 to 3.83) L/min/m(2) and 0.82 (0.50 to 1.81) L/min/m(2) in groups A and B, respectively. The mean inaccuracies corresponded to 7.9+/-14.5% and 7.1+/-13.6% of ascending aortic flow in groups A and B, respectively. Qp/Qs was negatively correlated with a younger age at the time of the bidirectional cavopulmonary connections operation (r=0.62, P=0.01) and positively correlated with the age at the time of the Fontan completion (r=0.81, P=0.01). Patients with a previous right-sided modified Blalock-Taussig shunt had more collateral flow to the right lung than those without.

CONCLUSIONS

APC blood flow can be noninvasively measured in bidirectional cavopulmonary connections and Fontan patients, using MRI in the majority of patients and results in a significant left-to-right shunt.

Quantification of collateral aortopulmonary flow in patients subsequent to construction of bidirectional cavopulmonary shunts

OBJECTIVES

We sought to provide a new method for quantifying collateral aortopulmonary flow in patients subsequent to construction of a bidirectional cavopulmonary shunt, and to clarify the clinical advantages of the new method.

METHODS

We performed lung perfusion scintigraphy and cardiac catheterization in 10 patients subsequent to construction of a bidirectional cavopulmonary shunt. First, the ratio of collateral to systemic flow was determined by whole-body images of lung perfusion scintigraphy, dividing the total lung count by the total body count minus the total lung count. Second, we integrated lung perfusion scintigraphy and cardiac catheterization data using a formula derived from the Fick principle, taking the ratio of pulmonary to systemic flow to be 1 plus the ratio calculated above and multiplied by the systemic saturation minus the inferior caval venous saturation divided by the pulmonary venous saturation minus the inferior caval venous saturation. Finally, the amount of collateral flow was obtained from the ratio of pulmonary to systemic flow. We evaluated the impact of collateral flow on the calculation of pulmonary vascular resistance.

RESULTS

The median age at bidirectional cavopulmonary shunt was 1.41 years, and the median age at catheterization was 2.33 years. The mean amount of collateral flow was 1.75 +/- 0.46 litres/min/m(2). The pulmonary vascular resistance calculated without considering the collateral flow was overestimated by an average of 57 +/- 23%, compared to the resistance calculated with our new method.

CONCLUSIONS

The use of scintigraphy combined with catheterization allows accurate determination of aortopulmonary collateral flow, and avoids overestimation of pulmonary vascular resistance in these candidates for the Fontan circulation.