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

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.

Systemic-to-pulmonary collateral flow associations with antegrade pulmonary flow in single ventricle patients: insights from cardiac magnetic resonance imaging

Purpose

In the palliated single ventricle anomalies, a considerable amount of the aortic flow may be absorbed by the systemic-pulmonary collateral flow (SPCF), which can be noninvasively assessed by cardiac magnetic resonance (CMR). The aims of this study were to (1) identify factors associated with SCPF in pediatric single ventricle patients, and (2) establish a cutoff values indicating an association between SCPF and a reduction in antegrade pulmonary flow.

Methods

A retrospective single-tertiary-center cohort study included 158 consecutive CMR studies of patients with a single ventricle. In the uni- and multivariable analysis, SPCF was presented as a percentage of the total pulmonary venous flow (SPCF%PV). The minimal clinically important difference in QP/QS ratios was estimated as ≥0.50, and an optimal cutoff value was defined using the receiver operating characteristic (ROC) curve.

Results

SPCF%PV was significantly smaller in the post-total cavopulmonary connection (TCPC) group than in the pre-TCPC patients (p < 0.001). The patient's higher age and a higher antegrade pulmonary flow were associated with a lower SPCF%PV. A negative weak association was observed between the SPCF%PV and systemic saturation (r = -0.39, p < 0.001). SPCF%PV did not associate with ventricular volumes nor ejection fraction. The SPCF%PV was significantly smaller in patients that were palliated primarily with a pulmonary artery banding compared to those palliated with a BT-shunt (p = 0.002) or RV-PA- shunt (p = 0.044). In the ROC analysis, for pre-TCPC patient's, a cutoff of SPCF%PV 42% yielded a sensitivity of 100% and specificity of 80% for significantly reduced antegrade pulmonary flow (AUC 0.97). In the post-TCPC group, the optimal SPCF%PV cutoff was 34% (sensitivity 100%, specificity 98%, AUC 0.99).

Conclusion

SPCF results in a considerable left-to-right shunt, which subsequently diminishes spontaneously after TCPC. Our findings indicated that for pre-TCPC patients, an SPCF%PV threshold of 42% (sensitivity 100%, specificity 80%), and for the post-TCPC group, a threshold of 34% (sensitivity 100%, specificity 98%) were effective in identifying reduced antegrade pulmonary flow.

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.

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.

Basic Concepts and Insights into Aortopulmonary Collateral Arteries in Congenital Heart Diseases

Aortopulmonary collateral arteries are persistent embryological vessels supplying lung parenchyma in various cardiopulmonary diseases with underlying pulmonary hypoperfusion. Their identification and mapping are important because of associated clinical implications and tendency to affect the surgical outcome. This article describes the embryological development and clinical relevance of aortopulmonary collaterals in various congenital cardiopulmonary conditions, along with the significance for treatment planning. Roles, strength, and shortcomings of the various imaging options and image-guided interventions are discussed, with a focus on presurgical planning and preparation, as well as postsurgical management.

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.

Influence of Respiration on Collateral Flow in the Fontan Population Using Real-time Phase-contrast Cardiovascular Magnetic Resonance: Collateral Flow Does Not Protect the Ventricle From Volume Deficiency and Diastolic Dysfunction

PURPOSE

The clinical significance of collateral flow for the ventricular function of patients with univentricular hearts is often debated. This study evaluates the impact of collateral flow on respiration-dependent preload modification and diastolic function in Fontan patients assessed by systemic and pulmonary vein (PV) flow patterns.

MATERIALS AND METHODS

Real-time phase-contrast cardiovascular magnetic resonance was performed in the right upper PV, ascending aorta, superior, and inferior vena cava (IVC) in 21 Fontan patients and 11 healthy individuals. The patients' respiratory cycle was divided into 4 periods to generate respiratory-dependent stroke volumes (SV i ). Conventional quantitative blood flow measurements were used to quantify and differentiate between low (group A) and high (group B) collateral flow.

RESULTS

Group B showed significantly lower SV i IVC in inspiration, end-inspiration, expiration, and SV i ΔIVC compared with group A (23.6±4.8 mL/m 2 to 33.4±8.0; P =0.005). PV flow resulted in a lower mean SV i PV (11.6±7.6 mL/m 2 , vs. 14.0±11.4 mL/m 2 ) as well as a significantly lower peak systolic S-wave velocity (S max ) ( P =0.005), S/D-ratio (S max /peak diastolic wave velocity) ( P =0.015), and shorter diastolic deceleration time (DT D ; P =0.030; median DT D =134 ms) compared with group A (DT D =202 ms).

CONCLUSIONS

This study demonstrates the incapability of Fontan patients to properly increase preload by inspiration in the presence of significant collateral flow. The results further show that collateral flow is associated with a volume-deprived ventricle and impaired diastolic function.

Collaterals in congenital heart disease: when and how to treat?

The development of collateral circulation is not that rare in patients with congenital heart defects. These collaterals can affect cardiovascular hemodynamics and cause systemic arterial desaturation, which arises the question whether these should be closed. To date, few if any reports have been published on the therapeutic management of collaterals in adult patients with congenital heart disease in heart failure (HF). The focus of this article is to provide a pragmatic approach in the assessment of collateral circulation of the patient with HF. By considering the underlying hemodynamics and overall effects of the collateral circulation, we aim to provide a practical tool useful in clinical decision making. The paper highlights mainly the systemic venous to systemic venous collaterals, systemic venous to pulmonary venous (or pulmonary venous atrium) collaterals, and pulmonary arterio-venous malformations. Systemic venous anomalies are frequent and reported in 20% to 40% of patients who underwent Glenn or Fontan procedure. A reduction in effective pulmonary blood flow, coupled with increasing oxygen demands with growth, as well as a pressure difference between the higher pressure caval venous system and lower pressure atria (so called decompressing collaterals) are potential causes of collateral formation. Whether angiogenesis de novo or reappearance of embryological venous channels is responsible for collateral formation remains to be elucidated.

Pulmonary Artery Development Over Time in Severe Ebstein Anomaly

Recently, the outcome of severe Ebstein anomaly (EA) has improved with the prevalence of the Starnes procedure. However, time-dependent changes in the size of the central pulmonary artery (PA) have not been fully understood. A retrospective chart review of patients with EA who underwent the Starnes procedure during the neonatal period and those with pulmonary atresia with intact ventricular septum (PAIVS) was performed at Fukuoka Children's Hospital. There were 14 patients in the severe EA group and 36 in the PAIVS group, with mean observational periods of 3.8 and 4.2 years, respectively. No significant difference in survival was observed between the groups. However, the mean size of the central PA was smaller in the severe EA group at each surgical stage (after systemic-to-pulmonary shunt, after the bidirectional Glenn procedure, and after the Fontan procedure). A significantly larger ventricular volume was observed in the severe EA group after the Fontan procedure. The growth of the central PA was poor in patients with severe EA. Patients with severe EA should be carefully monitored in this regard both before and after undergoing the Fontan procedure. Further studies regarding long-term prognosis are expected.

Longitudinal Trends of Vascular Flow and Growth in Patients Undergoing Fontan Operation

BACKGROUND

Single ventricle (SV) patients undergo multiple surgeries with subsequent changes in anatomy and hemodynamics. There is little cardiac magnetic resonance (CMR) data on serial changes in these patients. This study aimed to assess longitudinal changes of SV anatomy and hemodynamics in a large cohort.

METHODS

Anatomy and flow in SV patients with serial CMRs performed between 2008-2019 at a single institution were retrospectively reviewed. Mixed-effects linear regression was used to estimate changes over time at 3-9 months, 1-5 years, and >5 years after Fontan.

RESULTS

119 patients were included (51% with hypoplastic left heart;77% underwent extra-cardiac Fontan). 88 patients had 3 serial CMRs. Indexed right superior vena cava (RSVC), inferior vena cava (IVC), neo-aortic valve and descending aorta area decreased over time (beta -0.19,-0.44,-0.23 respectively;p<0.01) as did indexed RSVC, neo and native aorta and descending aorta flow (beta -0.49,-0.53,-0.59 respectively;p<0.0001). IVC flow and its contribution to total caval flow increased (beta 0.33;p<0.0001). Indexed right and left right pulmonary artery (LPA) flow did not change, however indexed LPA area decreased (beta -0.16;p=0.0014) with time. Systemic to pulmonary collateral flow remained unchanged prior to, and early after Fontan (beta -0.54;p=0.42) but decreased with time from Fontan (beta coefficient -0.22;p<0.0001).

CONCLUSIONS

In this cohort of longitudinally followed SV patients, there are significant trends in vascular size and flow over time from Fontan. These findings can be used as a framework to interpret serial CMR data in the SV, and non-invasively identify deviations from expected patterns prior to the development of clinical symptoms.

A Rare Cause of Hemoptysis in West Syndrome-Isolated Aortopulmonary Collaterals in Structurally Normal Heart

Major aortopulmonary collateral arteries (MAPCAs) are abnormal systemic to pulmonary collateral vessels originating from the persistent segmental arteries. The common conditions concomitant with MAPCA are congenital heart diseases with reduced pulmonary blood flow. Isolated MAPCAs represent occurrence of collaterals in the absence of underlying heart disease, which commonly present as heart failure, recurrent respiratory tract infection, and pulmonary artery hypertension. Here, we describe a case of West syndrome presenting with hemoptysis due to isolated MAPCAs and its causal relation and management.

Ventricular Assist Device Therapy in the Fontan Circulation

The number of Fontan patients with circulatory failure and systolic dysfunction is growing rapidly. The last decade has demonstrated that ventricular assist device (VAD) is an effective therapy in properly selected patients. Herein, we discuss the current approach to patient selection, implantation, and patient management.

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.

Systemic-to-Pulmonary Collateral Flow Correlates with Clinical Condition Late After the Fontan Procedure

In the Fontan circulation, there is a substantial degree of systemic-to-pulmonary collateral flow (SPCF), which can be measured by cardiac magnetic resonance (CMR). However, the correlation between the degree of SPCF and long-term outcomes is not fully understood. We retrospectively studied 321 patients who underwent the Fontan procedure and CMR at a single center. Using CMR, we calculated SPCF as pulmonary blood flow - systemic blood flow. %SPCF was defined as SPCF ÷ pulmonary blood flow. The mean age of patients at CMR was 14.3 ± 7.5 years. The average %SPCF was 13.0% ± 11.0%. With a multivariate analysis, %SPCF was significantly correlated with time (i.e., the longer the time period since the Fontan procedure, the lower the %SPCF) (p = 0.006), previous total anomalous pulmonary vein drainage (p = 0.007), a low pulmonary artery index (Nakata index) before the Fontan procedure (p = 0.04), and older age at the time of the Fontan procedure (p = 0.002). Regarding the findings after the Fontan procedure, %SPCF was significantly correlated with ventricular end-diastolic volume (p < 0.001), ventricular end-systolic volume (p < 0.001), central venous pressure (p < 0.001), plasma brain natriuretic peptide concentration (p < 0.001), hemoptysis (p = 0.009), and poor New York Heart Association functional class (p = 0.007). SPCF was correlated with clinical condition after the Fontan procedure. The importance of sufficient growth of the pulmonary vascular bed should be emphasized because the development of SPCF is believed to result from the poor condition of the pulmonary circulation.

Superior Cavopulmonary Connection: Its Physiology, Limitations, and Anesthetic Implications

The superior cavopulmonary connection (SCPC) or "bidirectional Glenn" is an integral, intermediate stage in palliation of single ventricle patients to the Fontan procedure. The procedure, normally performed at 3 to 6 months of life, increases effective pulmonary blood flow and reduces the ventricular volume load in patients with single ventricle (parallel circulation) physiology. While the SCPC, with or without additional sources of pulmonary blood flow, cannot be considered a long-term palliation strategy, there are a subset of patients who require SCPC palliation for a longer interval than the typical patient. In this article, we will review the physiology of SCPC, the consequences of prolonged SCPC palliation, and modes of failure. We will also discuss strategies to augment pulmonary blood flow in the presence of an SCPC. The anesthetic considerations in SCPC patients will also be discussed, as these patients may present for noncardiac surgery from infancy to adulthood.

Heart failure in single right ventricle congenital heart disease: physiological and molecular considerations

Because of remarkable surgical and medical advances over the past several decades, there are growing numbers of infants and children living with single ventricle congenital heart disease (SV), where there is only one functional cardiac pumping chamber. Nevertheless, cardiac dysfunction (and ultimately heart failure) is a common complication in the SV population, and pharmacological heart failure therapies have largely been ineffective in mitigating the need for heart transplantation. Given that there are several inherent risk factors for ventricular dysfunction in the setting of SV in addition to probable differences in molecular adaptations to heart failure between children and adults, it is perhaps not surprising that extrapolated adult heart failure medications have had limited benefit in children with SV heart failure. Further investigations into the molecular mechanisms involved in pediatric SV heart failure may assist with risk stratification as well as development of targeted, efficacious therapies specific to this patient population. In this review, we present a brief overview of SV anatomy and physiology, with a focus on patients with a single morphological right ventricle requiring staged surgical palliation. Additionally, we discuss outcomes in the current era, risk factors associated with the progression to heart failure, present state of knowledge regarding molecular alterations in end-stage SV heart failure, and current therapeutic interventions. Potential avenues for improving SV outcomes, including identification of biomarkers of heart failure progression, implications of personalized medicine and stem cell-derived therapies, and applications of novel models of SV disease, are proposed as future directions.

Reduced Right Ventricular Output Reserve in Patients With Systemic Sclerosis and Mildly Elevated Pulmonary Artery Pressure

OBJECTIVE

This prospective study was undertaken to evaluate right ventricular function and pulmonary arterial compliance (PAC; ratio of stroke volume to pulse pressure) at rest and during exercise in patients with systemic sclerosis (SSc) with normal mean pulmonary artery pressure (PAP), patients with SSc with mildly elevated mean PAP, and patients with SSc with manifest pulmonary hypertension (PH).

METHODS

Patients with SSc (n = 112) underwent clinical assessment and right-sided heart catheterization at rest and during exercise and were divided into 3 groups according to their resting mean PAP values: normal mean PAP (≤20 mm Hg), mildly elevated mean PAP (21-24 mm Hg), and PH (mean PAP ≥25 mm Hg). Results were compared between groups by analysis of variance followed by post hoc Student's t-test.

RESULTS

Compared to patients with normal mean PAP, patients with mildly elevated mean PAP had a lower 6-minute walking distance (P = 0.008), lower cardiac index (P = 0.027) and higher pulmonary vascular resistance (P = 0.0002) during exercise, and lower PAC at rest (P = 0.016) and different stages of exercise (P = 0.033 for 25W and P = 0.024 for 75W).

CONCLUSION

The results of this study suggest that impaired 6-minute walking distance in SSc patients with mildly elevated mean PAP might be caused by reduced PAC during exercise and reduced right ventricular output reserve, presumably due to impaired coupling between the right ventricle and the pulmonary vasculature. These findings provide further evidence of the clinical relevance of mildly elevated mean PAP in patients with SSc.

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.

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.

Where Is the "Optimal" Fontan Hemodynamics?

Fontan circulation is generally characterized by high central venous pressure, low cardiac output, and slightly low arterial oxygen saturation, and it is quite different from normal biventricular physiology. Therefore, when a patient with congenital heart disease is selected as a candidate for this type of circulation, the ultimate goals of therapy consist of 2 components. One is a smooth adjustment to the new circulation, and the other is long-term circulatory stabilization after adjustment. When either of these goals is not achieved, the patient is categorized as having "failed" Fontan circulation, and the prognosis is dismal. For the first goal of smooth adjustment, a lot of effort has been made to establish criteria for patient selection and intensive management immediately after the Fontan operation. For the second goal of long-term circulatory stabilization, there is limited evidence of successful strategies for long-term hemodynamic stabilization. Furthermore, there have been no data on optimal hemodynamics in Fontan circulation that could be used as a reference for patient management. Although small clinical trials and case reports are available, the results cannot be generalized to the majority of Fontan survivors. We recently reported the clinical and hemodynamic characteristics of early and late failing Fontan survivors and their association with all-cause mortality. This knowledge could provide insight into the complex Fontan pathophysiology and might help establish a management strategy for long-term hemodynamic stabilization.

The Pulmonary Circulation in the Single Ventricle Patient

In recent decades, survival of children with complex congenital heart disease has improved considerably. Specifically, children with a variety of congenital heart defects resulting in ‘single ventricle’ physiology can now undergo palliative surgery that allows survival beyond the neonatal period, and in many cases into adulthood, despite having a single functional ventricular pumping chamber supplying both the pulmonary and systemic circulation. Our growing understanding of the functionally univentricular heart has resulted in freedom from Fontan failure of >50% at 25 years post-Fontan. Yet there is still a fair amount of knowledge to be gained, specifically as it relates to the pulmonary circulation in this group of patients. Knowledge gaps relate not only to the pulmonary circulation after Fontan operation, but also at each stage of the single ventricle surgical palliation, including the native physiology prior to any intervention. The pulmonary circulation is affected by multiple issues related to the single ventricle, including specific details of the anatomy unique to each patient, any intervention(s) undertaken, and potential complications such as aortopulmonary collaterals, protein losing enteropathy, plastic bronchitis, venovenous collaterals, pulmonary arteriovenous fistulae, ventricular dysfunction, pulmonary venous stenosis, and more. This chapter will review the current knowledge with regard to the pulmonary circulation in the single ventricle patient, primarily after the Fontan operation. Additionally, it is our hope to help the practitioner assess the pulmonary circulation in the single ventricle patient; we will also discuss the evidence behind and approach to treatment strategies in order to optimize the pulmonary circulation in this complex group of patients.

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.

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.

Advances in pediatric cardiac MRI

PURPOSE OF REVIEW

Spurred by numerous recent technological advances, cardiac MRI (CMR) is now the gold standard for anatomic evaluation, quantitative assessment of chamber size and function, flow quantification, and tissue characterization. This review focuses on recent advances in pediatric and congenital CMR, highlighting recent safety data, and discussing future directions.

RECENT FINDINGS

CMR has become an important component of risk stratification and procedural planning in numerous congenital and pediatric heart diseases. Innovative approaches to image acquisition and reconstruction are leading the way toward fast, high-resolution, three- and four-dimensional datasets for delineation of cardiac anatomy, function, and flow. In addition, techniques for assessing the composition of the myocardium may help elucidate the pathophysiology of late complications, identify patients at risk for heart failure, and assist in the evaluation of therapeutic strategies.

SUMMARY

CMR provides invaluable morphologic, hemodynamic, and functional data that help guide diagnosis, assessment, and management of pediatric and adult congenital heart disease. As imaging techniques advance and data accumulate on the relative and additive value of CMR in patient care, its role in a multimodality approach to the care of this population of patients is becoming clear and is likely to continue to evolve.

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.

Effect of Inhaled Nitric Oxide on Blood Flow Dynamics in Patients After the Fontan Procedure Using Cardiovascular Magnetic Resonance Flow Measurements

Invasive hemodynamic studies have shown that nitric oxide (NO), a selective pulmonary vasodilator, can lower pulmonary vascular resistance in Fontan patients. Because oximetry-derived flow quantification may be unreliable, we sought to detect changes in blood flow within the Fontan circulation after inhalation of NO using cardiovascular magnetic resonance (CMR). Thirty-three patients (mean age 12.8 ± 7.0 years) after the Fontan procedure underwent CMR as part of their routine clinical assessment. Standard two-dimensional blood flow measurements were performed in the Fontan tunnel, superior vena cava (SVC) and ascending aorta (AAO) before and after inhalation of 40 ppm NO for 8-10 min. Systemic-to-pulmonary collateral (SPC) flow was calculated as AAO - (SVC + tunnel). Heart rate (82 ± 18 to 81 ± 18 bpm; p = 0.31) and transcutaneous oxygen saturations (93 ± 4 to 94 ± 3 %; p = 0.13) did not change under NO inhalation. AAO flow (3.23 ± 0.72 to 3.12 ± 0.79 l/min/m(2); p = 0.08) decreased, tunnel flow (1.58 ± 0.40 to 1.65 ± 0.46 l/min/m(2); p = 0.032) increased, and SVC flow (1.01 ± 0.39 to 1.02 ± 0.40 l/min/m(2); p = 0.50) remained unchanged resulting in higher total caval flow (Qs) (2.59 ± 0.58 to 2.67 ± 0.68 l/min/m(2); p = 0.038). SPC flow decreased significantly from 0.64 ± 0.52 to 0.45 ± 0.51 l/min/m(2) (p = 0.002) and resulted in a significant decrement of the Qp/Qs ratio (1.23 ± 0.23 to 1.15 ± 0.23; p = 0.001). Inhalation of NO in Fontan patients results in significant changes in pulmonary and systemic blood flow. The reduction in SPC flow is accompanied by a net increase in effective systemic blood flow suggesting beneficial effects of pulmonary vasodilators on cardiac output, tissue perfusion and exercise capacity.

Decision-Making for Surgery in the Management of Patients with Univentricular Heart

A series of technical refinements over the past 30 years, in combination with advances in perioperative management, have resulted in dramatic improvements in the survival of patients with univentricular heart. While the goal of single-ventricle palliation remains unchanged - normalization of the pressure and volume loads on the systemic ventricle, the strategies to achieve that goal have become more diverse. Optimal palliation relies on a thorough understanding of the changing physiology over the first years of life and the risks and consequences of each palliative strategy. This review describes how to optimize surgical decision-making in univentricular patients based on a current understanding of anatomy, physiology, and surgical palliation.