Morphology and Function of the Lymphatic Vasculature in Patients With a Fontan Circulation.

BACKGROUND: The Fontan procedure has revolutionized the treatment of univentricular hearts. However, it is associated with severe complications such as protein-losing enteropathy, plastic bronchitis, and peripheral edema that may involve the lymphatic circulation. We aimed to assess lymphatic function and morphology in patients with a univentricular circulation. METHODS: The functional state of lymphatic vessels in the lower extremities of patients with a Fontan circulation (n=10) was investigated using the novel technique near-infrared fluorescence imaging and compared with an age-, sex-, and weight-matched control group of healthy volunteers (n=10). The lymphatic morphology was described using T2-weighted magnetic resonance imaging, and microvascular permeability was estimated by strain gauge plethysmography. RESULTS: The Fontan patients had 17% lower lymphatic pumping pressure (50±3.1 mm Hg) compared with controls (60±2.8 mm Hg; P=0.0341) and a 62% higher contraction frequency (0.8±0.1 min-1) compared with the healthy controls (0.5±0.1 min-1; P=0.0432). Velocity by which the lymph is moved and refill time after manual emptying of the lymphatic vessels showed no differences between the 2 groups. The thoracic duct was elongated 10% ( P=0.0409) and with an abnormal course in the Fontan patients compared with normal. No difference in microvascular permeability was found between the 2 groups. CONCLUSIONS: Patients with a Fontan circulation have an impaired lymphatic pumping capacity and morphologically changed thoracic duct. Our results indicate a challenged lymphatic vasculature in the Fontan circulation and may play a role in the pathogenesis of the complications that are seen in Fontan patients. CLINICAL TRIAL REGISTRATION: URL: https://www.clinicaltrials.gov . Unique identifier: NCT03379805.

Cardiothoracic surgery.

Conjoined twins often have complex cardiac anomalies associated with other congenital defects. The correct cardiac diagnosis delineates the degree of cardiac fusion and the feasibility of separation. The outcome in twins with fused hearts remains poor.

A multiscale model for the study of cardiac biomechanics in single-ventricle surgeries: a clinical case.

Complex congenital heart disease characterized by the underdevelopment of one ventricular chamber (single ventricle (SV) circulation) is normally treated with a three-stage surgical repair. This study aims at developing a multiscale computational framework able to couple a patient-specific three-dimensional finite-element model of the SV to a patient-specific lumped parameter (LP) model of the whole circulation, in a closed-loop fashion. A sequential approach was carried out: (i) cardiocirculatory parameters were estimated by using a fully LP model; (ii) ventricular material parameters and unloaded geometry were identified by means of the stand-alone, three-dimensional model of the SV; and (iii) the three-dimensional model of SV was coupled to the LP model of the circulation, thus closing the loop and creating a multiscale model. Once the patient-specific multiscale model was set using pre-operative clinical data, the virtual surgery was performed, and the post-operative conditions were simulated. This approach allows the analysis of local information on ventricular function as well as global parameters of the cardiovascular system. This methodology is generally applicable to patients suffering from SV disease for surgical planning at different stages of treatment. As an example, a clinical case from stage 1 to stage 2 is considered here.

Performance monitoring of the arterial switch operation: a moving target.

OBJECTIVES: Twenty years ago our institution published an analysis of a cluster of failures associated with the arterial switch operation (ASO). The concept of 'near miss' was explored to detect warning signs of suboptimal performance. The aim of the current study was to review the parameters best suited to monitoring early ASO outcomes in the modern setting and re-examine the concept of near misses as failure equivalents. METHODS: All ASOs performed in our institution between 1983 and 2012 were reviewed. The experience was divided into three eras (1983-92, 1993-2002 and 2003-12). The cumulative sum graphic for sequential monitoring was used for early mortality. The need to re-establish cardiopulmonary bypass (CPB), CPB time >240 min and extracorporeal membrane oxygenation (ECMO) were explored as variables of near misses. RESULTS: The cohort consisted of 606 patients. The 30-day mortality rate was 23% (n = 29) in Era 1, 6% (n = 14) in Era 2 and 1% (n = 3) in Era 3. There were further 4, 8 and 6 deaths between 30 and 90 days in the three eras, respectively. In Era 3, the majority of deaths occurred between 30 and 90 days. In the current era, ECMO and CPB time >240 min as a marker of near miss was associated with an increased risk of death both within 30 days and 90 days after ASO. CONCLUSIONS: The 30-day outcomes of ASO have significantly improved over the last 30 years. As life-saving mechanical support after surgery has been implemented more often, an extended 90-day window of reporting can offer a more realistic outcome indicator of performance.

Human lymphatic vessel contractile activity is inhibited in vitro but not in vivo by the calcium channel blocker nifedipine.

Calcium channel blockers (CCB) are widely prescribed anti-hypertensive agents. The commonest side-effect, peripheral oedema, is attributed to a larger arterial than venous dilatation causing increased fluid filtration. Whether CCB treatment is detrimental to human lymphatic vessel function and thereby exacerbates oedema formation is unknown. We observed that spontaneous lymphatic contractions in isolated human vessels (thoracic duct and mesenteric lymphatics) maintained under isometric conditions were inhibited by therapeutic concentrations (nanomolar) of the CCB nifedipine while higher than therapeutic concentrations of verapamil (micromolar) were necessary to inhibit activity. Nifedipine also inhibited spontaneous action potentials measured by sharp microelectrodes. Furthermore, noradrenaline did not elicit normal increases in lymphatic vessel tone when maximal constriction was reduced to 29.4 ± 4.9% of control in the presence of 20 nmol l(-1) nifedipine. Transcripts for the L-type calcium channel gene CACNA1C were consistently detected from human thoracic duct samples examined and the CaV1.2 protein was localized by immunoreactivity to lymphatic smooth muscle cells. While human lymphatics ex vivo were highly sensitive to nifedipine, this was not apparent in vivo when nifedipine was compared to placebo in a randomized, double-blinded clinical trial: conversely, lymphatic vessel contraction frequency was increased and refill time was faster despite all subjects achieving target nifedipine plasma concentrations. We conclude that human lymphatic vessels are highly sensitive to nifedipine in vitro but that care must be taken when extrapolating in vitro observations of lymphatic vessel function to the clinical situation, as similar changes in lymphatic function were not evident in our clinical trial comparing nifedipine treatment to placebo.

Neither age at repair nor previous palliation affects outcome in tetralogy of Fallot repair.

OBJECTIVES: The study aimed to evaluate the results following complete repair of tetralogy of Fallot (TOF) in relation to age at surgery and to assess the role of palliation in the current era. METHODS: A retrospective review of 251 consecutive patients with TOF repaired between 2003 and 2011 at the Great Ormond Street Hospital was performed. Children were divided into two groups: Group A, younger than 6 months (n = 78) and B, older than 6 months (n = 173). Early clinical outcomes and reoperation/reintervention rates were studied as well as indication for a palliation. RESULTS: There was 1 (0.4%) early and 1 (0.4%) late death after a median follow-up time of 4.5 years. Forty-three patients (17%) underwent repair after initial palliation with inter-stage mortality of 5%. Groups A and B were similar in terms of surgical approach, postoperative complications and length of stay. Significant differences were found in terms of more frequent use of a transannular patch (P = 0.05), longer surgeries (P = 0.02) and a greater proportion of palliated patients (P = 0.002) in older patients. There was no difference in rates of reoperation/reintervention between groups and following both primary and staged repair. Palliated patients were more symptomatic (duct-dependent pulmonary blood flow; P < 0.01, cyanotic spells; P < 0.01), had more extracardiac/genetic anomalies (P < 0.01), coronary anomalies (P = 0.015) and significantly smaller pulmonary annulus, right pulmonary artery (RPA) and left pulmonary artery (LPA) Z-scores (P < 0.01 for all). CONCLUSION: Age at complete repair was not linked to early clinical outcome or reoperation/reintervention rate. Palliative procedures postponed the timing of complete repair, but did not increase the reintervention rate.

Rapid 2-stage Norwood I for high-risk hypoplastic left heart syndrome and variants.

OBJECTIVES: Preoperative comorbidities (PCMs) are known risk factors for Norwood stage I (NW1). We tested the hypothesis that short-term bilateral pulmonary arterial banding (bPAB) before NW1 could improve the prognosis of these high-risk patients. METHODS: From January 2006 to October 2011, 17 high-risk patients with hypoplastic left heart syndrome (defined as having ≥4 of the following PCMs: prolonged mechanical ventilation; older age; sepsis; necrotizing enterocolitis; hepatic, renal, or heart failure; coagulopathy; pulmonary edema; high inotropic requirements; anasarca; weight <2.5 kg; and cardiac arrest) were identified. In addition to conventional treatment of PCMs, they underwent bPAB before NW1. bPAB was undertaken with Silastic slings and secured with ligaclips to a luminal diameter of approximately 3.5 to 4.0 mm. The patency of the ductus arteriosus was maintained with prostaglandin. NW1 was performed using a modified, right Blalock-Taussig shunt at a median interval of 8 days after bPAB. The data from these patients were retrospectively reviewed, and the 30-day mortality and 1-year survival were compared with the hypoplastic left heart syndrome population who underwent primary NW1 with <3 PCMs in the same period. RESULTS: Of the bPAB patients, 5 (29.4%) died before NW1. All had ≥5 PCMs. Twelve patients (70.6%) survived to undergo NW1. One early death occurred after NW1 (8.3%). The 1-year survival rate for high-risk patients who underwent NW1 was 66.7%. The early mortality and 1-year survival for the 130 patients with <3 PCMs was 10% and 80%, respectively. CONCLUSIONS: Optimizing the balance between the pulmonary and systemic blood flow with a short period of bPAB and ductal patency can improve the perioperative conditions of high-risk patients before NW1. Those who survived bPAB and underwent NW1 had early mortality and 1-year survival comparable to the standard risk category, despite the severity of their initial condition. A rapid 2-stage NW1 strategy with bPAB and prostaglandin to maintain ductal patency can avoid the risks of suboptimal palliation and vascular injuries associated with hybrid procedures.

Reduced ascending aorta distensibility relates to adverse ventricular mechanics in patients with hypoplastic left heart syndrome: noninvasive study using wave intensity analysis.

OBJECTIVE: To evaluate the aortic arch elastic properties and ventriculoarterial coupling efficiency in patients with single ventricle physiology, with and without a surgically reconstructed arch. METHODS: We studied 21 children with single ventricle physiology after bidirectional superior cavopulmonary surgery: 10 with hypoplastic left heart syndrome, who underwent surgical arch reconstruction, and 11 with other types of single ventricle physiology but without arch reconstruction. All children underwent pre-Fontan magnetic resonance imaging. No patient exhibited aortic recoarctation. Data on aortic wave speed, aortic distensibility and wave intensity profiles were all extracted from the magnetic resonance imaging studies using an in-house-written plug-in for the Digital Imaging and Communications in Medicine viewer OsiriX. RESULTS: Children with hypoplastic left heart syndrome had significantly greater wave speed (P = .002), and both stiffer (P = .004) and larger (P < .0001) ascending aortas than the patients with a nonreconstructed arch. Aortic distensibility was not influenced by ventricular stroke volume but depended on a combination of increased aortic diameter and abnormal wall mechanical properties. Those with hypoplastic left heart syndrome had a lower peak wave intensity and reduced energy carried by the forward compression and the forward expansion waves, even after correction for stroke volume, suggesting an abnormal systolic and diastolic function. Lower wave energy was associated with an increased aortic diameter. CONCLUSIONS: Using a novel, noninvasive technique based on image analysis, we have demonstrated that aortic arch reconstruction in children with hypoplastic left heart syndrome is associated with reduced aortic distensibility and unfavorable ventricular-vascular coupling compared with those with single ventricle physiology without aortic arch reconstruction.

Midterm follow-up of arterial switch operation for transposition of the great arteries with intact ventricular septum and left-ventricular outflow tract obstruction.

OBJECTIVE: We report the mid-term follow-up of patients, who underwent arterial switch operation (ASO) for transposition of the great arteries (TGA) with intact ventricular septum and left-ventricular outflow tract obstruction (LVOTO) over a 10-year period from 2000 to 2009. METHODS: Thirteen TGA patients (3.9% of our ASO cohort) with intact ventricular septum and LVOTO underwent ASO. LVOTO was defined as pulmonary valve z-score ≤ -2.0 (n=3) or peak LVOT gradient ≥40 mmHg with (n=7) or without (n=3) anatomic subvalvar stenosis on echocardiography. Median age and weight were 14 days (range, 7-130 days) and 3.2 kg (range, 2.1-4.6 kg). The LVOT abnormalities included fibromuscular narrowing (n=5) and atrioventricular valve-related findings (n=5). LVOT clearance was achieved by resection of accessory mitral tissue (n=2) only. RESULTS: Follow-up was 100% complete. There were no early or late deaths. Freedom from re-operation for neo-aortic valve regurgitation and/or LVOTO was 100% at a median follow-up of 38 months (range, 6-115 months). All patients had functional status appropriate for their age. Three patients had mild aortic regurgitation. The median Doppler estimated LVOT systolic gradient was 12 mmHg (range, 0-18 mmHg) for the entire cohort at the latest follow-up. CONCLUSIONS: Mid-term outcomes of ASO for a highly selected group of patients with pulmonary valve annulus z-score ≤ -2.0 ≥ -0.4, resectable organic LVOTO, and dynamic peak LVOT gradient ≥40 mmHg remain satisfactory, with a need for long-term follow-up.

Outcomes and re-interventions after one-stage repair of transposition of great arteries and aortic arch obstruction.

OBJECTIVES: One-stage repair of transposition of great arteries (TGA) and aortic arch obstruction (AAO) is currently advocated, but carries formidable surgical challenges. This report presents our experience and re-interventions for residual lesions over the last 10 years. METHODS: Twenty-two patients (19.5 ± 42.4 days; range 2-206; median 10 days, 3.5 ± 0.6 kg) diagnosed with TGA (nine patients) or double outlet right ventricle (DORV) (13 patients) and AAO underwent one-stage repair. Of the nine TGA patients (two with intact ventricular septum), AAO were: two patients hypoplastic arch, one patient discrete coarctation, four patients hypoplastic arch with coarctation and two patients interrupted aortic arch. The 13 DORV patients were all of Taussig-Bing type and one showed multiple ventricular septal defects (VSDs). The degree of AAO ranged from hypoplastic arch in five patients, coarctation two patients, combined four patients and interrupted aortic arch (IAA) two patients. Arterial switch with Lecomte ± VSD repair was performed during cooling, and aortic arch repair was performed under deep hypothermic circulatory arrest (DHCA) (35 ± 14 min at 16.9 ± 0.7 °C). Our preference was to use homograft patch-plasty for arch and direct end-to-side anastomosis for coarctation repair. Aortic-cross-clamp time was 124 ± 24 min and cardiopulmonary bypass (CPB) time 215 ± 84 min. RESULTS: Early survival was 19/22 (86%) up to 30 days without mortality in the second half of our series. Three patients required extracorporeal membrane oxygenation (ECMO) support and renal support was needed in three and preferred permanent pace maker (PPM) implantation in two. Length of stay was 21.9 ± 22.1 days. There was one late death and overall survival was 18/22 (82%) for the follow-up period of 4.8 years (0.2-9.8 years). Eight patients (44%) required re-intervention for re-coarctation. Four patients required right ventricular outflow tract (RVOT)/pulmonary artery re-interventions. At follow-up, there was no requirement for aortic valve replacement, residual VSD closure and no evidence of ventricular dysfunction. CONCLUSIONS: One-stage repair of TGA/DORV and AAO can be performed safely with a good survival rate. Three important lessons that we have learnt are as follows: (1) the subpulmonary VSD may have a perimembraneous component, (2) late re-coarctation is not infrequent and (3) late residual right-sided cardiac lesions remain an issue in complex TGA repair.

Human thoracic duct in vitro: diameter-tension properties, spontaneous and evoked contractile activity.

The current study characterizes the mechanical properties of the human thoracic duct and demonstrates a role for adrenoceptors, thromboxane, and endothelin receptors in human lymph vessel function. With ethical permission and informed consent, portions of the thoracic duct (2-5 cm) were resected and retrieved at T(7)-T(9) during esophageal and cardia cancer surgery. Ring segments (2 mm long) were mounted in a myograph for isometric tension (N/m) measurement. The diameter-tension relationship was established using ducts from 10 individuals. Peak active tension of 6.24 +/- 0.75 N/m was observed with a corresponding passive tension of 3.11 +/- 0.67 N/m and average internal diameter of 2.21 mm. The equivalent active and passive transmural pressures by LaPlace's law were 47.3 +/- 4.7 and 20.6 +/- 3.2 mmHg, respectively. Subsequently, pharmacology was performed on rings from 15 ducts that were normalized by stretching them until an equivalent pressure of 21 mmHg was calculable from the wall tension. At low concentrations, norepinephrine, endothelin-1, and the thromboxane-A(2) analog U-46619 evoked phasic contractions (analogous to lymphatic pumping), whereas at higher contractions they induced tonic activity (maximum tension values of 4.46 +/- 0.63, 5.90 +/- 1.4, and 6.78 +/- 1.4 N/m, respectively). Spontaneous activity was observed in 44% of ducts while 51% of all the segments produced phasic contractions after agonist application. Acetylcholine and bradykinin relaxed norepinephrine preconstrictions by approximately 20% and approximately 40%, respectively. These results demonstrate that the human thoracic duct can develop wall tensions that permit contractility to be maintained across a wide range of transmural pressures and that isolated ducts contract in response to important vasoactive agents.

Four decades of Fontan palliation.

The Fontan palliation was introduced in 1968 to treat cardiac malformations unsuitable for biventricular repair. This procedure has transformed the surgical management of congenital heart disease. In this Review, we reflect on the outcomes and clinical problems associated with this unique circulation after more than 40 years of experience. We also summarize the evolution of the Fontan procedure, highlight the long-term clinical issues and their management, and consider future expectations of a circulation driven by a single ventricle with the systemic and pulmonary blood flow in series rather than in parallel.

Evolution of the Fontan-Kreutzer procedure.

The surgical techniques used to construct the Fontan-Kreutzer circulation have evolved considerably since the initial reports. In the early years, it was thought that a power source other than the main ventricular chamber was useful or even necessary to serve the pulmonary circulation. Better understanding of the physiology of the Fontan-Kreutzer circulation has led to an understanding that avoidance of flow disturbances and energy losses in the surgically constructed pathways is critically important. In vitro studies and clinical investigations of flow dynamics led to the introduction of the total cavopulmonary connection, or total cavopulmonary connections, designed to minimize flow disturbances and the resultant energy losses. Other important surgical modifications include staging with a superior cavopulmonary connection and creation of a fenestration. These innovations have resulted in extension of the Fontan-Kreutzer procedure to the management of complex univentricular hearts and, in particular, the management of hypoplastic left heart syndrome. There have been significant improvements of early mortality and morbidity following the Fontan-Kreutzer procedure. Yet it is important to recognize that there is continuing late attrition and morbidity for patients with the Fontan-Kreutzer circulation.

Functional outcomes after the Ross (pulmonary autograft) procedure assessed with magnetic resonance imaging and cardiopulmonary exercise testing.

OBJECTIVE: To assess autograft, homograft and ventricular function, as well as exercise capacity, in adult patients who have undergone the Ross procedure. SETTING: Single centre paediatric and adult congenital heart disease unit. Patients 45 subjects (24.6 years, range 16.9-52.2 years) who underwent the Ross procedure between 1994 and 2006 (8.1 years after the Ross operation, range 2.0-14.0 years). Interventions Cardiovascular magnetic resonance imaging, echocardiography and cardiopulmonary exercise testing. MAIN OUTCOME MEASURES: Autograft and homograft stenosis, and regurgitation. Autograft size. Biventricular function, scar volume and exercise capacity. RESULTS: Mean autograft regurgitation was 6.8%+/-8.3% (trivial regurgitation) and diameter was 40.0+/-7.0 mm. Mean homograft velocity was 2.4+/-0.6 m/s (mild-moderate stenosis) and regurgitation was 6.1%+/-8.3% (trivial regurgitation). Biventricular systolic function was normal (LV EF 63.1+/-6.4% and RV EF 60.1%+/-7.6%). In 38% of cases there was evidence of LV scar, mostly noted within the inter-ventricular septum. The mean exercise capacity achieved was 87%+/-22% of predicted. There was no correlation between exercise capacity and ventricular function or scar. CONCLUSION: This study demonstrates minor autograft and homograft dysfunction in the majority of patients after the Ross procedure, associated with good ventricular function and exercise capacity. In addition, minor scar was present in a third of patients with no functional consequences.

Evaluation and stages of surgical innovations.

Surgical innovation is an important part of surgical practice. Its assessment is complex because of idiosyncrasies related to surgical practice, but necessary so that introduction and adoption of surgical innovations can derive from evidence-based principles rather than trial and error. A regulatory framework is also desirable to protect patients against the potential harms of any novel procedure. In this first of three Series papers on surgical innovation and evaluation, we propose a five-stage paradigm to describe the development of innovative surgical procedures.

No surgical innovation without evaluation: the IDEAL recommendations.

Surgery and other invasive therapies are complex interventions, the assessment of which is challenged by factors that depend on operator, team, and setting, such as learning curves, quality variations, and perception of equipoise. We propose recommendations for the assessment of surgery based on a five-stage description of the surgical development process. We also encourage the widespread use of prospective databases and registries. Reports of new techniques should be registered as a professional duty, anonymously if necessary when outcomes are adverse. Case series studies should be replaced by prospective development studies for early technical modifications and by prospective research databases for later pre-trial evaluation. Protocols for these studies should be registered publicly. Statistical process control techniques can be useful in both early and late assessment. Randomised trials should be used whenever possible to investigate efficacy, but adequate pre-trial data are essential to allow power calculations, clarify the definition and indications of the intervention, and develop quality measures. Difficulties in doing randomised clinical trials should be addressed by measures to evaluate learning curves and alleviate equipoise problems. Alternative prospective designs, such as interrupted time series studies, should be used when randomised trials are not feasible. Established procedures should be monitored with prospective databases to analyse outcome variations and to identify late and rare events. Achievement of improved design, conduct, and reporting of surgical research will need concerted action by editors, funders of health care and research, regulatory bodies, and professional societies.

Challenges in evaluating surgical innovation.

Research on surgical interventions is associated with several methodological and practical challenges of which few, if any, apply only to surgery. However, surgical evaluation is especially demanding because many of these challenges coincide. In this report, the second of three on surgical innovation and evaluation, we discuss obstacles related to the study design of randomised controlled trials and non-randomised studies assessing surgical interventions. We also describe the issues related to the nature of surgical procedures-for example, their complexity, surgeon-related factors, and the range of outcomes. Although difficult, surgical evaluation is achievable and necessary. Solutions tailored to surgical research and a framework for generating evidence on which to base surgical practice are essential.