Predicting Hemodynamic Performance of Fontan Operation for Glenn Physiology using Computational Fluid Dynamics: Ten Patient-specific Cases

Single ventricle hearts have only one ventricle that can pump blood effectively and the treatment requires three stages of operations to reconfigure the heart and circulatory system. At the second stage, Glenn procedure is performed to connect superior vena cava (SVC) to the pulmonary arteries (PA). For the third and most complex operation, called Fontan, an extracardiac conduit is used to connect inferior vena cava (IVC) to the PL and thereafter no deoxygenated blood goes to the heart. Predicting Hemodynamic Performance of Fontan Operation using computational fluid dynamics (CFD) is hypothesized to improve outcomes and optimize this treatment planning in children with single-ventricle heart disease. An important reason for this surgical planning is to reduce the development of pulmonary arteriovenous malformations (PAVM) and the need to perform Fontan revisions. The purpose of this study was to develop amodel for Fontan surgical planning and use this model to compare blood circulation in two designed graft types of Fontan operation known as T-shape and Y-graft. The functionality of grafts was compared in terms of power loss (PL) and hepatic flow distribution (HFD), a known factor in PAVM development. To perform this study, ten single-ventricle children with Glenn physiology were included and a CFD model was developed to estimate the blood flow circulation to the left and right pulmonary arteries. The estimated blood flow by CFD was compared with that measured by cardiovascular magnetic resonance. Results showed that there was an excellent agreement between the net blood flow in the right and left pulmonary arteries computed by CFD and CMR (ICC= 0.98, P-value ≥0.21). After validating the accuracy of each CFD model, Fontan operations using T-shape and Y-graft conduits were performed in silico for each patient and the developed CFD model was used to predict the post-surgical PL and HFD. We found that the PL in the Y-graft was significantly lower than in the T-shape (P-value ≤0.001) and HFD was significantly better balanced in Y-graft compared to the T-shape (P-value=0.004).

Hospital costs and cost implications of co-morbid conditions for patients with single ventricle in the period through to Fontan completion

BACKGROUND

Patients undergoing palliative surgeries for single-ventricle conditions are affected by multiple comorbidities or non-cardiac conditions. The prevalence, costs and the cost implications of these conditions have not been assessed.

METHODS

Administrative costing records from four hospitals in Australia and New Zealand were linked with the Fontan registry database to analyze the inpatient resource use for co-morbid or non-cardiac conditions. Inpatient costing records from the birth year through to Fontan completion were available for 156 patients. The most frequent primary diagnoses were hypoplastic left heart syndrome (33%), double inlet left ventricle (13%), and tricuspid atresia (12%).

RESULTS

During the staged surgical treatment period, children had a mean of 10±6 inpatient admissions and spent 85±64days in hospital. Among these admissions, 3±5 were for non-cardiac conditions, totaling 21±41 inpatient days. Whilst cardiac surgeries were the major reason for resource use (77% of the total cost), other cardiac care that is not surgical contributed 5% and non-cardiac admissions 18% of the total cost. The three most prevalent non-cardiac diagnostic admission categories were 'Respiratory system', 'Digestive system', and 'Ear, nose, mouth and throat', affecting 28%, 21% and 34% of the patients respectively. Multivariate regression estimated that admissions for each of these categories resulted in an increased cost of $34,563 (P=0.08), $52,438 (P=0.05) and $10,525 (P=0.53) per patient respectively for the staged surgical treatment period.

CONCLUSIONS

Non-cardiac admissions for single-ventricle patients are common and have substantial resource implications. Further research assessing the causes of admission and extent to which admissions are preventable is warranted.

Single institution experience with the Ladd’s procedure in patients with heterotaxy and stage I palliated single-ventricle

AIM: To investigate and describe our current institutional management protocol for single-ventricle patients who must undergo a Ladd’s procedure.

METHODS: We retrospectively reviewed the charts of all patients from January 2005 to March 2014 who were diagnosed with heterotaxy syndrome and an associated intestinal rotation anomaly who carried a cardiac diagnosis of functional single ventricle and were status post stage I palliation. A total of 8 patients with a history of stage I single-ventricle palliation underwent Ladd’s procedure during this time period. We reviewed each patients chart to determine if significant intraoperative or post-operative morbidity or mortality occurred. We also described our protocolized management of these patients in the cardiac intensive care unit, which included pre-operative labs, echocardiography, milrinone infusion, as well as protocolized fluid administration and anticoagulation regimines. We also reviewed the literature to determine the reported morbidity and mortality associated with the Ladd’s procedure in this particular cardiac physiology and if other institutions have reported protocolized care of these patients.

RESULTS: A total of 8 patients were identified to have heterotaxy with an intestinal rotation anomaly and single-ventricle heart disease that was status post single ventricle palliation. Six of these patients were palliated with a Blaylock-Taussig shunt, one of whom underwent a Norwood procedure. The two other patients were palliated with a stent, which was placed in the ductus arteriosus. These eight patients all underwent elective Ladd’s procedure at the time of gastrostomy tube placement. Per our protocol, all patients remained on aspirin prior to surgery and had no period where they were without anticoagulation. All patients remained on milrinone during and after the procedure and received fluid administration upon arrival to the cardiac intensive care unit to account for losses. All 8 patients experienced no intraoperative or post-operative complications. All patients survived to discharge. One patient presented to the emergency room two months after discharge in cardiac arrest and died due to bowel obstruction and perforation.

CONCLUSION: Protocolized intensive care management may have contributed to favorable outcomes following Ladd’s procedure at our institution.

Executive Function in Children and Adolescents with Critical Cyanotic Congenital Heart Disease

Children and adolescents with critical cyanotic congenital heart disease (CHD) are at risk for deficits in aspects of executive function (EF). The primary aim of this investigation was to compare EF outcomes in three groups of children/adolescents with severe CHD and controls (ages 10-19 years). Participants included 463 children/adolescents with CHD [dextro-transposition of the great arteries (TGA), n=139; tetralogy of Fallot (TOF), n=68; and, single-ventricle anatomy requiring Fontan procedure (SVF), n=145] and 111 controls, who underwent laboratory and informant-based evaluation of EF skills. Rates of EF impairment on D-KEFS measures were nearly twice as high for CHD groups (75-81%) than controls (43%). Distinct EF profiles were documented between CHD groups on D-KEFS tasks. Deficits in flexibility/problem-solving and verbally mediated EF skills were documented in all three CHD groups; visuo-spatially mediated EF abilities were impaired in TOF and SVF groups, but preserved in TGA. Parent, teacher, and self-report ratings on the BRIEF highlighted unique patterns of metacognitive and self-regulatory concerns across informants. CHD poses a serious threat to EF development. Greater severity of CHD is associated with worse EF outcomes. With increased understanding of the cognitive and self-regulatory vulnerabilities experienced by children and adolescents with CHD, it may be possible to identify risks early and provide individualized supports to promote optimal neurodevelopment.

Palliative arterial switch as first-line treatment before the fontan procedure in patients with single-ventricle physiology and subaortic stenosis

INTRODUCTION AND OBJECTIVES

There are several techniques for the palliative treatment of patients with single-ventricle physiology, ventriculoarterial discordance and subaortic stenosis. The Fontan procedure relies on optimal initial palliation to avoid the development of subaortic stenosis (as well as ventricular hypertrophy and diastolic dysfunction).

METHODS

We present seven patients with single-ventricle physiology, transposition of the great arteries and subaortic stenosis, with low systemic output and high pulmonary flow, aged 21 to 383 days (median, 75) and weighing between 3.4 and 9.6kg (median, 4.2). All were treated with a palliative arterial switch, thus "switching" their subaortic stenosis to subpulmonary stenosis. Six patients also underwent aortic arch surgery, 4 an atrial septectomy, and 1 a subaortic membrane resection.

RESULTS

One patient died after surgery, another developed recoarctation, which was treated with an angioplasty, 3 patients reached the Glenn stage and 2 the Fontan stage. All had good ventricular function.

CONCLUSIONS

A palliative switch is an effective initial treatment for single-ventricle physiology with transposition of the great arteries and subaortic stenosis. This complex initial technique produces good results and allows the patient to progress to the Glenn or Fontan stage.