Real-Time Detection of Circulating Thrombi in an Extracorporeal Circuit Using Doppler Ultrasound: In-Vitro Proof of Concept Study.

BACKGROUND: Thromboembolic stroke continues to be by far the most common severe adverse event in patients supported with mechanical circulatory assist devices. Feasibility of using Doppler ultrasound to detect circulating thrombi in an extracorporeal circuit was investigated. METHODS: A mock extracorporeal circulatory loop of uncoated cardiopulmonary bypass tubing and a roller pump was setup. A Doppler bubble counter was used to monitor the mean ultrasound backscatter signal (MUBS). The study involved two sets of experiments. In Scenario 1, the circuit was sequentially primed with human blood components, and the MUBS was measured. In Scenario 2, the circuit was primed with heparinized fresh porcine blood, and the MUBS was measured. Fresh blood clots (diameter <1,000 microns, 1,000-5,000 microns, >5,000 microns) were injected into the circuit followed by protamine administration. RESULTS: In Scenario 1 (n = 3), human platelets produced a baseline MUBS of 1.5 to 3.5 volts/s. Addition of packed human red blood cells increased the baseline backscatter to 17 to 21 volts/s. Addition of fresh frozen plasma did not change the baseline backscatter. In Scenario 2 (n = 5), the blood-primed circuit produced a steady baseline MUBS. Injection of the clots resulted in abrupt and transient increase (range: 3-30 volts/s) of the baseline MUBS. Protamine administration resulted in a sustained increase of MUBS followed by circuit thrombosis. CONCLUSIONS: Doppler ultrasound may be used for real-time detection of circulating solid microemboli in the extracorporeal circuit. This technology could potentially be used to design safety systems that can reduce the risk of thromboembolic stroke associated with mechanical circulatory support therapy.

Mechanical support of pulmonary blood flow as a strategy to support the Norwood circulation-lumped parameter model study.

OBJECTIVES: We hypothesize that mechanical assistance of the pulmonary blood flow in a Norwood circulation can increase systemic blood flow and oxygen delivery. The aim of the study was to compare haemodynamics of an unassisted Norwood Blalock-Taussig shunt circulation with a mechanically assisted pulmonary flow-based Norwood circulation, using a lumped parameter computational model. METHODS: A neonatal circulatory lumped parameter model was developed to simulate a Norwood circulation with a 3.5-mm Blalock-Taussig shunt in a 3.5-kg neonate. A roller pump circulatory assist device with an inflow bladder was incorporated into the Norwood circulation to mechanically support the pulmonary circulation. Computer simulations were used to compare the haemodynamics of the assisted and unassisted circulations. Assisted and unassisted models with normal (56%) and reduced ejection fraction (30%) were compared. RESULTS: Compared to the unassisted Norwood circulation, the systemic flow in the assisted Norwood increased by 25% (ejection fraction = 56%) and 41% (ejection fraction = 30%). The central venous pressure decreased by up to 3 mmHg (both ejection fraction = 56% and ejection fraction = 30%) at a maximum pulmonary assist flow of 800 ml/min. Initiation of assisted pulmonary flow increased the arterial oxygen saturation by up to 15% and mixed venous saturation by up to 20%. CONCLUSIONS: This study demonstrates that an assisted pulmonary flow-based Norwood circulation has higher systemic flow and oxygen delivery compared to a standard Norwood Blalock-Taussig shunt circulation.

Compression Device-Assisted Extracorporeal Cardiopulmonary Resuscitation Cannulation in Pediatric Patients-A Simulation Study.

Background: Surgical neck cannulation for pediatric extracorporeal cardiopulmonary resuscitation (ECPR) requires multiple interruptions of manual chest compressions to facilitate the procedure. Effective uninterrupted CPR is essential to prevent neurological injury. We hypothesized that an automated chest compression device can be used to provide effective and uninterrupted chest compressions during pediatric neck ECPR cannulation. The feasibility of surgically cannulating the right carotid artery and right internal jugular vein in an infant during ongoing automated chest compressions was tested in a simulation study. Methods: A working prototype of a pediatric chest compression device was designed to provide automated chest compressions on an infant CPR manikin at the rate of 120 compressions/minute. A feedback device attached to the manikin was used to monitor the effectiveness of CPR. A synthetic artery, vein along with carotid sheath and skin was utilized to simulate surgical neck exploration. ECPR simulation was conducted using the compression device to provide chest compressions. Results: Four ECPR simulations were conducted during which vessel sparing (n = 2) and non-vessel sparing (n = 2) cannulation of the right internal carotid artery and right internal jugular vein were performed during ongoing mechanical chest compressions. All four cannulations were successfully performed without the need to interrupt chest compressions. Conclusions: In a simulated environment, pediatric ECPR neck cannulation with uninterrupted chest compressions may be accomplished using an automated chest compression device. The strategy of compression device-assisted ECPR cannulation requires further study and could potentially reduce the neurological complications of ECPR.

Emergency surgical stent retrieval following stent dislodgement during ductal stenting for hybrid palliation.

Stenting of the ductus arteriosus is part of the hybrid treatment of high-risk patients with hypoplastic left heart syndrome. Dislodgement of a ductal stent is a rare complication. We present challenges faced in successful surgical retrieval of a dislodged ductal stent in a high-risk infant undergoing hybrid palliation for hypoplastic left heart syndrome.

Circulatory support for prolonged electro-mechanical standstill in fulminant pediatric myocarditis.

Pediatric patients with fulminant myocarditis can rarely present with complete heart block with severe hemodynamic compromise, cardiac arrest and require circulatory support. Additionally, patients with cardiac dysfunction that require extracorporeal membrane oxygenation (ECMO) support sometimes develop cardiac stun or standstill. These factors are associated with extremely poor survival. We present a case of fulminant myocarditis presenting with dense heart block, no ventricular electrical activity resuscitated with ECMO that developed prolonged cardiac standstill. We present the clinical course, management including ECMO followed by biventricular assist devices, pacing and review supporting literature. We hope that the case will highlight challenges in management and decision making in such patients.

Patency of common carotid artery and internal jugular vein after a simple vessel sparing cannulation for extracorporeal membrane oxygenation support.

BACKGROUND: Common carotid artery and internal jugular vein are commonly cannulated for establishment of peripheral venoarterial extracorporeal membrane oxygenation (VA ECMO) support. We present our results of a vessel sparing cannulation technique for neck vessels, which helps maintain vessel patency after decannulation. METHODS: All patients who underwent ECMO, between January 2004 and January 2013 at a single center, were retrospectively reviewed. Follow up data for the patency of common carotid artery (CCA) and internal jugular vein (IJV) after decannulation were recorded. RESULTS: Twenty-four consecutive patients who were successfully decannulated after VA ECMO support who underwent vessel sparing cannulation were retrospectively reviewed. Follow up data were unavailable in 4 and 1 patient did not survive. Amongst the remaining 19 patients the median duration of ECMO support in the remaining was 7 (IQR; 4-10) days. Follow up studies documenting vessel patency were available for IJV in 18 patients and CCA in 14 patients. At a median follow up of 137days (IQR; 35-7240) 15 (78%) patients had patent IJVs and 14 (100%) patients had patent CCAs. CONCLUSION: The simple vessel sparing technique is effective in allowing restoration of the patency of the neck vessels after ECMO decannulation. LEVEL OF EVIDENCE: Case series with no comparison group (Level IV).

Optimal Timing for Elective Early Primary Repair of Tetralogy of Fallot: Analysis of Intermediate Term Outcomes.

BACKGROUND: We have previously demonstrated that early primary repair of tetralogy of Fallot with pulmonary stenosis (TOF) can be safely performed without increase in hospital resource utilization or compromise to surgical technical performance scores (TPS). We sought to identify the optimal timing for elective early primary repair of TOF with respect to intermediate-term reintervention. METHODS: Retrospective review of all patients with TOF undergoing elective primary repair between September 2004 and December 2013 was performed. Patients were stratified into reintervention group or no reintervention group. Multivariable Cox regression analysis identified independent predictors of reintervention. Youden's J-index in receiver operating characteristic analysis identified optimal age cutoff predictive of reintervention. Kaplan-Meier analysis with the log-rank test compared reintervention rates stratified by age and TPS. RESULTS: A total of 129 patients with median (interquartile range) age and weight of 78 days (56 to 111) and 5 kg (4.1 to 5.7), respectively, underwent primary repair. After a median (interquartile range) follow-up of 2.3 years (0.1 to 4.6), 18 patients (14%) required a total of 22 reinterventions. Youden's J-index revealed significantly lower risk of intermediate-term reintervention when repaired after 55 days of age (8% for >55 days old versus 31% for ≤55 days of age). Multivariable Cox regression identified age 55 days and younger (hazard ratio [HR] 4.5, 95% confidence interval [CI] 1.6 to 12.8, p = 0.004), valve sparing repair (HR 15.3, 95% CI 1.8 to 128.5, p < 0.001), residual right ventricular outflow tract (RVOT) gradient (HR 1.11, 95% CI 1.1 to 1.2, p < 0.001), and inadequate TPS (HR 21.5, 95% CI 7.4 to 63, p < 0.001) as independent predictors of overall intermediate-term reintervention. CONCLUSIONS: Elective repair in patients greater than 55 days of age, irrespective of size of the patient, can be safely performed without any increase in reintervention rates. Both residual peak RVOT gradient and TPS are effective in identifying patients at increased risk of reintervention.

Influence of Age and Weight on Technical Repair of Tetralogy of Fallot.

BACKGROUND: We have previously shown that early primary repair of tetralogy of Fallot can be performed without increased morbidity or resource utilization. The technical performance score (TPS) is a self-assessment tool used to identify patients at risk of poor postoperative outcomes. We hypothesized that adequate technical repair can be obtained regardless of the patient's preoperative age or size. METHODS: A retrospective review of all tetralogy of Fallot patients repaired between September 2004 and December 2013 was performed. The postoperative predischarge echocardiogram was reviewed to assign a TPS rating of optimal, adequate, or inadequate. The TPS groups were compared by univariate analysis using the Kruskal-Wallis test for continuous variables and χ(2) analysis for categoric variables. Multivariable logistic regression analysis was performed to identify independent predictors of inadequate TPS. RESULTS: Among 167 patients (1 operative mortality), TPS was optimal in 88, adequate in 62, and inadequate in 17. Patients with worse TPS had longer ventilation time (p = 0.031), hospital length of stay (p = 0.036), and higher hospital charges (p = 0.005). Multivariable regression analysis revealed discontinuous branch pulmonary arteries (odds ratio 18.24, 95% confidence interval: 1.42 to 234, p = 0.015) as the only independent predictor of inadequate TPS. Younger age at repair (p = 0.245) and smaller weight (p = 0.260) were not associated with inadequate TPS. CONCLUSIONS: Technical adequacy of tetralogy of Fallot repair is affected by anatomic subsets (discontinuous branch pulmonary arteries) and not by the patient's age or size. Worse TPS is associated with higher postoperative morbidity and hospital charges. Younger age and size should not be a deterrent for early primary repair.

Early primary repair of tetralogy of Fallot does not lead to increased postoperative resource utilization.

BACKGROUND: Although early primary repair of tetralogy of Fallot has gained wider acceptance, there is some speculation that repair at a younger age may be associated with increased morbidity and resource utilization. METHODS: A retrospective review of all consecutive patients undergoing tetralogy of Fallot repair between September 2004 and December 2011 was performed. Primary end points were hospital charges, and surrogates of postoperative hospital resource utilization, including ventilation time, intensive care unit (ICU) stay, and hospital stay. The secondary end point was operative death. Logistic regression analysis was used to determine factors associated with increased postoperative hospital resource utilization. RESULTS: Among 164 patients in the study, there was 1 hospital death (0.6%). After excluding 9 patients who had palliative procedures before their repair, 155 comprised the primary repair group. Multivariate linear regression analysis revealed prematurity (p = 0.018), a nonelective operation (p < 0.001), and major extracardiac anomalies (p = 0.003) were independent predictors of increased postoperative hospital charges. Prematurity (p < 0.002), low birth weight (p = 0.047), and major extracardiac anomalies (p < 0.001) were significant predictors of increased ventilation time. Prematurity (p < 0.001), a nonelective operation (p < 0.001), and low birth weight (p = 0.048) significantly increased ICU length of stay. A nonelective operation (p = 0.025) and major extracardiac anomalies (p < 0.001) were predictors of an increased hospital stay. Younger age at repair was not associated with any increase in ventilation time, ICU stay, hospital stay, or with an increase in hospital charges. CONCLUSIONS: Extracardiac anomalies, prematurity, low birth weight, and nonelective surgical intervention are predictors of increased morbidity and increased hospital resource utilization and impose a significant cost burden to the care of these patients. Early primary repair of tetralogy of Fallot can be safely performed without any increase in morbidity or increased hospital resource utilization.

Tricuspid atresia with aortopulmonary window: challenges in achieving a balanced circulation.

Tricuspid atresia and aortopulmonary window are rare congenital cardiac anomalies. The occurrence of both these anomalies in the same patient is extremely rare, with only 1 case reported in the literature. We report the surgical management of one such patient and discuss the management issues with respect to Stage 1 single ventricle palliation.

Aorto-left ventricular tunnel: uncommon site of origin and management.

Cases of aorto-ventricular tunnel involving the right ventricle and more commonly, the left ventricle have been described. The site of origin is located above the right coronary cusp and occasionally, the left. We describe an aorto-left ventricular tunnel in a 16-year-old girl, with aneurysmal expansion into the right ventricular outflow tract. Its aortic origin was above the commissure of the right and noncoronary cusps of the aortic valve.

Pulmonary artery bypass for in-stent stenosis following angioplasty for isolated pulmonary Takayasu arteritis.

Pulmonary artery (PA) stenosis due to Takayasu Arteritis (TA) is usually managed by angioplasty techniques. We present a patient with isolated PA stenosis with TA with in-stent stenosis. The surgical management and pathophysiology of this disease are reviewed.

A technique for repair of atrioventricular canal defect in dextrocardia.

Congenital heart disease with dextrocardia, situs solitus, is not uncommonly seen in paediatric cardiac surgery. An approach through the right atrium for correction of associated cardiac anomalies is needed in most of these cases. We present a technique for operating on this subset of patients wherein the heart can be displaced into the left pleural space allowing for surgery in an anatomical orientation that is familiar to the surgeon and emphasize the precautions to be taken following surgery.