Does the pattern of bicuspid aortic valve leaflet fusion determine the success of the Ross procedure?

BACKGROUND: In addition to being associated with aortopathy, a bicuspid aortic valve (BAV) has been posed to be a risk factor for the dilation of the pulmonary autograft in the aortic position. The aim of this study is to assess the association between the subtype of native aortic valve leaflet fusion (right and noncoronary leaflets [R/N] vs right and left leaflets [R/L]) and autograft dilation and valve dysfunction after the Ross procedure. METHODS: We performed a retrospective review of 43 patients with BAV who underwent a Ross procedure in our center from 1993 to 2013. Serial transthoracic echocardiography was used to measure changes in autograft and ascending aortic diameter over time. The aortic diameter was measured at four levels, and Z values were computed. Aortic dilation was defined as a Z value greater than 3. RESULTS: The mean age at the time of the Ross procedure was 13.5 ± 9.2 years. R/L was the most prevalent native aortic valve subtype (R/L, n = 26, 61% vs R/N, n = 17, 39%). PreRoss procedure, aortic dilation was more frequent in patients with R/N fusion (P = .02), whereas the initial aortic valve gradient and grade of aortic insufficiency (AI) did not differ between the subgroups. At follow-up, (mean = 9.6 ± 4.3 years) dilation of the autograft and ascending aorta was seen more often in patients with R/N leaflet fusion (P = .03). Conversely, the prevalence of more than moderate AI was significantly higher in patients with R/L leaflet fusion (P = .03). There was no significant difference between groups among numbers of late reintervention on the aortic valve or root (P = .75); however the type of intervention varied by morphologic subtype. Patients with R/L fusion underwent more aortic valve replacements (AVRs) while patients with R/N fusion underwent more valve-sparing aortic root replacements. CONCLUSIONS: After Ross procedure, both groups of patients were likely to have a combination of dilation of the aortic root and the tubular portion of the ascending aorta at follow-up. Patients with R/L fusion were more likely to have a prevalence of root dilation, while patients with R/N fusion were more likely to have tubular ascending aorta dilation. The R/L phenotype is associated with a slightly more rapid dilation at follow-up and is more likely to have postoperative autograft insufficiency. This information may serve to guide patient and procedure selection for AVR.

Continuous synthesis of high-entropy alloy nanoparticles by in-flight alloying of elemental metals.

High-entropy alloy (HEA) nanoparticles (NPs) exhibit unusual combinations of functional properties. However, their scalable synthesis remains a significant challenge requiring extreme fabrication conditions. Metal salts are often employed as precursors because of their low decomposition temperatures, yet contain potential impurities. Here, we propose an ultrafast (< 100 ms), one-step method that enables the continuous synthesis of HEA NPs directly from elemental metal powders via in-flight alloying. A high-temperature plasma jet ( > 5000 K) is employed for rapid heating/cooling (103 - 105 K s-1), and demonstrates the synthesis of CrFeCoNiMo HEA NPs ( ~ 50 nm) at a high rate approaching 35 g h-1 with a conversion efficiency of 42%. Our thermofluid simulation reveals that the properties of HEA NPs can be tailored by the plasma gas which affects the thermal history of NPs. The HEA NPs demonstrate an excellent light absorption of > 96% over a wide spectrum, representing great potential for photothermal conversion of solar energy at large scales. Our work shows that the thermal plasma process developed could provide a promising route towards industrial scale production of HEA NPs.

Repair of anomalous origin of right pulmonary artery from ascending aorta without cardiopulmonary bypass.

Anomalous origin of a pulmonary artery from the ascending aorta (AORPA) is a rare congenital cardiac malformation that needs prompt surgical repair; otherwise it is associated with poor prognosis. We describe 3 cases of AORPA that successfully underwent complete surgical correction without extracorporeal circulation.

The World Database for Pediatric and Congenital Heart Surgery "A Call to Service for North American Congenital Heart Surgery Programs".

The World Society for Pediatric and Congenital Heart Surgery has endorsed the establishment of an international platform for the exchange of knowledge and experience for those that treat patients with a congenital heart defect. On January 1, 2017, the release of the World Database for Pediatric and Congenital Heart Surgery opened a new era in evaluation of treatment with congenital heart defects. The contribution of data from countries with established congenital surgical databases will greatly enhance the efforts to provide the most accurate measure of overall surgical outcomes across the globe.

Role of Hydrogen in High-Yield Growth of Boron Nitride Nanotubes at Atmospheric Pressure by Induction Thermal Plasma.

We recently demonstrated scalable manufacturing of boron nitride nanotubes (BNNTs) directly from hexagonal BN (hBN) powder by using induction thermal plasma, with a high-yield rate approaching 20 g/h. The main finding was that the presence of hydrogen is crucial for the high-yield growth of BNNTs. Here we investigate the detailed role of hydrogen by numerical modeling and in situ optical emission spectroscopy (OES) and reveal that both the thermofluidic fields and chemical pathways are significantly altered by hydrogen in favor of rapid growth of BNNTs. The numerical simulation indicated improved particle heating and quenching rates (∼105 K/s) due to the high thermal conductivity of hydrogen over the temperature range of 3500-4000 K. These are crucial for the complete vaporization of the hBN feedstock and rapid formation of nanosized B droplets for the subsequent BNNT growth. Hydrogen is also found to extend the active BNNT growth zone toward the reactor downstream, maintaining the gas temperature above the B solidification limit (∼2300 K) by releasing the recombination heat of H atoms, which starts at 3800 K. The OES study revealed that H radicals also stabilize B or N radicals from dissociation of the feedstock as BH and NH radicals while suppressing the formation of N2 or N2+ species. Our density functional theory calculations showed that such radicals can provide faster chemical pathways for the formation of BN compared with relatively inert N2.

Pathophysiologic implications of the helical ventricular myocardial band: considerations for right ventricular restoration.

This chapter describes the structure/function relationships of the right ventricle (RV), and shows how the geometry of the helical ventricular myocardial band model defines spatial geometry of the free wall and septum that underlie dynamic action. Myocardial fiber orientation is the keynote to performance in health and disease. The transverse geometry of the RV free wall allows constriction (bellows-type motion), whereas oblique septal fiber orientation and midline septal position is essential for ventricular twisting, the vital mechanism for RV ejection against increased pulmonary vascular resistance. Therefore, the septum is considered "the lion or motor of RV performance." Distortion of such normal structure/function relationships underlies the pathophysiologic mechanisms of RV failure. Operative methods that restore normal myocardial fiber orientation are described to outline evolving surgical techniques for the surgical treatment of RV failure.

Pore size distributions of biodegradable polymer microparticles in aqueous environments measured by NMR cryoporometry.

NMR cryoporometry is a unique method permitting the investigation of pores in the microporous and mesoporous regimes for samples in aqueous environments. Here, we apply the technique to porous biodegradable polymer microparticles designed as devices for drug delivery in depot formulations. The results indicate that structural features too small to be captured in surface and fracture images obtained by SEM are able to be accessed using the technique, and that the evolution of pore structure can be studied for several days as the particles swell and degrade in the aqueous environment.

Atrial extracellular matrix remodeling and the maintenance of atrial fibrillation.

BACKGROUND: Remodeling occurs in both ventricle and atrium in dilated cardiomyopathy and heart failure. However, the alteration of atrial extracellular matrix components during remodeling and its effect on the electrical remodeling and atrial arrhythmia have never been explored. METHODS AND RESULTS: Atrial tissue samples of 53 explanted hearts from patients with dilated cardiomyopathy and end-stage heart failure who underwent heart transplantation were examined. Nineteen patients had permanent atrial fibrillation (PmAF), 18 had persistent AF (PsAF), and 16 had no documented AF (NAF). Sixteen donor left atria (LA) were used as controls (CNs). Western Blot analysis revealed a selective downregulation of tissue inhibitor of metalloproteinase (TIMP)-2 in PmAF and PsAF groups compared with the NAF and CN groups and an upregulation of atrial metalloproteinase (MMP)-2 that was most pronounced in the PmAF group followed by the PsAF and NAF groups. Immunofluorescent staining revealed that in the LA, type I collagen volume fraction (CVF-I) increased significantly in the PmAF group followed by the PsAF and NAF groups compared with that in CN. LA CVF-I significantly correlated with LA dimension and TIMP-2 to MMP-2 ratio. In the PsAF group, CVF-I/CVF-III ratio was significantly correlated with AF duration and the frequency of AF recurrence. CONCLUSIONS: Atrial extracellular matrix remodeling manifested by the selective downregulation of TIMP-2 along with upregulation of MMP-2 and CVF-I in the atrium is associated with the development of sustained atrial fibrillation in patients with cardiomyopathy and heart failure.

Results after transplantation using donor hearts with preexisting coronary artery disease.

OBJECTIVE: Cardiac allografts with coronary artery disease may permit a selective expansion of the donor pool. Twenty-two recipients who received donor hearts with mild to moderate coronary artery disease on angiography were reviewed. All donor organs had preserved left ventricle function on echocardiogram. METHODS: The procedure was explained to the patients in detail. All survivors have at least 1 year of follow-up. If the coronary arteries of the donor heart were significantly occluded, then the implanting surgeon performed coronary revascularization. Donors were allocated to patients facing imminent death (group I, n = 4) or to those who would otherwise not have been transplanted (group II, n = 18). Median recipient age was 57 years old for group I and 68 years old for group II. Median follow-up was 25 months for group I and 44 for group II. RESULTS: Outcome was evaluated using survival and freedom from graft coronary disease as end points. In group I, 3 of the 4 hearts required revascularization. In group II, 10 of the 18 required revascularization. The majority of the revascularizations were recipient saphenous vein grafts (84.6%) to the donor left anterior descending artery (50%). The 1-month and 2-year actual survivals for group I are 75% and 50% and 87.5% and 81.3 for group II. One patient in group I who was in extremis and 3 in group II died at less than 90 days. Group II early deaths had donor risk factor combinations of coronary artery disease, left ventricular hypertrophy, and long distance. Freedom from new graft coronary artery disease was 100% at 2 years in group I and 87.5% in group II. CONCLUSIONS: Selective use of donor hearts with coronary artery disease is acceptable. Early deaths are related to recipient factors as well as associated donor risk factors. Donor hearts with mild or moderate coronary artery disease and preserved function on echocardiogram can be used but may require revascularization with recipient conduit and/or percutaneous transluminal coronary artery angioplasty. Coronary disease in donor hearts requires grading and does not categorically preclude use, particularly in risk-matched recipients.

Use of assist devices and ECMO to bridge pediatric patients with cardiomyopathy to transplantation.

BACKGROUND: Pulsatile ventricular assist devices (VADs) are used to bridge adults with end-stage heart disease to transplantation. A combination of external implantable pulsatile and continuous-flow external mechanical support now can be used to bridge pediatric patients with end-stage cardiomyopathy to orthotopic heart transplantation (OHT). METHODS: We reviewed consecutive pediatric patients with cardiomyopathy (n = 28) who required mechanical cardiac support from July 1995 to February 2001. All were OHT candidates with severe hemodynamic compromise despite maximal medical support. We excluded from this series patients who had undergone cardiotomy. RESULTS: Nineteen patients received support from external continuous-flow devices, either with extracorporeal membrane oxygenation or with centrifugal VADs, and 9 patients received pulsatile support. Nineteen of 28 (68%) patients were successfully bridged to transplant (17) or weaned (2) from their devices after recovery. Of the patients successfully bridged to transplant or recovery, 89% are alive to date. Univariate analysis revealed that a lower bilirubin concentration after 2 days of support was associated with a favorable outcome (p = 0.006). As expected, the patients with pulsatile VADs had significantly higher rates of extubation and oral feeding. CONCLUSION: Pulsatile and continuous-flow devices can complement each other to significantly extend the lives of a wide range of pediatric patients with severe cardiomyopathies.

Seventeen-year experience with 1,083 heart transplants at a single institution.

BACKGROUND: Heart transplantation is the most accepted treatment for end-stage heart disease. A review of 1,083 consecutive transplants (1984 to 2001) was undertaken. METHODS: Adult recipients were divided into quartiles. The last 540 transplants were combined. Three eras were created from these, 1984 to 1991, 1991 to 1995, and 1995 to 2001, with three age groups: 0 to 18 years, 19 to 61 years, and 62 to 74 years. All patients have at least 1 year of follow-up time. End points were survival, rejection, and graft coronary artery disease. RESULTS: There were 1,012 patients. Donor age, graft ischemic time, and the proportion of elderly recipients and nonstandard donor hearts have increased in the current era. Actuarial 60-month survivals of recipients after 1995 were 80.7% (0 to 18 years); 75.3% (19 to 61 years); and 76.2% (>62 years). The current era children and younger adult groups demonstrated improved results when compared with previous eras (p = 0.003 and p = 0.05). Rejection episodes equal to or greater than ISHLT grade 3A per person per year improved to 0.15 in the current era (p < 0.001). During the three eras, older recipients (>62 years) demonstrated fewer episodes of rejection when compared with other adults (0.13 versus 0.58, p = 0.03). Deaths attributed to graft coronary artery disease decreased from 11% to 5% from era 2 to era 3. Regression analysis revealed a mild effect of donor age on survival and graft coronary artery disease (hazard ratio = 1.02, p = 0.001; hazard ratio = 1.039, p < 0.001, respectively). Recipient predictors of graft coronary artery disease were diagnosis of ischemic cardiomyopathy (hazard ratio = 1.6, p = 0.014) and congenital heart disease (hazard ratio = 3.41, p = 0.02). CONCLUSIONS: Improved survival in the current era may be attributed to better organ preservation, improved immunosuppression and control of infection, and less life-threatening graft coronary artery disease.

Allograft mitral valve replacement.

Allograft valves have been used in cardiac valve replacement for over 40 years. Early failures of allograft mitral valve replacement (AMVR) were attributed to inadequate allograft preservation or unsuccessful implantation techniques. Due to an improved understanding of mitral valve function gained from experience in mitral valve reconstruction, improved imaging techniques for preoperative assessment, and improved methods of allograft preservation, there has been a resurgence of interest in AMVR. The use of bioprosthetic valves in children and young adults is characterized by reduced durability and early valve failure. With the use of mechanical valves, there is a significant long-term risk of morbidity and mortality resulting from thrombosis or hemorrhagic complications from anticoagulation. Additionally, anticoagulation is often difficult to manage in children. The advantages of using allograft mitral valves include the avoidance of anticoagulation and the preservation of the subvalvar apparatus and its role in ventricular function. At our institution, successful early results with AMVR have been obtained in eight children and young adults with previous atrioventricular septal defects, previous placement of mitral valve prostheses, rheumatic valvular disease, and bacterial endocarditis. Our early results and those of others are encouraging for the continued use of AMVR in children and young adults. Long-term follow-up will be necessary to assess the durability and function of these allograft mitral valves. Copyright 1999 by W.B. Saunders Company

Determination of coupled solvent mass in quartz crystal microbalance measurements using deuterated solvents.

A simple method is described for determining of the contribution of hydrodynamically coupled solvent to the adsorbed film mass determined in a quartz crystal microbalance (QCM) when operated in liquid. The method requires no additional apparatus and utilizes the change in QCM resonant frequency response between measurements made in non-deuterated and deuterated solvents. The mass of coupled water in a polymer film has been determined and is found to agree with that determined by XPS analysis of the dried polymer film.

Management of an associated ventricular septal defect at the time of coarctation repair.

BACKGROUND: Management of a ventricular septal defect (VSD) at time of coarctation of the aorta (CoA) repair remains controversial, with recent studies advocating concomitant repair of both defects. We evaluated the surgical management and mortality for patients undergoing CoA repair associated with a VSD. METHODS: We retrospectively reviewed data submitted to the Pediatric Cardiac Care Consortium of patients undergoing repair of CoA from 1982 to 2007. The cohort was divided into three groups: CoA repair plus VSD closure (group 1); CoA repair plus pulmonary artery band (group 2); and CoA repair without repair of VSD (group 3). Variables reviewed included era, age, and weight at repair, and in-hospital mortality. RESULTS: There were 7,860 patients who underwent repair of CoA, of whom 2,022 had an associated VSD (25.7%). Mortality after CoA repair with and without an associated diagnosis of VSD was 8.3% versus 2.1% (p < 0.001). Mean age at repair for group 1 (n = 286) and group 2 (n = 472) was 87.4 days and 21.6 days, respectively (p = 0.004), and median weight was 3.31 kg and 3.30 kg, respectively (p = 0.130). Discharge mortality for group 1 and group 2 was similar, at 8.7% and 9.1%, respectively (p = 0.852). Patients with CoA/VSD who had neither VSD closure nor pulmonary artery banding (group 3) had a hospital mortality of 7.9%. CONCLUSIONS: The association of CoA and VSD is common. A strategy of concomitant VSD closure at CoA repair does not result in worse discharge mortality when compared with pulmonary banding with anticipated staged repair of the VSD. These outcomes support continued evaluation of a one-stage approach.

A paired membrane umbrella double-lumen cannula ensures consistent cavopulmonary assistance in a Fontan sheep model.

OBJECTIVES: The Avalon Elite (Macquet, Rastatt, Germany) double-lumen cannula can provide effective cavopulmonary assistance in a Fontan (total cavopulmonary connection) sheep model, but it requires strict alignment. The objective was to fabricate and test a newly designed paired umbrella double-lumen cannula without alignment requirement. METHODS: The paired membrane umbrellas were designed on the double-lumen cannula to bracket infusion blood flow toward the pulmonary artery. Two umbrellas were attached, one 4 cm above and one 4 cm below the infusion opening. Umbrellas were temporarily wrapped and glued to the double-lumen cannula body to facilitate insertion. A total cavopulmonary connection mock loop was used to test cavopulmonary assistance performance and reliability with double-lumen cannula rotation and displacement. The paired umbrella double-lumen cannula also was tested in a total cavopulmonary connection adult sheep model (n = 6). RESULTS: The bench test showed up to 4.5 L/min pumping flow and approximately 90% pumping flow efficiency at 360° rotation and 8-cm displacement of double-lumen cannula. The total cavopulmonary connection model with compromised hemodynamics was successfully created in all 6 sheep. The cavopulmonary assistance double-lumen cannula with paired umbrellas was smoothly inserted into the superior vena cava and extracardiac conduit in all sheep. At 3.5 to 4.0 L/min pump flow, the systolic arterial blood pressure and central venous pressure returned to normal baseline and remained stable throughout the 90-minute experiment, demonstrating effective cavopulmonary assistance support. Double-lumen cannula rotation and displacement did not affect performance. Autopsy revealed well-opened and positioned paired umbrellas, and double-lumen cannulas were easily removed from the right jugular vein. CONCLUSIONS: Our double-lumen cannula with paired umbrellas is easy to insert and remove. The paired umbrellas eliminated the strict alignment requirement and ensured consistent cavopulmonary assistance performance.

A practical and less invasive total cavopulmonary connection sheep model.

Our goal was to develop a less invasive total cavopulmonary connection (TCPC) sheep model for testing total cavopulmonary assist (CPA) devices. Thirteen sheep underwent a right fourth intercostal lateral thoracotomy. In series I (n = 6), a polytetrafluoroethylene (PTFE) extracardiac conduit (ECC) was connected to inferior vena cava (IVC) and superior vena cava (SVC) by end-to-side anastomosis. The SVC/IVC remained connected to right atrium (RA). A PTFE graft bridged ECC to right pulmonary artery (RPA). Clamps between SVC/IVC anastomoses and RA diverted total venous blood to pulmonary circulation. In series II (n = 7), temporary bypasses between SVC/IVC and RA allowed SVC/IVC to be cut off from RA for better RPA exposure. The ECC-SVC/IVC were end-end anastomosed and ECC-RPA side-side anastomosed for total SVC/IVC to pulmonary artery (PA) conversion. In each series, one sheep died of bleeding. In five sheep in series I and six sheep in series II, the TCPC model was successfully created with significantly increased central venous pressure and significantly decreased PA pressure/arterial blood pressure. Our acute TCPC sheep model has a less traumatic right thoracotomy with no cardiopulmonary bypass and less blood loss with no blood transfusion, facilitating future long-term CPA device evaluation.

Hydrogen-catalyzed, pilot-scale production of small-diameter boron nitride nanotubes and their macroscopic assemblies.

Boron nitride nanotubes (BNNTs) exhibit a range of properties that are as compelling as those of carbon nanotubes (CNTs); however, very low production volumes have prevented the science and technology of BNNTs from evolving at even a fraction of the pace of CNTs. Here we report the high-yield production of small-diameter BNNTs from pure hexagonal boron nitride powder in an induction thermal plasma process. Few-walled, highly crystalline small-diameter BNNTs (∼5 nm) are produced exclusively and at an unprecedentedly high rate approaching 20 g/h, without the need for metal catalysts. An exceptionally high cooling rate (∼10(5) K/s) in the induction plasma provides a strong driving force for the abundant nucleation of small-sized B droplets, which are known as effective precursors for small-diameter BNNTs. It is also found that the addition of hydrogen to the reactant gases is crucial for achieving such high-quality, high-yield growth of BNNTs. In the plasma process, hydrogen inhibits the formation of N2 from N radicals and promotes the creation of B-N-H intermediate species, which provide faster chemical pathways to the re-formation of a h-BN-like phase in comparison to nitridation from N2. We also demonstrate the fabrication of macroscopic BNNT assemblies such as yarns, sheets, buckypapers, and transparent thin films at large scales. These findings represent a seminal milestone toward the exploitation of BNNTs in real-world applications.

Death by late-presenting Bochdalek hernia in infant soon after congenital cardiac repair.

Congenital diaphragmatic hernia (CDH) presenting beyond the neonatal period is commonly perceived to be rare. With reported frequencies of 2.6% to 20% of all CDH, it may be an overlooked cause of mortality. Variable symptomatology makes its diagnosis challenging. We report the sudden death of a 3-month-old patient shortly after hospital discharge following congenital heart surgery. Autopsy findings associated the patient's demise with migrated abdominal contents in the chest through a Bochdalek hernia defect. No indications of CDH existed before hospital discharge. Relevant issues pertaining to congenital heart disease, CDH, and importance of autopsy in this context are discussed.