Device closure of secundum atrial septal defects in infants weighing less than 8 kg

This study aimed to assess the technical aspects of atrial septal defect (ASD) closure using the Amplatzer septal occluder (ASO) and the Gore Helex septal occluder (GHSO) for infants weighing less than 8 kg and to determine the safety, effectiveness, and near-to-intermediate-term outcome of the closure. The Mid-Atlantic Group of Interventional Cardiology Registry of percutaneous, transcatheter ASD closure procedures was reviewed for this analysis. Patients from 10 hospitals in the United States were included. The cohort for this report consisted of 68 patients weighing less than 8 kg (range, 2.3-7.8 kg; mean, 5.5 ± 1.6 kg) and ranging in age from 1 to 24 months (mean, 8.6 ± 4.7 months). The indications for ASD closure were failure to thrive, significant right heart enlargement, shunts otherwise thought to be hemodynamically significant, and poor overall clinical status. Devices were successfully implanted in 66 of the 68 infants (97.1 % procedural success rate). Five minor procedure-related complications occurred. At follow-up assessment, clinical status had improved significantly as measured by improved weight gain and decreased ventilator or oxygen dependence. All residual shunts spontaneously closed during the follow-up period. Six late deaths occurred, none of which were clearly device related. The ASO and GHSO can be safely and effectively implanted for ASD closure in infants weighing less than 8 kg. These procedures usually are successful and seldom complicated, resulting in significant clinical improvement.

Coarctation of the aorta - the current state of surgical and transcatheter therapies

Aortic coarctation represents a distinct anatomic obstruction as blood moves from the ascending to the descending aorta and can present in a range of ages from infancy to adulthood. While it is often an isolated and discrete narrowing, it can also be seen in the more extreme scenario of severe arch hypoplasia as seen in the hypoplastic left heart syndrome or in conjunction with numerous other congenital heart defects. Since the first description of an anatomic surgical repair over sixty years ago, an evolution of both surgical and transcatheter therapies has occurred allowing clinicians to manage and treat this disease with excellent results and low morbidity and mortality. This review focuses on the current state of both transcatheter and surgical therapies, paying special attention to recent data on long-term follow-up of both approaches. Further, current thoughts will be explored about future therapeutic options that attempt to improve upon historical long-term outcomes.

Using imaging to guide patient selection and performance of catheter-based mitral valve repair for mitral regurgitation

Percutaneous transcatheter therapies for mitral regurgitation have found a role for patients at high operative risk with both degenerative and functional pathologies. The MitraClip therapy utilizes a catheter-based system to deliver a clip-type implant to provide apposition between anterior and posterior mitral leaflets. Key to the procedure is using imaging to guide patient selection as well as intra-procedure performance. Careful patient selection remains paramount for success with the MitraClip, with imaging determination of appropriate mitral pathology. Technical success is dependent on skill with echocardiographic imaging, with three-dimensional transesophageal echocardiography particularly valuable.

Percutaneous Mitral Valve Repair in the Initial EVEREST Cohort

Background—

Percutaneous repair of mitral regurgitation (MR) permits examination of the effect of MR reduction without surgery and cardiopulmonary bypass on left ventricular (LV) dimensions and function. The goal of this analysis was to determine the extent of reverse remodeling at 12 months after successful percutaneous reduction of MR with the MitraClip device.

Methods and Results—

Of 64 patients with 3 and 4+ MR who achieved acute procedural success after treatment with the MitraClip device, 49 patients had moderate or less MR at 12-month follow-up. Their baseline and 12-month echocardiograms were compared between the group with and without LV dysfunction. In patients with persistent MR reduction and pre-existing LV dysfunction, there was a reduction in LV wall stress, reduced LV end-diastolic volume, LV end-systolic volume and increase in LV ejection fraction in contrast to those with normal baseline LV function, who showed reduction in LV end-diastolic volume, LV wall stress, no change in LV end-systolic volume, and a fall in LV ejection fraction.

Conclusions—

Patients with pre-existing LV dysfunction demonstrate reverse remodeling and improved LV ejection fraction after percutaneous mitral valve repair.

Clinical Trial Registration—

URL: http://www.clinicaltrials.gov . Unique identifiers: NCT00209339, NCT00209274.

Percutaneous transjugular implantation of MELODY® valve into tricuspid bioprosthesis

We present the technique of transcatheter balloon expandable (MELODY®) valve-in-valve deployment in a frail octogenarian with a failed previous tricuspid bioprosthesis. In patients who are not candidates for conventional surgery, transcatheter approach provides an alternative that warrants careful consideration.

Synthesis of sea urchin-like carbon nanotubes on nano-diamond powder

Carbon nanotubes (CNTs) have unique atomic structure and properties, such as a high aspect ratio and high mechanical, electrical and thermal properties. On the other hand, the agglomeration and entanglement of CNTs restrict their applications. Sea urchin-like multiwalled carbon nanotubes, which have a small aspect ratio, can minimize the problem of dispersion. The high hardness, thermal conductivity and chemical inertness of the nano-diamond powder make it suitable for a wide range of applications in the mechanical and electronic fields. CNTs were synthesized on nano-diamond powder by thermal CVD to fabricate a filler with suitable mechanical properties and chemical stability. This paper reports the growth of CNTs with a sea urchin-like structure on the surface of the nano-diamond powder. Nano-diamond powders were dispersed in an attritional milling system using zirconia beads in ethanol. After the milling process, 3-aminopropyltrimethoxysilane (APS) was added as a linker. Silanization was performed between the nano-diamond particles and the metal catalyst. Iron chloride was used as a catalyst for the fabrication of the CNTs. After drying, catalyst-attached nano-diamond powders could be achieved. The growth of the carbon nanotubes was carried out by CVD. The CNT morphology was examined by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The mean diameter and length of the CNTs were 201 nm and 3.25 microm, respectively.

Contemporary outcomes for surgical mitral valve repair: a benchmark for evaluating emerging mitral valve technology

OBJECTIVE

The emergence of transcatheter approaches to mitral valve (MV) repair has focused attention on outcomes after surgical MV repair. Results from the EVEREST II trial demonstrated worse short-term major adverse event (MAE) rates for surgical repair. This study analyzes contemporary outcomes of surgical MV repair to establish a benchmark for future therapeutic comparisons.

METHODS

From 2003 to 2008, 903 isolated MV repair operations were performed at 13 different statewide cardiac centers. Patients were excluded if they had prior valve operations or mitral stenosis similar to EVEREST II. MAE rate was defined using similar criteria to EVEREST II, including postoperative atrial fibrillation and transfusion of 2 units of blood or more. Univariate analyses and multivariate regression models were applied to identify independent predictors of MAEs after surgical MV repair.

RESULTS

Mean patient age was 57.0 ± 13.2 years, and the majority of patients were men (59.0%, 533/903). The prevalence of preoperative risk factors was as follows: stroke 3.9% (35/903), immunosuppression 2.4% (22/903), heart failure 32.1% (290/903), renal failure 3.5% (32/903), and previous coronary artery bypass grafting 3.4% (31/903). Mean ejection fraction was 55.6 ± 11.3%. MAE rate was 29.0% (262/903), including atrial fibrillation 17.6% (159/903), renal failure 1.3% (12/903), stroke 0.9% (8/903), and operative mortality 1.1% (10/903). Multivariate correlates of MAE included the following: advanced age, prior stroke, immunosuppression, and operation time. Importantly, gender, previous coronary bypass grafting, renal failure, and ejection fraction were not independent predictors of MAE.

CONCLUSIONS

In the current era, patients undergoing surgical MV repair have low mortality. MAE rate was largely due to postoperative atrial fibrillation. These results may help to stratify which patients may be best served with newer technologies.

Efficacy and safety of ventricular tachycardia ablation with mechanical circulatory support compared with substrate-based ablation techniques

AIMS

Catheter ablation of ventricular tachycardia (VT) can be limited by haemodynamic instability. In these cases, substrate-based ablation is typically performed. An alternative is to perform activation and entrainment mapping during VT supported by a percutaneous left ventricular assist device (pVAD). We sought to compare the complication and success rates of pVAD-assisted VT ablation with scar-based techniques.

METHODS AND RESULTS

Thirteen consecutive patients with haemodynamically unstable VT underwent pVAD-assisted ablation (pVAD group) and were retrospectively compared with 18-matched patients undergoing a substrate-based VT ablation (non-pVAD group). There was no significant difference in age or ejection fraction between the groups although pVAD patients tended to have more shocks in the preceding months. Procedure times were longer for the pVAD group. The number of monomorphic VTs induced was greater in the pVAD group (3.2 vs. 1.6, P= 0.04); however, after ablation, there was no difference in inducibility between the pVAD and non-pVAD group (10 of 13 vs. 12 of 18; 77 vs. 67%, P = 0.69). There was no difference in acute complications including stroke or death. At 9 ± 3 months, 1-year freedom from implantable cardioverter-defibrillator (ICD) shocks/therapies for sustained VT were similar (P= 0.96). In multivariable analysis, the absence of atrial fibrillation (hazard ratio=0.15, P= 0.04) was associated with a lower incidence of ICD shocks.

CONCLUSIONS

In high-risk patients, pVAD-assisted VT ablation guided by activation and entrainment mapping is a feasible alternative to substrate mapping and allows outcomes comparable to substrate mapping.

Nano-tribological properties of topographically undulated nanocrystalline diamond patterns

Surface roughness-controlled nanocrystalline diamond film was fabricated as an undulated line and space pattern on a silicon oxide surface. To simulate a MEMS (Micro-/Electro-Mechanical System) and NEMS (Nano-/Electro-Mechanical System) patterned surface, 800 nm and 1 microm wide lines with a 200 nm wide space pattern were prepared on the substrate using E-beam lithography and an ESAND (Electrostatic Self-assembly of NanoDiamond) seeding layer lift-off process. Through this process, an undulated pattern of a nanocrystalline CVD diamond successfully formed by a conventional micro crystalline diamond growth system. The roughness of the deposited surface was controlled by regulating the size of the seeding nanodiamond particles. Crushing of the nanodiamond aggregates and dispersion of the nanodiamond solution was performed in an attrition milling system. An AFM (Atomic Force Microscopy) probe was used for the wear test and surface profiling of nanocrystalline diamond coatings. 2-D friction coefficient mapping by LFM (Lateral Force Microscopy) scanning showed a low friction coefficient (< 0.1) on the line-patterned diamond surface, and a higher friction coefficient (< 0.3) on a narrow area adjacent to the undulated pattern edges. With prolonged LFM scanning, the high coefficient of friction was reduced to less than 0.1. The bonding status of the nanocrystalline diamond was analyzed with Raman spectroscopy.

Assessment of pulmonary hypertension in the pediatric catheterization laboratory: current insights from the Magic registry

OBJECTIVES

To assess protocols, demographics, and hemodynamics in pediatric patients undergoing catheterization for pulmonary hypertension (PH).

BACKGROUND

Pediatric specific data is limited on PH.

METHODS

Review of the Mid-Atlantic Group of Interventional Cardiology (MAGIC) collaboration PH registry dataset.

RESULTS

Between November 2003 and October 2008, seven institutions submitted data from 177 initial catheterizations in pediatric patients with suspected PH. Pulmonary arterial hypertension associated with congenital heart disease (APAH-CHD) (n = 61, 34%) was more common than idiopathic PAH (IPAH) (n = 36, 20%). IPAH patients were older with higher mean pulmonary arterial pressures (mPAP) (P < 0.01). Oxygen lowered mPAP in patients with IPAH (P < 0.01) and associated PAH not related to congenital heart disease (APAH-non CHD) (P < 0.01). A synergistic effect was seen with inhaled nitric oxide (iNO) (P < 0.01). Overall 9/30 (29%) patients with IPAH and 8/48 (16%) patients with APAH-non CHD were reactive to vasodilator testing. Oxygen lowered pulmonary vascular resistance index (PVRI) in patients with APAH-CHD (P < 0.01). There was no additive effect with iNO but a subset of patients required iNO to lower PVRI below 5 WU·m(2). General anesthesia (GA) lowered systemic arterial pressure (P < 0.01) with no difference between GA and procedural sedation on mPAP or PVRI. Adverse events were rare (n = 7) with no procedural deaths.

CONCLUSIONS

Pediatric patients with PH demonstrate a higher incidence of APAH-CHD and neonatal specific disorders compared to adults. Pediatric PH patients may demonstrate baseline mPAP < 40 mm Hg but > 50% systemic illustrating the difficulty in applying adult criteria to children with PH. Catheterization in children with PH is relatively safe.

Constraining carbon sources and growth rates of freshwater microbialites in Pavilion Lake using (14)C analysis

This study determined the natural abundance isotopic compositions ((13)C, (14)C) of the primary carbon pools and microbial communities associated with modern freshwater microbialites located in Pavilion Lake, British Columbia, Canada. The Delta(14)C of dissolved inorganic carbon (DIC) was constant throughout the water column and consistent with a primarily atmospheric source. Observed depletions in DIC (14)C values compared with atmospheric CO(2) indicated effects due either to DIC residence time and/or inputs of (14)C-depleted groundwater. Mass balance comparisons of local and regional groundwater indicate that groundwater DIC could contribute a maximum of 9-13% of the DIC. (14)C analysis of microbial phospholipid fatty acids from microbialite communities had Delta(14)C values comparable with lake water DIC, demonstrating that lake water DIC was their primary carbon source. Microbialite carbonate was also primarily derived from DIC. However, some depletion in microbialite carbonate (14)C relative to lake water DIC occurred, due either to residence time or mixing with a (14)C-depleted carbon source. A detrital branch covered with microbialite growth was used to estimate a microbialite growth rate of 0.05 mm year(-1) for the past 1000 years, faster than previous estimates for this system. These results demonstrate that the microbialites are actively growing and that the primary carbon source for both microbial communities and recent carbonate is DIC originating from the atmosphere. While these data cannot conclusively differentiate between abiotic and biotic formation mechanisms, the evidence for minor inputs of groundwater-derived DIC is consistent with the previously hypothesized biological origin of the Pavilion Lake microbialites.

Effect of reinforcement particle size on the tribological properties of nano-diamond filled polytetrafluoroethylene based coating

The tribological properties of PTFE composite coatings reinforced by nano-diamonds were investigated. Mechanical particle size reduction and dispersion of nano-diamond aggregates were performed by milling with ceramic beads in an organic solvent. Particle size was controlled by the milling time. Pastes comprising a PTFE solution mixed with nano-diamond having various sizes were coated on the aluminum substrate. Ball-on-plate type wear test was performed to investigate the friction and wear behavior. The results indicated that the addition of nano-diamonds effectively improved tribological performance of the PTFE coating. The reduction in nano-diamond sizes were not always improved the wear resistance of PTFE coating. This unexpected behavior was explained by observation on the worn surfaces and wear debris.

Ultra thin CVD diamond film deposition by electrostatic self-assembly seeding process with nano-diamond particles

Ultra thin and smooth nano crystalline diamond films were fabricated with electrostatic self-assembly seeding of explosively synthesized nano-diamond particles. Hard aggregates of nano-diamond particles were crushed by high revolution attrition milling at 1000 RPM to regulate the particle size. Through this process, cationic nano-diamond particles were coated with anionic PSS (poly sodium 4-styrene sulfonate) electrolytes. Anionic Si(100) substrate was coated with cationic PDDA (poly diallyldimethyl ammonium chloride) solution. Si(100)/PDDA/PSS/ND (nano-diamond) layer-by-layer structure was formed as a seeding layer by the simple dipping and rinsing of positively charged substrate into anionic PSS/nano-diamond solution. Throughout the seeding process, neither mechanical damage nor chemical attack was observed on the substrate. Every stage of this preparation was carried out at room temperature and pressure. The effect of attrition milling was determined by changing the milling time from 1 hr to 5 hrs. Through the attritional milling and monolayer formation of the nano-diamond, nucleation density was increased up to 3 x 10(11)/cm2. Typical hot filament chemical vapor deposition system was used to coat the diamond film on the ESA (electrostatic self-assembly) seeded Si(100) substrate. Although typical diamond deposition conditions (90 torr/1% CH4 in H2/800 degrees C) were maintained, ultra thin (< 100 nm) and continuous nano crystalline diamond films were deposited. Regardless of metallic or ceramic substrate, ESND (ESA Seeding of nano-diamond) process is applicable if the substrate has any charge. This simple nano technology based process ensures high thickness uniformity of diamond coating without visible edge effect.

Left ventricular assist via percutaneous transhepatic transseptal cannulation in swine

OBJECTIVE

To report the in vivo testing of transhepatic, transseptal cannula insertion to support the left ventricle.

BACKGROUND

Percutaneous cannulation for circulatory assist poses particular challenges in pediatrics. We utilized a strategy using a transhepatic, transseptal venous cannula inserted into the left atrium, a centrifugal pump, and arterial cannula.

METHODS

Yorkshire swine of 5-20 kg (n = 6) were anesthetized for the procedure. After hepatic venous angiography, percutaneous puncture of the hepatic vein was performed, followed by transseptal puncture with echocardiographic guidance. A 10-14 Fr 26-cm venous inflow cannula was placed in the left atrium via hepatic approach. The femoral artery was cannulated with a 6-10 Fr femoral cannula, and the circuit completed with the TandemHeart centrifugal pump.

RESULTS

Implantation of the system utilizing the transhepatic approach was successful in all experiments. The pump delivered flows ranging from 0.8 to 1.4 L/min, which corresponded to 40-86% of the baseline systemic outputs. Decannulation and occlusion of the hepatic tract was successful utilizing transcatheter vascular occlusion plugs.

CONCLUSION

The transhepatic, transseptal insertion of the inflow cannula, coupled with the TandemHeart centrifugal pump and femoral arterial cannulation allows percutaneous circulatory support in 5- to 20-kg models.

Sero-epidemiology of hepatitis A virus infection among healthcare workers in Korean hospitals

Hepatitis A virus (HAV) has been increasingly reported in Korea as has an outbreak in Korean healthcare workers (HCWs). This 2008 study evaluated the sero-epidemiology of HAV infections among 3696 HCWs in four Korean hospitals. HCWs were tested for immunoglobulin G anti-HAV antibodies using commercially available kits. Data including demographic characteristics, occupation, workplace and serological status for other hepatitis viruses were collected. Statistical analyses were conducted to identify variables related to HAV seropositivity. Among the 3696 participants, 2742 (74%) were women and the majority (96%) were aged 20-39 years (median: 28; range: 19-68). Eighteen percent were physicians, 46% nurses, 10% nurses' aides, 11% paramedical technicians and 15% administrative staff. Seropositivity for HAV significantly increased with age (P<0.001): 1.8% for < or =24 years, 14.7% for 25-29 years, 41.8% for 30-34 years, 75.5% for 35-39 years, and 93.7% for > or =40 years. Among those aged 20-39 years, age-specific HAV seroprevalence was significantly lower in physicians than in the other occupational groups (P<0.001). In Korea, mass vaccination to HCWs aged < or =29 years or screening for seropositivity and vaccinating non-immune subjects aged 30-39 years should be considered, especially in physicians.

B-type natriuretic peptide concentrations to guide treatment of patent ductus arteriosus

OBJECTIVE

To determine whether b-type natriuretic peptide (BNP) concentrations can guide treatment of patent ductus arteriosus (PDA) to reduce the number of indomethacin doses without increasing morbidity.

DESIGN

Prospective, randomised, controlled trial.

SETTING

Single-centre referral neonatal intensive care unit.

PATIENTS

Infants with echocardiographic diagnosis of PDA. Infants with congenital heart disease or renal insufficiency were excluded.

INTERVENTIONS

BNP measurement and echocardiography were performed in all subjects before and after indomethacin treatment. The investigational group had BNP concentrations measured 12 and 24 h after the first dose (before the 2nd and 3rd doses of indomethacin). Indomethacin dosing was withheld in the BNP-guided group if the 12 or 24 h BNP concentrations were found to be <100 pg/ml.

MAIN OUTCOME MEASURES

Number of doses of indomethacin given during the primary course of treatment (three doses every 12 h).

RESULTS

Sixty patients were randomly assigned to control (n = 30) and BNP-guided (n = 30) treatment groups. There was no difference between the groups with respect to gestational age (26(+3) vs 25(+5) weeks, respectively), Apgar scores, delivery method, gender or indomethacin prophylaxis. Median baseline and 48 h BNP concentrations did not differ between the groups (0 h: 500 vs 542 pg/ml; 48 h: 85 vs 126 pg/ml; control and BNP-guided groups, respectively). During primary indomethacin treatment, the BNP-guided group received fewer doses of indomethacin than controls (70 vs 88 doses, p<0.05). The rate of PDA ligation, intestinal perforation and chronic lung disease did not differ between groups.

CONCLUSIONS

BNP-guided treatment reduced the number of primary indomethacin doses. There was no increase in PDA persistence or associated morbidity.

Community use of the amplatzer atrial septal defect occluder: results of the multicenter MAGIC atrial septal defect study

The objective of this study was to determine the initial safety and results of unrestricted multi-institution routine community use of the Amplatzer Septal Occluder (ASO) for atrial septal defect (ASD) closure. A multicenter, nonrandomized prospective study was performed in 13 pediatric cardiology centers from November 2004 to September 2007. Data were collected at the time of cardiac catheterization and 1 day postimplant. Four hundred seventy-eight patients underwent cardiac catheterization for ASO device closure of an ASD. The median age was 6 years (range, <1-83 years), and the mean weight was 37.2 kg (range, 2.6-148 kg). Procedural success was 96% (458/478 patients), with deficient rims being the major single reason for failed implantation (9/20). Major and minor complication rates were 1.1% and 4.8%, respectively, and were not different between simple and complex ASD groups. Success at 24 h was 99.4% (333/335) in the simple ASD group and 100% (120/120) in the complex ASD group. The presence of large defects, the presence of multiple defects, the use of multiple devices, and a weight <8 kg were significantly associated with a residual shunt (small to moderate) at 24 h. In conclusion, the ASO device in routine clinical practice for simple and complex ASD closure has an immediate safety and effectiveness profile equal to that reported in the initial pivotal FDA trial for simple ASDs. Based on the evolution in care posed by the ASO and the lack of consensus on patient selection in complex ASDs, this study points out the need to redefine the optimal patient and possibly broaden the indications for device closure of ASDs.

Percutaneous ventricular assist device to rescue a patient with profound shock from a thrombosed prosthetic mitral valve

The TandemHeart is a percutaneous ventricular assist device that has been approved to provide hemodynamic support in high-risk patients undergoing cardiac procedures, including percutaneous coronary interventions and aortic balloon valvuloplasty. Limited data exists for its role in stabilizing cardiogenic shock secondary to prosthetic valve dysfunction. In conclusion, we report the first case, to our knowledge, of profound cardiogenic shock secondary to an acutely thrombosed mechanical mitral valve in which the use of the TandemHeart was instrumental in rescuing a critically ill young female who made a full recovery.

Cardiovascular magnetic resonance of pulmonary artery growth and ventricular function after Norwood procedure with Sano modification

For hypoplastic left heart syndrome (HLHS), there have been concerns regarding pulmonary artery growth and ventricular dysfunction after first stage surgery consisting of the Norwood procedure modified with a right ventricle-to-pulmonary artery conduit. We report our experience using cardiovascular magnetic resonance (CMR) to determine and follow pulmonary arterial growth and ventricular function in this cohort. Following first stage palliation, serial CMR was performed at 1 and 10 weeks post-operatively, followed by cardiac catheterization at 4-6 months. Thirty-four of 47 consecutive patients with HLHS (or its variations) underwent first stage palliation. Serial CMR was performed in 20 patients. Between studies, ejection fraction decreased (58 +/- 9% vs. 50 +/- 5%, p < 0.05). Pulmonary artery growth occurred on the left (6 +/- 1 mm vs. 4 +/- 1 mm at baseline, p < 0.05) but not significantly in the right. This trend continued to cardiac catheterization 4-6 months post surgery, with the left pulmonary artery of greater size than the right (8.8 +/- 2.2 mm vs. 6.7 +/- 1.9 mm, p < 0.05). By CMR, 5 had pulmonary artery stenoses initially, and at 2 months, 9 had stenoses. Three of the 9 underwent percutaneous intervention prior to the second stage procedure. In this cohort, reasonable growth of pulmonary arteries occurred following first stage palliation with this modification, although that growth was preferential to the left. Serial studies demonstrate worsening of ventricular function for the cohort. CMR was instrumental for detecting pulmonary artery stenosis and right ventricular dysfunction.

Transesophageal Echocardiographic Guidance for Surgical Repair of Aortic Insufficiency in Congenital Heart Disease

A total of 14 patients with congenital heart disease underwent aortic valve repair, with transesophageal echocardiograms performed to determine severity, mechanism, and direction of aortic insufficiency (AI) jet to tailor the surgical approach. Patient age was 13 +/- 10 years, and accompanying diagnoses were: truncus arteriosus, subaortic stenosis, ventricular septal defect, and tetralogy of Fallot. Repeat transesophageal echocardiography was performed after each cardiopulmonary bypass run to determine residual AI and mechanism. Aortic valve leaflet number ranged from 2 to 4. AI was graded 2 to 4+, and postoperatively 0 to 2+. Primary mechanisms were: cusp prolapse (7), leaflet holes (4), restricted leaflet motion (2), and annular dilation (3). Patients required 1 to 3 cardiopulmonary bypass runs until primary AI mechanism was abolished. In all, 12 of 14 patients were free from death or repeated surgery at 2 years. Surgical repair of congenital AI may be aided by transesophageal echocardiographic guidance, with repeat short cardiopulmonary bypass as needed. Long-term studies are needed to determine durability of repair.

Fluid force predictions and experimental measurements for a magnetically levitated pediatric ventricular assist device

The latest generation of artificial blood pumps incorporates the use of magnetic bearings to levitate the rotating component of the pump, the impeller. A magnetic suspension prevents the rotating impeller from contacting the internal surfaces of the pump and reduces regions of stagnant and high shear flow that surround fluid or mechanical bearings. Applying this third-generation technology, the Virginia Artificial Heart Institute has developed a ventricular assist device (VAD) to support infants and children. In consideration of the suspension design, the axial and radial fluid forces exerted on the rotor of the pediatric VAD were estimated using computational fluid dynamics (CFD) such that fluid perturbations would be counterbalanced. In addition, a prototype was built for experimental measurements of the axial fluid forces and estimations of the radial fluid forces during operation using a blood analog mixture. The axial fluid forces for a centered impeller position were found to range from 0.5 +/- 0.01 to 1 +/- 0.02 N in magnitude for 0.5 +/- 0.095 to 3.5 +/- 0.164 Lpm over rotational speeds of 6110 +/- 0.39 to 8030 +/- 0.57% rpm. The CFD predictions for the axial forces deviated from the experimental data by approximately 8.5% with a maximum difference of 18% at higher flow rates. Similarly for the off-centered impeller conditions, the maximum radial fluid force along the y-axis was found to be -0.57 +/- 0.17 N. The maximum cross-coupling force in the x direction was found to be larger with a maximum value of 0.74 +/- 0.22 N. This resulted in a 25-35% overestimate of the radial fluid force as compared to the CFD predictions; this overestimation will lead to a far more robust magnetic suspension design. The axial and radial forces estimated from the computational results are well within a range over which a compact magnetic suspension can compensate for flow perturbations. This study also serves as an effective and novel design methodology for blood pump developers employing magnetic suspensions. Following a final design evaluation, a magnetically suspended pediatric VAD will be constructed for extensive hydraulic and animal testing as well as additional validation of this design methodology.

Traumatic ascending aortopulmonary window following pulmonary artery stent dilatation: therapy with aortic endovascular stent graft

Endovascular stent grafts have become an established therapy in adults for descending thoracic aortic disease. We report a case of a 13-year-old boy with a hemodynamically significant traumatic aortopulmonary window following angioplasty of pulmonary artery stent. Endovascular stent graft implantation into the ascending aorta was performed to seal off the communication, with dramatic hemodynamic improvement.

Hybrid palliation in hypoplastic left heart syndrome

PURPOSE OF REVIEW

Despite progressive improvement in surgical results, hypoplastic left heart syndrome remains one of the congenital heart abnormalities with the greatest morbidity and mortality. Hybrid approaches to management, combining surgical and interventional catheterization procedures, have been introduced to minimize exposure to cardiopulmonary bypass, and improve outcomes for these high-risk infants.

RECENT FINDINGS

First-stage palliation of hypoplastic left heart syndrome has been performed as a hybrid procedure combining surgical pulmonary artery banding with catheterization stenting of the ductus arteriosus and balloon atrial septostomy, especially in high-risk patients. Additionally, several centers have performed second-stage palliation - bidirectional Glenn or hemi-Fontan procedures - in a manner that allows the subsequent 'Fontan' procedure to be completed in the catheterization laboratory with a covered stent.

SUMMARY

These innovative procedures offer the potential of an alternative management strategy for hypoplastic left heart syndrome. They have been applied to a very limited number of patients and long-term results are not available. Their role in management of hypoplastic left heart syndrome remains to be defined, especially as results of conventional surgical management continue to improve.

Percutaneous device closure of atrial septal defect in a premature infant with rapid improvement in pulmonary status

Atrial septal defects are a common congenital heart defect and may complicate the course of a premature infant by imposing volume overload to the lungs. Surgical closure requires cardiopulmonary bypass and, frequently, a midline sternotomy. Recently, percutaneous transcatheter devices were approved for atrial septal defect closure but have been limited to use in larger children. Here we present the first known report of a transcatheter device closure of an atrial septal defect in a premature infant, which resulted in rapid improvement of the patient's respiratory status.

Transcatheter closure of high-risk muscular ventricular septal defects with the CardioSEAL occluder: Initial report from the CardioSEAL VSD Registry

OBJECTIVES

The CardioSEAL VSD registry was created to track safety of the device to close high-risk Ventricular Septal Defect (VSD).

BACKGROUND

This is the first report from the multi-centered CardioSEAL VSD registry reviewing demographics and initial results.

METHODS

Centers recruited patients with VSD who were high-risk for surgery due to medical condition or anatomic features.

RESULTS

18 centers contributed data on 55 high-risk patients who had 61 VSD-occlusion procedures, with age of range of 5 days to 65 years and using one to six devices. Implantation approach was transvenous in 48, perventricular in five, and by combined approach in two patients. Ninety-two percent of intended VSD device implants were judged successful. Twenty-two patients had single VSD closed by single device in 18 and by two devices in four patients. All patients <8 kg underwent perventricular device implantation. Thirty-three patients had multiple VSDs which were closed by a single device in 23, and multiple devices in 10. At discharge echocardiography showed total residual flow through all VSDs in which devices were used was classified as "Small" or less in 74%, "More than small" in 11%, and "Uncertain" in 15%. Eight major adverse events occurred in 5/61 cases (8% event rate), with 3/81 devices embolized (4% embolization rate), 5/81 devices surgically explanted (6% explant rate), and no deaths judged to be procedure-related.

CONCLUSION

This initial report from the multi-centered CardioSEAL VSD registry demonstrates the safety of the device to close high-risk VSDs.

Endothelial dysfunction and circadian blood pressure rhythmicity in young heart transplant recipients

Blood pressure variability correlates with circadian rhythmicity in endothelium-derived nitric oxide (NO) production in adults. Young, hypertensive orthotopic heart transplant (OHT) patients have functional abnormalities in NO-dependent signaling pathways that lead to reduced NO bioavailability and endothelial dysfunction. Following acute intravenous infusion of L: -arginine, the amino acid substrate for NO, OHT patients normalize blood pressure (BP) and endothelial function. However, the effects of chronic L: -arginine infusion on circadian BP rhythmicity and endothelial function in OHT patients have not been described. Six OHT patients (9-29 years old), and seven healthy control subjects (19-28 years old) were admitted for 48 hours. Systolic, diastolic, and mean blood pressures (MBP) were recorded hourly. Urine samples were obtained to measure nitrates/nitrites (NO(X)). Brachial artery flow-mediated vasodilatation (FMD; an index of endothelial function) and left ventricular ejection fraction (LVEF) were measured 0, 23, and 48 hours after admission. Intravenous L: -arginine HC1 was infused continuously beginning 24 hours after admission in all subjects. The incidence (50%) and degree (12.0 +/- 9.2%) of nocturnal MBP dipping was significantly less in OHT patients than control subjects. Furthermore, FMD was significantly reduced in OHT patients compared to controls (3.2 +/- 1.1 vs 7.2 +/- 3.1%, p = 0.01). L: -Arginine infusion had no significant effect on 24-hour MBP, LVEF, or nocturnal dipping status in any subject; however, L: -arginine normalized FMD in OHT patients (7.4 +/- 1.8%). Circadian BP variability and endothelial function are impaired in young cardiac transplant patients with medically controlled hypertension, and L: -arginine administration reverses endothelial dysfunction.

Development of the MAGIC Congenital Heart Disease Catheterization Database for Interventional Outcome Studies

As the field of catheter-based therapies for congenital heart disease continues to expand, we lack the evidence-based data to make appropriate therapeutic decisions in the catheterization laboratory. A stumbling block to the determination of evidence-based therapies is our inability to simply and reliably share outcome data across multiple centers. We investigated whether a commonly used congenital heart disease catheterization database program (PedCath) could be used as an automatic catheterization data submission tool to a central database for outcome analysis. To test the feasibility of such a tool for collaborative outcomes research we formed a national group of seven congenital heart disease centers, the Mid-Atlantic Group of Interventional Cardiology, to warehouse and analyze catheterization data. We successfully modified PedCath to transfer the results of catheter-based therapies on 256 therapeutic procedures for atrial septal defect (ASD) closure, coarctation of the aorta angioplasty and stenting, and pulmonary and aortic balloon valvuloplasties over a 13-month pilot period. Short-term follow-up within the 13-month period was received on 31 patients. This study demonstrated the successful development of a simple process, requiring minimal data entry for investigators from around the world to share cardiac catheterization data for long-term outcome determination of catheter-based therapies for congenital heart disease.

Risk-stratified approach to hybrid transcatheter-surgical palliation of hypoplastic left heart syndrome

We prospectively employed a risk-stratified approach to first-stage palliation of hypoplastic left heart syndrome. High-risk features included severe tricuspid insufficiency, severe right ventricular dysfunction, a severely restrictive or intact atrial septum, an ascending aortic diameter < or = 2 mm, late presentation, weight < 2 kg, or significant extracardiac issues, Infants without high-risk features underwent a Norwood procedure (with Sano modification), whereas infants with high-risk features underwent a hybrid procedure consisting of bilateral pulmonary artery banding, ductal stenting, and atrial septostomy or a Norwood/Sano. Operative survival for 10 infants without high-risk features undergoing a Norwood/Sano procedure was 90%. Operative survival for 5 infants with high-risk features undergoing hybrid palliation was 100%, compared to 29% in 7 infants with high-risk features undergoing the Norwood/Sano procedure. Although only short-term data are available, this hybrid palliative procedure may have a role for infants with hypoplastic left heart syndrome and high-risk features.

Computational Design and Experimental Performance Testing of an Axial-Flow Pediatric Ventricular Assist Device

The Virginia Artificial Heart Institute continues to design and develop an axial-flow pediatric ventricular assist device (PVAD) for infants and children in the United States. Our research team has created a database to track potential PVAD candidates at the University of Virginia Children's Hospital. The findings of this database aided with need assessment and design optimization of the PVAD. A numerical analysis of the optimized PVAD1 design (PVAD2 model) was also completed using computational fluid dynamics (CFD) to predict pressure-flow performance, fluid force estimations, and blood damage levels in the flow domain. Based on the PVAD2 model and after alterations to accommodate manufacturing, a plastic prototype for experimental flow testing was constructed via rapid prototyping techniques or stereolithography. CFD predictions demonstrated a pressure rise range of 36-118 mm Hg and axial fluid forces of 0.8-1.7 N for flows of 0.5-3 l/min over 7000-9000 rpm. Blood damage indices per CFD ranged from 0.24% to 0.35% for 200 massless and inert particles analyzed. Approximately 187 (93.5%) of the particles took less than 0.14 seconds to travel completely through the PVAD. The mean residence time was 0.105 seconds with a maximum time of 0.224 seconds. Additionally, in a water/glycerin blood analog solution, the plastic prototype produced pressure rises of 20-160 mm Hg for rotational speeds of 5960 +/- 18 rpm to 9975 +/- 31 rpm over flows from 0.5 to 4.5 l/min. The numerical results for the PVAD2 and the prototype hydraulic testing indicate an acceptable design for the pump, represent a significant step in the development phase of this device, and encourage manufacturing of a magnetically levitated prototype for animal experiments.

Transcatheter occlusion of aortopulmonary shunts during single-ventricle surgical palliation

Development of aortopulmonary collaterals during the course of surgical palliation for single-ventricular anatomy has been linked to adverse outcomes following Fontan palliation. We investigated the hemodynamic significance of aortopulmonary collaterals during presurgical cardiac catheterization of patients with single-ventricle surgically palliated anatomy. Thermal indicator dilution studies were performed to determine degree of shunt. A total of 52 patients were studied and the data were analyzed. Measurements by thermal indicator dilution correlated significantly with qualitative angiographic grading of aortopulmonary collaterals. However, the hemodynamic significance of these aortopulmonary collaterals, as measured by thermal indicator dilution, did not correlate with postoperative outcome variables. This study demonstrated that thermal indicator dilution measurement holds promise for hemodynamically quantifying the significance of aortopulmonary shunts in surgically palliated single-ventricular patients. However, the degree of recirculation from aortopulmonary collaterals does not correlate with outcome after Fontan surgery in this patient cohort.

Effect of oral L-arginine on oxidant stress, endothelial dysfunction, and systemic arterial pressure in young cardiac transplant recipients

Oral L-arginine therapy reverses endothelial dysfunction and attenuates high blood pressure in hypertensive cardiac transplant recipients. L-arginine corrects derangements in the vascular endothelial nitric oxide (NO)-dependent signaling pathway. Our data support the concept that cardiac transplant recipients use excess endogenous NO from L-arginine supplementation to buffer increased vascular oxidant stress.

Aminophylline for the prevention of apnea during prostaglandin E1 infusion

BACKGROUND

Apnea is associated with prostaglandin E1 infusion (PGE1) used in the palliation of ductal-dependent congenital heart lesions.

HYPOTHESIS

Aminophylline is a central respiratory stimulant and will decrease the incidence of PGE1-associated apnea and the need for intubation for apnea in infants with ductal-dependent congenital heart disease.

METHODS

Informed consent was obtained for all patients. In a prospective, double-blinded, placebo-controlled study, newborn infants with ductal-dependent congenital heart disease were randomized to receive either aminophylline or placebo during initiation and maintenance of PGE1, which was started at 0.01 microg/kg/min and increased to 0.03 microg/kg/min. Aminophylline was given as a bolus dose of 6 mg/kg before or during initiation of PGE1, and continued at 2 mg/kg dose every 8 hours for 72 hours. Serum aminophylline levels were checked at 18 and 36 hours. The primary study endpoint was intubation for apnea, with a secondary endpoint of apnea, as defined as acute cessation of breathing with associated hypoxia and bradycardia.

RESULTS

The study evaluated 42 infants. The 2 groups were similar for gestational age, weight, hematocrit, and use of sedation. In the aminophylline group, serum levels were 7.6 +/- 1.2 microg/mL. No significant side effects of aminophylline were seen. Infants receiving aminophylline (n = 21) were less likely to have apnea (2 vs 11) or be intubated for apnea (0 vs 6). Length of postoperative stay and survival to discharge were similar between the 2 groups.

CONCLUSIONS

Aminophylline was effective for the prevention of apnea and intubation for apnea associated with PGE1 in infants with ductal-dependent congenital heart disease.