Temperature resistant fast InxGa1-xAs / GaAs quantum dot saturable absorber for the epitaxial integration into semiconductor surface emitting lasers.

Quantum-dot-based semiconductor saturable absorber mirrors (SESAMs) with fast response times were developed by molecular beam epitaxy (MBE). Using quantum dots (QDs) in the absorber region of the SESAMs instead of quantum wells, enables additional degrees of freedom in the design, the control of saturation parameters and the recovery dynamics. However, if one wants to integrate such a SESAM element into semiconductor surface emitting lasers such as a mode-locked integrated external-cavity surface-emitting laser (MIXSEL), the saturable absorber layers have to withstand a longer high-temperature growth procedure for the epitaxial formation of distributed Bragg reflectors (DBR). Typically defect related SESAMs will be annealed at those growth temperatures and lose their high-speed performance. Here we present a systematic study on the growth parameters and post-growth annealing of SESAMs based on high-quality InxGa1-xAs/GaAs quantum dots (QDs) grown by MBE at growth temperatures of 450 °C or higher. The good quality enables the QDs to survive the long DBR overgrowth at 600 °C with only minimal shifts in the designed operation wavelength of 1030 nm required for growth of MIXSEL devices. The introduction of recombination centers with p-type modulation doping and additional post-growth annealing improves the absorption of the high-quality QDs. Hence, low saturation fluences < 10 µJ/cm2 and a reduction of the τ1/e recovery time to values < 2 ps can be achieved.

Tightly locked optical frequency comb from a semiconductor disk laser.

Ultrafast semiconductor disk lasers (SDLs) passively modelocked using semiconductor saturable absorbers mirrors (SESAMs) generate optical frequency combs (OFCs) with gigahertz line spacings - a regime where solid-state and fiber lasers struggle with geometrical and Q-switching limitations. We stabilized both the frequency comb spacing and the offset without any additional external optical amplification or pulse compression. The overall noise performance is competitive with other gigahertz OFCs. A SESAM-modelocked vertical external-cavity surface-emitting laser (VECSEL) at a center wavelength around 1 µm generates 122-fs pulses with 160 mW average output power and we only needed 17-pJ pulse energy coupled into a silicon nitride (Si3N4) waveguide for supercontinuum generation (SCG) and OFC offset stabilization.

Sub-150-fs pulses from an optically pumped broadband modelocked integrated external-cavity surface emitting laser.

With a modelocked integrated external-cavity surface emitting laser (MIXSEL) we achieved a pulse duration of 144 fs. The MIXSEL belongs to the family of optically pumped semiconductor disk lasers. The MIXSEL operates at a center wavelength of 1033 nm with a 13-nm full width at half maximum optical bandwidth, at a pulse repetition rate of 2.73 GHz, and at an average output power of 30 mW. This new record result was obtained with an optimized multipair dielectric top-coating, a large bandgap AlAsxP1-x material for strain compensation, a nonperiodic InGaAs quantum well gain structure, and an improved thermal management.

Catheter ablation in ASymptomatic PEDiatric patients with ventricular preexcitation: results from the multicenter "CASPED" study.

BACKGROUND: As there are limited data about the clinical practice of catheter ablation in asymptomatic children and adolescents with ventricular preexcitation on ECG, we performed the multicenter "CASPED" (Catheter ablation in ASymptomatic PEDiatric patients with Ventricular Preexcitation) study. METHODS AND RESULTS: In 182 consecutive children and adolescents aged between 8 and 18 years (mean age 12.9 ± 2.6 years; 65% male) with asymptomatic ventricular preexcitation, a total of 196 accessory pathways (APs) were targeted. APs were right sided (62%) or left sided (38%). The most common right-sided AP location was the posteroseptal region (38%). Ablation was performed using radiofrequency (RF) energy (93%), cryoablation (4%) or both (3%). Mean procedure time was 137.6 ± 62.0 min with a mean fluoroscopy time of 15.6 ± 13.8 min. A 3D mapping or catheter localization system was used in 32% of patients. Catheter ablation was acutely successful in 166/182 patients (91.2%). Mortality was 0% and there were no major periprocedural complications. AP recurrence was observed in 14/166 patients (8.4%) during a mean follow-up time of 19.7 ± 8.5 months. A second ablation attempt was performed in 20 patients and was successful in 16/20 patients (80%). Overall, long-term success rate was 92.3%. CONCLUSION: In this retrospective multicenter study, the outcome of catheter ablation for asymptomatic preexcitation in children and adolescents irrespective of antegrade AP conduction properties is summarized. The complication rate was low and success rate was high, the latter mainly depending on pathway location. The promising results of the study may have future impact on the ongoing risk-benefit discussion regarding catheter ablation in the setting of asymptomatic preexcitation in children and adolescents.

The conformational IgE epitope profile of soya bean allergen Gly m 4.

BACKGROUND: Birch pollen-related soya allergy is mediated by Gly m 4. Conformational IgE epitopes of Gly m 4 are unknown. OBJECTIVE: To identify the IgE epitope profile of Gly m 4 in subjects with birch pollen-related soya allergy utilizing an epitope library presented by Gly m 4-type model proteins. METHODS: Sera from patients with (n = 26) and without (n = 19) allergy to soya as determined by oral provocation tests were studied. Specific IgE (Bet v 1/Gly m 4) was determined by ImmunoCAP. A library of 59 non-allergenic Gly m 4-type model proteins harbouring individual and multiple putative epitopes for IgE was tested in IgE binding assays. Primary, secondary and tertiary protein structures were assessed by mass spectrometry, circular dichroism and nuclear magnetic resonance spectroscopy. RESULTS: All subjects were sensitized to Gly m 4 and Bet v 1. Allergen-specific serum IgE levels ranged from 0.94 to > 100 kUA /L. The avidities of serum IgE were 5.06 ng (allergic) and 1.8 ng (tolerant) as determined by EC50 for IgE binding to Gly m 4. 96% (46/48) of the protein variants bound IgE. Model proteins had Gly m 4-type conformation and individual IgE binding clustered in six major surface areas. Gly m 4-specific IgE binding could be inhibited to up to 80% by model proteins harbouring individual IgE binding sites in an epitope-wise equimolar fashion. Receiver operating curve analysis revealed an area under fitted curve of up to 0.88 for model proteins and 0.66 for Gly m 4. CONCLUSION AND CLINICAL RELEVANCE: Serum levels and avidity of Gly m 4-specific IgE do not correlate with clinical reactivity to soya. Six IgE-binding areas, represented by 23 amino acids, account for more than 80% of total IgE binding capacity of Gly m 4. Model proteins may be used for epitope-resolved diagnosis to differentiate birch-soya allergy from clinical tolerance.

Echocardiographic measurements of cardiac dimensions correlate better with body length than with body weight or body surface area.

Looking after children means caring for very small infants up to adult-sized adolescents, with weights ranging from 500 g to more than 100 kg and heights ranging from 25 to more than 200 cm. The available echocardiographic reference data were drawn from a small sample, which did not include preterm infants. Most authors have used body weight or body surface area to predict left ventricular dimensions. The current authors had the impression that body length would be a better surrogate parameter than body weight or body surface area. They analyzed their echocardiographic database retrospectively. The analysis included all available echocardiographic data from 6 June 2001 to 15 December 2011 from their echocardiographic database. The authors included 12,086 of 26,325 subjects documented as patients with normal hearts in their analysis by the examining the pediatric cardiologist. For their analysis, they selected body weight, length, age, and aortic and pulmonary valve diameter in two-dimensional echocardiography and left ventricular dimension in M-mode. They found good correlation between echocardiographic dimensions and body surface area, body weight, and body length. The analysis showed a complex relationship between echocardiographic measurements and body weight and body surface area, whereas body length showed a linear relationship. This makes prediction of echo parameters more reliable. According to this retrospective analysis, body length is a better parameter for evaluating echocardiographic measurements than body weight or body surface area and should therefore be used in daily practice.

Association of intraoperative blood pressure instability with adverse outcomes after liver transplantation.

BACKGROUND: Blood pressure derangements are common in orthotopic liver transplantation (OLT), and are potentially associated with adverse outcomes if they are sustained. While this concept is often believed to be true, few have rigorously demonstrated the validity of this claim, especially in likely vulnerable OLT patients. METHODS: We retrospectively investigated 827 patients who underwent OLT to determine the magnitude of these hemodynamic associations with adverse outcomes. The median value of the mean arterial pressure (MAP) and the fractional change in the median MAP between subsequent epochs (FCM) were calculated for every 5-minute epoch intraoperatively. Epochs were classified according to prespecified ranges of MAP and fractional changes in MAP (lability) between epochs. Multivariate stepwise logistic regression was used to model associations of risk factors and epochs of intraoperative blood pressure (BP) instability with primary (30-day mortality and/or graft failure) and secondary adverse outcomes. RESULTS: Primary adverse outcomes occurred in 10.9% and 12.2% of patients for 30-day mortality and 30-day graft failure, respectively. Independent hemodynamic predictors for 30-day mortality and graft failure included sustained periods of MAP <50 mmHg and BP lability where the MAP changed >25%. All of these values were statistically significant. CONCLUSION: Although severe intraoperative hypotension and BP lability during OLT are often observed in current practice as consequences of major surgical manipulations and patient vulnerability, these are likely not benign conditions based on this retrospective analysis. Prospective trials are warranted to investigate the possibility that interventions tailored to avoidance of hypotension and BP lability may improve outcomes.

Successful cardiac resynchronization therapy in a 9-year-old boy with dilated cardiomyopathy.

Despite increasing clinical impact of cardiac resynchronization therapy (CRT) with av-synchronous biventricular pacing in adults with dilated cardiomyopathy (DCMP), an ejection fraction (EF) of less than 35% and left bundle branch block (LBBB), there is still only little experience in children. We report on a 9-year-old boy with histologically proven DCMP and LBBB who had fulfilled the criteria for heart transplantation (HTX) after cardiac decompensation including catecholamine therapy. A transvenous CRT pacing system was implanted without technical difficulties. The healing process was uneventful. With optimized AV-interval invasive evaluation during implantation indicated a 16% pulse pressure increase and a 63% augmentation of LV dp/dt by pacing the LV 20 ms prior to the RV. Tissue Doppler imaging demonstrated complete LV resynchronization. Physical capacity increased and HTX could be delayed.

[Evaluation of abnormal myocardial wall motions in patients with univentricular heart by tissue Doppler echocardiography]. / Evaluation abnormer Myokardwandgeschwindigkeiten des univentrikulären Herzens mittels Gewebedoppler-Echokardiographie.

INTRODUCTION: Assessment of systolic and diastolic ventricular function in children and adults with morphologically and functionally univentricular heart is difficult using the conventional echocardiographic methods. Quantitative assessment of systolic and diastolic wall motion by TDE may provide information on abnormal systolic and diastolic ventricular function. Thus, the object of this study was to analyze the patterns of anterior and posterior wall motions in children with univentricular heart after palliative Fontan operation in comparison to normal subjects. PATIENTS AND METHODS: We investigated 21 patients of an average age of 10.1 years (range 4.2 to 32 years) with the primary diagnosis of univentricular heart and tricuspid atresia after a median period of 4.3 (range 1.2 to 8) years after cavo-pulmonary anastomosis (Fontan procedure) and in comparison to a normal collective of children without cardiovascular malformations. For investigation we used the novel tissue Doppler echocardiography (TDE) (EchoPack 6.3.6, Vingmed, Norway). Thereby we chose the standardized apical view and evaluated the left and right annular systolic (S(T)), early diastolic (E(T)) and atrial (A(T)) motion. We also registered the acceleration and deceleration time of each obtained curve. RESULTS: In comparison to the posterior myocardial wall the velocities at the anterior wall of the rudimentary ventricle were significantly reduced in all patients with tricuspid atresia and univentricular heart (p<0.0001). Particularly the annular systolic and diastolic wall motions of the rudimentary ventricle as well as their deceleration and acceleration time in patients with univentricular hearts differed significantly from those in healthy persons. CONCLUSION: Abnormal myocardial wall motion is detectable in children and adults with univentricular heart after palliative cardiac procedures using tissue Doppler echocardiography. The hemodynamic value of the measured abnormal wall motions, however, need further comparative studies.

Antibradycardia pacing in patients with congenital heart disease: experience with automatic threshold determination and output regulation (Autocapture).

AIMS: The purpose of this study was to reevaluate whether St Jude Medical's Autocapture algorithm (AC) with beat-to-beat capture confirmation, automatic pacing threshold determination and output adjustment can be applied to paced patients with congenital heart disease (CHD). METHODS AND RESULTS: 30 patients with CHD received a transvenous (group A: n=22) or epicardial (group B: n=8) single (n=7) or dual chamber (n=23) AC pacemaker for antibradycardia pacing. As a safe AC function is ensured only if a sufficient evoked response (ER) and a low lead polarization amplitude (LPA) are present, these parameters were reevaluated from 112 follow-up studies with respect to AC-function. In all but one transvenous system AC correctly functioned. AC was recommended in 5/8 patients with epicardial leads but correct AC function was preserved in only 3 patients. CONCLUSION: These data suggest that the application of the AC algorithm is safe in patients with CHD when transvenous leads are used. Whether appropriate AC function is possible with epicardial leads needs individual verification.

Early and medium-term results after modified Fontan operation in adults.

OBJECTIVE: Single ventricle palliation is rarely performed in adults and the results are less optimal than in children. In this article we analyze our experience with the modified Fontan operation in this age group. METHODS: Data of 15 consecutive patients with single ventricle with a mean age of 26 (range 16-38) years, who underwent Fontan operation between 3/92 and 1/2000 were retrospectively analyzed. Five patients had previously had an aortopulmonary shunt in childhood and two patients had previously received a bi-directional cavopulmonary shunt as adults. Eleven patients were preoperatively in NYHA class III and four in class II. The main factors for the selection of the patients before surgery were well-developed pulmonary arteries with lower lobe index 120+30 mm/m(2), pulmonary artery pressure <18 mmHg, good cardiac function and enddiastolic systemic ventricular pressure <12 mmHg. The lateral tunnel Fontan operation (LTFO) was performed in ten patients and extracardiac Fontan operation (ECFO) in five. A fenestration 4-5 mm in size was constructed in all patients with LTFO and in three of five patients with ECFO. RESULTS: There was one intraoperative and one late death (total mortality 13%). The mean extubation time and hospital stay were 24 h and 21 days, respectively. Severe postoperative complications were observed in three patients (20%). Two LTFO patients out of a total of eight patients (53%) with perioperative arrhythmias received a permanent pacemaker due to bradyarrhythmia. During the median follow-up of 5.0 (range 2.3-10.1) years, four patients developed arrhythmias; one of them had new onset bradyarrhythmia after LTFO and required permanent pacemaker implantation. The median postoperative oxygen saturation was 93% (range 90-98%). NYHA class improved significantly in 12 survivors. Cardiac catheterization (0.5-4 years postoperatively, n=12) showed excellent Fontan hemodynamics in all patients. CONCLUSIONS: The modified Fontan operation can be performed in adults with acceptable early and midterm mortality and morbidity and leads to either complete or marked relief of cyanosis and enhanced exercise tolerance in all survivors. Postoperative arrhythmias are one of the main drawbacks but the incidence of arrhythmias after ECFO seems to be lower. The long-term follow-up has yet to be established.

[Stent implantation as therapy of first choice in adults with coarctation]. / Stentimplantation als Therapie der ersten Wahl bei Erwachsenen mit Aortenisthmusstenose?

Stent implantation for coarctation of the aorta is an alternative to surgery or balloon dilation. We report our results in 12 patients with a median age of 22 years (10 to 28 years) and a body weight of 60 kg (32 to 97 kg). Nine patients had native stenosis and three had recoarctation after surgery. Invasively measured systolic pressure gradients ranged from 20 to 100 mmHg. Nine patients suffered from brachiocephalic hypertension. Eleven implantations were successful with a median dilatation of 17 mm (15-25 mm). Residual gradients were 0-5 mmHg in seven patients, 5-10 mmHg in three and 15 mmHg in one patient with postoperative recoarctation. Twenty-one months (2-37 months) after intervention, no hemodynamically relevant intimal proliferations, no restenosis, and no aneurysms were present. Thus, stent implantation is a very promising therapy for coarctation of the aorta in adults and is on its way to becoming the therapy of first choice.

[Pulmonary plasma catecholamine levels and pulmonary hypertension in congenital heart disease]. / Pulmonale Plasmakatecholaminspiegel bei Patienten mit angeborenen Herzfehlern und erhöhtem pulmonalarteriellen Fluss.

Plasma catecholamines may play a role in the pathogenesis of pulmonary hypertension in congenital heart disease with increased pulmonary blood flow. At cardiac catheterization, blood samples were obtained before and after passage of the lung in patients with congenital heart disease with normal pulmonary blood flow (n=39), elevated pulmonary blood flow with normal pulmonary pressure and normal pulmonary vascular resistance (PVR) in patients with atrial septal defect (ASD) (n=57) or ventricular septal defect (VSD) (n=12), and increased pulmonary blood flow, pressure and vascular resistance in patients with ASD, VSD or both (n=22), or in patients with primary pulmonary hypertension (n=4). Plasma catecholamines were determined by reversed phase high performance liquid chromatography and electrochemical detection (HPLC-ECD). In patients with elevated PVR elevated norepinephrine levels (NE) were observed. In contrast, epinephrine levels (E) were not associated with the development of pulmonary hypertension. Patients with primary pulmonary hypertension had the highest levels of NE while patients with associated Down's syndrome had significantly lower epinephrine levels. Pulmonary plasma norepinephrine levels are increased in patients with elevated pulmonary vascular resistance. Whether this phenomena is the cause or sequalae of pulmonary hypertension needs further examination. In the future, plasma catecholamines may serve as a diagnostic feature or may result in further therapeutic options.

[A delayed life-threatening complication after uneventful varicella infection: transient complete heart block]. / Späte bedrohliche Komplikation nach blande abgelaufener Varizellen-Infektion - transienter kompletter AV-Block (Fallbericht).

A 9 year old boy presented with uncharacteristic gastroenteric complaints due to a complete heart block 9 days after an uneventful varicella infection. Echocardiographically there were no signs of gross myocardial involvement. Bradydysrhythmia necessitated isoproterenol application however without the need for temporary transvenous cardiac pacing. After a short period of second-degree atrioventricular block and transient left bundle branch block the rhythm recovered completely and sinus rhythm is maintained so far. Worrying is the delayed onset of this complication after an uneventful course of a typically undangerous children's disease. Presumably a remaining inflammatory reaction in different parts of the specific conducting system has to be assumed. The long lasting prognosis of the atrioventricular conduction properties remains to be seen.

[Transthoracic pacing in a very low birth weight infant with congenital complete atrioventricular block - Case report]. / Kongenitaler AV-Block III degrees bei einem Frühgeborenen von 832 g: Möglichkeiten der passageren Herzschrittmacher-Therapie.

We report our experience of pacemaker treatment in a premature infant of 832 grams with congenital complete atrioventricular block due to maternal Sjögren's Syndrome. She was delivered by cesarean section at an estimated gestational age of 26 weeks because of fetal bradycardia, decreasing fetal movements and hydrops. Immediate postnatal transesophageal ventricular pacing was not successful, whereas transthoracic pacing with self-adhesive patch electrodes adapted to body size resulted in an effective increase of the infant's heart rate until operative application of temporary epimyocardial pacing wires ensured the external stimulation of the heart.

Preliminary analysis of arrhythmias after the Fontan operation with extracardiac conduit compared with intra-atrial lateral tunnel.

BACKGROUND: It is to be expected that avoidance of the atrial suture line during extracardiac Fontan operation (ECFO) decreases the risk of postoperative arrhythmias. METHODS: Two groups of consecutive patients (23 with lateral tunnel (LTFO) and 24 with extracardiac conduit) who underwent successful Fontan operations between 5/93 and 10/98 were comparatively analyzed. All patients had postoperatively standard ECG and 24-hour monitoring. During follow-up, all patients had 2 - 8 (mean 3) standard ECG recordings per year and 76 % of the patients a 24-hour Holter ECG once a year. RESULTS: Median follow-up after ECFO and LTFO was 2.4 years and 4.5 years, respectively. The incidence of supraventricular tachyarrhythmias and bradyarrhythmias after ECFO versus LTFO was lower early after operation and during follow-up (p < 0.05). In follow-up, 20 ECFO patients (91 %) versus 11 patients after LTFO (52 %) remained in sinus rhythm (p < 0.01). Pacemaker insertion was required in 7 (33 %) LTFO patients but none of the ECFO patients (p < 0.01). CONCLUSIONS: The extracardiac Fontan operation decreases the incidence of early and medium-term postoperative arrhythmias. Comparative long-term results are not yet available.

[DDD-pacemaker implantation in a 7-week-old infant: epicardial electrodes in intrapleural position]. / DDD-Schrittmacher-Implantation bei einem 7 Wochen alten Säugling: Epikardiale Elektroden mit intrapleuraler Aggregatlage.

Permanent pacing for complete heart block in newborns and small infants is a challenge concerning the mismatch between body size and pacemaker dimensions. As the abdominal position of the large pacemaker carries a considerable risk of healing disturbances, the intrapleural position of single chamber pacemakers is accepted as well. We report about a 7 week old infant with congestive heart failure due to a complete atrioventricular septal defect. The immature valve tissue led to recurrent, severe mitral valve incompetence and necessitated several valvuloplasty procedures and finally the implantation of a mechanical prothesis. Because of a postoperative complete heart block, a dual chamber pacemaker with epicardial steroid-eluting bipolar leads was implanted without specific fixation into the right pleural cavity during delayed sternal closure to ensure atrioventricular synchrony. Despite the capacious implant, adverse effects on hemodynamics and pulmonary function were not observed and the infant thrived normally. The DDD function of the pacemaker allowed the utilization of the infant's complete heart rate spectrum without restrictions due to the technically limited upper tracking rate of 180 bpm.

Percutaneous closure of large atrial septal defects with the Amplatzer Septal Occluder: technical overkill or recommendable alternative treatment?

To judge whether an Amplatzer Septal Occluder (ASO) can be used as a safe therapy instead of surgery for closure of large atrial septal defects > 25 mm in diameter, we report our experiences in 45 patients out of a cohort of 467 patients after successful ASO implantation within a period of 3 years. Median defect diameter was 28 mm (range 25-36), median age was 41.2 years (range 10.1-77.7 years). Body weight ranged from 33.5 to 112.0 kg (median 68 kg). Due to an inevitable reduction of the stent size with increasing distances of the discs fixed at the thicker part of the atrial septum in larger defects, we implanted devices 2-4 mm larger than the measured stretched diameter. Fluoroscopy times ranged from 2.0 to 24.4 minutes, with a median of 10.3 minutes. Follow-up studies were obtained after 48 hours and 1, 6, and 12 months, and then yearly. The median period of follow-up was 0.82 years (range 0.1-2.6). The complete occlusion rate was 91.1%. A trivial hemodynamically insignificant residual shunt remained in 8.9% of the patients. Three patients showed transient atrial tachyarrhythmias within the first 3 months after implantation and three remained in chronic atrial fibrillation. The excellent results in the short and medium term make Amplatzer device implantation a recommendable safe and effective alternative to surgery, even in selected cases with defects > 25 mm. Final judgement, however, is only possible after long-term follow-up.

Transvenous demand Pacemaker Treatment for intermittent complete Heart Block in a Cat.

A 13-year-old male neutered domestic shorthaired cat had repeated syncopal episodes over a 6 month period, which had variable duration and continued to increase in frequency. Intermittent ventricular asystole, due to complete heart block, and hyperthyroidism were documented. As the syncopal episodes did not respond to a 4-week medical treatment and symptoms became severe, a transvenous ventricular demand pacemaker system (VVIM) was implanted via the external jugular vein. The unipolar lead was tunneled subcutaneously and connected with the generator in a preformed ventral abdominal muscle pocket. During follow up of 18-months there were no recurrences of the syncopal episodes.