Hybrid pixel direct detector for electron energy loss spectroscopy.

We characterize a hybrid pixel direct detector and demonstrate its suitability for electron energy loss spectroscopy (EELS). The detector has a large dynamic range, narrow point spread function, detective quantum efficiency ≥ 0.8 even without single electron arrival discrimination, and it is resilient to radiation damage. It is capable of detecting ~5 × 106 electrons/pixel/second, allowing it to accommodate up to 0.8 pA per pixel and hence >100 pA EELS zero-loss peak (ZLP) without saturation, if the ZLP is spread over >125 pixels (in the non-dispersion direction). At the same time, it can reliably detect isolated single electrons in the high loss region of the spectrum. The detector uses a selectable threshold to exclude low energy events, and this results in essentially zero dark current and readout noise. Its maximum frame readout rate at 16-bit digitization is 2250 full frames per second, allowing for fast spectrum imaging. We show applications including EELS of boron nitride in which an unsaturated zero loss peak is recorded at the same time as inner shell loss edges, elemental mapping of an STO/BTO/LMSO multilayer, and efficient parallel acquisition of angle-resolved EEL spectra (S(q, ω)) of boron nitride.

Thromboembolic complications during weaning from right ventricular assist device support.

We report on two patients who experienced life-threatening thromboembolic complications during prolonged weaning from Levitronix CentriMag right ventricular assist device support. Right ventricular assist device flow in both patients was reduced below 2 L/min for a period of 72 or 36 h to closely monitor patients' hemodynamics and echocardiography because the extent of right ventricular recovery was difficult to assess. Thrombus formation occurred despite adjusting the heparin dosage to achieve partial prothrombin time values between 60 and 70 s. Periods of reduced flow during Levitronix CentriMag support must be kept short, and an additional bolus dose of heparin should be considered.

Successful administration of levosimendan in a patient with low-gradient low-output aortic stenosis.

Aortic valve replacement in patients suffering from low-gradient aortic stenosis and congestive heart failure is associated with high operative mortality, and the perioperative use of inotropes is common. Levosimendan is a calcium sensitizer with positive inotropic and vasodilatory effects and has been developed for treatment of decompensated heart failure. Although its use in patients with low-gradient aortic stenosis is not established, we hypothesized that it might have beneficial effects on outcome after aortic valve replacement. We report on a high-risk operation in a 73-year-old man with low-gradient aortic stenosis, congestive heart failure and coronary artery disease. Levosimendan was administered perioperatively (0.1 mg/kg/min 16 hours prior to the operation without a loading dose) and allowed rapid recovery of the patient, who required only brief treatment in the intensive care unit. No levosimendan-specific adverse events were observed, in particular no hypotension. The excellent postoperative result was maintained after the patient was discharged from hospital.

Early detection and successful therapy of fulminant chlamydia pneumoniae myocarditis.

We report a case involving a young female patient with Chlamydia pneumoniae myocarditis who required assist device therapy for acute heart failure. Early diagnosis was provided by endomyocardial biopsy, and tailored antibiotic therapy facilitated quick recovery of myocardial function. This is the first case to report detecting C pneumoniae as the pathogen responsible for fulminant myocarditis while the patient was still alive and to report long-term follow-up data.

Cardiac transplantation complicated by acute thrombotic occlusion of the right coronary artery.

We report the case of a 63-year-old male patient undergoing cardiac transplantation due to fourth time aortic valve endocarditis. The postoperative course was complicated by thrombotic occlusion of the right coronary artery (RCA) causing acute right ventricular myocardial infarction, which required extracorporeal membrane oxygenation. The RCA could be reopened by catheter-based intervention and the patient stabilized. In order to avoid further immobilization, a right ventricular assist device was implanted and an aortocoronary bypass to the RCA was performed. After that, the patient stabilized progressively, could be weaned from the assist device, and was discharged home 6 weeks after transplantation. On coronary angiography, which is routinely performed 4 to 6 weeks after transplantation, a fistula from the RCA to the right ventricle was detected which was treated conservatively. Five months after transplantation, the patient is in good clinical condition without signs of recurrent endocarditis. This case shows that intense interdisciplinary cooperation of cardiac specialists allows the successful management of very complex patients in serious clinical conditions.

Proportional assist ventilation reduces the work of breathing during exercise at moderate altitude.

Reducing the work of breathing (WOB) during exercise and thus the oxygen required solely for ventilation may be an option to increase the oxygen available for nonventilatory physiological tasks at altitude. This study evaluated whether pressure support ventilation (PSV) and proportional assist ventilation (PAV) may partially reduce WOB during exercise at altitude. Seven volunteers breathing with either PSV or PAV or without support (control) were examined for WOB, inspiratory pressure time product (iPTP), and (O(2)) before and during pedaling at 160 W for 4 min on an ergometer at an altitude of 2860 m, where barometric pressure and oxygen partial pressure are approximately 30% less than at sea level. PSV and PAV reduced WOB from 4.5 +/- 0.9 J/L(-1)/min(-1) during unsupported breathing to 3.7 +/- 0.4 (p < 0.05) and 3.2 +/- 0.7 (p < 0.01), respectively. iPTP was reduced during PAV (570 +/- 151 cm H(2)O/sec/min(-1), p < 0.01), but not during PSV (727 +/- 116, p = 0.58) compared with unsupported ventilation during exercise (763 +/- 90). During PSV and PAV breathing, higher arterial oxygen saturations (84 +/- 2%, p < 0.05, and 86 +/- 1%, p < 0.01, respectively) were observed compared with control (80 +/- 3%), indicating that PSV and PAV attenuated hypoxemia during exercise at altitude. Total body (O(2)), however, was not reduced during PSV or PAV. In conclusion, both PSV and PAV reduced the WOB during exercise at altitude, but only PAV reduces iPTP. Both modes reduce hypoxemia, which may be due to higher alveolar ventilation or decreased ventilation-perfusion heterogeneity compared to unsupported breathing.

Epidemiology of mechanical ventilation: analysis of the SAPS 3 database.

OBJECTIVE: To evaluate current practice of mechanical ventilation in the ICU and the characteristics and outcomes of patients receiving it. DESIGN: Pre-planned sub-study of a multicenter, multinational cohort study (SAPS 3). PATIENTS: 13,322 patients admitted to 299 intensive care units (ICUs) from 35 countries. INTERVENTIONS: None. MAIN MEASUREMENTS AND RESULTS: Patients were divided into three groups: no mechanical ventilation (MV), noninvasive MV (NIV), and invasive MV. More than half of the patients (53% [CI: 52.2-53.9%]) were mechanically ventilated at ICU admission. FIO2, VT and PEEP used during invasive MV were on average 50% (40-80%), 8 mL/kg actual body weight (6.9-9.4 mL/kg) and 5 cmH2O (3-6 cmH2O), respectively. Several invMV patients (17.3% (CI:16.4-18.3%)) were ventilated with zero PEEP (ZEEP). These patients exhibited a significantly increased risk-adjusted hospital mortality, compared with patients ventilated with higher PEEP (O/E ratio 1.12 [1.05-1.18]). NIV was used in 4.2% (CI: 3.8-4.5%) of all patients and was associated with an improved risk-adjusted outcome (OR 0.79, [0.69-0.90]). CONCLUSION: Ventilation mode and parameter settings for MV varied significantly across ICUs. Our results provide evidence that some ventilatory modes and settings could still be used against current evidence and recommendations. This includes ventilation with tidal volumes >8mL/kg body weight in patients with a low PaO2/FiO2 ratio and ZEEP in invMV patients. Invasive mechanical ventilation with ZEEP was associated with a worse outcome, even after controlling for severity of disease. Since our study did not document indications for MV, the association between MV settings and outcome must be viewed with caution.

The pediatric mechanical circulatory support program in Innsbruck, Austria, and the impact of such programs on lack of donor hearts in Europe.

Strategy and results of the Innsbruck Mechanical Circulatory Support Program are presented, and the impact of such programs on pediatric heart transplantation (HTX) in Europe is discussed. Venoarterial extracorporeal membrane oxygenation (vaECMO) and ventricular assist devices (VADs) were used in 21 pediatric patients (median age 3.3 years, 2 days to 17 years) for acute heart failure (AHF) following a bridge or bridge-to-bridge strategy. Twelve patients were treated with vaECMO: eight were weaned after 2-10 days, two died, and two were switched to a VAD. Of the last, one was weaned 47 days later and the other underwent HTX 168 days later. In nine patients, VAD was implanted without preceding vaECMO. One such patient died (cerebral hemorrhage) after 236 days; of the remaining eight patients three were weaned and five underwent HTX. Waiting time for HTX (high-urgency status) varied from 4 to 372 days. Fifteen patients were discharged (follow up: 2-74 months); 14 are doing very well (New York Heart Association (NYHA) Functional Classification Class I, neurologically normal), whereas one suffers from severe neurologic damage, presumably from resuscitation before vaECMO. Data from Eurotransplant on pediatric HTX in 2004, 2005, and 2006 (33, 49, and 34 transplanted hearts, respectively; recipients <16 years of age) are discussed. Mechanical circulatory support (MCS) substantially improves survival with AHF in pediatric patients. Medium-term support (up to 400 days in our patients) is possible and outcome of survivors is excellent. Wide spread use of MCS might slightly aggravate the lack of donor organs, which could result in longer support times.

Outcome evaluation of the bridge-to-bridge concept in patients with cardiogenic shock.

BACKGROUND: Patients with cardiogenic shock can be stabilized by percutaneous implantation of extracorporeal membrane oxygenation (ECMO). If weaning from ECMO is impossible, the implantation of a ventricular assist device (VAD) is required. Patients either go for recovery of myocardial function (bridge to recovery) or for heart transplantation (bridge to transplant). METHODS: One hundred thirty-one patients were supported with ECMO between March 1995 and November 2005. Reasons for ECMO implantation were acute heart failure, acute or chronic heart failure, and postcardiotomy heart failure. In 28 patients, subsequent VAD implantation was necessary (bridge to bridge concept). RESULTS: Fourteen bridge to bridge patients (50%) became long-time survivors with a mean follow-up of 39 months. Risk factors for mortality were status post-cardiopulmonary resuscitation and elevated lactate and bilirubin levels before VAD implantation. Complications after ECMO and VAD implantation were bleeding and thromboembolic events. The most common cause of death was multiorgan failure. CONCLUSIONS: Bridge to bridge is a successful concept for selected patients with cardiogenic shock. During ECMO support, patients can be evaluated for comorbidities. For patients with a combination of risk factors (status post-cardiopulmonary resuscitation, elevated lactate levels, and impaired liver function), VAD implantation should be considered very carefully.

Interventional and medical treatment of acute heart failure due to inflammation: four cases.

Four patients (aged 15-41 years, mean age 26.7 years) with fulminant myocarditis undergoing mechanical circulatory support are reported. All patients suffered from acute low-output syndrome refractory to inotropic support. Diagnosis was confirmed by histology and immunohistochemistry. RT-PCR (reverse transcription-polymerase chain reaction) from endomyocardial biopsy specimens revealed parvovirus B19 in two patients and a coinfection with Chlamydia pneumoniae and parvovirus B19 in one patient. Midterm support with the biventricular Thoratec system was preceded by implantation of an extracorporeal membrane oxygenation (ECMO) device in two patients. Two patients regained full cardiac function and were successfully weaned from the ventricular assist device (VAD) after 12 and 40 days. Heart transplantation was performed in another patient without evidence of myocardial recovery after 53 days. One patient died of cerebral hemorrhage on day 12 after VAD implantation. In summary, patients with life-threatening fulminant myocarditis can be successfully bridged to recovery or transplantation with mechanical circulatory support.

Experience with percutaneous venoarterial cardiopulmonary bypass for emergency circulatory support.

OBJECTIVE: Mechanical circulatory support can maintain vital organ perfusion in patients with cardiac failure unresponsive to standard pharmacologic treatment. The purpose of the current study was to report complication and survival rates in patients supported with emergency percutaneous venoarterial cardiopulmonary bypass because of prolonged cardiogenic shock or cardiopulmonary arrest. DESIGN: Retrospective clinical study. SUBJECTS: A total of 46 patients supported with venoarterial cardiopulmonary bypass, 25 because of cardiogenic shock unresponsive to pharmacologic therapy and 21 because of cardiopulmonary arrest unresponsive to standard advanced cardiac life support. RESULTS: In 41 of the 46 patients (89%), stable extracorporeal circulation was established; in five patients (11%), femoral cannulation was accomplished only after a surgical cutdown. A total of 28 patients were weaned from cardiopulmonary bypass (19 of 25 patients with cardiogenic shock vs. 9 of 21 patients with cardiopulmonary arrest, p =.03), and 13 patients had long-term survival (10 of 25 patients with cardiogenic shock vs. 3 of 21 patients with cardiopulmonary arrest, p =.1). Complications directly related to the use of cardiopulmonary bypass were found in 18 patients (39%), major complications related to femoral cannulation being the most common single cause for bypass-associated morbidity (eight patients, 17%). CONCLUSIONS: Long-term survival rates after emergency percutaneous cardiopulmonary bypass are encouraging in patients with an underlying cardiocirculatory disease amenable to immediate corrective intervention (angioplasty, surgery, transplantation).