Feasibility of customised unipolar conversion using bipolar temporary pacing wires in patients after surgical repair of congenital heart disease.

OBJECTIVE: Temporary pacing wires play a crucial role in the diagnosis and therapy of post-operative arrhythmia after surgery for congenital heart disease. At present, bipolar pacing wires are used in most institutions. In case of functional failure of these wires, a unipolar mode of stimulation and sensing should be theoretically possible as a rescue procedure. METHODS: We tested the feasibility of the customised unipolar mode in 18 post-operative patients with congenital heart disease (age 9.2 ± 13.9 months, weight 6.3 ± 3.8 kg, and cardiopulmonary bypass time 70 ± 29 minutes). As there are two possible unipolar configurations, there are twice the number of testing parameters; of those, we compared sensing (mV) and pacing thresholds (V at 0.5 ms). RESULTS: Atrial sensing was significantly better in the unipolar modes (p < 0.001, p < 0.003). The ventricular unipolar sensing did not differ significantly in the "better" of the two possible configurations from the bipolar values (p = 0.363). For the unipolar pacing thresholds, only the "better" unipolar configuration did not differ significantly from the bipolar measurements (atrial: p = 0.058, ventricular: p = 0.138). There was no exit block or undersensing. CONCLUSION: The results demonstrate that unipolar stimulation and sensing using bipolar epicardial temporary pacing wires is feasible. In the case of failure of bipolar temporary pacing wires, this modality represents an easy rescue measure that in such cases should always be considered.

Synthesis of taurine-Cu3(PO4)2 hybrid nanoflower and their peroxidase-mimic and antimicrobial properties.

Herein, we report the synthesis of taurine incorporated (sulfur containing organic molecule derived from methionine and cysteine) hybrid nanoflowers (thNFs) with an intrinsic peroxidase-mimic and antimicrobial activities in the presence of H2O2. Formation of thNFs using non-enzyme molecules was for the first time and systematically studied as a function of the taurine concentration, types of metal ions (Cu2+, Fe2+ and Fe3+) and pH values of reaction solution. The peroxidase like activities of thNFs rely on Fenton-like reaction against guaiacol used as a model substrate. The efficiency of Fenton reaction can be attributed to porous structure and presence of ions of transition elements in the thNFs. The thNFs were further characterized using FTIR, XRD, SEM and EDX. The thNFs also showed remarkable antimicrobial properties against S. aureus, E. coli, B. cereus and C. albicans. We claim that nonprotein-based NFs can be considered as new generation nano-biocatalysts as an alternative to enzymes and can be used in various medicinal, biochemical, immunological, biotechnological, and industrial applications.

[Evaluation of tularemia cases originated from Central Anatolia, Turkey]. / Orta Anadolu Kaynakli Tularemi Olgularinin Degerlendirilmesi.

Tularemia is an infection caused by Francisella tularensis with a worldwide distribution and diverse clinical manifestations. In recent years, tularemia cases are increasing in Turkey, with a special attention to Marmara, western Blacksea and Central Anatolia regions. The aim of this study was to evaluate tularemia cases admitted to our hospital during an outbreak emerged at Central Anatolia between December 2009 and September 2010, making a point for the disease. A total of 32 patients (17 female, 15 male; age range: 15-80 years, mean age: 41 ± 16 years) with fever, sore throat, cervical mass and failure to respond to beta-lactam antibiotics, were followed up with the preliminary diagnosis of tularemia. The diagnosis was confirmed by specific laboratory tests. Serum samples were obtained from 25 patients and in 17 (68%) of them microagglutination test yielded positive result (≥ 1/160) in their first serum samples. All of the 8 patients who had negative results in their first samples (< 1/160), revealed seroconversion in their second samples. In 10 (91%) of the 11 patients from whom lymph node aspirates were obtained, PCR performed with species specific (tul4) primers yielded positivity and subspecies differentiation done by RD1 primers identified the agent as F.tularensis subspecies holarctica. F.tularensis growth was not detected in the cultures of lymph aspirates and/or throat swabs of the cases (n= 16). All the patients had oropharyngeal tularemia and eight of them also had oculoglandular form. The mean duration of the symptoms were 25.6 ± 17.2 (2-60) days. They had a history of oral intake of contaminated water. Cervical or submandibular lymphadenopathy were detected in all patients. One patient had cervical abscess and the other one had erythema nodosum. Elevated sedimentation rate was found in 26 (81.3%) patients and elevated CRP in 24 (75%) patients. Spontaneous drainage was detected in nine cases during follow-up. Lymph node aspiration was performed in patients when fluctuation was detected. Streptomycin 2 g/day for 10 days was given to 21 patients and doxycycline 2 x 100 mg for 14 days was given to 11 patients. Twelve (37.5%) patients received further antibiotic treatment since they failed to respond to the first therapy. Of the patients, 21 recovered completely and two patients had lymph node excision. No severe complications were observed. The patients who applied to the hospital within 10 days of the initiation of the symptoms were treated successfully, while the others that applied later were not. In conclusion, tularemia which is an endemic disease in Turkey, should be kept in mind in patients with fever, sore throat and lymphadenopathy.

Measuring myocardial extracellular volume of the right ventricle in patients with congenital heart disease.

The right ventricle´s (RV) characteristics-thin walls and trabeculation-make it challenging to evaluate extracellular volume (ECV). We aimed to assess the feasibility of RV ECV measurements in congenital heart disease (CHD), and to introduce a novel ECV analysis tool. Patients (n = 39) and healthy controls (n = 17) underwent cardiovascular magnetic resonance T1 mapping in midventricular short axis (SAX) and transverse orientation (TRANS). Regions of interest (ROIs) were evaluated with regard to image quality and maximum RV wall thickness per ROI in pixels. ECV from plane ROIs was compared with values obtained with a custom-made tool that derives the mean T1 values from a "line of interest" (LOI) centered in the RV wall. In CHD, average image quality was good (no artifacts in the RV, good contrast between blood/myocardium), and RV wall thickness was 1-2 pixels. RV ECV was not quantifiable in 4/39 patients due to insufficient contrast or wall thickness < 1 pixel. RV myocardium tended to be more clearly delineated in SAX than TRANS. ECV from ROIs and corresponding LOIs correlated strongly in both directions (SAX/TRANS: r = 0.97/0.87, p < 0.001, respectively). In conclusion, RV ECV can be assessed if image quality allows sufficient distinction between myocardium and blood, and RV wall thickness per ROI is ≥ 1 pixel. T1 maps in SAX are recommended for RV ECV analysis. LOI application simplifies RV ECV measurements.

Magnetic resonance imaging-guided balloon angioplasty of coarctation of the aorta: a pilot study.

BACKGROUND: MRI guidance of percutaneous transluminal balloon angioplasty (PTA) of aortic coarctation (CoA) would be desirable for continuous visualization of anatomy and to eliminate x-ray exposure. The aim of this study was (1) to determine the suitability of MRI-controlled PTA using the iron oxide-based contrast medium Resovist (ferucarbotran) for catheter visualization and (2) to subsequently apply this technique in a pilot study with patients with CoA. METHODS AND RESULTS: The MRI contrast-to-noise ratio and artifact behavior of Resovist-treated balloon catheters was optimized in in vitro and animal experiments (pigs). In 5 patients, anatomy of the CoA was evaluated before and after intervention with high-resolution respiratory-navigated 3D MRI and multiphase cine MRI. Position monitoring of Resovist-treated catheters was realized with interactive real-time MRI. Aortic pressures were continuously recorded. Conventional catheterization was performed before and after MRI to confirm interventional success. During MRI, catheters filled with 25 micromol of iron particles per milliliter of Resovist produced good signal contrast between catheters and their background anatomy but no image distortion due to susceptibility artifacts. All MRI procedures were performed successfully in the patient study. There was excellent agreement between the diameters of CoA and pressure gradients as measured during MRI and conventional catheterization. In 4 patients, PTA resulted in substantial widening of the CoA and a decrease in pressure gradients. In 1 patient, PTA was ineffective. CONCLUSIONS: The MRI method described represents a potential alternative to conventional x-ray fluoroscopy for catheter-based treatment of patients with CoA.

Cardiac T1 mapping in congenital heart disease: bolus vs. infusion protocols for measurements of myocardial extracellular volume fraction.

Myocardial extracellular volume fraction (ECV) reflecting diffuse myocardial fibrosis can be measured with T1 mapping cardiovascular magnetic resonance (CMR) before and after the application of a gadolinium-based extracellular contrast agent. The equilibrium between blood and myocardium contrast concentration required for ECV measurements can be obtained with a primed contrast infusion (equilibrium contrast-CMR). We hypothesized that equilibrium can also be achieved with a single contrast bolus to accurately measure diffuse myocardial fibrosis in patients with congenital heart disease (CHD). Healthy controls (n = 17; median age 24.0 years) and patients with CHD (n = 19; 25.0 years) were prospectively enrolled. Using modified Look-Locker inversion recovery T1 mapping before, 15 min after bolus injection, and during constant infusion of gadolinium-DOTA, T1 values were obtained for blood pool and myocardium of the left ventricle (LV), the interventricular septum (IVS), and the right ventricle (RV) in a single midventricular plane in short axis or in transverse orientation. ECV of LV, IVS and RV by bolus-only and bolus-infusion correlated significantly in CHD patients (r = 0.94, 0.95, and 0.74; p < 0.01, respectively) and healthy controls (r = 0.96, 0.89, and 0.64; p < 0.05, respectively). Bland-Altman plots revealed no significant bias between the techniques for any of the analyzed regions. ECV of LV and RV myocardium measured by bolus-only T1 mapping agrees well with bolus-infusion measurements in patients with CHD. The use of a bolus-only approach facilitates the integration of ECV measurements into existing CMR imaging protocols, allowing for assessment of diffuse myocardial fibrosis in CHD in clinical routine.

Magnetic resonance imaging analysis of right ventricular pressure-volume loops: in vivo validation and clinical application in patients with pulmonary hypertension.

BACKGROUND: The aims of this study were to validate MRI-derived right ventricular (RV) pressure-volume loops for assessment of RV myocardial contractility and then to apply this technique in patients with chronic RV pressure overload for assessment of myocardial contractility, ventricular pump function, and VA coupling. METHODS AND RESULTS: Flow-directed catheters were guided under MR fluoroscopy (1.5 T) into the RV for invasive pressure measurements. Simultaneously, ventricular volumes and myocardial mass were assessed from cine MRI. From sampled data, RV pressure-volume loops were constructed, and maximal ventricular elastance indexed to myocardial mass (E(max_i)) was derived by use of a single-beat estimation method. This MRI method was first validated in vivo (6 swine), with conductance techniques used as reference. Bland-Altman test showed good agreement between methods (E(max_i)=5.1+/-0.5 versus 5.8+/-0.7 mm Hg x mL(-1) x 100 g(-1), respectively; P=0.08). Subsequently, the MRI method was applied in 12 subjects: 6 control subjects and 6 patients with chronic RV pressure overload from pulmonary hypertension. In these patients, indexes of RV pump function (cardiac index), E(max_i), and VA coupling (E(max)/E(a)) were assessed. In patients with pulmonary hypertension, RV pump function was decreased (cardiac index, 2.2+/-0.5 versus 2.9+/-0.4 L x min(-1) x m(-2); P<0.01), myocardial contractility was enhanced (E(max_I), 9.2+/-1.1 versus 5.0+/-0.9 mm Hg x mL(-1) x 100 g(-1); P<0.01), and VA coupling was inefficient (E(max)/E(a), 1.1+/-0.3 versus 1.9+/-0.4; P<0.01) compared with control subjects. CONCLUSIONS: RV myocardial contractility can be determined from MRI-derived pressure-volume loops. Chronic RV pressure overload was associated with reduced RV pump function despite enhanced RV myocardial contractility. The proposed MRI approach is a promising tool to assess RV contractility in the clinical setting.

Catheter visualization with resonant markers at MR imaging-guided deployment of endovascular stents in swine.

PURPOSE: To evaluate resonant circuits as markers for magnetic resonance (MR) imaging-guided placement of nitinol stents. MATERIALS AND METHODS: The study was approved by the institutional animal research committee and complied with National Institutes of Health guidelines for care and use of laboratory animals. Resonant circuits similar to catheter markers used at conventional angiography were placed proximally and distally to a nitinol stent in a stent delivery system. Resonant circuits were tested in vitro and in vivo for signal intensity levels that would enable visualization during MR imaging-guided stent deployment. Experiments were conducted by using real-time imaging with a 1.5-T unit. Stents (n = 9) were deployed in the vena cava (n = 2), abdominal aorta (n = 2), isthmus of the aorta (n = 2), and carotid (n = 2) and iliac (n = 1) arteries in five pigs. After intervention, the site of the stent was investigated with balanced fast field-echo MR imaging and contrast material-enhanced MR angiography. Blood flow velocities were measured in the stent lumen and next to the stent with velocity-encoded cine MR imaging. Level of agreement was determined with Bland-Altman analysis. RESULTS: During all interventions, resonant circuits provided highly visible MR signal that allowed fast and reliable visualization of the stent delivery system. Borders of loaded stents were clearly marked, which allowed precise stent placement in all experiments. Balanced fast field-echo MR imaging and contrast-enhanced MR angiography provided information about immediate postintervention position. Positions depicted on MR images were found accurate at postmortem examination. Results of Bland-Altman analysis showed good agreement between blood flow velocities measured in and next to the stent lumen, with a mean difference of -9 cm/sec +/- 5 (standard deviation). CONCLUSION: Resonant circuits are well suited for use at deployment of endovascular stents.