The role of FDG-PET-CT in pediatric cardiac patients and patients with congenital heart defects.

AIM: Medical imaging by using FDG-PET/CT (PET-CT) can detect, confirm or eliminate with high sensitivity areas of suspected infections in case of persistent fever of unknown origin in combination with other bacteriological examinations. The aim of this study was to assess the potential role of PET-CT in detecting or excluding infections or other inflammatory processes in patients with congenital heart defects (CHD). In addition we wanted to evaluate the practical impact of PET-CT on the subsequent clinical management. METHODS: In this retrospective study we analyzed the data of all CHD patients who underwent PET-CT over a 5year period in our institution. The results were then evaluated with regard to the potential impact on clinical decision making. RESULTS: Between 2010 and 2015 PET-CT was performed in 30 patients. The mean age was 26years (SD 15years, range 1 to 66years). The diagnoses covered a large field of CHD. 11 patients (4/11 with assist device) were assessed before heart transplantation; suspected malignancies or infections were excluded and transplant listing was possible. In another 5/6 patients suspected assist device infection could be confirmed with PET/CT. Endocarditis was suspected in 13 patients, 2 of whom underwent previous MRI without confirmation and ECHO was inconclusive. Endocarditis was finally excluded in 5/13 patients but confirmed in 8/13 patients by PET-CT. CONCLUSION: In this study we could show a high sensitivity of PET-CT for specific localization of infections and with high impact on subsequent therapy. Based on this results clinical management could be targeted and adapted. We could demonstrate that PET-CT has a high impact on the subsequent clinical therapy.

Assessment of myocardial scarring by contrast enhanced magnetic resonance imaging in a patient 11 years after percutaneous transluminal septal myocardial ablation in hypertrophic obstructive cardiomyopathy.

We report on a 60 year-old male who was one of the first patients who underwent percutaneous transluminal septal myocardial ablation (PTSMA) in our institution in 1996. Contrast enhanced cardiac magnetic resonance imaging (MRI) 11 years after the PTSMA demonstrated extensive scarring, in septal and inferior segments of the left ventricle, and an excellent functional result. It has been previously demonstrated that contrast-enhanced MRI allows detailed evaluation of size and location of septal myocardial infarction induced by PTSMA, and that infarction size detected by MRI correlates well with clinical indexes of infarct size. Our case report underlines the importance of ongoing specialized care and reassessment of patients after PTSMA including continuous clinical risk assessment.

An echocardiographic and magnetic resonance imaging comparative study of right ventricular volume determination.

Assessment of right ventricular volume and function is important in many clinical settings involving heart or lung disease. However, the complexity of the right ventricular anatomy has prevented accurate volume determination by two-dimensional echocardiography. In the present study, 5 models incorporating standard echocardiographic views, were used to determine right ventricular volume in 10 human subjects. Two models were contingent on the true crescentic appearance of the right ventricle, whereas the remaining 3 calculated the right ventricular volume as a pyramid, an ellipsoid or other tapering geometrical figures, respectively. Subsequently, echocardiographic right ventricular volumes were compared to magnetic resonance imaging derived volumes. Correlation analysis and agreement measurement between the echocardiographic and magnetic resonance end-diastolic volume were performed in 10 out of 10 subjects and in 9 out of 10 subjects for the end-systolic volume. The 2 crescentic models resulted in the most reliable estimation of right ventricular volume. Those findings suggest that models based on right ventricular anatomical landmarks are feasible and should be preferred in echocardiographic studies.

[Tachycardia-induced syncopes]. / Tachyarrhythmiebedingte Synkopen.

In 50% of the patients presenting with a syncope, the cause is cardiac. The incidence of sudden death with 24% is high in this group. Since most of the tachycardia-induced syncopes are due to ventricular tachycardia (VT), a careful diagnostic approach must be used. The possibility of a VT to end in a fibrillation is great, especially in the presence of a organic heart disease, which leads to a bad prognosis in such patients. The aim of a careful anamnesis and clinical history is to establish the presence of a cardiac disease. A Wolff-Parkinson-White syndrome, a long QT, an old myocardial infarction or a coronary artery disease (CAD) can be assessed by echocardiography (ECG). Stress testing is useful in evaluating a CAD and can possibly lead to a diagnosis when a VT or a supraventricular tachycardia (SVT) is induced. ECG is used to assess the cardiac ejection fraction and in the evaluation of a suspected right or left cardiomyopathy. The ambulatory ECG allow a diagnosis only in 2 to 3% of the cases. Nevertheless, the presence of more than 10 PVC/h and/or asymptomatic nonsustained VT is a predictor for sudden death in syncopy patients. Detection of late potentials has a sensitivity of 50 to 83% and a sensibility of 89 to 91% for the prediction of inducible sustained VT during electrophysiological studies (EPS) in patients with syncope. However, the usefulness of this technique is not fully established, since there is no significant difference in survival or recurrence of syncope between patients with and without late potentials. The EPS is an invasive technique and therefore used at the end of the investigations. The cardiovascular mortality is low (4%) in patients with a negative EPS. A treatment is mandatory in tachycardia-induced syncopes even when the cause is a SVT. Antiarrhythmic drugs are useful for the treatment of SVT. However, radiofrequency ablation of the accessory pathway is preferable, since the success rate is over 90%, and the side effects of chronic ingestion of antiarrhythmic drugs can therefore be avoided. Some VT can be treated successfully with drugs under the control of an EPS, but most of the patients must have the implantation of an internal cardiac defibrillator (ICD).

Doppler echocardiographic assessment of the new ATS medical prosthetic valve in the aortic position.

Advancing The Standard (ATS) Medical (ATS Medical Inc., Minneapolis, MN) is a new mechanical bileaflet valve, composed of pyrolitic carbon. The aim of this study was to define in a blinded manner the Doppler echocardiographic characteristics of normally functioning ATS Medical prostheses with respect to their size. Forty consecutive patients (29 men, mean age 58 +/- 13 years), clinically stable, and without evidence of valve dysfunction, were studied from 1993 to 1995. Doppler echocardiography was performed at least 3 months after valve replacement with ATS Medical valves (5 n degrees 21, 8 n degrees 23, 12 n degrees 25, 10 n degrees 27, 5 n degrees 29). Maximum and mean transprosthetic pressure gradients were calculated by the simplified Bernoulli equation. Functional valve surface area was assessed by the continuity equation using the external diameter of the prostheses to calculate the subaortic surface area. The Doppler velocity index was obtained by the ratio of subaortic and transaortic velocities and the performance index was calculated dividing the effective orifice area by the actual orifice area. For the most commonly used aortic valve (25 mm), the maximum pressure gradient was 17 +/- 8 mmHg, the mean gradient 11 +/- 4 mmHg, the functional surface area 2.2 +/- 0.4 cm2, the Doppler velocity index 0.44 +/- 0.07, and the performance index 0.68 +/- 0.11. This study provides the normal range for Doppler hemodynamic characteristics of the various sizes of the ATS valve.

Nosocomial pneumonia in mechanically ventilated patients receiving antacid, ranitidine, or sucralfate as prophylaxis for stress ulcer. A randomized controlled trial.

OBJECTIVE: To assess three anti-stress ulcer prophylaxis regimens in mechanically ventilated patients for bacterial colonization, early- and late-onset nosocomial pneumonia, and gastrointestinal bleeding. DESIGN: Randomized controlled trial. PATIENTS: Consecutive eligible patients with mechanical ventilation and a nasogastric tube. Of 258 eligible patients, 244 were assessable. SETTING: Medical and surgical intensive care units. INTERVENTION: At intubation, patients were randomly assigned to receive one of the following: antacid (a suspension of aluminum hydroxide and magnesium hydroxide), 20 mL every 2 hours; ranitidine, 150 mg as a continuous intravenous infusion; or sucralfate, 1 g every 4 hours. MEASUREMENTS: Using predetermined criteria, the incidence of gastric bleeding, gastric colonization, early-onset pneumonia, and late-onset pneumonia was assessed in patients intubated for more than 24 hours. RESULTS: Of 244 assessable patients, macroscopic gastric bleeding was observed in 10%, 4%, and 6% of patients assigned to receive sucralfate, antacid, and ranitidine, respectively (P > 0.2). The incidence of early-onset pneumonia was not statistically different among the three treatment groups (P > 0.2). Among the 213 patients observed for more than 4 days, late-onset pneumonia was observed in 5% of the patients who received sucralfate compared with 16% and 21% of the patients who received antacid or ranitidine, respectively (P = 0.022). Mortality was not statistically different among the three treatment groups. Patients who received sucralfate had a lower median gastric pH (P < 0.001) and less frequent gastric colonization compared with the other groups (P = 0.015). Using molecular typing, 84% of the patients with late-onset gram-negative bacillary pneumonia were found to have gastric colonization with the same bacteria before pneumonia developed. CONCLUSION: Stress ulcer prophylaxis with sucralfate reduces the risk for late-onset pneumonia in ventilated patients compared with antacid or ranitidine.

Continuous measurement of rat gastric blood flow using Doppler flowmeter.

We describe the use of pulsed Doppler flowmetry to permit continuous measurement of gastric blood flow in the anesthetized rat. The aims of this study were: 1) to assess the stability of blood flow during Doppler flowmetry; 2) to assess the ability of Doppler flowmetry to record rapid, transient blood flow changes; and 3) to validate Doppler flowmetry against an established blood flow measurement technique using labeled microspheres. Measurements over 3-h periods with a Doppler probe placed on the left gastric artery showed that there was an initial 30-min stabilization period; after this the mean percentage coefficient of variation, indicating intraindividual variability for blood flow, was < 10% for the remaining 150 min. The infusion of norepinephrine produced rapid, transient blood flow changes, including the typical "autoregulatory escape" and "postinfusion hyperemia," both of which were detected by Doppler flowmetry. The accuracy of pulsed Doppler flowmetry in measuring gastric blood flow was established by the demonstration of a highly significant agreement between blood flow measured by the Doppler flowmetry and microsphere techniques. These data indicate that pulsed Doppler flowmetry is an accurate method for the continuous measurement of left gastric artery blood flow in the rat.

The effect of continuous enteral nutrition on gastric acidity in humans.

The effect of continuous intraduodenal enteral nutrition on gastric pH was compared with the effects of fasting and of parenteral and standard nutrition control regimens containing equal amounts of carbohydrate, protein, and lipid. Eleven healthy volunteers underwent four 24-hour intragastric pH-metry studies; serum glucose, calcium, immunoreactive insulin and gastrin levels were determined during fasting and enteral and parenteral regimens. Median 24-hour gastric pH during enteral nutrition (group median pH 1.4) was lower than during parenteral nutrition (pH 1.9; P = 0.0039 vs. enteral) but was not different from fasting (pH 1.4) or standard nutrition (pH 1.6) values. Median 24-hour serum glucose levels during enteral nutrition (group median, 4.8 mmol/L) were higher than during fasting (4.0 mmol/L; P = 0.00098 vs. enteral) and lower than during parenteral nutrition (5.3 mmol/L; P = 0.0039 vs. enteral). Median 24-hour serum insulin levels during enteral nutrition (group median, 22.9 mU/L) were higher than during fasting (group median, 9.2 mU/L; P = 0.00098 vs. enteral) but similar to levels during parenteral nutrition (23.3 mU/L). Neither median 24-hour gastrin levels nor calcium levels were affected by any nutrition regimen. Thus, continuous enteral nutrition produces gastric pH values similar to those seen with fasting or standard nutrition, suggesting that, under most physiological conditions, gastric acidity is subject to close feedback control. Parenteral nutrition increases gastric pH, suggesting that systemic nutrients may influence this feedback mechanism.

Role of cholecystokinin in the regulation of gastric emptying and pancreatic enzyme secretion in humans. Studies with the cholecystokinin-receptor antagonist loxiglumide.

The role of cholecystokinin (CCK) in the regulation of gastric emptying and pancreatic enzyme secretion was evaluated by infusing the CCK-receptor antagonist loxiglumide. Gastric emptying rates and pancreatic secretory outputs were measured in five healthy volunteers by the double-indicator perfusion technique using a multiple-lumen tube in the duodenum. Placebo or loxiglumide (22 mumol.kg-1.h-1) was infused throughout each experiment. Five hundred-milliliter liquid intragastric meals of (a) fat, protein, and glucose (Ensure; Abbott, Chicago, IL); (b) glucose, 20 g/dL; and (c) guar gum, 1.1 g/dL, were given in random order. In addition, the effect of a physiologic CCK-8 dose (20 pmol.kg-1.h-1) after an intragastric 500-mL saline meal (0.154 mol/L) was tested. Intravenous CCK-8 induced a marked retardation of the gastric emptying rate of the saline solution (P less than 0.05) while stimulating pancreatic secretory outputs; both effects were completely abolished by the infusion of loxiglumide. Loxiglumide markedly accelerated the gastric emptying rates (by approximately 40%) and simultaneously diminished lipase (by approximately 75%) and trypsin (by approximately 50%) outputs of both the mixed meal (P less than 0.01) and the pure glucose meal (P less than 0.05). Additional experiments using gamma camera scintigraphy confirmed the accelerating effect of loxiglumide on gastric emptying of the mixed meal (P less than 0.01). The gastric emptying rate of the guar meal, which did not release CCK, was not influenced by the infusion of loxiglumide. Loxiglumide distinctly augmented plasma CCK levels after the mixed (2.6 times) and the pure glucose (2.1 times) meals while markedly reducing (approximately 76%) pancreatic polypeptide release (P less than 0.02). It is concluded that endogeneous CCK exerts a major role in the regulation of both gastric liquid emptying and pancreatic secretion in humans.

Luminal acid reduces gastric mucosal blood flow in the ischemic stomach.

Luminal gastric acid is essential for the formation of acute gastric mucosal lesions during ischemia. The mechanism by which luminal acid promotes gastric injury is, however, unclear. We investigated the effect of exogenous luminal acid on gastric mucosal blood flow using the radiolabeled microsphere technique. In rats with intact gastric blood supply application of exogenous luminal acid increased blood flow to the mucosa of the corpus and antrum. However, after ligation of the left gastric artery, which compromised mucosal blood flow to the corpus, application of luminal exogenous acid further decreased blood flow to the corpus. This indicates that the ability of the normal stomach to respond to luminal acidification with an increase in blood flow, which is thought to support clearance of back diffusing H+, is reversed in the ischemic stomach. The exposure to high luminal H+ concentrations may therefore promote gross injury in the ischemic stomach by further compromising nutritional mucosal blood flow.