Enrique Vallejo

Clinical utility of 99mTc-labeled ubiquicidin 29-41 antimicrobial peptide for the scintigraphic detection of mediastinitis after cardiac surgery.

BACKGROUND Previous studies demonstrated that (99m)Tc-labeled-ubiquicidin 29-41 ((99m)Tc-UBI 29-41) imaging is an accurate method for detection of bacterial infections. This study was conducted to evaluate the clinical use of (99m)Tc-UBI 29-41 for detection of mediastinitis after cardiac surgery. METHODS Thirteen patients with suspected mediastinitis after cardiac surgery were included. Qualitative and semiquantitative analyses of (99m)Tc-UBI 29-41 images were performed. Mediastinitis was confirmed by bacterial culture. RESULTS Qualitative analysis correctly identified the infection in 5/6 patients with mediastinitis. For observer 1, there were five true-positive results, six true-negative results, one false-positive result and one false-negative result (sensitivity: 83%, specificity: 85%, positive predictive value: 83%, negative predictive value: 85%, and overall diagnostic accuracy: 84%). For observer 2, there were five true-positive results, five true-negative results, two false-positive results and one false-negative result (sensitivity: 83%, specificity: 71%, positive predictive value: 71%, negative predictive value: 83%, and overall diagnostic accuracy: 76%). Agreement between observers was 0.847 (SE=0.145, p=0.002). Semiquantitative analysis showed a higher mediastinum uptake of the (99m)Tc-UBI 29-41 in patients with mediastinitis than that derived from patients without mediastinitis. Mean uptake of (99m)Tc-UBI 29-41 was 60.4+/-10.3 counts/pixel and 47.4+/-5.5 counts/pixel, respectively (p=0.01). At the threshold value of > or =57 counts/pixel using ROC analysis, the sensitivity, specificity, positive predictive value, negative predictive value and overall diagnostic accuracy for detecting patients with mediastinitis were 83, 100, 100, 87, and 92%, respectively (p=0.02; 95% CI: 0.65-1.10%). CONCLUSIONS (99m)Tc-UBI 29-41 imaging yielded fast and promising first results for patients with suspected mediastinitis after cardiac surgery and, as such, deserves further investigation.

Evaluation of Ventricular Synchrony with Equilibrium Radionuclide Angiography: Assessment of Variability and Accuracy

BACKGROUND AND AIMS Equilibrium radionuclide angiography (ERNA) has become an established method for assessing cardiac function. However, limited data are available to evaluate ventricular synchrony with ERNA. The aim of this study was to assess the variability and accuracy of ERNA to evaluate ventricular synchrony by means of phase images in healthy individuals and to compare them with a group of subjects with left bundle-branch block (interventricular dyssynchrony, LBBB) and with a group of patients with nonischemic, dilated cardiomyopathy (DCM) (inter- and intraventricular dyssynchrony). METHODS The population was divided into groups as follows: group 1 included 22 healthy subjects, group 2 included 11 patients with LBBB and normal left ventricular ejection fraction (LVEF), and group 3 included 14 DCM patients with LVEF <35% and LBBB. Interventricular synchrony was measured as the difference between LV mean phase angle (mPA) and RV mPA (LV-RV mPA). Intraventricular synchrony for each ventricle was measured as the standard deviation (SD) of the RV mPA and LA mPA blood pools. RESULTS Intra- and interobserver correlation coefficients were high for both inter- and intraventricular synchrony parameters. Area under the curve (AUC) was 0.98 for LV-RV mPA (p <0.001; 95% CI: 0.947-1.0). A cutoff value of 10 degrees yielded 96% sensitivity and 99% specificity to identify interventricular dyssynchrony. AUC was high for SD RV mPA and SD LV mPA (AUC = 1.0, p <0.001; 95% CI: 1.0-1.0 and AUC = 0.99, p <0.001; 95% CI: 0.979-1.0). A cutoff value of 22 degrees for SD LV mPA yielded 100% sensitivity and 100% specificity to identify LV intraventricular dyssynchrony. A cutoff value of 20 degrees for SD RV mPA yielded 100% sensitivity and 99% specificity to identify RV intraventricular dyssynchrony. CONCLUSIONS ERNA is an accurate and highly reproducible technique for evaluation of ventricular function and synchrony.

Factorial phase analysis of ventricular contraction using equilibrium radionuclide angiography images

Abstract Factorial phase analysis (FaPI) represents an alternative method to Fourier phase analysis (FoPI) in the evaluation and detection of abnormalities on cardiac contraction patterns, but it has limitations in representing the sequence in abnormal contraction patterns. In this work we propose a modified factorial phase image (FaPIm) that incorporates more complete information regarding the ventricular contraction sequence. In particular, we analyze and evaluate the contribution of the third eigenimage, in the presence of ventricular dyssynchrony, which has not been sufficiently explored in the literature. We have validated the proposed FaPIm using two Equilibrium Radionuclide Angiography (ERNA) sets of images obtained with a dynamic cardiac phantom and with a numerically simulated phantom. Also, we have tested the proposed representation for a control group of 23 normal subjects and for a sample of 15 patients with Complete Left Bundle Branch Block (LBBB). Whereas FoPI allows us to obtain an image that synthesizes ventricular contraction with the smallest dispersion around the mean values, FaPI and FaPIm show that external areas surrounding ventricular cavities present more dephasing than the rest of the ventricular region and contain more detailed information about the progression of contraction. Also, in the presence of an abnormal contraction pattern, the magnitude of the third eigenvalue was greater than the corresponding eigenvalue obtained for normal simulations. The dispersion plots obtained for a normal contraction pattern show that left ventricle (LV) and right ventricle (RV) information overlap. Therefore, when there is a dyssynchrony between LV and RV contraction it becomes necessary to incorporate the information corresponding to the third factor to achieve a clear separation between regions. In the comparison of the indices of control and LBBB populations, FaPIm shows significant differences in five out of six contraction indices, showing its promising value as a clinical tool.

Cardiopulmonary exercise testing in healthy children and adolescents at moderately high altitude

OBJECTIVE Cardiopulmonary exercise testing is a tool that helps clinicians to establish diagnosis and calculate risk stratification in adults. However, the utility of this test among children with congenital heart disease has not been fully explored. The goal of this study was to describe reference values for cardiopulmonary performance of healthy children. METHODS This study included 103 apparently healthy children (aged from 4 to 18 years; 61 boys), who underwent cardiopulmonary test using a treadmill protocol. All tests took place at 2240m above sea level (Mexico City). RESULTS Exercise time was 11±4min. There were no complications. Peak oxygen uptake correlated closely with height in both genders (girls r=0.84; boys r=0.84, p<0.001). A multivariable linear regression model showed that body surface area, exercise time, gender and heart rate reserve were significant predictors of peak oxygen uptake (R(2)=0.815, p<0.001). Peak oxygen uptake was strongly associated with age even among children younger than thirteen years (r=0.74, p<0.001). CONCLUSION This study provides physiological values for the major cardiopulmonary variables obtained from exercise testing using a treadmill among healthy children. Cardiopulmonary exercise test can be safely and effectively performed in young children even as young as 4 years old. Variables including age, gender and height are strongly associated with exercise time, peak heart rate and peak oxygen uptake. Regression equations for predicting peak heart rate and peak oxygen uptake are presented as reference values that allow researchers to compare children with heart disease versus those who are healthy.

Automated Classification of Severity in Cardiac Dyssynchrony Merging Clinical Data and Mechanical Descriptors

Cardiac resynchronization therapy (CRT) improves functional classification among patients with left ventricle malfunction and ventricular electric conduction disorders. However, a high percentage of subjects under CRT (20%–30%) do not show any improvement. Nonetheless the presence of mechanical contraction dyssynchrony in ventricles has been proposed as an indicator of CRT response. This work proposes an automated classification model of severity in ventricular contraction dyssynchrony. The model includes clinical data such as left ventricular ejection fraction (LVEF), QRS and P-R intervals, and the 3 most significant factors extracted from the factor analysis of dynamic structures applied to a set of equilibrium radionuclide angiography images representing the mechanical behavior of cardiac contraction. A control group of 33 normal volunteers (28 ± 5 years, LVEF of 59.7% ± 5.8%) and a HF group of 42 subjects (53.12 ± 15.05 years, LVEF < 35%) were studied. The proposed classifiers had hit rates of 90%, 50%, and 80% to distinguish between absent, mild, and moderate-severe interventricular dyssynchrony, respectively. For intraventricular dyssynchrony, hit rates of 100%, 50%, and 90% were observed distinguishing between absent, mild, and moderate-severe, respectively. These results seem promising in using this automated method for clinical follow-up of patients undergoing CRT.

Infective endocarditis detection through SPECT/CT images digital processing

Infective endocarditis (IE) is a difficult-to-diagnose pathology, since its manifestation in patients is highly variable. In this work, it was proposed a semiautomatic algorithm based on SPECT images digital processing for the detection of IE using a CT images volume as a spatial reference. The heart/lung rate was calculated using the SPECT images information. There were no statistically significant differences between the heart/lung rates values of a group of patients diagnosed with IE (2.62±0.47) and a group of healthy or control subjects (2.84±0.68). However, it is necessary to increase the study sample of both the individuals diagnosed with IE and the control group subjects, as well as to improve the images quality.

Normality Index of Ventricular Contraction Based on a Statistical Model from FADS

Radionuclide-based imaging is an alternative to evaluate ventricular function and synchrony and may be used as a tool for the identification of patients that could benefit from cardiac resynchronization therapy (CRT). In a previous work, we used Factor Analysis of Dynamic Structures (FADS) to analyze the contribution and spatial distribution of the 3 most significant factors (3-MSF) present in a dynamic series of equilibrium radionuclide angiography images. In this work, a probability density function model of the 3-MSF extracted from FADS for a control group is presented; also an index, based on the likelihood between the control groups contraction model and a sample of normal subjects is proposed. This normality index was compared with those computed for two cardiopathic populations, satisfying the clinical criteria to be considered as candidates for a CRT. The proposed normality index provides a measure, consistent with the phase analysis currently used in clinical environment, sensitive enough to show contraction differences between normal and abnormal groups, which suggests that it can be related to the degree of severity in the ventricular contraction dyssynchrony, and therefore shows promise as a follow-up procedure for patients under CRT.

Noninvasive coronary angiography using multislice computed tomography in a patient with Amplatzer occluder

Case history. A 68-year-old woman presented to our hospital complaining of chest discomfort. Five months earlier, she had a normal myocardial perfusion single photon emission computed tomography (SPECT) study before she was treated with an Amplatzer occluder (AGA Medical, Plymouth, Minn) for transcatheter closure of atrial septal defect (Figure 1). In the emergency department, the results of her physical examination, laboratory evaluation, electrocardiogram, and chest radiography were normal. A transthoracic echocardiogram showed normal ventricular function with a mild to moderate pericardial effusion. Nonsteroidal analgesics promptly relieved chest pain. The patient’s vital signs were stable, and the cardiologist decided to observe the patient closely in the hospital. On the next day, the patient complained of chest pain that radiated to the left arm, which disappeared with sublingual nitrates. The electrocardiogram showed T-wave inversion in the precordial leads. The patient underwent contrast-enhanced, electrocardiography-gated, multislice 16-row computed tomography (CT) (Gemini PET/CT; Philips Medical Systems, Andover, Mass) to exclude coronary artery disease (CAD) (Figures 1 and 2). Calcium scoring showed no coronary calcification, and subsequent multislice computed tomography (MSCT)–based angiography corroborated the pericardial effusion without any significant coronary artery stenosis. There were no technical limitations or any beam-hardening artifacts produced by the Amplatzer occluder (Figure 3). Subsequent intensive medical treatment led to significant improvement of the patient’s clinical condition. Discussion. SPECT myocardial perfusion imaging (MPI) is an established method for diagnosing CAD, with a reported sensitivity of 90%. In addition, MPI has been shown to be an excellent testing modality for risk stratification because the major determinants of prognosis in patients with CAD—the amount of myocardial scar, the extent and severity of inducible ischemia, and measurements of LV volumes and function—are already available from gated stress MPI. However, there is increasing understanding that in the setting of multivessel disease or in patients with small hearts, MPI might be less sensitive for detection of ischemia. More recently, MSCT has been introduced as a testing modality that allows a noninvasive assessment of coronary anatomy with a very high negative predictive value. Consequently, MSCT might serve as an adjunct to MPI in patients with equivocal MPI results or those patients in whom “balanced ischemia” is suspected. However, detection of coronary stenosis might be limited by high-attenuation structures, such as calcified coronary plaques, stents, surgical clips, pacemaker wires, or prosthetic valves, because they prevent adequate visualization of the surrounding structures or obscure the underlying coronary lumen, causing overestimation of the severity of the stenosis as a result of blooming and partial-volume effects. As shown in our patient, nitinol Amplatzer occlusion devices at the atrial level do not interfere with the evaluation of coronary arteries via MSCT. Furthermore, pericardial effusion was clearly evaluated with cardiac CT, which is an important advantage over SPECT MPI as a diagnostic tool for patients with chest pain presumably due to pericarditis.