The value of local normal limits in quantitative Thallium-201 CZT MPI SPECT.

BACKGROUND: Considering the distinctive characteristics of CZT detectors, automatic quantification of ischemia using normal limits included with software package may deliver suboptimal results for CAD detection. The present study aims to evaluate the benefits of creating normal limits specific to a local population and laboratory protocol. METHODS AND RESULTS: Two groups were selected from patients who had undergone a CZT MPI. Normal limits were generated with the QPS application based on the population with low likelihood of CAD. Using the vendor-supplied and the population-specific normal limits i-TPD and vessel-specific SDS results obtained for patients who had subsequently undergone coronary angiography were compared with coronary angiography data. A weak correlation was observed for low i-TPD (stress TPD minus rest TPD) and SDS values. Both databases gave similar values for the area under the ROC curve concerning i-TPD (0.75 to 0.74) and SDS results (0.72 to 0.75 for the LAD, 0.62 to 0.64 for the LCx, and 0.63 to 0.67 for the RCA). Sensitivity (60%), specificity (78%), and predictive positive (84%) and negative (52%) values were also similar with a diagnostic and prognostic threshold value. CONCLUSION: The use of a population-specific created database did not influence the diagnostic value of thallium-201 MPI QPS results using a CZT camera.

Scintigraphic spectrum of a patient population with suspected arrhythmogenic right ventricular dysplasia.

Gated radionuclide ventriculography (RNV), combined with inter- and intraventricular dyssynchrony measurement by phase analysis, is able to evidence right and left ventricular mechanical cardiac disorders and may contribute to the diagnosis of arrhythmogenic right ventricular dysplasia (ARVD). Nevertheless, the patients referred for suspicion of ARVD on the basis of symptoms, electrical abnormalities or family history of sudden death, are very heterogeneous and the examination findings spread out from strictly normal to severely abnormal. In order to describe the patient population encountered in "real life" we propose to use an automatic clustering method based on RNV results in order to segment the overall population into subgroups with coherent scintigraphic data in each one. A series of 130 consecutive patients presenting with various criteria suggestive of ARVD has been studied over a 3-year period. Seven variables have been extracted from gated RNV: left and right ejection fractions, visual semi-quantitative assessment of left and right ventricular volumes, left and right phase standard deviations and inter-ventricular dyssynchrony (IVD) measured from the phase histograms. The Self Organizing Map (SOM) clustering method has been applied to these data with various numbers of variables (right ventricular values only or values from both ventricles) and an increasing number of classes from two to nine. Including left ventricular variables and IVD in the analysis results in significant changes in classification compared to right ventricular data alone. Clustering into nine classes seems to be the most pertinent one and separates patients into four groups of normal result or insignificant left, right or bilateral abnormalities, two groups of isolated right ventricular abnormalities of increasing severity and three groups of severe bilateral abnormalities, right predominant with and without IVD, and left predominant. Automatic clustering of patients on the basis of scintigraphic results helps to understand the signification of the large spectrum of results encountered in clinical practice for patients whose common characteristic is to present some abnormalities or risk factors leading to investigations in the context of suspicion of ARVD. Although the final diagnosis remains questionable in a large proportion of patients, the knowledge of the various profiles of gated blood pool phase analysis may help for stratification of patients at risk of ARVD.

Quantification of ventricular resynchronization reserve by radionuclide phase analysis in heart failure patients: a prospective long-term study.

BACKGROUND: Phase analysis, developed to assess dyssynchrony from ECG-gated radionuclide ventriculography, has shown promising results. We hypothesized that quantifying the cardiac resynchronization reserve, that is, the extent of response to cardiac resynchronization therapy (CRT), by radionuclide imaging could potentially identify patients who are best suited for CRT. METHODS AND RESULTS: Seventy-four patients ages 64.8±10.1 years were prospectively studied from July 2004 to July 2006, of whom 62.2% and 37.8%, respectively, were in New York Heart Association class 3 and 4. Mean QRS width was 173±25 ms. ECG-gated radionuclide ventriculography to quantify interventricular and intraventricular dyssynchrony was performed at baseline with and without CRT and at the 3-month follow-up visit. Amino-terminal-pro-brain natriuretic peptide (NT-pro-BNP) levels were also determined at baseline and at 3 months. During a mean follow-up of 10.1±7.6 months, there were 37 (50%) clinical events that defined the nonresponder group, including cardiac death or readmission for worsening heart failure. In multivariate Cox model analysis, higher NT-pro-BNP blood levels were associated with a significant increase in the risk for event (hazard ratio=1.085 for a 100 pg/L increase in NT-pro-BNP; 95% confidence interval, 1.014 to 1.161). Each 10° elevation in intraventricular dyssynchrony was associated with a decrease in the risk of events (hazard ratio=0.456, 95% confidence interval, 0.304 to 0.683). Receiver operating characteristic curve analysis demonstrated that an interventricular dyssynchrony cutoff value of 25.5° for intraventricular synchrony yielded 91.4% sensitivity and 84.4% specificity for predicting a good response to CRT. CONCLUSIONS: The quantification of interventricular dyssynchrony with radionuclide phase analysis suggests that early postimplantation interventricular dyssynchrony may provide identification of CRT responders.

Long-term benefit of postconditioning.

BACKGROUND: We previously demonstrated that ischemic postconditioning decreases creatine kinase release, a surrogate marker for infarct size, in patients with acute myocardial infarction. Our objective was to determine whether ischemic postconditioning could afford (1) a persistent infarct size limitation and (2) an improved recovery of myocardial contractile function several months after infarction. METHODS AND RESULTS: Patients presenting within 6 hours of the onset of chest pain, with suspicion for a first ST-segment-elevation myocardial infarction, and for whom the clinical decision was made to treat with percutaneous coronary intervention, were eligible for enrollment. After reperfusion by direct stenting, 38 patients were randomly assigned to a control (no intervention; n=21) or postconditioned group (repeated inflation and deflation of the angioplasty balloon; n=17). Infarct size was assessed both by cardiac enzyme release during early reperfusion and by 201thallium single photon emission computed tomography at 6 months after acute myocardial infarction. At 1 year, global and regional contractile function was evaluated by echocardiography. At 6 months after acute myocardial infarction, single photon emission computed tomography rest-redistribution index (a surrogate for infarct size) averaged 11.8+/-10.3% versus 19.5+/-13.3% in the postconditioned versus control group (P=0.04), in agreement with the significant reduction in creatine kinase and troponin I release observed in the postconditioned versus control group (-40% and -47%, respectively). At 1 year, the postconditioned group exhibited a 7% increase in left ventricular ejection fraction compared with control (P=0.04). CONCLUSIONS: Postconditioning affords persistent infarct size reduction and improves long-term functional recovery in patients with acute myocardial infarction.