Confinement effects on the shape and composition of bimetallic nano-objects in carbon nanotubes.

CoPt and FePt nanostructures have been efficiently confined in carbon nanotubes (CNTs). A marked confinement effect has been evidenced, both on bimetallic nano-object shape and composition. In large diameter CNTs small Co- and Fe-rich nanoparticles are formed, while in small diameter CNTs Pt-rich nanowires are selectively produced.

A transparent flexible z-axis sensitive multi-touch panel based on colloidal ITO nanocrystals.

Bottom-up fabrication of a flexible multi-touch panel prototype based on transparent colloidal indium tin oxide (ITO) nanocrystal (NC) films is presented. A series of 7% Sn(4+) doped ITO NCs protected by oleate, octanoate and butanoate ligands are synthesized and characterized by a battery of techniques including, high resolution transmission electron microscopy, X-ray diffraction, (1)H, (13)C and (119)Sn nuclear magnetic resonance spectroscopy, and the related diffusion ordered spectroscopy. Electrical resistivities of transparent films of these NCs assembled on flexible polyethylene terephthalate substrates by convective self-assembly from their suspension in toluene decrease with the ligand length, from 220 × 10(3) for oleate ITO to 13 × 10(3)Ω cm for butanoate ITO NC films. A highly transparent, flexible touch panel based on a matrix of strain gauges derived from the least resistive film of 17 nm butanoate ITO NCs sensitively detects the lateral position (x, y) of the touch as well as its intensity over the z-axis. Being compatible with a stylus or bare/gloved finger, a larger version of this module may be readily implemented in upcoming flexible screens, enabling navigation capabilities over all three axes, a feature highly desired by the display industry.

Tuning deposition of magnetic metallic nanoparticles from periodic pattern to thin film entrainment by dip coating method.

In this work, we report on the self-assembly of bimetallic CoFe carbide magnetic nanoparticles (MNPs) stabilized by a mixture of long chain surfactants. A dedicated setup, coupling dip coating and sputtering chamber, enables control of the self-assembly of MNPs from regular stripe to continuous thin films under inert atmosphere. The effects of experimental parameters, MNP concentration, withdrawal speed, amount, and nature of surfactants, as well as the surface state of the substrates are discussed. Magnetic measurements revealed that the assembled particles were not oxidized, confirming the high potentiality of our approach for the controlled deposition of highly sensitive MNPs.

Electron optical phase-shifts by Fourier methods: analytical versus numerical calculations.

The theoretical framework for the computation of electromagnetic fields and electron optical phase-shifts in Fourier space has been recently applied to objects with long-range fringing fields, such as reverse-biased p-n junctions and magnetic stripe domains near a specimen edge. In addition to new analytical results, in this work, we present a critical comparison between numerical and analytical computations. The influence of explicit and implicit boundary conditions on the phase shifts and phase-contrast images is also investigated in detail.

Electron microscope calibration for the Lorentz mode.

The calibration of a modern electron microscope for Lorentz microscopy observations has been performed using diffractogram, Fresnel diffraction fringe analysis and low-angle electron diffraction methods. An example related to the observations of electrostatic fields associated to a thinned reverse-biased p-n junction is also reported.

A Fourier approach to fields and electron optical phase-shifts calculations.

The Fourier method is applied to calculate fields and electron optical phase shifts in specimens having long-range electromagnetic fields, like reverse biased p-n junctions or stripe magnetic domains. It is shown that this approach not only allows to take into account rather easily the effect of the fringing fields protruding in the space around the specimen, but also to obtain solutions to interesting models in analytical form.

A randomized study of intravenous magnesium in acute myocardial infarction treated with direct coronary angioplasty.

BACKGROUND: Notwithstanding the negative result of the International Study of Infarct Survival-4 (ISIS-4), the controversy about the role of magnesium in acute myocardial infarction is still open because, according to experimental data, magnesium could decrease myocardial damage and mortality only if infusion is started before reperfusion. This randomized placebo-controlled trial was designed to evaluate the effect of intravenous magnesium, delivered before, during, and after direct coronary angioplasty, in patients with acute myocardial infarction. METHODS: One-hundred fifty patients were randomized to intravenous magnesium sulfate or placebo. The primary end point was an infarct zone wall motion score index at 30 days, as a measure of infarct size. The secondary end points included creatine kinase peak, ventricular fibrillation/tachycardia within the first 24 hours, death and congestive heart failure within the 30-day follow-up, and 30-day left ventricular ejection fraction. Analysis was by intention to treat. RESULTS: There were no significant differences between the magnesium and placebo groups in the 30-day infarct zone wall motion score index (1.93 +/- 0.61 vs 1.85 +/- 0.51, P =.39), ventricular arrhythmias (24% vs 15%, P =.15), death (0 vs 1%, P =.32), heart failure (8% vs 7%, P =.75), and 30-day left ventricular ejection fraction (49% +/- 11% vs 50% +/- 9%, P = 0.55). There was a trend toward a higher creatine kinase peak in the magnesium group (3059 +/- 2359 vs 2404 +/- 1673,P =.052). CONCLUSIONS: Intravenous magnesium delivered before, during, and after reperfusion did not decrease myocardial damage and did not improve the short-term clinical outcome in patients with acute myocardial infarction treated with direct angioplasty.

Early dobutamine echocardiography predicts improvement in regional and global left ventricular function after reperfused acute myocardial infarction without residual stenosis of the infarct-related artery.

BACKGROUND: The accuracy of dobutamine echocardiography (DE) early after reperfused acute myocardial infarction (AMI) without residual stenosis of the infarct-related artery is unknown. The objective of this study was to assess whether in reperfused AMI DE can predict early as well as late regional and global spontaneous functional recovery. METHODS: DE was performed in 157 patients (61 +/- 11 years; 33 women) 3 days after AMI treated with successful direct percutaneous transluminal coronary angioplasty (Thrombolysis in Myocardial Infarction flow grade 3, residual stenosis <30%). All patients underwent 2-dimensional echocardiography and coronary angiography at 1 month and 145 (92%) at 6 months. RESULTS: Patency and restenosis rate were similar between those who did and did not respond to DE. DE showed a high accuracy in predicting both early and late regional functional recovery (86% and 81%, respectively). DE accuracy in predicting early and late reversible dysfunction was also high on a patient-by-patient analysis (89% and 87%). In DE responders left ventricular ejection fraction increased from 44% +/- 9% at baseline to 57% +/- 9% at 6 months (P <.00005), whereas only a slight, although significant improvement was found in nonresponders (from 40% +/- 10% to 44% +/- 12%; P =.03). A significant correlation was found between the number of dobutamine-responder segments and the magnitude of their functional improvement at peak dobutamine and changes in ejection fraction (r =.72; P <.000001; r =.68, P <.000001, respectively). CONCLUSIONS: These data indicate that in patients with AMI in whom anterograde flow is fully restored without residual stenosis, DE can predict the recovery of regional function and whether a relevant change in ejection fraction will occur at early and late follow-up.

Efficacy of a "stent-like" PTCA strategy in current clinical practice.

Retrospective analysis within the BENESTENT-l trial has shown that patients having a "stent-like" result after standard PTCA had angiographic and clinical outcomes similar to those of patients receiving a stent. The objective of this study is to assess the efficacy of a "stent-like" PTCA strategy in native coronary arteries in non-selected patients. From our data base, 503 consecutive patients who underwent successful PTCA or stent supported PTCA were stratified according to a target lesion length < 15 mm, a reference vessel diameter > or = 2.5 mm, and a postprocedural residual stenosis < 30%. After stratification, 132 patients with "stent-like" PTCA, and 88 with single stent implantation were compared on two-year clinical outcomes. Two-year event-free survival rate was 70% in the "stent-like" PTCA group, and 83% in the stent group (p = 0.022). Stent-like PTCA is associated with a higher restenosis rate and higher adverse events rate as compared to single stent supported PTCA, whatever the indication for stenting.

Systematic primary angioplasty in octogenarian and older patients.

BACKGROUND: There are conflicting data about the efficacy of aggressive treatment and early intervention among high-risk patients with acute myocardial infarction (AMI), such as elderly patients. This study sought to determine the short- and long-term outcome of octogenarian and older patients after primary percutaneous transluminal coronary angioplasty (PTCA). METHODS: In our tertiary referral center a program of primary PTCA was begun in 1995, and the systematic care for AMI included primary PTCA in all patients with AMI, with no age restriction. Over a period of 3 years, 55 octogenarian or older patients underwent primary PTCA. RESULTS: Between January 1995 and July 1998, 719 patients with AMI underwent primary PTCA. Of these, 55 patients were octogenarians or older (mean age, 84 +/- 3 years). Primary PTCA failure occurred in 3 (5%) patients. An optimal acute angiographic result was achieved in 51 (93%) patients. Stenting of the infarct vessel was accomplished in 33 (60%) patients. The 30-day mortality rate was 16%. The mortality rate was 4% in patients without cardiogenic shock on presentation and 70% in patients with cardiogenic shock. The recurrent ischemia rate was 13% and resulted in nonfatal reinfarction in 2 patients and repeat PTCA in 5 patients. As determined by multivariate analysis, an optimal acute angiographic result and cardiogenic shock were significantly related to mortality. The 1-year survival rate was 77%. CONCLUSIONS: The results of this study suggest that the benefits of primary PTCA apply to the very elderly and support an early aggressive strategy for this high-risk patient subset.

Primary coronary infarct artery stenting in acute myocardial infarction.

Completed and ongoing randomized trials have provided results that favor primary infarct-related artery (IRA) stenting as opposed to primary percutaneous transluminal coronary angioplasty, but the applicability of the trial results to all patients with acute myocardial infarction (AMI) has not yet been investigated. This study sought to determine the applicability of an unconditional IRA stenting strategy in nonselected patients with AMI. After successful mechanical recanalization of the IRA, all patients with AMI and a reference diameter > or =2.5 mm were considered eligible for primary IRA stenting without any restriction regarding age or clinical status on presentation. The primary end point of the study was a composite end point defined as death, reinfarction, or repeat target lesion revascularization. Primary IRA stenting was successfully performed in 161 of 190 consecutive patients with AMI (85%), and of 162 (99%) considered suitable for stenting. Patients with nonstented IRA had a reference IRA diameter smaller than patients with a stent (2.71+/-0.48 vs 3.20+/-0.41 mm, p <0.001). Overall, the 6-month mortality was 5%. Mortality was 2% for patients without, and 32% for patients with cardiogenic shock. The incidences of reinfarction and of repeat target lesion revascularization were 1% and 12%, respectively. The 6-month angiographic follow-up showed an IRA patency rate of 94% and a restenosis rate of 26%. The results of this study strengthen the hypothesis that unconditional primary IRA stenting is highly feasible, and may actually improve the outcome of patients with AMI.

Detecting myocardial salvage after primary PTCA: early myocardial contrast echocardiography versus delayed sestamibi perfusion imaging.

UNLABELLED: The extent of myocardial salvage after primary percutaneous transluminal coronary angioplasty (PTCA) in acute myocardial infarction (AMI) is variable and cannot be predicted on the basis of either vessel patency or early regional wall motion assessment. The aim of this study was to evaluate the reliability of microvascular integrity, as shown by myocardial contrast echocardiography (MCE), as an indicator of tissue salvage and a predictor of late functional recovery, and to compare MCE with the quantification of tracer activity in sestamibi perfusion imaging. METHODS: Twenty-six patients with AMI who received successful treatment with primary PTCA were examined with MCE during cardiac catheterization immediately before and after vessel recanalization. Myocardial contrast effect was scored as 0 (absent), 0.5 (partial) or 1 (normal). Wall motion was assessed by two-dimensional echocardiography on admission and 1 mo later with a 16-segment model and 4-point score. Resting sestamibi SPECT was collected within 1 wk after AMI. The risk area was defined by MCE as the sum of the segments with no perfusion (score 0) before PTCA. Myocardial viability was defined by MCE as an increase in contrast score in the same segments after PTCA and by sestamibi SPECT as a preserved tracer activity (>60% of peak activity). The functional recovery after 1 mo detected by two-dimensional echocardiography was the reference standard for viability. RESULTS: A total of 50 segments showed perfusion defects before PTCA (risk area). Immediately after PTCA, the MCE score increased in 44 of 50 segments, whereas sestamibi SPECT showed preserved activity in 22 of 50 segments. After 1 mo, the wall motion score decreased in 22 of 50 segments (viable segments) and was unchanged in the remaining 28 segments. Thus, MCE showed a sensitivity of 91% and a specificity of 14% in detecting viable myocardium, whereas sestamibi SPECT showed a lower sensitivity (68%) but a significantly higher specificity (75%; P < 0.00001). The positive predictive values were 45% and 68% for MCE and SPECT (P < 0.005), respectively, and the negative predictive values were 67% and 71%, respectively. On a patient basis, SPECT was more specific (79% versus 21%; P < 0.01) and showed a higher overall predictive accuracy (88% versus 50%; P < 0.01) than MCE. CONCLUSION: The demonstration of microvascular integrity by MCE performed immediately after primary PTCA has a limited diagnostic value in predicting salvaged myocardium. Conversely, tracer activity quantification in resting sestamibi SPECT performed in a later stage is confirmed to be a reliable approach for recognizing myocardial stunning and predicting functional recovery.

Doppler-derived mitral deceleration time: an early strong predictor of left ventricular remodeling after reperfused anterior acute myocardial infarction.

BACKGROUND: The relation between remodeling and left ventricular (LV) diastolic function has not yet been fully investigated. The aim of this study was to determine whether early assessment of Doppler-derived mitral deceleration time (DT), a measure of LV compliance and filling, may predict progressive LV dilation after acute myocardial infarction (AMI). METHODS AND RESULTS: Fifty-one patients (aged 61+/-11 years; 6 women) with anterior AMI successfully treated with direct coronary angioplasty underwent 2-dimensional and Doppler echocardiographic examinations within 24 hours of admission, at days 3, 7, and 30 and 6 months after the index infarction. Mitral flow velocities were obtained from the apical 4-chamber view with pulsed Doppler. End-diastolic volume index (EDVI) and end-systolic volume index (ESVI) were calculated with the Simpson's rule algorithm. Patients were divided according to the DT duration assessed at day 3 in 2 groups: group 1 (n=33) with DT >130 ms and group 2 (n=18) with DT

[Systematic treatment of acute myocardial infarction with primary angioplasty. Early clinical and angiographic results and after 6 months]. / Trattamento sistematico dell'infarto miocardico acuto con angioplastica primaria. Risultati clinici ed angiografici precoci e a sei mesi.

UNLABELLED: Starting in 1995, at our institution all patients with acute myocardial infarction (AMI) who gave informed consent were treated by primary percutaneous transluminal coronary angioplasty (PTCA) without limitations in entry criteria. This report presents early and six-month clinical and angiographic results of the 720 patients (77% male, median age 64 years) treated by direct PTCA between January 1, 1995 and July 31, 1998. On admission, 33% of patients were in Killip class > 1, and 101 patients (14%) were in early cardiogenic shock. Optimal acute angiographic success (TIMI grade 3 flow with residual stenosis < 30%) was achieved in 683 patients (95%). Primary or unplanned stenting of infarct related artery (IRA) for a suboptimal or poor angiographic result after primary PTCA was performed in 454 patients (63%). The mean time from hospital arrival to recanalization was 62 +/- 28 min. At 30 days, the mortality rate was 4.9% (1.8% in Killip class < 4 patients and 24% in patients with cardiogenic shock). The reinfarction rate was 1.2%. At 30 days, coronary angiography showed restenosis or reocclusion of the IRA in 55 patients (8.9%). During the six-month follow-up (30-180 days), there were 11 deaths (1.5%) and 2 non-fatal reinfarctions (0.3%). At six months, the IRA patency rate was 95%, while the mean ejection fraction improvement in 422 patients with paired ventriculograms was 7%. Recurrent ischemia occurred in 144 patients (20%) and resulted in 7 deaths, 11 non-fatal reinfarctions and 126 repeat targeted vessel revascularization. CONCLUSIONS: The major finding of our experience is that direct coronary angioplasty may result in excellent early and late outcome in a population without limitations in entry criteria. The low mortality and the few recurrent myocardial ischemic events are connected with the high patency rate at 6 months. The extensive use of stents improves the angiographic results and the clinical outcome.

Relation between ST-segment changes and myocardial perfusion evaluated by myocardial contrast echocardiography in patients with acute myocardial infarction treated with direct angioplasty.

The aim of this study was to evaluate the relation between myocardial perfusion and ST-segment changes in patients with acute myocardial infarction treated with successful direct angioplasty. Thirty-seven patients, successfully treated with direct angioplasty, underwent myocardial contrast echocardiography before and after angioplasty. The sum of ST-segment elevation divided by the number of the leads involved (ST-segment elevation index) was calculated at 1, 5, 10, 20, and 30 minutes after restoration of a Thrombolysis In Myocardial Infarction trial grade 3 flow. After recanalization, myocardial reperfusion within the risk area was observed in 26 patients, whereas a no-reflow phenomenon occurred in 11. In patients with myocardial reperfusion, the ST-segment elevation index progressively declined, whereas in patients with no reflow, no significant change was observed. Reduction of > or = 50% in the ST-segment elevation index occurred in 20 of the 26 patients with reflow and in 1 of the 11 with no reflow (p = 0.0002). An additional increase of > or = 30% in the ST-segment elevation index occurred in 3 patients with reflow and in 7 with no reflow (p = 0.003). Sensitivity, specificity, positive and negative predictive values, and accuracy of the reduction in the ST-segment elevation index for predicting microvascular reflow were 77%, 91%, 95%, 62%, and 81%, respectively. The corresponding values of the increase in ST-segment elevation index for predicting no reflow were 64%, 88%, 70%, 85%, and 81%, respectively. In conclusion, after successful angioplasty, different patterns of myocardial perfusion are associated with different ST-segment changes. Analysis of ST-segment changes predicts the degree of myocardial reperfusion.

[Rapid resolution of ST-segment elevation predicts functional recovery in acute myocardial infarction treated with primary percutaneous transluminal coronary angioplasty]. / La rapida riduzione del sovraslivellamento del tratto ST è predittiva del recupero della funzione nell'infarto miocardico acuto trattato con angioplastica coronarcia primaria.

OBJECTIVES: This study was designed to prospectively assess the ability of the 12-lead electrocardiogram (ECG) and optimal ECG criteria to predict late functional recovery in patients with acute myocardial infarction (AMI) treated with primary coronary angioplasty (PTCA) BACKGROUND: A simple clinical method to predict clinical outcome in patients with reperfused AMI is highly desirable from a clinical point of view. METHODS: Seventy-five patients with AMI treated with successful PTCA (TIMI flow grade 3 and residual stenosis < 30%) underwent serial 12-lead ECG before PTCA and every hour for the first 6 hours and then at 9, 12, and 18 hours after PTCA. All patients underwent two-dimensional echocardiography before PTCA and 1 and 6 months later for the evaluation of regional wall motion. The ST segment level in the lead exhibiting the maximal ST elevation (ST increase max) and the sum of the ST segment elevation (sigma ST increases) were calculated on initial ECG and a cut-off values of > or = 50% reduction of ST increases max sigma ST increases elevation and sampling intervals were correlated with late functional recovery. A wall motion score index (WMSI: 1 = normal to 4 = dyskinesia) and 16-segment model were used. Reversible dysfunction was defined as a decrease of > or = 0.22 in WMSI. RESULTS: At univariate analysis a > or = 50% reduction of both ST increases max and sigma ST increases was related to late functional recovery. Multiple logistic regression analysis revealed that reduction of sigma ST increases was the most powerful predictor of late functional recovery (p = 0.008). A > or = 50% reduction of sigma ST increase within 4 hours of PTCA provided the optimal criterion for predicting late functional recovery. CONCLUSIONS: Rapid reduction of sigma ST increases elevation is an accurate predictor of left ventricular functional recovery in patients with AMI treated with primary PTCA. Optimal criteria include a reduction in sigma ST increases elevation > or = 50% within 4 hours of PTCA.

Prediction of post-revascularization functional recovery of asynergic myocardium using quantitative thallium-201 rest-redistribution tomography: has the reverse redistribution pattern an independent significance?

The significance of reverse redistribution on rest-redistribution thallium-201 myocardial scintigraphy is unclear. Previous studies suggested that reverse redistribution segments with normal resting activity include viable myocardium, whilst resting defects with further worsening correspond to scar. We evaluated whether reverse redistribution has an independent significance for the prediction of post-revascularization recovery, particularly as compared with the quantification of redistribution activity. We studied 26 coronary artery disease patients with left ventricular dysfunction, who underwent 201Tl rest-redistribution single-photon emission tomography (SPET) and echocardiography before revascularization. Viability was defined by the detection of wall motion improvement on follow-up echocardiography. 201Tl activity was considered normal if >/=80%, moderately reduced if <80% but >/=50%, and severely decreased if <50%. Reverse redistribution was defined as a defect in redistribution images with >/=10% decrease in relative 201Tl activity compared with the resting value. Reverse redistribution was detected in 33 segments (10%). Baseline dysfunction was equally observed in the reverse redistribution and in the non-reverse redistribution segments (64% vs 56%, P=0.40) and the rate of asynergic segments with post-revascularization recovery was not different between the two groups (33% vs 54%, P=0.11). The rate of functional recovery in redistribution defects without reverse redistribution was 53% in moderate and 30% in severe defects; the corresponding values for the reverse redistribution segments were 50% and 27% (all non-significant versus non-reverse redistribution segments). For the prediction of post-revascularization recovery in asynergic segments, the detection of reverse redistribution on rest-redistribution 201Tl SPET does not add any information to the quantitative analysis of redistribution activity.

A clinical trial comparing primary stenting of the infarct-related artery with optimal primary angioplasty for acute myocardial infarction: results from the Florence Randomized Elective Stenting in Acute Coronary Occlusions (FRESCO) trial.

OBJECTIVES: This study sought to compare stenting of the primary infarct-related artery (IRA) with optimal primary percutaneous transluminal coronary angioplasty (PTCA) with respect to clinical and angiographic outcomes of patients with an acute myocardial infarction. BACKGROUND: Early and late restenosis or reocclusion of the IRA after successful primary PTCA significantly contributes to increased patient morbidity and mortality. Coronary stenting results in a lower rate of angiographic and clinical restenosis than standard PTCA in patients with angina and with previously untreated, noncomplex lesions. METHODS: After successful primary PTCA, 150 patients were randomly assigned to elective stenting or no further intervention. The primary end point of the trial was a composite end point, defined as death, reinfarction or repeat target vessel revascularization as a consequence of recurrent ischemia within 6 months of randomization. The secondary end point was angiographic evidence of restenosis or reocclusion at 6 months after randomization. RESULTS: Stenting of the IRA was successful in all patients randomized to stent treatment. At 6 months, the incidence of the primary end point was 9% in the stent group and 28% in the PTCA group (p=0.003); the incidence of restenosis or reocclusion was 17% in the stent group and 43% in the PTCA group (p=0.001). CONCLUSIONS: Primary stenting of the IRA, compared with optimal primary angioplasty, results in a lower rate of major adverse events related to recurrent ischemia and a lower rate of angiographically detected restenosis or reocclusion of the IRA.

Rest-redistribution thallium-201 SPECT to detect myocardial viability.

UNLABELLED: Rest-redistribution 201Tl imaging is currently being used for myocardial viability detection, but the ideal parameters for territory classification have not yet been defined. The aim of this study was to define the optimal criteria for detecting viable myocardium and predicting postrevascularization recovery with rest-redistribution 201Tl SPECT. METHODS: In 29 patients with left ventricular dysfunction, tracer activity within asynergic segments was quantified on rest and redistribution 201Tl SPECT. Viability was defined by the presence of functional recovery, which was detected by comparing wall motion in baseline and follow-up echocardiography. Discriminant function analysis and receiver operating characteristic (ROC) curve analysis were used to evaluate the relationship between 201Tl data and viability. RESULTS: Of 214 dysfunctioning segments (135 a-/dyskinetic), viability was demonstrated in 115 (75 a-/dyskinetic). Both rest and redistribution 201Tl activity in these segments were significantly higher than they were in the nonviable segments (p < 0.0001). Significant (> 10%) reversibility was observed in 39% of the viable and in 36% of the nonviable segments (p = 0.81). Discriminant analysis identified redistribution activity, followed by rest activity, as the most effective predictors of functional recovery. Similar areas were found under the ROC curve for rest (0.68 +/- 0.037) and for redistribution activity (0.70 +/- 0.036) (p = 0.13). ROC curve analysis identified the optimal cutoff for redistribution activity at < 60%, with 147 of 214 (69%) segments correctly classified (sensitivity = 78% and specificity = 58%). In the subset of a-/dyskinetic segments, redistribution activity presented a significantly larger ROC curve area (0.81 +/- 0.038 compared to 0.77 +/- 0.042, p < 0.05), and 103 of 135 (76%) segments were correctly classified (sensitivity = 81% and specificity = 70%). CONCLUSION: Redistribution activity is the most important parameter to be considered in rest-redistribution 201Tl to differentiate viable from nonviable segments; rest activity is also valuable, whereas the meaning of reversibility appears limited. Cutoff values about 60% appear to give the most reasonable balance between sensitivity and specificity.