Positron Emission Tomography Viability Research Articles

Impact of Positron Emission Tomography Viability Imaging: Guided Revascularizations on Clinical Outcomes in Patients With Myocardial Scar on Single-Photon Emission Computed Tomography Scans.

Positron emission tomography (PET) viability scan is used to determine whether patients with a myocardial scar on single-photon emission computed tomography (SPECT) may need revascularization. However, the clinical utility of revascularization decision-making guided by PET viability imaging has not been proven yet. The purpose of this study was to investigate the impact of PET to determine revascularization on clinical outcomes. Between September 2012 and May 2021, 53 patients (37 males; mean age = 64 ± 11 years) with a myocardial scar on MIBI SPECT who underwent PET viability test were analyzed in this study. The primary outcome was a temporal change in echocardiographic findings. The secondary outcome was all-cause mortality. Viable myocardium was presented by PET imaging in 29 (54.7%) patients. Revascularization was performed in 26 (49.1%) patients, including 18 (34.0%) with percutaneous coronary intervention (PCI) and 8 (15.1%) with coronary artery bypass grafting. There were significant improvements in echocardiographic findings in the revascularization group and the viable myocardium group. All-cause mortality was significantly lower in the revascularization group than in the medical therapy-alone group (19.2% vs. 44.4%, log-rank P = 0.002) irrespective of viable (21.4% vs. 46.7%, log-rank P = 0.025) or non-viable myocardium (16.7% vs. 41.7%, log-rank P = 0.046). All-cause mortality was significantly lower in the PCI group than in the medical therapy-alone group (11.1% vs. 44.4%, log-rank P < 0.001). Revascularization improved left ventricular systolic function and survival of patients with a myocardial scar on SPECT scans, irrespective of myocardial viability on PET scans.

Clinical use of cardiac 18F-FDG viability PET: a retrospective study of 44 patients undergoing post-test revascularization.

The coupling between coronary artery disease and the development of ischemic heart failure is well-established. For these patients, assessment of potentially viable but dysfunctional myocardial tissue (hibernation) is considered critical to guide optimal surgical treatment. Assessment with positron emission tomography (PET) theoretically provides measurements of hibernating tissue and maximal myocardial glucose uptake (MGU) in all cardiac territories. However, the clinical benefits of these measures are not thoroughly studied. We therefore aimed to investigate whether cardiac viability testing with combined Rubidium-82 (82Rb) and 18F-fluorodeoxyglucose (18F-FDG) predicts post-intervention improvement in left ventricle ejection fraction (LVEF) and survival. This retrospective study consisted of 131 patients with ischemic heart failure referred for dynamic 82Rb/18F-FDG PET viability testing prior to revascularization. The FDG viability scan was done during a hyperinsulinemic-euglycemic clamp and included PET measures static FDG hibernation and absolute MGU as well as myocardial blood flow and coronary flow reserve. In total, 44/131 patients undergoing viability testing were subsequently revascularized. Following revascularization, 26 patients had LVEF improvement of at least 5% while 18 patients had no improvement. A poor correlation between areas of intervention and areas of hibernation was observed. Receiver operating characteristics for all PET metrics did not predict improvement in LVEF. Furthermore, hibernation failed to predict survival regardless of whether patients underwent subsequent revascularization. Dynamic viability PET metrics (hibernation and MGU) do not predict post-intervention improvement in LVEF or overall survival in ischemic heart failure patients undergoing revascularization. In a clinical setting, the value of these measurements may therefore be limited. Kindly check and confirm the Given names and Family names for all the authors.All names are correct!

Manganese-enhanced T1 mapping to quantify myocardial viability: validation with 18F-fluorodeoxyglucose positron emission tomography

Gadolinium chelates are widely used in cardiovascular magnetic resonance imaging (MRI) as passive intravascular and extracellular space markers. Manganese, a biologically active paramagnetic calcium analogue, provides novel intracellular myocardial tissue characterisation. We previously showed manganese-enhanced MRI (MEMRI) more accurately quantifies myocardial infarction than gadolinium delayed-enhancement MRI (DEMRI). Here, we evaluated the potential of MEMRI to assess myocardial viability compared to gold-standard 18F-fluorodeoxyglucose (18F-FDG) positron emission tomography (PET) viability. Coronary artery ligation surgery was performed in male Sprague-Dawley rats (n = 13) followed by dual MEMRI and 18F-FDG PET imaging at 10–12 weeks. MEMRI was achieved with unchelated (EVP1001-1) or chelated (mangafodipir) manganese. T1 mapping MRI was followed by 18F-FDG micro-PET, with tissue taken for histological correlation. MEMRI and PET demonstrated good agreement with histology but native T1 underestimated infarct size. Quantification of viability by MEMRI, PET and MTC were similar, irrespective of manganese agent. MEMRI showed superior agreement with PET than native T1. MEMRI showed excellent agreement with PET and MTC viability. Myocardial MEMRI T1 correlated with 18F-FDG standard uptake values and influx constant but not native T1. Our findings indicate that MEMRI identifies and quantifies myocardial viability and has major potential for clinical application in myocardial disease and regenerative therapies.

Status of F-18 fluorodeoxyglucose uptake in normal and hibernating myocardium after glucose and insulin loading

ObjectiveF-18 fluorodeoxyglucose (FDG) positron emission tomography (PET) has been increasingly used in myocardial viability imaging. In routine PET viability studies, oral glucose and intravenous insulin loading is commonly utilized. In an optimal study, glucose and insulin loading is expected to cause FDG uptake both in hibernating and normal myocardium. However, in routine studies it is not uncommon to see absent or reduced FDG uptake in normal myocardium. In this retrospective study we further analyzed our PET viability images to evaluate FDG uptake status in myocardium under the oral glucose and intravenous insulin loading protocol that we use in our hospital. MethodsPatients who had both myocardial perfusion single photon emission computed tomography (SPECT) and FDG PET cardiac viability studies were selected for analysis. FDG uptake status in normal and abnormal myocardial segments on perfusion SPECT was evaluated. Based on SPECT and PET findings, patients were divided into two main groups and four subgroups. Group 1 included PET viable studies and Group 2 included PET-nonviable studies. Subgroups based on FDG uptake in normal myocardium were 1a and 2a (normal uptake) and 1b and 2b (absent or significantly reduced uptake). ResultsSeventy-one patients met the inclusion criteria. Forty-two patients were PET-viable and 29 were PET-nonviable. In 33 of 71 patients (46.4%) there was absent or significantly reduced FDG uptake in one or more normal myocardial segments, which was identified more in PET-viable than PET-nonviable patients (59.5% vs. 27.5%, p=0.008). This finding was also more frequent in diabetic than nondiabetic patients (53% vs. 31.8%), but the difference was not significant (p=0.160). ConclusionsIn nearly half of our patients, one or more normal myocardial segments showed absent or significantly reduced FDG uptake. This finding, particularly if it is diffuse, could be from suboptimal study, inadequacy of current glucose and insulin loading protocols, or various other patient-related causes affecting FDG uptake both in the normal and hibernating myocardium. In cases with significantly reduced FDG uptake in normal myocardium, PET images should be interpreted cautiously to prevent false-negative results for viability.

Long-Term Follow-Up of Outcomes With F-18-Fluorodeoxyglucose Positron Emission Tomography Imaging-Assisted Management of Patients With Severe Left Ventricular Dysfunction Secondary to Coronary Disease.

Whether viability imaging can impact long-term patient outcomes is uncertain. The PARR-2 study (Positron Emission Tomography and Recovery Following Revascularization) showed a nonsignificant trend toward improved outcomes at 1 year using an F-18-fluorodeoxyglucose positron emission tomography (PET)-assisted strategy in patients with suspected ischemic cardiomyopathy. When patients adhered to F-18-fluorodeoxyglucose PET recommendations, outcome benefit was observed. Long-term outcomes of viability imaging-assisted management have not previously been evaluated in a randomized controlled trial. PARR-2 randomized patients with severe left ventricular dysfunction and suspected CAD being considered for revascularization or transplantation to standard care (n= 195) versus PET-assisted management (n=197) at sites participating in long-term follow-up. The predefined primary outcome was time to composite event (cardiac death, myocardial infarction, or cardiac hospitalization). After 5 years, 105 (53%) patients in the PET arm and 111 (57%) in the standard care arm experienced the composite event (hazard ratio for time to composite event =0.82 [95% confidence interval 0.62-1.07]; P=0.15). When only patients who adhered to PET recommendations were included, the hazard ratio for the time to primary outcome was 0.73 (95% confidence interval 0.54-0.99; P=0.042). After a 5-year follow-up in patients with left ventricular dysfunction and suspected CAD, overall, PET-assisted management did not significantly reduce cardiac events compared with standard care. However, significant benefits were observed when there was adherence to PET recommendations. PET viability imaging may be best applied when there is likely to be adherence to imaging-based recommendations. URL: http://www.clinicaltrials.gov. Unique identifier: NCT00385242.

&lt;sup&gt;18&lt;/sup&gt;F-FDG PET Viability Assessment for the Improvements of Prognosis of the Patients with Left Ventricular Dysfunction

Positron emission tomography (PET) has greater temporal and spatial resolution. 18 F-fluorodeoxyglucose ( 18 F

Combining FDG-PET and 99mTc-SPECT to predict functional outcome after coronary artery bypass surgery.

Single-photon emission computed tomography (SPECT) and positron emission tomography (PET) are suggested to improve clinical decision-making in ischaemic cardiomyopathy. Here, we present a unique cohort of patients who underwent nuclear medicine studies and cardiac magnetic resonance imaging (MRI) both before and 1 year after coronary artery bypass (CABG) surgery to assess benefit from surgery. Before CABG, we applied three quantitative techniques using (18)F-fluorodeoxyglucose-PET and (99m)technetium-tetrofosmin-SPECT with a software tool to measure defects with hypoperfused but viable and non-viable myocardium in 15 patients. One method used solely PET, two others combined PET and SPECT at different thresholds. As a reference, we used change in left-ventricular (LV) function and volume by MRI. Preoperatively, ischaemic but viable areas detected by the method with a 10% threshold combining PET-SPECT and the PET-only method correlated significantly with preoperative regional wall thickening (WT; P = 0.03 and P = 0.005, respectively). When compared with global functional outcome (change in LV ejection fraction) and LV remodelling (change in end-diastolic volume) 1 year postoperatively, no correlation appeared with preoperative PET- or PET-SPECT-derived viable or non-viable tissue. Neither was any correlation observable between local change in WT and local preoperative defect size evaluated by any of these three methods. Preoperatively, PET and PET-SPECT with 10% threshold detected dysfunctional myocardium, but all analysis methods failed to predict 1-year functional outcome assessed by MRI. In patients with three-vessel disease and heart failure, SPECT perfusion and PET viability study results show substantial heterogeneity; this should be considered when selecting patients for revascularization.

New SPECT and PET radiopharmaceuticals for imaging cardiovascular disease.

Nuclear cardiology has experienced exponential growth within the past four decades with converging capacity to diagnose and influence management of a variety of cardiovascular diseases. Single photon emission computed tomography (SPECT) myocardial perfusion imaging (MPI) with technetium-99m radiotracers or thallium-201 has dominated the field; however new hardware and software designs that optimize image quality with reduced radiation exposure are fuelling a resurgence of interest at the preclinical and clinical levels to expand beyond MPI. Other imaging modalities including positron emission tomography (PET) and magnetic resonance imaging (MRI) continue to emerge as powerful players with an expanded capacity to diagnose a variety of cardiac conditions. At the forefront of this resurgence is the development of novel target vectors based on an enhanced understanding of the underlying pathophysiological process in the subcellular domain. Molecular imaging with novel radiopharmaceuticals engineered to target a specific subcellular process has the capacity to improve diagnostic accuracy and deliver enhanced prognostic information to alter management. This paper, while not comprehensive, will review the recent advancements in radiotracer development for SPECT and PET MPI, autonomic dysfunction, apoptosis, atherosclerotic plaques, metabolism, and viability. The relevant radiochemistry and preclinical and clinical development in addition to molecular imaging with emerging modalities such as cardiac MRI and PET-MR will be discussed.

Relationship between myocardial viability, myocardial blood flow and coronary anatomy by positron emission tomography integrated with multislice computed tomography

The relationship between myocardial viability, myocardial blood flow and the degree of epicardial coronary stenosis in patients with coronary artery disease and left ventricular dysfunction is unclear. Objective The purpose of this study is to determine whether positron emission tomography (PET) viability patterns and myocardial flow at rest correlate with the degree of epicardial coronary stenosis. Methods Myocardial viability was evaluated in 27 patients by the combined analysis of 13N-Ammonia (13NH3) perfusion and 18F-2-fluoro-2-deoxyglucose (FDG) metabolism to identify four PET patterns: match (concordant reduced uptake of both radiotracers), mismatch (hypoperfusion with preserved FDG uptake), reverse mismatch (preserved perfusion and reduced FDG uptake) and preserved uptake of both radiotracers. Myocardial blood flow was calculated using a two-compartment model. Coronary artery stenosis was classified as mild ( 50%), severe (>70%) and critical (≥90%). Results In the 459 analyzed segments, 33% were match, 12% mismatch, 11% reversemismatch and 44% preserved patterns. Mismatch, reverse-mismatch and preserved patterns exhibited higher flows than the match pattern (p<0.01). Fifteen coronary lesions were mild, 7 moderate, 20 severe and 39 critical. There was no correlation between the degree of coronary stenosis and viability patterns (R<0.2, p=NS) or blood flow values (R=0.12). Analysis by vascular territory did not correlate with the degree of coronary stenosis (p=NS). Conclusions Lack of correlation between PET viability patterns, degree of epicardial stenosis and myocardial blood flow suggest that coronary anatomy can neither differentiate viable from necrotic myocardium nor predict the functional status of myocardial flow in patients with left ventricular dysfunction.

Cardiac positron emission tomography imaging

Cardiac positron emission tomography (PET) imaging has advanced from primarily a research tool to a practical, high-performance clinical imaging modality. The widespread availability of state-of-the-art PET gamma cameras, the commercial availability of perfusion and viability PET imaging tracers, reimbursement for PET perfusion and viability procedures by government and private health insurance plans, and the availability of computer software for image display of perfusion, wall motion, and viability images have all been a key to cardiac PET imaging becoming a routine clinical tool. Although myocardial perfusion PET imaging is an option for all patients requiring stress perfusion imaging, there are identifiable patient groups difficult to image with conventional single-photon emission computed tomography imaging that are particularly likely to benefit from PET imaging, such as obese patients, women, patients with previous nondiagnostic tests, and patients with poor left ventricular function attributable to coronary artery disease considered for revascularization. Myocardial PET perfusion imaging with rubidium-82 is noteworthy for high efficiency, rapid throughput, and in a high-volume setting, low operational costs. PET metabolic viability imaging continues to be a noninvasive standard for diagnosis of viability imaging. Cardiac PET imaging has been shown to be cost-effective. The potential of routine quantification of resting and stress blood flow and coronary flow reserve in response to pharmacologic and cold-pressor stress offers tantalizing possibilities of enhancing the power of PET myocardial perfusion imaging. This can be achieved by providing assurance of stress quality control, in enhancing diagnosis and risk stratification in patients with coronary artery disease, and expanding diagnostic imaging into the realm of detection of early coronary artery disease and endothelial dysfunction subject to risk factor modification. Combined PET and x-ray computed tomography imaging (PET-CT) results in enhanced patient throughput and efficiency. The combination of multislice computed tomography scanners with PET opens possibilities of adding coronary calcium scoring and noninvasive coronary angiography to myocardial perfusion imaging and quantification. Evaluation of the clinical role of these creative new possibilities warrants investigation.

FDG PET image quality during hyperinsulinemic euglycemic clamp in ischemic cardiomyopathy with and without diabetes mellitus

Background: Positron emission tomography (PET) with fluorine-18 fluorodeoxyglucose (FDG) can be utilized to assess myocardial viability. The objective of this study was to assess FDG PET image quality during the hyperinsulinemic euglycemic clamp (HE clamp) in patients with and without diabetes referred for myocardial viability assessment. Methods: Consecutive FDG PET viability scans at Mayo Clinic from June 2000Nov 2003 were reviewed retrospectively. Scans were performed using static acquisition. Image quality was visually assessed at the time of reading by two experienced observers. Image quality was also assessed by calculating the myocardium to blood pool (M/B) activity ratio (mean activity from regions of interest over normal myocardium and the LV cavity, averaged over three midventricular slices). Results: 81 of 82 FDG PET scans utilized the HE clamp; 39 Type 2 diabetics (DM2), 2 Type 1 diabetics, and 40 non-diabetics (Non-DM). By visual assessment, images were inadequate in 1 DM2 (M/B=1.6) and 1 Non-DM (M/B=1.8). All other patients (97%) had adequate images (M/B range 2.2–30.0). DM2 Non-DM P-Value Age, yrs 67.4 ± 10.3 64.8 ± 13.0 NS BM, kg/m 22 30.9 ± 5.9 27.7 ± 5.4 0.02 LVEF, % 27.3 ± 9.5 29.8 ± 11.0 NS Blood glucose before clamp, mg/dL 141.1 ± 34.6 101.7 ± 13.3 0.0001 Clamp start to FDG injection, min 155.7 ± 71.8 104.7 ± 35.1 0.0001 FDG injection to scan, min 39.8 ± 10.9 39.8 ± 16.1 NS Blood glucose during scan, mg/dL 91.6 ± 10.5 85.4 ± 13.3 0.03 Dextrose infusion during scan, mg/kg/min 3.1 ± 1.6 3.9 ± 1.6 0.02 M/B ratio 6.5 ± 4.6 8.1 ± 4.6 0.06 Conclusions: HE clamp yielded adequate image quality in >97% of both diabetic and non-diabetic patients referred for FDG PET myocardial viability assessment. HE clamp time was longer in diabetics, primarily due to higher baseline glucose and longer time until FDG injection.

Baseline/post-nitrate Tc-99m tetrofosmin mismatch for the assessment of myocardial viability in patients with severe left ventricular dysfunction: comparison with baseline Tc-99m tetrofosmin scintigraphy/FDG PET imaging

Background Positron emission tomography (PET) flow/metabolic mismatch is considered the nuclear medicine gold standard for the assessment of myocardial viability. The aim of this study was to investigate whether baseline/nitrate technetium 99m tetrofosmin single photon emission computed tomography (SPECT) mismatch may provide equivalent clinical information. Methods and results We studied 23 patients (aged 62 ± 10 years, 19 men) with previous myocardial infarction (16 anterior, 4 inferior, and 3 anterior plus inferior) and postischemic heart failure (gated SPECT [G-SPECT] ejection fraction, 26% ± 8%). All patients underwent Tc-99m tetrofosmin G-SPECT at rest and after nitrates (intravenous isosorbide dinitrate, 0.2 mg/mL, 10 mL/h) as well as a fluorine 18 fluoro-2-deoxy- d-glucose (FDG) PET scan. Regional wall motion analysis was performed with quantitative G-SPECT (QGS). Myocardial dysfunction was defined as a regional QGS score of 2 or greater. Regional perfusion was assessed by quantitative perfusion score (QPS) providing percent Tc-99m tetrofosmin uptake in a 20-segment model. Semiquantitative analysis of FDG uptake was performed by use of polar maps generated by Siemens ECAT HR + software. In areas with a perfusion rate lower than 80%, PET viability was identified by a normalized FDG percent uptake/baseline Tc-99m tetrofosmin percent uptake ratio greater than 1.2. We analyzed 460 segments; 298 (64%) were dysfunctional by QGS analysis. Of these, 170 were viable by PET imaging whereas 128 were nonviable. Regional Tc-99m tetrofosmin uptake was higher in viable than in nonviable segments both at rest (60% ± 24% vs 42% ± 12%, P < .01) and after nitrates (67% ± 20% vs 41% ± 18%, P < .01). According to receiver operating characteristic curve analysis, a cutoff value of 63% for resting as well as post-nitrate G-SPECT provided the highest diagnostic accuracy for the detection of myocardial viability (67% and 72% at rest and after nitrates, respectively). When the same algorithm used for the comparison with PET (normalized nitrate percent uptake/baseline percent uptake) was applied to G-SPECT, we obtained the highest agreement with PET (accuracy, 93%; sensitivity, 95%; specificity, 92%). Conclusions In patients with severe left ventricular dysfunction, perfusion data alone, both at rest and after nitrates, do not allow an accurate estimate of myocardial viability. In dysfunctioning segments, the analysis of rest/post-nitrate Tc-99m tetrofosmin mismatch provides results similar to those obtained by PET flow/metabolic mismatch.

Gated fluorine 18 fluorodeoxyglucose positron emission tomography: determination of global and regional left ventricular function and myocardial tissue characterization

Background Our objectives were to investigate the accuracy of global and regional left ventricular (LV) function parameters determined from gated fluorine 18 deoxyglucose (FDG) positron emission tomography (PET) and to determine whether this approach complements viability imaging data for tissue characterization. Nongated FDG-PET is a clinical standard for viability imaging, but LV function is often determined with other techniques, which increases patient burden, expenditure, and co-registration errors. Better tissue characterization may be achieved if data were acquired with one test. Methods and results Forty-eight patients with LV dysfunction (including 35 with ejection fraction [EF] ≤35%) underwent perfusion/FDG imaging with gating of the FDG images and radionuclide angiography (RNA) 6 ± 6 days apart. Regional function (wall motion/thickening) and viability pattern (normal, mismatch, nontransmural scar, and transmural scar) were determined for 301 segments. Global EFs from FDG-PET (29.3% ± 11.5%) and RNA (31.1% ± 10.4%) were well correlated: EF FDG-PET = 0.91 × EF RNA + 0.91 ( r = 0.83, P < .00001). Regional wall motion concordance between PET and RNA with three wall motion scores was 67% with moderate agreement (κ = 0.50, P < .001). PET viability was also determined for each segment. The relative frequency of normal motion compared with abnormal motion decreased with worsening viability classification. Of the normal segments, 96 of 139 (69%) had reduced wall motion, suggesting repetitively stunned myocardium. Segments classified as normal or mismatch had a higher frequency of normal wall thickening (65% and 52%) than wall motion (31% and 17%). No segments classified as transmural scar exhibited normal wall thickening. Conclusion Gated FDG-PET accurately measures global LV function. Regional function can also be determined with reasonable accuracy. This approach also provides precise co-registration of function with metabolic information and thus improved tissue characterization of the myocardium. Gated FDG-PET has the potential to assist in optimizing management of this patient population.

Ischemically compromised myocardium displays different time-courses of functional recovery: correlation with morphological alterations?

It has been demonstrated that positron emission tomography (PET) predicts the functional recovery of viable but ischemically compromised myocardium. Reversible contractile dysfunction after revascularization has been reported for 'hibernating myocardium' and stunned myocardium, however, there are little data concerning the time-course and the extent of improvement of the two different pathophysiological conditions. Twenty-nine patients with advanced coronary artery disease and severely reduced left ventricular function (EF 18--35%) who were referred for isolated coronary artery bypass grafting underwent preoperative PET viability assessment and were functionally assessed by two-dimensional echocardiography preoperatively at 11 days, 14 weeks, and more than 12 months after surgical revascularization. Intraoperative biopsies were taken from dysfunctional areas defined by PET as segments of normal perfusion and normal metabolism (stunned myocardium) and from areas with a 'mismatch' between perfusion and metabolism (hibernating myocardium). The degree of morphological alterations was evaluated by electron microscopy. In 70% of the 240 dysfunctional segments, 'stunned myocardium' was present whereas 'hibernating myocardium' could be detected in only 24% (P < 0.01). Hibernating myocardium was associated with more severe preoperative wall motion abnormalities and incomplete postoperative recovery. After 1 year, 31% of 'stunned' segments vs. only 18% of 'hibernating' segments showed complete functional restoration (P < 0.05). This incomplete improvement was associated with more severe morphological alterations including depletion of sarcomeres, accumulation of glycogen, loss of sarcoplasmatic reticulum, and cellular sequestration. These data indicate that in patients with severe ischemic left ventricular dysfunction 'stunned myocardium' is more prevalent than 'hibernation'. Functional normalization is more frequent in 'stunned' segments, whereas areas of 'hibernation' showed more severe tissue injury and protracted recovery. Different degrees of myocardial injury coexist in most patients, which determines the time-course and the extent of improvement after revascularization.

99m Tc-Sestamibi SPECT is a Useful Technique for Viability Detection. Results of a Comparison with NH 3 /FDG PET

Objective - Assessment of myocardial viability by 99m Tc-Sestamibi Single Photon Emission Computerized Tomography (SPECT) has been suggested as a more readily available and cheaper alternative to Positron Emission Tomography (PET) with 13 N-ammonia (NH 3 ) and 18 F-fluoro-deoxy-glucose (FDG). We hypothesized that a semi-quantitative evaluation by SPECT could delineate myocardial viability with an acceptable concordance to PET. Design - Fifty patients (age 57 - 7 years; ejection fraction 28 - 8%), with ischemic cardiomyopathy, underwent SPECT and PET imaging in random order. Viability by SPECT was defined as a defect size <50% of the segment area, or a defect representing S 50% of the segment but with a mean activity S 50% of peak activity. PET viability was defined as a perfusion score >2 and FDG score h 2 (five-point scale, 0 = normal, 4 = absent activity). Results - By segmental comparison to PET, SPECT yielded a sensitivity and specificity of 87% and 82% for detection of viable myocardium. The positive and negative predictive values were 96% and 58%, respectively. Conclusion - In patients with severe ischemic cardiomyopathy 99m Tc-Sestamibi SPECT can delineate viable myocardium with an acceptable segmental concordance to NH 3 /FDG PET.

722-2 Predicting Viability and Functional Recovery with Dobutamine Echocardiography and Positron Emission Tomography

Positron emission tomography (PET) is considered the gold standard for detecting myocardial viability. Unfortunately, PET is limited by availability and cost. Dobutamine echocardiography (DE) may be a cost effective and more available method of detecting viability. This report compared DE with PET in 33 patients (pts) with advanced coronary disease using a 16 segment model for left ventricular wall motion and uptake of fluorodeoxyglucose (FDG). PET viability was defined as normal or mildly reduced uptake of FDG. DE viability was defined as preserved wall motion at rest or augmentation during DE. PET showed evidence of viability in 93% (157/169) of segments with normal rest wall motion, 85% (62/73) of mildly hypokinetic segments and 93% (68/73) of severely hypokinetic segments. DE and PET were concordant in only 41% (71/175) of akinetic segments (46 nonviable and 25 viable). To investigate this discordance we evaluated follow up echocardiograms (≥four weeks) after coronary bypass surgery in 8 pts with 36 akinetic segments at rest. The ability of PET and DE to predict functional recovery of wall motion is as shown:Empty Cell(+)PV(-)PVSensSpecPET0.440.850.850.44DE0.600.730.460.83PV = predictive value PV = predictive value 1) Normal, mildly hypokinetic or severely hypokinetic rest wall motion on echo correlates strongly with PET evidence of viability. 2) For functional recovery of akinetic segments, PET is sensitive but not specific and DE is specific but not sensitive.

722-1 High Dose Dobutamine Echocardlography Detects Myocardial Viability and Ischemia in Coronary Cardiomyopathy

Augmentation of wall motion during low dose ( ≤ 10 meg/kg/min) dobutamine infusion has been utilized to detect myocardial viability in patients with ischemic cardiomyopathy. The utility of high dose (30–50 mcglkg/min) dobutamine infusion to detect viable and compromised myocardium has not been described. Thirty-three patients with ischemic cardiomyopathy (mean EF of 0.33 ± 0.084) had low and high dose dobutamine echocardiograms and positron emission tomography (PET) using N-13 ammonia (NH3) and fluorodeoxyglucose (FOG). Left ventricular wall motion, NH3 and FDG uptake were scored using a 16 segment model. Of 490 interpretable segments, 321 (66%) were abnormal at rest. At low dose 85 (27%) segments augmented of which 80 (94%) were viable by PET. In 15 patients, an additional 32 (10%) abnormal segments augmented at high dose. PET viability was noted in 29 (91%) of these segments. In 18 of 33 patients (55%), 38 segments had stress induced wall motion abnormalities at high dose. Of the 38 segments, 37 (97%) were viable by PET. Angiography showed 34 of these 38 (89%) segments were supplied by an obstructed coronary artery ( ≥ 50% diameter stenosis). 1) The use of higher doses increases the sensitivity of DE to detect viable myocardium. 2) Deterioration of wall motion at peak indicates viable but compromised myocardium supplied by an obstructed coronary artery.

Beneficial effect of residual anterograde flow on tissue viability as assessed by positron emission tomography in patients with myocardial infarction.

With the advent of therapeutic interventions to restore blood flow in patients with acute infarction, early identification of salvageable myocardium has gained clinical importance. It was the purpose of this study to define regional blood flow and glucose metabolism in patients with acute myocardial infarction as assessed by positron emission tomography (PET) and to correlate these findings with coronary anatomy. In 15 patients blood flow as determined by N-13 ammonia was reduced in 37 left ventricular segments. In 20 segments there was a similar decrease in FDG uptake, consistent with tissue necrosis. In contrast, 17 segments with reduced blood flow revealed maintained FDG uptake suggesting residual viability in the electrocardiographically defined 'infarct segment'. PET viability and necrosis was significantly associated with presence or absence of anterograde flow in the infarct artery. Evaluation of regional wall motion did not distinguish segments with PET criteria for viability from segments with necrosis. Thus, in patients without thrombolytic therapy during evolving myocardial infarction, spontaneous reperfusion appears to be beneficial for tissue survival. PET offers the unique possibility to assess tissue viability early after the ischaemic injury where evaluation of wall motion fails to identify salvageable myocardium.