Electromechanical mapping for determination of myocardial contractility and viability. A comparison with echocardiography,myocardial single-photon emission computed tomography,and positron emission tomography

OBJECTIVE: The purpose of this study was to validate electromechanical viability parameters with combined myocardial perfusion and metabolic imaging and echocardiography. BACKGROUND: The NOGA System is a catheter-based, non-fluoroscopic, three-dimensional endocardial mapping system. This unique technique allows accurate simultaneous assessment of both local electrical activity and regional contractility. METHODS: The results of NOGA, myocardial single-photon emission computed tomography (SPECT), positron emission tomography, and echocardiography in 51 patients with coronary artery disease and a pathologic SPECT study were transcribed in a nine-segment bull's-eye projection and compared.The local shortening of normally contracting segments, as shown by echocardiography, was 9.2 +/- 5.1%, which decreased to 6.6 +/- 5.0% and 4.1 +/- 5.2% in hypokinetic and akinetic segments. The highest unipolar voltage (11.2 +/- 5.0 mV) and local shortening (8.2 +/- 5.0%) characterized normally perfused segments. Fixed perfusion defects with normal or limited 18-fluoro-2-deoxy-D-glucose uptake indicating viability had a significantly higher unipolar voltage than did scar tissue (7.25 +/- 2.7 vs. 5.0 +/- 3.1 mV, p = 0.029). CONCLUSION: Electromechanical parameters sufficiently defined the viability state of the myocardium and showed good concordance with the findings by nuclear perfusion and metabolism imaging and echocardiography. The NOGA technique provides all the relevant information immediately after coronary angiography and enables the physician to proceed with therapy in the same setting.     

Electromechanical mapping for detecting myocardial viability and ischemia in patients with severe ischemic cardiomyopathy

This study was designed to evaluate several electromechanical mapping parameters for assessment of myocardial viability and inducible ischemia as defined by dipyridamole single-photon emission computed tomographic (SPECT) imaging at rest in patients with severe ischemic cardiomyopathy. Unipolar voltage, normalized unipolar voltage, bipolar voltage, and fragmentation were compared with tracer uptake at rest and reversibility on stress or rest quantitative technetium-99m sestamibi SPECT imaging in 32 patients with severe ischemic cardiomyopathy (left ventricular ejection fraction 0.24 +/- 0.08). In dysfunctional myocardial segments, logistic regression showed unipolar voltage, normalized unipolar voltage, and bipolar voltage to be predictive of viable myocardium (> or = 60% tracer uptake at rest) and was significantly higher in viable than in nonviable segments (p <0.01). A unipolar voltage of > or = 7.1 mV was the best predictor of viable myocardium. In dysfunctional viable segments, unipolar voltage was significantly higher in reversible than in fixed segments (p <0.001), and a unipolar voltage of > or = 8.5 mV had optimal power for identifying reversibility on dipyridamole SPECT imaging. We conclude that in patients with severe ischemic cardiomyopathy, unipolar voltage can identify viable from nonviable myocardium and reversible from fixed viable defects as defined by dipyridamole technetium-99m sestamibi SPECT imaging.     

药物负荷试验核素心肌断层显像识别存活心肌

目的探讨药物多巴酚丁胺、硝酸异山梨酯负荷试验核素锝[^99mTc]甲氧异丁异腈（technetium [^99mTc] methoxy isobutyl isonitrile,^99mTc-MIBI）心肌断层显像识别存活心肌的价值。方法对48例陈旧性心肌梗死伴左心室收缩功能受损患者进行静息心肌^99mTc-MIBI心肌断层显像和多巴酚丁胺、硝酸异山梨酯负荷试验^99mTc-MIBI心肌断层显像,用半定量的方法将^99mTc-MIBI摄取进行评分,区分存活心肌和非存活心肌。结果^99mTc-MIBI显像判定,经皮冠状动脉介入术前存活心肌节段有279个．非存活心肌节段235个;经多巴酚丁胺加硝酸异山梨酯负荷后,心肌显像改善：轻度稀疏节段9个、中度稀疏节段24个、严重稀疏或缺损节段10个,共计43个节段显像改善,评分减少1分以上,存活心肌节段313个,非存活心肌节段201个。两组差异有统计学意义（P〈0．05）。经皮冠状动脉介入术后6个月,随访多巴酚丁胺加硝酸异山梨酯负荷后,心肌显像改善的32个节段发现,静息^99mTc-MIBI显像改善,另有8个受损节段正常化。多巴酚丁胺加硝酸异山梨酯负荷后心肌显像无变化的389个节段在经皮冠状动脉介入术后346个节段无变化。多巴酚丁胺加硝酸异山梨酯负荷心肌显像检测存活心肌的阳性预测值93％,阴性预测值89％。结论多巴酚丁胺加硝酸异山梨酯负荷后心肌显像对存活心肌的识别能够提高存活心肌的检出率。其阳性预测值和阴性预测值较好。     

Dipyridamole myocardial perfusion single photon emission computed tomography in patients with slow coronary flow

OBJECTIVE: Several studies have indicated that the velocity of contrast dye increases after intravenous dipyridamole infusion in patients with a slow-flow pattern (SFP). In this study we compared the results of coronary arteriography and exercise myocardial perfusion single photon emission computed tomography (SPECT) in patients with SFP. We also investigated the changes in myocardial perfusion in patients with abnormal exercise myocardial perfusion SPECT by using a pharmacological stress test with dipyridamole. DESIGN AND PATIENTS: This study included 60 patients who revealed SFP in their coronary arteriograms. Slow coronary flow diagnoses were made using the frame count method. A single day rest-exercise technetium-99m hexakis-2-methoxy-isobutyl isonitrile (Tc-99m MIBI; Du Pont Pharma SA, Belgium) SPECT was performed in all patients. Patients who had reversible perfusion defect (RPD) on the exercise SPECT were evaluated with dipyridamole myocardial perfusion scintigraphy.RESULTS Patients with SFP revealed both higher frame counts in native coronary arteries and higher mean frame counts. The coronary frame count was 26.4 +/- 3.5 in control patients and 64.40 +/- 16.64 in patients with SFP, respectively (P < 0.001). Exercise perfusion SPECT showed RPD in 17 patients (group 1), but was normal in 43 others (group 2). There were no statistically significant differences between groups 1 and 2 in frame counts. Myocardial perfusion was normalized in all 17 patients of group 1 after dipyridamole infusion. CONCLUSIONS: In patients with SFP perfusion, changes may improve with dipyridamole infusion. This study indicates that this improvement can be shown by dipyridamole SPECT. Furthermore, no correlation was observed between the time needed to fill a native coronary artery and RPD of the myocardium.     

Fluorine-18 FDG imaging in hepatocellular carcinoma using positron coincidence detection and single photon emission computed tomography

BACKGROUND/AIMS: We prospectively evaluated whether fluorine-18 deoxyglucose (FDG) positron coincidence detection (PCD) or FDG single-photon emission computed tomography (SPECT) provides additional benefits to our conventional preoperative evaluation of lesion detection in patients suspected to have hepatocellular carcinoma (HCC). METHODS: Thirteen consecutive patients with a suspected HCC underwent conventional preoperative evaluation with ultrasonography (US), triple-phase helical computed tomography (CT), superparamagnetic iron oxides (SPIO) enhanced magnetic resonance imaging (MRI) and serum alpha-fetoprotein (AFP) level. All 13 patients had an FDG-PCD and SPECT. These results were evaluated to assess the value of FDG-PCD and SPECT in addition to US, SPIO-enhanced MRI and triple-phase helical CT. RESULTS: Ten of the 13 (77%) patients had at least one histologically confirmed HCC without extrahepatic abdominal spread. The tumors ranged in size from 1 to 8 cm and the serum AFP ranged from 3 to 30 000 microg/l. Of these 10 patients, two patients had an increased tumor F-FDG uptake (sensitivity of 20%); one patient with an AFP of 5 microg/l and a tumor size of maximum 4.5 cm and one patient with an AFP of 249 microg/l and a tumor size of maximum 2 cm. In three patients with a benign liver mass, FDG imaging with either PCD or SPECT was negative. There was no false positive finding. CONCLUSIONS: We found poor sensitivity of FDG-PCD and FDG-SPECT for the detection of HCC. There were no clear relations between AFP or tumor size and FDG uptake. Therefore, we conclude that FDG imaging with PCD or SPECT has no value in the preoperative work-up for HCC in patients with cirrhosis.     

Developments in nuclear cardiology: transition from single photon emission computed tomography to positron emission tomography-computed tomography

Recent advances in positron emission tomography (PET) instrumentation have paralleled those of multichannel computed tomography (CT) for cardiac applications. Whereas multichannel CT angiography provides information on the presence and extent of anatomical luminal narrowing of epicardial coronary arteries, stress myocardial perfusion PET provides information on the downstream functional consequences of such anatomic lesions. With the advent of hybrid PET/CT systems, such complementary information of anatomy and physiology can be realized immediately at the same imaging session. By acquiring dynamic, gated myocardial perfusion data, PET studies provide insight into impairment of regional coronary blood flow reserve and microvascular endothelial dysfunction. This paper presents recent developments in PET detector materials, acquisition modes, combined PET/CT scanners, rubidium-82 (Rb-82) gated myocardial perfusion studies and analysis methods for absolute myocardial blood flow quantification.     

Assessment of left ventricular function by electrocardiogram-gated myocardial single photon emission computed tomography using quantitative gated single photon emission computed tomography software]

Electrocardiogram (ECG)-gated myocardial single photon emission computed tomography (SPECT) can assess left ventricular (LV) perfusion and function easily using quantitative gated SPECT (QGS) software. ECG-gated SPECT was performed in 44 patients with coronary artery disease under post-stress and resting conditions to assess the values of LV functional parameters, by comparison to LV ejection fraction derived from gated blood pool scan and myocardial characteristics. A good correlation was obtained between ejection fraction using QGS and that using cardiac blood pool scan (r = 0.812). Some patients with myocardial ischemia had lower ejection fraction under post-stress compared to resting conditions, indicating post-stress LV dysfunction. LV wall motion and wall thickening were significantly impaired in ischemic and infarcted myocardium, and the degree of abnormality in the infarcted areas was greater than in the ischemic area. LV functional parameters derived using QGS were useful to assess post-stress LV dysfunction and myocardial viability. In conclusion, ECG-gated myocardial SPECT permits simultaneous quantitative assessment of myocardial perfusion and function.     

Measurement of myocardial infarction fraction using single photon emission computed tomography

Although infarct size correlates generally with prognosis after acute myocardial infarction, an absolute measure of infarct size may have differing prognostic significance depending on absolute left ventricular mass. To test the hypothesis that single photon emission computed tomography can accurately measure myocardial infarct size as a percent of total left ventricular mass ("infarction fraction"), thallium-201 and technetium-99m pyrophosphate tomograms were acquired in 21 dogs 24 to 48 hours after fixed occlusion of the left anterior descending or circumflex coronary artery. Pathologic infarct weight was measured as the myocardial mass that showed no staining with triphenyltetrazolium chloride. Scintigraphic infarct mass by technetium-99m pyrophosphate was calculated from the total number of left ventricular volume elements (voxels) demonstrating technetium-99m pyrophosphate uptake X voxel dimension [( 0.476 cm]3) X specific gravity of myocardium (1.05 g/cm3). Scintigraphic left ventricular mass was calculated in a similar fashion using an overlay of the thallium-201 and technetium-99m pyrophosphate scans. The "infarction fraction" was calculated as: infarction fraction = infarct mass/left ventricular mass. There was good correlation between single photon emission computed tomography and pathologic measurements of infarct mass (technetium-99m pyrophosphate mass = 1.01 X pathologic infarct mass + 0.96; r = 0.98), left ventricular mass (single photon emission computed tomographic left ventricular mass = 0.60 X pathologic left ventricular mass + 37.4; r = 0.86) and "infarction fraction" (single photon emission computed tomographic infarction fraction = 1.09 X pathologic infarction fraction - 1.7; r = 0.94).(ABSTRACT TRUNCATED AT 250 WORDS)     

Positron emission tomography and computed tomography versus positron emission tomography computed tomography: tools for imaging the lung

This article reviews the potential use of positron emission tomography (PET), alone and in combination with computed tomography, for evaluating the severity of disease in cystic fibrosis. PET scanning using injected 18F-fluorodeoxyglucose provides visual and quantitative information for the rate at which glucose is taken up by the lung, a process that should relate to the presence of inflammation and reflect the extent of the disease. The computed tomography scan gives highly accurate density and anatomic information to locate areas of inflammation seen on the PET scan, increasing the accuracy of the interpretation. Until recently, the scanners have been single systems, often located in separate hospital departments. Combined systems are now commercially available, with major advantages for patients and in the quality of analytical information obtained for interpretation by the physician. The use of 18F-fluorodeoxyglucose uptake and PET scanning has been suggested as a biomarker of progressive pulmonary inflammation in cystic fibrosis. Although promising, the data so far are limited. Further studies will be needed to validate this measurement for this purpose.     

Myocardial perfusion imaging with positron emission tomography and single photon emission computed tomography: frequency and causes of disparate results

The purpose of this study was to compare rubidium-82 PET withthallium-201 SPECT imaging in 150 patients. Both techniquesfollowed a single dipyridamole-handgrip stress, and images weredisplayed using the same 3-dimensional format and quantitativecolour scale. Coronary arteriography was employed to assignthe correct diagnosis in situations of disparity. Results of PET and SPECT were at least partially concordantin 110 patients (73%), although 22 had more than one defect.A reversible perfusion defect was identified in 60 patients,but the scans were concordant in only 20 (33%). These disparitieswere chiefly due to false-negative SPECT imaging (22 patients,55%), and probable delayed thallium redistri bution (13 patients,33%). No patients had ischaemia correctly identified by SPECTin the presence of normal PET imaging. Persistent defects wereidentified in 91 patients, some of whom also had reversibledefects, and the results were consistent in 54 (59%). Otherthan the delayed thallium redistribution group, the major categoriescausing disparities were false-positive (6 patients, 16%), andfalse negative SPECT (8 patients, 22%), attributable to attenuationand scatter. PET appears able to identify smaller, less ischaemic areas subtendedby milder coronary stenoses. The availability of a true restingscan with Rb-PET enhances the discrimination between ischaemiaand infarction. Attenuation correction, and the high energyphotons of positron annihilation, yield more accurate evaluationof inferior wall defects and greater specificity in the presenceof soft tissue attenuation.     

Real-time myocardial contrast echocardiography for the detection of stress-induced myocardial ischemia. Comparison with 99mTc-sestamibi single photon emission computed tomography

BACKGROUND: Real-time contrast echocardiography (MCE) is a new promising technique for assessing myocardial perfusion. The purpose of this study was to test whether realtime MCE can be used to detect functionally significant coronary artery stenosis in patients with known or suspected coronary artery disease. Myocardial contrast echocardiographic studies were compared with nearly simultaneous 99mTc-sestamibi single photon emission computed tomography (SPECT) as a clinical standard reference to evaluate regional myocardial perfusion defects. METHODS: Real-time MCE based on continuous infusion of Optison (8-10 ml/h) was performed in 66 patients during standard 99mTc-SPECT dipyridamole (0.56 mg/kg x 4 min) stress testing. Images were obtained in apical 4- and 2-chamber views, each divided into 6 segments. Tracer uptake and myocardial opacification were visually analyzed for each segment by two pairs of blinded observers and graded as normal, mildly reduced, severely reduced, or absent. In 792 myocardial segments, myocardial opacification by MCE was uninterpretable in 143 (18%) segments and tracer uptake by SPECT was not clearly defined in 92 (12%) segments. Interobserver variability for MCE was good with concordance rates of 83% (kappa=0.72) for rest- and 86% (kappa=0.76) for stress images. Overall concordance between MCE and SPECT was good (83%, kappa=0.63) at a segmental level. In the diagnosis of fixed and reversible defects, and of normal perfusion, concordance rates were 73, 65 and 83%, respectively. When analysis was performed at the regional level, we found comparable levels of concordance rates for LAD (83%, kappa=0.59), LCX (86%, kappa=0.64) and RCA (80%, kappa=0.68) perfusion territories. CONCLUSIONS: These findings suggest that realtime MCE is a clinically acceptable method to evaluate myocardial perfusion defects during dipyridamole stress testing.     

Differentiation of ischemic from nonischemic cardiomyopathy with positron emission tomography

This study was undertaken to determine whether positron emission tomography (PET) performed after the intravenous injection of 11C-palmitate permits differentiation of patients with ischemic from those with nonischemic dilated cardiomyopathy. PET was performed after intravenous injection of 11C-palmitate in 10 patients with ischemic and in 10 with nonischemic dilated cardiomyopathy. Regions of homogeneously severely depressed accumulation of 11C-palmitate, representing 15% or more of the expected myocardial cross-sectional area, were observed in 8 of 10 patients with ischemic but in none of 10 patients with nonischemic cardiomyopathy. Patients with nonischemic cardiomyopathy had marked spatial heterogeneity of the accumulation of palmitate throughout the left ventricular myocardium, whereas most tomographic sections from patients with ischemic cardiomyopathy accumulated 11C-palmitate more homogeneously in regions exclusive of discrete defects indicative of remote infarction. Thus, a larger number of discrete noncontiguous regions (17 +/- 5 compared with 12 +/- 4, p less than 0.001) and greater reduction of average 11C-palmitate content (59 +/- 6 compared with 64 +/- 10% maximal myocardial radioactivity, p less than 0.05) were seen in the tomographic reconstructions from patients with nonischemic than in those from patients with ischemic cardiomyopathy. These findings support the hypothesis that multiple myocardial infarctions underlie the process seen as dilated cardiomyopathy in patients with coronary artery disease. Our findings indicate that PET permits differentiation of patients with ischemic from those with nonischemic cardiomyopathy.     

Myocardial perfusion imaging with positron emission tomography and single photon emission computed tomography: frequency and causes of disparate results.

The purpose of this study was to compare rubidium-82 PET with thallium-201 SPECT imaging in 150 patients. Both techniques followed a single dipyridamole-handgrip stress, and images were displayed using the same 3-dimensional format and quantitative colour scale. Coronary arteriography was employed to assign the correct diagnosis in situations of disparity. Results of PET and SPECT were at least partially concordant in 110 patients (73%), although 22 had more than one defect. A reversible perfusion defect was identified in 60 patients, but the scans were concordant in only 20 (33%). These disparities were chiefly due to false-negative SPECT imaging (22 patients, 55%), and probable delayed thallium redistribution (13 patients, 33%). No patients had ischaemia correctly identified by SPECT in the presence of normal PET imaging. Persistent defects were identified in 91 patients, some of whom also had reversible defects, and the results were consistent in 54 (59%). Other than the delayed thallium redistribution group, the major categories causing disparities were false-positive (6 patients, 16%), and false negative SPECT (8 patients, 22%), attributable to attenuation and scatter. PET appears able to identify smaller, less ischaemic areas subtended by milder coronary stenoses. The availability of a true resting scan with Rb-PET enhances the discrimination between ischaemia and infarction. Attenuation correction, and the high energy photons of positron annihilation, yield more accurate evaluation of inferior wall defects and greater specificity in the presence of soft tissue attenuation.     

Silent myocardial ischemia in patients with myocardial infarction: evaluation with positron emission computed tomography

To evaluate myocardial blood flow and glucose utilization, N-13 ammonia and F-18 deoxyglucose positron emission tomography were performed in 33 patients with myocardial infarction. The N-13 ammonia study was performed at rest and during supine exercise, and the F-18 deoxyglucose was done at rest after greater than or equal to 5 hours of fasting. Based on angina, exercise-induced hypoperfusion, and deoxyglucose uptake, 3 groups of patients were classified; 10 patients in group I (neither angina nor exercise induced hypoperfusion), 8 patients in group II (painless exercise-induced hypoperfusion) and 15 patients in group III (anginal patients with/without exercise-induced hypoperfusion). The F-18 deoxyglucose positron study demonstrated accumulation of deoxyglucose in 6 patients in group I, 7 in group II, and 14 in group III. Thus, our results indicated that a significant number of patients with antecedent myocardial infarction had exercise-induced hypoperfusion and/or altered glucose metabolism without accompanying anginal pain.