Functional significance of myocardial perfusion defects induced by dipyridamole using thallium-201 single-photon emission computed tomography and two-dimensional echocardiography

The mechanisms responsible for inhomogeneous myocardial blood flow after oral administration of a large dose (300 mg) of dipyridamole were assessed in 27 patients with serial thallium-201 single-photon emission computed tomography (SPECT) and simultaneous 2-dimensional echocardiograms. Myocardial tomographic images were obtained 50 minutes and 3 to 4 hours after administration of dipyridamole. Two-dimensional echocardiograms were recorded at baseline and then every 15 minutes for 60 minutes. Dipyridamole caused only a mild reduction in blood pressure (from 129 +/- 18 to 126 +/- 16 mm Hg) and a mild increase in heart rate (from 69 +/- 15 to 73 +/- 4 beats/min). Sixteen patients had perfusion defects after dipyridamole by SPECT, which underwent partial or total filling-in. Fourteen of these patients (87.5%) had either a new abnormality or further deterioration of a preexisting wall motion abnormality by 2-dimensional echocardiography, and thus were considered to have developed transient ischemia during dipyridamole administration. Ten of 11 patients (91%) with normal perfusion or fixed defects by SPECT had no further deterioration in wall motion after oral dipyridamole, and were thus considered to have no evidence of myocardial ischemia. In conclusion, most patients with transient thallium-201 defects after dipyridamole develop transient worsening of resting wall motion by 2-dimensional echocardiography, suggestive of true myocardial ischemia. Because myocardial oxygen demand, as indicated by the heart rate-blood pressure product, did not change significantly, the mechanism of myocardial ischemia in these patients is likely to be diminished regional blood flow related to a "subendocardial steal" induced by dipyridamole.     

Dobutamine stress echocardiography compared with dipyridamole thallium-201 single-photon emission computed tomography in detecting coronary artery disease

To compare the diagnostic value of dobutamine stress echocardiographywith dipyridamole thallium-201 single-photon emission computedtomography (SPECT) in detecting coronary artery disease (CAD),we performed both tests on 54 patients who also underwent coronaryarteriography. Dobutamine was infused at an incremental regimenof 5,10,20,30 and 40 µg. kg^-1. min^-1. Dipyridamole wasinfused at a rate of 0.14 mg. kg^-1. min^-1 over 4 min. Dobutaminestress echocardiography detected 40 (93%) and SPECT 42 (98%,P=ns) of the 43 patients with significant CAD, defined as (greaterthan or equal) 50% diameter stenosis. The specificity was 73%(8 of 11) for both tests. The sensitivity for detecting individualcoronary artery stenosis with dobutamine stress echocardiographywas 81% (30 of 37) for the left anterior descending artery,75% (24 of 32) for the right coronary artery, and 61% (17 of28) for the left circumflex artery. For SPECT it was 89%, 97%(P>0.05 vs dobutamine stress echocardiography) and 75%, respectively. Among the 97 stenotic coronary arteries, 17 had mild to moderatestenosis (50%-69% diameter stenosis) and 80 had severe stenosis($$70% diameter stenosis). With dobutamine stress echocardiography,53% of the arteries with mild to moderate stenosis were identifiedvs 78% of those with severe stenosis (P<0.05). With SPECT,the sensitivity was 82% (14 of 17) in mild to moderate stenosisand 89% (71 of 80) in severe stenosis (P=ns). No major sideeffects occurred during either test. Thus, both dobutamine stressand SPECT are highly sensitive for detection and localizationof CAD. However, the sensitivity of dobutamine stress is affectedby the level of stenosis severity.     

Exercise-induced thallium-201 myocardial perfusion defects in angina pectoris without significant coronary artery stenosis

We performed exercise thallium-201 myocardial scintigraphy in 32 patients with angina pectoris to study the incidence of perfusion defects, who had no significant organic stenosis on coronary angiography. None of them had myocardial infarction or cardiomyopathy. Thallium-201 myocardial scintigraphy and 12-lead ECG recording were performed during supine bicycle ergometer exercise. Perfusion defects in thallium-201 scintigrams in SPECT images were assessed during visual analysis by two observers. In the coronary angiograms obtained during intravenous infusion of nitroglycerin, the luminal diameter of 75% stenosis or less in the AHA classification was regarded as an insignificant organic stenosis. Myocardial perfusion defects in the thallium-201 scintigrams were detected in eight (25%) of the 32 patients. Six of these eight patients had variant angina documented during spontaneous attacks with ST elevations in standard 12-lead ECGs. Perfusion defects were demonstrated at the inferior or inferoposterior regions in six patients, one of whom had concomitant anteroseptal defect. The defects were not always accompanied by chest pain. All but one patient demonstrating inferior or inferoposterior defects showed ST depression in leads II, III and aVF on their ECGs, corresponding to inferior wall ischemia. The exception was a case with right bundle branch block. Thus, 25% of the patients with angina pectoris, who had no evidence of significant organic stenosis on their coronary angiograms, exhibited exercise-induced perfusion defects in their thallium-201 scintigrams. Coronary spasms might have caused myocardial ischemia in these patients.     

Detection of coronary artery disease using real-time myocardial contrast echocardiography: a comparison with dual-isotope resting thallium-201/stress technectium-99m sestamibi single-photon emission computed tomography

Real-time myocardial contrast echocardiography (MCE) has the potential to evaluate myocardial perfusion and wall motion (WM) simultaneously. The purposes of this study were to correlate the diagnostic value of MCE with radionuclide single-photon emission computed tomography (SPECT), and to assess the sensitivity and specificity of real-time MCE in detecting coronary artery disease (CAD). Seventy patients with clinically suspected CAD underwent MCE and SPECT at baseline and after dipyridamole infusion. Segmental perfusion with MCE using low mechanical index after 0.3–0.4-ml bolus injections of perfluorocarbon exposed sonicated dextrose albumin solution was performed. All patients had a dual-isotope (rest thallium-201, stress sestamibi) study performed both at baseline and after dipyridamole infusion, and 40 patients had subsequent quantitative coronary angiography. Abnormalities were noted in 27 patients (38.6%) by MCE, in 29 patients (41.4%) by WM analysis, and in 30 patients (42.9%) by SPECT imaging. When MCE and WM analysis were combined, the agreement with SPECT imaging improved from 75.7% (Kappa = 0.50) to 82.0% (Kappa = 0.62). In 40 patients (120 territories) who underwent coronary angiography, good perfusion concordance was achieved for the left anterior descending and left circumflex arteries, and was fair for the right coronary arteries. Compared with quantitative angiography, there was no difference in sensitivity, specificity, and accuracy in detecting significant CAD among the three modalities. The combination of MCE and WM had a better sensitivity (84%), specificity (93.3%), and accuracy (87.5%) than the MCE and WM analysis alone. However, the difference did not reach statistical significance. Real-time MCE has a good agreement with SPECT imaging for detecting CAD. The combination of MCE and WM appears to have higher sensitivity, specificity, and accuracy in detecting CAD than either technique alone.     

Correlation between thallium-201 myocardial perfusion defects and the functional severity of coronary artery stenosis as assessed by pressure-derived myocardial fractional flow reserve.

Although a relationship between the coronary pressure-derived fractional flow reserve (FFR) and the presence of myocardial ischemia as demonstrated by radionuclide imaging has been reported in a select group of patients, it remains to be established whether this relation also holds true in actual clinical settings with a heterogeneous group of patients. Accordingly, 194 coronary vessels and their supply territories were evaluated in 165 consecutive patients with suspected or known coronary artery disease. An FFR <0.75, which is regarded as indicative of functionally important stenosis, showed a significant correlation with the redistribution of (201)Tl (p<0.0001), with a sensitivity of 79% and specificity of 73%. In 70 infarct-related coronary arteries, the sensitivity and specificity were 79% and 75%, respectively, whereas in the 124 remaining vessels that were not related to the myocardial infarct, the sensitivity and specificity were 80% and 72%, respectively. In addition, the FFR exhibited a significant inverse correlation with the (201)Tl reversibility score (r=-0.62; p<0.0001). These results suggest that the FFR has a significant relationship with scintigraphic evidence of myocardial ischemia and can be regarded as a marker of its presence or absence in patients in actual clinical settings.     

Comparison of real-time coherent contrast imaging to dipyridamole thallium-201 single-photon emission computed tomography for assessment of myocardial perfusion and left ventricular wall motion

Real-time coherent contrast imaging (CCI) echocardiography has the ability to evaluate wall motion and myocardial perfusion simultaneously, but its clinical applicability in the diagnosis of coronary artery disease (CAD) remains to be determined. This study examines the level of agreement between real-time CCI echocardiography and thallium-201 single-photon emission computed tomography (SPECT) following stress vasodilation. Forty-two patients with known or suspected CAD underwent real-time CCI using octafluoropropane-filled microspheres infusion before and after dipyridamole and thallium-201 injections. The apical 4- and 2-chamber views were each divided into 6 segments to assess wall motion and perfusion. Real-time CCI and SPECT were interpreted independently. Thirty-eight patients successfully completed tests, and 4 had suboptimal contrast images. Each vascular territory was classified as normal or abnormal by CCI perfusion, wall motion, and SPECT at baseline and at stress. Of the 114 territories (3 in each of the 38 patients), 3 (3.5%) were not analyzed; however, all territories corresponding to the left anterior descending artery were suitable for analysis. Concordance between CCI echocardiography and thallium-201 SPECT perfusion for left anterior descending, left circumflex, and right coronary artery territories were 91%, 86%, and 69%, respectively; between CCI perfusion and wall motion, the correlations were 93%, 93%, and 91%, respectively. When CCI perfusion and wall motion analysis were combined, their concordance to thallium-201 SPECT uptake improved to 94%, 89%, and 79%, respectively. In conclusion, real-time CCI echocardiography agrees very closely with thallium-201 SPECT in assessing myocardial perfusion following vasodilatory stress. Assessment of myocardial perfusion, in addition to segmental wall motion analysis, during stress echocardiography may be a significant contribution to the noninvasive evaluation of patients with ischemic heart disease.     

Detection and quantification of coronary stenosis severity with myocardial contrast echocardiography

The development of microbubble contrast agents and new imaging modalities now allows the assessment of myocardial perfusion during echocardiography. These microbubbles are excellent tracers of red blood cell kinetics. Apart from providing a spatial assessment of myocardial perfusion, myocardial contrast echocardiography (MCE) can also be used to quantify the 2 specific components of myocardial blood flow-flow velocity and myocardial blood volume. The method to quantify myocardial blood flow velocity is based on rapid destruction of microbubbles by ultrasound, and subsequent assessment of the rate of replenishment of microbubbles into the myocardial microcirculation within the ultrasound beam elevation. Assessment of steady state myocardial video intensity (VI) provides a measure of myocardial or capillary blood volume. Perfusion defects that develop distal to a stenosis during hyperemia are therefore due to capillary derecruitment. We have shown that the degree of derecruitment (and therefore the severity of a perfusion defect) is proportional to stenosis severity. Because the capillary bed also provides the greatest resistance to hyperemic flow, decreases in capillary blood volume distal to a stenosis during hyperemia result in increases in microvascular resistance, which is the mechanism underlying the progressive decrease in flow reserve in the presence of a stenosis. Consequently, both the severity of a perfusion defect and quantification of abnormal myocardial blood flow reserve on MCE can be used to determine stenosis severity. As imaging methods with MCE continue to be refined, the optimal imaging algorithms for clinical practice still need to be determined. MCE, however, holds promise as a noninvasive, instantaneous, on-line method for the detection and quantification of coronary artery disease.     

Coronary vasospasm produces reversible perfusion defects observed during adenosine triphosphate stress myocardial single-photon emission computed tomography

BACKGROUND: Adenosine triphosphate stress thallium-201 single-photon emission computed tomography (ATP-SPECT) is useful for diagnosing coronary artery disease (CAD), although sometimes false positive results are observed. It has not been established whether a coronary spasm is responsible for the false positive findings during ATP-SPECT. HYPOTHESIS: We investigated whether coronary spasm is one of the factors which produces reversible defects on ATP-SPECT. METHODS: Eighty-six patients (mean age: 62 y; 58 men) who underwent both spasm-provocation testing by coronary angiography and ATP-SPECT, were selected for the study. Patients with coronary narrowing (>30%), myocardial infarction, or heart failure were excluded. Patients were divided into 2 groups based on whether the spasm-provocation test result was positive (vasospastic angina [VSA] group, n = 46) or negative (non-VSA group, n = 39). RESULTS: The body mass index was lower in the VSA group than in the non-VSA group (p = 0.005). On ATP-SPECT imaging, any type of reversible defect was observed more frequently in the VSA group (68%) than in the non-VSA group (36%, p = 0.0027). Logistic regression analysis demonstrated that the presence of reversible defects was one of the factors accounting for the presence of coronary vasospasm (p = 0.0022, R2 = 0.172). CONCLUSIONS: The findings suggest that reversible defects on ATP-SPECT imaging are frequently present in patients with coronary vasospasm. Coronary spasm may be considered as 1 of the factors, which produce reversible defects on ATP-SPECT, observed in patients with chest symptoms and angiographically normal coronary arteries.     

Analysis of thallium-201 single-photon emission computed tomography after intravenous dipyridamole using different quantitative measures of coronary stenosis severity and receiver operator characteristic curves.

The presence of significant coronary artery disease in individual vessels was assessed using thallium-201 single-photon emission computed tomography (SPECT) after intravenous dipyridamole. Coronary angiograms were analyzed using quantitative computer-assisted techniques in 81 men patients. Eleven men with a less than 3% probability of coronary artery disease were used as a control population. Three definitions of a hemodynamically significant coronary stenosis were studied independently: (1) a greater than 50% luminal diameter narrowing; (2) an absolute cross-sectional area less than or equal to 2.0 mm2; or (3) a greater than or equal to 70% cross-sectional area obstruction. Myocardial perfusion after dipyridamole was analyzed using the quantitative (polar map) method in 213 regions from the group with known coronary anatomy and using 33 regions from the group with a low likelihood of disease. Receiver operating characteristic curves were used to define the best cut-off point for the discrimination between normal and abnormal perfusion. When related to each of the three quantitative angiographic criteria, the optimum balance between sensitivity and specificity occurred at a defect size of greater than or equal to 8% for the left anterior descending artery, greater than or equal to 4% for the circumflex artery, and greater than 0% for the right coronary artery. Using a luminal diameter narrowing of greater than 50% to define the presence of significant coronary artery disease, these corresponded to respective sensitivities and specificities of 0.82 and 0.76 for the left anterior descending artery, 0.71 and 0.71 for the circumflex artery, and 0.76 and 0.82 for the right coronary artery. Thus analysis of receiver operator characteristic curves provides a means to define abnormalities for the SPECT polar map program after dipyridamole stress. Different definitions of coronary stenosis significance as determined by quantitative angiography did not substantially alter the results of the thallium imaging data and thus suggest that these definitions are functionally similar.     

Assessment of coronary artery disease using single-photon emission computed tomography with thallium-201 during adenosine-induced coronary hyperemia

Thallium-201 myocardial imaging during dipyridamole-induced coronary hyperemia has been an accepted method for diagnosing coronary artery disease (CAD) and risk stratification. Adenosine is a powerful short-acting coronary vasodilator. Initial results of thallium imaging during adenosine infusion have been encouraging. In 132 patients with CAD and in 16 patients with normal coronary angiograms, adenosine was given intravenously at a dose of 0.14 mg/kg/min for 6 minutes and thallium-201 was injected at 3 minutes. The thallium images using single-photon emission computed tomography were abnormal in 47 of the 54 patients (87%) with 1-vessel, in 34 of 37 patients (92%) with 2-vessel and in 40 of 41 patients (98%) with 3-vessel CAD. The sensitivity was 92% in the 132 patients with CAD (95% confidence intervals, 86 to 96%). In patients with normal coronary angiograms, 14 of 16 patients had normal thallium images (specificity, 88%; 95% confidence intervals, 59 to 100%). The results were very similar when subgroups of patients were analyzed: those without prior myocardial infarction, elderly patients and women. The nature of the perfusion defects (fixed or reversible) was assessed in relation to whether the 4-hour delayed images were obtained with or without the reinjection technique. In patients who underwent conventional delayed imaging, there were more fixed perfusion defects than in patients with reinjection delayed imaging (16 vs 0%, p less than 0.0001). The adverse effects were mild, transient and well tolerated. Thus, adenosine thallium tomographic imaging provides a high degree of accuracy in the diagnosis of CAD. The use of the reinjection technique enhances the ability to detect reversible defects.     

Incremental prognostic value of exercise thallium-201 myocardial single-photon emission computed tomography late after coronary artery bypass surgery

Objectives.This study assessed the incremental prognostic value of exercise thallium-201 myocardial perfusion single-photon emission computed tomography (SPECT) performed ≥5 years after coronary artery bypass surgery.Background.Thallium-201 scintigraphy has shown significant prognostic value in a variety of populations with suspected and known coronary artery disease. However, its value in patients with previous bypass surgery remains unknown.Methods.We studied 294 patients who were prospectively followed up. Cox proportional hazards models for prediction of “hard” events (cardiac death and nonfatal infarctions) were constructed, with variables considered for inclusion in hierarchic order: clinical and exercise data first, followed by scintigraphic information.Results.Mean (± SD) follow-up duration after scintigraphy was 31 ± 11 months. There were 20 cardiac deaths and 21 monfatal acute myocardial infarctions. Twenty-nine patients had late (>60) days after thallium-201 SPECT) revascularization procedures or underwent repeat bypass surgery or percutaneous transluminal angioplasty. Shortness of breath and peak exercise heart rate were the most important clinical predictors of hard events. Two scintigraphic variables added significant prognostic information to the clinical model: the thallium-201 summed reversibility score (summation of segmental differences between stress and redistribution scores) and the presence of increased lung uptake of the radiotracer. The global chi-square statistic for this model was twice as high as that for the clinical/exercise model alone (49.7 vs. 24.2). When a second multivariate Cox model was build adding “soft” events (i.e., late revascularization procedures) as outcomes of interest, the summed reversibility score was selected as an independent scintigraphic predictor of events. The global chi-square statistic for this model was 50.7, three times as high as that for the clinical/exercise model alone.Conclusions.After evaluation of treadmill and exercise data, thallium-201 myocardial perfusion SPECT provided incremental prognostic information in patients late after bypass.     

Myocardial contrast echocardiography for the detection of coronary artery stenosis: a prospective multicenter study in comparison with single-photon emission computed tomography.

OBJECTIVES: The purpose of this study was to compare myocardial contrast echocardiography (MCE) with single-photon emission computed tomography (SPECT) for the detection of significant coronary artery disease (CAD) in patients with symptoms suggestive of CAD. BACKGROUND: Single-photon emission computed tomography is a well-established method of assessing patients with CAD. Myocardial contrast echocardiography is a new technique allowing bedside assessment of myocardial perfusion. We hypothesized that MCE was comparable to SPECT in the assessment of patients with known or suspected CAD. METHODS: A total of 123 patients scheduled for coronary angiography underwent intermediate (mechanical index 0.5) triggered replenishment MCE and SPECT imaging at rest and after vasodilator stress. Coronary angiography was performed within four weeks of stress imaging. RESULTS: In total, 96 of 123 (78%) patients demonstrated CAD (stenosis >/=50%). There was no difference in the sensitivity of MCE compared with SPECT in the detection of CAD (84% vs. 82%; p = NS), and both demonstrated similar specificity (56% vs. 52%, respectively). In patients with multivessel disease, MCE and SPECT also demonstrated similar sensitivity (91% and 88%, respectively) for the detection of CAD. Agreement between MCE and SPECT for the presence or absence of CAD was 73%. CONCLUSIONS: Myocardial contrast echocardiography is comparable to SPECT in the detection of CAD not only on a patient basis but also in the localization of disease by vascular territory in a relatively high-risk population.     

Improved detection of myocardial infarction by emission computed tomography with thallium-201. Relation to infarct size.

Emission computed tomography with thallium-201 was compared with planar imaging in its ability to detect myocardial infarctions of various sizes four weeks after the onset. Tomography was performed after planar imaging at rest in 160 patients with a first myocardial infarction, in whom infarct size was prospectively estimated by the peak value of creatine kinase activity at the time of the acute episode and in 39 patients without infarction. The planar images and the transaxial, short axial, and long axial tomograms were interpreted qualitatively. Tomography was significantly more sensitive than planar imaging in detecting anterior (87% v 96%), inferior (73% v 97%), and non-transmural (47% v 87%) infarcts. The increased sensitivity was confined to detecting small infarcts as assessed by the peak creatine kinase value (44% v 89% when peak creatine kinase activity was less than or equal to 1000 IU/l). The overall sensitivity was 96% for tomography and 78% for planar imaging. The specificity was similar (92%) with the two techniques. Thus emission computed tomography can improve the detection rate of small infarcts that cannot be identified on planar images, by showing the three dimensional distribution of thallium-201, and increases the diagnostic value of thallium-201 scintigraphy.     

Physiologic assessment of left anterior descending coronary artery stenosis by quantitative intravenous myocardial contrast echocardiography in humans: comparison with exercise single-photon emission computed tomography

OBJECTIVE: To clarify the potential of quantitative intravenous myocardial contrast echocardiography (MCE) for physiologic assessment of the left anterior descending artery (LAD) stenosis. METHODS: We studied 38 patients with suspected coronary artery disease. MCE was performed by continuous infusion of Levovist and intermittent ultrasonic exposure. Images were obtained from the apical four-chamber view at rest and after dipyridamole infusion. The background-subtracted intensity versus pulsing interval plots were fitted to an exponential function,Y=A(1 e-ss), to obtain the plateau level (A) and rate of rise (ss) of background-subtracted intensity both at rest and after dipyridamole infusion. We compared the results with those of exercise thallium-201 single-photon emission computed tomography (SPECT). RESULTS: Of the 38 patients, 18 patients exhibited redistribution in the LAD territories with SPECT (group A), although 20 did not (group B). The ss reserve (DIP/rest) in group A was significantly lower than those in group B (0.8 +/- 0.5 versus 2.0 +/- 1.1, P < 0.001), while the A reserve did not differ between the two groups (1.2 +/- 0.6 versus 1.0 +/- 0.5, P = NS). The ss reserve <1.1, which was the optimal cutoff value, provided sensitivity of 79% and specificity of 84% for the presence of redistribution in SPECT. CONCLUSIONS: Quantitative intravenous MCE allows us to estimate physiologic severity of the LAD stenosis in the clinical setting.     

Localization of coronary artery disease with exercise electrocardiography: correlation with thallium-201 myocardial perfusion scanning

In 61 patients with single vessel coronary artery disease (70 percent or greater obstruction of luminal diameter in only one vessel) and no previous myocardial infarction, the sites of ischemic changes on 12 lead exercise electrocardiography and on thallium-201 myocardial perfusion scanning were related to the obstructed coronary artery. The site of exercise-induced S-T segment depression did not identify which coronary artery was obstructed. In the 37 patients with left anterior descending coronary artery disease S-T depression was most often seen in the inferior leads and leads V₄ to V₆, and in the 18 patients with right coronary artery disease and in the 6 patients with left circumflex artery disease S-T depression was most often seen in leads V₅ and V₆. Although S-T segment elevation was uncommon in most leads, it occurred in lead V₁ or aVL, or both, in 51 percent of the patients with left anterior descending coronary artery disease. A reversible anterior defect on exercise thallium scanning correlated with left anterior descending coronary artery disease (probability [p] < 0.0001) and a reversible inferior thallium defect correlated with right coronary or left circumflex artery disease (p < 0.0001).In patients with single vessel disease, the site of S-T segment depression does not identify the obstructed coronary artery; S-T segment elevation in lead V₁ or aVL, or both, identifies left anterior descending coronary artery disease; and the site of reversible perfusion defect on thallium scanning identifies the site of myocardial ischemia and the obstructed coronary artery.     

Quantitative assessment of harmonic power Doppler myocardial perfusion imaging with intravenous Levovist in patients with myocardial infarction: comparison with myocardial viability evaluated by thallium-201 single-photon emission computed tomography and coronary flow reserve.

BACKGROUND: Intravenous myocardial contrast echocardiography with harmonic power Doppler imaging is a novel technique for assessing myocardial perfusion. AIMS: The aim of this study was to quantitatively assess myocardial perfusion by harmonic power Doppler imaging in patients with a previous myocardial infarction and compare myocardial contrast echocardiography results with myocardial viability evaluated by thallium-201 single-photon emission computed tomography ((201)Tl-SPECT) and the results of Doppler flow measurement of coronary flow velocity reserve. METHODS: Twenty-three patients with anterior myocardial infarction who were scheduled for adenosine stress (201)Tl-SPECT underwent myocardial contrast echocardiography with harmonic power Doppler imaging. Harmonic power Doppler imaging was performed at rest and during adenosine infusion (0.15 mg/kg/min) using an intravenous infusion of Levovist. The peak colour pixel intensity ratios of the risk area to the control area were used for quantitative analysis of myocardial perfusion by harmonic power Doppler imaging. Coronary blood flow velocity was measured using Doppler-tipped guidewire in the distal portion of left anterior descending artery and coronary flow velocity reserve was calculated. RESULTS: In patients with myocardial viability assessed by (201)Tl-SPECT, pixel intensity ratios both at rest and during hyperaemia were significantly higher compared with those in patients without myocardial viability (at rest: 0.62 +/- 0.28 vs 0.37 +/- 0.17, P=0.038, during hyperaemia 0.72 +/- 0.19 vs 0.40 +/- 0.18, P=0.003). Coronary flow velocity reserve was significantly different between two groups (2.35 +/- 0.43 vs 1.49 +/- 0.53, P <0.01). CONCLUSIONS: Quantitative assessment of microvascular integrity by harmonic power Doppler imaging corresponds to the evaluation of the microcirculation by coronary flow velocity reserve.     

Transaxial tomography in the study of myocardial perfusion with thallium-201

Stress and redistribution thallium-201 myocardial imaging using a transaxial single emission computed tomographic system has been applied to the diagnosis of coronary artery disease. Data sampling was performed along a limited 180 degree arc, obtaining 32 images in a continuous mode, at a rate of 20 seconds per image. The production of perfusion defects in patients was stimulated by exercise testing or by dipyridamole infusion. No significant differences existed when both tests were compared (p less than 0.01). Normal and abnormal patterns including the different pathophysiological alterations of myocardial ischemia were defined in three tomographic planes using this methodology. Patients with coronary disease are separated from patients without coronary disease with high probability (84%). Transaxial SPECT (single photon emission computerized tomography) provides a significant increment in sensitivity and specificity in relation to planar scintigraphy in the detection of myocardial infarction (91 and 100%, respectively); residual ischemia postinfarction (96 and 97%, respectively), and significant coronary artery disease (91 and 97%, respectively).     

铊^201单光子发射计算机断层心肌显像对隐匿性冠心病预后判断的价值

目的探讨心肌潘生丁负荷／再分布铊（T1）^201单光子发射计算机断层显像（single photon emission computed tomography，SPECT）法评价隐匿性冠心病预后的可行性。方法入选1998至2005年期间94例无任何症状但运动平板试验反复阳性的飞行人员，根据SPECT心肌显像结果分为检查结果阳性组及阴性组，阳性组中根据心肌缺血累及范围又分为单个节段受累亚组、2个节段受累亚组和2个以上节段受累亚组，平均随访4．5年，比较组间的主要心血管事件（major adverse cardiovascular events，MACE）发生率。结果随访过程中，阳性组与阴性组的MACE分别为30％与7％，差异具有统计学意义（P〈0．01）。2个以上节段受累亚组组MACE发生率（100％）明显高于单个节段受累亚组（24％）、2个节段受累亚组（22％）及阴性组（7％），P均〈0．05。结论潘生丁负荷心肌T1^201-SPECT显像有助于隐匿性冠心病预后判断，从而指导临床早期干预治疗。