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Unlabelled: The availability of gated SPECT has increased the interest in the determination of volume and ejection fraction of the left ventricle (LV) for clinical diagnosis. However, the same indices for the right ventricle (RV) have been neglected. The objective of this investigation was to use a mathematical model of the anatomical distribution of activity in gated blood-pool imaging to evaluate the accuracy of two ventricular volume and ejection fraction determination methods. In this investigation, measurements from the RV were emphasized., Methods: The mathematical cardiac torso phantom, developed to study LV myocardium perfusion, was modified to simulate the radioactivity distribution of a 99mTc-gated blood-pool study. Twenty mathematical cardiac torso phantom models of the normal heart with different LV volumes (122.3 +/- 11.0 ml), RV volumes (174.6 +/- 22.3 ml) and stroke volumes (75.7 +/- 3.3 ml) were randomly generated to simulate variations among patients. An analytical three-dimensional projector with attenuation and system response was used to generate SPECT projection sets, after which noise was added. The projections were simulated for 128 equidistant views in a 360 degrees rotation mode., Results: The radius of rotation was varied between 24 and 28 cm to mimic such variation in patient acquisitions. The 180 degrees and 360 degrees projection sets were reconstructed using the filtered backprojection reconstruction algorithm with Butter-worth filtering. Comparison was made with and without application of the iterative Chang attenuation correction algorithm. Volumes were calculated using a modified threshold and edge detection method (hybrid threshold), as well as a count-based method. A simple background correction procedure was used with both methods., Conclusion: Results indicate that cardiac functional parameters can be measured with reasonable accuracy using both methods. However, the count-based method had a larger bias than the hybrid threshold method when RV parameters were determined for 180 degrees reconstruction without attenuation correction. This bias improved after attenuation correction. The count-based method also tended to overestimate the end systolic volume slightly. An improved background correction could possibly alleviate this bias.

Background: Coronary angiography may not reliably predict whether a stenosis causes exercise-induced ischemia. Intracoronary Doppler ultrasound may enhance diagnostic accuracy by providing a physiological assessment of stenosis severity. The goal of this study was to compare intracoronary Doppler ultrasound with both 201Tl imaging and coronary angiography., Methods and Results: Fifty-five patients with 67 stenotic coronary arteries underwent coronary angiography with intracoronary Doppler ultrasound and had exercise 201Tl testing within a 1-week period. Coronary flow reserve was measured, and analyses were performed by independent core laboratories. The mean stenosis was 59+/-12%; 51 of 67 stenoses were intermediate in severity (40% to 70%). A coronary flow reserve < 1.7 predicted the presence of a stress 201Tl defect in 56 of 67 stenoses (agreement=84%; kappa=0.67; 95% CI=0.48 to 0.86). In the patients who achieved 75% of their predicted maximum heart rate, the Doppler and 201Tl imaging data agreed in 46 of 52 stenoses (agreement=88%; kappa=0.77; 95%CI=0.57 to 0.97). Scatter was evident when angiography was compared with coronary flow reserve (r=.43), and the angiogram did not reliably predict the results of the 201Tl stress test (kappa=0.21; agreement=57% to 63%)., Conclusions: Doppler-derived coronary flow reserve accurately predicts the presence of exercise-induced ischemia on stress 201Tl imaging, and coronary angiography does not reliably assess the physiological significance of an intermediate coronary stenosis.

We hypothesized that left ventricular (LV) cavity size measured on dipyridamole thallium scintigraphy identifies patients at risk for late nonfatal myocardial infarction and cardiovascular death. Accordingly, we retrospectively evaluated the predictive value of clinical and scintigraphic variables, including transendocardial LV cavity measurement performed on formatted images, in 335 vascular surgery patients. A nonhomogeneous perfusion pattern and enlarged LV cavity size were the most significant predictors of late events, and the interaction between these two variables was more predictive than was either variable alone. Life-table analysis demonstrated that patients with normal perfusion patterns had the lowest incidence of late events regardless of cavity size (p < 0.0005). Conversely, patients with a nonhomogeneous perfusion pattern and the largest LV cavity measurements were at the highest risk for late cardiac events (p < 0.0001). Therefore, this study demonstrated that a measurement of LV scintigraphic cavity size can provide important risk stratification for late cardiac events.

By combining conjugate views, truncation-free attenuation profiles of patients can be obtained by using slant hole collimators on three-headed SPECT systems. The alterations in reconstruction algorithms necessary for use with slant hole collimators and potential image artifacts are discussed. Based on an evaluation of the size of objects that can be imaged without truncation and the size of the overlap region in the conjugate views, a 15 degrees slant angle was determined to be optimal. Studies with a 30 degrees slant hole collimator verified the ability of slant hole transmission imaging to provide accurate, truncation-free attenuation maps of a 56 cm lateral width phantom. The center of rotation was determined to be dependent on the slant angle and radius of rotation of the slant collimator. These studies also demonstrated that the spatial resolution in the transaxial plane of the attenuation maps depends on radius of rotation of the slant hole collimator, but does not depend on the radius of rotation of an uncollimated transmission source. A multiline transmission source was investigated for use with estimating the attenuation map in Tc-99m labeled sestamibi perfusion imaging.

Objectives: This study sought to evaluate the efficacy and safety of arbutamine when used in conjunction with thallium-201 single-photon emission computed tomography (SPECT) in a multicenter trial and to compare arbutamine stress and treadmill exercise thallium-201 SPECT for diagnostic sensitivity and myocardial perfusion pattern., Background: Arbutamine is a potent beta-agonist developed specifically for pharmacologic stress testing., Methods: Arbutamine was administered by a novel computerized closed-loop device that measures heart rate and adjusts arbutamine infusion to achieve a selected rate of heart rate increase toward a predetermined limit. The cohort included 184 patients who underwent arbutamine stress testing, of whom 122 (catheterization group) had angiographically defined coronary artery disease ( > or = 50% diameter stenosis of a major coronary artery), and 62 had a low pretest likelihood of coronary artery disease (low likelihood group). A subset of 69 patients from the catheterization group underwent both arbutamine and exercise stress testing., Results: Hemodynamic responses during arbutamine and exercise stress testing demonstrated no significant difference in percent increase in heart rate (81% vs. 76%) or systolic blood pressure (26% vs. 30%). The sensitivity for detecting coronary artery disease ( > or = 50% stenosis) using arbutamine thallium-201 SPECT was 87% (95% for detecting > or = 70% stenoses), and the normalcy rate in the low likelihood group was 90%. In patients completing both arbutamine and exercise stress testing, thallium-201 SPECT sensitivity for detecting coronary artery disease ( > or = 50% stenosis) was 94% and 97% (p = NS), respectively Furthermore, SPECT segmental visual score agreement (defect vs. no defect) showed a concordance of 92% between arbutamine and exercise results (kappa 0.80, p < 0.001). The stress thallium-201 SPECT segmental scores showed 83% exact agreement (kappa 0.69, p < 0.001), and analysis of the reversibility of segments with stress perfusion defects demonstrated 86% exact agreement (kappa 0.68, p < 0.001). In general, side effects associated with arbutamine were well tolerated and resolved with discontinuation of infusion., Conclusions: Arbutamine, administered by a closed-loop feed-back system was shown to be a safe and effective pharmacologic stress agent. Arbutamine stress thallium-201 SPECT appears to be accurate for the diagnosis of coronary artery disease with a diagnostic efficacy similar to that of treadmill exercise thallium-201 studies.

Objectives: This study attempted 1) to assess the utility of rest measurements of intracoronary blood flow velocity for the physiologic assessment of coronary stenoses before and after right coronary artery angioplasty, and 2) to compare the phasic flow pattern in the right coronary artery proper with the phasic flow pattern in its major branches to the left ventricle., Background: Previous investigations have demonstrated that a reduction in distal blood flow velocity and a loss of distal diastolic predominant flow are characteristic of physiologically significant stenoses and that these indexes normalize after successful coronary artery dilation. However, these studies were predominantly performed in the left coronary artery. The utility of monitoring rest velocity variables during angioplasty of the right coronary artery has not been studied., Methods: We studied 20 patients undergoing angioplasty of the right coronary artery with use of a Doppler angioplasty guide wire., Results: Values were expressed as the mean value +/- 1 SD. The rest average peak velocity did not decrease distal to angiographically significant right coronary artery stenoses (23.3 +/- 9.4 cm/s proximal vs. 20.2 +/- 11.1 cm/s distal, p = 0.20). The proximal/distal velocity ratio was 1.4 +/- 0.9 before angioplasty and did not significantly decrease after angioplasty (p = 0.58). This study had a 99.4% power to detect a difference between proximal and distal average peak velocity. There was no relation between percent diameter stenosis and proximal/distal velocity ratios (r = 0.15, p = 0.55). Diastolic predominant flow was not observed in the proximal or distal right coronary artery. However, after angioplasty, diastolic predominant flow was observed in the posterolateral and posterior descending coronary arteries., Conclusions: Rest phasic Doppler flow velocity indexes are not useful for evaluating stenoses in the right coronary artery proper before or after angioplasty. In contrast to the right coronary artery proper, diastolic predominant flow is observed in the posterior descending and posterolateral coronary arteries. The utility of measuring hyperemic Doppler flow velocity indexes, such as distal coronary flow reserve, for assessing right coronary artery stenoses merits further investigation.

Nine Yorkshire pigs underwent coronary artery occlusion followed by 2 hours of reperfusion. In five pigs (group A) the occlusion time was 15 minutes and in four pigs (group B) the occlusion time was 1 hour. Teboroxime was administered and images were acquired at baseline, and following occlusion and reperfusion. Infarct size was determined by triphenyl tetrazolium staining. Normalized regional myocardial blood flow, as determined by radio-labeled microspheres, was 0.26 +/- 0.09 following occlusion and 0.83 +/- 0.07 following reperfusion (p < 0.01). Significant differences were found between the defect/normal scan ratios on the baseline and occlusion scans (1.0 +/- 0.03 vs 0.54 +/- 0.10; p < 0.01) and between the occlusion and reperfusion scans (0.54 +/- 0.10 vs 0.97 +/- 0.17; p < 0.01). This is the first study to demonstrate that rapid sequential teboroxime imaging can detect acute coronary occlusion and reperfusion to both ischemic and infarcted myocardium. Teboroxime may be an excellent tracer for the early evaluation of infarct artery patency in patients receiving thrombolytic therapy.

Adenosine thallium stress testing has a demonstrated utility in the detection of coronary artery disease. The optimal dose for diagnostic efficacy with minimal side effects has not been critically evaluated. A randomized 3- and 6-minute infusion of adenosine (140 micrograms/kg/min) was performed in 11 subjects. Subjects reported more side effects during the 6-minute infusion protocol (p < 0.05). Hemodynamic changes were not different during either infusion duration. All dysrhythmias began within 2 minutes and therefore the duration of the infusion did not influence their occurrence. Segmental comparison of the stress images demonstrated an 89% agreement. Delayed scans demonstrated a 79% agreement. There was a higher incidence of redistribution following the 6-minute infusion (p = 0.014). We conclude that when side effects necessitate the discontinuation of a 6-minute adenosine infusion, a diagnostic test can still be achieved if 2 to 3 minutes of adenosine have been administered before the thallium injection; however, the amount of viable myocardium may be underestimated.

Objectives: We sought to assess whether sequential teboroxime imaging can rapidly evaluate vessel patency and identify the coronary artery occluded in patients undergoing balloon occlusion of a coronary artery., Background: Intravenous thrombolytic therapy results in successful reperfusion of the infarct-related artery in only 50% to 80% of cases. A noninvasive technique to serially evaluate coronary perfusion would identify patients who might benefit from other interventions such as emergency percutaneous transluminal coronary angioplasty, coronary artery bypass grafting or increased intensity of thrombolytic therapy., Methods: Teboroxime scans were performed during balloon occlusion in 15 nonconsecutive patients undergoing angioplasty of a major coronary artery. Equivalent views were repeated after successful angioplasty., Results: The mean time between balloon occlusion and reperfusion imaging was 1.6 +/- 0.6 h. The mean number of defects decreased significantly from 4.13 +/- 1.01 during balloon occlusion to 0.27 +/- 0.44 after reperfusion (p = 0.0006). There was a 30% decrease in the defect/normal zone count/pixel ratios during balloon occlusion and normalization of these ratios after reperfusion (p = 0.0006). The scans correctly identified all nine left anterior descending coronary artery occlusions and both right coronary artery occlusions. One of the four left circumflex coronary artery occlusions was incorrectly identified as a right coronary artery occlusion by scan criteria. Overall, the scans correctly identified the occluded artery 93% of the time (kappa = 0.88). The scan was 100% accurate for distinguishing occlusion of the left anterior descending coronary artery (n = 9) from occlusions of the left circumflex or right coronary artery (n = 6)., Conclusions: We believe that this is the first clinical study to demonstrate that sequential planar imaging with teboroxime can 1) rapidly detect acute coronary artery occlusion and reperfusion, and 2) identify the occluded coronary artery. A trial comparing rapid sequential teboroxime imaging with coronary angiography in patients receiving thrombolytic therapy for acute myocardial infarction is warranted.

"After summarizing the major features of the ASEAN labor market and patterns of labor migration in Asia, the article describes the origins and current status of the ASEAN Free Trade Area (AFTA) and its main mechanism, the Common Effective Preferential Tariff (CEPT) Scheme." Possible trends in the migration of skilled and professional Philippine workers throughout the Asia-Pacific region are discussed., (excerpt)