Assessing coronary artery disease with dipyridamole technetium-99m-tetrofosmin SPECT: a multicenter trial.

UNLABELLED: Exercise 99mTc-tetrofosmin myocardial scintigraphy is as accurate as exercise 201TI imaging. Thus far, no data are available on tetrofosmin imaging during pharmacologic stress. We evaluated the feasibility of using. 99mTc-tetrofosmin myocardial SPECT during vasodilation with dipyridamole for detecting coronary artery disease. METHODS: Sixty-four patients, enrolled in three centers in the U.S., underwent one-day dipyridamole/rest tetrofosmin SPECT. Coronary angiography, performed in 59 patients within 2 mo of the SPECT study, revealed normal coronary arteries or insignificant coronary stenosis in 11 patients and significant (> or = 50% luminal diameter stenosis) coronary stenoses in 48 patients. RESULTS: Sensitivity and specificity of tetrofosmin SPECT for detecting coronary artery disease were 85% and 55%, respectively, in the overall population and 81% and 55% in patients without prior coronary artery bypass surgery. The overall sensitivity and specificity of tetrofosmin tomographic imaging for detection of individual coronary stenoses were 53% and 72%, respectively, in the overall population and 54% and 80% in the patients without prior coronary artery bypass surgery. CONCLUSION: One-day dipyridamole/rest 99mTc-tetrofosmin myocardial perfusion imaging is feasible and has a high sensitivity for detection of coronary artery disease.

Myocardial viability: methods of assessment and clinical relevance.

Myocardial hibernation is hypoperfused dysfunctional myocardium that has the potential to recover function after coronary revascularization. Although recovery of regional function after revascularization is the gold standard for assessing the diagnostic accuracy of various techniques, improvements of EF, symptoms, and survival are fundamental end points. Despite important differences in the markers of viability by positron-emission tomography, single-photon emission tomography, two-dimensional echocardiography, and magnetic resonance imaging, their positive and negative predictive values in nonrandomized studies are fairly comparable. Assessment of myocardial viability may be clinically important in many patients but especially in those with EF < 30% and congestive heart failure. The degree of improvement in EF after coronary revascularization depends on the extent of hibernation, the suitability of coronary structure for revascularization, the lack of perioperative infarction, the completeness of revascularization, and the long-term patency of grafts.

Dynamic planar myocardial perfusion imaging in patients with one-vessel disease with intracoronary injection of technetium 99m teboroxime during papaverine-induced coronary hyperemia.

This study examined the imaging results and kinetics of technetium 99m teboroxime after its intracoronary injection during papaverine-induced coronary hyperemia in patients with one-vessel disease before and after coronary angioplasty. Thirteen patients with > or = 90% diameter stenosis of either the left anterior descending or the left circumflex coronary artery were included. Two patients were excluded because of ventricular tachycardia during papaverine injection in one patient and unsuccessful angioplasty in the second patient. One mCi of technetium 99m teboroxime was injected into the left main coronary artery during coronary hyperemia induced by intracoronary injection of papaverine. Dynamic acquisition in a frame mode (20 sec/frame) was performed for 5 minutes in the left anterior oblique projection with a multicrystal gamma camera before and after successful angioplasty. Ischemic:normal count ratio increased from 0.75 +/- 0.4 before to 1.00 +/- 0.50 after angioplasty (p < 0.1). The T 1/2 of teboroxime was 6.5 +/- 1.5 min in the normal zone and 7.2 +/- 1.9 min in the ischemic zone (p, NS). Perfusion defects were visible in the territory of the stenosed coronary artery in 9 of 11 patients before angioplasty and in 7 of 11 patients after angioplasty. The image quality was excellent in all studies. Thus this study shows that performing dynamic imaging with intracoronary injection of technetium 99m teboroxime is feasible. This technique may be useful to study the impact of angioplasty on coronary flow and tracer kinetics.

Comparison of left ventricular performance in healthy young women and men during exercise.

BACKGROUND: Previous studies show sex-related differences in left ventricular (LV) response to exercise. It is not clear, however, whether these differences are also seen in younger healthy subjects. METHODS AND RESULTS: This study examined the changes in LV performance during dynamic upright exercise in 11 healthy men and 19 healthy young women according to the Bruce protocol and an individualized ramp protocol. There were no significant differences between the two protocols for either men or women in heart rate, blood pressure, LV ejection fraction (EF) (measured by ambulatory nuclear detector), and measured oxygen consumption. The peak oxygen consumption was higher in men than in women (44 +/- 13 vs 36 +/- 9 ml/kg/min; p < 0.05), but the peak heart rate, systolic blood pressure, and EF were similar. The change in EF (from rest to exercise) was 19% +/- 8% in men and 19% +/- 11% in women with the Bruce protocol (difference not significant) and 26% +/- 9% in men and 19% +/- 6% in women with the ramp protocol (difference not significant). At peak exercise, both men and women showed an increase in end-diastolic volume (29% +/- 14% vs 23% +/- 11%; difference not significant) and a decrease in end-systolic volume (41% +/- 15% vs 43% +/- 21%) (difference not significant). The increase in cardiac output during exercise was due to an increase in heart rate and stroke volume in both men and women. At submaximal exercise, however, the decrease in end-systolic volume was less in women than in men (p < 0.05). CONCLUSIONS: There are no sex-related differences in compensatory mechanism during dynamic exercise in healthy subjects. The changes in contractility and LV volume are not affected by the exercise protocol.

Myocardial viability: unresolved issues.

The determination or assessment of myocardial viability has, over the past decade, captured the imagination and interest of many investigators in basic and clinical research using state-of-the-art technologies such as PET, SPECT, MRI and two-dimensional echocardiography (2-DE). The emphasis in these studies has been to determine the absolute and comparative accuracy of these techniques. There are recent studies addressing the evaluation of the effect of viability assessment on patient outcome. The use of biochemical agents and other imaging methods in viability assessment is complex with many unresolved issues to be considered in the design and implementation of clinical protocols and in routine patient care.

Comparison of nuclear cardiology in the United States and Europe.

Nuclear Cardiology is widely available and a widely accepted tool for diagnosis and management of coronary artery disease both in the US and in Europe. Although the most common indications for nuclear studies are similar in the US and Europe, different social and economical environments may affect the practice of Nuclear Cardiology. The aim of this paper is to identify key issues and to provide some information on the similarities and differences which characterize the practice of Nuclear Cardiology in the US and Europe. This paper takes into account the training requirements, the relationships between different professional societies, the accessibility, the choice of imaging protocols, tracers and stressors, the impact of managed care and the role of cardiologists, nuclear physicians and technologists in nuclear labs. The economical differences which may affect the field of high technology, imply a wide range of variability concerning the availability of nuclear cardiology studies in different countries (1:1/10). Moreover the legislation which regulates the practice of nuclear medicine may differ from country to country. Thus in our opinion there are several important factors both in the US and Europe limiting the development of nuclear cardiology independently of its intrinsic clinical value.

Prognostic value of tomographic rest-redistribution thallium 201 imaging in medically treated patients with coronary artery disease and left ventricular dysfunction.

BACKGROUND: Previous studies show that rest-redistribution thallium imaging is useful in the assessment of myocardial viability. The impact of such studies on patient outcome is not well defined. This study examined the prognostic value of tomographic rest-redistribution 201T1 imaging in 81 medically treated patients with coronary artery disease and left ventricular dysfunction. METHODS AND RESULTS: Rest-redistribution single-photon emission computed tomographic images were obtained and analyzed quantitatively. The segmental thallium uptake (20 segments per patient) was interpreted as normal, reversible defect, mild to moderate fixed defect, or severe fixed defect. The thallium images were abnormal in 80 patients, with no redistribution (no ischemia) in 43 patients and redistribution (ischemia) in 38 patients. The left ventricular ejection fraction was 27% +/- 8% in patients with no redistribution and 26% +/- 7% in patients with redistribution (difference not significant). In patients with no ischemia, there were 7 +/- 5 severe fixed defects and 5 +/- 4 mild to moderate fixed defects per patient. In patients with ischemia there were 7 +/- 4 reversible defects, 3 +/- 3 mild to moderate fixed defects, and 5 +/- 4 severe fixed defects per patient. The number of any abnormal segments was 11 +/- 5 in patients with no ischemia and 14 +/- 4 in patients with ischemia (p = 0.03). During a mean follow-up of 31 +/- 24 months, there were 11 cardiac deaths in patients with no ischemia (26%) and 22 in patients with ischemia (58%); the survival rate was worse in patients with than without ischemia (p < 0.05). Multivariate Cox survival analysis on important clinical, angiographic, and thallium variables showed that the presence of redistribution was an independent predictor of death (x2 = 5; p = 0.03). CONCLUSIONS: Patients with left ventricular dysfunction and redistribution on rest thallium imaging, a marker of hibernating myocardium, have a higher mortality rate with medical therapy than do patients with a comparable degree of left ventricular dysfunction but with fixed defects only. Thus observations similar to those made with positron emission tomography can be made in a much more straightforward, simple, and probably cost-effective manner with single-photon emission computed tomography.

Arbutamine stress thallium-201 single-photon emission computed tomography using a computerized closed-loop delivery system. Multicenter trial for evaluation of safety and diagnostic accuracy. The International Arbutamine Study Group.

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.

Use of a tantalum-178 generator and a multiwire gamma camera to study the effect of the Mueller maneuver on left ventricular performance: comparison to hemodynamics and single photon emission computed tomography perfusion patterns.

During the Mueller maneuver, there is a decrease in intrathoracic pressure and an increase in transmural left ventricular pressure. The changes in loading conditions cause transient left ventricular dysfunction. This study examined the effects of the Mueller maneuver on left ventricular performance using tantalum (Ta)-178 (half-life 9.3 min) and a multiwire gamma camera. First-pass radionuclide angiograms were obtained at baseline and during Mueller maneuver in 41 patients aged 58 +/- 10 years. In 34 patients, stress single photon emission computed tomography (SPECT) myocardial perfusion imaging with thallium-201 or sestamibi was also performed. Hemodynamic measurements during the Mueller maneuver (n = 10) showed a decrease in systemic pressure (139 +/- 25 mm Hg vs 123 +/- 24 mm Hg, p < 0.001) and pulmonary artery pressure (24 +/- 6 mm Hg vs 14 +/- 12 mm Hg, p = 0.01) and an increase in heart rate (67 +/- 10 bpm vs 75 +/- 14 beats/min, p = 0.001). Among the 34 patients who had perfusion imaging, the left ventricular ejection fraction remained unchanged or increased in 17 patients (group 1) (48% +/- 19% vs 49% +/- 21%, p not significant) and decreased (> or = 5%) in 17 patients (group 2) (55% +/- 13% vs 40% +/- 16%, p = 0.001). The stress SPECT images showed no or only fixed defects in 11 (65%) patients in group 1 and 3 (18%) patients in group 2 (p = 0.02), and reversible defects in 6 (35%) patients in group 1 and 14 (82%) patients in group 2 (p = 0.04).(ABSTRACT TRUNCATED AT 250 WORDS)

Prediction of improvement in left ventricular function with iodine-123-IPPA after coronary revascularization.

UNLABELLED: Iodine-123-phenylpentadecanoic acid (IPPA) is a synthetic fatty acid suitable for myocardial imaging. This study is the result of a Phase I/II trial to evaluate IPPA's ability to predict functional recovery in patients undergoing coronary revascularization. METHODS: Twenty-three patients with documented coronary disease underwent sequential SPECT imaging with IPPA before and radionuclide ventriculography both before and 8 wk after revascularization. Software was developed to evaluate myocardial IPPA metabolism and to determine the fraction of the left ventricle with intermediate metabolism. RESULTS: There was a significant correlation between initial IPPA uptake and final LVEF. The fractional area of the left ventricle demonstrating IPPA metabolism in the intermediate metabolic range was significantly higher in patients who demonstrated a 5% or greater increase in EF after revascularization (0.90 +/- 0.08 versus 0.78 +/- 0.17, p = 0.04). When only the patients who received complete revascularization were evaluated, there was a more significant difference (improved 0.92 +/- 0.05 versus 0.74 +/- 0.17, p = 0.011). Taking a lower limit of 1 s.d. from the mean, (87%) the six patients who had > or = 5% increase in LVEF after revascularization had more than 87% of the left ventricle in the intermediate metabolic range, whereas seven of ten patients whose change in LVEF was < 5% had less than 87% in the intermediate metabolic range (p = 0.011). CONCLUSION: In this initial experience, the amount of myocardium in the intermediate metabolic range is associated with improvement in LVEF after revascularization, especially in patients receiving complete revascularization.

Implications of increased lung thallium uptake during exercise single photon emission computed tomography imaging.

Increased lung thallium uptake during exercise is an important marker of patients who are at high risk and have CAD; however, most previous studies were done with planar imaging, and therefore it is unclear whether this conclusion is also true with SPECT imaging. This study examined the lung thallium uptake during exercise SPECT imaging in 1031 patients who also underwent coronary angiography. The lung thallium uptake was increased in 309 patients (group 1) and normal in 722 patients (group 2). Compared with patients in group 2, those in group 1 had more ST segment depression (44% vs 28%, p = 0.01), previous Q-wave myocardial infarction (28% vs 17%, p = 0.0001), larger perfusion defects (24% +/- 11% vs 10% +/- 11%, p = 0.0001), and multivessel CAD by angiography (75% vs 47%, p = 0.0001). Multivariate discriminant analysis identified left ventricular dilation, reversible defects, the size of perfusion abnormality, and the extent of CAD as independent predictors of increased lung thallium uptake. Increased lung thallium uptake was more common in men than women regardless of the extent of CAD: 26% versus 11% in patients with one-vessel, 38% versus 18% in patients with two-vessel, and 51% versus 31% in patients with three-vessel disease (p < 0.001 each). Thus increased lung thallium uptake by SPECT identifies patients with more severe anatomic and functional evidence of CAD. The sex-related difference suggests the need for a sex-specific normal file for quantitative analysis.

Results of adenosine single photon emission computed tomography thallium-201 imaging in hemodynamic nonresponders.

Systolic blood pressure typically decreases during adenosine infusion because of stimulation of A2b receptors, resulting in systemic vasodilation. This study examined the results of adenosine single photon emission computed tomography (SPECT) thallium-201 imaging in patients who did not show such a decrease in blood pressure during peak adenosine effect (nonresponders). The 102 nonresponders and 341 responders had no significant differences in age, gender, history of diabetes mellitus, hypertension, or previous myocardial infarction. The extent of coronary artery disease (CAD) by angiography was also similar. The sensitivity of SPECT thallium-201 imaging in patients with one-vessel disease was 82% in nonresponders and 84% in responders (p value not significant [NS]); in patients with multivessel disease, it was 90% in nonresponders and 94% in responders (p = NS) and for all CAD, it was 87% in non-responders and 91% in responders (p = NS). Thus lack of hemodynamic systemic response during adenosine infusion does not affect sensitivity for detecting CAD.