Incremental prognostic power of single-photon emission computed tomographic myocardial perfusion imaging in patients with known or suspected coronary artery disease

Noninvasive stress testing provides prognostic information in patients who have suspected coronary artery disease, but limited data are available on the incremental value of myocardial perfusion testing in high-risk patients. We studied 3,275 patients who underwent cardiac catheterization and single-photon emission computed tomographic (SPECT) perfusion imaging. Median follow-up was 3.1 years for death, cardiovascular death, and a composite of cardiovascular death or nonfatal myocardial infarction. Using Cox's proportional hazards regression models, we examined the relation of SPECT summed stress score (SSS) to each outcome. A 1-unit change in SSS was associated with increased risks of 4%, 7%, and 5% for death, cardiovascular death, and death or nonfatal myocardial infarction, respectively (all p <0.0001). To examine the prognostic utility of SPECT, after baseline adjustments, SSS and angiographic results provided incremental prognostic information for each outcome. Thus, SPECT SSS provides information beyond clinical and angiographic data in patients who have known or suspected coronary artery disease. This information may be useful for stratifying patients into multiple risk categories for future cardiovascular events and potentially guiding therapy.     

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.     

Pinhole single-photon emission computed tomography for myocardial perfusion imaging of mice

OBJECTIVES: Although transgenic mice have emerged as powerful experimental models of cardiovascular disease, methods for in vivo phenotypic assessment and characterization remain limited, motivating the development of new instruments for biologic measurement. BACKGROUND: We have developed a single-photon emission computed tomography system with a pinhole collimator (pinhole SPECT) for high-resolution cardiovascular imaging of mice. In this study, we describe a protocol for myocardial perfusion imaging of mice using technetium-99m ((99m)Tc)-sestamibi and demonstrate the feasibility for measurement of perfusion defect size from pinhole SPECT images. METHODS: Mice were anesthetized and injected with 370 MBq (10 mCi) of (99m)Tc-sestamibi. Tomographic projection images were acquired by rotating each mouse in a vertical axis in front of a stationary clinical scintillation camera equipped with a pinhole collimator. BALB/c mice (n = 15) were imaged after the permanent ligation of the left anterior descending coronary artery. The resulting defect size was measured from circumferential profiles of short-axis images. After imaging, the hearts were excised and sectioned to obtain ultra-high resolution digital autoradiographs of (99m)Tc-sestamibi, from which the actual infarct size was determined. RESULTS: Reconstructed image quality was equivalent to that obtained for clinical myocardial perfusion imaging. Linear regression analysis produced a correlation coefficient of 0.83 (p < 0.001) between the measured and actual values of the defect size. CONCLUSIONS: These results demonstrate that myocardial perfusion can be characterized qualitatively and quantitatively in mice using pinhole SPECT.     

Prognostic value of thallium-201 single-photon emission computed tomographic myocardial perfusion imaging according to extent of myocardial defect: Study in 1,926 patients with foilow-up at 33 months

Objectives. This study was designed to assess the prognostic value of thallium-201 single-photon emission computed tomographic (thallium SPECT) perfusion imaging in patients evaluated for stable angina pectoris and to examine the relation, if any, between the preface and extent of myocardial defect and future fatal or nonfatal cardiovascular events (revascularization, secondary myocardial infarction).Background. Compared with planar scintigraphy, thallium SPECT enables better evaluation of the extent of mayocardial perfusion defect. However, its prognostic value has not yet been studied in a large population of patients.Methods. Between 1987 and 1989 we studied 3,193 patients. After exclusion of patients with unstable angina, myocardial infarction during the previous month or earlier revascularization, 1,926 patients were followed up for 33 ± 10 (mean ± SD) months after stress thallium SPECT imaging (performed after exercise in 1,121 patients or during dipyridamole infusion in 805 patients). Thallium SPECT imaging of the left ventricle was divided into six segments.Results. After normal thallium SPECT imaging (715 patients), the annual total and cardiovascular mortality rates were, respectively, 0.42%/year and 0.10%/year and were significantly higher after abnormal thallium SPECT imaging (respectively, 2.1%, relative risk 5, p = 0.012; 1.5%, relative risk 15, p < 0.0001 [log-rank test]). There was a significant relation between the number of abnormal segments and cardiovascular mortality during follow-up (p < 0.02) or the occurrence of nonfatal events (p < 0.001). The extent of defect on the initial scan provided the best SPECT variable for long-term prognosis. Thallium SPECT imaging provided additive prognostic information compared with other clinical variables (gender, previous myocardial infarction) and exercise electrocardiogram.Conclusions. In patients with stable angina, normal thallium SPECT imaging indicates a low risk patient, and the extent of myocardial defect is an important prognostic predictive factor.     

Ethnic differences in the prognostic value of stress technetium-99m tetrofosmin gated single-photon emission computed tomography myocardial perfusion imaging

OBJECTIVES: This study was designed to evaluate the differential prognostic value of gated single-photon emission computed tomographic imaging (SPECT) imaging in an ethnically diverse multicenter registry. BACKGROUND: Ethnic minority patient populations have reportedly higher coronary heart disease mortality with greater comorbidity and a clustering of risk factors at a significantly younger age when compared with Caucasian, non-Hispanic patients. Despite our increasingly diverse population, the predictive accuracy of cardiac imaging in ethnic minority patients is ill-defined. METHODS: A total of 7,849 patients were prospectively enrolled in a registry of patients undergoing exercise (44%) or pharmacologic stress (56%) technetium-99m tetrofosmin SPECT. Scans were scored using a 20-segment myocardial model with a 5-point severity index. Multivariable Cox proportional hazards models were employed to assess time to death or myocardial infarction. RESULTS: A total of 1,993 African-American, 464 Hispanic, and 5,258 Caucasian non-Hispanic patients underwent SPECT imaging. African-American and Hispanic patients more often had a history of stroke, peripheral arterial disease, angina, heart failure, diabetes, hypertension, and smoking at a younger age. Moderate or severely abnormal SPECT scans were noted in 21%, 17%, and 13% of African-American, Hispanic, and Caucasian non-Hispanic patients, respectively (p < 0.0001). Cardiovascular death rates were highest for ethnic minority patients (p < 0.0001). Annual rates of ischemic heart disease death ranged from 0.2% to 3.0% for Caucasian non-Hispanic and 0.8% to 6.5% for African-American patients with low-risk to severely abnormal SPECT scans (p < 0.0001). For post-stress ejection fraction <45%, annualized risk-adjusted death rates were 2.7% for Caucasian non-Hispanic patients versus 8.0% and 14.0% for African-American and Hispanic patients (p < 0.0001). CONCLUSIONS: The current results from a large observational registry reveal that exercise and pharmacologic stress SPECT effectively predicts major cardiovascular events in a large cohort of African-American and Hispanic patients evaluated for suspected myocardial ischemia. These results provide further evidence that ethnic minority patient populations have a worsening outcome related to cardiovascular disease.     

Comparison of single-photon emission computed tomographic (SPECT) myocardial perfusion imaging with thallium-201 and technetium-99m sestamibi in dogs.

OBJECTIVES. The purpose of the present study was to compare single-photon emission computed tomographic (SPECT) myocardial images of technetium-99m (Tc-99m) sestamibi and thallium-201 (Tl-201) isotopes in the same dog undergoing partial coronary occlusion during pharmacologic vasodilation. BACKGROUND. To date, no controlled study has been reported comparing SPECT Tc-99m sestamibi with SPECT Tl-201 imaging during stress with anatomic and physiologic standards. METHODS. Mongrel dogs were anesthetized with chloralose and instrumented to record left anterior descending coronary blood flow and aortic pressure. Partial coronary occlusion with a hydraulic cuff reduced coronary vascular conductance, which is equal to the coronary blood flow normalized to aortic pressure during peak vasodilation with intravenous adenosine. Each dog received 5 mCi of Tl-201, then 30 mCi of Tc-99m sestamibi during partial coronary occlusion at peak vasodilation. Tomographic myocardial imaging was performed in a 180 degrees anterior arc scan for 33.5 min, first with Tl-201, and later, without moving the dog, for 33.5 min with Tc-99m sestamibi. Postmortem staining defined the region underperfused because of its dependence on the artery that was partially occluded. RESULTS. In seven dogs with moderate reduction in coronary blood flow, coronary vascular conductance decreased with partial coronary occlusion (47 +/- 12%) during Tl-201 imaging and (47 +/- 8%, p = NS) during Tc-99m sestamibi imaging. The underperfused region was 23.9 +/- 6.4% of total left ventricular mass. Counts in the defects were 39% higher (0.86 +/- 0.08 of normal counts) for Tc-99m sestamibi than for Tl-201 (0.64 +/- 0.09 of normal counts, p < 0.001), and the defect on SPECT Tc-99m sestamibi images occupied only a fraction (0.37 +/- 0.30) of the area of the defect on the Tl-201 images of the same dog. Bull's-eye displays constructed from the pathologic slices showed that the Tl-201 defect size was closer to the underperfused region of the left ventricular mass determined pathologically than was the Tc-99m sestamibi defect size. In four additional dogs a severe, near total coronary occlusion was created during Tl-201 and Tc-99m sestamibi administration. In these dogs, similar defect contrast (0.55 +/- 0.12 vs. 0.62 +/- 0.09, p = NS) and areas (0.18 +/- 0.07 vs. 0.18 +/- 0.11, p = NS) were observed with Tl-201 and Tc-99m sestamibi, respectively. CONCLUSIONS. Tomographic myocardial imaging with Tc-99m sestamibi during moderately severe partial coronary occlusion underestimated the area of the defect relative to Tl-201 or to the pathologic reference standard in dogs. Defect contrast was sharper with tomographic myocardial Tl-201 than with tomographic myocardial Tc-99m sestamibi during moderately severe partial coronary occlusion.     

Impact of limited treadmill exercise on adenosine Tc-99m sestamibi single-photon emission computed tomographic myocardial perfusion imaging in coronary artery disease.

Limited exercise combined with dipyridamole increases myocardial perfusion defect severity compared with dipyridamole alone. The impact of limited exercise combined with adenosine on myocardial perfusion defect severity is unknown. This study compares myocardial perfusion defect severity with adenosine alone and adenosine combined with limited exercise. Thirty-two patients with coronary artery disease underwent on separate days and in randomized order technetium-99m sestamibi (25 to 30 mCi) single-photon emission computed tomographic imaging at rest, after adenosine (140 microg/kg/min x 6 minutes), and after adenosine (140 microg/kg/min x 4 minutes) during 6 minutes of modified Bruce treadmill exercise (adenosine-exercise). Radiopharmaceutical was injected at 3 and 5 minutes during adenosine and adenosine-exercise, respectively. Images were interpreted by a consensus agreement of 3 nuclear cardiologists without knowledge of patient identity, stress protocol, or clinical data using a 17-segment model and 5-point scoring system. A summed stress score (SSS), summed rest score (SRS), and summed difference (SSS-SRS) score (SDS) were calculated for each image. Peak stress heart rate and rate-pressure product were higher for adenosine-exercise than adenosine (102 +/- 19 vs 81 +/- 11 beats/min and 13,972 +/- 4,265 vs 10,623 +/- 2,131, respectively; both p <0.001). Sensitivity for detection of > or = 50% coronary stenosis was 75% and 72% for adenosine-exercise and adenosine, respectively (p = NS). There were no differences in SSS and SDS between adenosine-exercise and adenosine (8.2 +/- 5.9 vs 8.1 +/- 6.3 and 4.9 +/- 4.1 vs 5.2 +/- 4.6, respectively; both p = NS). Thus, in patients with coronary artery disease, limited treadmill exercise combined with adenosine does not increase myocardial perfusion defect severity compared with standard adenosine technetium-99m sestamibi single-photon emission computed tomographic myocardial perfusion imaging.     

Intracoronary doppler guide wire versus stress single-photon emission computed tomographic thallium-201 imaging in assessment of intermediate coronary stenosis

Objectives. The purpose of this study was to compare measures of coronary flow reserve by an intracoronary Doppler guide wire with results of stress single-photon emission computed tomographic (SPECT) thallium-201 imaging in patients with intermediate coronary artery disease (40% to 70% stenosis).Background. Visual assessment of the coronary arteriogram as a means of predicting the physiologic significance of intermediate coronary stenoses is inaccurate. Coronary flow reserve is a reliable marker of the functional importance of a coronary lesion. The recent development of an intracoronary Doppler guide wire permits routine assessment of coronary flow reserve distal to coronary artery stenoses.Methods. We prospectively evaluated coronary flow reserve in 30 subjects with intermediate stenoses using an intracoronary Doppler guide wire during elective coronary angiography. Patients subsequently underwent stress SPECT thallium-201 testing, and the blinded interpretations were correlated. Coronary flow reserve in a control group with normal coronary arteries classified our sample into group 1 (abnormal flow reserve, <2.0) and group 2 (normal flow reserve, ≥2.0).Results. As defined, the coronary flow reserve of 16 vessels in group 1 was diminished in comparison to that of 19 vessels in group 2 (p = 0.0001). Qualitative and quantitative analysis of stress SPECT thallium-201 images confirmed perfusion defects in 15 of 16 vascular territories in group 1 in contrast to 1 of 19 regions in group 2. The sensitivity, specificity and overall predictive accuracy of Doppler-determined coronary flow reserve for stress SPECT thallium-201 results were 94%, 91% and 94%, respectively.Conclusions. In appropriately selected patients with intermediate coronary artery stenoses. Doppler guide wire determination of lesion significance provides equivalent data to those acquired by stress SPECT thallium-201 imaging.     

Gated single-photon emission computed tomographic myocardial imaging: a new tool in clinical cardiology

BACKGROUND: Gated single-photon emission computed tomography (gated SPECT) myocardial perfusion imaging allows the analysis of left ventricular (LV) perfusion and function during the same acquisition. RESULTS: Gated SPECT provides additional information to myocardial perfusion, which improves test specificity in patients with known or suspected coronary artery disease and hence diminishes the amount of borderline diagnosis. Because gated SPECT provides reliable information on LV ejection fraction and LV volumes, it is also a valuable tool in risk stratification. In addition, from gated SPECT, images can be reconstructed from which wall motion can be assessed showing a good correlation with wall motion assessed by accepted imaging modalities as echocardiography, magnetic resonance imaging, and contrast angiography. In the future wall motion analysis from gated SPECT may also be used for revascularization stratification. CONCLUSIONS: Gated SPECT gives important additional information beyond myocardial perfusion imaging alone, which could have major clinical implications for optimal patient management.     

Comparative prognostic value of automatic quantitative analysis versus semiquantitative visual analysis of exercise myocardial perfusion single-photon emission computed tomography

Objectives. The purpose of this study was to determine the prognostic value of automatic quantitative analysis in exercise dual-isotope myocardial perfusion single-photon emission computed tomography (SPECT) and to compare the prognostic value of quantitative analysis to semiquantitative visual SPECT analysis.

Background. Extent, severity and reversibility of exercise myocardial perfusion defects have been shown to correlate with prognosis. However, most studies examining the prognostic value of SPECT in chronic coronary artery disease (CAD) have been based on visual analysis by experts.

Methods. We studied 1,043 consecutive patients with known or suspected CAD who underwent rest Tl-201/exercise Tc-99m sestamibi dual-isotope myocardial perfusion SPECT and were followed up for at least 1 year (mean 20.0 ± 3.7 months). After censoring 59 patients with early coronary artery bypass grafting or percutaneous transluminal coronary angioplasty, <60 days after nuclear testing, the final population consisted of 984 patients (36% women, mean age 63 ± 12 years).

Results. During the follow-up period, 28 hard events (14 cardiac deaths, 14 nonfatal myocardial infarctions) occurred. Patients with higher defect extent (>10%), severity (>150) and reversibility (>5%) by quantitative SPECT defect analysis, as well as those with an abnormal scan (>2 abnormal segments, summed stress score >4 and summed difference score >2) by semiquantitative visual SPECT analysis, had a significantly higher hard event rate compared to patients with a normal scan (p < 0.001). With both visual and quantitative analyses, hard event rates of approximately 1% with normal scans and 5% with abnormal scans (p > 0.05) were observed over the 20-month follow-up period. A Cox proportional hazards regression model showed that chi-square increased similarly with the addition of quantitative defect extent and visual summed stress score variables after considering both clinical and exercise variables (improvement chi-square = 11 for both, p < 0.0007). There were no significant differences in the areas under receiver operating characteristic curves between quantitative and visual analysis (p > 0.70). Linear regression analysis also indicated that quantitative assessments correlated well with visual semiquantitative assessments.

Conclusions. The findings of this study indicate that automatic quantitative analysis of exercise stress myocardial perfusion SPECT is similar to semiquantitative expert visual analysis for prognostic stratification. These findings may be of particular clinical importance in laboratories with less experienced visual interpreters.     

Major advances in single-photon emission computed tomography perfusion imaging

Major advances in single-photon emission computed tomography (SPECT) myocardial perfusion imaging have been realized with the introduction of state-of-the-art imaging equipment and radiopharmaceuticals. Gated tomographic myocardial perfusion imaging with technetium-99m (Tc-99m)-labeled radiopharmaceuticals provides a combined evaluation of both myocardial perfusion and function. Left ventricular ejection fraction can be measured accurately from the gated SPECT images. Recently, hardware and software have been introduced, which minimize the effect of soft tissue attenuation, thereby improving test specificity in the diagnosis of coronary artery disease. Myocardial viability may be assessed with the use of rest/delayed thallium-201 SPECT or F-18 fluorodeoxyglucose SPECT with modified scintillation camera collimation and electronics, or coincidence detection. Imaging patients to assess myocardial infarction or resting ischemia in the emergency department has expedited patient care and improved cost effectiveness. Teleradiography has also facilitated the interpretation of studies performed in the emergency department and at remote facilities, likewise improving cost-effectiveness.     

Quantitative relation of ST-segment depression during exercise to the magnitude of myocardial ischemia as assessed by single-photon emission computed tomographic myocardial perfusion imaging

The mechanism of ST-segment depression during exercise electrocardiographic treadmill testing (ETT) is unknown. The relatively good correlation between the results of ETT and myocardial perfusion imaging suggests that ST-segment depression may be related to the magnitude of ischemia. Previous studies that investigated this relation have produced conflicting results. We evaluated 1,006 patients who underwent symptom-limited ETT and technetium-99m single-photon emission computed tomographic myocardial perfusion imaging at rest and during stress at a single institution. The magnitude, extent, and duration of ST-segment depression were each strongly associated with the magnitude of myocardial ischemia (p <0.001 for all). The magnitude, extent, and duration of ST-segment depression were highly correlated with each other and had similar relations to the magnitude of ischemia. After adjustment for significant clinical and ETT parameters, these relations remained highly significant. The location of myocardial ischemia was unrelated to ST-segment depression. This large study found that ST-segment depression during ETT is strongly associated with the magnitude of ischemia. These data support a causative role for the magnitude of ischemia in the generation of ST-segment depression.     

Single-photon emission computed tomographic myocardial perfusion imaging in patients with mitral valve prolapse

The possibility of exercise-induced myocardial ischemia due to mitral valve prolapse (MVP) in the absence of coronary artery disease was evaluated with single-photon emission computed tomographic analysis using thallium-201 and technetium-99m sestamibi in 72 patients with MVP. Exercise electrocardiography was positive in 5 patients (8%), but single-photon emission computed tomography was found to be normal in all patients, and exercise-induced chest pain, electrocardiographic changes, and arrhythmias were found not to be related to myocardial ischemia in patients with MVP.     

Comparison between angiography and fractional flow reserve versus single-photon emission computed tomographic myocardial perfusion imaging for determining lesion significance in patients with multivessel coronary disease

We hypothesized that myocardial perfusion imaging (MPI) would fail to identify all vascular zones with the potential for myocardial ischemia in patients with multivessel coronary disease (MVD). MPI is based on the concept of relative flow reserve. The ability of these techniques to determine the significance of a particular stenosis in the setting of MVD is questionable. Fractional flow reserve (FFR) can determine the significance of individual stenoses. Thirty-six patients with disease involving 88 arteries underwent angiography, FFR, and MPI. FFR was performed using a pressure wire with hyperemia from intracoronary adenosine. Myocardial perfusion images were analyzed quantitatively and segments assigned to a specific coronary artery. The relation between FFR and perfusion was determined for each vascular zone. Of the 88 vessels, the artery was occluded (n=20) or had an abnormal FFR相似文献   

Comparison of prognostic value of negative dobutamine stress echocardiography versus single-photon emission computed tomography after acute myocardial infarction

We enrolled 196 patients who had myocardial infarction and no ischemia on dobutamine stress echocardiography (DSE) and/or single-photon emission computed tomography (SPECT). Negative studies were observed in 125 patients on DSE and in 159 on SPECT. Patients were followed for 43 +/- 14 months. Cardiac events occurred in 14% of patients who did not have ischemia on DSE and in 9% of patients who did not have ischemia on SPECT. Event-free survival rate was higher in the presence of negative findings on SPECT compared with DSE (p <0.05). The lack of residual myocardial ischemia on SPECT identifies patients at low risk of events, and a negative finding on stress SPECT is superior to a negative finding on DSE.     

Selective use of single-photon emission computed tomography myocardial perfusion imaging in a chest pain center

Emergency department chest pain centers (CPCs) vary in their approach to patients with chest pain and nonischemic electrocardiograms (ECG). Although single-photon emission computed tomography (SPECT) myocardial perfusion imaging has been evaluated in this setting, both acutely at rest and after stress, we questioned its application in all patients. We prospectively evaluated the utility of selective SPECT imaging in a CPC (i.e., rest SPECT for ongoing pain, stress SPECT if unable to undergo exercise electrocardiography) and its impact on the overall disposition of all emergency department chest pain patients. Over 3 years, 2,601 patients were evaluated in a CPC (2,211 [85%] were sent home, 390 [15%] were hospitalized). Of 390 CPC patients hospitalized, 182 (47%) were diagnosed with coronary artery disease at the time of hospital discharge. Only 28 patients (1.1%) had an acute myocardial infarction. After 3 years, the proportion of all chest pain patients hospitalized and those diagnosed as “rule-out myocardial infarction” decreased from 53% to 41% and 32% to 18% of all chest pain patients, respectively (both p <0.0001). Overall, 906 patients (35%) required SPECT imaging to complete the CPC evaluation. Had SPECT imaging not been performed selectively, and all 906 patients been admitted, 762 (29%) would have been hospitalized unnecessarily based on the final diagnoses. Alternatively, sending all these patients home would have resulted in 144 (6%) inappropriate discharges of patients with coronary artery disease. A CPC protocol using the selective use of SPECT imaging permits the complete evaluation of all patients in the CPC, significantly reduces hospitalizations for chest pain, and restricts hospital admission to more appropriate patients.