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H Kiat

Publications and source records attributed to H Kiat.

At least 19 recordsLinked to original sources
PubMed1999

Multicenter clinical trial to evaluate the efficacy of correction for photon attenuation and scatter in SPECT myocardial perfusion imaging.

BACKGROUND: Soft tissue attenuation is a prominent cause of single-photon emission computed tomography (SPECT) imaging artifacts, which may result in reduced diagnostic accuracy of myocardial perfusion imaging. A method incorporating simultaneously acquired transmission data permits nonuniform attenuation correction and when incorporating scatter correction and resolution compensation may substantially reduce interpretive errors. METHODS AND RESULTS: A prospective multicenter trial was performed recruiting patients with angiographically documented coronary disease (n=96) and group of subjects with a low likelihood of disease (n=88). The uncorrected and attenuation/scatter corrected images were read independently, without knowledge of the patient's clinical data. The detection of >/=50% stenosis was similar using uncorrected perfusion data or with attenuation/scatter correction and resolution compensation (visual or visual plus quantitative analysis), 76% versus 75% versus 78%, respectively (P=NS). The normalcy rate, however, was significantly improved with this new methodology, using either the corrected images (86% vs 96%; P=0.011) or with the corrected data and quantitative analysis (86% vs 97%; P=0.007). The receiver operator characteristic curves were also found to be marginally but not significantly higher with attenuation/scatter correction than with tradition SPECT imaging. However, the ability to detect multivessel disease was reduced with attenuation/scatter correction. Regional differences were also noted, with reduced sensitivity but improved specificity for right coronary lesions using attenuation/scatter correction methodology. CONCLUSIONS: This multicenter trial demonstrates the initial clinical results of a new SPECT perfusion imaging modality incorporating attenuation and scatter correction in conjunction with 99mTc sestamibi perfusion imaging. Significant improvements in the normalcy rate were noted without a decline in overall sensitivity but with a reduction in detection of extensive coronary disease.

Data Interpretation, Statistical↗
PubMed1998

Incremental prognostic value of adenosine myocardial perfusion single-photon emission computed tomography in women with suspected coronary artery disease.

Adenosine myocardial perfusion single-photon emission computed tomography (SPECT) is now increasingly used for risk stratification of patients with known or suspected coronary artery disease. However, the incremental prognostic value of this test over clinical and historical information in a large series of women has not been examined. Thus, we studied 923 consecutive women who underwent adenosine technetium (Tc)-99m sestamibi myocardial perfusion SPECT and were followed-up for a mean period of 26+/-8 months. During the follow-up period, 77 hard events (46 cardiac deaths and 31 nonfatal myocardial infarctions) occurred. The results of the perfusion scan significantly risk stratified the population; patients with normal scans had a low rate of nonfatal myocardial infarction and cardiac death (< 1%/year of follow up). Patients with mildly abnormal scans had low cardiac death rates (0.9%/year of follow up); these rates increased as a function of scan abnormality (4.1% and 7.5% mortality per year of follow up in moderate and severely abnormal scans). Cox proportional hazards analysis demonstrated that after adjusting for prior myocardial infarction and diabetes mellitus (the most predictive individual clinical variables [global chi-square=22.5, p <0.001]), as well as heart rate at rest (the most predictive physiologic variable [chi-square=3.8; p=0.05]), the most predictive nuclear variable (summed stress score [chi-square=48.5; p <0.0001]) added significant incremental prognostic information (global chi-square increased from 22.5 to 56.2 [p <0.0001]). In conclusion, adenosine myocardial perfusion SPECT added significant incremental prognostic information to clinical and physiologic variables in women. Normal scans were associated with an excellent prognosis. In contrast, patients with moderately to severely abnormal scans were at a higher risk for future cardiac events.

Adenosine↗
PubMed1998

Incremental prognostic value of myocardial perfusion single photon emission computed tomography for the prediction of cardiac death: differential stratification for risk of cardiac death and myocardial infarction.

BACKGROUND: The incremental prognostic value of stress single photon emission computed tomography (SPECT) for the prediction of cardiac death as an individual end point and the implications for risk stratification are undefined. METHODS AND RESULTS: We identified 5183 consecutive patients who underwent stress/rest SPECT and were followed up for the occurrence of cardiac death or myocardial infarction. Over a mean follow up of 642+/-226 days, 119 cardiac deaths and 158 myocardial infarctions occurred (3.0% cardiac death rate, 2.3% myocardial infarction rate). Patients with normal scans were at low risk (< or =0.5%/y), and rates of both outcomes increased significantly with worsening scan abnormalities. Patients who underwent exercise stress and had mildly abnormal scans had low rates of cardiac death but higher rates of myocardial infarction (0.7%/y versus 2.6%/y; P<.05). After adjustment for prescan information, scan results provided incremental prognostic value toward the prediction of cardiac death. The identification of patients at intermediate risk of nonfatal myocardial infarction and low risk for cardiac death by SPECT may result in significant cost savings when applied to a clinical testing strategy. CONCLUSIONS: Myocardial perfusion SPECT yields incremental prognostic information toward the identification of cardiac death. Patients with mildly abnormal scans after exercise stress are at low risk for cardiac death but intermediate risk for nonfatal myocardial infarction and thus may benefit from a noninvasive strategy and may not require invasive management.

Adenosine↗
PubMed1997

Incremental prognostic value of adenosine stress myocardial perfusion single-photon emission computed tomography and impact on subsequent management in patients with or suspected of having myocardial ischemia.

We examined 1,159 consecutive patients who underwent adenosine stress dual isotope single-photon emission computed tomography (SPECT) and had follow-up performed at a mean of 27.5 +/- 9.1 months (94% complete) for hard events (cardiac death and myocardial infarction) and referral to cardiac catheterization after nuclear testing. During follow-up, 120 hard events occurred (11.0% hard event rate; 72 cardiac deaths [6.7% cardiac death rate] and 57 myocardial infarctions [5.3% myocardial infarction rate]). Cox proportional hazards analysis revealed that nuclear testing added incremental value after adjusting for clinical and historical variables (global chi-square increased 13 to 98 for cardiac death as the end point, global chi-square increased 19 to 105 for hard events as the end point; p <0.0001 for both). Kaplan-Meier analysis demonstrated that after clinical risk stratification of the patient population, the results of nuclear testing were further able to significantly stratify both low- and intermediate- to high-risk patients. Patients with both normal and mildly abnormal scans were at low risk of cardiac death (<1% cardiac death per year of follow-up) and the risk of events increased significantly with worsening scan result. Multivariable analysis revealed that the only predictor of referral to catheterization was the extent and severity of reversible defect present on the scan. Referral rates to early catheterization were very low in patients with normal scans and increased significantly as a function of worsening scan results. In patients who underwent myocardial perfusion SPECT using adenosine stress, the results of nuclear testing yielded incremental prognostic information and clinically relevant risk stratification. Referring physicians predominantly utilized nuclear information when referring patients to catheterization after nuclear testing and do so at rates comparable with those after exercise SPECT despite the higher risk of events in patients undergoing pharmacologic stress.

Adenosine↗
PubMed1997

Identification of severe or extensive coronary artery disease in women by adenosine technetium-99m sestamibi SPECT.

To assess the ability of adenosine technetium-99m sestamibi myocardial perfusion single-photon emission computed tomography (SPECT) to identify high-risk women with severe or extensive coronary artery disease (CAD), we studied 130 consecutive women who underwent adenosine sestamibi myocardial perfusion SPECT and catheterization within 2 months. Severe (> or = 50% stenosis of left main coronary artery, > or = 90% stenosis in the proximal left anterior descending or in > or = 2 coronary arteries) or extensive (> or = 70% stenosis in 3 vessels) CAD was present in 54 patients, whereas 76 had no CAD or mild to moderate CAD. Semiquantitative visual SPECT analysis used 20 segments and a 5-point scoring system (0 = normal, 4 = absent uptake). Among the clinical, hemodynamic and nuclear variables analyzed, univariate predictors of severe or extensive CAD included a higher prescan likelihood of CAD, history of myocardial infarction, a higher heart rate at rest, a lower increase in heart rate during adenosine infusion, a higher summed stress score, summed reversibility score, and multivessel scan abnormality. Multivariate logistic analysis of the most predictive clinical (prescan likelihood of CAD), hemodynamic (increase in heart rate during adenosine infusion), and scan variables (summed stress score) revealed summed stress score (chi-square = 32; p <0.0001) and prescan likelihood of CAD (chi-square = 6.4; p <0.05) as the only independent predictors of severe or extensive CAD. Based on these logistic models, we determined the probability for the presence of severe or extensive CAD in patients with low, intermediate, and high prescan likelihood of CAD across the range of values of a summed stress score. This revealed that there were incremental increases in the probability for severe or extensive CAD both as a function of prescan likelihood of CAD and summed stress score. A severely abnormal scan (summed stress score > 8) during adenosine technetium-99m sestamibi myocardial perfusion SPECT had a high sensitivity of 91% and a moderately high specificity of 70% for identifying high-risk women with severe or extensive CAD. These results coupled with the previously defined prognostic significance of these findings suggest this test to be a useful diagnostic tool for the evaluation of CAD in women.

Adenosine↗
PubMed1997

Usefulness of hemodynamic changes during adenosine infusion in predicting the diagnostic accuracy of adenosine technetium-99m sestamibi single-photon emission computed tomography (SPECT).

Whether adenosine myocardial perfusion single-photon emission computed tomography (SPECT) remains accurate for detecting coronary artery disease (CAD) in the absence of peripheral hemodynamic changes is unknown. To assess the hemodynamic correlates of perfusion defects, we studied 222 consecutive patients (age 71 +/- 11 years) without prior myocardial infarction or revascularization who underwent adenosine technetium (Tc)-99m sestamibi myocardial perfusion SPECT and cardiac catheterization within 6 months of adenosine study. The SPECT protocol used separate acquisition of rest thallium-201 and adenosine Tc-99m sestamibi, which was semiquantitatively analyzed in 20 segments with a visual 5-point scoring system (0 = normal, 4 = absent uptake). The overall sensitivity, specificity, and predictive accuracy of adenosine Tc-99m sestamibi SPECT for detecting significant CAD were 93% (159 of 171), 73% (37 of 51), and 88% (196 of 222), respectively. The study population was grouped into 6 categories as a function of peripheral hemodynamic changes: (1) increase in heart rate by < or = 10 beats/min (n = 135); (2) increase in heart rate by > 10 beats/min (n = 87); (3) decrease in systolic blood pressure by < or = 10 mm Hg (n = 108); (4) decrease in systolic blood pressure by > 10 mm Hg (n = 114); (5) increase in heart rate by < or = 10 beats/min and decrease in systolic blood pressure by < or = 10 mm Hg (n = 72); and (6) increase in heart rate by > 10 beats/min or decrease in systolic blood pressure by > 10 mm Hg (n = 150). The sensitivity, specificity, and predictive accuracy of adenosine sestamibi SPECT were similar in all 6 categories. The prevalence of left main or multivessel CAD and extent of scan abnormality were also similar among all groups. Thus, the diagnostic accuracy of adenosine Tc-99m sestamibi SPECT is high in patients with or without peripheral hemodynamic evidence of adenosine effect.

Adenosine↗
PubMed1997

Quantitative LVEF and qualitative regional function from gated thallium-201 perfusion SPECT.

UNLABELLED: This study investigates the feasibility of routine clinical 201Tl gated perfusion SPECT (gated Tl), and compares quantitative left ventricular ejection fraction (LVEF) and visually-assessed regional wall motion and thickening to analogous values obtained from 99mTc-sestamibi gated perfusion SPECT (gated MIBI). METHODS: We studied 121 patients with a rest gated Tl (3-3.5 mCi, 35 sec/ projection/poststress gated MIBI (25-30 mCi, 25 sec/projection) separate dual-isotope protocol on a 90 degrees dual-detector camera. Automatic quantitation of LVEFs was accomplished using previously developed and validated software, while visual scoring of motion and thickening was performed using four-point scales. RESULTS: Average myocardial counts were lower in gated Tl images (306 +/- 81 counts/pixel) compared to gated MIBI images (789 +/- 237 counts/pixel). The quality of gated Tl images was ranked as excellent, good, fair and poor in 24.0%, 42.1%, 24.8% and 9.1%, respectively, of the patients, compared to 43.0%, 43.8%, 9.1% and 4.1%, respectively, for gated MIBI images. Quantitative-gated Tl and gated MIBI LVEFs correlated well (y = 0.11 + 1.05x, r = 0.918, SEE = 6.35). Possible poststress myocardial stunning may have caused gated Tl LVEFs to overestimate gated MIBI LVEFs by a larger (p = 0.03) amount in ischemic patients (n = 47, y = -0.69 + 1.09x, r = 0.914, s.e.e. = 6.44) compared to nonischemic patients (n = 64, y = -1.58 + 1.05x, r = 0.919, s.e.e. = 5.93), the residual difference in LVEFs for this latter group being likely due to different isotope resolution in conjunction with small left ventricles. Exact agreement between gated Tl and gated MIBI segmental myocardial function in 41 nonischemic patients was 92.2% (kappa = 0.619) and 95.4% (kappa = 0.586) for motion and thickening scores, respectively. CONCLUSION: Thallium-201 gated SPECT imaging can be effectively performed on the majority of patients in our clinical environment and offers the opportunity to assess both myocardial perfusion and function using one injection and one imaging sequence, similarly to what is done with 99mTc-based agents.

Aged↗
PubMed1997

Clinical validation of automatic quantitative defect size in rest technetium-99m-sestamibi myocardial perfusion SPECT.

UNLABELLED: We examined the relationships of automatic quantitative perfusion defect size and defect severity to rest left ventricular ejection fraction and semiquantitative visual sestamibi defect size in rest 99mTc-sestamibi SPECT in 40 consecutive patients with a history of myocardial infarction more than 30 days prior to testing. The purpose of this investigation was to validate the use of automatic quantitative rest sestamibi SPECT as a clinical measure of assessing relative infarction size. METHODS: All patients received 20-30 mCi of 99mTc-sestamibi followed by SPECT imaging. Quantitative defect analysis used previously developed resting normal limits and an automatic version of a commercially available quantitative program (CEqual). Semiquantitative visual defect interpretation used a 20 segment/scan and five-point scoring analysis. First-pass (FP) radionuclide ventriculography (RVG) and gated sestamibi perfusion SPECT were each performed in 31 patients. RESULTS: LVEF assessed by FP RVG was 37% +/- 15% (range 14%-62%) and 37% +/- 16% (range 12%-63%) by gated perfusion SPECT with high linear correlation (r = 0.96, n = 22) between the two methods. Myocardial perfusion defect size was 24% +/- 15% of LV (range 0%-50%) and defect severity was 1103 +/- 864 (range 0 to 2825) by automatic quantitative rest sestamibi. Perfusion defect size and defect severity both had close correlations with LVEF by FP RVG (r = -0.78, r = -0.86) and by gated perfusion SPECT (r = -0.75, r = -0.79). High linear correlations were observed between quantitative defect size and summed visual score of segments with score > or = 2 (r = 0.82) and the number of visually abnormal segments (r = 0.77), as well as between defect severity and visual summed rest score (r = 0.86) and the number of visually abnormal segments (r = 0.76). CONCLUSION: Quantitation of rest sestamibi SPECT defect extent and severity using automatic CEqual correlates well with rest LVEF and with semiquantitative expert visual analysis. Results of this study define a strong relationship between measurements of 99mTc-sestamibi perfusion defect as measured by an automatic software program and global left ventricular function. The automatic quantitative program appears to be a useful measure of assessing infarct size in patients with remote myocardial infarction.

Adult↗
PubMed1996

Adenosine technetium-99m sestamibi myocardial perfusion SPECT in women: diagnostic efficacy in detection of coronary artery disease.

OBJECTIVES: This study sought to assess the diagnostic efficacy of adenosine technetium-99m sestamibi myocardial perfusion single-photon emission computed tomography (SPECT) in a consecutive series of female patients. BACKGROUND: The utility of adenosine myocardial perfusion SPECT for the detection of coronary artery disease is not well defined in women because most studies have described a predominantly male population with a high prevalence of coronary artery disease. METHODS: Of the 201 consecutive female patients in the study group who had undergone adenosine Tc-99m sestamibi myocardial perfusion SPECT, 130 had coronary angiography within 2 months of the nuclear test, and the other 71 had a low likelihood (<10%, mean [+/-SD] 5 +/- 3%) of coronary artery disease. The SPECT protocol used separate acquisition of rest thallium-201 and adenosine Tc-99m sestamibi and was visually analyzed in 20 segments with a semiquantitative five-point scoring system (0=normal; 4=absent uptake). RESULTS: The normalcy rate in patients with a low likelihood of coronary artery disease was 93% (66 of 71). Among the catheterized group, the overall sensitivity, specificity and predictive accuracy of adenosine sestamibi SPECT for detecting coronary artery disease (> or = to 50% diameter stenosis) were 93% (87 of 94), 78% (28 of 36) and 88% (115 of 130), respectively. In the 103 patients without a prior myocardial infarction, the sensitivity, specificity and predictive accuracy were 91% (61 of 67), 78% (28 of 36) and 86% (89 of 103), respectively, for detecting > or = to 50% diameter stenosis. Of particular interest, the sensitivity and specificity were as high in patients with nonanginal symptoms (93% and 69%, respectively) as in patients with angina (92% and 83%, respectively, p=NS). The sensitivity and specificity among patients with a relatively low (<25%), intermediate (between 25% and 75%) or high prescan likelihood of coronary artery disease (>75%) were similar: 82% and 82%, 93% and 73%, and 95% and 100%, respectively. The sensitivity and specificity for detecting individual diseased vessels (> or = to 50% diameter stenosis) were, respectively, 76% and 81% for the left anterior descending coronary artery, 44% and 90% for the left circumflex coronary artery and 75% and 77% for the right coronary artery. CONCLUSIONS: Adenosine Tc-99m sestamibi SPECT is an efficient protocol with high sensitivity and specificity for the detection of coronary artery disease in women irrespective of presenting symptoms or pretest likelihood of coronary artery disease and a high normalcy rate. These findings are of particular clinical relevance because chest pain, anginal or otherwise, has been shown to be a frequent but a less specific marker for coronary artery disease among female patients.

Adenosine↗
PubMed1996

Exercise myocardial perfusion SPECT in patients without known coronary artery disease: incremental prognostic value and use in risk stratification.

BACKGROUND: We evaluated the incremental prognostic value, the role in risk stratification, and the impact on patient management of myocardial perfusion single-photon emission computed tomography (SPECT) in a population of patients without prior myocardial infarction, catheterization, or revascularization. METHODS AND RESULTS: We examined 2200 consecutive patients who at the time of their dual-isotope SPECT had not undergone catheterization, coronary artery bypass surgery, or percutaneous transluminal coronary angioplasty and had no known history of previous myocardial infarction. Follow-up was performed at a mean of 566 +/- 142 days (97% complete) for hard events (cardiac death and myocardial infarction) and for referral to cardiac catheterization or revascularization within 60 days after nuclear testing. Examination of clinical, exercise, and nuclear models by use of pre-exercise tolerance test (ETT), post-ETT, and nuclear information using a stepwise Cox proportional hazards model and receiver-operating characteristic curve analysis revealed that nuclear testing added incremental prognostic value after inclusion of the most predictive clinical and exercise variables (global chi2 = 12 for clinical variables; 31 for clinical + exercise variables; 169 for nuclear variables; gain in chi2, P < .0001 for all; receiver-operating characteristic areas: 0.66 +/- 0.04 for clinical, 0.73 +/- 0.04 for clinical + exercise variables, 0.87 +/- 0.03 for nuclear variables, P = .03 for gain in area with exercise variables; P < .001 for increase with nuclear variables). Multiple logistic regression analysis revealed that scan information contributed 95% of the information regarding referral to catheterization with further additional information provided by presenting symptoms and exercise-induced ischemia. Referral rates to early catheterization and revascularization paralleled the hard event rates in all scan categories - very low referral rates in patients with normal scans and significant increases in referral rates as a function of worsening scan results. Even after stratification by clinical and exercise variables such as the Duke treadmill score, pre- and post-ETT likelihood of coronary artery disease, presenting symptoms, sex, and age, the nuclear scan results further risk-stratified the patient subgroups, thus demonstrating clinical incremental value. CONCLUSIONS: In a patient population with no evidence of previous coronary artery disease at overall low risk (1.8% hard event rate), myocardial perfusion SPECT adds incremental prognostic information and risk-stratifies patients even after clinical and exercise information is known. It appears that referring physicians use this test in an appropriate manner in selecting patients to be referred to catheterization or revascularization.

Cardiac Catheterization↗
PubMed1996

Identification of severe and extensive coronary artery disease by automatic measurement of transient ischemic dilation of the left ventricle in dual-isotope myocardial perfusion SPECT.

OBJECTIVES: This study sought to assess whether a transient ischemic dilation ratio, determined from automatically derived stress and rest left ventricular volumes during stress technetium-99m (Tc-99m) sestamibi/rest thallium-201 dual-isotope myocardial perfusion single-photon emission computed tomography (SPECT), is useful for the identification of patients with severe and extensive coronary artery disease. BACKGROUND: Transient ischemic dilation of the left ventricle on stress/redistribution thallium-201 scintigraphy has been shown to be a clinically useful marker of severe and extensive coronary artery disease. However, in practice, its assessment is highly subjective. This study automatically assessed the transient ischemic dilation ratio on the basis of a previously described algorithm to estimate three-dimensional ventricular boundaries. METHODS: Normal limits for the transient ischemic dilation ratio were developed using data from 54 patients with a low likelihood (< 5%) of coronary artery disease, and criteria for abnormality were developed based on data from 97 who under-went catheterization, of whom 34 had severe and extensive coronary artery disease, defined as > or = 90% stenosis in the proximal left anterior descending coronary artery or in two or more coronary arteries, and 63 had no coronary artery disease (15 patients) or mild to moderate coronary artery disease (48 patients). The criteria were then tested in a validation cohort of 77 additional patients who underwent catheterization, of whom 36 had severe and extensive coronary artery disease. The quantitative results of the dilation ratio were compared with the visual results of the dilation ratio and perfusion defect analysis. RESULTS: For normal limits, receiver operating characteristic curve analysis showed that abnormal transient ischemic dilation ratio values corresponded to left ventricular endocardial volume ratios > 1.22 (mean +/- 2 SD). Transient ischemic dilation assessment using these criteria for abnormality showed high sensitivity (24 [71%] of 34) and very high specificity (60 [95%] of 63) for severe and extensive coronary artery disease. When the analysis was applied to the prospective catheterization group, similar sensitivity and specificity for severe and extensive coronary artery disease were observed (77% and 92%, respectively). Significant agreement (p = 0.0001) was found between the degree of transient ischemic dilation and the Tc-99m sestamibi defect extent, the latter assessed by semiquantitative visual analysis (summed stress score). CONCLUSIONS: The automatic measurement of transient ischemic dilation in dual-isotope myocardial perfusion SPECT is a clinically useful marker that is sensitive and highly specific for detection of severe and extensive coronary artery disease.

Aged↗
PubMed1996

Effective risk stratification using exercise myocardial perfusion SPECT in women: gender-related differences in prognostic nuclear testing.

OBJECTIVES: This study was designed to evaluate the incremental prognostic value over clinical and exercise variables of rest thallium-201/exercise technetium-99m sestamibi single-photon emission computed tomography (SPECT) in women compared with men and to determine whether this test can be used to effectively risk stratify patients of both genders. BACKGROUND: To minimize the previously described gender-related bias in the evaluation of coronary artery disease in women, there is a need to identify a noninvasive testing strategy that is able to accurately and effectively risk stratify women. METHODS: We identified 4,136 consecutive patients (2,742 men, 1,394 women) who underwent dual-isotope SPECT. The incremental value of nuclear testing was determined using both a stepwise Cox proportional hazards model and Kaplan-Meier survival analysis. Receiver operating characteristic curve analysis was performed to determine test discrimination for high risk patients in men and women. RESULTS: The patient population was followed up for 20 +/- 5 months for events (cardiac death or nonfatal myocardial infarction). During this time, 63 myocardial infarctions and 32 cardiac deaths occurred in the men, and 31 myocardial infarctions and 14 cardiac deaths occurred in the women. Nuclear testing significantly stratified both men and women irrespective of their rest electrocardiogram. Cox proportional hazards analysis revealed that nuclear testing added incremental prognostic value in both men and women after inclusion of the most predictive clinical exercise variables (overall chi-square 89 in men vs. 120 in women, p < 0.005). Kaplan-Meier survival analysis demonstrated that nuclear testing further stratified men and women with both intermediate to high and low prescan likelihoods of coronary artery disease (p < 0.005 for all). Receiver operating characteristic curve analysis demonstrated superior discrimination for the nuclear scan results in identifying high risk women than men (area under the curve: 0.84 +/- 0.03 vs 0.71 +/- 0.03 in men, p < 0005). The odds ratio comparing event rates in patients with women than in men, suggesting superior stratification using nuclear testing in women. CONCLUSIONS: Dual-isotope myocardial perfusion imaging yields incremental prognostic value in both men and women. This modality identifies low risk women and men equally well but relatively high risk women more accurately than relatively high risk men and, thus, is able to stratify women more effectively than men.

Bias↗
PubMed1996

Impact of myocardial perfusion single-photon emission computed tomography on referral to catheterization of the very elderly. Is there evidence of gender-related referral bias?

OBJECTIVES: This study sought to assess the impact of myocardial perfusion studies on subsequent management in the very elderly with respect to referral to catheterization or revascularization. BACKGROUND: The very elderly are a rapidly growing segment of the U.S. population, and myocardial perfusion studies are frequently performed in this patient subset for evaluation of coronary artery disease. METHODS: The study utilized 1,006 consecutive patients > or = 80 years old (511 men, 495 women) who underwent stress myocardial perfusion single-photon emission computed tomography (SPECT) using pharmacologic stress (n = 605) or treadmill exercise (n = 401). Referral to catheterization or revascularization within 60 days of the nuclear scan was correlated with clinical and nuclear variables. RESULTS: Catheterization and revascularization were performed in 119 and 77 patients, respectively. Stratification of referral rates showed a low rate in normal and mildly abnormal scan categories and significantly higher rates in patients with severely abnormal scan results irrespective of the presenting symptoms or pretest likelihood of coronary artery disease. Multiple logistic regression analysis of clinical and nuclear variables revealed that extent and severity of reversibility by SPECT and the final scan result were the two most powerful predictors of referral to catheterization and revascularization in men and women (catheterization: chi-square 65 and 78; revascularization: chi-square 37 and 68, respectively). Overall, referral rates to catheterization and revascularization were similar in men and women (catheterization: 13% vs. 11%; revascularization: 8% vs. 8%, respectively). However, women with severely abnormal scan results were more frequently referred to catheterization (28% vs. 18%, p < 0.03) and revascularization (21% vs. 12%, p < 0.01) than men. CONCLUSIONS: In patients > or = 80 years old, myocardial perfusion SPECT had a significant impact on patient management. The apparent discrepancy in referral rates for interventional management in men and women is unexplained but may be appropriate in light of our previous observations that women with severely abnormal scan results are at increased risk for hard cardiac events than are men with severely abnormal scan results.

Age Factors↗
PubMed1995

Gender-related differences in clinical management after exercise nuclear testing.

OBJECTIVES: This study sought to determine the rate of referral to cardiac catheterization in men and women early after nuclear testing as a function of the magnitude of myocardial ischemia by radionuclide perfusion imaging. BACKGROUND: Although many previous studies have suggested that gender-related differences are present in the clinical management of coronary artery disease, the presence of such a difference with respect to referral to catheterization after noninvasive testing is disputed. METHODS: We examined 3,211 consecutive patients (1,074 women, 2,137 men) who underwent exercise dual-isotope single-photon emission computed tomography and had follow-up evaluation performed at least 1 year after nuclear testing (mean [+/- SD] follow-up 19 +/- 5 months) for "hard" events (cardiac death and myocardial infarction) and referral to cardiac catheterization or revascularization within 60 days of nuclear testing. Multiple logistic regression analysis was performed to determine the best predictors of referral to catheterization as well as to examine whether gender itself added further information to this model. RESULTS: Although men were referred to catheterization more frequently than women (10.6% vs 7.1%, p < 0.001) early after exercise nuclear testing, there were no differences in the rate of referral to catheterization or revascularization after stratification by the amount of abnormally perfused myocardium detected by the nuclear scan. Both men and women with normal scan results were infrequently referred to subsequent catheterization. In the setting of severe ischemia, women were referred to catheterization more frequently than men. This higher rate appears to be clinically appropriate because women with severely abnormal scan results had a significantly higher event rate than men (17.5% vs. 6.3%, p < 0.0001). This greater risk in women than in men appeared to be underappreciated because the increased rate of hard events in women with severely abnormal scan results was out of proportion to the smaller increase in their rate of referral to cardiac catheterization. Although gender added information to the multivariate model most predictive of referral to catheterization models when nuclear variables were not included, when nuclear variables were considered, the addition of gender added no further significant information. This finding suggests that adjusting for differences in perfusion scan abnormalities by the use of nuclear testing eliminated the apparent gender-related referral bias. CONCLUSIONS: After controlling for differences in perfusion scan abnormalities, no gender-related referral bias to catheterization was present. In the setting of severe ischemia, women had a greater rate referral to catheterization than men. As a function of risk, both men and women were appropriately referred to catheterization at a low rate when the scan result was normal. However, because women with severe perfusion abnormalities had a greater rate of cardiac death and myocardial infarction then men, women in this high risk subgroup were underreferred to catheterization relative to men. This finding points to the need to better identify women at high cardiac risk.

Aged↗
PubMed1995

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.

Adult↗
PubMed1995

Clinical applications of exercise nuclear cardiology studies in the era of healthcare reform.

The challenge for nuclear cardiology is to demonstrate that it can provide more information than competitive modalities at comparable or lower cost. In considering patients for nuclear cardiology procedures, presentations can be divided into 9 subsets: within each subset, nuclear cardiology tests should be employed where incremental information is provided over the information available without performing the test. (1) Patients with no known coronary artery disease (CAD); for diagnosis, nuclear imaging is useful in patients with intermediate probability of CAD. For prognosis, assessment is based on extent of ischemia, where we have shown that nuclear testing provides incremental information, especially in patients with a high likelihood of CAD, such as those with typical angina. In the remaining categories (2-9), nuclear cardiology studies are predominantly used for purposes of risk stratification. Here the greatest value is in patients deemed to be at intermediate risk before nuclear testing. (2) Postmyocardial infarction: stress nuclear imaging provides an alternative to angiography for risk assessment of clinically uncomplicated patients. (3) Poor ventricular function: Nuclear testing is particularly useful for differentiating patients with hibernating myocardium (the defect is reversible), with stunned myocardium (no defect is present), or with myocardial infarction (the defect is persistent). (4) Unstable angina: Following current federal guidelines, nuclear imaging in medically stabilized low-to-intermediate risk patients with unstable angina is likely to increase. (5) Postcatheterization patients: Nuclear imaging is useful when there is uncertainty regarding the choice of medical management or revascularization. (6) Pre-noncardiac surgery patients: Nuclear imaging is clearly helpful in patients with intermediate clinical risk and may provide useful information in clinically high-risk patients. (7) Post-PTCA patients: Due to the intermediate likelihood of restenosis, nuclear scans are frequently employed 2-6 months following intervention. (8) Post-CABG patients: We have demonstrated that exercise scintigraphy (SPECT) provides incremental prognostic information over clinical and exercise electrocardiographic results and is useful when clinical risk of events is considered intermediate. (9) Long-term management: Scintigraphy provides objective information regarding progression or regression of CAD.

Angina, Unstable↗