The efficacy of cardiovascular nuclear medicine exercise studies

Prospective diagnostic performance of semiconductor SPECT myocardial perfusion imaging: wall thickening analysis reduces the need for an additional prone acquisition

PURPOSE

To determine whether the assessment of regional wall thickening (WT) in addition to myocardial perfusion from stress supine acquisitions could compensate for the lack of prone acquisition and the corresponding decrease in the diagnostic performance of SPECT myocardial perfusion imaging (MPI) in patients with known or suspected coronary artery disease (CAD).

METHODS

The study group comprised 41 patients (123 vessels) with known or suspected CAD prospectively recruited for systematic prone and supine ²⁰¹Tl stress SPECT MPI. The diagnostic performance of SPECT MPI was determined for various image sets including nongated supine images (supine NG), nongated combined prone and supine images (prone and supine NG) and gated supine images, allowing WT evaluation from NG images in addition to perfusion (supine NG + WT) using invasive coronary angiography and fractional flow reserve as the gold standards.

RESULTS

The rate of false positives was significantly higher among the supine NG images (20.8%) than among either the prone and supine NG or the supine NG + WT images (3.3% and 2.7%, respectively, P < 0.05 vs. supine NG). Consequently, specificity was higher for the prone and supine NG images than for the supine NG images (96.1% vs. 76.1%, P < 0.01) and was highest for the supine NG + WT images (96.8%, P not significant vs. prone and supine NG), without significant differences in sensitivity (80.0%, 86.6% and 73.3%, respectively, P not significant for all comparisons).

CONCLUSION

The diagnostic performance of supine stress SPECT MPI is improved when WT assessment of ischaemic segments is used as an additional diagnostic criterion to values not significantly different from those with combined prone and supine acquisitions.

Comparative accuracy of supine-only and combined supine-prone myocardial perfusion imaging in men

BACKGROUND

Combined supine-prone myocardial perfusion imaging (CSP MPI) has been shown to reduce attenuation artifact in comparison to supine-only (SU) MPI in mixed-gender populations with varying risk for coronary artery disease (CAD), often where patients served as their own controls. However, there is limited direct comparison of these imaging strategies in men.

METHODS

934 male patients underwent CSP or SU MPI. Diagnostic certainty of interpretation was compared. Within the cohort, 116 were referred for left heart catheterization (LHC) to assess for CAD. Sensitivity, specificity, and area under the curve (AUC) were compared with additional analysis based on body mass index (BMI).

RESULTS

597 patients completed the SU protocol and 337 patients completed the CSP protocol. Equivocal studies were seen more frequently in the SU group (13%) than in the CSP group (4%, P < .001). At catheterization, the specificity for CSP MPI of 70% was higher than 40% for SU MPI (P = .032). The CSP AUC (0.80 ± 0.06) was significantly larger than SU AUC (0.57 ± 0.05, P = .004). CSP specificity was significantly higher in obese patients.

CONCLUSIONS

CSP MPI increases diagnostic certainty and improves test accuracy for CAD detection in men with CAD risk factors, especially obese patients, compared to SU MPI.

Observer Variability of Radionuclide Left Ventricular Volume Determination at Rest and during Exercise

The reproducibility expressed as the intra- and interobserver variation in the determination of cardiac left ventricular (LV) volumes by the radionuclide multigated equilibrium technique in the upright position is presented. No systematic difference was found in the reproducibility between LV volumes determined in healthy subjects and cardiac patients or between examinations performed at rest and during exercise. The intra- and interobserver variation were of the same magnitude. SD of the difference was 8 to 9 ml for LV end-diastolic volume, 4 to 7 ml for LV end-systolic volume, and 2 to 5% for LV ejection fraction. Thus, there is a 95% probability that repeat measurements, either by the same observer or by 2 independent observers, will result in the same LV end-diastolic volume within 18 ml, LV end-systolic volume within 11 ml, and LV ejection fraction within 8%. Only 15% of the variation can be ascribed to determination of the attenuation correction factor.

Effectiveness of (99m)Tc-tetrofosmin for assessment of heart functions in micropigs

This study examined the suitability of a nuclear imaging technique using ^99mTc-tetrofosmin as an agent to assess the heart functions of healthy micropigs. The mean age of the pigs was 360 days (male), and the mean body weight was 35.3 kg ranging from 34.5-36 kg. There were no significant perfusion defects in any of the reconstructed images. Gated single-photon emission computed tomography imaging can be used to calculate the ventricular volume and ejection fraction (EF). In this case, an EF of 79% was calculated from the ventricular volume of the end-systolic image (10 ml) subtracted from that of the end-diastolic volume (49 ml). A perfusion defect (particularly the apex, lateral wall) is unlikely because of the presence of a preserved wall motion in a segment with a defect. It is concluded that quantitative cardiac scintigraphy, using ^99mTc-tetrofosmin is an adequate technique for estimating the heart functions of healthy micropigs.

Comparative Use of Radionuclide Stress Testing, Coronary Artery Calcium Scanning, and Noninvasive Coronary Angiography for Diagnostic and Prognostic Cardiac Assessment

Noninvasive cardiac imaging has undergone a recent resurgence with the development of new approaches for imaging coronary atherosclerosis. Non-contrast computed tomography (CT) for imaging the extent of coronary artery calcification (CAC) and contrast CT for noninvasive coronary angiography (CTA) are developments with a growing evidence base regarding risk assessment and the diagnosis of obstructive coronary disease. This review discusses the role of CAC for risk assessment of asymptomatic individuals and for the use of coronary CTA in symptomatic patients. By comparison, gated myocardial perfusion scintigraphy (MPS) is a well-established noninvasive imaging modality that is a core element in evaluation of patients with stable chest pain syndromes. Stress MPS is the most commonly used stress imaging technique for patients with suspected or known coronary disease. In contrast to the nascent evidence noted with coronary CTA, MPS has a robust evidence base, including the support of numerous clinical guidelines. We highlight the current evidence supporting the diagnostic accuracy and risk stratification data for MPS for symptomatic patients with known or suspected coronary artery disease. It is likely that assessing the extent of atherosclerosis using CAC or coronary CTA will become an increasing part of mainstream cardiovascular imaging practices. In some patients, further ischemia testing with MPS will be required. Similarly, in some patients referred for MPS, anatomic definition of atherosclerosis using CAC by CT may be appropriate. Thus, this review also provides a synopsis of the available literature on imaging that integrates both CT and MPS in combined strategies for the assessment of atherosclerotic and obstructive coronary disease burden. We also propose possible risk-based strategies through which imaging might be used to identifying candidates for more intensive prevention and risk factor modification strategies as well as those who would benefit from referral to coronary angiography and revascularization.

Diagnostic accuracy of gated Tc-99m sestamibi stress myocardial perfusion SPECT with combined supine and prone acquisitions to detect coronary artery disease in obese and nonobese patients

BACKGROUND

The diagnostic value of gated myocardial perfusion single-photon emission computed tomography (MPS) with combined supine and prone acquisitions to detect coronary artery disease (CAD) in obese and nonobese patients has not been defined.

METHODS AND RESULTS

We studied 1511 patients without prior myocardial infarction or coronary revascularization who either had coronary angiography within 3 months of MPS (n = 785) or had a low pretest likelihood of CAD (n = 726). All patients underwent rest thallium 201/gated exercise or adenosine stress technetium 99m sestamibi MPS in both the supine and prone positions. According to body mass index (BMI), patients were categorized as normal weight (BMI of 18.5-24.9 kg/m2), overweight (BMI of 25.0-29.9 kg/m2), or obese (BMI > or = 30.0 kg/m2). There were no significant differences in stress, fixed, or ischemic defects among patients in different weight categories. The sensitivity of MPS was 85%, 86%, and 89% for detecting patients with 50% or greater coronary stenosis and 89%, 91%, and 92% for detecting those with 70% or greater coronary stenosis in the normal-weight, overweight, and obese groups, respectively. Normalcy rates were nearly identical among the 3 weight groups (99%, 98%, and 99%, respectively). Multivariate logistic regression analysis further confirmed that BMI was a nonsignificant predictor for the detection of CAD. In a subset of 290 patients, automated quantitative MPS analysis confirmed that combined supine and prone MPS increased specificity (86%) in identifying CAD, without a significant reduction in sensitivity (83% for > or = 50% stenosis and 88% for > or = 70% stenosis).

CONCLUSION

The findings of this study suggest that MPS performed with gating and combined supine and prone acquisitions without attenuation correction had a similar diagnostic accuracy for the detection of CAD in normal-weight, overweight, and obese patients.

Usefulness of the exercise electrocardiogram in diagnosing ischemic or coronary heart disease in patients with chest pain

We compared exercise electrocardiograms with myocardial perfusion images and coronary angiograms in 186 patients who had been referred to coronary angiography for stable angina pectoris. All had normal electrocardiographic findings at rest, and none had undergone coronary revascularization. Sensitivity, specificity, and positive and negative predictive values with the exercise electrocardiogram for prediction of reversible and/or irreversible hypoperfusion were 58%, 89%, 76%, and 77% and 70%, 88%, 72%, and 87%, respectively, for prediction of reversibility only. Corresponding values for comparison with coronary angiography were 65%, 89%, 74%, and 83%, respectively. Sensitivities were considerably lower in women than in men. Exercise electrocardiographic findings were normal in 50% of women and 25% of men who had reversible perfusion defects.

Impaired left ventricular diastolic function during isometric exercise in asymptomatic patients with hyperlipidaemia

BACKGROUND

Left ventricular (LV) diastolic dysfunction is an early sign, and may be more sensitive indicator, of ischaemic heart disease (IHD) than systolic dysfunction.

METHODS

LV diastolic function was assessed during isometric exercise (IME) in 37 consecutive normotensive hyperlipidaemics (LIP), without cardiac history or symptoms. Each patient underwent a stress ECG test and 2-D echo and Doppler cardiography. During the latter, transmitral flow at rest and at peak standardised IME using handgrip was studied. From the tracings, the E/A (peak velocity of the early/atrial components), the contribution of atrial systole to LV filling (ACF), the deceleration time (DT) of the E wave and the isovolumic relaxation time (IVRT) were calculated. Results were compared to 37 age-matched normal healthy volunteers (NOR).

RESULTS

Resting E/A was not different between NOR and the LIP. A significant reduction in E/A with IME was observed in LIP but not in NOR. Impaired LV filling (shown by E/A<1) was demonstrated in five patients (13%) at rest and in 20 patients (54%) at peak IME. All NOR had E/A>1 suggesting normal LV filling. Fifteen of the 30 patients with negative stress ECG test demonstrated LV diastolic dysfunction. ACF was higher in LIP than NOR and increased significantly (P<0.005) by 23% during IME. DT and IVRT in LIP were not different from NOR. In neither NOR nor LIP, were the LV diastolic functional parameters related to gender, smoking habit or levels of total cholesterol, LDL- or HDL-cholesterol or triglycerides.

CONCLUSION

The prevalence of LV diastolic dysfunction in asymptomatic patients with hyperlipidaemia despite a negative stress ECG test may be evidence of early underlying pre-clinical myocardial ischaemia.

Contemporary management of chronic stable angina

Chronic stable angina is a common condition with a prognosis that is less benign than is generally appreciated. The optimal treatment strategy of this disorder is unclear, and few anti-ischaemic agents have been rigorously tested in prospectively randomised mortality studies. The evidence base for the anti-ischaemic therapy of chronic angina draws upon data 'borrowed' from studies in acute coronary syndromes, and from studies in chronic angina using surrogate endpoints such as ambulatory silent ischaemia. Such evidence leads us to believe that anti-ischaemic therapy with beta-blockers offers a mortality benefit in chronic angina. In contrast, the mortality benefit of lipid lowering therapy and antiplatelet agents is well proven. Angioplasty offers no mortality benefit in the treatment of chronic angina, although it is more effective than medical therapy alone for the relief of symptoms. In a few patients with high order proximal coronary disease, coronary bypass surgery offers a distinct mortality advantage compared with medical treatment alone. Most patients, however, do not warrant such an approach, and only require surgery for when they remain symptomatic despite adequate medical therapy. Alternative strategies such as cardiac transplantation, transmyocardial laser revascularisation and spinal cord stimulation are now accepted in a subgroup of patients for the treatment of chronic angina refractory to standard therapy.

[Tomographic studies of myocardial perfusion normality with 99m Tc-Tetrofosmin. Spanish multicenter study]

This objective of this study was to obtain a pool of Myocardial Perfusion SPECTs with a 99mTetrofosmin stress/rest one day protocol in normal volunteers having a less than or equal to 5% likelihood of coronary artery disease that represents normalcy in the Spanish population. A total of 169 volunteers from 15 hospitals were studied. The volunteers were divided into 5 groups: Groups 1, 2 or 3 corresponding to men < 30 years (n = 33), men between 30 and 50 years (n = 32), or men > 50 years (n = 31); Groups 4 or 5: premenopausal (n = 38) or postmenopausal women (n = 35). A clinical history, physical examination, clinical laboratory parameters, echocardiography and a symptom limited exercise stress test were performed in all of them and had to be normal. The mean likelihood of coronary artery disease was 1.15 +/- 1.07%.Twenty-four segments were analyzed in each study and were classified into 5 grades of uptake (1 = normal, 2, 3, 4 = mild, moderate or severe defect and 5 = no uptake). Defects were then analyzed according to sex and location. Considering the stress and rest studies separately (8,112 segments), only 19 moderate and 75 mild defects were found, these corresponding to 16 volunteers, with more inferior defects in men and anterior defects in women. These data validate the normalcy of our population. A pool of Myocardial Perfusion SPECTs with a 99mTetrofosmin stress/rest one day protocol in normal volunteers that represents Spanish normal values was obtained.

Principles for combining radionuclide and echocardiographic stress imaging into a single clinical laboratory service

Physicians who supervise stress-imaging procedures, whether they be stress nuclear or stress echocardiography tests, are increasingly required to incorporate important principles in the interpretation of the test results. Important guiding principles, common to these tests, are reviewed in this article. The principles include the following: avoiding categorical interpretation of test results; identifying equivocal test responses; combining diagnostic and prognostic information in rendering information to referring physicians; integrating the stress test results with other clinical data and using Bayesian analysis as a decision-aid; reporting one's confidence in the interpretation of the results of testing; characterizing both the extent and severity of any induced myocardial ischemia; and analyzing the test results in a blinded fashion, without prior knowledge of patient clinical history

Comparative ability of myocardial perfusion single-photon emission computed tomography to detect coronary artery disease in patients with and without diabetes mellitus

BACKGROUND

Diabetics generally have more frequent and extensive silent myocardial ischemia than nondiabetics, increasing the importance of noninvasive detection of coronary artery disease (CAD) in this cohort. However, little is known regarding the diagnostic accuracy of myocardial perfusion single-photon emission computed tomography (SPECT) in patients with diabetes. This study was undertaken to compare the diagnostic value of rest thallium-201/stress technetium-99m sestamibi dual-isotope myocardial perfusion SPECT in patients with and without diabetes.

METHODS

Of the 203 patients with diabetes and 260 patients without diabetes who underwent dual-isotope myocardial perfusion SPECT with exercise or pharmacologic stress testing, 138 diabetics (12% type 1 diabetics) and 188 nondiabetics had coronary angiography within 6 months of the nuclear test, and 65 diabetics and 72 nondiabetics had a low likelihood (<10%, mean 6% +/- 3% and 6% +/- 3%) of CAD.

RESULTS

The angiographic data showed that patients with diabetes had less incidence of 1-vessel disease and a higher incidence of 3-vessel/left main artery disease than patients without diabetes (P <.05). The overall sensitivity and specificity, respectively, of SPECT for detecting CAD with the criterion of >/=50% diameter stenosis were 86% (95 of 111) and 56% (15 of 27) in diabetics, 86% (122 of 142) and 46% (21 of 46) in nondiabetics (P = not significant). With the criterion of >/=70% diameter stenosis the corresponding results were 90% (86 of 96) and 50% (21 of 42) in diabetics, and 91% (108 of 119) and 43% (30 of 69) in nondiabetics, respectively (P = not significant). The normalcy rate for low likelihood patients was 89% (58 of 65) in diabetics and 90% (65 of 72) in nondiabetics (P = not significant). The sensitivity and specificity for individual vessel detection were also similar in patients with and without diabetes (P = not significant) except for a lower sensitivity and a higher specificity for detecting left anterior descending coronary artery disease in the diabetic group (P <.05).

CONCLUSION

Dual-isotope myocardial perfusion SPECT has comparable accuracy for the diagnosis of CAD in diabetic and nondiabetic patients.

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.

Myocardial perfusion imaging with technetium-99m sestamibi SPECT in the evaluation of coronary artery disease

Technetium-99m hexakis-2-methoxy-isobutyl-isonitrile (99mTc sestamibi) has been used for myocardial perfusion imaging in the evaluation of coronary artery disease (CAD) since 1990. The experience of its use in an Asian population with and without previous myocardial infarction (MI), diabetes mellitus (DM), hypertension (HPT) and collateral circulation (COL) is reported. One hundred and thirty-nine patients who underwent treadmill exercise testing with 99mTc sestamibi single photon emission computed tomography (SPECT) and coronary angiogram were studied. The overall sensitivity for the detection of CAD was 91.0% and specificity was 64.7%. For patient without previous myocardial infarction, the sensitivity was 83.8% and specificity was 83.3%. Patients with COL had a higher sensitivity while those with HPT had a lower specificity. Sensitivity was higher in patients with multi-vessel disease (MVD) than single vessel disease (SVD). The overall detection for individual artery stenosis was 74.1% with a specificity of 73.1%. Amongst the three major coronary arteries, sensitivity was highest for the right coronary artery and specificity was highest for the left circumflex artery. Specificity was higher in patients without MI or COL. We found that the agreement between 99mTc sestamibi SPECT and coronary angiogram for the extent of CAD was only 52.5%. The concordance rate was higher for patients with MVD than SVD. It is concluded that 99mTc sestamibi SPECT is a sensitive and specific test for the detection of CAD and localization of disease to individual coronary arteries in our patients with some differences in the subgroups. Agreement between coronary angiogram and 99mTc sestamibi for the extent of coronary artery disease was also satisfactory.

Incremental value of simultaneous assessment of myocardial function and perfusion with technetium-99m sestamibi for prediction of extent of coronary artery disease

OBJECTIVES

This study assessed the incremental value of technetium-99m myocardial single-photon emission computed tomography (SPECT) and simultaneous first-pass radionuclide angiography, when added to treadmill exercise, for prediction of the extent of coronary artery disease.

BACKGROUND

Technetium-99m count statistics permit the simultaneous assessment of myocardial perfusion and function. However, whether this characteristic improves prediction of the extent of coronary artery disease remains unknown.

METHODS

We studied 70 consecutive patients who had coronary angiography within 6 months of the scintigraphic study. All patients underwent a symptom-limited treadmill exercise test. Treadmill data were summarized using a previously validated score. Left ventricular ejection fraction and regional wall motion were evaluated from a first-pass radionuclide angiogram acquired at peak treadmill exercise in the anterior view. Perfusion was assessed visually. Extent of angiographic disease was expressed as the presence or absence of multivessel disease (more than two coronary artery territories with > 50% stenosis) and as a score that reflects the location of severe (> 75%) stenosis.

RESULTS

Stepwise addition of scintigraphic data (perfusion first, followed by function) to the treadmill score showed significant incremental value for prediction of the angiographic score at each step; exercise ejection fraction alone was the strongest independent predictor. Discriminant accuracy for detection of multivessel disease was also improved by the addition of perfusion information to the treadmill score and addition of regional wall motion analysis to both of them. In this case, ejection fraction failed to show independent value.

CONCLUSIONS

The addition of simultaneously performed sestamibi perfusion SPECT and first-pass radionuclide angiography to the treadmill exercise test significantly improved prediction of the extent of coronary artery disease.

Pharmacologic stress dual-isotope myocardial perfusion single-photon emission computed tomography

Separate-acquisition rest thallium-201/exercise technetium-99m sestamibi (sestamibi) dual-isotope single-photon emission computed tomography (SPECT) has been shown to be effective for assessment of myocardial perfusion and viability. The present study was designed to validate the dual-isotope approach when used in conjunction with pharmacologic stress. All patients had rest 201TI SPECT followed immediately by adenosine (n = 82) or dipyridamole (n = 50) infusion and sestamibi injection. Sestamibi SPECT was performed 1 hour later. The entire study lasted < 2.5 hours. The patient population was categorized into three groups: 51 consecutive patients with coronary angiography and no previous myocardial infarction (group I), 58 consecutive patients with a low prescintigraphic test likelihood of coronary artery disease (group II), and 23 consecutive catheterized patients with remote Q-wave myocardial infarction (group III). For group I patients, the sensitivity and specificity for dual-isotope SPECT were 92% (35 of 38) and 85% (11 of 13), respectively, when > or = 50% coronary artery narrowing was considered significant and were 97% (34 of 35) and 81% (13 of 16) respectively, when > or = 70% narrowing was considered significant. The normalcy rate among the 58 patients of group II was 96%. Comparisons for pattern of stress-defect reversibility demonstrated that of the 97 stress defects within the infarct zones (group III), 15% were reversible and 85% were nonreversible. In contrast, of the 227 stress defects within the diseased (> or = 50% stenosis) vessel zones of the group I patients, 93% were reversible and 7% were noreversible (p < 0.001 vs group III). In conclusion, separate acquisition rest 201-TI/pharmacologic stress sestamibi dual-isotope SPECT is an efficient myocardial perfusion imaging protocol with high accuracy for detection and assessment of angiographically significant coronary artery disease.

Pathophysiologic factors governing the variability of ischemic responses to treadmill and bicycle exercise

Ischemic responses may vary considerably when patients with coronary artery disease (CAD) are tested serially, but the pathophysiologic mechanisms that govern this variability have not been well evaluated. We thus evaluated whether clinical, hemodynamic, physiologic, and anatomic factors influenced the variability in ischemic responses among 140 patients (mean age 54 +/- 11 years) subjected to both bicycle and treadmill exercise electrocardiography. Radionuclide ventriculography was obtained during bicycle exercise in each patient. The population included 77 patients with CAD, 21 patients with normal coronary arteriograms, and 42 patients with < 5% likelihood of CAD. Bicycle exercise evoked higher systolic blood pressure (p < 0.001) and double-product (p < 0.001) responses compared with treadmill exercise in the patients with CAD and in the normal subjects, and it evoked a lower frequency of chest pain (12% vs 41%, p < 0.001) in the 34 patients with CAD who had ST-segment depression during both exercise tests. There was a high frequency of variability in ischemic responses during treadmill versus bicycle exercise: 22 (39%) of the 56 CAD patients who had exercise-induced ST-segment depression manifested this response during one stress test only. This variability was strongly related to the functional and anatomic magnitude of disease. Ischemic variability decreased progressively as the response of left ventricular ejection fraction (LVEF) to exercise worsened progressively (p = 0.003 by analysis of variance), from 83% in those with an LVEF increase of > 10% with exercise to only 13% in those with an LVEF fall of > or = 5% with exercise.(ABSTRACT TRUNCATED AT 250 WORDS)

Choosing a thallium-201 or technetium 99m sestamibi imaging protocol

During the past decade progress in the field of myocardial perfusion imaging has resulted in a myriad of choices for perfusion imaging protocols, including choices in types of stressor, imaging modality, perfusion tracer, method of analysis, and a wide range of choices of imaging protocols. This review will examine this latter aspect in the context of choices of perfusion tracers that are now available for wide use. Manipulations of thallium protocols have revolved primarily around optimizing identification of stress defect reversibility and regional myocardial viability. The high image quality and long retention time afforded by the technetium-labeled agents allow the potential for streamlining imaging protocols to maximize efficiency and cost-effectiveness, such as performing stress only imaging in a subset of patients and performing simultaneous assessment of perfusion and function.

Is 'silent' myocardial ischemia really as severe as symptomatic ischemia? The analytical effect of patient selection biases

BACKGROUND

The clinical significance of exercise-induced chest pain remains controversial, as reflected by sharply discordant clinical results within the medical literature. Thus, we developed a prospective study to compare the functional significance of silent versus symptomatic ischemia and to evaluate whether patient selection biases influence this analysis.

METHODS AND RESULTS

We evaluated 117 patients (mean age, 63 +/- 9 years) with ischemic ST-segment depression during treadmill testing. Each patient underwent Tl-201 myocardial perfusion single-photon emission computed tomography (SPECT) after exercise followed by 24-ambulatory ECG monitoring. Patients were divided into silent versus symptomatic cohorts and were compared for the degree of hemodynamic, exercise and ambulatory ECG, and thallium abnormalities during stress testing. Analyses were repeated as the patient population became increasingly restricted. Compared with the silent patients, patients with chest pain during exercise had a shorter exercise duration (P < .009), lower peak heart rate (P = .009) and double product (P = .005), lower heart rate threshold for ST depression (P < .05), more episodes of ambulatory ST-segment depression (P < .05), a higher frequency of ischemia abnormalities during Tl-201 SPECT (P = .02), and higher summed Tl reversibility scores (P = .002). As the population became increasingly restricted, the relative magnitude of differences in silent versus symptomatic cohorts diminished, whereas the absolute magnitude of ischemic abnormalities progressively increased in both cohorts. For example, within the restricted group having ischemia on both exercise and ambulatory ECG, 50% of the silent cohort had severe ischemia on Tl SPECT (five or more reversible defects) and more than one third demonstrated the ominous finding of transient left ventricular dilation after exercise.

CONCLUSIONS

The induction of chest pain is associated with substantially more functional abnormalities when it is analyzed in a relatively "broad-spectrum" coronary artery disease population; by contrast, chest pain tends to lose its apparent value as a clinical test parameter when its analysis is restricted to coronary artery disease populations with a greater a priori likelihood of manifesting inducible ischemia. These findings may help resolve some of the previous discordant literature reports.

Left ventricular function during weaning of patients with chronic obstructive pulmonary disease

OBJECTIVE

Determine the evolution of left ventricular ejection fraction during weaning.

DESIGN

Prospective study.

SETTING

Intensive care unit of a university teaching hospital.

PATIENTS AND PARTICIPANTS

12 consecutive mechanically ventilated patients, without documented coronary artery disease, suffering from acute exacerbation of chronic obstructive pulmonary disease and able to be weaned.

MEASUREMENTS AND RESULTS

Left ventricular ejection fraction was determined during mechanical ventilation, inspiratory pressure support (10 cmH2O) and spontaneous ventilation with constant inspiratory oxygen fraction using technetium 99m radionuclide angiography. Spontaneous ventilation induced a significant decrease in left ventricular ejection fraction from 54.5 +/- 12.4 to 47.0 +/- 13% (p < 0.01). Inspiratory pressure support induced a slight but non-significant decrease in left ventricular ejection fraction from 55.0 +/- 12.1 to 50.3 +/- 12.4%. Left ventricular ejection fraction was homogeneously reduced by spontaneous ventilation without patent regional wall motion abnormalities of the left ventricle. Myocardial 201thallium imaging performed 15 min after weaning showed a normal perfusion in the left ventricle anterior and posterior free wall.

CONCLUSION

Weaning of patients suffering from chronic obstructive pulmonary disease without coronary artery disease induced a significant reduction in left ventricular ejection fraction. The non significant decrease in left ventricular ejection fraction observed with inspiratory pressure support suggested that our results might be explained by a weaning induced increase in afterload.

Separate acquisition rest thallium-201/stress technetium-99m sestamibi dual-isotope myocardial perfusion single-photon emission computed tomography: a clinical validation study

OBJECTIVES

This study assessed the validity of a novel approach to myocardial perfusion scintigraphy that provides the opportunity to avoid the drawbacks of standard same-day rest/stress technetium-99m sestamibi myocardial perfusion studies by using separate-acquisition dual-isotope rest thallium-201 and exercise technetium-99m sestamibi single-photon emission computed tomography (SPECT).

BACKGROUND

Standard same-day rest/stress technetium-99m sestamibi myocardial perfusion studies are cumbersome, associated with a potential decrease in perceived stress defect severity compared with thallium-201 due to the presence of rest technetium-99m sestamibi and may be unable to differentiate hibernating from infarcted myocardium.

METHODS

The dual-isotope procedure was performed in 63 patients without previous myocardial infarction undergoing coronary angiography to evaluate sensitivity and specificity for coronary artery disease and in 107 patients with a low (< 5%) likelihood of coronary artery disease to evaluate normalcy rate. To validate defect reversibility, the dual-isotope SPECT study was compared with stress/rest technetium-99m sestamibi SPECT studies in a separate group of 31 patients with previous documented myocardial infarction who underwent a rest technetium-99m sestamibi study in addition to the dual-isotope SPECT study.

RESULTS

In angiographic correlations, dual-isotope SPECT demonstrated high sensitivity for detecting patients with > or = 50% stenosis (91%, 55 patients) and > or = 70% stenosis (96%, 52 patients). In a small group of patients, high specificity was also observed (75% for < 50% stenosis [8 patients] and 82% for < 70% stenosis [11 patients]). A very high normalcy rate of 95% was also found. In the patient group assessed for defect reversibility, in zones with no previous myocardial infarction, segmental agreement for defect type between rest thallium-201 and rest technetium-99m sestamibi studies was 97% (kappa = 0.79, p < 0.001). In myocardial infarct zones, segmental agreement for defect type was 98% (kappa = 0.93, p < 0.001). Image quality was generally good to excellent.

CONCLUSIONS

Our findings demonstrate that separate-acquisition dual-isotope myocardial perfusion SPECT is accurate for coronary artery disease detection, correlates well with rest-stress sestamibi studies for assessment of defect reversibility and results in good to excellent image quality. This approach provides an excellent method for the combined assessment of stress myocardial perfusion and myocardial viability.

Prevalence and functional significance of transient ST-segment depression during daily life activity: comparisons of ambulatory ECG with stress redistribution thallium 201 single-photon emission computed tomographic imaging

To assess the prevalence and functional significance of ischemic ambulatory ECG responses, we prospectively performed ambulatory ECG monitoring in 244 patients (mean age 61 +/- 10 years) referred for stress redistribution thallium 201 myocardial perfusion scintigraphy. The prevalence of ST-segment depression during ambulatory ECG was 33% among patients with a positive exercise ECG, but prevalence varied in selected patient subgroups. Among three groups with coronary artery disease (CAD), the group with ambulatory ECG ischemia (group 1) had a greater frequency of ischemic thallium responses (p = 0.07), a greater median number of reversible thallium defects (p < 0.05), and a greater summed thallium "reversibility" score (p < 0.05) than did the group with a positive exercise ECG but negative ambulatory ECG response (group 2) or that with negative exercise and ambulatory ECG responses (group 3). Exercise ST depression in group 1 versus group 2 was significantly greater (p = 0.002), occurred at a lower heart rate threshold (p = 0.002), and lasted longer after exercise (p = 0.001). Notably, one third of group 1 patients also manifested evidence of transient ischemic dilation of the left ventricle after exercise (p < 0.01 vs groups 2 and 3), a sign of severe ischemia. However, although functionally less "sick" than group 1 patients, 66% of group 2 patients and 50% of group 3 patients still had an ischemic thallium response, which was sometimes severe. Thus transient ischemia during ambulatory ECG monitoring identifies a functionally sicker cohort of patients with CAD and occurs in approximately one third of CAD patients with positive results of exercise tests. A negative ambulatory ECG response, however, does not exclude functionally significant disease among CAD patients. These results imply that caution should be applied in the interpretation of a negative ambulatory ECG response for the purpose of patient risk stratification.

Technetium 99m sestamibi in the assessment of chronic coronary artery disease

Extensive work has already been performed with regard to both planar and single photon emission computed (SPECT) technetium 99m sestamibi studies. Before widespread application of optimized acquisition and processing methods, clinical results between 99mTc sestamibi and thallium 201 were remarkably similar. It is anticipated that as techniques for 99mTc sestamibi planar and SPECT imaging become optimized, improvements in sensitivity and specificity for detection of coronary artery disease, over those observed with 201TI, might be forthcoming. This expectation is based on the improved image quality inherent in the use of the 99mTc agent with its higher count rate and higher energy. This improvement in image quality may be a principal reason for laboratories to switch from 201TI to 99mTc sestamibi imaging. It is anticipated that, with improved imaging characteristics, it will be easier for the average community hospital to obtain higher quality planar or SPECT imaging using 99mTc sestamibi rather than 201TI. In addition to improved image quality, the characteristics of 99mTc sestamibi allow gated planar or SPECT perfusion images to be obtained. It has been suggested that stress-gated SPECT sestamibi studies may provide all the information contained in a stress-rest nongated 99mTc sestamibi study, thereby potentially increasing patient throughput, a major concern with SPECT. Throughput can also be increased by using dual-isotope approaches with rest 201TI and stress technetium sestamibi acquisitions, employing either separate or simultaneous imaging with which the entire study can be accomplished in less than 2 hours. With simultaneous dual-isotope acquisition, camera time can be reduced by 50%. Finally, 99mTc sestamibi offers the advantage of the ability to perform first-pass exercise ventricular function and SPECT myocardial perfusion studies with a single injection of tracer. Regarding the assessment of myocardial viability, results to date suggest a very high degree of concordance between 201TI and 99mTc sestamibi studies using either planar or SPECT acquisition techniques. Correlative rest studies with both tracers will be of particular interest, as will preoperative and postoperative and position emission tomography correlation studies.

Myocardial perfusion imaging with technetium-99m-labeled agents

Thallium-201 (201Tl) is suboptimal as a single-photon emitting agent for myocardial perfusion imaging, in view of its low-energy photons and long half-life. To circumvent these limitations, two new myocardial perfusion imaging agents labeled with technetium-99m (99mTc) have been developed. They are Tc-sestamibi and Tc-teboroxime. Clinical trials of myocardial perfusion with both tracers have shown results similar to those obtained with 201Tl for detection of coronary artery disease. Results to date indicate that Tc-sestamibi accurately detects and locates myocardial infarction and can accurately assess both left and right ventricular ejection fractions by the first-pass technique. In addition, research has shown that rest-stress studies can be performed on the same day and that Tc-sestamibi can be used to assess the results of thrombolytic therapy. Tc-teboroxime has excellent myocardial tracer uptake characteristics but is cleared very rapidly from the myocardium. These features make Tc-teboroxime well suited to rapid serial studies. These new technetium myocardial perfusion agents have just become available for routine clinical use and are likely to replace 201Tl in many of its clinical applications.

A new approach to the assessment of tomographic thallium-201 scintigraphy in patients with left bundle branch block

To determine whether a new approach to interpretation could improve the accuracy of thallium-201 single photon emission computed tomography (SPECT) for detection of left anterior descending coronary artery disease in patients with left bundle branch block, 69 patients were evaluated. Forty-four had angiographically proved coronary artery disease; the remaining 25 were considered to have a "low" (mean 13.5 +/- 6.4%, range 3.4% to 24.9%) likelihood of disease before thallium-201 scintigraphy. The conventional scintigraphic criterion for detection of left anterior descending artery disease (septal, anterior or apical defects) was compared with a new criterion that required the apex to be abnormal to indicate left anterior descending disease. The normalcy rates in the low likelihood patient group were significantly improved by using the new approach, from 16% to 80% (p less than 0.0001) by visual analysis and from 24% to 64% (p = 0.003) by quantitative SPECT polar map analysis. The sensitivity for left anterior descending disease was similar for the conventional and the new method by visual (100% vs. 94%) and quantitative (100% vs. 83%) analyses. In contrast, the specificity was significantly improved by using the new approach, from 14% to 79% (p = 0.0006) by visual analysis and 14% to 64% (p = 0.007) by quantitative analysis. In conclusion, septal and anterior thallium-201 SPECT defects are common in patients with left bundle branch block without coronary artery disease, resulting in low specificity for left anterior descending artery disease. The normalcy rates and accuracy for detection of left anterior descending coronary artery disease were significantly better when an apical defect was used as the criterion for disease.

Dipyridamole perfusion scintigraphy: the experience with its application in one hundred seventy patients with known or suspected unstable angina

We evaluated the safety, accuracy, and potential clinical utility of intravenous dipyridamole perfusion scintigraphy with thallium-201 in 170 patients, 78 with suspected and 92 with known unstable angina. All had coronary angiography. Noncardiac side effects (26%), induced chest discomfort (44%), and ST segment changes (12%) were similar in the two groups. No significant arrhythmias occurred. Two patients had prolonged chest pain, both with extensive reversible image abnormalities and associated creatinine kinase-MB release. Both had elective bypass surgery. Twenty-eight patients had normal coronary arteries, and 35 had single-vessel disease. Scintigraphic per patient sensitivity and specificity were 91% and 79% with a per vessel sensitivity of 74% and a per vessel specificity of 78% without between-group differences. During a brief follow-up period, 62 patients with image abnormalities had coronary revascularization, and there were seven deaths without intergroup differences. In a similar patient group that did not have angiography, scintigraphic defects were less frequent and less extensive, revascularization was not performed, and subsequent deaths occurred less often. Dipyridamole perfusion scintigraphy is an accurate alternative to exercise testing in the evaluation of patients with unstable angina pectoris. Although not without risk, the method appears relatively safe and should be considered as a guide to diagnosis, and probably to prognosis and management.

Development and prospective application of quantitative 2-day stress-rest Tc-99m methoxy isobutyl isonitrile SPECT for the diagnosis of coronary artery disease

The clinical diagnostic accuracy of 2-day stress/rest quantitative Technetium-99m (Tc-99m) methoxy-isobutyl-isonitrile (Tc-sestamibi) single photon emission computerized tomography (SPECT) was assessed in a validation population of 61 patients from two different sites using two different camera/computer systems. The study population was made up of 53 catheterized patients, 29 from Cedars-Sinai Medical Center (CSMC) and 24 from the University of Texas Southwestern Medical Center (UTSMC), and eight UTSMC patients with a less than 5% pre-test likelihood of coronary artery disease. Interpretation employed gender-specific normal limits developed in an additional 15 men and 8 women at CSMC with less than a 5% likelihood of significant coronary artery disease. The results from CSMC compared with those from UTSMC were not different from each other. The overall sensitivity for detection of patients with coronary artery disease (greater than or equal to 50% stenosis) was 94% (CSMC: 92%, UTSMC: 95%). Overall specificity in the five patients with normal coronary arteriograms was 80% (CSMC: 67%, UTSMC: 100%). The normalcy rate in patients with a low likelihood of coronary artery disease was 88%. Vessel sensitivity was 85% (CSMC: 84%, UTSMC: 85%), while vessel specificity was 71% (CSMC: 72%, UTSMC: 69%). There was also no significant difference in the sensitivities and specificities between male and female populations. In addition, the agreement with coronary angiography for assessment of disease extent (normal coronary arteriogram, single or multivessel disease) was 75% (kappa = 0.6 +/- 0.1). This study demonstrated that Tc-sestamibi SPECT by quantitative analysis is accurate for the detection and localization of coronary artery disease. Furthermore, the CSMC quantitative method was shown to provide similar diagnostic accuracy when applied to data acquired at a different site using a different camera/computer system.

Comparison of physiologic ejection fraction responses to activities of daily living: implications for clinical testing

The recent development of the VEST, an ambulatory radionuclide detector, to measure left ventricular ejection fraction may enhance the detection of ischemia during daily activities in patients with coronary artery disease. The normal range and determinants of ejection fraction responses to stimuli other than physical exercise, however, are not adequately characterized. Therefore, ejection fraction responses to various activities were measured in 18 normal subjects utilizing the VEST. Uniform increases (greater than 5%) in ejection fraction were seen during physical exercise, uniform decreases were seen during cold pressor testing and modest changes (including decreases greater than 5%) were seen in ejection fraction during mental stress, micturition and hyperventilation. Different forms of stress produced significantly different changes in ejection fraction, even when values were controlled for changes in heart rate. Ventricular loading conditions in the form of enhanced blood pressure responses during mental stress may have contributed to the relatively smaller changes in ejection fraction compared with those during exercise. Subjects demonstrating a decrease in ejection fraction during mental stress did not differ from other subjects in hemodynamic reactivity during mental testing but did have evidence of increased parasympathetic tone during cold pressor and bicycle exercise testing. The results reveal that normal ejection fraction response differs among varying physiologic stimuli. These changes are in part related to changes in heart rate and blood pressure; however, other factors, such as neurohumoral regulation, may also play a role. These findings indicate that the patient's activity and the setting in which it occurs must be considered when interpreting ambulatory ejection fraction responses.

Is quantitative analysis superior to visual analysis of planar thallium 201 myocardial exercise scintigraphy in the evaluation of coronary artery disease? Analysis of a prospective clinical study

Quantitative analysis of myocardial exercise scintigraphy has been previously reported to be superior to visual image interpretation for detection of the presence and extent of coronary artery disease. Computer analysis of perfusion defects and washout rate of thallium 201 was performed on scintigrams from a group of 131 consecutive patients (prospective group), using criteria defined from a previous group of 72 patients (initial group), and compared with visual interpretation of scintigrams for detection and evaluation of coronary artery disease. The sensitivity of the quantitative technique with regard to overall detection of coronary artery disease was not significantly different from the visual method (69% and 74%, respectively), whereas the specificity was higher (86% and 68%). Quantitative analysis did not increase the sensitivity of thallium imaging over the visual method in the left anterior descending artery (46% vs 65%) and the right coronary artery (51% vs 72%) but did increase sensitivity in the left circumflex artery (75% vs 47%). Whereas in the initial group quantitative analysis resulted in a better identification of multivessel disease (sensitivity 81% vs 57%), in the prospective group sensitivity decreased (54% vs 67%) without significant loss of specificity. The initial group had a 40% incidence of three-vessel disease and the prospective group, 22% (P less than 0.05). One-vessel disease was higher in the prospective group (32% vs 11%, P less than 0.05). Thus, assessing the quantitative technique in a larger prospective patient population, there was no improvement of detection of the presence and extent of coronary artery disease when compared with visual interpretation.

Assessment of priority for coronary revascularisation procedures. Revascularisation Panel and Consensus Methods Group

To develop guidelines for ranking the urgency with which patients with angiographically proven coronary disease need revascularisation procedures, factors that a panel of cardiac specialists agreed were likely to affect urgency were incorporated into 438 fictitious case-histories. Each panelist then rated the cases on a 7-point scale based on maximum acceptable waiting time for surgery; 1 on the scale represented emergency surgery and 7 delays of up to 6 months. For only 1% of cases was there agreement on a single rating by at least 12/16 panelists. Results of this ranking exercise were used by the panel to draw up triage guidelines. The three main urgency determinants were severity and stability of symptoms of angina, coronary anatomy from angiographic studies, and results of non-invasive tests for risk of ischaemia. Together these three factors generally gave an urgency rating for any given case to within less than 0.25 scale points of the value predicted with all factors. A numerical scoring system was derived to permit rapid estimation of the panel's recommended ratings.

Prognostic significance of nonfatal myocardial reinfarction. Multicenter Diltiazem Postinfarction Trial Research Group

In most risk stratification and intervention postinfarction trials, cardiac mortality is used as the major outcome end point either alone or in combination with nonfatal reinfarction. However, the independent risk carried by nonfatal reinfarction for subsequent cardiac death has not been quantified. The prognostic significance of nonfatal reinfarction was determined from the multicenter diltiazem trial data base of 1,234 patients treated with placebo followed up for 1 to 4 years after acute myocardial infarction. One hundred sixteen patients had at least one nonfatal reinfarction, 14 (12%) of whom subsequently experienced cardiac death. Of the remaining 1,118 patients without nonfatal reinfarction, 110 (9.8%) experienced cardiac death. Compared with event-free patients, patients with nonfatal reinfarction were more likely (p less than 0.05) to be women, to have had an infarction before their index event and to have had prior cardiac-related symptoms. Cox survivorship analyses, using pertinent baseline clinical variables along with nonfatal reinfarction as a time-dependent predictor variable, revealed that nonfatal reinfarction carried a significant and independent risk for subsequent cardiac mortality (hazard ratio 3.0, p = 0.002), which was greater than that carried by other significant predictor variables (New York Heart Association functional class, pulmonary congestion on chest radiograph, blood urea nitrogen level, predischarge Holter-recorded ventricular premature complexes and radionuclide ejection fraction). The cardiac mortality risk associated with nonfatal reinfarction was further increased in patients whose index event was their first infarction (hazard ratio 5.4, p = 0.0006). Thus, nonfatal reinfarction carries a strong, significant and independent risk for subsequent cardiac death in patients surviving an acute myocardial infarction.

Transient left ventricular dysfunction during provocative mental stress in patients with coronary artery disease

We studied the temporal effects of various types of mental stress and physical exercise on the left ventricular ejection fraction (LVEF) in seven normal volunteers and nine patients with coronary artery disease. Three types of psychological stress were administered: mental arithmetic, the Stroop color word test, and a personally relevant speaking task. In the normal volunteers the LVEF response was either flat or increased (p less than 0.05) compared to the baseline value during the mental tasks and increased by a mean of 10 +/- 5% (p less than 0.05) during exercise. In contrast, in patients with coronary disease in whom LVEF did not increase greater than or equal to 5% during exercise, LVEF decreased significantly during the mental tasks (p less than 0.05 for arithmetic and Stroop tasks). Typically LVEF decreased quickly during mental stress with an immediate rebound after intervention. Decreases in LVEF during mental stress occurred without chest pain and were not associated with ECG changes. In patients with coronary disease in whom LVEF increased normally with exercise (LVEF increase greater than or equal to 5%), no significant changes in LVEF occurred during mental stress. The heart rate x systolic blood pressure double product during mental stress was significantly less than that achieved during exercise (p less than 0.05) in each normal subject and patient. Thus psychological stress can provoke acute decreases in LVEF in patients with coronary disease and exercise-inducible dysfunction. The silent nature of the mental stress-induced abnormalities and their occurrence at a lower physiologic workload compared to abnormalities during exercise parallel characteristics of transient ischemia noted during ambulatory monitoring.(ABSTRACT TRUNCATED AT 250 WORDS)

Comparison of technetium 99m methoxy isobutyl isonitrile and thallium 201 for evaluation of coronary artery disease by planar and tomographic methods

To compare stress/rest technetium 99m methoxy isobutyl isonitrile (Tc-MIBI) with stress redistribution thallium 201(T1-201) myocardial perfusion imaging, 36 patients were studied by single photon emission computerized tomography (SPECT) and planar methods. For SPECT, overall sensitivities for identification of patients with coronary artery disease were 93% (14/15) by Tc-MIBI and 80% (12/15) by TI-201 (p = NS). For planar methods, overall sensitivities were 73% (11/15) by both TI-201 and Tc-MIBI. Overall specificity was 75% (3/4 patients with normal coronary arteries) for both tracers with SPECT and Tc-MIBI by planar imaging and was 50% for planar TI-201 (p = NS). The normalcy rates for overall identification of coronary artery disease were determined in 17 patients with a low likelihood of disease. For SPECT, normalcy rates were 100% by Tc-MIBI and 77% by TI-201 (p = NS). For planar, they were 94% by Tc-MIBI and 88% by TI-201 (p = NS). Vessel sensitivities in the 35 stenosed coronary arteries (greater than or equal to 50% stenosis) for SPECT were 87% by Tc-MIBI and 77% by TI-201 (p = NS). For planar, the vessel sensitivities were 60% by Tc-MIBI and 54% by TI-201 (p = NS). For both tracers, the SPECT vessel sensitivities were significantly higher (p less than 0.005) than planar vessel sensitivities. The vessel specificities in 22 coronary vessels with less than 50% stenosis were 86% by SPECT Tc-MIBI and TI-201, 80% by planar Tc-MIBI and 73% by planar TI-201 (p = NS, SPECT vs planar, Tc-MIBI vs TI-201). Regarding myocardial segmental agreement, for the presence of stress defects the agreement was 91% for the 720 SPECT segments and 95% for the 540 planar segments. For severity of stress defects based on semiquantitative visual scoring, the exact agreement was 87% for SPECT and 80% for planar. For the pattern of reversibility in myocardial segments with stress defects, the agreement was 97% for SPECT and 91% for planar. This study demonstrated that Tc-MIBI and TI-201 correlate well on both planar and SPECT images with respect to the identification of patients with coronary artery disease, identification of disease in individual coronary arteries, the presence and severity of perfusion defects, and the assessment of defect reversibility. Furthermore, SPECT Tc-MIBI was shown to be superior to planar Tc-MIBI for the identification of individual diseased vessels.

Differences in the frequency of ST segment depression during upright and supine exercise: assessment in normals and in patients with coronary artery disease

Increased utilization of ambulatory ST segment monitoring mandates an appreciation of nonischemic variables that may influence the ST segment. While a greater frequency of ST segment depression has been reported with supine vs upright exercise, the relative false positive rate in both positions is not known. Thus, we compared the frequency of exercise ECG abnormalities during upright and supine bicycle exercise in two groups--17 normals and 46 patients with coronary artery disease. Exercise was performed in combination with radionuclide ventriculographic imaging. Peak exercise heart rate, peak systolic blood pressure, and exercise duration time were all slightly higher in the upright vs supine position (p less than 0.05). Nevertheless, the frequency of positive ST segment responses was more common in the supine position, both in the patients with coronary artery disease (54% vs 30%, p less than 0.05) and in the normal subjects (29% vs 6%, p = NS). The corresponding radionuclide ventriculographic responses, however, were normal during upright and supine exercise in 6 of the 11 CAD patients and in all five of the normal subjects with an abnormal ST segment response during supine exercise only. The frequency of exercise-induced chest pain was also similar in the two positions. Thus, we theorize that nonischemic factors may govern some positive ST segment responses in the supine position. This finding is of relevance for understanding the potential sources of physiologic false positive ST segment responses for ambulatory ST segment monitoring.