Prognostic value of dipyridamole technetium-99m sestamibi myocardial tomography in patients with stable chest pain who are unable to exercise

High prevalence of coronary artery calcification in Saudi patients with normal myocardial perfusion

BACKGROUND

Normal single-photon emission computed tomography (SPECT) myocardial perfusion imaging (MPI) has a high negative predictive value for ischemic heart disease. Thus, the presence of subclinical coronary atherosclerosis detected by coronary artery calcification (CAC) score in patients who have under-gone SPECT MPI is unknown.

OBJECTIVES

Determine the prevalence of coronary artery calcification (CAC) in patients with normal SPECT MPI and examine the association of CAC with conventional coronary artery disease (CAD) risk factors.

DESIGN

Cross-sectional analytical study using medical records from February 2010 to April 2016.

SETTINGS

Single tertiary-care center.

PATIENTS AND METHODS

We studied patients referred from the outpatient clinical services for clinically indicated noninvasive CAD diagnosis with MPI SPECT. CAC scoring was subsequently performed within 3 months after a normal MPI. We excluded patients with chest pain or decompensated heart failure or patients with a history of CAD. The study population was divided into three groups: patients with a CAC score of 0, a CAC score from 1 to 300, and a CAC score more than 300. The groups were analyzed by age and other demographic and clinical characteristics.

MAIN OUTCOME MEASURE(S)

Prevalence of CAC in patients with normal MPI.

RESULTS

The prevalence of CAC was 55% (n=114) in 207 patients with a mean (SD) age of 57.1 (10.4) years. Twelve percent had severe coronary atherosclerosis (CAC score > 300). All patients had a normal MPI SPECT. CAC scores were 0 for 93 patients (45%), 1 to 300 for 89 (43%), and more than 300 for 24 (12%). There was a strong association between CAC score and age (P < .0001), male sex (P < .0001), and diabetes mellitus (P=.042), but no association between CAC score and hypertension (P=.153), family history of CAD (P=.23), obesity (P=.31), hypercholesterolemia (P=.071), or smoking (P=.308).

CONCLUSIONS

The prevalence of CAC is high in this study population of patients with normal SPECT MPI. Age, male sex and diabetes were risk factors associated with CAC.

LIMITATIONS

Single center and small study population.

Assessment of coronary flow reserve using a combination of planar first-pass angiography and myocardial SPECT: Comparison with myocardial (15)O-water PET

Coronary flow reserve (CFR), defined as the ratio of maximum coronary flow increase from baseline resting blood flow, is one of the most sensitive parameters to detect early signs of coronary arteriosclerosis at the microvascular level. Myocardial perfusion PET is a well-established technology for CFR measurement, however, availability is still limited. The aim of this study is to introduce and validate myocardial flow reserve measurement by myocardial perfusion SPECT.

METHODS

Myocardial perfusion SPECT at rest and ATP stress (0.16mg/Kg/min) was performed in 10 patients with known coronary artery disease. Immediately after the injection of Tc-99m sestamibi (MIBI), left ventricular (LV) dynamic planar angiographic data were obtained for 90s. Coronary flow reserve index as measured by MIBI SPECT (CFRMIBI) was calculated as follows: CFRMIBI=CmsSbmb/CmbSbms, where subscripts b, s, Cm, and Sbm indicate baseline, during stress, myocardial counts with MIBI SPECT, and integral of LV counts with first pass angiography, respectively. Additionally, standard stress/rest (15)O-water PET to estimate CFR was performed in all patients as standard of reference.

RESULTS

CFRMIBI increased in conjunction with CFR, but underestimated blood flow at high flow rates. The relationship between CFRMIBI (Y) and CFRPET (X) was well fitted as follows: Y=1.40x(1-exp(1.79/x)) (r=0.84).

CONCLUSIONS

The index of CFRMIBI reflects the CFR by (15)O-water PET but underestimates flow at high flows, maybe as a reflection of pharmacokinetic limitations of MIBI.

Cardiovascular mortality prediction in veterans with arm exercise vs pharmacologic myocardial perfusion imaging

BACKGROUND

No data exist comparing outcome prediction from arm exercise vs pharmacologic myocardial perfusion imaging (MPI) stress test variables in patients unable to perform treadmill exercise.

METHODS

In this retrospective study, 2,173 consecutive lower extremity disabled veterans aged 65.4 ± 11.0years (mean ± SD) underwent either pharmacologic MPI (1730 patients) or arm exercise stress tests (443 patients) with MPI (n = 253) or electrocardiography alone (n = 190) between 1997 and 2002. Cox multivariate regression models and reclassification analysis by integrated discrimination improvement (IDI) were used to characterize stress test and MPI predictors of cardiovascular mortality at ≥10-year follow-up after inclusion of significant demographic, clinical, and other variables.

RESULTS

Cardiovascular death occurred in 561 pharmacologic MPI and 102 arm exercise participants. Multivariate-adjusted cardiovascular mortality was predicted by arm exercise resting metabolic equivalents (hazard ratio [HR] 0.52, 95% CI 0.39-0.69, P < .001), 1-minute heart rate recovery (HR 0.61, 95% CI 0.44-0.86, P < .001), and pharmacologic and arm exercise delta (peak-rest) heart rate (both P < .001). Only an abnormal arm exercise MPI prognosticated cardiovascular death by multivariate Cox analysis (HR 1.98, 95% CI 1.04-3.77, P < .05). Arm exercise MPI defect number, type, and size provided IDI over covariates for prediction of cardiovascular mortality (IDI = 0.074-0.097). Only pharmacologic defect size prognosticated cardiovascular mortality (IDI = 0.022).

CONCLUSIONS

Arm exercise capacity, heart rate recovery, and pharmacologic and arm exercise heart rate responses are robust predictors of cardiovascular mortality. Arm exercise MPI results are equivalent and possibly superior to pharmacologic MPI for cardiovascular mortality prediction in patients unable to perform treadmill exercise.

Comparison of long-term mortality risk following normal exercise vs adenosine myocardial perfusion SPECT

BACKGROUND

A higher frequency of clinical events has been observed in patients undergoing pharmacological vs exercise myocardial perfusion single-photon emission computed tomography (SPECT). While this difference is attributed to greater age and co-morbidities, it is not known whether these tests also differ in prognostic ability among patients with similar clinical profiles.

METHODS AND RESULTS

We assessed all-cause mortality rates in 6,069 patients, followed for 10.2 ± 1.7 years after undergoing exercise or adenosine SPECT. We employed propensity analysis to match exercise and adenosine subgroups by age, gender, symptoms, and coronary risk factors. Within our propensity-matched cohorts, adenosine patients had an annualized mortality rate event rates that was more than twice that of exercise patients (3.9% vs 1.6%, P < .0001). Differences in mortality persisted among age groups, including those <55 years old. In the exercise cohort, mortality was inversely related to exercise duration, with comparable mortality noted for patients exercising <3 min and those undergoing adenosine testing.

CONCLUSIONS

Among patients with normal stress SPECT tests, those undergoing adenosine testing manifest a mortality rate that is substantially higher than that observed among adequately exercising patients, but comparable to that observed among very poorly exercising patients. This elevated risk underscores an important challenge for managing patients undergoing pharmacological stress testing.

NT-proBNP and circulating inflammation markers in prediction of a normal myocardial scintigraphy in patients with symptoms of coronary artery disease

BACKGROUND

Myocardial perfusion imaging (MPI) can detect myocardial perfusion abnormalities but many examinations are without pathological findings. This study examines whether circulating biomarkers can be used as screening modality prior to MPI.

METHODOLOGY/PRINCIPAL FINDINGS

243 patients with an intermediate risk of CAD or with known CAD with renewed suspicion of ischemia were referred to MPI. Blood samples were analyzed for N-terminal fragment of the prohormone brain natriuretic peptide (NT-proBNP), YKL-40, IL-6, matrix metalloproteinase 9 (MMP-9) and high sensitive C-reactive protein (hsCRP). Patients with myocardial perfusion defects had elevated levels of NT-proBNP (p<0.0001), YKL-40 (p = 0.03) and IL-6 (p = 0.03) but not of hsCRP (p = 0.58) nor of MMP-9 (p = 0.14). The NT-proBNP increase was observed in both genders (p<0.0001), whereas YKL-40 (p = 0.005) and IL-6 (p = 0.02) were elevated only in men. A NT-proBNP cut off-concentration at 25 ng/l predicted a normal MPI with a negative predictive value >95% regardless of existing CAD.

CONCLUSIONS

20-25% of patients suspected of CAD could have been spared a MPI by using a NT-proBNP cut-off concentration at 25 ng/l with a negative predictive value >95%. NT-proBNP has the potential use of being a screening marker of CAD before referral of the patient to MPI.

Long-term prognostic value of 13N-ammonia myocardial perfusion positron emission tomography added value of coronary flow reserve

OBJECTIVES

The goal of this study was to assess the predictive value of myocardial perfusion imaging with (13)N-ammonia positron emission tomography (PET) and coronary flow reserve (CFR) on long-term prognosis in patients with suspected myocardial ischemia.

BACKGROUND

No prognostic data exist on the predictive value of CFR and (13)N-ammonia PET.

METHODS

Perfusion and CFR were assessed in 256 patients using (13)N-ammonia PET, and follow-up was obtained in 245 (96%) patients. Sixteen early revascularized patients were excluded and 229 were assigned to normal versus abnormal perfusion or normal versus abnormal CFR (<2.0). Major adverse cardiac events (MACE) (cardiac death, nonfatal myocardial infarction, late revascularization, or hospitalization for cardiac reasons) were assessed using the Kaplan-Meier method. Cox proportional hazard regression was used to identify independent predictors for cardiac events.

RESULTS

During follow-up (5.4 +/- 2.2 years), 78 patients had at least 1 cardiac event, including 29 cardiac deaths. Abnormal perfusion (n = 126) was associated with a higher incidence of MACE (p < 0.001) and cardiac death (p < 0.05). In patients with normal perfusion, abnormal CFR was independently associated with a higher annual event rate over 3 years compared with normal CFR for MACE (1.4% vs. 6.3%; p < 0.05) and cardiac death (0.5% vs. 3.1%; p < 0.05). In abnormal perfusion, CFR remained predictive throughout the 10-year follow-up (p < 0.001).

CONCLUSIONS

Perfusion findings in (13)N-ammonia PET and CFR are strong outcome predictors. CFR allows further risk stratification, suggesting a "warranty" period of 3 years if normal CFR is associated with normal perfusion. Conversely, in patients with abnormal perfusion, an impaired CFR has added value for predicting adverse outcomes.

Reduced heart rate response to dipyridamole as a marker of left ventricular dysfunction in diabetic patients undergoing myocardial perfusion scintigraphy

PURPOSE OF THE REPORT

This study sought to find among clinical, hemodynamic and left ventricular perfusion and function data obtained from myocardial perfusion scintigraphy (MPS), those associated with a reduced heart rate (HR) response to dipyridamole in diabetic patients. This phenomenon, although previously described as a marker of autonomic dysfunction in patients with diabetes, has not been fully elucidated.

MATERIALS AND METHODS

One hundred two consecutive diabetic patients undergoing dual-isotope (rest Tl-201/dipyridamole stress Tc-99m tetrofosmin) MPS were prospectively enrolled. A reduced HR response to dipyridamole was considered present if the ratio between maximal HR after dipyridamole infusion and rest HR was <or=1.20. MPS images were interpreted semiquantitatively, and perfusion scores were calculated. Left ventricular ejection fraction (LVEF) was automatically obtained. A logistic regression analysis was used to find variables independently associated with a reduced HR response to dipyridamole.

RESULTS

A reduced HR response to dipyridamole was found in 46.1% of the patients and was associated with the presence of chronic renal failure (chi2 = 6.4), with high baseline HR (chi2 = 4.7) and low poststress LVEF (chi2 = 10.6).

CONCLUSIONS

Attenuation of the HR response to dipyridamole was frequent and was strongly associated with reduced LVEF. Autonomic dysfunction may be reflected in the higher baseline HR but should not be considered the sole mechanism accounting for the reduction in HR response to dipyridamole in patients with diabetes.

Influence of chronic renal failure on the heart rate response to dipyridamole in patients undergoing myocardial perfusion SPECT

BACKGROUND

Dipyridamole promotes a reduction in blood pressure and an increase in heart rate (HR), considered the normal hemodynamic response to the drug. Data suggest that patients with chronic renal failure (CRF) have an attenuation of this hemodynamic response. This study sought to evaluate the HR response to dipyridamole and its determinants in patients with or without CRF undergoing gated myocardial perfusion single photon emission computed tomography.

METHODS AND RESULTS

Consecutive patients (n = 355, 9.6% with CRF) undergoing rest/dipyridamole myocardial perfusion single photon emission computed tomography were evaluated. The HR response to dipyridamole was considered to be reduced if the HR ratio (maximal HR/rest HR) was 1.20 or less. A logistic regression analysis determined independent predictors of a blunted HR response. A reduced HR response was found in 84.4% of patients with CRF and 40.6% of those without CRF (P < .0001). In patients without CRF the independent predictors of abnormal HR response were hypertension, rest and differential perfusion scores, and left ventricular ejection fraction. In contrast, in CRF patients there was no significant association of any of the studied variables with abnormal HR response.

CONCLUSIONS

An abnormal HR response to dipyridamole is frequently found in patients with CRF. Different mechanisms may account for abnormal HR response in patients with or without CRF.

Symptom-limited exercise combined with dipyridamole stress: prognostic value in assessment of known or suspected coronary artery disease by use of gated SPECT imaging

BACKGROUND

Combining vasodilator and exercise stress reduces noncardiac side effects, improves image quality, and enhances the detection of ischemia, compared with suboptimal exercise or vasodilator stress alone. However, prognostic data with combined protocols are limited.

METHODS AND RESULTS

Consecutive patients (n = 2064) who underwent symptom-limited exercise and dipyridamole stress with gated single-photon emission computed tomography (SPECT) imaging, without early revascularization, were studied. Subsequent cardiac death or nonfatal myocardial infarction was related to exercise and gated SPECT variables. Cox proportional hazards regression modeling was performed to identify predictors of adverse outcome. Annualized event rates in patients with normal and abnormal images were 0.96% and 2.71%, respectively (P < .001). With abnormal imaging, annualized event rates were 0.86% and 3.13% in patients with average to high and fair or poor functional capacity, respectively (P = .019). Abnormal imaging, a severely reduced post-stress ejection fraction, transient ischemic dilation, and fair or poor functional capacity emerged as predictors of adverse outcome. Accordingly, patients were stratified into low-risk, intermediate-risk, and high-risk cohorts with annualized event rates of 0.94%, 2.24%, and 8.19%, respectively (P < .001 in any two-way comparison).

CONCLUSIONS

A protocol that combines symptom-limited exercise and dipyridamole stress with gated SPECT imaging provides highly effective risk stratification for adverse outcomes.

Myocardial perfusion imaging in the elderly: a review

Coronary artery disease is a major cause of morbidity and mortality in the elderly population. As a result of ageing of the population and better medical, interventional and surgical treatment of patients with coronary artery disease, more and more elderly patients are referred to the cardiology department for diagnostic work-up. Stress testing, in combination with myocardial perfusion imaging, is routinely used in elderly patients, a population in which the diagnosis of significant coronary artery disease is often challenging because of atypical symptomatology. Since the introduction of technetium-99m ligands for myocardial perfusion imaging, it is possible to perform electrocardiogram-gated perfusion imaging. This not only improves the specificity of the test for coronary artery disease detection, but also enables the simultaneous assessment of left ventricular functional parameters. This article briefly overviews the possible stress modalities, diagnostic accuracy and prognostic value of myocardial perfusion imaging in elderly patients.

Comparison of myocardial blood flow induced by adenosine triphosphate and dipyridamole in patients with coronary artery disease

Myocardial perfusion imaging with adenosine triphosphate (ATP) has been used increasingly to diagnose coronary artery disease (CAD) and assess risk for this disease. This study compared absolute myocardial blood flow (MBF) and myocardial flow reserve index (MFR) with ATP and dipyridamole (DIP) in patients with CAD. MBF was quantified by 15O-H2O PET in 21 patients with CAD (17 male, 4 female), aged 55 to 81 years. MBF was measured at rest, during intravenous injection of ATP (0.16 mg/kg/min), and again after DIP infusion (0.56 mg/kg). Regions of interest were drawn in nonischemic and ischemic segments based on findings from thallium-201 (201T1) scintigraphy and coronary angiography (CAG). Absolute MBF values and indexes of MFR were calculated in nonischemic and ischemic segments. Intravenous injection of ATP and DIP significantly increased MBF in nonischemic (2.4 +/- 0.9 and 2.1 +/- 0.8 ml/g/min, respectively; p < 0.01, for both) and in ischemic segments (1.3 +/- 0.4 and 1.5 +/- 0.4 ml/g/min, respectively; p < 0.01, for both). There was a significant difference in MBF values between ATP and DIP in nonischemic segments (p < 0.05), which was not observed in ischemic segments. In nonischemic segments, ATP produced higher MFR than DIP (2.1 +/- 0.8 and 1.8 +/- 0.7, respectively; p < 0.05), while no significant difference was observed in ischemic segments (1.5 +/- 0.6 and 1.7 +/- 0.3, respectively). ATP produced a greater hyperemia than DIP between the ischemic and nonischemic myocardium in patients with CAD. ATP is as effective as DIP for the diagnosis of CAD.

Incremental prognostic value of combined perfusion and function assessment during myocardial gated SPECT in patients aged 75 years or older

BACKGROUND

Perfusion and functional data obtained during gated single photon emission computed tomography (SPECT) have proven prognostic value in the middle-aged patient population. The aim of this study was to investigate whether perfusion and functional cardiac gated SPECT data have prognostic value in patients aged 75 years or older.

METHODS AND RESULTS

We studied clinical and gated SPECT predictors of cardiac and all-cause death in 294 patients aged 75 years or older with known or suspected coronary artery disease who were referred for tetrofosmin cardiac gated SPECT imaging. Summed perfusion scores were calculated in a 17-segment model by use of commercially available software (4D-MSPECT). Left ventricular functional data were calculated by use of QGS gated SPECT software. The median age of the study population was 78 years (range, 75-91 years). There were 160 men (54%) and 134 women (46%). During a median follow-up of 25.9 months (range, 1.8-36 months), 47 patients (16%) died (27 cardiac deaths). In a multivariate Cox proportional hazards regression analysis, the summed rest score (chi2 gain = 8.0, P = .009), transient ischemic dilatation index (chi2 gain = 6.3, P = .012), and resting left ventricular ejection fraction (chi2 gain = 7.0, P = .030) were independent predictors of all-cause death. The summed rest score (chi2 gain = 8.2, P = .004) and resting end-systolic volume (chi2 gain = 13.7, P = .005) were independent predictors of cardiac death.

CONCLUSIONS

This study showed that gated SPECT left ventricular functional data assessed during myocardial gated SPECT provide independent and incremental information above clinical and perfusion SPECT data for the prediction of cardiac and all-cause death in patients aged 75 years or older referred for myocardial SPECT imaging.

The use of nuclear cardiology in clinical decision making

Extensive data exist to support the role of myocardial perfusion single-photon emission computed tomography (MPS) in risk stratification. Normal MPS studies usually are associated with very low risk, and patient risk increase significantly as a function of MPS results. Ventricular function measurements from gated single-photon emission computed tomography further augment risk stratification, particularly with respect to identifying patients at risk of cardiac death. Ancillary findings are prognostically important, particularly in the setting of normal or near-normal MPS results. Recent data suggest that MPS results can identify which patients will benefit from revascularization versus medical therapy and have expanded the understanding of how stress MPS is helpful in the identification of risk, enhanced the means of identifying risk, and improved its use as a means to identify optimal posttest treatment.

Role of noninvasive testing in the clinical evaluation of women with suspected coronary artery disease: Consensus statement from the Cardiac Imaging Committee, Council on Clinical Cardiology, and the Cardiovascular Imaging and Intervention Committee, Council on Cardiovascular Radiology and Intervention, American Heart Association

Cardiovascular disease is the leading cause of mortality for women in the United States. Coronary heart disease, which includes coronary atherosclerotic disease, myocardial infarction, acute coronary syndromes, and angina, is the largest subset of this mortality, with >240,000 women dying annually from the disease. Atherosclerotic coronary artery disease (CAD) is the focus of this consensus statement. Research continues to report underrecognition and underdiagnosis of CAD as contributory to high mortality rates in women. Timely and accurate diagnosis can significantly reduce CAD mortality for women; indeed, once the diagnosis is made, it does appear that current treatments are equally effective at reducing risk in both women and men. As such, noninvasive diagnostic and prognostic testing offers the potential to identify women at increased CAD risk as the basis for instituting preventive and therapeutic interventions. Nevertheless, the recent evidence-based practice program report from the Agency for Healthcare Research and Quality noted the paucity of women enrolled in diagnostic research studies. Consequently, much of the evidence supporting contemporary recommendations for noninvasive diagnostic studies in women is extrapolated from studies conducted predominantly in cohorts of middle-aged men. The majority of diagnostic and prognostic evidence in cardiac imaging in women and men has been derived from observational registries and referral populations that are affected by selection and other biases. Thus, a better understanding of the potential impact of sex differences on noninvasive cardiac testing in women may greatly improve clinical decision making. This consensus statement provides a synopsis of available evidence on the role of the exercise ECG and cardiac imaging modalities, both those in common use as well as developing technologies that may add clinical value to the diagnosis and risk assessment of the symptomatic and asymptomatic woman with suspected CAD.

Comparison of risk stratification with pharmacologic and exercise stress myocardial perfusion imaging: a meta-analysis

BACKGROUND

Although pharmacologic stress myocardial perfusion imaging (MPI) and exercise stress MPI have comparable diagnostic accuracy, their comparative value for risk stratification of patients with known or suspected coronary disease is not known.

METHODS AND RESULTS

The data of 14,918 patients were combined from 24 studies evaluating prognosis in patients undergoing either pharmacologic stress or exercise stress MPI. Studies were included if a 2 x 2 table for hard cardiac events (cardiac death and myocardial infarction [MI]) could be constructed from the data available. Excluded were studies performed for post-MI, post-revascularization, or preoperative risk stratification. A weighted t test was used to compare the cardiac events, and a random effects model was used to calculate summary odds ratios. Summary odds ratios for hard cardiac events were similar for pharmacologic stress and exercise stress MPI. Summary receiver operating characteristic curves also showed no difference in discriminatory power between the stressors. The cardiac event rates were significantly higher with normal and abnormal test results with pharmacologic stress MPI than with exercise stress MPI (1.78% vs 0.65% [P < .001] for normal results and 9.98% vs 4.3% [P < .001] for abnormal results). Subgroup analysis revealed that both cardiac death and nonfatal MI were significantly higher with pharmacologic stress MPI. Patients undergoing pharmacologic stress MPI had a significantly higher prevalence of poor prognostic factors, and meta-regression revealed that exercise capacity was the single most important predictor of cardiac events.

CONCLUSIONS

This meta-analysis shows that exercise stress MPI and pharmacologic stress MPI are comparable in their ability to risk-stratify patients. However, patients undergoing pharmacologic stress studies are at a higher risk for subsequent cardiac events. This is true even for those with normal perfusion imaging results.

Medium- to long-term prognostic impact of dipyridamole thallum-201 myocardial single-photon emission computed tomography in elderly patients

Dipyridamole thallium-201 single-photon emission computed tomography (SPECT) has not been extensively evaluated for risk stratification and the medium- to long-term prognostic value in elderly cardiac patients who are unable to exercise. The present study group comprised 210 consecutive patients aged at least 70 years with known or suspected coronary artery disease (CAD). The SPECT findings were classified as a reversible, fixed, or combined (reversible and fixed) defect. Of the 210 patients, 201 (77+/-5 years, 85 male) were successfully followed for 49+/-26 months. Thirteen (7%) patients had cardiac events: cardiac death (n=10), non-fatal myocardial infarction (n=1), or coronary artery bypass grafting (n=2). Cardiac events occurred in 3 of 112 patients with normal SPECT and in 10 of 89 patients with an abnormal scan (0.7% /year vs 2.8% /year, p=0.01). Stepwise Cox regression analysis revealed that the significant predictors of cardiac events were combined defects (relative risk 7.3) and the number of defect areas (relative risk 4.4). The predictive value of dipyridamole thallium-201 SPECT is maintained over 4 years in mixed populations of elderly CAD patients who are unable to exercise.

Myocardial perfusion scintigraphy: the evidence

This review summarises the evidence for the role of myocardial perfusion scintigraphy (MPS) in patients with known or suspected coronary artery disease. It is the product of a consensus conference organised by the British Cardiac Society, the British Nuclear Cardiology Society and the British Nuclear Medicine Society and is endorsed by the Royal College of Physicians of London and the Royal College of Radiologists. It was used to inform the UK National Institute of Clinical Excellence in their appraisal of MPS in patients with chest pain and myocardial infarction. MPS is a well-established, non-invasive imaging technique with a large body of evidence to support its effectiveness in the diagnosis and management of angina and myocardial infarction. It is more accurate than the exercise ECG in detecting myocardial ischaemia and it is the single most powerful technique for predicting future coronary events. The high diagnostic accuracy of MPS allows reliable risk stratification and guides the selection of patients for further interventions, such as revascularisation. This in turn allows more appropriate utilisation of resources, with the potential for both improved clinical outcomes and greater cost-effectiveness. Evidence from modelling and observational studies supports the enhanced cost-effectiveness associated with MPS use. In patients presenting with stable or acute chest pain, strategies of investigation involving MPS are more cost-effective than those not using the technique. MPS also has particular advantages over alternative techniques in the management of a number of patient subgroups, including women, the elderly and those with diabetes, and its use will have a favourable impact on cost-effectiveness in these groups. MPS is already an integral part of many clinical guidelines for the investigation and management of angina and myocardial infarction. However, the technique is underutilised in the UK, as judged by the inappropriately long waiting times and by comparison with the numbers of revascularisations and coronary angiograms performed. Furthermore, MPS activity levels in this country fall far short of those in comparable European countries, with about half as many scans being undertaken per year. Currently, the number of MPS studies performed annually in the UK is 1,200/million population/year. We estimate the real need to be 4,000/million/year. The current average waiting time is 20 weeks and we recommend that clinically appropriate upper limits of waiting time are 6 weeks for routine studies and 1 week for urgent studies.

The clinical role of stress myocardial perfusion imaging in women with suspected coronary artery disease

Cardiovascular disease remains the number one cause of mortality for women in the United States, with coronary artery disease (CAD) accounting for 54% of all cardiovascular deaths. CAD claims the lives of more than 250,000 women each year and is therefore the single largest killer of American women. For several decades, the under-representation of women in clinical trials led to both a lack of available sex-specific evidence and a generalized misconception that CAD was a "man's disease." In actuality, not only are women vulnerable to CAD, they typically develop it 10 to 15 years later than men. Furthermore, sex differences exist in the mortality rates of women and men with CAD, such that once CAD is present in women, they have worse outcomes than their male counterparts. Consequently, early and accurate diagnosis of CAD is crucial for reducing mortality rates in women. Stress myocardial perfusion imaging (MPI) using contemporary techniques has been shown to have significant value in the diagnosis and prognosis of CAD in women. In the risk assessment of women with an intermediate clinical pretest likelihood of CAD, using MPI with exercise or pharmacologic stress has been shown to add incremental value to clinical variables or exercise electrocardiogram stress testing alone. This review discusses the clinical role of stress MPI in the management of women with suspected CAD.

Role of myocardial perfusion imaging for risk stratification in suspected or known coronary artery disease

Nuclear cardiology is an evolving specialty that has recently benefited from technological and radiopharmaceutical advances. As a result there has been an increase in the accuracy of myocardial perfusion imaging (MPI) with gated single photon emission computed tomography (SPECT) for assessing the diagnosis and prognosis of coronary artery disease. Moreover, ECG gated SPECT allows the simultaneous assessment of both myocardial perfusion and left ventricular function, which provides additional prognostic value. With increasing concern over early detection of coronary artery disease and its effective treatment, myocardial perfusion imaging is ideally placed to provide a full "one stop" functional assessment for any patient, irrespective of their exercise capacity. This applies not only to patients with chest pain but also to those with myocardial infarction, revascularisation, and heart failure, and those being assessed for non-cardiac surgery. The focus of this review is the use of myocardial perfusion imaging in risk stratification for coronary artery disease.

Coronary artery angiography in systemic lupus erythematosus patients with abnormal myocardial perfusion scintigraphy

OBJECTIVE

According to published studies, 16-82% of systemic lupus erythematosus (SLE) patients have abnormal findings on myocardial perfusion tests, but it has not been established whether these patients also have abnormal findings on coronary angiography. The aim of this study was to evaluate the frequency of abnormal findings on coronary angiography in SLE patients in whom myocardial perfusion scintigraphy revealed abnormalities.

METHODS

Ninety female SLE patients (ages 20-55 years, disease duration >5 years, and current or previous steroid treatment for >/=1 year) underwent myocardial perfusion scintigraphy with single-photon-emission computed tomography using (99m)Tc-sestamibi. Images were taken while the patient was at rest and after dipyridamole-induced stress. Myocardial perfusion defects were identified in 30 patients (33%). Twenty-one of these patients (mean +/- SD age 42 +/- 9; mean +/- SD disease duration 132 +/- 66 months) agreed to undergo coronary angiography.

RESULTS

Atherosclerotic plaques were identified by angiography in 8 of the 21 patients (38%). The majority of coronary abnormalities were localized in the anterior descending artery. The mean +/- SD number of risk factors for coronary artery disease (CAD) was significantly higher in the subgroup with (4.5 +/- 0.8) compared with the subgroup without (2.5 +/- 1.9) abnormal angiographic findings (P = 0.006). Arterial hypertension and postmenopause status were significantly associated with abnormal angiographic findings. Of the patients with at least 4 risk factors for CAD, coronary stenosis was present in 67% (P = 0.005). The number of American College of Rheumatology (ACR) criteria for SLE and scores on the SLE Disease Activity Index and the Systemic Lupus International Collaborating Clinics/ACR damage index were also higher in the subgroup with coronary stenosis (P < 0.05).

CONCLUSION

This is the first study to examine coronary angiography results in SLE patients with abnormal findings on myocardial scintigraphy. Our data suggest that myocardial scintigraphy can be used to screen SLE patients and that all patients with abnormal findings plus at least 4 risk factors for CAD should undergo coronary angiography.

Stress Myocardial Perfusion Imaging in the Diagnosis and Prognosis of Women with Suspected Coronary Artery Disease

Coronary artery disease is the single largest killer of women in the United States and claims the lives of more than 250,000 women each year. For several decades, there was the misperception that coronary artery disease was a "man's disease." The fact is that women are indeed vulnerable to coronary artery disease; however, they typically develop the disease 10 to 15 years later than men. Once coronary artery disease is evident, women have worse outcomes as compared with men.Therefore, early and accurate diagnosis of coronary artery disease is crucial for reducing heart disease mortality in women. Stress myocardial perfusion imaging using contemporary techniques has been shown to have significant value in the diagnosis and prognosis of coronary artery disease in women. Myocardial perfusion imaging with exercise or pharmacologic stress has been shown to add incremental value to the use of clinical variables or exercise electrocardiogram stress testing alone in the risk stratification of women with an intermediate clinical pretest likelihood of coronary artery disease. This review provides an overview of the role of stress myocardial perfusion imaging in the clinical evaluation of women with suspected coronary artery disease.

Long-term prognosis after a normal exercise stress Tc-99m sestamibi SPECT study

BACKGROUND

Patients with a normal stress technetium 99m sestamibi study were shown to have a favorable outcome at intermediate-term follow-up. However, long-term survival has not been studied. The aim of this study was to evaluate the incidence and predictors of mortality and cardiac events at long-term follow-up after a normal exercise stress sestamibi study. Methods and results We studied 218 patients (mean age, 53 +/- 10 years, 108 men) who had normal myocardial perfusion assessed by Tc-99m sestamibi single photon emission computed tomography at rest and during symptom-limited bicycle exercise stress test. Endpoints during a follow-up period of 7.4 +/- 1.8 years were hard cardiac events (cardiac death and nonfatal myocardial infarction) and all-cause mortality. During follow-up, 13 patients died of various causes (cardiac death in 1 patient). Ten patients had nonfatal myocardial infarction (a total of 11 hard cardiac events). By multivariate analysis, independent predictors of cardiac events were history of coronary artery disease (chi(2) = 5, P =.03) and lower exercise heart rate (chi(2) = 12, P =.001). Independent predictors of all-cause mortality were age (chi(2) = 4, P =.05) and exercise heart rate (chi(2) = 5, P =.03). The annual mortality rate was 0.6% in the first 5 years and 1.8% between the sixth and eighth years. The annual hard cardiac event rate was 0.7% in the first 5 years and 1.5% between the sixth and eighth years. Receiver operating characteristic curves identified an exercise heart rate lower than 130 beats/min as the cutoff value that separated patients with regard to their risk for mortality and hard cardiac events.

CONCLUSIONS

It is concluded that the annual mortality and cardiac event rate is less than 1% during 5-year follow-up after a normal exercise sestamibi study. Therefore repeated testing would not be required unless there is a change in symptoms. Follow-up should be closer in patients with a history of coronary artery disease and in those who fail to achieve an exercise heart rate of 130 beats/min or greater.

Determinants of risk and its temporal variation in patients with normal stress myocardial perfusion scans: what is the warranty period of a normal scan?

OBJECTIVES

The aim of this study was to determine the predictors of risk and the temporal characteristics of risk associated with normal myocardial perfusion single photon emission computed tomography (MPS).

BACKGROUND

No empiric data exist regarding predictors of risk after normal MPS and their temporal characteristics.

METHODS

Follow-up (mean: 665 +/- 200 days, 96% complete) of 7,376 consecutive patients with normal exercise or adenosine MPS identified 78 hard events (HE) (45 cardiac deaths, 33 non-fatal myocardial infarction; 1.1% cumulative HE rate, 0.6%/year). Cox proportional hazards analysis was used to identify predictors of HE. Parametric survival analysis was used to model predicted time to HE.

RESULTS

The HE rates were greater in patients with versus without previous coronary artery disease (CAD). The Cox proportional hazards model identified pharmacologic stress, known CAD, diabetes mellitus (DM), male gender, and increasing age, with interactions between stress type and previous CAD (lower risk in patients without previous CAD undergoing exercise stress vs. all others) and between DM and gender (higher risk in DM females vs. all others) as the model most predictive of HE. The highest risk subgroups had a maximal event rate of 1.4% to 1.8%/year. Parametric survival models revealed that in patients without previous CAD the level of risk was uniform with time, but in patients with known CAD, risk increased with time (e.g., risk in the first year was less than in the second year, hence, a dynamic temporal component of risk was present).

CONCLUSIONS

Multiple clinical factors add incremental prognostic value in patients with normal MPS, affecting their risk and its temporal pattern, and may alter the appropriate timing of repeat testing, hence establishing the existence of a "warranty" period for normal MPS studies.

Prognostic value of dobutamine stress technetium-99m-sestamibi single-photon emission computed tomography myocardial perfusion imaging: stratification of a high-risk population

OBJECTIVES

This work was undertaken to define the intrinsic cardiac risk of the patient population referred for dobutamine stress perfusion imaging and to determine whether dobutamine technetium-99m ((99m)Tc)-sestamibi single-photon emission computed tomography (SPECT) imaging is capable of risk stratification in this population.

BACKGROUND

In animal models, dobutamine attenuates the myocardial uptake of (99m)Tc-sestamibi resulting in underestimation of coronary stenoses. Therefore, we hypothesized that the prognostic value of dobutamine stress (99m)Tc-sestamibi SPECT myocardial perfusion imaging might be impaired, owing to reduced detection of coronary stenoses.

METHODS

We reviewed the clinical outcome of 308 patients (166 women, 142 men) who underwent dobutamine stress SPECT (99m)Tc-sestamibi imaging at our institution from September 1992 through December 1996.

RESULTS

During an average follow-up of 1.9 +/- 1.1 years, there were 33 hard cardiac events (18 myocardial infarctions [MI] and 15 cardiac deaths) corresponding to an annual cardiac event rate of 5.8%/year, which is significantly higher than the event rate for patients referred for exercise SPECT imaging at our institution (2.2%/year). Event rates were higher after an abnormal dobutamine (99m)Tc-sestamibi SPECT study (10.0%/year) than after a normal study (2.3%/year) (p < 0.01), even after adjusting for clinical variables. In the subgroup (n = 29) with dobutamine-induced ST-segment depression and abnormal SPECT imaging, the prognosis was poor, with annual cardiac death and nonfatal MI rates of 7.9% and 13.2%, respectively.

CONCLUSIONS

Patients referred for dobutamine perfusion imaging are a high-risk population, and dobutamine stress (99m)Tc-sestamibi SPECT imaging is capable of risk stratification in these patients.

Cardiac nuclear medicine in monitoring patients with coronary heart disease

Patient monitoring is a major indication for cardiac nuclear medicine procedures. Stress myocardial perfusion scintigraphy was initially used for diagnosis, but monitoring patients with coronary artery disease has become more common. Stress myocardial perfusion scintigraphy has been shown to provide a considerable amount of incremental prognostic information, which may be useful in selecting patients for therapy. In patients being considered for revascularization, fluorodeoxyglucose can be used to identify regions of dysfunctional but viable myocardium, even within regions that show fixed defects on stress perfusion imaging. It can be used to select a group of patients who will improve function with revascularization and who may have an improved outcome. Thus, cardiac nuclear medicine plays a pivotal role in monitoring patients with coronary artery disease.

Enhanced detection of reversible perfusion defects by Tc-99m sestamibi compared to Tc-99m tetrofosmin during vasodilator stress SPECT imaging in mild-to-moderate coronary artery disease

OBJECTIVES

We prospectively compared dipyridamole single-photon emission computed tomography (SPECT) imaging with Tc-99m sestamibi and Tc-99m tetrofosmin for the detection of reversible perfusion defects in patients with mild-to-moderate coronary artery disease.

BACKGROUND

Tc-99m tetrofosmin has a lower first-pass myocardial extraction fraction compared to Tc-99m sestamibi and thus could underestimate mild perfusion defects.

METHODS

Eighty-one patients with 50% to 90% stenosis in one or two major epicardial vessels without previous myocardial infarction, and seven with <5% probability of coronary artery disease underwent dipyridamole SPECT imaging with both agents. The SPECT data were analyzed quantitatively.

RESULTS

Tc-99m sestamibi detected reversible perfusion defects in a greater number of segments (total 363 and 285, p < 0.001, and mean +/- SD, 2.2 +/- 3.0 and 1.8 +/- 2.5 per patient, p = 0.008, for Tc-99m sestamibi and Tc-99m tetrofosmin, respectively), demonstrated a larger extent of perfusion defect (mean +/- SD, 15.8% +/- 12.3% and 12.0% +/- 11.4%, p < 0.03, for Tc-99m sestamibi and Tc-99m tetrofosmin, respectively) and more often correctly identified patients with disease in more than one coronary artery (p = 0.02). There was better defect contrast with Tc-99m sestamibi (defect/normal wall count ratios were 0.60 +/- 0.15 vs. 0.73 +/- 0.14 for Tc-99m sestamibi and Tc99m tetrofosmin, respectively, p = 0.01, for reversible defects seen in identical segments with both agents; and 0.73 +/- 0.16 vs 0.79 +/- 0.17, respectively, p <0.01, for reversible defects detected with either agent alone). There was no significant difference in diagnostic sensitivity or image quality.

CONCLUSIONS

These differences between two commonly used tracers may have significant diagnostic and prognostic implications.

Pharmacological stress testing

Pharmacological stress in conjunction with radionuclide myocardial perfusion imaging has become a widely used noninvasive method of assessing patients with known or suspected coronary artery disease. In the United States, over one third of perfusion imaging studies are performed with pharmacological stress. Pharmacological stress agents fall into two categories: coronary vasodilating agents such as dipyridamole and adenosine, and cardiac positive inotropic agents such as dobutamine and arbutamine. For both, in the presence of coronary artery disease (CAD), perfusion image abnormalities result from heterogeneity of coronary blood flow reserve. Vasodilating agents work directly on the coronary vessels to increase blood flow, whereas inotropic agents work indirectly by increasing myocardial work load, which then leads to an increase in coronary blood flow. Both classes of agents have high accuracies for diagnosing coronary artery disease, and they have excellent safety records with acceptably low occurrences of side effects. For dipyridamole planar thallium imaging, pooled analysis yields a sensitivity of 85% and a specificity of 87% for diagnosis of coronary disease, but there is a large variation in reported values depending on various factors, such as the extent of postcatheterization referral bias, the type of imaging (planar versus single photon emission computed tomography [SPECT]), the types of patients being studied (single versus multivessel disease, men versus women), and the imaging agent used (thallium versus one of the technetium-based agents). Diagnostic accuracies for adenosine are similar to those of dipyridamole, with reported overall sensitivities ranging from 83% to 97%, and specificities ranging from 38% to 94%. For dobutamine, pooled analyses yield a sensitivity of 82% and a specificity of 75%. There is some concern that dobutamine may interfere with uptake of technetium-99m sestamibi, lowering the sensitivity for detection of disease, and thus the vasdodilating agents are generally preferred. Pharmacological stress testing has high clinical use for risk stratifying patients with known or suspected CAD, in patients after myocardial infarction, and in patients needing noncardiac surgery. Vasodilating agents are particularly advantageous in assessing post-myocardial infarction patients, allowing testing as soon as 2 days after the event. Like patients undergoing exercise stress testing, patients with normal perfusion images by pharmacological stress have a <1% annual incidence of cardiac events. The likelihood of an event increases with the extent and severity of perfusion abnormalities. However, it is important to consider clinical variables when using perfusion imaging for risk stratification, particularly in the presurgery patients. As with exercise testing, adjunct markers such as ST segment depression during testing, lung uptake of radiotracer (if thallium is used), and ventricular cavity dilatation add additional prognostic information to that available from the perfusion images alone. The aim of current research is to find better agents that are easier to use and that have fewer side effects. MRE-0470 is an experimental vasodilating agent that is more receptor selective than adenosine and promises a lower incidence of hypotension. Arbutamine more closely simulates exercise than dobutamine, and it can be administered by a closed-loop computerized delivery device. Work is also underway to look at novel uses of pharmacological stress agents, such as acquiring gated SPECT images during dobutamine infusion to enhance detection of myocardial viability. With increasing use of noninvasive testing in elderly patients and in patients with comorbidities that preclude adequate exercise, pharmacological stress testing has become an indispensable tool for radionuclide myocardial perfusion imaging studies. A good understanding of pharmacological stress testing is essential for performing high-quality nuclear cardiology

Technetium Tc 99m sestamibi myocardial perfusion imaging: current role for evaluation of prognosis

Like 201Tl imaging, technetium Tc 99m sestamibi (MIBI) myocardial imaging can be used with exercise and pharmacologic testing to assess the presence of coronary artery disease. An increasing body of literature indicates that MIBI can also be used to assess risk of future cardiac events such as myocardial infarction or death. This article summarizes the current status of MIBI imaging for evaluating prognosis in patients with known or suspected coronary artery disease.

Value of negative dobutamine stress echocardiography in predicting long-term cardiac events

To determine the value of negative dobutamine stress echocardiography (DSE) results in predicting subsequent long-term cardiac event rates, we retrospectively reviewed all dobutamine stress echocardiograms performed at our institution over a 3-year period (1992-1994). Follow-up was accomplished through the completion of a detailed questionnaire compiled from data obtained through chart review and direct telephone contact. Information regarding death also was determined by referencing patient data with mortality data available on the World Wide Web. Event rates were determined for hard (myocardial infarction [MI] or cardiac death) and soft (hospitalization for angina and/or congestive heart failure, coronary angioplasty, or coronary bypass surgery) cardiac events occurring after the negative DSE results for up to 7 years after the test. Negative test results were defined as those showing no new or worsening wall motion abnormalities after either a normal resting echocardiogram (normal-negative [NN]) or an abnormal segmental resting echocardiogram (fixed-negative [FN]).

RESULTS

Of the 346 interpretable tests, 224 were negative for inducible wall motion abnormalities, with 171 NN and 53 FN. In the NN group, the MI rate was 1.5% per patient/year, and the mortality rate was 0.13% per patient/year. In the FN group, the MI rate was 0.7% per patient/year, and the mortality rate was 0% per patient/year.

CONCLUSIONS

DSE results in both NN and FN groups predict a very low subsequent hard event rate and mortality for up to 5 years after the test.

Dobutamine stress echocardiography in the prediction of acute or chronic myocardial infarction

BACKGROUND

We assessed the value of dobutamine stress echocardiography (DSE) in predicting cardiac events in patients with acute or chronic myocardial infarction (MI), and we studied the association between DSE and these events.

METHODS AND RESULTS

Two hundred sixty-six patients (mean [+/-SD] age 65.3 +/- 11.4 years) with acute (n = 139) or chronic (n = 127) MI were recruited from March 1995 through April 1997. Both groups underwent DSE and were followed up for an average of 14.1 +/- 8.0 months. DSE was positive in 111 (79.9%) patients with acute MI and 65 (51.2%) patients with chronic MI (P <.0001 ). Positive DSE results were associated with a higher rate of all cardiac events (cardiac mortality rate, reinfarction, and unstable angina) than negative DSE results in both patients with acute MI and patients with chronic MI (44 in 111 patients vs 6 in 28 patients, P =.052, and 31 in 65 patients vs 10 in 62 patients, P <.0001, respectively). Among patients with acute MI, the positive and negative predictive values of DSE for all cardiac events were 39.6% (95% confidence interval [CI] 30.5% to 48. 7%) and 78.6% (95% CI 63.4% to 93.8%), respectively. In chronic MI, the positive and negative predictive values were 47.7% (95% CI 35.5% to 59.8%) and 83.9% (95% CI 74.7% to 93.0%), respectively. In both acute (P =.03) and chronic (P <.0001 ) MI, positive DSE findings were independent predictors of all cardiac events.

CONCLUSIONS

DSE is useful for predicting cardiac events. A positive finding on DSE is an independent predictor of cardiac events after both acute and chronic MI, whereas a negative DSE result predicts a low likelihood of subsequent cardiac events.

Risk assessment using single-photon emission computed tomographic technetium-99m sestamibi imaging

OBJECTIVES

This review summarizes the results of single-photon emission computed tomographic (SPECT) technetium-99m (Tc-99m) tracer imaging in patients with stable symptoms, patients with acute coronary syndromes, patients undergoing major non-cardiac surgery and patients with chest pain in the emergency department.

BACKGROUND

Previous studies have examined the prognostic value of stress thallium imaging in several subsets of patients with ischemic heart disease. At present, >50% of myocardial perfusion studies are performed with technetium-labeled tracers in the United States. Furthermore, there is a shift from diagnostic to the prognostic utility of stress testing. There are important differences between technetium-labeled tracers and thallium-201. It is therefore important to review the prognostic value of technetium-labeled tracers.

METHODS

We analyzed published reports in English on risk assessment using Tc-99m perfusion tracers. Results. The largest experience is in patients with stable symptoms, comprising >12,000 patients in 14 studies. In these patients, normal stress SPECT sestamibi images were associated with an average annual hard event rate of 0.6% (death or nonfatal myocardial infarction [MI]). In contrast, patients with abnormal images had a 12-fold higher event rate (7.4% annually). Both fixed and reversible defects are prognostically important, and quantitative analysis shows increased risk in relation to the severity of the abnormality. These results are similar to those obtained with thallium-201.

CONCLUSIONS

Patients with stable chest pain syndromes and normal stress SPECT sestamibi images have a very low risk of death or nonfatal MI. It is highly unlikely that coronary revascularization can improve survival in such patients. Patients with abnormal images have an intermediate to high risk for future cardiac events, depending on the degree of the abnormality. Further prospective studies comparing aggressive medical therapy with coronary revascularization in these patients are warranted.

Inotropic stress with arbutamine is superior to vasodilator stress with dipyridamole for the detection of reversible ischemia with Tc-99m sestamibi single-photon emission computed tomography

BACKGROUND

There is a paucity of data comparing the relative merits of inotropic and vasodilator stress Tc-99m sestamibi single-photon emission computed tomography (SPECT) for the detection of coronary artery disease and reversible ischemia.

METHODS AND RESULTS

Twenty-seven patients referred for diagnostic coronary arteriography underwent separate day dipyridamole and arbutamine Tc-99m sestamibi SPECT imaging with simultaneous two-dimensional echocardiography. The sensitivity of arbutamine and dipyridamole Tc-99m sestamibi for the detection of coronary artery disease was 100% (21 of 21) and 90% (19 of 21), respectively, with a specificity of 66% (4 of 6) for both. Coronary artery disease was detected in all six patients with single vessel disease by both stress modalities. The sensitivity for prediction of multivessel disease was 66% (10 of 15) for arbutamine and 46% (7 of 15) for dipyridamole stress. Arbutamine stress induced a greater extent and severity of perfusion abnormality at peak stress (peak perfusion score 25 +/- 6.2 and 21 +/- 5.9 for arbutamine and dipyridamole, respectively, p = 0.001) and reversible perfusion defects (difference between peak stress and rest scores 8.8 +/- 5.5 and 5.2 +/- 4.4 for arbutamine and dipyridamole, respectively, p = 0.001). Furthermore a significantly higher percentage of reversible defects induced by arbutamine stress was associated with wall thickening abnormality on simultaneous echocardiography, which is a more specific marker of myocardial ischemia (88% and 24% for arbutamine and dipyridamole, respectively, p = 0.002).

CONCLUSION

Inotropic stress may be superior to vasodilators for the determination of the extent and severity of myocardial involvement and reversible ischemia by Tc-99m sestamibi SPECT.

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.

Prognostic value of dobutamine stress echocardiography in patients undergoing diagnostic coronary arteriography

There are only a few studies addressing the prognostic value of dobutamine stress echocardiography in patients with suspected coronary artery disease and none have assessed its value compared with coronary arteriography. Accordingly, graded dobutamine stress echocardiography was performed in 121 patients who underwent coronary arteriography based on symptoms and the findings of treadmill exercise electrocardiography. During the follow-up period of mean (SD) months (15 +/- 9) there were 41 cardiac events (death [n = 5], acute myocardial infarction [n = 2], unstable angina [n = 29], and congestive heart failure [n = 5]). There were a greater number of patients with inducible wall motion abnormality (88%) on dobutamine stress with cardiac events compared with those without (55%, p <0.001). The wall motion score indexes at rest (1.6 +/- 0.6) and at peak stress (2.1 +/- 0.8) were worse in patients with cardiac events compared with those without (1.2 +/- 0.3, p <0.001 and 1.5 +/- 0.6, p <0.001, respectively). When multivariate analysis was performed using clinical, exercise, echocardiographic, and coronary arteriographic data the independent predictors of cardiac events were exercise duration (p = 0.01), presence of inducible wall motion abnormality (p = 0.03), and wall motion score index at peak stress (p <0.001). Thus, dobutamine stress echocardiography is a powerful predictor of future cardiac events in patients undergoing exercise testing and coronary arteriography for evaluation of chest pain and is superior to both exercise electrocardiography and coronary arteriography for the prediction of subsequent cardiac events.

Comparison of arbutamine stress 99mTc-labeled sestamibi single-photon emission computed tomographic imaging and echocardiography for detection of the extent and severity of coronary artery disease and inducible ischemia

BACKGROUND

Arbutamine is a new synthetic catecholamine developed specifically for pharmacologic stress testing.

METHODS AND RESULTS

We investigated 39 patients undergoing coronary arteriography to compare arbutamine stress (99m)Tc-labeled sestamibi single-photon emission computed tomographic imaging and echocardiography for detection of the extent and severity of coronary artery disease and inducible ischemia. Rest and stress studies were analyzed blindly according to a 12-segment left ventricular model for both techniques. Each segment was graded according to severity of wall thickening abnormality and perfusion defect (1 = normal to 4 = severe). Total perfusion defect and wall thickening scores were calculated at peak stress and the difference in scores between stress and rest (delta perfusion defect; delta wall thickening) were used as indexes of inducible ischemia. Twenty-one patients had multivessel disease, nine had single-vessel disease, and nine had normal coronary arteries. Diagnostic accuracies for the detection of coronary artery disease for single-photon emission computed tomographic imaging and echocardiography were 95% and 92%, respectively. Extent and severity of coronary artery disease indicated by a peak stress perfusion defect score of 26 +/- 6.4 and wall thickening score of 25.1 +/- 8.4 were similar, and there was no significant difference in the delta perfusion defect and delta wall thickening scores of 8.7 +/- 5.5 and 10.4 +/- 7.1, respectively. Segmental concordance rates for the detection of coronary artery disease and inducible ischemia were 74% (K = 0.47; confidence interval 0.39 to 0.55) and 74% (kappa = 0.42; confidence interval 0.34 to 0.51), respectively. Regional concordance for coronary artery disease was 84% (kappa = 0.68; confidence interval 0.51 to 0.84). Where discordance was present, there was a greater prevalence of perfusion abnormality compared with wall thickening abnormality.

CONCLUSION

Arbutamine stress single-photon emission computed tomographic imaging and echocardiography provide largely equivalent and accurate pathophysiologic information for the evaluation of coronary artery disease and inducible ischemia.

Prognostic importance of scintigraphic left ventricular cavity dilation during intravenous dipyridamole technetium-99m sestamibi myocardial tomographic imaging in predicting coronary events

Left ventricular (LV) cavity dilation during stress myocardial perfusion imaging has been associated with multivessel disease, and may be an independent prognostic marker in addition to perfusion defects. The present study examines the predictive value for future cardiac events of transient or fixed LV dilation during dipyridamole technetium-99m (Tc-99m) sestamibi single-photon emission computed tomography (SPECT) imaging. The study included 512 consecutive patients who underwent SPECT imaging with Tc-99m sestamibi after dipyridamole infusion. Transient LV dilation was seen in 70 patients (14%) and 74 had fixed cavity dilation (14%); cavity size was normal in 368 patients (72%). Each perfusion scan was classified as normal or abnormal, and if abnormal, defects were categorized as transient or fixed, and as small, medium, or large (depending upon the number of abnormal vascular territories). Events during a mean follow-up of 12.8 +/- 6.8 months were tabulated by direct review of hospital charts and death certificates. The cardiac event rate (cardiac death or nonfatal infarction) was 1.9% in patients with normal cavity size, 11.4% with transient LV dilation, and 13.5% with fixed LV dilation (p < 0.01). Compared with patients with normal cavity size, those with transient LV dilation were more likely to sustain a myocardial infarction (p < 0.01) and those with fixed dilation more frequently suffered cardiac death (p < 0.01) and hospitalization for heart failure (p < 0.01). The group with the highest risk had both a large perfusion defect and cavity dilation. By Cox proportional hazard regression analysis, both transient and fixed LV dilation were strong independent predictors of cardiac events. Transient or fixed LV dilation are commonly seen during dipyridamole Tc-99m sestamibi SPECT imaging (14% incidence for each) and are useful predictors of cardiac events.

Potential cost effectiveness of initial myocardial perfusion imaging for assessment of emergency department patients with chest pain

Previous investigations have confirmed the diagnostic and predictive usefulness of initial single-photon emission computed tomography (SPECT) myocardial perfusion imaging using technetium-99m sestamibi in the evaluation of emergency department patients with chest pain. Patients with a normal SPECT perfusion scan performed during chest pain have an excellent short-term prognosis, and may be candidates for expeditious cardiac evaluation or outpatient management. However, there are limited data regarding the cost effectiveness of this technique. This analysis models the potential cost effectiveness of this procedure. In the current investigation we compared 2 model strategies for management of emergency department patients with typical chest pain and a normal or nondiagnostic electrocardiogram (ECG). In 1 model strategy, (the technetium-99m sestamibi SPECT myocardial perfusion imaging [SCAN] strategy), the decision whether to admit or discharge a patient from the emergency department is based on results of initial technetium-99m sestamibi SPECT myocardial imaging. Patients with normal scans are discharged; others are admitted. In the second model strategy, (the NO SCAN strategy), the decision whether or not to admit a patient is based on a combination of clinical and electrocardiographic variables. Patients with > or = 3 cardiac risk factors or an abnormal ECG are admitted; others are discharged. Adverse cardiac events were prospectively defined as cardiac death, nonfatal myocardial infarction, or the need for acute coronary intervention. Costs were assigned using data derived from 102 patients who underwent SPECT myocardial perfusion imaging and an additional 107 emergency department patients with ongoing chest pain who either underwent or were eligible for initial SPECT myocardial perfusion imaging. Mean (+/- SE) costs were highest among hospital admitted patients who experienced an adverse cardiac event ($21,375 +/- $2,733) and lowest in patients discharged from the emergency department ($715 +/- 71). Mean costs per patient of the SCAN strategy and NO SCAN strategy were $5,019 versus $6,051, respectively. These results were stable in a sensitivity analysis across a range of costs and predictive values. Thus, the SCAN model strategy for initial management of emergency department patients with typical ongoing angina and a normal or nondiagnostic ECG using initial myocardial perfusion imaging with technetium-99m sestamibi appears to be safe, accurate, and potentially cost effective. Validation of these preliminary retrospective observations will require further prospective investigation.

ECG-manifest and ECG-silent dipyridamole technetium-99m sestamibi SPET perfusion defects in patients with ischaemic heart disease

At dipyridamole myocardial scintigraphy, perfusion defects are seldom backed up by significant ECG changes. This would suggest myocardial blood flow heterogeneity, rather than true ischaemia, as the cause of the scintigraphic abnormalities. Electrocardiographic surface mapping has been documented to be more accurate than standard 12-lead ECG in the detection of provoked ischaemia. Thus, to investigate the relationship between ECG changes and perfusion abnormalities, body surface maps were recorded during dipyridamole infusion in 55 subjects (11 normals and 44 patients with ischaemic heart disease) undergoing dipyridamole technetium-99m sestamibi single-photon emission tomography (SPET). All had a normal resting ECG. The extent and severity of the sestamibi defect were quantified. New negative areas in the isointegral maps and rest-dipyridamole map differences >2 SD from normal limits were considered abnormal. After dipyridamole in normals, neither perfusion defects nor >/=1 mm ST segment depression on 12-lead ECG nor new negative areas in isointegral maps occurred. In patients, dipyridamole induced new perfusion defects in 35 (80%) but ST segment depression in only 18 (41%, P<0.001). Of the 35 patients with perfusion defects, 17 (49%, group 1) showed ST segment depression, while the other 18 (51%, group 2) did not. Abnormal body surface maps were found in 100% of group 1 and 88% of group 2 patients (NS). In group 1, the provoked hypoperfusion was of greater extent (P=0.007) and severity (P=0.01) and the onset of map abnormalities was significantly earlier (P<0. 001) than in group 2; time to map abnormalities was also significantly shorter than time to ST segment depression (P=0.01). In the 35 patients with complete scintigraphic, body map and angiographic data, the severity of reversible perfusion defect proved to be the strongest correlate of ST segment depression upon logistic regression analysis. Thus, sestamibi SPET abnormalities after dipyridamole are almost always associated with electrical changes on body surface maps, suggesting myocardial ischaemia as their cause. The much less common 12-lead ECG changes are slower to appear and reflect a more severe hypoperfusion.