Value of gated SPECT myocardial perfusion imaging for individual cardiac risk assessment

Myocardial perfusion imaging enables not only accurate diagnosis of disease but also entails prognostic value. Myocardial perfusion SPECT contributes to assessment of future cardiac events independently of other clinical parameters. A normal stress myocardial perfusion scan is associated with a favorable prognosis independent of history, symptoms, and exercise electrocardiography test variables. Cardiac risk and benefit from invasive therapeutic strategies increase in relation to the severity of the abnormality of perfusion and function assessed by gated myocardial perfusion SPECT. Thus, stress myocardial perfusion imaging may serve as a gatekeeper for referral to coronary angiography enabling effective risk stratification in patients with suspected or documented coronary artery disease.     

Principal uses of myocardial perfusion scintigraphy in the management of patients with known or suspected coronary artery disease

The use of myocardial perfusion single photon emission computed tomography (SPECT) has undergone considerable expansion and evolution over the past 2 decades. Although myocardial perfusion imaging was first conceived as a noninvasive diagnostic tool for determining the presence or absence of coronary artery disease, its prognostic value is now well established. Thus, identification of patients at risk for future cardiac events has become a primary objective in the noninvasive evaluation of patients with chest pain syndromes and among patients with known coronary artery disease. In particular, the ability of myocardial perfusion SPECT to identify patients at low (< 1%), intermediate (1% to 5%) or high (> 5%) risk for future cardiac events is essential to patient management decisions. Moreover, previous studies have conclusively shown the incremental prognostic value of myocardial perfusion SPECT over clinical and treadmill exercise data in predicting future cardiac events. This report addresses the current role and new developments, with respect to the use of myocardial perfusion imaging, in determining patient risk for cardiac events and the cost-effective integration of such information into patient management decisions.     

Stress echocardiography

Stress echocardiography has become an accepted noninvasive method for the diagnosis of coronary artery disease. Stress echocardiography is more sensitive than exercise electrocardiography and as sensitive and specific as radionuclide perfusion studies for detecting coronary artery disease. Pharmacologic stress echocardiography using dobutamine also has excellent diagnostic accuracy for patients who are unable to exercise. Dobutamine stress echocardiography can provide prognostic data to determine perioperative cardiac risks in patients who are undergoing vascular surgery.     

The diagnostic and prognostic value of exercise electrocardiography in asymptomatic subjects and stable symptomatic patients

In asymptomatic patients, the use of exercise ECG testing for the detection of subclinical coronary artery disease has considerable theoretical appeal, but its practical application is severely hampered by the constraints of Bayes' theorem. Serial exercise ECGs do not appear to offer significant improvement in this regard. Thallium-201 perfusion scintigraphy performed in conjunction with an exercise ECG can greatly improve the predictive value of such testing, although at considerable cost. Screening strategies with promise are those that reserve exercise testing for individuals at greater-than-average risk for subclinical coronary artery disease (eg, patients with multiple coronary risk factors) or that prescribe sequential testing, where only those with an abnormal exercise ECG are subjected to thallium-201 scintigraphy. At present, the optimal method of identifying asymptomatic individuals at high risk of a major cardiac event remains undefined. The use of maximal-effort stress testing has stood the test of time in the evaluation of patients with stable symptoms suggestive of coronary artery disease. This is particularly true when variables other than the ECG response to exercise are considered. The independent contribution of exercise angina remains controversial; however, recent studies indicate that it correlates with a more severe symptom pattern and more extensive coronary artery disease. Prognostic stratification in these studies was improved by considering both subjective and objective manifestations of ischemia. Although exercise ECG testing has been shown to have important prognostic value after acute myocardial infarction, exercise thallium-201 scintigraphy offers several potential advantages for asymptomatic post-myocardial infarction patients, several of which this paper reviews. The more optimal prognostic efficiency of thallium-201 scintigraphy is due in part to the fact that the error rate in falsely classifying patients at low risk is substantially smaller with scintigraphy than with stress electrocardiography. Because of this, there appears to be adequate rationale for recommending exercise perfusion imaging, rather than exercise ECG testing alone, as the preferred method for evaluating mortality and morbidity risks after acute myocardial infarction.     

Comparison of exercise thallium-201 perfusion scintigraphy and coronarography in the prognostic stratification of patients with post-infarction residual ischemia]

The goals of this study were: 1) to determine and compare the prognostic utility of exercise 201Thallium scintigraphy with coronary angiography in patients with residual ischemia at the symptom limited bicycle exercise testing performed at hospital discharge after a first uncomplicated acute myocardial infarction 2) to verify the ability of perfusion scintigraphy to identify better than coronary angiography a subset of these patients at low risk for future events, despite the ischemic response at the exercise stress testing. Accordingly, follow-up data were obtained prospectively for 72 consecutive patients with adequate left ventricular rest systolic function, and with exercise induced greater than or equal to 1 mm ST-segment depression and/or typical angina pectoris. A planar 201Thallium scintigraphy and coronary angiography were performed within 2 months after acute myocardial infarction. By 31 +/- 29 months 38 patients had no events, while 34 experienced a cardiac event: 3 died of cardiac causes, 2 had nonfatal recurrent myocardial infarction, 29 were rehospitalized for severe class III or IV angina pectoris (4 were treated medically, 25 were revascularized: 20 had coronary bypass surgery, 5 coronary angioplasty). Each of the 3 angiographic classification of coronary artery disease (number of vessels with greater than or equal to 70% reduction of luminal diameter, jeopardy score and Gensini score) accurately identified patients with subsequent cardiac event by Mantel and Cox analysis (respectively p = 0.01, p = 0.0000, p = 0.002). Among 201Thallium variables, the number of segments demonstrating redistribution on delayed images (p = 0.0000), the number of segments with persistent defect (p = 0.0003) and increased 201Thallium uptake by the lungs (p = 0.0100) effectively stratified the probability of survival by the same analysis. Furthermore, the number of perfusion defects, either transient or persistent, with exercise 201Thallium scintigraphy provide additive prognostic information to any of the 3 angiographic coronary artery disease classifications considered. On the contrary, when 201Thallium stress findings are known, coronary angiography data in general are not additive in risk stratification. 17 patients with no reversible perfusion defect remained stable at follow up (52 +/- 28 months) despite development of typical angina pectoris (11/17) and/or ischemic ST segment depression (12/17) during exercise testing.(ABSTRACT TRUNCATED AT 400 WORDS)     

Limited usefulness of exercise testing and thallium scintigraphy in evaluation of ambulator patients several months after recovery from an acute coronary event: Implications for management of stable coronary heart disease

Objectives. This study evaluated the value of noninvasive testing to predict cardiac events in patients with stable coronary disease after hospital admission (and risk stratification) for an acute coronary event.Background. Exercise testing with thallium perfusion imaging identifies patients with obstructive coronary artery disease and has been used to stratify patients after myocardial infarction. Its usefulness for predicting cardiac events in patients with stable coronary disease after recovery from an acute coronary event was explored.Methods. Nine hundred thirty-six patients were enrolled 1 to 6 months after hospital admission for a coronary event Patients underwent exercise treadmill testing with planar thallium-201 scintigraphy and were followed up for an average of 23 months (range 6 to 43). End points were 1) unstable angina requiring hospital admission, nonfatal myocardial infarction or cardiac death; 2) nonfatal infarction or cardiac death; or 3) cardiac death alone.Results. Twelve patients died of cardiac causes (1.2%); 32 had a nonfatal myocardial infarction (3.4%); and 79 patients (8.4%) developed unstable angina in the first year. Exercise testing improved proportional hazards models constructed from clinical variables for all three end points (p < 0.05). The perfusion scan further improved models for the end points (nonfatal infarction or cardiac death and cardiac death alone, p < 0.05). However, the exercise test with or without thallium added little to the overall prediction of primary events (area under the receiver operating curve increased from 0.649 to 0,663), and only 2% to 13% of patients with abnormal results either had a nonfatal infarction or died.Conclusions. Thallium-201 scintigraphy and exercise testing variables identify patients at risk for subsequent cardiac events. However, the poor predictive performance of these tests in this group of patients with stable coronary disease severely limits their usefulness. These results suggest a limited role for exercise and thallium testing in predicting cardiac events in patients with known coronary disease.     

Exercise thallium-201 scintigraphy in men with nondiagnostic exercise electrocardiograms. Prognostic implications

We studied the prognostic value of exercise thallium-201 imaging in 196 men with suspected or known coronary artery disease who had nondiagnostic exercise electrocardiograms. The perfusion images in each of three projections were divided into three segments; each segment was assessed for perfusion defects (fixed or reversible). There were 12 cardiac events at a mean follow-up of 15 months (range, one to 66 months). Of those, five patients died of cardiac causes and seven had nonfatal acute myocardial infarctions (MIs). Only the number of perfusion defects significantly predicted cardiac events; clinical presentation, history of MI, presence of Q-wave MI, exercise duration, and exercise heart rate and double product did not predict cardiac events or add to information provided by the number of defects. Furthermore, actuarial life-table analysis showed that patients with three or more perfusion defects had significantly worse prognoses than patients with fewer than three defects. Exercise thallium-201 imaging helps in risk stratification of men with nondiagnostic exercise electrocardiograms.     

Evaluation of the patient with diabetes mellitus and suspected coronary artery disease

Coronary artery disease (CAD) is the leading cause of morbidity and mortality in patients with diabetes mellitus. In fact, patients with diabetes have the same risk of myocardial infarction as do nondiabetic subjects with a history of infarction. For this reason, diabetes has been designated by the American College of Cardiology (ACC) and the American Heart Association (AHA) as a CAD equivalent. For women, data indicate a substantially elevated risk of cardiovascular disease (CVD) even before a clinical diagnosis of type 2 diabetes has been made. Identifying patients with diabetes who have CAD and who will benefit from medical and/or invasive intervention to prevent cardiovascular events is a challenge in both symptomatic and asymptomatic patients. The decision to evaluate patients with diabetes who are asymptomatic for CAD presents the greatest challenge; investigation will reveal 10% to 15% of these patients to have CAD. Current diagnostic tools include exercise tolerance testing, stress echocardiography, stress myocardial perfusion imaging (MPI), and cardiac catheterization. Few guidelines are available to aid in the choice of testing modalities for a given patient. Although cardiac catheterization is useful, it is generally reserved for patients in whom invasive intervention is suitable. The American Diabetes Association (ADA) recommends exercise tolerance testing alone in symptomatic patients with > or = 2 CAD risk factors or an abnormal resting electrocardiogram (ECG). However, that recommendation is not based on data; it is the consensus of an expert panel. Stress echocardiography is a useful, noninvasive procedure; however, there is limited experience with this technology in the diabetic population. Recently accumulated data support both diagnostic and prognostic roles for stress MPI, particularly with ECG-gated single-photon emission computed tomographic imaging. In symptomatic patients with diabetes, the presence and extent of abnormal stress MPI findings have been found to be highly accurate independent predictors of subsequent cardiac events: 18% to 26% of asymptomatic patients with diabetes have perfusion defects consistent with CAD. However, CVD risk factors are not predictive of abnormal MPI findings even though duration of diabetes and abnormal ECGs are. The results of future studies may be helpful in guiding the selection of asymptomatic patients to undergo myocardial perfusion and function studies. In conclusion, MPI provides clinicians with an important diagnostic tool, because it offers perfusion as well as functional information for diagnosis and risk stratification in patients with diabetes. These capabilities facilitate decision making regarding the appropriateness of medical therapy or surgical intervention in these individuals.     

Stress nuclear myocardial perfusion imaging versus stress echocardiography: prognostic comparisons

The use of noninvasive stress cardiac imaging for stratifying risk in patients with known or suspected coronary artery disease is growing as a tool for identification of the subgroup most likely to benefit from the expense and risk of more invasive procedures, including cardiac catheterization and coronary revascularization. In this setting, it is especially important that a test be able to identify patients with sufficiently low risk that clinicians are comfortable in deferring such interventions, especially in those with other markers of increased risk. Previous data have shown that cardiac risk is most closely related to the presence and extent of jeopardized viable myocardium on noninvasive stress cardiac imaging. Although stress echocardiography may have comparable ability to detect coronary artery disease, current data suggest that stress echocardiography detects significantly less jeopardized viable myocardium than stress nuclear myocardial perfusion imaging and consequently fewer patients at risk for cardiac events. Stress nuclear myocardial perfusion imaging may therefore have important advantages for risk stratification and the direction of future care of patients with known or suspected coronary artery disease.     

Noninvasive evaluation of cardiac risk before elective vascular surgery

The prognostic utility for predicting cardiac events was determined for dipyridamole-thallium scintigraphy, exercise stress testing (when possible; n = 69) and multiple clinical variables in 100 consecutive patients admitted for elective surgical repair of peripheral vascular disease. After initial noninvasive evaluation, 11 patients were referred for coronary angiography and the remaining 89 patients had surgery without further cardiac studies. Fifteen patients (17%) had a postoperative myocardial infarction, one of which was fatal. Of these 15 patients, 14 had thallium redistribution and 3 had positive ST segment depression during stress testing. Among the many variables tested, the presence of redistribution on serial dipyridamole-thallium images was the most significant predictor of serious cardiac events. All 11 patients who had coronary angiography had both redistribution and multivessel coronary artery disease. Four of these 11 patients died during follow-up and 6 had coronary artery bypass surgery. It is concluded that dipyridamole-thallium imaging has significant prognostic utility in predicting postoperative myocardial infarction and death in patients with severe peripheral vascular disease, and is superior to exercise testing or clinical variables in determining cardiac risk. The odds for a serious cardiac event were 23 times greater in a patient with thallium redistribution than in a patient without redistribution, strongly suggesting that myocardial imaging may be used as a primary screening test before elective vascular surgery.     

Enhanced prognostic stratification of patients with left ventricular hypertrophy with the use of single-photon emission computed tomography

BACKGROUND: Patients with left ventricular hypertrophy (LVH) are at increased risk of future cardiovascular events. Little is known about risk stratification of these patients with the use of myocardial perfusion imaging. This study sought to assess the prognostic stratification of patients with LVH by using myocardial perfusion single-photon emission computed tomography (SPECT). METHODS AND RESULTS: We studied 633 consecutive patients with electrocardiographic evidence of LVH who underwent dual isotope myocardial perfusion SPECT (rest thallium 201/stress technetium 99m sestamibi) and were followed up for a mean period of 22 +/- 7 months. During the follow-up period, 67 events (35 cardiac deaths and 32 nonfatal myocardial infarctions) occurred (6% annual event rate). The results of the perfusion scan significantly risk-stratified the population; patients with normal scans had a low rate of nonfatal myocardial infarction and cardiac death (<1% per year of follow-up). The rates of cardiac events increased significantly as a function of the scan result: 4.9% in patients with mildly abnormal scans and 10. 3% in moderately to severely abnormal scans. Cox proportional hazards analysis demonstrated that after adjusting for pretest likelihood of coronary artery disease (the most predictive clinical variable; chi(2) = 15.5, P <.001), summed stress score (the most predictive nuclear variable; chi(2) = 18, P <.0001) added significant incremental prognostic information (global chi(2) increased from 15.5 to 36; P <.001). CONCLUSIONS: In patients with LVH with an overall high cardiac event rate, SPECT provided enhanced stratification by adding significant incremental prognostic information over clinical and historic variables.     

Noninvasive Coronary Risk Stratification of Elderly Patients

The prognostic value of stress thallium-201 myocardial perfusion imaging has not been defined in an elderly (at or above 70 years) population. To this end, we studied 468 consecutive elderly patients undergoing either Bruce protocol exercise stress (n equals 120) or intravenous dipyridamole stress (n equals 348) with quantitative planar thallium-201 imaging. These patients were followed for at least 2 years after testing to determine their rates of cardiac events (cardiac death, myocardial infarction, coronary revascularization). There were no stress-related complications in either subgroup. A 10% cardiac event rate (6 deaths and 6 myocardial infarctions) was observed in the exercise subgroup. Survival without cardiac events was associated with greater exercise duration (5.6?+/-2.4 vs 3.1?+/-2.4 min; P is less than 0.001) and peak exercise heart rate (131?+/-18 vs 120?+/-19 bpm; P is less than 0.05). Multivariate analysis identified the combination of peak exercise at or below Stage 1 and thallium-201 perfusion defects as significant predictors of cardiac events (relative risk equals 5.3 at 1 year). Sixty-four percent of elderly patients were successfully stratified into very low and high risk subgroups, with annual cardiac event rates of less than 1% and greater than 15%, respectively. The cardiac event rate in dipyridamole stress patients was 22% (24 myocardial infarction, 52 death, 42 revascularization). The cardiac event rate was significantly lower (5%) in 150 patients with a normal dipyridamole thallium-201 study (P is less than 0.001). Clinical univariate predictors of cardiac events were previous myocardial infarction, congestive heart failure symptoms, hypercholesterolemia and diabetes (all P equals 0.05). A fixed, reversible, or combined thallium defect pattern was correlated with cardiac death or myocardial infarction (P is less than 0.05). Multivariate analysis demonstrated that the presence of an abnormal dipyridamole thallium study was the single-best predictor of cardiac events (relative risk equals 7.2; P is less than 0.01) We conclude that exercise and dipyridamole thallium-201 myocardial imaging are powerful independent noninvasive techniques for prognostication in the elderly patient population, a group with the potential for advanced coronary artery disease and a high risk of cardiac events.     

New developments in pharmacologic stress imaging.

The clinical usefulness of cardiac imaging modalities that rely upon the detection of perfusion defects and wall motion disturbances requires conditions that provoke a heterogeneity of coronary flow and a myocardial oxygen imbalance, respectively. Traditionally, this has been achieved by exercise stress testing. Many patients cannot perform dynamic exercise sufficiently for various reasons. Pharmacologic stress has been proven to be an attractive alternative for physical exercise. Currently, several stressing agents are used in conjunction with thallium-201 scintigraphy, 2-D echocardiography and, recently, MRI. The most employed agents include vasodilators, such as dipyridamole and adenosine, and catecholamines, such as dobutamine (Table VI). The predominant rationale of thallium-201 perfusion scintigraphy is based on the creation of a flow maldistribution between territories supplied by normal arteries and those supplied by stenotic arteries that does not necessarily require ischemia. Dipyridamole and adenosine, as rather selective coronary vasodilators, are well suited to provoke such a condition and may be classified as the ideal markers of myocardial perfusion. 2-D echocardiography and MRI have the potential to provide noninvasively derived information of cardiac dynamics and regional myocardial function. To assess the functional significance of coronary artery disease, detection of wall motion abnormalities and alterations in ejection fraction require the presence of myocardial ischemia. Dobutamine, as a widely applied inotropic agent in the management of severely depressed left ventricular contractile function, seems to be an appropriate pharmacologic stressor when heart failure is absent. By increasing contractility, heart rate, and systolic arterial pressure, it is capable of inducing an imbalance between myocardial oxygen demand and supply, leading to ischemia in patients with coronary artery disease.(ABSTRACT TRUNCATED AT 250 WORDS)     

Comparative analysis of the diagnostic and prognostic value of exercise ECG and thallium-201 scintigraphic markers of myocardial ischemia in asymptomatic and symptomatic patients

A considerable amount of data now exists that indicates that exercise ECG--due to its suboptimal sensitivity and specificity--has limited diagnostic and prognostic value in asymptomatic subjects, patients with chest pain of unclear etiology or those with chronic stable angina pectoris, and in patients recovering from acute myocardial infarction. Because of this and the well-recognized advantages of thallium-201 scintigraphy, there appears to be a strong rationale for recommending exercise perfusion imaging, rather than exercise ECG alone, as the preferred method for detecting CAD and staging its severity. This recommendation seems justified given the fact that (1) thallium-201 scintigraphy is far more sensitive and specific in detecting myocardial ischemia than exercise testing; (2) unlike stress ECG, thallium-201 scintigraphy can localize ischemia to a specific area of areas subtended by a specific coronary artery; and (3) thallium-201 scintigraphy has been shown to be more reliable to risk stratification of individual patients than exercise testing alone. The more optimal prognostic efficiency of thallium-201 scintigraphy is due, in part, to the fact that the error rate in falsely classifying patients as low-risk is substantially and significantly smaller with thallium-201 scintigraphy than with stress ECG.     

Risk stratification with electrocardiographic-gated dobutamine stress technetium-99m sestamibi single-photon emission tomographic imaging: value of heart rate response and assessment of left ventricular function.

OBJECTIVES: The purpose of this research was to evaluate the significance of heart rate response to dobutamine and the assessment of left ventricular (LV) function during risk stratification of patients undergoing dobutamine stress myocardial perfusion imaging (DSMPI). BACKGROUND: Dobutamine stress myocardial perfusion imaging has been shown to effectively risk stratify highly selected patients. However, based on perfusion alone, patients with normal and abnormal tests have twice the risk as comparable patients with exercise testing. The added value of assessment of LV function and the heart rate response to dobutamine in risk stratification of these patients is unknown. METHODS: Follow-up information (cardiac death or non-fatal myocardial infarction) was obtained on 1,367 consecutive patients who underwent DSMPI due to inability to perform adequate exercise and contraindications to vasodilators. Perfusion images were interpreted using a 17-segment model. Abnormal perfusion and function were defined as: summed stress score > or =4 and ejection fraction <50%, respectively. RESULTS: Annualized event rates (AERs) were related to the extent/severity of perfusion defects and worsening LV function. A three-risk category model was constructed from combined assessment of perfusion and function, with AERs of 2.4% (both normal), 5.8% (discordant), and 11.3% (both abnormal); p < 0.001. Stress electrocardiogram (ECG) data added incremental value to myocardial perfusion alone but not to combined assessment of perfusion and function. Importantly, inability to achieve 85% of mean predicted heart rate was associated with worse outcomes and was an independent predictor of cardiac events. For patients in whom perfusion, function, and stress ECG response were normal, inability to achieve target heart rate was associated with significantly higher AER (1.5% vs. 3.4%, respectively, p = 0.021). CONCLUSIONS: In highly selected patients undergoing DSMPI, assessment of perfusion and function is effective in risk stratification. The stress ECG and heart rate response to dobutamine have prognostic value and should be incorporated into image interpretation so as to maximize risk stratification.     

Nuclear cardiac imaging for the assessment of coronary artery disease in the elderly

Stress single photon emission computed tomography (SPECT) and positron emission tomography (PET), the standard clinical methods for measuring myocardial perfusion, have been extensively validated for diagnostic and prognostic purposes in general populations. Published data in the elderly are limited. The available data suggest that in elderly patients, SPECT is as accurate for diagnostic purposes as in younger patients and that stress SPECT is considerably more accurate for prognostic purposes when compared with standard treadmill testing. Pharmacologic stress testing can be performed in conjunction with SPECT and PET, representing another advantage of these techniques because many elderly patients cannot exercise to a high enough workload to provoke ischemia during testing.     

Stress echocardiography versus myocardial SPECT for risk stratification of patients with coronary artery disease

PURPOSE OF REVIEW: Diagnostic testing using noninvasive imaging has become an integral part of risk stratification in patients with coronary artery disease. It is important to understand the integral strengths and weaknesses between the different modalities of stress testing and to apply accurately the type of test the clinical scenario demands. RECENT FINDINGS: There have been tremendous advances made in the field of cardiac imaging. Both myocardial perfusion imaging and stress echocardiographic techniques continue to evolve and play an important role in the assessment of patients with coronary artery disease. SUMMARY: In this review the authors discuss the relative merits of both stress echocardiography and myocardial single photon emission computed tomographic imaging for diagnosis and risk stratification of patients with coronary artery disease.     

Preoperative risk stratification with myocardial perfusion imaging in intermediate and low-risk non-cardiac surgery.

BACKGROUND: Perioperative cardiac risk in high risk surgery is often stratified with myocardial perfusion single-photon emission computed tomography (SPECT). However, little and no data are available about intermediate and low-risk surgery, respectively. METHODS AND RESULTS: A total of 1,220 consecutive patients underwent electrocardiography-gated dipyridamole stress SPECT to evaluate myocardial perfusion and cardiac function before intermediate or low risk non-cardiac surgery. Variables predictive of perioperative cardiac events were determined and the usefulness of combining pretest information and the incremental prognostic value of SPECT was estimated. The frequency of all cardiac events depended on clinical risk factors and type of surgical procedures. After sorting the patients with clinical risk factors and surgical risk, assessment of myocardial perfusion or cardiac function yielded significant risk stratification in intermediate, but not in low-risk surgery. Adding functional data to perfusion variables offered an incremental prognostic value for patients with an intermediate clinical risk and scheduled intermediate risk surgery. CONCLUSIONS: Integrating information about clinical risk factors, type of surgery, myocardial perfusion and cardiac function allows detailed preoperative risk stratification. Preoperative SPECT provides an incremental prognostic value in intermediate, but not in low-risk surgery.     

The role of myocardial perfusion imaging in the diagnosis of patients with coronary artery disease: developments over the past year

PURPOSE OF REVIEW: The role of myocardial perfusion imaging in the diagnosis of coronary artery disease in various patient populations has been expanding. Recent literature from March 2004 to February 2005 has advanced the concept of attenuation correction and electrocardiographic gating in improving the diagnosis of coronary artery disease. RECENT DEVELOPMENTS: The American Heart Association encourages the use of electrocardiographic-gated single photon emission computerized tomography in women. Asymptomatic diabetic patients may benefit from screening with myocardial perfusion imaging. Dobutamine stress perfusion imaging is an important diagnostic tool in elderly patients who are unable to exercise. In patients with chest pain, acute imaging may decrease unnecessary admissions. Vasodilator stress imaging has high sensitivity and specificity in patients with left bundle branch block. Patients undergoing endovascular stent grafting may benefit from risk stratification with vasodilator myocardial perfusion imaging. The American Society of Nuclear Cardiology and the Society of Nuclear Medicine have recognized the role of attenuation correction in increasing the diagnostic accuracy of myocardial perfusion imaging. Multiple studies emphasize the importance of electrocardiographic gating in myocardial perfusion imaging. SUMMARY: Recent developments have resulted in an important statement by the American Heart Association that assigns a larger role for myocardial perfusion imaging in the diagnosis of coronary artery disease in women. The role of myocardial perfusion imaging is also expanding in various other patient populations. The literature has validated the concept of attenuation correction for the accurate assessment of attenuation artifacts as well as electrocardiographic gating in enhancing the diagnosis and risk stratification for coronary artery disease.     

Diagnostic and prognostic value of vasodilator stress echocardiography in asymptomatic Type 2 diabetic patients with positive exercise thallium scintigraphy: a pilot study.

AIM: To assess the diagnostic and prognostic value of vasodilator stress echocardiography in Type 2 diabetic patients with positive exercise perfusion scintigraphy. METHODS: Of an initial cohort of 50 asymptomatic Type 2 diabetic patients undergoing exercise single photon emission computed tomography (SPECT) thallium scintigraphy, 24 had a positive thallium scan, with a reversible perfusion defect. All these 24 underwent high dose (up to 0.84 mg/kg in 10 min) dipyridamole echocardiography and coronary angiography independently of stress echocardiography results. All patients were then followed for 61+/-22 months. RESULTS: Coronary angiography showed normal coronary arteries in 11 patients and significant (> 50% visually assessed diameter reduction in a major vessel) coronary artery disease in 13. Stress echocardiography showed 92% sensitivity and 100% specificity for non-invasive detection of coronary artery disease. During follow-up, five patients experienced cardiac events: heart failure in one, angina with subsequent revascularization in two, and myocardial infarction in two. Event-free survival was 100% in the 12 patients with negative and 58% in the 12 patients with positive stress echocardiography (P = 0.08 by Mantel-Cox test). CONCLUSIONS: In asymptomatic Type 2 diabetic patients with stress-induced perfusion defects, vasodilator stress echocardiography is an excellent diagnostic and prognostic tool proven with long-term follow-up.