Assessment of left ventricular wall motion in angina pectoris by two-dimensional echocardiography and myocardial perfusion by technetium-99m sestamibi tomography during adenosine-induced coronary vasodilation and comparison with coronary angiography

A systemic review of rubidium-82 PET contrasted with 99mTc-MIBI SPECT for imaging coronary artery disease

BACKGROUND

99mTc-sestamibi single photon emission tomography (SPECT) method is widely used for imaging coronary artery disease (CAD). 82-Rubidium-PET is an alternative method that can be used to perform the same purpose.

PURPOSE/AIM

This study aims to determine whether 82-Rubidium-PET can offer extra value over 99mTc-sestamibi SPECT in imaging CAD.

METHODS

To achieve the study aim, a systematic review of the literature for the 2 tracers were conducted. The aim of the systemic review was to find every related previous study that corresponded to well-defined scientific criteria. The analysis of the results was restricted to peer-reviewed papers in order to avoid any selective outcome reports. Besides, extra analysis was carried out to curb or avoid any ascertainment bias. The qualified studies selected for this research were then assessed for the risk of bias. Furthermore, the details of the methods were rechecked to ensure that they were comparable, before synthesizing the results.

RESULTS

Eighteen original studies were selected and included in the final analysis out of 803 articles identified at the initial research. Overall, the mean value of sensitivity and specificity for diagnosis of CAD was 84.3% and 75.4%, respectively for technetium 99m sestamibi (99mTc-MIBI). On the other hand, for 82-Rubidium-PET, the mean value of sensitivity and specificity for diagnosis of CAD was 81% and 81%, respectively. The accuracy of diagnostics of these imaging modalities was dependent on the radiotracers and stress agent used in these studies, with 99mTc-MIBI achieving the highest diagnostic value.

CONCLUSION

This study concludes that 99mTc-MIBI-SPECT has higher diagnostic value for diagnosing CAD compared to 82-Rubidium-PET. This indicates that 99mTc-MIBI-SPECT is a more valuable technique for predicting CAD. Besides, for the stress agents used to stimulate the heart and increase workload, this research/study recommends the use of adenosine for the SPECT and the use of dipyridamole for positron emission tomography. However, it suggests the need for more systemic and theoretical studies to assess the real value of 82-Rubidium-PET and the value of stress agents.

Diagnostic efficacy of a low-dose 32-projection SPECT 99mTc-sestamibi myocardial perfusion imaging protocol in routine practice

BACKGROUND

99mTc-labeled tracers can provide better imaging quality than does TI for myocardial perfusion imaging (MPI). Nevertheless, a large study showed no significant difference in diagnostic efficacy, implying that image quality, though not optimal, may be still adequate for reliable interpretation. We thus proposed a suboptimal low-dose 32-projection single-photon emission computed tomography (SPECT) 99mTc-sestamibi (99mTc-methoxyisobutylisonitrile) MPI protocol and evaluated its diagnostic efficacy.

METHODS

A total of 1007 patients undergoing the proposed rest-stress MPI protocol were included in the study for analysis. Among them, 218 had coronary angiography, which was used as the 'gold standard' for evaluating sensitivity and specificity. The normalcy rate was obtained from 47 patients with a low cardiovascular risk. The injected dosage for 99mTc-methoxyisobutylisonitrile resting and dipyridamole stress imaging is 185 and 555 MBq, respectively, with an interval of about 2 h between the two injections. Most of the patients completed the whole MPI within 3 h.

RESULTS

Using this protocol, the sensitivity and specificity of the 218 patients with subsequent coronary angiography for determining coronary artery disease were 95 and 63%, respectively. The normalcy rate was 87%. Both the rest and stress images were adequate for confident interpretation.

CONCLUSION

The proposed low-dose 32-projection SPECT protocol has a diagnostic efficacy comparable with that reported in the literature, most of which used a higher dose and 64-projection SPECT, with additional benefits of lower radiation exposure, lower cost, and shorter study time.

Adenosine and adenosine uptake inhibitors potentiate the neuromuscular blocking action of rocuronium mediated by adenosine A(1) receptors in isolated rat diaphragms

BACKGROUND

Adenosine, which pre-junctionally modulates neuromuscular transmission, and adenosine uptake inhibitors, which increase extracellular adenosine, have been used clinically. We investigated the effects of adenosine, dipyridamole and midazolam on the neuromuscular blocking action of rocuronium.

METHODS

Isometric twitch tensions of rat nerve-hemidiaphragm preparations elicited by indirect (phrenic nerve) supra-maximal stimulation at 0.1 Hz were evaluated (n=6 in all data).

RESULTS

Pre-treatments with adenosine (0.1 and 1 microM) and CCPA (1 microM, adenosine A(1) receptor agonist), but not that with CGS21680 (0.5 microM, A(2) receptor agonist), shifted the rocuronium concentration-twitch tension curves to the left and decreased the rocuronium concentration for 50% twitch depression (IC(50)) compared with the control (P<0.01). The leftward shift induced by 1 microM adenosine was inhibited by pre-treatments with theophylline (50 microM, non-selective adenosine receptor antagonist) and DPCPX (0.2 microM, A(1) receptor antagonist) but not by that with DPMA (5 microM, A(2) receptor antagonist). Pre-treatments with dipyridamole and midazolam, adenosine uptake inhibitors, shifted the curve to the left and decreased IC(50) at supra-therapeutic concentrations (10 and 2.5 microM, respectively) but not at clinical concentrations (2 and 0.5 microM, respectively), and the leftward shifts were inhibited by pre-treatment with DPCPX (0.2 microM).

CONCLUSION

The results indicate that adenosine potentiates the neuromuscular blocking action of rocuronium mediated by adenosine A(1) receptors and that supra-therapeutic concentrations of dipyridamole and midazolam also potentiate the action of rocuronium by increasing endogenous adenosine concentration.

A meta-analytic comparison of echocardiographic stressors

BACKGROUND

The relative performance of alternative stressors for stress echocardiography for the diagnosis of coronary artery disease (CAD) is not well established.

METHODS

All studies published between 1981 to December 2001 who met inclusion criteria were included in this analysis. We performed a summary receiver operator characteristic (SROC) analysis and calculated weighted mean of the likelihood ratio and sensitivity/specificity. A covariate analysis using meta-regression methods was also performed.

RESULTS

Forty-four studies presented data on Exercise, 11 on Adenosine, 80 on Dobutamine, 40 on Dipyridamole, 16 on transatrial pacing transesophageal echocardiography (Tap-TEE), and 7 on transatrial pacing transthorasic echocardiography (Tap-TTE). SROC analysis showed that the following order of most discriminatory to least: Tap-TEE, Exercise, Dipyridamole, Dobutamine and Adenosine. Weighted means sensitivity/specificity were Exercise: 82.6/84.4%, Adenosine: 68.4/80.9%, Dobutamine: 79.6/85.1%, Dipyridamole: 71.0/92.2%, Tap-TTE: 90.7/86.1%, and Tap-TEE: 86.2/91.3%. Covariate analysis showed that the discriminatory power of Exercise decreased with increasing mean age.

CONCLUSIONS

Tap-TEE is a very accurate test for both ruling in and ruling out CAD although its invasiveness may limit its clinical acceptability. Exercise is a well-balanced satisfactory test for both ruling in and ruling out but performance might be lower for the elderly. Dobutamine offers a reasonable compromise for Exercise. Dipyridamole might be good for ruling in but not for ruling out CAD. The incapability in ruling-out CAD was a major problem in clinical application of the stress. Adenosine was the least useful stressor in diagnosing CAD.

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.

Use of pharmaceuticals in noninvasive cardiovascular diagnosis

A number of pharmaceuticals are employed as diagnostic agents for cardiovascular diseases. Four groups of agents are reviewed here: 1) vasoactive substances employed as adjuncts to physical maneuvers in diagnosis of structural heart disease; 2) vasodilators used to produce heterogeneity of coronary flow; 3) sympathomimetic agents simulating the effects of exercise on the heart for the purpose of detection of coronary artery stenosis; and 4) ultrasonic contrast agents used to enhance myocardial imaging for the assessment of segmental wall motion. In the first group are amyl nitrate, a vasodilator, and methoxamine and phenylephrine, both vasopressors. The vasodilators of the second group are dipyridamole and adenosine. When combined with scintigraphic perfusion imaging or with echocardiographic assessment of segmental wall motion, these agents can detect single- or multiple-vessel coronary artery disease with sensitivity and specificity comparable to submaximal exercise. They are especially useful for preoperative risk assessment before noncardiac surgery. The sympathomimetic agents of the third group, dobutamine and arbutamine, increase myocardial contractility and heart rate, and dilate the peripheral vasculature. As with the vasodilators, when combined with nuclear or echocardiographic techniques they are equivalent to exercise in detection of coronary disease. They are especially useful in patients with bronchospastic disease and for assessment of myocardial viability. Agents from groups 2 and 3 have acceptable side-effect and safety profiles. The last group reviewed includes echocardiographic contrast agents that, in this investigative setting, are employed to enhance detection of segmental wall motion when used with agents from groups 2 and 3.

Pharmacologic stress testing for coronary disease diagnosis: A meta-analysis

BACKGROUND

Although noninvasive pharmacologic stress tests are widely used, their relative performance is not clear. We compared the performance of pharmacologic stress tests combined with echocardiography or nuclear imaging for the diagnosis of coronary disease.

METHODS

We performed a regression meta-analysis of published data. We included studies published between January 1975 and June 1999 in which subjects underwent echocardiographic or single-photon emission computed tomography (SPECT) stress testing with adenosine, dipyridamole, or dobutamine for diagnosis of coronary artery disease. All subjects also underwent coronary angiography. Two independent reviewers abstracted population characteristics, technical factors, methodologic factors, and results and calculated test sensitivity and specificity.

RESULTS

Eighty-two studies met the inclusion criteria. The sensitivity of dipyridamole SPECT imaging, 89% (95% CI, 84%-93%), was higher than that of dipyridamole echocardiography, but the specificity of dipyridamole SPECT imaging, 65% (95% CI, 54%-74%), was lower than that of dipyridamole echocardiography. Dipyridamole and adenosine tests had similar sensitivities and specificities. The sensitivity of dobutamine echocardiography, 80% (95% CI, 77%-83%) was similar to that of dobutamine SPECT imaging, but dobutamine echocardiography had a higher specificity, 84% (95% CI, 80%-86%) than dobutamine SPECT imaging did.

CONCLUSIONS

The findings of our study can be used to guide the selection of the optimal pharmacologic stress test for each patient. Maximum sensitivity can be attained by use of a vasodilator combined with SPECT imaging. Maximum specificity can be attained by use of a vasodilator with echocardiography. The highest combination of sensitivity and specificity can be attained with dobutamine echocardiography.

Overview of stress echocardiography: uses, advantages, and limitations

Responses of the heart to changes in our environment are probably even more important than how the heart functions at rest. Accordingly, stress testing with noninvasive imaging has become important for diagnosis, prognosis, and monitoring the effects of therapy. Echocardiography at rest and with stress permits characterization of global and segmental left ventricular function as well as valvular structure and function. Moreover, echocardiography can be performed during or after a number of different physical or even mental stressors. Advantages of stress echocardiography include its ready availability, relatively low capital cost, and incremental value in that it allows characterization of cardiac anatomy as well as the myocardial response to a potentially ischemic stimulus. Moreover, echocardiography has the potential to image myocardial perfusion along with wall motion and wall thickening. Substantial literature has now been accumulated on the value of stress echocardiography for the diagnosis of ischemic disease, preoperative risk assessment, and assessment of myocardial viability. Echocardiography has compared generally well with nuclear imaging techniques for the detection of angiographic coronary artery disease. Overall sensitivity, however, has been slightly less, particularly for the detection of single-vessel coronary disease, although specificity has been on average somewhat higher than nuclear cardiology techniques. Because of the potential for variability in study acquisition as well as interpretation, careful safeguards need to be employed. Specifically, meticulous technique needs to be applied to obtain high-quality images and to assure that those images are obtained promptly after treadmill exercise stress. Only readers with specific interest and expertise should interpret stress echocardiography studies. Continuing efforts need to be made to assess and minimize variability and to assure continuing quality improvement. Advances in instrumentation, including evolving technology for real-time 3-dimensional imaging, and echocardiography contrast assessment of myocardial perfusion will likely improve the sensitivity of echocardiography and further extend its usefulness.

Diagnostic and prognostic use of stress echocardiography in stable patients

Stress echocardiography is an effective diagnostic and prognostic technique in stable patients with known or suspected coronary artery disease (CAD), myocardial infarction, or chronic left ventricular dysfunction and those undergoing noncardiac surgery. Stress echocardiography is sensitive and specific for the detection and extent of CAD. Negative tests confer a high negative predictive value for cardiac events regardless of the clinical risk. Positive studies confer a high positive predictive value for ischemic events in patients with intermediate to high clinical risk. Stress echocardiography provides incremental prognostic information relative to clinical, resting echocardiographic, and angiographic data. Meta-analysis studies have shown that the diagnostic and prognostic information provided by stress echocardiography is comparable to that from radionuclide scintigraphic stress tests. Stress echocardiography may be more specific for the detection and extent of CAD, whereas radionuclide scintigraphy may be more sensitive for one-vessel disease. Sensitivities are similar for the detection and extent of disease in patients with multivessel CAD.

Diagnostic and Prognostic Use of Stress Echocardiography and Radionuclide Scintigraphy

Stress echocardiography and radionuclide scintigraphy are effective diagnostic and prognostic techniques in patients with known or suspected coronary artery disease (CAD), myocardial infarction (MI), chronic left ventricular dysfunction (LVD), and those undergoing noncardiac surgery. Both are sensitive and specific for the detection and extent of CAD. Negative tests confer a high negative predictive value for cardiac events irrespective of clinical risk. Positive studies confer a high positive predictive value for ischemic events in patients with intermediate to high clinical risk. Both provide incremental diagnostic and prognostic information relative to clinical, resting echocardiographic, and angiographic data. Meta-analysis studies have shown that the diagnostic and prognostic information provided by stress echocardiography is comparable with radionuclide scintigraphic stress tests. Stress echocardiography may be more specific for the detection and extent of CAD, whereas radionuclide scintigraphy may be more sensitive for single-vessel disease. Sensitivities are similar for the detection and extent of disease in patients with multivessel CAD.

Relation between QT dispersion and adenosine triphosphate stress thallium-201 single-photon emission computed tomographic imaging for detecting myocardial ischemia and scar

It is not known if QT dispersion is useful for detecting coronary artery disease. We investigated whether QT dispersion at baseline and during adenosine triphosphate (ATP) infusion correlate with the imaging patterns obtained from ATP stress thallium-201 single-photon emission computed tomography (ATP-SPECT). QT dispersion was determined in 169 patients who underwent ATP-SPECT from 12-lead electrocardiograms obtained at baseline and 3 minutes after the beginning of ATP infusion. Based on the results of ATP-SPECT, patients were divided into 4 groups: normal (n = 55), ischemia (n = 38), ischemia and scar (n = 42), and scar (n = 34). Baseline QT dispersions (mean +/- SD) in the normal, ischemia, ischemia and scar, and scar groups were 48 +/- 15, 50 +/- 17, 69 +/- 25, and 70 +/- 24 ms, respectively. Baseline QT dispersion was significantly greater in the groups with myocardial scar. QT dispersions during ATP infusion were 43 +/- 16, 63 +/- 20, 76 +/- 20, and 62 +/- 25 ms in the normal, ischemia, ischemia and scar, and scar groups, respectively. QT dispersion increased with ATP infusion in patients with myocardial ischemia. QT dispersion at baseline and during ATP infusion correlated with the ATP-SPECT imaging pattern. These findings suggest that baseline QT dispersion and ATP-induced changes in QT dispersion may help detect the presence of myocardial ischemia and scar.

Assessment of flow mismatch with pharmacologic stress test on myocardial contrast echocardiography in a model of critical stenosis: adenosine triphosphate and dipyridamole

Although adenosine triphosphate (ATP) is a favorable vasodilator because of its short-acting duration, the agent's effectiveness in facilitating the diagnosis of myocardial ischemia with myocardial contrast echocardiography (MCE) is not fully understood. The goal of this study was to examine the efficacy of intravenous ATP administration (0.15 to 0.30 mg/kg/min for 5 minutes) in diagnosing the flow mismatch with MCE. To achieve this, a critical stenosis was produced in the left circumflex artery in 10 anesthetized dogs. The peak intensity ratio of risk area to control area was reduced by ATP from 0.51 +/- 0.19 to 0.31 +/- 0.12 (P <.05). Systolic wall thickening of the risk area did not change significantly (32.8% +/- 9.8% to 27.5% +/- 12.8%). These changes did not differ from those obtained after dipyridamole. We conclude that MCE with intravenous ATP administration is as useful as the dipyridamole method for diagnosing critical coronary stenosis.

Detection of coronary artery disease in patients with severe aortic stenosis with noninvasive methods

Exercise stress ECG testing is not generally recommended in patients with severe aortic stenosis. Analysis of the utility of exercise testing, both with and without the use of myocardial thallium-201 scintigraphy for the diagnosis of coronary artery disease (CAD), yielded low specificity. A noninvasive, safe, and accurate diagnostic modality to ascertain the presence of CAD is not available to date for patients with severe aortic stenosis. The aim of this study was to assess the safety and diagnostic accuracy of adenosine stress echocardiography (A-Stress-Echo) and of adenosine stress myocardial perfusion scintigraphy (A-SPECT), for the detection of CAD in patients with severe aortic stenosis. The study included 50 patients with severe aortic stenosis (maximal instantaneous aortic valve gradient >80 mmHg, range 81 to 144 mmHg, and aortic valve area <0.75 cm2). All patients were submitted to A-Stress-Echo, after a 6-minute infusion of adenosine (140 microg/kg body weight/min), and then (>3 days later) A-SPECT with the same dosage of adenosine as above. Coronary angiography was performed in all patients. No major complications were observed. The unpleasant symptoms were brief and did not necessitate cessation of the test. Both modalities showed the same sensitivity (85% for A-SPECT and 85% for A-Stress-Echo) angiographically diagnosed CAD while A-Stress-Echo yielded much higher specificity (96.7% vs 76.7%). Concordance of the two methods was found in 40 cases and the specificity for those patients was 100%. A-Stress-Echo and A-SPECT, either separately or in combination, constitute excellent and safe noninvasive diagnostic methods in detecting CAD in patients with severe aortic stenosis.

Usefulness of adenosine triphosphate-atropine stress echocardiography for detecting coronary artery stenosis

There have been few studies on adenosine triphosphate (AT) stress echocardiography. The AT stress test may have fewer adverse effects than the adenosine stress test. The addition of atropine to AT echocardiography may enhance the sensitivity for detection of coronary artery disease (CAD). The purpose of this study was to determine the utility of AT-atropine echocardiography for detection of CAD. The group studied consisted of 112 patients with suspected CAD. Sixty-one patients did not have a history of prior myocardial infarction (group I) and 51 patients did (group II). AT was infused intravenously at 180 microg/kg/min for 14 minutes. Atropine (0.25 mg intravenously, repeated up to maximum total dose of 1 mg) was administered starting after 8 minutes of AT infusion. Ischemic response was defined as new or worsening wall motion abnormality occurring during the infusion. The sensitivity and specificity for detection of CAD were assessed using the representative echocardiograms during single AT infusion and AT-atropine infusion. Sixty-two patients had CAD. Fifty-eight patients (52%) developed minor side effects that resolved promptly. The rate-pressure product (10(3)/mm Hg beats/min) was significantly increased at 12 minutes of infusion (12.4+/-3.2) compared with that at baseline (9.1+/-2.3) and that at 6 minutes of infusion (9.4+/-2.1). The sensitivity for detection of CAD was 45% for AT echocardiography and 74% for AT-atropine echocardiography. The specificity was 94% for AT echocardiography and 90% for AT-atropine echocardiography. The sensitivity and specificity of AT-atropine echocardiography was 78% and 93%, respectively, in group I, and 70% and 86%, respectively, in group II. In conclusion, AT-atropine stress echocardiography seems to be well tolerated, safe, and useful for detection of CAD.

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

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

Correlation of adenosine thallium 201 perfusion patterns with markers for inducible ischemia

To determine the frequency of true myocardial ischemia caused by hemodynamic, metabolic, and regional functional abnormalities after intravenous adenosine infusion in patients with coronary artery disease, 13 patients--11 with coronary artery disease--received intravenous adenosine and thallium 201 during cardiac catheterization. Intracoronary adenosine levels increased by an average of 9.4-fold over baseline. Of the 11 patients, all had > or = 70% stenoses with a mean number of redistribution defects per patient of 3.3 +/- 0.7. Only two (18%) patients had new wall motion abnormalities detected by echocardiography during adenosine infusion. Pulmonary capillary wedge pressure did not significantly rise (13 +/- 7 to 17 +/- 8 mm Hg, p= NS). Lactate production occurred in two patients. Coronary sinus oxygen saturation levels rose from 29% +/- 6% to 68% +/- 8%, consistent with less myocardial oxygen extraction. Thus, despite a high prevalence of defects detected by 201Tl, the prevalence of true myocardial ischemia in patients with coronary artery disease undergoing pharmacologic stress imaging with intravenous adenosine is low. Perfusion defects induced by vasodilator stress are predominantly caused by heterogeneity of flow reserve rather than true ischemia.

Supine Bicycle Exercise Echocardiography: A Potent Immediately Available Tool for Detection and Localization of Myocardial Ischemia for the Initial Cardiologist

BACKGROUND: Exercise echocardiography (EE) is being used increasingly as an investigative technique now that dynamic images can be captured digitally. Its equivalent reliability with scintigraphic methods has been demonstrated in a hospital setting. This study analyzes its impact on daily practice. MATERIALS AND METHODS: Standardized progressive stress was produced by supine bicycle ergometry. Echocardiographic images of complete cardiac cycles were obtained in standard apical and parasternal short-axis views before, during, and after maximum effort, and digitized for simultaneous analysis of synchronized images at rest and during exercise. Two hundred sixteen patients (175 men and 41 women; mean age 58 +/- 10 years) were studied. RESULTS: Image quality was suboptimal in 4 cases. In the remaining 212 cases, ischemia was detected in 91 cases, and the test was negative in 114 cases and doubtful in 7 cases. Control by selective coronary angiography, as indicated by the clinical situation, was performed in 52 cases. In this particular group, EE showed 87% sensitivity, which is significantly higher than the 59% recorded for conventional exercise testing (P < 0.0001). CONCLUSIONS: EE by bicycle ergometer in the supine position is a valid, noninvasive investigative technique that can be used in an outpatient situation (feasibility 95%) since it is readily available. Its value appears to be greatest in cases in which exercise ECG is not conclusive. A negative result enables the initial cardiologist to reassure the patient immediately, which has been demonstrated in the literature to have favorable prognostic value. (ECHOCARDIOGRAPHY, Volume 13, May 1996)

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

OBJECTIVES

This study sought to assess the diagnostic efficacy of adenosine technetium-99m sestamibi myocardial perfusion single-photon emission computed tomography (SPECT) in a consecutive series of female patients.

BACKGROUND

The utility of adenosine myocardial perfusion SPECT for the detection of coronary artery disease is not well defined in women because most studies have described a predominantly male population with a high prevalence of coronary artery disease.

METHODS

Of the 201 consecutive female patients in the study group who had undergone adenosine Tc-99m sestamibi myocardial perfusion SPECT, 130 had coronary angiography within 2 months of the nuclear test, and the other 71 had a low likelihood (<10%, mean [+/-SD] 5 +/- 3%) of coronary artery disease. The SPECT protocol used separate acquisition of rest thallium-201 and adenosine Tc-99m sestamibi and was visually analyzed in 20 segments with a semiquantitative five-point scoring system (0=normal; 4=absent uptake).

RESULTS

The normalcy rate in patients with a low likelihood of coronary artery disease was 93% (66 of 71). Among the catheterized group, the overall sensitivity, specificity and predictive accuracy of adenosine sestamibi SPECT for detecting coronary artery disease (> or = to 50% diameter stenosis) were 93% (87 of 94), 78% (28 of 36) and 88% (115 of 130), respectively. In the 103 patients without a prior myocardial infarction, the sensitivity, specificity and predictive accuracy were 91% (61 of 67), 78% (28 of 36) and 86% (89 of 103), respectively, for detecting > or = to 50% diameter stenosis. Of particular interest, the sensitivity and specificity were as high in patients with nonanginal symptoms (93% and 69%, respectively) as in patients with angina (92% and 83%, respectively, p=NS). The sensitivity and specificity among patients with a relatively low (<25%), intermediate (between 25% and 75%) or high prescan likelihood of coronary artery disease (>75%) were similar: 82% and 82%, 93% and 73%, and 95% and 100%, respectively. The sensitivity and specificity for detecting individual diseased vessels (> or = to 50% diameter stenosis) were, respectively, 76% and 81% for the left anterior descending coronary artery, 44% and 90% for the left circumflex coronary artery and 75% and 77% for the right coronary artery.

CONCLUSIONS

Adenosine Tc-99m sestamibi SPECT is an efficient protocol with high sensitivity and specificity for the detection of coronary artery disease in women irrespective of presenting symptoms or pretest likelihood of coronary artery disease and a high normalcy rate. These findings are of particular clinical relevance because chest pain, anginal or otherwise, has been shown to be a frequent but a less specific marker for coronary artery disease among female patients.

Adenosine radionuclide perfusion imaging in the preoperative evaluation of patients undergoing peripheral vascular surgery

To define the clinical and adenosine test variables that predicted perioperative cardiac events, 122 patients who received adenosine radionuclide perfusion imaging before peripheral vascular surgery were reviewed. Events included pulmonary edema, an ischemic end point of acute myocardial infarction (AMI) or cardiac death. Five patients underwent coronary revascularization before the surgical procedure. Of the 117 remaining patients, 19 had pulmonary edema, 10 had an AMI, and 2 died after peripheral vascular surgery. Most of the patients (78%) were in an intermediate-risk group as indicated by the presence of > or = 1 clinical risk factor as defined by the Eagle criteria. The only predictor of perioperative pulmonary edema was a history of congestive heart failure (33% vs 4%; p = 0.002). No clinical variables predicted AMI or death. The adenosine variables that were univariate predictors of AMI and death were the number of reversible perfusion defects (1.75 +/- 1.84 vs 0.75 +/- 0.90; p = 0.001) and the number of coronary artery distributions with a radionuclide perfusion defect (1.33 +/- 0.64 vs 0.85 +/- 0.67; p = 0.022). The number of reversible perfusion defects was the only multivariate predictor of ischemic events (p = 0.017). The presence of > 1 reversible defect was associated with an increased frequency of ischemic events (68% vs 28%; p = 0.045). The sensitivity and specificity of > 1 reversible defect was 58% and 73%, respectively, with a positive and negative predictive value of 19% and 94%.(ABSTRACT TRUNCATED AT 250 WORDS)

Prognostic significance of ST-segment depression during adenosine perfusion imaging

To determine the significance of ST-segment depression during adenosine perfusion imaging for predicting future cardiac events, 188 patients with interpretable electrocardiograms were assessed 1 to 3 years (mean 21.5 +/- 6.6 months) after adenosine testing. At least 1 mm of ST-segment depression was observed in 32 (17%) patients, with > or = 2 mm of ST-segment depression in 10 (5.3%). Thirty-seven cardiac events occurred during the study period: 2 cardiac deaths, 5 nonfatal myocardial infarctions, 6 admissions for unstable angina, and 24 revascularizations. Univariate predictors of events were a history of congestive heart failure, previous non-Q-wave myocardial infarction, previous coronary angioplasty, use of antianginal medication, ST-segment depression during adenosine infusion (particularly > or = 2 mm), any reversible perfusion defect, transient left ventricular cavity dilation, and the severity of perfusion defects. Multivariate analysis identified > or = 2 mm ST-segment depression as the most significant predictor of cardiac events (relative risk [RR] = 6.5; p = 0.0001). Other independent predictors of events were left ventricular dilation (RR = 3.8; p = 0.002), previous coronary angioplasty (RR = 3.3; p = 0.001), a history of non-Q-wave myocardial infarction (RR = 2.3; p = 0.01), and the presence of any reversible defect (RR = 2.0; p = 0.05). We conclude that ST-segment depression occurs uncommonly during adenosine infusion, but the presence of > or = 2 mm of ST-segment depression is an independent predictor of future cardiac events and provides information in addition to that obtained from clinical variables and the results of adenosine perfusion imaging.

Significance of ST segment depression during adenosine-induced coronary hyperemia in angina pectoris and correlation with angiographic, scintigraphic, hemodynamic, and echocardiographic variables

Factors determining myocardial ischemia during adenosine-induced coronary vasodilation in patients with angina pectoris are not well defined. To evaluate the angiographic, scintigraphic, hemodynamic, and echocardiographic determinants of ST segment depression during adenosine infusion, 40 patients with angina pectoris underwent technetium-99m sestamibi single photon emission computed tomography and simultaneous two-dimensional echocardiography. Ischemic ST depression occurred in 18 patients (45%). Coronary angiography was performed in all patients and a coronary artery jeopardy score was determined. The sensitivity, specificity, and the predictive accuracy of adenosine-induced ST segment depression in detecting significant coronary artery disease were 53%, 100%, and 60%, respectively, while the corresponding results for detecting reversible perfusion defects were 61%, 92%, and 70%, respectively. Univariate predictors of ST segment depression included the coronary artery jeopardy score, the presence and the extent of reversible perfusion defects, the presence of three-vessel and/or left main coronary artery disease, and diastolic blood pressure at peak adenosine infusion. There was a trend (P = 0.06) to a higher incidence of collateral vessels in patients developing ST segment depression. The coronary artery jeopardy score was found to be the only significant independent predictor of ST segment depression by stepwise multivariate logistic regression analysis. Thus, in patients with angina pectoris, the coronary artery jeopardy score, representing the extent of significant coronary artery disease, is the most important independent predictor of adenosine-induced ST segment depression. ST depression is unusual in the absence of reversible perfusion defects and is also associated with more extensive reversible defects.

Noninvasive testing in the diagnosis and management of unstable angina

Patients presenting with a clinical diagnosis of unstable angina comprise a heterogenous population and a wide spectrum of patients with varying degrees of underlying coronary artery disease, severity and prognosis are categorized in this syndrome. A very small number of patients with unstable angina who are refractory to adequate in-hospital medical therapy should undergo urgent coronary angiography and, if suitable, revascularization. The vast majority of patients do, however, stabilize on medical therapy and an invasive approach, such as a coronary angiography should not be performed routinely to all of these patients. Early recognition of clinical and non-invasive test variables indicating an adverse outcome is of paramount importance in unstable angina. This review focuses on the importance of baseline clinical markers and the usefulness of a non-invasive approach with exercise testing, myocardial perfusion imaging, stress echocardiography, and Holter monitoring in the diagnosis, risk stratification, and management of patients with unstable angina.