Selective correlation of amide groups to glycine alpha protons and of arginine guanidine groups to delta protons in proteins by multiple quantum spectroscopy

Study objective: We sought to determine whether electron-beam computed tomography (EBCT) could be used as a triage tool in the emergency department for patients with angina-like chest pain, no known history of coronary disease, normal or indeterminate ECG findings, and normal initial cardiac enzyme concentrations. METHODS: We conducted a prospective observational study of 105 patients admitted between December 1995 and October 1997 to the ED of a large tertiary care hospital with 70,000 annual ED visits. The study group was comprised of women aged 40 to 65 years and men aged 30 to 55 years who presented with angina-like chest pain requiring admission to the hospital or chest pain observation unit. All patients underwent EBCT of the coronary arteries, along with other cardiac testing as deemed necessary by staff physicians. RESULTS: Of the 105 patients, 100 underwent other cardiac testing during hospitalization. Evaluation included treadmill exercise testing in 58, coronary angiography in 25, radionuclide stress testing in 19, and echocardiography in 11. Results of EBCT and cardiac testing were negative for both in 53 patients (53%), positive for both in 14 (14%), positive for tomography and negative for cardiac testing in 32 (32%), and negative for tomography and positive for cardiac testing in only 1 patient. This positive test result, on a treadmill exercise test, was ruled a false positive by an independent staff cardiologist. Two other female patients with normal exercise sestamibi or coronary angiography and EBCT findings also had false-positive treadmill exercise results. The sensitivity of EBCT was 100% (95% confidence interval, 77% to 100%), with a negative predictive value of 100% (95% confidence interval, 94% to 100%). Specificity was 63% (95% confidence interval, 54% to 75%). CONCLUSION: EBCT is a rapid and efficient screening tool for patients admitted to the ED with angina-like chest pain, normal cardiac enzyme concentrations, indeterminate ECG findings, and no history of coronary artery disease. Our study suggests that patients with normal initial cardiac enzyme concentrations, normal or indeterminate ECG findings, and negative results on EBCT may be safely discharged from the ED without further testing or observation. Larger studies are required to confirm this conclusion.     

Exercise-induced ST segment change and coronary risk factors in apparently healthy men

Exercise stress test is useful for the early detection of coronary artery disease and is recommended as a medical clearance test before the initiation of exercise training. However, when applied to apparently healthy people, there are many false positive results. It is therefore necessary to determine indications for stress testing, but few data are available in Japan. In this study, we performed exercise stress test in apparently healthy men to investigate the incidence of exercise-induced ST segment changes and their relationship to coronary risk factors. The subjects were 2,187 men who underwent symptom-limited exercise stress test at a health-promotion center in Tokyo. Those with a history of cardiovascular disease were excluded. They underwent symptom-limited exercise stress test on a treadmill with a modified Bruce protocol or on a cycle ergometer with a ramp protocol (20 watts per minute). Twelve-lead electrocardiogram was recorded every 3 min. Cardiologists evaluated the exercise ECG responses, and advised those with abnormal ST segment changes (Group A) to undergo further examinations at a cardiovascular hospital. The results of further examination such as exercise scintigraphy and/or coronary angiography were obtained. Twice the number of subjects with normal exercise responses were selected as age-matched controls (Group N) to compare the coronary risk factors between the two groups. Twenty-nine subjects had abnormal ST segment changes (1.33% of the total subjects) (Group A). Their mean age was 57 years (38 to 76). Among these, 27 had ST segment depression and 2 had ST elevation.(ABSTRACT TRUNCATED AT 250 WORDS)     

Ontogeny of thyroid hormone receptors in the brushtail possum (Trichosurus vulpecula)

Exercise electrocardiogram (ECG) has a high rate of false negative results in comparison with simultaneously performed thallium-201 perfusion scintigraphy, particularly in patients with single-vessel coronary artery disease, low exercise workload, inadequate heart rate rise, and resting ECG abnormalities. We present the case of a patient in whom thallium-201 SPECT scintigram revealed equally extensive and severe myocardial ischemia in two myocardial planes opposite each other. The accompanying exercise ECG did not disclose ischemic changes despite the adequacy of heart rate rise in this patient with severe right and left anterior descending coronary artery disease. We propose, as an explanation for this phenomenon, that in this patient the ischemic ST-segment vectors of equal magnitude and direction but of opposite sense, generated during stress, cancelled each other ("ischemic ST-segment counterpoise"), thus rendering the exercise ECG normal.     

QRS prolongation measured by a new computerized method: a sensitive marker for detecting exercise-induced ischemia

This study compared thallium stress testing and exercise changes in QRS duration using a computerized 'optic scanner' in three groups. Group 1 consisted of 108 subjects with positive exercise ECG tests by ST-T segment criteria and with proven coronary artery disease. Group 2 included 19 subjects with nondiagnostic exercise ECG ST-T changes and with proven coronary artery disease. Group 3 was formed by 38 healthy controls. Group 1: Mean increase in exercise QRS width of 12.4 +/- 14 ms. Group 3: Mean decrease in exercise QRS width of 4.9 +/- 9.3 ms (p < 0.0001). Group 2: Mean QRS prolongation of 7.8 +/- 9.2 ms, which was significantly different from the controls (p < 0.0001) but not from group 1. When compared to thallium stress testing, exercise QRS prolongation had a sensitivity of 93%, specificity of 71%, relative risk of 5, and positive predictive value of 86%. QRS duration measurement can improve the diagnostic accuracy of the exercise ECG stress test.     

Accuracy of treadmill exercise electrocardiography in detecting restenosis following single-vessel percutaneous transluminal coronary angioplasty

To develop an improved method for diagnosing restenosis using treadmill exercise electrocardiography (ECG) following percutaneous transluminal coronary angioplasty (PTCA), we prospectively evaluated 46 patients who underwent PTCA for the treatment of single-vessel coronary artery disease and who did not have a history of myocardial infarction. Treadmill exercise ECG and coronary angiography were performed 3 months after PTCA to determine their accuracy in diagnosing restenosis based on standard ST-segment depression criteria, the difference between the maximum ST-segment depression before and 3 months after PTCA (< or =0.5 mm: positive; >0.5 mm: negative), and the difference between sigmaST-segment depression before PTCA and 3 months after PTCA (< or = 1.5 mm: positive; > 1.5 mm: negative). The sensitivity, specificity, and diagnostic accuracy of standard ST-segment depression criteria were 65%, 66%, and 65%, respectively. The sensitivity, specificity, and accuracy for the difference in maximum ST-segment depression were 77%, 76%, and 76%, respectively, whereas the values for the difference in sigmaST-segment depression were 77%, 83%, and 80%, respectively. Based on these results, we conclude that using the difference between ST-segment depression before and after PTCA improves the accuracy of treadmill exercise ECG for diagnosing restenosis.     

The sensitivity and specificity of the ergometric test for the diagnosis of coronary disease

According to the principles of probabilistic analysis, sensitivity and specificity of a diagnostic test are fixed values. Nevertheless, most authors consider them to be inconstant values, specially when applied to the diagnosis of coronary heart disease by exercise stress test. In this paper, we review the basic concepts on sensitivity and specificity of diagnostic tests and try to explain their supposed variability, when related to exercise test, as a function of undue comparison between ST-segment response and the findings of cinecoronariography. Based on the essential difference between coronary heart disease and ischemic heart disease, we demonstrate why such an equivocal comparison can lead to false results of sensitivity and specificity of exercise tests relative to coronary heart disease. As a result, their alleged variability depends most on the prevalence of ischemia throughout the spectrum of coronary heart disease in the studied population. As a matter of fact, unless one can rely on a method as a gold standard for the diagnosis of ischemic heart disease, the real sensitivity and specificity of exercise stress test should be considered as unknown values.     

Improved detection of coronary artery disease by exercise electrocardiography with the use of right precordial leads

BACKGROUND: Exercise electrocardiography is an perfect test for the detection of coronary artery disease. We attempted to improve the diagnostic accuracy of exercise testing as a noninvasive method for the detection of coronary artery disease by using a combination of the left and right precordial leads. METHODS: We studied 245 patients (218 men and 27 women) ranging from 32 to 74 years of age (mean [+/-SD], 52+/-8) who underwent treadmill exercise testing, thallium-201 scintigraphy, and coronary arteriography. During exercise testing, each patient had one electrocardiogram recorded with the standard 12 leads and 3 right precordial leads (V3R, V4R, and V5R), with the results for each set of leads recorded and analyzed separately. RESULTS: On the basis of coronary arteriography, 34 patients had normal coronary arteries, 85 had single-vessel disease, 84 had two-vessel disease, and 42 had three-vessel disease. The sensitivities of the standard 12-lead exercise electrocardiogram, exercise electrocardiography incorporating right precordial leads, and thallium-201 scintigraphy were 52 percent, 89 percent, and 87 percent, respectively, for the detection of single-vessel disease; 71 percent, 94 percent, and 96 percent for the detection of two-vessel disease; 83 percent, 95 percent, and 98 percent for the detection of three-vessel disease; and 66 percent, 92 percent, and 93 percent for the detection of any coronary artery disease. The specificities of the three methods for the detection of any coronary artery disease were 88 percent, 88 percent, and 82 percent, respectively. CONCLUSIONS: Use of right precordial leads along with the standard six left precordial leads during exercise electrocardiography greatly improves the sensitivity of exercise testing for the diagnosis of coronary artery disease.     

Dipyridamole and dobutamine-atropine stress echocardiography in the diagnosis of coronary artery disease. Comparison with exercise stress test, analysis of agreement, and impact of antianginal treatment

STUDY OBJECTIVES: To compare the usefulness of dipyridamole echocardiography, dobutamine-atropine echocardiography, and exercise stress testing in the diagnosis of coronary artery disease and to analyze the agreement among the tests. DESIGN: Performance of these three tests in random order on a consecutive cohort of patients. SETTING: A tertiary care and university center. PATIENTS: One hundred two consecutive patients with chest pain and no history of coronary artery disease. INTERVENTIONS: Dipyridamole echocardiography, dobutamine-atropine echocardiography, exercise stress testing, and coronary angiography. MEASUREMENTS AND RESULTS: Dobutamine-atropine test was positive in 49 (77%) of 63 patients with coronary artery disease, dipyridamole test in 49 (77%), and exercise stress test in 44 (68%; p = NS). Both echocardiographic tests showed an overall specificity (dipyridamole, 97%; dobutamine, 95%) higher than exercise stress test (79%; p < 0.05). Sensitivity of dipyridamole testing decreased from 93 to 61% (p = 0.002) if patients were receiving antianginal treatment but sensitivity of dobutamine-atropine testing was not affected (77% in patients receiving and not receiving treatment). When results were considered as positive-negative, agreement between dipyridamole and dobutamine-atropine echocardiography was 85% (kappa = 0.70). With regards to regional analysis, concordance was good (93% for segments, kappa = 0.76; and 95% for coronary arteries, kappa = 0.92). Major complications were more frequent during dobutamine-atropine (n = 7) than during dipyridamole infusion (n = 2) (p = 0.06). CONCLUSIONS: Dobutamine-atropine and dipyridamole echocardiography have a similar sensitivity and a higher specificity than that obtained by exercise ECG for the diagnosis of coronary artery disease. Similar information is obtained with dipyridamole and dobutamine-atropine echocardiography. It is our thought that pharmacologic stress echocardiography should be used as a first-step test to rule out coronary artery disease in patients not capable of exercising.     

Comparison of dobutamine stress echocardiography and treadmill exercise electrocardiography for detection of coronary artery disease

BACKGROUND: Critical analysis of treadmill exercise testing (TMET) for the detection of coronary artery disease has revealed many shortcomings. Excellent diagnostic accuracy has been reported for dobutamine stress echocardiography (DSE). METHODS: A prospective comparison of DSE and TMET for the detection of coronary artery disease in routine clinical practice was performed using contrast cineangiography (significant stenosis > or = 50%) as a gold standard. RESULTS: A total of 116 patients (82 men, 34 women) were studied. Significant stenosis was detected by coronary angiography in 92 patients (79%). Single vessel disease occurred in 28, double-vessel disease in 32, and multivessel disease in 32 patients. Although sensitivity of DSE was better than that of TMET (82 versus 40%), specificity was worse (63 versus 79%). Positive predictive values for both DSE and TMET were good at 89 and 87%, respectively, whereas negative predictive values were poor for both (47% for DSE, 26% for TMET). CONCLUSIONS: Overall, DSE performs better than TMET in terms of sensitivity and positive and negative predictive value. Its lower specificity than that of TMET may lead to more patients being referred for diagnostic coronary angiography. The poor negative predictive value of DSE and TMET means that one should not be falsely reassured by normal results.     

N-alpha-tosyl-L-lysine chloromethylketone prevents expression of iNOS in vascular smooth muscle by blocking activation of NF-kappa B

OBJECTIVE: To demonstrate that an agreement approach to applying equations on the basis of clinical and exercise test variables is an accurate, self-calibrating, and cost-efficient method for predicting severe coronary artery disease in clinical populations. DESIGN: Retrospective analysis of consecutive patients with complete data from exercise testing and coronary angiography referred for evaluation of possible coronary artery disease. After developing an equation in a training set, this equation and two other equations developed by other investigators were validated in a test set. The study was performed at two university-affiliated Veteran's Affairs medical centers. PATIENTS: 1080 consecutive men studied between 1985 and 1995 who had coronary angiography within 3 months of the treadmill test. The population was randomly divided into a training set of 701 patients and a test set of 379 patients. Patients with previous coronary artery bypass surgery, valvular heart disease, marked degrees of resting ST depression, and left bundle branch block were excluded. MEASUREMENTS: Recording of clinical and exercise test data along with visual interpretation of the electrocardiogram recordings on standardized forms and abstraction of visually interpreted angiographic data from clinical catheterization reports. RESULTS: Simple clinical and exercise test variables improved the standard application of exercise-induced ST criteria for predicting severe coronary artery disease. By setting probability thresholds for severe disease of <20% and >40% for the three prediction equations, the agreement approach divided the test set into three groups: low risk (patients with all three equations predicting <21% probability of severe coronary disease), no agreement, and high risk (all three equations with >39% probability) for severe coronary artery disease. Because the patients in the no agreement group would be sent for further testing and would eventually be correctly classified, the sensitivity of the agreement approach was 89% and the specificity was 96%. The agreement approach appeared to be unaffected by disease prevalence, missing data, variable definitions, or even angiographic criteria. CONCLUSIONS: Requiring diagnosis of severe coronary disease to be dependent on agreement between these three equations has made them likely to function in all clinical populations. The agreement approach should be an efficient method for the evaluation of populations with varying prevalence of coronary artery disease, limiting the use of more expensive noninvasive and invasive testing to patients with a higher probability of left main or triple-vessel coronary artery disease. This approach provides a strategy that can be applied by inputting the results of basic clinical assessment into a programmable calculator or a computer to assist the practitioner in deciding when further evaluation is appropriate, thus assuring patients access to subspecialty care.     

Diagnostic value of myocardial thallium stress scintigraphy in the detection of coronary artery disease in patients undergoing chronic hemodialysis

Atherosclerotic heart disease is the leading cause of death in patients with end stage renal disease, but its non invasive detection remains difficult because of a low efficacy of exercise testing. The aim of the study was to evaluate diagnostic accuracy of thallium myocardial imaging after dipyridamole combined with exercise. Forty two chronic dialysis patients (34 men, 8 women) aged 55 +/- 11 years (range: 36 to 75) without symptom of angina nor myocardial infarction were studied. In each patient, an echocardiography, a myocardial scintigraphy with dipyridamole combined with symptom-limited exercise, and coronarography were performed. A coronary heart disease was diagnosed by coronarography in 10 patients (4.5 and 1 respectively with 1, 2 and 3 vessels diseased). Echocardiography detected a left ventricular hypertrophy (LVH) in 26 patients and a regional asynergia in 14 patients. A positive scintigraphy was present in 11 patients. Three false-positive and 2 false-negative on scintigraphy were noted. Sensibility, specificity, positive predictive value and negative predictive value were respectively evaluated at 80, 73, 73 and 93%. All the five patients with either false-positive or false-negative scintigraphy exhibited a LVH. CONCLUSION. In chronic dialysis patients, coronary heart disease may be detected by thallium myocardial imaging after dipyridamole combined with exercise.     

Comparison of four methods for the detection of fecal streptococci in water

The objective of this study was to select an effective and fast method for the detection of socalled fecal streptococci in water by comparing a method according to the German drinking water standard, a membrane filtration method according to the ISO-draft standard 7899/2, the Chromocult Enterococcus Broth (Merck) and the Enterolert-System (IDEXX). The study was based on a collective of 297 water samples derived from different stages of water treatment and distribution, as well as from individual water supplies. The sensitivity, reliability, and selectivity of the single methods in relation to their practicability was evaluated. Concerning false positive and false negative results, the tests were proved by metabolic characterization of the isolated strains. The advantages and disadvantages of the methods resulting from the investigated criteria are discussed. The work is part of a comparative study within the scope of the DIN ad-hoc-committee "fecal streptococci".     

Value of QT dispersion in the interpretation of exercise stress test in women

BACKGROUND: Exercise testing in women is associated with a high incidence of false-positive ECG changes and should be combined with an imaging study. The QT dispersion (QTD), recorded as the difference between maximum and minimum QT intervals on a 12-lead ECG, is sensitive to myocardial ischemia and may improve the accuracy of exercise testing in women. METHODS AND RESULTS: Exercise ECGs were analyzed in 64 women who had undergone exercise ECG and coronary angiography for clinical indications: 20 patients with normal exercise stress test and nonsignificant (< or = 50% diameter narrowing of a major epicardial coronary artery) coronary artery disease (CAD) on angiography (true-negative; TN group), 20 patients with positive exercise stress tests (> or = 1 mm ST-segment depression or reversible perfusion defects) and significant CAD (true-positive; TP group), and 24 patients with positive exercise stress tests but no significant CAD (false-positive; FP group). The exercise QTD was 45+/-15 ms in TN, 80+/-23 ms in TP (P<.0001 versus TP), and 41+/-14 ms in FP (P=NS versus TN and <.0001 versus TP) groups. A stress QTD of > 60 ms had a sensitivity of 70% and specificity of 95% for the diagnosis of significant CAD compared with 55% (P<.05) and 63% (P<.01), respectively, for > or = 1 mm ST-segment depression during stress. When QTD of > 60 ms was added to ST-segment depression as a condition for positive test, the specificity increased to 100%. CONCLUSIONS: Exercise QTD is an easily measurable ECG variable that significantly increases the accuracy of exercise testing in women.     

Postexercise systolic blood pressure response: clinical application to the assessment of ischemic heart disease

Stress test parameters indicating the presence and extent of coronary artery disease have traditionally included such variables as exercise duration, and the blood pressure and ST-segment responses to exercise. The three-minute systolic blood pressure ratio, another important indicator of significant coronary artery disease, is a useful and readily obtainable measure that can be applied in all patients who are undergoing stress testing for the evaluation of known or suspected ischemic heart disease. The ratio is calculated by dividing the systolic blood pressure three minutes into the recovery phase of a treadmill exercise test by the systolic blood pressure at peak exercise. A three-minute systolic blood pressure ratio greater than 0.90 is considered abnormal and has a diagnostic accuracy of approximately 75 percent for the detection of coronary artery disease (i.e., an accuracy comparable to that of ST-segment depression). Higher values for the ratio are associated with more extensive coronary artery disease, as well as an adverse prognosis after myocardial infarction. Thus, the three-minute systolic blood pressure ratio provides information that is complementary to the traditional exercise test parameters for identifying high-risk ischemic heart disease.     

Exercise in an hypoxic environment as a screening test for ischaemic heart disease

Submaximal and maximal exercise testing have been used to predict coronary events but these tests do not give reliable information regarding employability of subjects with abnormal electrocardiogram. In 30 subjects with stabilized ischaemic heart disease (Group A) and 70 subjects with abnormal resting electrocardiogram (Group B), resting electrocardiograms--at ground level and at a simulated height of 4592 m (15000 ft)--after 40-min exposures were recorded. The double Master's two-step exercise test (DM) was performed at ground level as well as at stimulated height (DMH). In the ischaemic group, exercise combined with hypoxia did not yield better results than exercise alone; but among the asymptomatic subjects, exercise in an hypoxic environment gave significantly better results than exercise alone (p less than 0.005) or hypoxia alone (p less than 0.01). Those with negative responses to the test have been employed on strenous duties, including employment at high altitude for the last 3 years. None of them have manifested any objective or subjective evidence of ischaemic heart disease. DM exercise testing in an hypoxic environment is a reliable method to assess subjects with abnormal electrocardiogram and evaluate their functional status.     

Clinical symptomatology of coronary artery disease and results of exercise thallium scintigraphy: gender-related differences

Exercise thallium stress test is the mainstay of the noninvasive assessment of patients with symptomatology suggestive of coronary artery disease. The diagnostic accuracy of thallium scintigraphy as a screening test for coronary artery disease in women as compared to men, however, remains controversial. In order to determine whether gender-related differences in the detection of coronary artery disease using exercise thallium scintigraphy are demonstrable in all age groups, we analyzed the exercise thallium results in 335 outpatients (189 male, 146 female), who were referred by their primary physicians to our institution for evaluation of clinically suspected coronary artery disease. Overall, 50.3 percent of men had a positive for ischemia thallium stress test vs 29.5 percent of women (p < 0.0002). In the subgroup of patients 65 years of age or above, 67.4 percent of men had a positive for ischemia thallium stress test vs 27.6 percent of women (p < 0.003). In the subgroup of patients upto 40 years of age, 37.9 percent of men had a positive for ischemia thallium stress test vs 25.0 percent of women (p = NS). We conclude that symptoms suggestive of coronary artery disease are less predictive of positive exercise thallium stress tests in women as compared to men even above age 65 when the prevalence of coronary artery disease is known to be similar. This suggests that women may have lower threshold for perception of symptoms or that physicians have lower threshold for referring women for screening of coronary artery disease.     

Coronary calcification by electron beam computed tomography and obstructive coronary artery disease: a model for costs and effectiveness of diagnosis as compared with conventional cardiac testing methods

OBJECTIVES: The purpose of this study was to determine if electron beam computed tomography (EBCT) has potential as a cost-effective approach to diagnosis of obstructive coronary disease. BACKGROUND: Coronary calcification quantified by EBCT is closely related to the extent of atherosclerosis. METHODS: A model based upon published sensitivities (Se)/specificities (Sp) for diagnosis in an ambulatory patient of obstructive coronary disease (> or =50% stenosis) and population prevalence was tested for angiography alone, or treadmill exercise, stress echocardiography, stress thallium or predetermined EBCT calcium score outpoints, followed by angiography if indicated. RESULTS: Total direct testing costs increased in proportion to disease prevalence whereas cost-effectiveness, direct costs/patient diagnosed correctly with disease, decreased as a function of prevalence. Using an EBCT calcium score of 168 (Se/Sp = 71%/90%) provided for the least costly and most cost-effective noninvasive pathway. Calcium scores of 80 (Se/Sp = 84%/84%) and 37 (Se/Sp = 90%/77%) were also cost-effective when prevalence of disease was < or =70%; but results for a >0 calcium score (Se/Sp = 95%/46%) cutpoint were not superior to conventional methods. Calcium score cutpoints of 37, 80 or 168 provided similar or superior overall negative and positive predictive values to conventional noninvasive testing pathways across all prevalence subgroups. CONCLUSIONS: In ambulatory patients evaluated for obstructive coronary disease, a testing pathway utilizing quantification of coronary calcium by EBCT as an initial noninvasive testing approach minimized direct costs, and maximized cost-effectiveness in population groups with low/ moderate disease prevalence (< or =70%); as expected, direct angiography as the first and only test proved most cost-effective in patients with a high prevalence (>70%) of disease.     

Noninvasive myocardial imaging with potassium-43 and rubidium-81 in patients with left bundle branch block

Noninvasive myocardial imaging with potassium-43 and rubidium-81 has been used successfully to identify areas of infarction and exercise-induced ischemia as regions of decreased radioactivity. The image defects observed are believed to be due to a decreased radionuclide uptake in regions of myocardial scar or to heterogeneous myocardial accumulation of tracer as a result of regional ischemia. Of 27 patients with left bundle branch block studied with noninvasive imaging at rest and during exercise, 25 manifested at rest reduced radioactivity in the region of the interventricular septum. This pattern is similar to that seen in patients with anteroseptal myocardial infarction. Sixteen of the 27 patients underwent diagnostic coronary arteriography and left ventriculography. Only five of these patients had evidence of either previous infarction or significant obstructive coronary artery disease as assessed with clinical or angiographic criteria, or both. Although the image defect was routinely demonstrated at rest in patients with left bundle branch block, this defect was generally normalized or less distinct with exercise in patients with no anatomic heart disease. In contrast, a larger, more distinct or new image defect with exercise correctly identified the presence of significant obstructive coronary artery disease in patients with left bundle branch block. In the clinical application of noninvasive myocardial imaging, these image defects observed at rest can lead to the false pasitive radionuclide interpretation of anteroseptal myocardial infarction.     

Exercise echocardiography or exercise SPECT imaging? A meta-analysis of diagnostic test performance

CONTEXT: Cardiac imaging has advanced rapidly, providing clinicians with several choices for evaluating patients with suspected coronary artery disease, but few studies compare modalities directly. OBJECTIVES: To review the contemporary literature and to compare the diagnostic performance of exercise echocardiography (ECHO) and exercise single-photon emission computed tomography (SPECT) imaging in the diagnosis of coronary artery disease. DATA SOURCES: Studies published between January 1990 and October 1997 identified from MEDLINE search; bibliographies of reviews and original articles; and suggestions from experts in each area. STUDY SELECTION: Articles were included if they discussed exercise ECHO and/or exercise SPECT imaging with thallous chloride TI 201 (thallium) or technetium Tc 99m sestamibi for detection and/or evaluation of coronary artery disease, if data on coronary angiography were presented as the reference test, and if the absolute numbers of true-positive, false-negative, true-negative, and false-positive observations were available or derivable from the data presented. Studies performed exclusively in patients after myocardial infarction, after percutaneous transluminal coronary angioplasty, after coronary artery bypass grafting, or with recent unstable coronary syndromes were excluded. DATA EXTRACTION: Clinical variables, technical factors, and test performance were independently extracted by 2 reviewers on a standardized spreadsheet. Discrepancies were resolved by consensus. RESULTS: Forty-four articles met inclusion criteria. In pooled data weighted by the sample size of each study, exercise ECHO had a sensitivity of 85% (95% confidence interval [CI], 83%-87%) with a specificity of 77% (95% CI, 74%-80%). Exercise SPECT yielded a similar sensitivity of 87% (95% CI, 86%-88%) but a lower specificity of 64% (95% CI, 60%-68%). In a summary receiver operating characteristic model comparing exercise ECHO performance to exercise SPECT, exercise ECHO was associated with significantly better discriminatory power (parameter estimate, 1.18; 95% CI, 0.71-1.65), when adjusted for age, publication year, and a setting including known coronary artery disease for SPECT studies. In models comparing the discriminatory abilities of exercise ECHO and exercise SPECT vs exercise testing without imaging, both ECHO and SPECT performed significantly better than exercise testing. The incremental improvement in performance was greater for ECHO (3.43; 95% CI, 2.74-4.11) than for SPECT (1.49; 95% CI, 0.91-2.08). CONCLUSIONS: Exercise ECHO and exercise SPECT have similar sensitivities for the detection of coronary artery disease, but exercise ECHO has better specificity and, therefore, higher overall discriminatory capabilities as used in contemporary practice.     

Cardiac stress testing with thallium-201 imaging reveals silent ischemia in individuals with paraplegia

The purpose of this study was to determine through noninvasive arm ergometry and radionuclide tomographic imaging the presence of latent coronary heart disease (CHD) in subjects with paraplegia. Assessment of CHD in spinal cord injury, using these methods, has not been addressed previously. Twenty asymptomatic subjects with paraplegia performed arm ergometry exercise stress testing with thallium-201 single photon emission computerized tomography (SPECT) or planar myocardial imaging studies. All subjects had normal resting electrocardiograms (ECG). Only five subjects had ECG evidence of ischemia on exercise testing, whereas 13 subjects, including the five subjects with ECG positive stress tests, had scintigraphic evidence of ischemia. Thus, eight subjects would have been undiagnosed for CHD without thallium-201 SPECT imaging. These individuals had multiple risk factors for CHD and, except for age, were without a statistically significant difference between the groups with positive or negative thallium stress imaging studies. Arm ergometry stress thallium imaging shows a high prevalence of ischemia in subjects with paraplegia.