Noninvasive prediction of the angiographic extent of coronary artery disease after myocardial infarction: comparison of clinical, bicycle exercise electrocardiographic, and ventriculographic parameters

Management of Tricuspid Valve Disease in Patients Undergoing Double Valve Replacement

The management of mild tricuspid valve disease associated with left-sided valve lesions remains controversial. Between January 1985 and September 1995, 87 patients underwent combined double (aortic and mitral) valve replacement and tricuspid valve repair at the Shanghai Chest Hospital. The early mortality was 16.1%. Predictors of early mortality were found to be New York Heart Association functional class IV and right ventricular systolic pressure of 65 mm Hg or more, by multivariable regression analysis. The mean follow-up was 4.6 years. Cumulative 3-year and 5-year survival rates in patients discharged from hospital were 80% ± 4% and 63% ± 7%. Late mortality was due to sudden death (18.7%), myocardial infarction (6.5%), and cerebral embolism or hemorrhage (31.2%). Of 48 patients still alive, 45 are in New York Heart Association functional class I or II. None of them has mild or moderate tricuspid regurgitation. Based on these results, we recommend early surgical treatment prior to the appearance of severe hemodynamic deterioration and we propose a policy of liberal indication for tricuspid annuloplasty for mild functional tricuspid insufficiency at the initial double valve replacement.

Risk stratification of patients with coronary artery disease and left ventricular dysfunction by exercise radionuclide angiography and exercise electrocardiography

BACKGROUND

The results of multicenter trials indicate that patients with left ventricular dysfunction and either three-vessel or left main coronary artery disease have improved prognosis when treated surgically.

OBJECTIVE

As part of a larger evaluation and follow-up study of coronary artery disease, the objective of this investigation was to determine whether exercise radionuclide angiography can be used, in patients with mild symptoms of coronary artery disease and left ventricular dysfunction at rest, to identify patients with three-vessel or left main coronary artery disease.

METHODS AND RESULTS

Eighty-four consecutive patients were studied with angiographically defined coronary artery disease in whom left ventricular ejection fraction at rest ranged from 20% to 40%. Patients underwent exercise electrocardiography, rest and exercise radionuclide angiography, and 24-hour electrocardiographic monitoring. There were 22 patients with one-vessel, 31 with two-vessel, 27 with three-vessel, and four with left main coronary artery disease. All but four patients had a documented history of myocardial infarction. By univariate analysis, the following parameters were related to the anatomic severity of coronary artery disease: magnitude of ST segment depression with exercise (p < 0.001), magnitude of change in ejection fraction with exercise (p < 0.005), and occurrence of angina during exercise (p < 0.005). However, because of the extensive overlap among anatomic subgroups, no single factor had both a satisfactory sensitivity and a satisfactory specificity in identifying patients with three-vessel and left main coronary artery disease. Multivariate stepwise regression analysis also failed to predict three-vessel or left main coronary artery disease satisfactorily (sensitivity 73% and specificity 73%; positive predictive accuracy 59% and negative predictive accuracy 83%). Nonetheless, this multivariate analysis provided important prognostic information. During medical therapy (mean follow-up 56 months), the patients with a high likelihood of three-vessel or left main coronary artery disease had a greater risk of death or reinfarction than had patients with a low likelihood (p < 0.05). These functional data were better than coronary anatomy alone in providing risk stratification. Four of six patients with two-vessel disease who died were classified incorrectly by the multivariate analysis in the high-likelihood group for three-vessel or left main coronary artery disease, but classified correctly as being at high risk; whereas none of the patients with three-vessel disease who were misclassified in the low-likelihood group died during medical therapy.

CONCLUSION

Although exercise radionuclide angiography in patients with minimal symptoms of coronary artery disease and left ventricular dysfunction is not precise in predicting three-vessel or left main coronary artery disease, it provides important functional information regarding subsequent prognosis during medical therapy.

Noninvasive testing of asymptomatic patients for the detection of silent ischemia after an infarction. A decision analysis

This decision analysis estimates the overall gain in life expectancy and the relative efficacy of predischarge submaximal exercise electrocardiography, ambulatory cardiac monitoring, and thallium-201 scintigraphy for the identification of silent ischemia in asymptomatic postinfarct patients. A small, virtually equal increase in life expectancy can be obtained from any of the noninvasive tests (as compared to no testing). Large differences in life expectancy may result only when the prevalence of residual coronary artery disease and the probability of left-main and three-vessel lesions are high.

Relation between left ventricular function at rest and with exercise and silent myocardial ischemia

The prognostic value of radionuclide measures of left ventricular function at rest and exercise is well established. Some studies have suggested that the frequency and duration of silent ischemia during ambulatory monitoring provide similar prognostic information; however, studies comparing these two techniques have not been performed. This study examines the relation between left ventricular function at rest and exercise-induced ischemia assessed by radionuclide ventriculography with myocardial ischemia during ambulatory electrocardiographic (ECG) monitoring. Of the 155 patients with coronary artery disease studied, 88% had left ventricular dysfunction with exercise, defined as failure of the ejection fraction to increase by greater than 4% with exercise, and 33% of patients had left ventricular dysfunction at rest (ejection fraction less than 45%); 52% had transient episodes of ST segment depression during 48-h ambulatory ECG monitoring. Exercise-induced left ventricular dysfunction during radionuclide ventriculography was extremely sensitive (94%) in detecting patients with ischemic episodes during ambulatory ECG monitoring; however, only 55% of patients with exercise-induced left ventricular dysfunction had ST segment depression during ambulatory monitoring. Moreover, patients with left ventricular dysfunction at rest had a lower prevalence of transient episodes of ST segment depression (31%) than did patients with normal left ventricular function at rest (62%) (p = 0.008). The relation between prognostically important variables during exercise radionuclide ventriculography and the number and duration of transient episodes of ST depression was examined.(ABSTRACT TRUNCATED AT 250 WORDS)

Utility of stress echocardiography for postinfarct prognosis

Although high-risk patients following myocardial infarct are usually identified in the acute stage by clinical assessment and determination of left ventricular function at rest, a significant percentage of infarct patients with increased risks, i.e., presence of residual myocardial ischemia, remain undetected at discharge. Since the yield of adequate images for interpretation stress echocardiograms has been significantly improved with digital technology, stress echocardiography has become a truly practical technique to identify these patients. Presence of remote asynergy, i.e., asynergy not directly adjacent to the infarcted area and supposed to be related to another vascular region, directly following cessation of dynamic exercise appears to be highly related to multivessel disease and an unfavorable follow-up period. Treadmill electrocardiographic findings, however, appeared to be of limited value in this respect. Furthermore, the echocardiographic ejection fraction was also a poor predictor. The versatility of the technique, lack of injections, or radiation hazard, and the relatively low cost will undoubtedly increase the application of stress echocardiography for postinfarct stratification.

Risk stratification in survivors of acute myocardial infarction: routine cardiac catheterization and angiography is a reasonable approach in most patients

Noninvasive risk assessment in survivors of AMI can effectively subdivide patients into groups with differing risk profiles after hospital discharge, but some patients at risk for late death or recurrent AMI may be incorrectly identified; data from cardiac catheterization and angiography provide complementary and generally more powerful prognostic information. Many patients may derive particular benefit from early cardiac catheterization and angiography, including: (1) patients with AMI complicated by recurrent myocardial ischemia, congestive heart failure, and/or complex ventricular arrhythmias; (2) patients with abnormal or inconclusive results of noninvasive testing or those patients unable to perform an exercise test; (3) patients with abnormal left ventricular global systolic function and those with increased left ventricular end-systolic volume; (4) "young" patients (younger than 50 years of age?); (5) older patients (older than 65 to 70 years of age?); (6) patients with non-Q wave AMI; and (7) patients who are receiving thrombolytic therapy. Performance of early cardiac catheterization and angiography in virtually all survivors of AMI, with selective use of appropriate noninvasive tests, may provide a more efficacious means of risk assessment after AMI; if all tests are performed judiciously, the cost of such an approach need not be excessive. A combination of invasive and selected noninvasive tests probably provides optimal information. The risks to the routine performance of diagnostic cardiac catheterization and angiography in all survivors of AMI are: (1) adequate care and attention may not be paid to proper performance of the procedure(s) and to detailed and proper analyses of the data; (2) the need for additional noninvasive testing in selected patients may be ignored; and most importantly, (3) premature or unnecessary revascularization procedures may be performed subsequently. For optimal patient care, the clinician must obtain all necessary data, avoid unnecessary and repetitive tests, know the accuracy of individual tests at his or her own facility, interpret all data in proper context, and then counsel patients objectively about available management strategies. With this approach, all patients who might appropriately benefit from coronary artery revascularization will be correctly identified, and patients who are truly at very low risk (minimal residual coronary artery disease and preserved left ventricular function particularly if associated with a patent infarct-related artery) may be similarly identified and managed appropriately with elimination of unnecessary additional testing and pharmacologic therapy. Finally, whatever approach to risk stratification one chooses for an individual patient, the importance of and the need to correct and/or ameliorate risk factors for coronary artery disease must be recognized and undertaken.

Role of radionuclide ventriculography in evaluating cardiac function

The role of nuclear cardiology techniques for evaluating cardiac function has become increasingly important among other diagnostic techniques. The current status of radionuclide imaging of left and right ventricular function allows accurate diagnosis of cardiac patients with both coronary and noncoronary disease. The combination of gated first-pass and equilibrium radionuclide ventriculography makes it possible to assess more completely cardiac function than by either technique alone. Of particular interest to most imaging physicians is the current position of exercise ventriculography in the diagnostic setting, especially since this test has undergone new scrutiny in its application to broader patient segments. This technique and issues related to its place in the diagnostic environment are discussed in this review article, with emphasis on relevance to the clinical laboratory.

Enoximone: true inotropic effects? Do they cause ischemia? Analysis of end-systolic pressure-volume relations using the conductance (volume) catheter technique

True positive inotropy of enoximone is hard to prove clinically. It could increase the risk of myocardial ischemia when used in coronary artery disease (CAD). The analysis of the end-systolic pressure-volume relationship (ESPVR) as a load-independent parameter of the contractile left ventricular function (LVF) allows for differentiation of enoximone's unloading effects. Therefore, we analyzed ESPVR and LVF in 12 of 18 CAD patients before and after enoximone, 0.75 mg/kg intravenously. The slope k increased (seven patients) and loops of the ESPVR (12 patients) moved leftward with the enoximone an average of 32% and downward 19%, in the diastolic portion. The delta percent changes in enoximone versus control (18 patients) indicated an improved LVF via load changes: LV filling pressure fell by 50% and end-systolic volume by 28%, while dp/dt max rose by 25%, LV work by 10%, and ejection fraction by 11%. Lastly, the pacing-induced myocardial ischemia threshold increased from an average of 58 +/- 18 sec to 89 +/- 12 sec after eximone, while ischemic postpacing LV filling pressure and ST-segment changes normalized under the drug's influence. Thus, enoximone improved LVF, both by unloading and by true positive inotropy. Lack of enoximone-induced angina and an increased anginal threshold indicate that the drug can be used safely in CAD patients as well.

Prediction of cardiac events after uncomplicated myocardial infarction by cross-sectional echocardiography during transesophageal atrial pacing

Atrial pacing can safely be utilized shortly after myocardial infarction. To evaluate the prognostic value of wall motion abnormalities induced by such pacing 83 consecutive patients with recent uncomplicated myocardial infarction underwent transthoracic cross-sectional echocardiography during transesophageal atrial pacing and upright bicycle exercise stress test. Patients were followed-up for 14 +/- 5 months. During the atrial pacing and the echocardiography, patients were defined at high risk if abnormalities of wall motion were detected in left ventricular regions remote from the infarcted area. Then, during the exercise stress test, high risk patients were those with ST segment depression greater than or equal to 1 mm. On the other hand, patients were considered to be at low risk if they had no abnormalities of wall motion during atrial pacing in remote regions or, in the case of the stress test, if they did not develop ST depression greater than or equal to 1 mm. Of the 83 patients, 21 had major cardiac events during the period of follow-up. Cardiac events occurred in 15/23 (65%) and 5/60 (8%, P less than 0.001) patients assigned to the groups adjudged to be at high and low risk, respectively, on the basis of echocardiographic results. Exercise testing was less reliable in identifying patients at risk of future cardiac events. Major events occurred in only 6 of the 19 patients with a positive stress test (32%, P less than 0.05 vs positive stress echocardiography) and in 14 of the 64 patients with a negative exercise stress test (22%, P = NS vs positive exercise stress test, P less than 0.05 vs negative atrial pacing echocardiography).

Exercise testing: uses and limitations considering recent studies

Accurate use and interpretation of exercise test results depend on an understanding of physiologic principles, meticulous attention to proper methodology, and realization of the appropriate applications and limitations of testing. Understanding the relationship between myocardial and ventilatory oxygen consumption and exercise test variables will aid in the diagnosis and prognostic evaluation. Use of proper methodology in preparing the patient, performing the examination, and interpreting the results is critical to obtaining the maximum information with maximum safety for each individual patient. Improvements in methodology including the use of the Borg scale to estimate individual effort, abandonment of the predicted maximum heart rate, and the increased use of ventilatory oxygen uptake measurements should be applied. Exercise capacity should not be reported in total time but rather as the VO2 or MET equivalent of the workload achieved. This permits the comparison of the results of many different exercise testing protocols. The most useful exercise ECG variable for the diagnosis of coronary artery disease remains the ST segment shift. Unfortunately, it is not as helpful in localizing myocardial ischemia. Diagnostic accuracy can be improved by adjusting ST depressions for exercise-induced heart rate increase. Accuracy can be further increased by combining ECG, clinical, and radionuclide variables in probabilistic formulas that retain the independent diagnostic information from each variable and accurately predict disease probability. To avoid errors in clinical decision making, care must be used to insure that the mathematical formula used was derived from a population of patients that is similar to those being tested. The clinical applications for exercise testing include diagnosis of patients with chest pain syndromes, determination of disease severity, and prognosis in patients with known coronary artery disease, evaluation of arrhythmias, screening of asymptomatic patients, and evaluation of medical, surgical, and angioplastic therapy for coronary disease. In spite of studies involving thousands of patients, controversy exists regarding the diagnostic power of exercise testing. The large differences in reported accuracies are largely due to methodologic problems that have been encountered by various investigators. Clinicians should be made aware of these problems when reading the literature on ECG and radionuclide exercise testing. Such awareness will help them understand the limitations of these noninvasive procedures.(ABSTRACT TRUNCATED AT 400 WORDS)

Comparative accuracy of clinical tests for diagnosis and prognosis of coronary artery disease

The discriminant accuracy of 14 variables derived from clinical evaluation, cardiac fluoroscopy, exercise electrocardiography, thallium scintigraphy and radionuclide angiography was assessed with respect to the diagnosis of angiographic coronary artery disease (CAD) among 607 patients undergoing coronary angiography, and with respect to the prognosis of subsequent cardiac death or nonfatal infarction among 4,104 patients followed for 1 year after testing. Discriminant accuracy (quantified in terms of the area under a receiver-operating characteristic curve for each variable) ranged from 50 to 73% for diagnosis, and from 54 to 77% for prognosis. Although there was a great deal of variability from test to test, variables representing direct or indirect manifestations of myocardial ischemia tended to correlate better with prognosis. Thus, variables derived from radionuclide angiography and thallium scintigraphy tended to have more prognostic accuracy than diagnostic accuracy, while fluoroscopy tended to have more diagnostic accuracy than prognostic accuracy. The pattern associated with clinical evaluation and exercise electrocardiography was less discernable. Accordingly, the accuracy of noninvasive tests with respect to diagnosis and prognosis of CAD should be separately determined based on individual empiric observation.

Cardiac nuclear medicine

In this paper, the principal applications of nuclear medicine to studies of the heart are described. First, gated cardiac blood pool imaging is discussed, then thallium-201 myocardial imaging, myocardial infarct scintigraphy with 99mTc pyrophosphate, and evaluation of intracardiac shunts. In gated cardiac blood pool imaging, the patient's red blood cells are labeled with 99mTc. Images of the cardiac blood pool are then obtained in multiple projections and displayed in an endless-loop cine display. Quantitative indices of cardiac function are readily obtained, and a variety of functional images can be generated. Blood pool imaging may also be performed with use of a first-pass technique that yields similar information. Applications of blood pool imaging are discussed. The theory and techniques of planar and tomographic thallium-201 myocardial imaging are described, together with their application in the diagnosis of coronary artery disease. The prognostic value of thallium imaging is also examined. Myocardial infarct imaging with 99mTc pyrophosphate is described, and clinical indications are reviewed. Left-to-right cardiac shunts can be evaluated by following the first transit of a bolus of radiopharmaceutical through the lungs. Right-to-left shunts may be evaluated by injection of 99mTc macroaggregated albumin.

Effect of age on long-term prognosis of patients with myocardial infarction

We studied 181 patients aged under 65 years and 129 patients over 65 with acute myocardial infarction. There were no major differences in the prevalence of coronary risk factors, angina or previous myocardial infarction. A larger percentage of elderly patients had congestive heart failure (51.4% vs 32.6%, P less than 0.001) and complete heart block (17.1% vs 7.2%, P less than 0.01) during the acute phase. In-hospital mortality was significantly higher in the elderly patients (34% vs 16%, P less than 0.01). Late mortality rates correlated in both groups with the Killip class at the time of infarction and with the occurrence of reinfarction. In the elderly group, it was also associated with complete heart block during the acute phase. Five-year survival was 80% in the older and 72% in the younger patients (P = 0.1). Age did not affect survival of Killip class I patients (85% vs 86%, P = 0.83), but life expectancy was significantly reduced in elderly patients in Killip class greater than II (39% vs 60%, P less than 0.05). In conclusion, elderly patients cannot be considered a homogeneous group of high-risk patients. Clinical variables at the time of infarction can identify low- and high-risk subsets among them. Age constitutes an independent prognostic factor for late mortality when any degree of heart failure is present.

Mental stress and the induction of silent myocardial ischemia in patients with coronary artery disease

To assess the causal relation between acute mental stress and myocardial ischemia, we evaluated cardiac function in selected patients during a series of mental tasks (arithmetic, the Stroop color--word task, simulated public speaking, and reading) and compared the responses with those induced by exercise. Thirty-nine patients with coronary artery disease and 12 controls were studied by radionuclide ventriculography. Of the patients with coronary artery disease, 23 (59 percent) had wall-motion abnormalities during periods of mental stress and 14 (36 percent) had a fall in ejection fraction of more than 5 percentage points. Ischemia induced by mental stress was symptomatically "silent" in 19 of the 23 patients with wall-motion abnormalities (83 percent) and occurred at lower heart rates than exercise-induced ischemia (P less than 0.05). In contrast, we observed comparable elevations in arterial pressure during ischemia induced by mental stress and ischemia induced by exercise. A personally relevant, emotionally arousing speaking task induced more frequent and greater regional wall-motion abnormalities than did less specific cognitive tasks causing mental stress (P less than 0.05). The magnitude of cardiac dysfunction induced by the speaking task was similar to that induced by exercise. Personally relevant mental stress may be an important precipitant of myocardial ischemia--often silent--in patients with coronary artery disease. Further examination of the pathophysiologic mechanisms responsible for myocardial ischemia induced by mental stress could have important implications for the treatment of transient myocardial ischemia.

Silent myocardial ischemia: II. Prognosis and implications for the clinical assessment of patients with coronary artery disease

Myocardial ischemia is known to be a strong independent predictor of cardiac events. New data suggest that the presence of silent ischemia, like symptomatic ischemia, is indicative of an increased risk of future cardiac events. Ordinarily, patients with suspected or known coronary artery disease are evaluated first for the presence of myocardial ischemia by performing exercise ECG, used as a test of both diagnosis and prognosis. In those patients who have an "intermediate" probability of cardiac event after exercise ECG, prognostic assessment may be enhanced, by using either radionuclide stress testing, to assess the extent and severity of potentially inducible ischemia, or ambulatory ECG, to assess the frequency and duration of spontaneously occurring ischemia. The indications for testing and type of test to be used are highly dependent on a number of clinical factors, not the least of which are the nature of the population to be evaluated and the exercise ECG response. We have proposed an overall approach for prognostic testing that considers the potential strengths and limitations of each form of testing. This potential approach now requires prospective evaluation.

Usefulness of ejection fraction response to exercise one month after acute myocardial infarction in predicting coronary anatomy and prognosis

The prognostic value of left ventricular (LV) ejection fraction (EF) measured during maximal exercise testing early after acute myocardial infarction (AMI) was assessed in 75 patients, aged 65 years or younger, a mean of 36 days after AMI. At follow-up for a mean 12 months (range 6 to 26), medical complications developed in 15 patients: cardiac death in 5, ventricular fibrillation in 1, reinfarction in 2, unstable angina in 5, and severe cardiac failure in 2. Seven other patients underwent coronary artery bypass grafting for severe angina. When LVEF less than 50% at rest was compared with LVEF of 50% or more, the 2-year life-table survival free of complications was 54 +/- 21% compared with 84 +/- 19% (p less than 0.05). When exercise LVEF less than 50% was compared with LVEF of 50% or more, the 2-year survival rate free of medical complication was 42 +/- 32% compared with 83 +/- 20% (p less than 0.05). LVEF change from rest to exercise was not related to prognosis. Patients with combined medical and surgical events tended to have lower rest and exercise LVEFs, but changes in LVEF during exercise were again unrelated to prognosis. Sixty-five patients underwent coronary arteriography. After inferior AMI the mean LVEF was lower in those with multivessel than in those with 1-vessel coronary artery disease at rest (47 +/- 13% vs 59 +/- 7%, p less than 0.005) and during exercise (47 +/- 13% vs 59 +/- 9%, p less than 0.005); however, the change in LVEF during exercise was not related to coronary anatomy anatomy.(ABSTRACT TRUNCATED AT 250 WORDS)

The efficacy of cardiovascular nuclear medicine exercise studies

Radionuclide stress tests were initially introduced into medicine as new diagnostic tests for coronary artery disease (CAD). These tests are very effective for this purpose when applied to populations with an intermediate pre-test probability of coronary artery disease. Radionuclide stress tests, however, also are used now in guiding many management decisions in patients with established CAD, based on the ability of these tests to assess the extent and severity of myocardial ischemia, the functional significance of coronary stenoses, and myocardial viability. Specific uses beyond diagnosis include decisions regarding whom to catheterize, send to coronary bypass surgery, or angioplasty; risk stratification following myocardial infarction or before noncardiac surgery; and evaluation of the results of therapy. This article reviews both the diagnostic efficacy of radionuclide stress tests and their efficacy in guiding management decisions in patients with known coronary artery disease.

Role of nuclear cardiology in evaluating the total ischemic burden in coronary artery disease

Goals of exercise radionuclide imaging are to: enhance sensitivity, specificity and predictive value of coronary artery disease (CAD) detection; noninvasively assess extent and severity of functionally significant CAD; determine prognosis so that specific therapeutic strategies can be more rationally implemented; detect silent ischemia in asymptomatic subjects or in patients with known CAD with a higher degree of specificity than can be accomplished by electrocardiogram stress testing alone; evaluate the response to therapeutic interventions aimed at enhancing coronary blood flow. Two major radionuclide techniques are currently used in evaluating the total ischemic burden in patients with CAD. These are myocardial perfusion imaging with either thallium-201 or rubidium-82, and radionuclide angiography performed after administration of technetium-99m. Areas of diminished thallium-201 activity on early postexercise images are abnormal and represent either areas of stress-induced ischemia or myocardial scar. To differentiate between the two, delayed images are obtained to determine if the initial postexercise defect either persists or demonstrates redistribution (i.e., delayed defect disappearance or improvement). Defects demonstrating redistribution represent transient ischemia, whereas areas of previous infarction or scar usually appear as persistent defects. Patients with left main or 3-vessel CAD usually show multiple thallium-201 redistribution defects in more than 1 vascular supply region, a phenomenon often associated with abnormal lung thallium-201 uptake. In terms of radionuclide angiography, the normal ventricular response to exercise has been defined as an absolute increment of at least 5% in the left ventricular ejection fraction without the development of regional wall motion abnormalities.(ABSTRACT TRUNCATED AT 250 WORDS)

Non-invasive detection of coronary artery disease by body surface electrocardiographic mapping after dipyridamole infusion

Electrocardiographic changes after dipyridamole infusion (0.568 mg/kg/4 min) were studied in 41 patients with coronary artery disease and compared with those after submaximal treadmill exercise by use of the body surface mapping technique. Patients were divided into three groups; 19 patients without myocardial infarction (non-MI group), 14 with anterior infarction (ANT-MI) and eight with inferior infarction (INF-MI). Eighty-seven unipolar electrocardiograms (ECGs) distributed over the entire thoracic surface were simultaneously recorded. After dipyridamole, ischemic ST-segment depression (0.05 mV or more) was observed in 84% of the non-MI group, 29% of the ANT-MI group, 63% of the INF-MI group and 61% of the total population. Exercise-induced ST depression was observed in 84% of the non-MI group, 43% of the ANT-MI group, 38% of the INF-MI group and 61% of the total. For individual patients, there were no obvious differences between the body surface distribution of ST depression in both tests. The increase in pressure rate product after dipyridamole was significantly less than that during the treadmill exercise. The data suggest that the dipyridamole-induced myocardial ischemia is caused by the inhomogenous distribution of myocardial blood flow. We conclude that the dipyridamole ECG test is as useful as the exercise ECG test for the assessment of coronary artery disease.

Use of radionuclide angiography and an electrocardiographic stress test to diagnose multivessel disease after a first episode of uncomplicated myocardial infarction

Sixty consecutive patients who were symptom free 2-12 months after an uncomplicated acute myocardial infarction underwent maximal treadmill exercise testing, radionuclide angiography before and during submaximal bicycle stress test, and coronary angiography. The results of the non-invasive procedures were compared with those of coronary angiography. The sensitivity and specificity of electrocardiogram stress test for detection of multivessel disease were 40% and 77% respectively. Failure of left ventricular ejection fraction to increase at least 5% with exercise identified 20 of the 25 patients with multivessel disease (sensitivity 80%) and 23 of the 35 patients with no additional coronary artery stenosis (specificity 66%). In patients with anterior Q waves the sensitivity was 78% and the specificity 50%, whereas in the presence of inferior Q waves these values were 81% and 87% respectively. Loss of left ventricle synchronicity during effort, as indicated by failure of the standard deviation of the phases to decrease during exercise, demonstrated a radionuclide angiography sensitivity of 80% (77% for anterior myocardial infarction and 81% for inferior myocardial infarction) and a specificity of 50% (33% for anterior myocardial infarction and 64% for inferior myocardial infarction). When the test was considered to be positive if either the ejection fraction or the standard deviation of the phases criteria were positive, the sensitivity was 100% and specificity 46% (30% for anterior myocardial infarction and 65% for inferior myocardial infarction). It is concluded that in patients who are free from angina 2-12 months after an episode of uncomplicated myocardial infarction, a simple exercise electrocardiogram cannot be relied upon to detect residual ischaemia. An abnormal ejection fraction response or an increased standard deviation of the phases during exercise nuclear angiography or both identified all the patients with multivessel disease. None of the patients in whom radionuclide angiographic criteria were negative had multivessel disease.

Should the intent of testing influence its interpretation?

A test is often interpreted as "normal" or "abnormal" by a single criterion, regardless of the intent of testing. The discriminate accuracy of this convention was critically analyzed using information content (I), likelihood ratio and the area under the receiver-operating characteristic curve. Three ejection fraction variables were assessed--ejection fraction at rest, exercise ejection fraction and the change in ejection fraction from rest to exercise--each relative to three intentional goals: diagnosis of coronary artery disease in 929 patients without previous myocardial infarction, prediction of multivessel disease in these same 929 patients and prediction of multivessel disease in 507 patients with previous myocardial infarction. The information content of exercise ejection fraction (IEX) was higher than for ejection fraction at rest (IR) or for the change from rest to exercise (IEX-R), and was relatively constant regardless of the goal of testing. In contrast, neither IR nor IEX-R was constant. IR was lowest for diagnosis of coronary artery disease, whereas IEX-R was highest for this same goal. These empiric observations are consistent with the quantitative relation predicted by information theory: IEX = IR + IEX-R. Thus, ejection fraction at rest has little discriminate value relative to the diagnosis of coronary artery disease, but does have value in evaluating the extent of disease in patients after myocardial infarction. Exercise ejection fraction and change in ejection fraction are nearly equally useful for purposes of diagnosis, whereas the former is most useful for functional evaluation in postinfarction patients.(ABSTRACT TRUNCATED AT 250 WORDS)