Noninvasive identification of severe coronary artery disease using exercise radionuclide angiography

Normal response of cardiac flow and function to adenosine stress as assessed by cardiac MR

AIMS

To establish the response of cardiac flow and function to adenosine stress using phase-contrast magnetic resonance (pcMR) and cine steady-state free precession (SSFP) cardiac magnetic resonance (CMR).

METHODS

Healthy volunteers (n = 10) were scanned on 1.5T at rest and under adenosine stress utilizing short-axis SSFP sequences and pcMR of the aorta and pulmonary trunk.

RESULTS

Adenosine-induced increase in heart rate was 62.7% (P < 0.001). Left and right-ventricular stroke volumes (SVs) increased by 12.2% (P = 0.048) and 11.9% (P = 0.044), left-ventricular ejection fraction by 11.8% (P = 0.002), and left-ventricular and right-ventricular cardiac output (CO) by 81.0% (P < 0.001) and 81.8% (P = 0.005). Average flow velocities in the ascending aorta and pulmonary trunk increased by 77.3% (P < 0.001) and 73.6% (P < 0.001), and peak flow velocities in the ascending aorta and pulmonary trunk by 27.2% (P < 0.001) and 22.4% (P = 0.003). End-systolic volumes in the left ventricle (LV) and right ventricle (RV) decreased by 16.4% (P = 0.020) and 19.2% (P = 0.028). Planimetric cine SSFP and pcMR-derived SV showed an excellent correlation.

CONCLUSION

In healthy volunteers, response to adenosine stress is characterized by an increase in heart rate, CO and SV of both ventricles. Excellent correlation is demonstrated between these increases and the increased blood flow velocities in the aorta and the pulmonary trunk. Thus, results support the use of flow measurements as an internal control of planimetric measurements of ventricular SV and CO.

Quantitative Assessment of Left Ventricular Function During Contrast-Enhanced Dobutamine Stress Echocardiography Predicts Future Cardiac Events in Diabetic Patients

BACKGROUND

Non-invasive diagnosis and risk stratification of coronary artery disease are important for the selection and optimization of therapeutic interventions in diabetic patients, which may improve survival. The aim of this study was to determine the incremental value of contrast-enhanced dobutamine stress echocardiography (CE-DSE) for risk stratification.

METHODS AND RESULTS

CE-DSE was performed in 326 patients with diabetes mellitus (mean age; 66 +/- 10 years, 223 men). All patients were followed up for a mean of 29 months (1-61 months). Dobutamine was infused in a standard protocol with an intravenous contrast agent. The primary endpoints for hard cardiac events included cardiac death and nonfatal myocardial infarction. The primary endpoints for total cardiac events included hard cardiac events, unstable angina pectoris, congestive heart failure, and late coronary revascularization (> 3 months). Cardiac events occurred in 74 patients. The addition of the CE-DSE results, including abnormal left ventricular end-systolic volume response and left ventricular ejection fraction at peak stress < 50%, to the clinical and rest echocardiography model provided incremental information in predicting total cardiac events (increase in chi-square value for the model from 17 to 24, p < 0.05) and hard cardiac events (increase in chi-square value for the model from 18 to 24, p < 0.05).

CONCLUSIONS

Quantitative assessment of left ventricular function during CE-DSE provides incremental prognostic information in predicting cardiac events in diabetic patients.

Left Ventricular Ejection Fraction Change with Exercise Versus Ejection Fraction at Rest in Coronary Artery Disease: Implications for Using Ejection Fraction Variations in Making Therapeutic Decisions

Previous studies have differed regarding the prognostic importance of the change (Delta) in left ventricular ejection fraction (LVEF) with exercise among patients with known or suspected coronary artery disease (CAD). Data suggest that these discrepancies may be owing to patient selection, including wide interstudy variations in the range of LVEFrest at study entry; however, the impact of LVEFrest on LVEF exercise response has not been adequately addressed. To test the hypothesis that magnitude and variability in DeltaLVEF are systematically related to LVEFrest, we analyzed data from 2655 patients who underwent rest/exercise radionuclide cineangiography for evaluation of clinically evident CAD, stratified into 5 successive LVEFrest subgroups: <30% (n = 205), 30%-44% (n = 563), 45%-59% (n = 1529), 60%-75% (n = 324), and >75% (n = 34). The standard deviation of DeltaLVEF among patients with LVEFrest <30% was found to be half that among patients in the higher LVEFrest subgroups (P < 0.00001, global). The average magnitude of the rise and fall in LVEF with exercise also varied markedly among LVEFrest subgroups (P < 0.0001, global), being smallest among patients with LVEFrest <30%. These findings may explain differences in predictive accuracy of DeltaLVEF noted among various study populations. Further study is needed to determine whether LVEFrest should be used in selecting exercise-based prognostic descriptors in individual patients.

Prognostic value of exercise echocardiography in patients after coronary artery bypass surgery

To assess the prognostic value of exercise echocardiography in patients with prior coronary artery bypass surgery, follow-up was obtained in 718 patients (591 men [82%] and 127 women [18%], aged 67 +/- 9 years) who underwent clinically indicated exercise echocardiography 5.7 +/- 4.7 years after coronary bypass surgery. Resting wall motion abnormalities were present in 479 patients (67%). New or worsening wall motion abnormalities developed with exercise in 366 patients (51%). During a median follow-up of 2.9 years, cardiac events included cardiac death in 36 patients and nonfatal myocardial infarction in 40 patients. The addition of the exercise echocardiographic variables, abnormal left ventricular end-systolic volume response and exercise ejection fraction to the clinical, resting echocardiographic and exercise electrocardiographic model provided incremental information in predicting cardiac events (chi-square 37 to chi-square 42, p = 0.02) and cardiac death (chi-square 38 to chi-square 43, p <0.02). Exercise echocardiography provides prognostic information in patients after coronary artery bypass surgery, incremental to clinical, rest echocardiographic, and exercise electrocardiographic variables.

Prognostic value of exercise echocardiography in 2,632 patients > or = 65 years of age

OBJECTIVES

We sought to determine the prognostic value of exercise echocardiography in the elderly.

BACKGROUND

Limited data exist regarding the prognostic value of exercise testing in the elderly, a population which may be less able to exercise and is at increased risk of cardiac death.

METHODS

Follow-up (2.9 +/- 1.7 years) was obtained in 2,632 patients > or = 65 years who underwent exercise echocardiography.

RESULTS

There were 1,488 (56%) men and 1,144 (44%) women (age 72 +/- 5 years). The rest ejection fraction was 56 +/- 9%. Rest wall motion abnormalities were present in 935 patients (36%). The mean work load was 7.7 +/- 2.3 metabolic equivalents (METs) for men and 6.5 +/- 1.9 METs for women. New or worsening wall motion abnormalities developed with stress in 1,082 patients (41%). Cardiac events included cardiac death in 68 patients and nonfatal myocardial infarction in 80 patients. The addition of the exercise electrocardiogram to the clinical and rest echocardiographic model provided incremental information in predicting both cardiac events (chi-square = 77 to chi-square = 86, p = 0.003) and cardiac death (chi-square = 71 to chi-square = 86, p < 0.0001). The addition of exercise echocardiographic variables, especially the change in left ventricular end-systolic volume with exercise and the exercise ejection fraction, further improved the model in terms of predicting cardiac events (chi-square = 86 to chi-square = 108, p < 0.0001) and cardiac death (chi-square = 86 to chi-square = 99, p = 0.004).

CONCLUSIONS

Exercise echocardiography provides incremental prognostic information in patients > or = 65 years of age. The best model included clinical, exercise testing and exercise echocardiographic variables.

Risk stratification in patients with chest pain

This article reviews the role of exercise testing in the assessment of patients with suspected coronary disease. To accomplish this, four major topics are considered: the general concept of risk stratification; the estimation of outcomes using data from the initial evaluation of the patient; diagnostic assessment with the exercise test; and prognostic assessment with the exercise test. This review focuses on the standard treadmill exercise test.

Stable Angina Pectoris

Patients with stable Canadian Heart Classification I or II angina pectoris may be managed successfully with a conservative medical program. Such a program should always include aspirin, beta-blocking agents, and lipid-lowering therapies unless contraindications to them exist. Exercise and dietary restrictions will achieve target lipid values in some patients; the remainder should be treated with a lipid-lowering drug if they are at high risk of cardiac events. Emerging data support a role for angiotensin-converting enzyme inhibitors in many, if not all, patients with coronary artery disease. The role of calcium antagonists in this population remains uncertain, with some favorable and some unfavorable effects seen with these agents. High-risk patients and those with a desire to achieve greater exercise tolerance once medical therapies have been optimized are suitable candidates for angiographic study and revascularization. Although randomized studies addressing this population are limited, available data support the benefits of either coronary artery bypass grafting or percutaneous catheter intervention.

Identification of severe coronary artery disease in patients with a single abnormal coronary territory on exercise thallium-201 imaging: the importance of clinical and exercise variables

OBJECTIVES

The aim of this study was to determine which clinical, exercise and thallium variables can aid in the identification of three-vessel or left main coronary artery disease (3VLMD) in patients with one abnormal coronary territory (either a reversible or fixed defect) on exercise thallium testing and to test the prognostic value of these variables.

BACKGROUND

Although the sensitivity of detection of coronary artery disease by thallium-201 imaging is high, the actual detection of 3VLMD by thallium tomographic images alone is not optimal.

METHODS

A multivariate model for prediction of 3VLMD was developed from several clinical, exercise and thallium-201 variables in a training population of 264 patients who had one abnormal coronary artery territory on exercise thallium testing and had undergone coronary angiography. Using this model, patients were stratified into risk groups for prediction of 3VLMD. A separate validation cohort of 474 consecutive patients who were treated initially with medical therapy and who had one abnormal coronary territory were divided into identical risk groupings by the variables derived from the training population, and they were followed for a median of 7.0 years to evaluate the prognostic value of this model.

RESULTS

The prevalence of 3VLMD was 26% in the training population despite one abnormal thallium coronary territory. Four clinical and exercise variables--diabetes, hypertension, magnitude of ST segment depression, and exercise rate-pressure product-were found to be independent predictors of 3VLMD. In the training population, the prevalence of 3VLMD in low-, intermediate- and high-risk groups was 15%, 22% and 51%, respectively. When the multivariate model was applied to the validation population, the eight-year overall survival rates in the low-, intermediate- and high-risk groups were 89%, 73% and 75%, respectively (p < 0.001).

CONCLUSIONS

A substantial proportion of patients with one abnormal thallium coronary territory have 3VLMD with subsequent divergent outcomes based upon risk stratification by clinical and exercise variables. Consequently, the finding of only a single abnormal coronary territory by thallium-201 perfusion imaging does not necessarily confer a benign prognosis in the absence of consideration of nonimaging variables.

Prospective identification of myocardial stunning using technetium-99m sestamibi-based measurements of infarct size

OBJECTIVES

We sought to prospectively identify patients with stunning and hyperkinesia at hospital discharge on the basis of mismatches between left ventricular (LV) function and infarct size as assessed by technetium-99m (Tc-99m) sestamibi perfusion tomographic imaging.

BACKGROUND

Mechanical indexes of LV function may not accurately reflect myocardial damage after acute myocardial infarction (MI) because of myocardial stunning and compensatory hyperkinesia in noninfarct-related territories. Myocardial perfusion techniques are unaffected by these variables.

METHODS

Eighty-four patients with acute MI underwent hospital admission and discharge Tc-99m-sestamibi tomographic imaging. Global LV ejection fraction (LVEF) was measured at hospital discharge and 6 weeks later. The perfusion defect size was quantified and expressed as a percentage of the LV. The discharge perfusion defect, which is a measure of infarct size, was used to predict the 6-week LVEF for each patient based on a previously reported regression equation. Patients were classified into one of three groups depending on whether their LVEF at hospital discharge fell within, above or below one standard error (6.8 LVEF points) of the predicted 6-week LVEF.

RESULTS

There were 48 patients classified as having a "match" between function and infarct size; these patients demonstrated no significant change in LVEF at 6 weeks. There were 21 patients (25%) classified as "mismatch stunned" who had discharge LVEFs lower than those predicted by infarct size. These patients demonstrated a significant improvement in mean LVEF at 6 weeks (mean [+/-SD] discharge LVEF 0.41 +/- 0.08, 6-week LVEF 0.47 +/- 0.10; p = 0.003). Fifteen patients (18%) were classified as "mismatch-hyperkinetic." The mean LVEF for these patients significantly declined at 6 weeks (discharge LVEF 0.64 +/- 0.06, 6-week LVEF 0.58 +/- 0.09; p = 0.002). There was a marked increase in LVEF within the infarct zone (8 +/- 15 LVEF points; p = 0.03) for patients predicted to have stunning and a marked decline in LVEF outside the infarct zone (9 +/- 15 LVEF points; p = 0.06) in patients predicted to have hyperkinesia. Both discharge LVEF (p < 0.0001) and group classification (p = 0.005) were independent predictors of LVEF 6 weeks later.

CONCLUSIONS

Perfusion imaging with Tc-99m-sestamibi can identify post-MI patients at hospital discharge in whom LV function is discordant with the measured infarct size. Patients with stunning have late increases in LVEF; patients with hyperkinesia have late decreases. This methodology, performed at discharge, is predictive of late changes in LV function.

Worsening left ventricular performance on serial exercise radionuclide angiography does not identify high-risk patients

OBJECTIVE

To determine whether worsening exercise performance on serial exercise radionuclide angiography identifies patients at increased risk of future cardiac events.

MATERIAL AND METHODS

One hundred nine medically treated patients with previous Q-wave myocardial infarction underwent two exercise radionuclide angiographic studies at least 6 months apart (median, 16 months) without an intervening clinical event. Worsening exercise performance between the two studies was defined by five criteria: (1) lower (5% or more) peak exercise ejection fraction; (2) worsening peak exercise wall motion score; (3) combination of criteria 1 and 2; (4) worsening serial delta (exercise - rest) ejection fraction; or (5) increasing exercise ST-segment depression of 1 mm or more. Patients were followed up for a median duration of 3.9 years after the second exercise study.

RESULTS

Five cardiac deaths and 10 nonfatal myocardial infarctions occurred during follow-up. A Cox proportional hazards analysis failed to show an association between any of the aforementioned variables and cardiac events. Of the 15 patients with cardiac events, 4 (27%) had a lower (5% or more) exercise ejection fraction and 2 (13%) had a worsening exercise wall motion score. Of the 94 patients without cardiac events, 37 (39%) had a lower (5% or more) exercise ejection fraction and 28 (30%) had a worsening serial exercise wall motion score (not a statistically significant difference).

CONCLUSION

Worsening exercise performance on serial exercise radionuclide angiography does not identify patients at increased risk of future cardiac events.

Quantitative measures of regional asynergy add independent prognostic information to left ventricular ejection fraction in patients with prior myocardial infarction

The purpose of this study was to determine if quantitative measurements of regional asynergy add independent prognostic information to global ejection fraction in patients with chronic coronary artery disease. Four hundred eighty-six patients with a history of Q-wave myocardial infarction who underwent gated-equilibrium radionuclide angiography at least 3 months after infarction were monitored for a median duration of 4.7 years. During follow-up there were 95 deaths. Four of five regional asynergy indexes analyzed were associated with overall mortality. The strength of the association between overall mortality and the index that proved to be optimal (univariate chi2 = 26.4, p < 0.001) was stronger than for global ejection fraction (univariate chi2 = 21.5, p < 0.001). For patients with global ejection fraction <40%, 4-year survival was 87% for those with a low asynergy index versus 65% for those with a high asynergy index (p = 0.016). In conclusion, indexes of regional asynergy add independent prognostic information to global left ventricular ejection fraction.

Beneficial effects of RheothRx injection in patients receiving thrombolytic therapy for acute myocardial infarction. Results of a randomized, double-blind, placebo-controlled trial

BACKGROUND

RheothRx (poloxamer 188) is a surfactant with hemorheological and antithrombotic properties that reduces myocardial reperfusion injury in animal models of myocardial infarction. The purpose of the present study was to evaluate the safety and efficacy of adjunctive therapy with poloxamer 188 in patients receiving thrombolytic therapy for acute myocardial infarction.

METHODS AND RESULTS

In this multicenter trial, we randomized 114 patients to a 48-hour infusion of poloxamer 188 or vehicle placebo beginning immediately after the initiation of thrombolytic therapy. Tomographic imaging with 99mTc sestamibi before reperfusion and again 5 to 7 days after the infarction was used to determine myocardium at risk for infarction, infarct size, and myocardial salvage. Radionuclide angiography at 5 to 7 days after infarction was used to measure left ventricular ejection fraction. The treated and control groups had comparable baseline characteristics, time to thrombolytic administration, and time to treatment with poloxamer 188 or placebo. Poloxamer 188-treated patients demonstrated a 38% reduction in median myocardial infarct size (25th and 75th percentile) compared with placebo (16% [7, 30] versus 26% [9, 43]; P = .031), greater median myocardial salvage (13% [7, 20] versus 4% [1, 15]; P = .033), and a 13% relative improvement in median ejection fraction (52% [43, 60] versus 46% [35, 60]; P = .020). Poloxamer 188 treatment also resulted in a reduced incidence of reinfarction (1% versus 13%; P = .016). Poloxamer 188 was well tolerated without adverse hemodynamic effects or significant organ toxicity.

CONCLUSIONS

Adjunctive therapy with poloxamer 188 resulted in substantial benefit in this randomized trial, including significantly smaller infarcts, greater myocardial salvage, better left ventricular function, and a lower incidence of in-hospital reinfarction. Although the mechanisms are unproven, poloxamer 188 treatment may accelerate thrombolysis, reduce reocclusion, and ameliorate reperfusion injury.

Cardiovascular stress testing: a description of the various types of stress tests and indications for their use

OBJECTIVE

To describe the various types of stress tests and to provide guidelines for selecting a specific test for an individual patient.

MATERIAL AND METHODS

Myocardial perfusion imaging, radionuclide angiography, stress echocardiography, and cardiopulmonary exercise testing are described. The advantages and limitations of these techniques are reviewed and compared with those of standard treadmill exercise testing. The agents used for pharmacologic stress testing are discussed.

RESULTS

Standard treadmill exercise testing is widely available and is less expensive than the imaging techniques. It is most accurate in patients with normal findings on a resting electrocardiogram who are not taking digoxin. In these patients, standard exercise electrocardiography is almost as accurate as the exercise imaging modalities for identifying those with left main or three-vessel coronary artery disease. Advantages of the stress imaging modalities in comparison with standard exercise electrocardiography include greater accuracy when the resting electrocardiogram shows abnormal findings, higher sensitivity, ability to localize and characterize the extent of myocardial ischemia, and direct measurement of other variables such as left ventricular function. These techniques must be performed carefully in experienced laboratories in order to provide accurate information. Published data are scant that directly compare one technique with another in the same set of patients. The nuclear cardiology techniques have been well validated for detecting left main and three-vessel coronary artery disease and for assessing prognosis. Myocardial perfusion imaging has been well validated for detecting ischemia in patients with abnormal left ventricular function at rest. In comparison with the nuclear cardiology techniques, stress echocardiography is less expensive and provides more ancillary information but has not been as well validated for assessment of severe coronary artery disease or prognosis. Cardiopulmonary exercise testing can be useful in selecting patients for cardiac transplantation and in assessing exertional dyspnea in selected patients. The most common application of pharmacologic stress testing is preoperative risk assessment of patients undergoing noncardiac operations. Pharmacologic stress testing should usually be reversed for patients who are unable to exercise adequately.

CONCLUSION

Most patients with normal findings on a resting electrocardiogram who are not taking digoxin should undergo standard treadmill exercise testing for diagnostic and prognostic purposes. Most patients with abnormal findings on a resting electrocardiogram should undergo one of the stress imaging techniques. Selecting a specific stress imaging techniques. should depend primarily on local expertise with the various techniques and secondarily on the strengths and limitations of the techniques as they relate to the individual patient.

Infarct size after acute myocardial infarction measured by quantitative tomographic 99mTc sestamibi imaging predicts subsequent mortality

BACKGROUND

99mTc sestamibi is a recently developed radioisotope that has been used to measure myocardium at risk and infarct size. The relation between these measurements and subsequent patient outcome has not yet been demonstrated.

METHODS AND RESULTS

Two hundred seventy-four consecutive patients with acute myocardial infarction underwent tomographic 99mTc sestamibi imaging on arrival at the hospital (to measure myocardium at risk before reperfusion therapy) and at hospital discharge (to measure the amount of salvaged myocardium and final infarct size). Defect size on the sestamibi images was quantified using a threshold value of 60% of peak counts from the circumferential count profile curves generated for five representative slices of the left ventricle. Patients were followed after hospital discharge to evaluate the association between final infarct size and subsequent mortality. The median defect size measured was 27% of the left ventricle at presentation to the hospital (range, 0% to 77%) and was 12% of the left ventricle at hospital discharge (range, 0% to 68%). Almost one half of the patients had a final infarct size of < or = 10%. The median amount of myocardium salvaged was 9% (range, -31% to 75%). During a median duration of follow-up of 12 months, there were 10 deaths (7 cardiac and 3 noncardiac) and 1 resuscitated out-of-hospital cardiac arrest. There was a significant association between infarct size and overall mortality (chi 2 = 8.66, P = .003) and cardiac mortality (chi 2 = 11.89, P < .001). Two-year mortality was 7% for patients whose infarct size was > or = 12% versus 0% for patients whose infarct size was < 12%. There also was a significant association between myocardium at risk and cardiac mortality (chi 2 = 6.87, P = .009). There was no association between myocardium at risk and overall mortality or between amount of myocardium salvaged and either overall mortality or cardiac mortality.

CONCLUSIONS

Larger infarct size measured by 99mTc sestamibi imaging after acute myocardial infarction is associated with increased mortality risk during short-term follow-up.

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.

Predischarge exercise radionuclide angiography in predicting multivessel coronary artery disease and subsequent cardiac events after thrombolytic therapy for acute myocardial infarction

The value of exercise testing in postinfarction patients receiving thrombolytic therapy has not been established. Ninety-four patients treated acutely with thrombolytic therapy without angioplasty who underwent exercise radionuclide angiography and coronary angiography before hospital discharge were studied. Thirty patients underwent early revascularization, often for multivessel disease. During a median follow-up period of 3.5 years, only 5 patients had "hard" events (cardiac death, cardiac arrest, or myocardial infarction) and 5 other patients underwent late (> 90 days) revascularization. The results of radionuclide angiography did not predict multivessel disease. Peak exercise ejection fraction was the only significant (p = 0.003) independent predictor of events. Among the 65 patients with a peak exercise ejection fraction > or = 40%, the 3-year hard and "combined" event-free survival were 98% and 91%, respectively. Among the 29 patients with a peak exercise ejection fraction < 40%, the 3-year hard and combined event-free survival were 74% and 69%, respectively. Postinfarction patients treated with thrombolytic therapy, who often underwent early revascularization, had an excellent prognosis through 3.5 years of follow-up. Although exercise radionuclide angiography had little value for identifying multivessel disease, a reduced peak exercise ejection fraction was associated with subsequent events.

Role of nuclear cardiology for determining management of patients with stable coronary artery disease

Both radionuclide angiography and myocardial perfusion imaging provide important insights that determine the management of patients with stable coronary artery disease. Both nuclear cardiology procedures have clearly demonstrated use in the noninvasvie identification of severe (left main or three-vessel) coronary artery disease and the noninvasive assessment of prognosis and thereby determine which patients should be sent to coronary angiography. Both radionuclide angiography and myocardial perfusion imaging provide prognostic information that is independent of resting left ventricular function and coronary anatomy and thereby influence the decision regarding which patients should be sent to coronary revascularization. This review considers the evidence supporting the uses of these nuclear cardiology procedures and provides suggestions regarding their cost-effective application.

Impaired left ventricular function, one- or two-vessel coronary artery disease, and severe ischemia: outcome with medical therapy versus revascularization

OBJECTIVE

To determine whether patients with impaired left ventricular function and one- or two-vessel coronary artery disease who manifest severe ischemia during exercise radionuclide angiography have a lower rate of subsequent cardiac events when initial management is revascularization rather than medical therapy.

DESIGN

During a median follow-up of 100 months, we compared the outcome between 37 patients who underwent a revascularization procedure and 22 who received medical therapy at the Mayo Clinic between September 1980 and December 1985.

MATERIAL AND METHODS

The revascularization therapy consisted of coronary artery bypass grafting in 31 patients and coronary angioplasty in 6. Overall survival and survival free of initial cardiac events were compared statistically for the medically and surgically treated patients.

RESULTS

Eleven deaths occurred in the patients who received medical therapy and 9 in the revascularization group. Five-year overall survival was 58% in the medically treated patients versus 84% in the revascularization group. A significant association was noted between type of treatment and overall survival (adjusted chi 2 = 6.20; P = 0.013). Twenty patients had initial cardiac events--7 in the medically treated group (3 cardiac deaths and 4 nonfatal myocardial infarctions) and 13 in the revascularization group (3 cardiac deaths, 3 out-of-hospital cardiac arrests, and 7 nonfatal myocardial infarctions). Survival free of cardiac events at 5 years was 72% in the medically treated patients and 66% in those who underwent revascularization. No association was detected between type of treatment and survival free of cardiac events.

CONCLUSION

These nonrandomized data suggest that overall survival for patients with one- or two-vessel coronary artery disease, impaired left ventricular function, and severe exercise-induced ischemia may be improved by revascularization, but the subsequent cardiac event rates are not.

Exercise testing without interruption of medication for refining the selection of mildly symptomatic patients for prognostic coronary angiography

OBJECTIVE

To examine how exercise testing on background medical treatment affects the ability of the test to predict prognostically important patterns of coronary anatomy in patients with a high clinical probability of coronary artery disease but who are well controlled on medication.

DESIGN

Prospective study.

SETTING

Regional cardiothoracic centre and referring district general hospital.

PATIENTS

84 patients with a history of typical angina or definite myocardial infarction and mild symptoms who had been placed on the waiting list for prognostic angiography.

INTERVENTION

Maximal exercise electrocardiography and radionuclide ventriculography performed off and on medication, followed by angiography within three months.

MAIN OUTCOME MEASURE

Prognostically important coronary artery disease for which early surgery might be recommended purely on prognostic grounds, irrespective of symptoms.

RESULTS

Coronary artery disease was present in 71/84 (85%) patients; in 28/84 (33%) patients this was prognostically important. When the result was strongly positive, the predictive accuracy for prognostically important disease was 0.46 off and 0.62 on medication for the exercise electrocardiogram and 0.71 off and 0.82 on medication for exercise radionuclide ventriculography. The likelihood ratio was 1.00 off and 1.36 on medication for exercise electrocardiography and 2.54 off and 10.5 on medication for exercise radionuclide ventriculography. In stepwise logistic regression, the test identified as the strongest predictor of prognostically important disease was exercise radionuclide ventriculography on medication for which the improvement chi 2 was 28 (p < 0.0001). With the regression model, the probability of important disease is 92% if exercise radionuclide ventriculography on medication is at least strongly positive, compared with 16% if the result is normal or just positive.

CONCLUSION

In patients likely to have coronary disease, exercise testing should be performed without interruption of medication to optimise its ability to identify those with prognostically important disease, and to help to avoid unnecessary or premature angiography in those who are well controlled on medical treatment.

Severe exercise-induced ischemia does not identify high risk patients with normal left ventricular function and one- or two-vessel coronary artery disease

OBJECTIVES

This study was conducted to determine whether severe exercise-induced ischemia identifies high risk patients with a normal left ventricular ejection fraction and one- or two-vessel coronary artery disease.

BACKGROUND

Severe ischemia during exercise radionuclide angiography has been shown to identify high risk patients among certain other patient subsets.

METHODS

Four hundred twenty patients with left ventricular ejection fraction > or = 50% and one- or two-vessel disease underwent exercise radionuclide angiography within 3 months of coronary angiography. Patients were treated initially with revascularization (n = 140) or medical therapy (n = 280) at the discretion of their physicians. Patients treated with revascularization were more likely to have angina by history, a positive exercise electrocardiogram, a lower exercise ejection fraction, two-vessel disease and proximal left anterior descending coronary artery disease. Two hundred sixty-four of the 280 patients given medical therapy who had complete follow-up data formed the study group. Outcome was compared between patients with (n = 56) and without (n = 208) severe exercise-induced ischemia, defined by previously published criteria (work load < or = 600 kg-m/min, ST segment depression > or = 1 mm and decrease in ejection fraction with exercise).

RESULTS

During follow-up, there were 30 initial cardiac events (12 cardiac deaths and 18 nonfatal myocardial infarctions). There was no difference in the 5-year event-free survival rate: 91% in patients with and 87% in patients without severe ischemia (p = 0.89). There was no association between event-free survival and severe ischemia (chi 2 = 1.41, p = 0.24). The study had approximately 80% power at alpha = 0.05 to detect a 25% decrease in event-free survival in the group with severe ischemia. In addition, there was no association between severe ischemia and outcome if late revascularization was included as an event or if the total mortality rate (overall survival) was analyzed.

CONCLUSIONS

Severe exercise-induced ischemia fails to identify a high risk subgroup among patients with normal left ventricular function and one- or two-vessel disease who are treated initially with medical therapy.

Prognosis of myocardial infarctions involving more than 40% of the left ventricle after acute reperfusion therapy

BACKGROUND

Prior studies based on autopsy data suggest that infarction of more than 40% of the left ventricle necessitates cardiogenic shock and death.

METHODS AND RESULTS

Technetium-99m Sestamibi tomography was used prospectively to measure infarct size at discharge in 166 patients with acute myocardial infarction. Patients with previous myocardial infarction or revascularization were excluded from the trial. Sixteen patients were identified with final infarct sizes > 40% of the left ventricle despite acute reperfusion therapy. These 16 patients (13 men) had a mean age of 63 +/- 10 years; 44% had a previous history of angina. Ten patients had emergent coronary angioplasty only (mean time to percutaneous transluminal coronary angioplasty [PTCA], 6.0 +/- 3.0 hours); 6 had thrombolysis (mean time to tissue plasminogen activator, 4.0 +/- 1.5 hours), of which 2 had rescue PTCA (5 and 3 hours from onset of pain). Of 15 patients who had angiograms after therapy, 15 had open infarct-related arteries. The left anterior descending artery was the infarct-related artery in 14 (9 proximal and 5 distal lesions). Half the patients had only single-vessel disease. Infarct size measured 50 +/- 7% of the left ventricle (range, 42% to 68%). Ejection fraction by radionuclide angiogram was 0.33 +/- 0.09 and 0.38 +/- 0.07 at discharge and 6 weeks, respectively. Hospital complications included shock (1 patient), pulmonary edema (2), angina (3), symptomatic nonsustained ventricular tachycardia (1), transient complete heart block (2), and transient bifascicular block (1). At follow-up (13 +/- 9 months), the patient with shock had died, but the remaining 15 patients were asymptomatic (1 had late PTCA for angina).

CONCLUSIONS

In the interventional and thrombolytic era, patients with large residual myocardial infarctions can survive without heart failure.

Immediate angioplasty compared with the administration of a thrombolytic agent followed by conservative treatment for myocardial infarction. The Mayo Coronary Care Unit and Catheterization Laboratory Groups

BACKGROUND

Immediate angioplasty and the administration of a thrombolytic agent followed by conservative treatment are two approaches to the management of acute myocardial infarction, but these methods have not been compared prospectively.

METHODS

We enrolled 108 patients with acute myocardial infarction in a randomized trial designed to test the hypothesis that immediate angioplasty (without previous thrombolytic therapy) may result in greater myocardial salvage than the administration of a thrombolytic agent followed by conservative treatment. The primary end point was the change in the size of the perfusion defect as assessed at admission and discharge by tomographic imaging with technetium-99m sestamibi, a myocardial perfusion agent that can measure myocardium at risk and final infarct size.

RESULTS

End-point data were available for 56 patients randomly assigned to receive tissue plasminogen activator (mean [+/- SD] time to start of infusion, 232 +/- 174 minutes after the onset of chest pain) and 47 patients randomly assigned to receive angioplasty (first balloon inflation at 277 +/- 144 minutes). In the case of anterior infarction, myocardial salvage as assessed by imaging with technetium-99m sestamibi was 27 +/- 21 percent of the left ventricle for 22 patients in the thrombolysis group, as compared with 31 +/- 21 percent for 15 patients in the angioplasty group. For infarcts in all other locations, myocardial salvage was 7 +/- 13 percent for 34 patients in the thrombolysis group and 5 +/- 10 percent for 32 patients in the angioplasty group. After adjustment for infarct location, the difference in mean salvage between groups was 0 (P = 0.98), with a 95 percent confidence interval of +/- 6 percent of the left ventricle.

CONCLUSIONS

In patients with acute myocardial infarction, immediate angioplasty does not appear to result in greater myocardial salvage than the administration of a thrombolytic agent followed by conservative treatment, although a small difference between these two therapeutic approaches cannot be excluded.

The treadmill exercise score revisited: coronary arteriographic and thallium perfusion correlates

The treadmill exercise score has been used to stratify patients into low-, moderate-, and high-risk groups. This score is derived from ST segment depression, angina, and exercise duration. To determine the coronary arteriographic and exercise thallium perfusion correlates of the score, we examined the extent of coronary artery disease and exercise single photon emission computed thallium-201 results in 834 patients for whom cardiac catheterization data were available. Of those, 174 had no coronary artery disease, 195 had one-vessel, 246 had two-vessel, and 219 had three-vessel disease. Based on the treadmill exercise score, 369 were in the low-risk, 384 in the moderate-risk, and 81 in the high-risk group. The extent of coronary artery disease was 2.1 +/- 1 diseased vessels in the high-risk, 1.7 +/- 1 in the moderate, and 1.4 +/- 1.1 in the low-risk group (p < 0.01). The extent of the thallium abnormality (maximum number of abnormal segments 120/patient) was 10 +/- 6 in the high-risk, 7 +/- 6 in the moderate, and 6 +/- 5 in the low-risk group (p < 0.05). Based on the extent of coronary artery disease and results of thallium imaging, patients were reclassified into three groups: group 1 had three-vessel disease and/or > or = 10 abnormal segments (n = 387), group 3 had no coronary artery disease or one-vessel disease and less than five abnormal segments (n = 212), and the remaining patients were in group 2 (n = 235).(ABSTRACT TRUNCATED AT 250 WORDS)

Noninvasive identification of severe coronary artery disease using exercise tomographic thallium-201 imaging

The ability of exercise thallium-201 tomographic imaging to predict the presence of left main or 3-vessel coronary artery disease (CAD) was examined in 688 patients who underwent both exercise thallium-201 testing and coronary angiography. Significant differences existed for multiple variables between patients with (n = 196) and without (n = 492) severe left main or 3-vessel CAD. Logistic regression analysis identified 4 variables as independently predictive of left main or 3-vessel CAD. These variables were the magnitude of ST-segment depression with exercise, the number of visually abnormal short-axis thallium-201 segments, the presence or absence of diabetes mellitus, and the change in systolic blood pressure with exercise. Using these variables, patients were classified by nomograms into low-, intermediate- and high-probability groups. Patients at high probability (n = 205) had a 52% prevalence of 3-vessel or left main CAD, whereas those at low probability (n = 170) had only a 12% prevalence. Only 53 patients (29%) with 3-vessel or left main CAD had perfusion abnormalities in all 3 coronary territories. Clinical and exercise parameters provide important independent information in the identification of left main or 3-vessel CAD by exercise thallium-201 tomographic imaging, because thallium scintigraphy alone is suggestive of extensive CAD in few patients.

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)

Effects of the dipyridamole test on left ventricular function in coronary artery disease

The dipyridamole stress test is used with thallium-201 to detect areas of inhomogeneity of blood flow that point to coronary artery disease (CAD). It is unclear whether dipyridamole produces inhomogeneous perfusion only or whether it actually decreases net flow in the obstructed vessels and produces true ischemia. It is also unclear what effect dipyridamole has on global and segmental left ventricular function. Therefore, ejection fraction, segmental wall motion and ventricular volume equivalents were measured before and after dipyridamole in 113 patients and 32 normal subjects. Ejection fraction responded in an abnormal fashion in 98 patients (87%), decreasing from 49 +/- 11% to 43 +/- 13% (p less than 0.0001), whereas it increased in 29 normal subjects (90%) from 57 +/- 6% to 64 +/- 10% (p less than 0.0001). Wall motion worsened distinctly in 75 patients (66%), and pressure/volume ratio deteriorated in 72%. The effect of dipyridamole lasted between 10 and 25 minutes, but was promptly reversed by aminophylline. These findings indicate that dipyridamole generally induces true ischemia in CAD. Furthermore, the degree of dysfunction is related to the angiographically assessed severity of CAD. The shortness of breath (seen in 10% of patients) may be partially explained by the findings, and it seems advisable to give aminophylline to every patient in order to promptly correct left ventricular dysfunction.

Circadian rhythm of white blood cell aggregation and free radical status in healthy volunteers

Previous studies have demonstrated circadian rhythms in the onset of thrombotic events, which occur most commonly in the morning, and also in the fibrinolytic activity of the blood which has a peak in the evening and a trough in the morning. There has recently been increasing interest in the role of white blood cells (WBCs) and free radicals (FRs) in thrombosis. No one has yet investigated the potential circadian variation of WBC aggregation and FRs in humans. We studied the circadian rhythm of WBC aggregation and FR status in 10 healthy male volunteers. Six blood samples were collected at 4 hourly intervals from 12:00 (mid-day) until 08:00 the following morning. The volunteers carried out normal daily activities until 00:00 at which time they went to bed and they remained in bed until 08:00. The following were measured on each sample: WBC aggregation; thiobarbituric acid reactive substances (TBARs), plasma thiols (PSH), red cell lysate thiols (LSH), glutathione (GSH) and superoxide dismutase (SOD) which are all altered in the presence of FR activity. The following parameters demonstrated significant circadian rhythms, WBC aggregation p less than 0.001, TBARs p less than 0.015, PSH p less than 0.001, LSH p less than 0.002. WBC aggregation was lowest at 09:00 and highest at 00:00-04:00. TBARs and PSH both had a peak at 16:00 and a trough at 04:00. LSH had a peak at 12:00 and a trough at 08:00. As the behaviour of WBCs and FR status influence the flow properties of blood, a circadian rhythm in WBC function and FR status may contribute to the time of onset of thrombotic diseases. Moreover, with many studies being currently undertaken in this area, our work indicates the need to standardize sample times.

Correlation between resting ST segment depression, exercise testing, coronary angiography, and long-term prognosis

Resting ST segment depression has been identified as a marker for adverse cardiac events in patients with and without known coronary artery disease. To correlate this with exercise testing, coronary angiography, and how it impacts on long-term prognosis, a retrospective study was performed on 476 patients, of whom 223 had no clinical or electrocardiographic evidence of prior myocardial infarction while 253 were survivors of an infarction. All patients performed a standard exercise test and underwent diagnostic coronary angiography within an average of 32 days of their exercise test (range 0 to 90 days). Exclusions were women, those with left bundle branch block, left ventricular hypertrophy, use of digoxin, previous revascularization procedures, or significant valvular or congenital heart disease. Long-term follow-up was carried out for an average of 45 months (+/- 17). Of the patients without prior infarction, 23 (10%) had persistent resting ST segment depression, and of those with a prior history of infarction, 37 (15%) also had resting ST segment depression. Patients with resting ST segment depression and no prior myocardial infarction had a higher prevalence of severe coronary disease (three-vessel and/or left main) (30%) than those without resting ST segment depression (16%) (95% confidence interval [CI] for observed difference -5.0% to 33.9%, p = 0.12). The criterion of greater than or equal to 2 mm of additional exercise-induced ST segment depression was a particularly useful marker in these patients for the diagnosis of any coronary disease (likelihood ratio 3.35, 95% CI 0.56 to 19.93, p = 0.06). Patients with resting ST segment depression and a prior myocardial infarction had a 2.5 times higher prevalence of severe coronary artery disease compared with patients without resting ST segment depression (43% versus 17% prevalence, respectively, 95% CI for observed difference 9.38% to 42.8%, p less than 0.001) and also had larger left ventricles postinfarction (left ventricular end-diastolic volume index 102 ml/m2 compared with 96 ml/m2, p less than 0.001).(ABSTRACT TRUNCATED AT 400 WORDS)

Identification of "surgical" coronary anatomy by exercise radionuclide cineangiography

Radionuclide cineangiography with exercise has been used to identify patients with coronary arteriographic patterns for which bypass grafting has been shown to prolong life. However, patients with severe prior myocardial damage were included in these studies, although the randomized medicine versus surgery trials recognized an effect of resting ejection fraction on operative risk and excluded patients with severely compromised function. Moreover, continuing reports from trials of surgery and from an ancillary evaluation of angioplasty have refined the set of coronary anatomic patterns for which mechanical therapy prolongs life, although stenosis severity criteria varied (50 vs 70 to 75%) between these trials. In this study, we have focused on patients who would have been eligible for the randomized trials of surgical therapy, and included only those with at least moderately preserved ventricular function at rest (ejection fraction greater than or equal to 30%). In such patients, exercise parameters were significantly more accurate than rest variables in identifying all anatomic patterns appropriately treated mechanically; logistic regression selected ejection fraction change with exercise, followed by systolic blood pressure change with exercise, as the 2 most powerful independent covariates among patients with "surgical" coronary anatomy defined by a 70% stenosis criterion; absolute exercise ejection fraction contributed no significant independent information. When defined at a 50% stenosis severity level, blood pressure change and angina class were more powerful than absolute exercise ejection fraction, but a crude, noninvasively determined analog of stroke work, incorporating change in both ejection fraction and blood pressure, was most accurate.(ABSTRACT TRUNCATED AT 250 WORDS)

Relation of left ventricular volume and function over one year after acute myocardial infarction to infarct size determined by technetium-99m sestamibi

Twenty patients with a first acute myocardial infarction (AMI) (15 anterior, 5 inferior) who received successful reperfusion therapy underwent tomographic imaging with technetium-99m (Tc-99m) sestamibi and radionuclide ventriculography at discharge, 6 weeks, and 1 year after AMI. Patency of the infarct-related artery after reperfusion (thrombolysis, 8 patients; coronary angioplasty, 12 patients) was confirmed by angiogrpahy in all patients. Tc-99m sestamibi perfusion defect at discharge (a measure of infarct size) was quantitated using previous methods and expressed as a percentage of the left ventricle (28 +/- 19%, range 0 to 59%). This perfusion defect size correlated closely with ejection fraction at discharge (r = -0.87), 6 weeks (r = -0.81) and at 1 year (r = -0.78, all p less than 0.0001). Perfusion defect size at discharge also correlated closely with end-systolic volume index at discharge (r = 0.71, p less than 0.0005), 6 weeks (r = 0.63, p less than 0.005) and at 1 year (r = 0.76, p less than 0.0001). Perfusion defect size at discharge did not correlate significantly with end-diastolic volume index at discharge or at 6 weeks, but did correlate at 1 year (r = 0.66, p less than 0.005). There was no significant group change in end-systolic or end-diastolic volume indexes from discharge to 1 year later, although 7 patients had definite individual changes in end-diastolic volume index (3 increased and 4 decreased). There was no relation between defect size and late changes in end-systolic volume index, but there was a weak correlation between defect size and late changes in end-diastolic volume index (r = 0.42, p = 0.07).(ABSTRACT TRUNCATED AT 250 WORDS)

Effect of infarct location on myocardial salvage assessed by technetium-99m isonitrile

To investigate the influence of infarct location on myocardial salvage, technetium-99m isonitrile was injected into 43 patients with a first myocardial infarction before early reperfusion therapy. Primary coronary angioplasty was performed in 22 patients and successful intravenous thrombolytic therapy was given to 15 patients, both within 6 h of the onset of chest pain. Patency of the infarct-related artery was confirmed by angiography in all 37 patients. In the remaining six patients (three with and three without early thrombolytic therapy) the infarct-related artery remained occluded. Single photon emission computed tomography was performed within 6 h of the administration of technetium-99m isonitrile and repeated at the time of hospital discharge. Radionuclide ejection fraction at discharge was significantly lower for patients with anterior infarction (0.41 +/- 0.12) than for those with inferior infarction (0.56 +/- 0.09, p less than 0.001). Early perfusion defect size, a measure of myocardium at risk, was greater in patients with anterior than in those with inferior infarction (52 +/- 9% vs. 18 +/- 10% of the left ventricle, p = 0.0001) as was final defect size (30 +/- 20% vs. 9 +/- 8%, p less than 0.01). The change in myocardial perfusion, an estimate of myocardial salvage, was also greater in patients with anterior infarction (24 +/- 16% vs. 10 +/- 7%, p less than 0.01). However, the proportion of jeopardized myocardium salvaged (salvage index) was not significantly different between patients with anterior or inferior infarction (0.49 +/- 0.34 vs. 0.59 +/- 0.35, p = NS).(ABSTRACT TRUNCATED AT 250 WORDS)

Degree of coronary artery disease predicted by exercise testing

The ability of exercise testing to predict the extent of coronary artery disease was examined in 268 male patients undergoing both coronary angiography and bicycle testing with electrocardiography before coronary artery bypass surgery. When maximal ST-depressions limited by symptoms increased from 0 to 4 mm or more, the percentage of patients with 'serious' coronary disease, defined as either triple vessel disease or left main stem stenosis, increased from 50% to 80% (P = 0.0001). The patients in the lowest third of physical work capacity showed only a slightly increased risk of serious disease. This tendency was abolished in patients who were using beta-blockers, whereas the relationship between ST-depression and disease was not affected by this medication. The probability of finding left main stem stenosis in a patient increased from 5 to 30% with increasing ST-depression: beta-blockers did not affect this relationship, but there was no additional predictive effect of implicating the level of physical work capacity. It is concluded that traditional electrocardiography during exercise is of value when selecting patients for angiography, but that the physical work level obtained during the test does not predict the degree of coronary pathology.

Capabilities of supine exercise electrocardiography versus exercise radionuclide angiography in predicting coronary events

The ability of supine exercise electrocardiography and exercise radionuclide angiography to predict time to subsequent cardiac events (cardiac death, nonfatal myocardial infarction or late coronary bypass grafting or angioplasty) were compared in 265 patients with normal resting electrocardiograms who were not taking digoxin. All patients had undergone coronary catheterization and were initially treated medically. Follow-up study was performed at a median of 51 months. Separate logistic regression models, which had been previously developed to predict 3-vessel or left main coronary artery disease (CAD), were compared using a Cox regression analysis to predict time to a subsequent cardiac event. The exercise electrocardiography model, consisting of the magnitude of ST depression, exercise heart rate and patient gender, was a powerful predictor (chi-square = 30.8, p less than 0.0001) of subsequent events. The exercise radionuclide angiography model, which included the exercise response of the pressure-volume ratio in addition to the exercise electrocardiography variables, had similar prognostic power (chi-square = 31.8, p less than 0.0001). In a separate analysis considering only cardiac death and nonfatal myocardial infarction, the exercise electrocardiography model remained a significant predictor of events (chi-square = 12.2, p less than 0.001). None of the radionuclide angiography variables added significantly to the prognostic power of the exercise electrocardiography model. Thus, in patients with a normal resting electrocardiogram who are not taking digoxin, the supine exercise electrocardiography model that predicts 3-vessel or left main CAD also predicts future cardiac events. Exercise radionuclide angiography does not provide any additional prognostic information in such patients.

Primary angioplasty in myocardial infarction: assessment of improved myocardial perfusion with technetium-99m isonitrile

Technetium-99m-hexakis-2-methoxy-2-isobutyl-isonitrile (technetium-99m isonitrile) is a new radiopharmaceutical compound that reflects myocardial perfusion. Its kinetics, especially its lack of redistribution after intravenous administration, permits the assessment of changes in myocardial perfusion without delay of therapy. Tomographic images at rest were obtained immediately and 6 to 10 days later in 17 consecutive patients undergoing successful primary angioplasty during their first transmural myocardial infarction. Thirteen patients had anterior infarction. The initial (acute) defect size before angioplasty of 48 +/- 17% of the left ventricle decreased significantly (p less than 0.0001) to 29 +/- 19% on the late scans. There was no correlation between the time to therapy and the reduction in defect size. Twelve of the 17 patients, including 7 of the 11 patients treated after 4 h, demonstrated a definite reduction in the initial defect size. Eight patients with angiographically proved persistent coronary occlusion underwent a similar imaging sequence. The initial defect size in this group remained unchanged on the late scans (24 +/- 16% versus 26 +/- 18%, p = NS). Primary angioplasty is an effective approach toward salvaging myocardium; comparison with thrombolytic drug therapy must await the results of controlled clinical trials.

Interpreting results of exercise studies after acute myocardial infarction altered by thrombolytic therapy, coronary angioplasty or bypass

Numerous studies have assessed the ability of exercise modalities to predict patient outcome after acute myocardial infarction (AMI). Implicit in the use of these prior data to assess the prognosis of patients currently undergoing exercise studies is the assumption that patients selected for exercise assessment are similar over time and that the data generated in the past are therefore applicable to the current patient populations. This study retrospectively assessed the clinical, exercise, and rest and exercise radionuclide angiographic data in 791 consecutive patients referred for exercise radionuclide angiography within 1 month after AMI during a 5-year period to determine if the clinical and exercise characteristics of patients referred for exercise evaluation after infarction have changed significantly over time. Most parameters examined demonstrated significant increasing trends, including thrombolytic therapy at the time of AMI, revascularization procedure between AMI and exercise assessment, age, beta-blocker usage, Q-wave AMI, inferior infarction, exercise double product, exercise capacity, significant ST-segment depression with exercise, peak ejection fraction, and change in ejection fraction with exercise. These data indicate that the characteristics of patients selected to undergo exercise after AMI in a large referral center have changed significantly over time. If these data are applicable to other referral centers and to other exercise testing modalities, previously published results regarding exercise assessment after AMI will need to be reconfirmed in patients currently selected for testing, since these results may no longer be applicable in this current era of aggressive medical and interventional management.

Assessment of stable ischemic heart disease. Which tests are best for which patients?

An understanding of the importance of various risk factors, the pathogenesis of myocardial ischemia, and the appropriate use of various noninvasive and invasive tests is essential for management of patients with known or suspected coronary artery disease (CAD). Although coronary angiography remains the "gold standard" for diagnosis of CAD, much of the data obtained from risk factor assessment, medical history, and various noninvasive tests provides information that may be even more important than cardiac catheterization data alone for defining prognosis and directing management.

Comparison of exercise performance in left main and three-vessel coronary artery disease

From a consecutive series of patients who underwent rest and exercise radionuclide angiography over several years, we retrospectively identified 34 patients with left main coronary artery disease and 103 patients with three-vessel coronary artery disease who did not have significant left main disease. The results of gated equilibrium radionuclide angiography were compared in these 2 groups. Multiple exercise hemodynamic, exercise electrocardiographic, and exercise radionuclide angiographic parameters were considered in an attempt to separate the 2 groups. The only parameter that was significantly different between the 2 groups was exercise heart rate. However, no value of the exercise heart rate could meaningfully separate the 2 groups. Despite their known difference in prognosis, patients with left main and three-vessel disease had very similar exercise performance and could not be distinguished from one another by exercise electrocardiography or exercise radionuclide angiography. The inability to distinguish these two groups is a clear limitation of noninvasive exercise modalities.

Optimal interpretation of the supine exercise electrocardiogram in patients with right bundle branch block

A detailed analysis of the exercise ECG was performed in 82 patients with right bundle branch block who underwent supine exercise equilibrium radionuclide angiography. The sensitivity and specificity of each individual electrocardiographic lead for the detection of a positive radionuclide angiogram was determined. Leads V5 and V6 had a sensitivity of 58 percent and a specificity of 89 percent. The limb leads and lead V4 had a lower sensitivity, but an equivalent specificity. Leads V1 and V3 each had a clearly lower specificity that ranged from 56 to 67 percent. Receiver operating characteristic curve analysis demonstrated that the optimal interpretation of the exercise ECG included the limb leads and V4 to V6, but not V1 to V3. The results of coronary angiography in the subset of 16 patients who underwent this procedure confirmed these findings.

Mismatch of left ventricular function and infarct size demonstrated by technetium-99m isonitrile imaging after reperfusion therapy for acute myocardial infarction: identification of myocardial stunning and hyperkinesia

Quantitation of perfusion defect size using tomographic imaging with technetium-99m-hexakis-2-methoxy isobutyl isonitrile was performed at the time of hospital discharge in 32 patients with a first myocardial infarction who underwent successful coronary reperfusion within 8 h of the onset of chest pain. Reperfusion was accomplished with thrombolysis or primary coronary angioplasty. Radionuclide angiography was performed at discharge and 6 weeks later. There was a close correlation between perfusion defect size and values for ejection fraction and regional wall motion both at discharge (r = -0.80 and -0.75, respectively) and 6 weeks later (r = -0.81 and -0.81, respectively). There was no overall group difference in ejection fraction between the value at discharge and at 6 weeks; however, five patients had a significant increase (greater than or equal to 0.08) and six had a significant decrease (greater than or equal to 0.08) in ejection fraction. In patients with a significant increase at 6 weeks, ejection fraction was significantly lower at discharge than the value predicted from perfusion defect size (0.37 +/- 0.09 measured versus 0.47 +/- 0.13 predicted, p less than 0.05) and it improved at 6 weeks to near predicted values (0.51 +/- 0.07). In patients with a significant decrease at 6 weeks, ejection fraction was significantly higher at discharge than the value predicted from perfusion defect size (0.60 +/- 0.10 measured versus 0.50 +/- 0.10 predicted, p less than 0.05) and it decreased at 6 weeks to near predicted levels (0.51 +/- 0.09). Left ventricular ejection fraction at the time of hospital discharge is a potentially misleading index of the efficacy of reperfusion therapy for myocardial infarction. In a significant minority (34%) of patients this index does not accurately reflect perfusion defect size, apparently because of the effects of myocardial stunning and compensatory hyperkinesia.

Circadian variation of heart rate is affected by environment: a study of continuous electrocardiographic monitoring in members of a symphony orchestra

Twenty four hour ambulatory ST segment monitoring was performed on 48 members (43 players and five members of the management/technical team) of the British Broadcasting Corporation (BBC) symphony orchestra without a history of cardiac disease. This period included final rehearsals and live performances (for audience and radio) of music by Richard Strauss and Mozart at the Royal Festival Hall (n = 36) and Rachmaninov and Tchaikovsky at the Barbican Arts Centre (n = 21). During the period of monitoring one person (2%) had transient ST segment changes. Mean heart rates were significantly higher during the live performances than during the rehearsals. Mean heart rates during the live performance of Rachmaninov and Tchaikovsky were significantly higher than during Strauss and Mozart in those (n = 6) who were monitored on both occasions. Mean heart rates in the management and technical team were higher than those of the players. The recognised circadian pattern of heart rate, with a peak in the morning waking hours, was altered similarly during both concert days, with a primary peak occurring in the evening hours and a lesser peak in the morning for both musicians and management/technical staff. This study showed that environmental factors are of primary importance in defining the circadian pattern of heart rate. This has important implications when identifying peak periods of cardiovascular stress and tailoring drug treatment for patients with angina pectoris.

Prognostic value of radionuclide angiography in medically treated patients with coronary artery disease. A comparison with clinical and catheterization variables

To evaluate the usefulness of multiple measures from rest and exercise radionuclide angiography (RNA) in predicting cardiovascular death and cardiovascular events (death or nonfatal myocardial infarction) and to assess the prognostic usefulness of the RNA relative to clinical and catheterization data, we studied 571 stable patients with symptomatic coronary artery disease who had upright rest/exercise first-pass RNA within 3 months of catheterization and were medically treated. With a median follow-up of 5.4 years, 90 patients have died from cardiovascular causes, and 147 patients have either died or suffered a nonfatal myocardial infarction. Using the Cox regression model and a preselected group of RNA variables, the most important RNA predictor of mortality was exercise ejection fraction (chi 2 = 81, p less than 0.00001). Neither rest ejection fraction nor the change in ejection fraction from rest to exercise contributed additional predictive information. Two other RNA study variables, the change in heart rate from rest to exercise and rest end-diastolic volume index, did contribute additional prognostic information to the exercise ejection fraction (chi 2 = 23, p less than 0.0001). Compared with noninvasive clinical data (history, physical examination, electrocardiogram, and chest radiograph), RNA variables were considerably more predictive of mortality (chi 2 = 71 [clinical variables] versus chi 2 = 104 [RNA]). Remarkably, the strength of the relation of RNA variables with mortality was equivalent to that of the set of catheterization variables previously demonstrated in our large angiographic population to be prognostically important (chi 2 = 104 [RNA] versus chi 2 = 102 [catheterization variables]). The RNA contained 84% of the information provided by clinical and catheterization descriptors combined. Furthermore, the RNA contributed significant additional prognostic information to the clinical and catheterization data (chi 2 = 13.6, p = 0.0035). For cardiovascular events, the relative prognostic usefulness of the RNA was similar, although relations with this outcome were generally weaker. Descriptors from the rest/exercise RNA exhibit a powerful relation with long-term outcomes and can be useful in defining risk, even when clinical and catheterization data are available.

The divergent recovery of ST-segment depression and radionuclide angiographic indicators of myocardial ischemia

This study evaluated the recovery after exercise of both ST-segment depression on the exercise electrocardiogram (electrical evidence of ischemia) and exercise-induced abnormalities in wall motion or ejection fraction as detected by radionuclide angiography. The study group of 31 patients was selected to undergo prolonged electrocardiographic and radionuclide imaging after exercise because they had persistent ST-segment depression greater than 3 minutes after exercise and radionuclide angiographic evidence of ischemia at peak exercise. In 27 (87%) of the 31 patients, radionuclide evidence of ischemia recovered more quickly than the electrocardiogram. Only 15 of the 31 patients had exercise-induced radionuclide abnormalities after exercise. Compared with the 16 patients without such findings of ischemia after exercise, these 15 patients had a worse wall motion score at peak exercise (5.3 vs 3.9; p less than 0.01) and a smaller increase in systolic blood pressure with exercise (p less than 0.05) and after exercise (p less than 0.01). Radionuclide angiographic evidence of ischemia recovers more quickly after exercise than ST-segment depression. When there is radionuclide evidence of ischemia after exercise, it is associated with more severe ischemia during exercise.

Prevention of late ventricular dilatation after acute myocardial infarction by successful thrombolytic reperfusion

To examine the sequential changes in left ventricular volume after thrombolytic therapy for acute myocardial infarction, gated radionuclide ventriculography was performed within 12 hours of thrombolysis and at 1 and 6 weeks in 34 consecutive patients who received intravenous thrombolytic therapy in the Thrombolysis in Myocardial Infarction Trial. Angiographic confirmation of immediate reperfusion (mean 5.6 hours after onset of symptoms) that persisted at 24 hours was noted in 24 patients; 10 patients were not reperfused. A small (9.5%), but significant (p = 0.05), increase in end-diastolic volume index was noted in the reperfused group between 1 and 6 weeks; however, a marked degree of dilatation (35%) was noted in the non-reperfused group (p = 0.01). The change in left ventricular volume between 1 and 6 weeks differed in the 2 groups for both end-diastolic volume index and end-systolic volume index (p = 0.01 and p = 0.02, respectively). By 6 weeks, both end-diastolic volume index and end-systolic volume index were greater in the nonreperfused group (p less than 0.05). Between the acute and 6-week studies, definite increases in end-diastolic volume index (p less than 0.05) and end-systolic volume index (p less than 0.01) occurred commonly in the nonreperfused group but rarely in the reperfused group. Compared to the nonreperfused group, the reperfused group also had significantly higher ejection fractions at both 1 and 6 weeks (p less than 0.05). The change in end-diastolic volume index between 1 and 6 weeks correlated significantly and inversely with the ejection fraction at 1 week (r = -0.60, p less than 0.001).(ABSTRACT TRUNCATED AT 250 WORDS)

Risk stratification of single or double vessel coronary artery disease and impaired left ventricular function using exercise radionuclide angiography

Patients with 3-vessel coronary artery disease (CAD) and normal left ventricular (LV) function have a worse prognosis if they manifest ischemia during exercise testing. The present study determines if exercise radionuclide angiography can aid in the risk stratification of patients with 1- or 2-vessel CAD and impaired LV function (ejection fraction less than 50%). Sixty-five consecutive patients with these findings were followed for a median duration of 24 months (range 12 to 49). Eleven of the 65 patients (17%) had severely ischemic exercise radionuclide angiograms, defined as: a decrease in ejection fraction with exercise; greater than or equal to 1.0 mm of ST-segment depression; and peak exercise workload less than or equal to 600 kg-m/min. During follow-up 11 patients had initial significant cardiac events: 4 cardiac deaths, 1 cardiac arrest, 4 myocardial infarctions and 2 bypass or angioplasty procedures for unstable angina greater than or equal to 3 months after the exercise study. Four of 11 patients (36%) with severely ischemic exercise radionuclide angiograms had events, compared to 7 of 54 patients (13%) without ischemic radionuclide angiograms. Event-free survival at 18 months was 73% for patients with severe exercise ischemia versus 92% for those without ischemia (p less than 0.05). Univariate analysis showed that severe ischemia on radionuclide angiography was the only variable of several tested that significantly predicted future cardiac events (chi-square = 8.16, p less than 0.005). Among patients with 1- or 2-vessel CAD and impaired resting LV function, severe ischemia on exercise radionuclide angiography identifies a subgroup at high risk for future cardiac events.

Stable angina pectoris: 2. Cardiac evaluation and diagnostic testing

The examination of a patient with angina pectoris begins with clinical assessment. Certain clinical findings that are present only during angina, such as mitral regurgitation due to ischemia-induced papillary muscle dysfunction, may clarify an otherwise uncertain diagnosis. Electrocardiography is a useful and relatively inexpensive test for detecting evidence of ischemia in patients with suspected angina. The presence of cardiomegaly on the chest roentgenogram has adverse prognostic implications. Exercise stress testing is important in the diagnosis of coronary artery disease and also provides prognostic information. Patients should be classified into high-, intermediate-, or low-risk subsets by noninvasive techniques. Although relatively easy and inexpensive, treadmill exercise stress testing cannot be performed in all patients, and sometimes it will yield equivocal results. In these cases, radionuclide testing (with thallium scintigraphy or radionuclide angiography) can be helpful and also can identify high-risk patients. Some patients will require coronary angiography.