The prognostic value of submaximal exercise testing with radionuclide ventriculography before hospital discharge in patients with recent myocardial infarction

Ethnic differences in the cardiac responses to aerobic exercise

Background: Cardiovascular disease disproportionately affects North American Indigenous populations. Ethnic differences in cardiac responses to exercise are known, though Indigenous populations response is unknown. To evaluate cardiac responses to aerobic exercise among Canadian Indigenous and European adults. Methods: Indigenous (N = 12, 4 females, 1 male incomplete) and European (N = 12, all completed) Canadian age and sex-matched adults 19-40 years and free of cardiovascular disease or diabetes completed a cycle ergometer maximal aerobic power test and 30 min at 60% maximal aerobic capacity on two separate days. Echocardiographic assessments preceded and immediately followed exercise. Results: Responses to maximal exercise were similar among ethnicities including decreases in stroke volume index, cardiac output index and ejection fraction, and increases in arterial-ventricular coupling. However, following submaximal exercise, only Indigenous adults demonstrated reductions in end systolic volume, end diastolic volume (154.8 ± 40.6 mL to 136.5 ± 33.0 mL, p = 0.01, vs. 149.4 ± 22.4 mL to 147.1 ± 27.0 mL; p = 0.81), stroke volume index (44.9 ± 8.7 mL m^-2 to 38.0 ± 6.5 mL m^-2, p = 0.002, vs. 46.4 ± 7.1 mL m^-2 to 44.0 ± 6.5 mL m^-2; p = 0.28) and arterial compliance. Conclusion: Indigenous and European adults demonstrated similar cardiac responses to maximal exercise, though only Indigenous adults demonstrated cardiac responses to submaximal exercise.

Clinical value of hyperemic left ventricular systolic function in vasodilator stress testing

Exercise results in increased left ventricular contractility in normal individuals. Similar changes can also be seen with vasodilator stress. This article discusses the physiologic basis of these changes as well as reviews the clinical data supporting the use of these parameters for diagnostic and prognostic evaluation. Methodologic limitations as well as other concomitant pathologic processes which may confound interpretation of stress-induced changes in LVEF are also reviewed.

Resting measures and physiological responses to exercise for the determination of prognosis in patients with chronic heart failure: useful tools for clinical decision-making

Despite recent advances in the management of chronic heart failure (CHF), the prognosis of many of these patients remains dire. The need for an accurate prognosis in these patients has led to the identification of several indicators purported to represent the impact of the disease. Such indicators often are obtained at rest and are not always accurate at determining the clinical status of CHF patients. As a result, the relationship between prognostic indicators and clinical outcomes is frequently weak. On the other hand, physiological responses to acute exercise may unmask patients with the worst clinical status and identify those at increased risk of poor outcomes. Therefore, the present review appraises the value of several prognostic indicators for patients with CHF collected at rest and in response to exercise. In particular, it contrasts the value and accuracy of predictors of mortality widely used in clinical settings, such as oxygen uptake, ventilatory efficiency, and left ventricular ejection fraction, with new and more direct indicators of ventricular systolic and diastolic function.

Prognostic value of predischarge radionuclide ventriculography at rest and exercise after acute myocardial infarction treated with thrombolytic therapy or primary coronary angioplasty. The Zwolle Myocardial Infarction Study Group

BACKGROUND

Previous studies have demonstrated the prognostic value of radionuclide ventriculography at rest and exercise in patients post myocardial infarction (MI). The number of studies in patients treated with modern reperfusion techniques, including thrombolysis or primary angioplasty, however, is limited.

HYPOTHESIS

The aim of this study was to evaluate the prognostic significance of predischarge radionuclide ventriculography at rest and exercise in patients with acute MI treated with thrombolysis or primary angioplasty.

METHODS

A total of 272 consecutive patients with acute MI who were randomized to thrombolysis or primary coronary angioplasty underwent predischarge resting and exercise radionuclide ventriculography. Left ventricular ejection fraction at rest, decrease in ejection fraction during exercise > 5 units below the resting value, angina pectoris, ST-segment depression, and exercise test ineligibility were related to subsequent cardiac events (cardiac death, nonfatal reinfarction) during follow-up.

RESULTS

During a mean follow-up of 30 +/- 10 months, cardiac death occurred in 11 (4%) patients and nonfatal reinfarction in 14 (5%) patients. Resting left ventricular ejection fraction was the major risk factor for cardiac death. In patients with an ejection fraction < 40%, cardiac death occurred in 16% compared with 2% in those with an ejection fraction > or = 40% (p = 0.0004). In addition, cardiac death tended to be higher in patients ineligible than in those eligible for exercise testing (11 vs. 3%, p = 0.08). None of the other exercise variables (decrease in ejection fraction during exercise > 5 units below the resting value, angina pectoris or ST-segment depression) were predictive for cardiac death. When all exercise test variables in each patient were combined and expressed as a risk score, a low risk (n = 185) and a higher risk (n = 87) group of patients could be identified, with cardiac death occurring in 1 and 10%, respectively. As the predictive accuracy of a negative test was high, radionuclide ventriculography was of particular value in identifying patients at low risk for cardiac death. Radionuclide ventriculography was not able to predict recurrent nonfatal MI.

CONCLUSION

In patients with MI treated with thrombolysis or primary angioplasty, radionuclide ventriculography may be helpful in identifying patients at low risk for subsequent cardiac death. In this respect, left ventricular ejection fraction at rest was the major determinant. Variables reflecting residual myocardial ischemia were of limited prognostic value. Identification of a large number of patients at low risk allows selective use of medical resources during follow-up in this subgroup and has significant implications for the cost effectiveness of reperfusion therapies.

Assessment of left ventricular function: comparison of cardiac multidetector-row computed tomography with two-dimension standard echocardiography for assessment of left ventricular function

OBJECTIVE

To compare global Left Ventricular (LV) systolic function assessment by 16-detector row Computed Tomography (MDCT) with Two-Dimensional Standard Echocardiography (2DSE) in a routine cardiology practice setting and to ascertain the degree of correlation between LV volumes and measurements obtained by 2DSE with those measured by MDCT.

METHODS

In 52 patients with suspected coronary artery disease, a contrast enhanced MDCT study was performed using retrospective gating without dose modulation for better endocardial delineation. Eight phases of the cardiac cycle were analyzed to identify the end-diastolic and end-systolic phases. 2DSE was performed on the same day. Left ventricular systolic and diastolic volumes and ejection fraction were calculated in 4-chamber, 2-chamber and biplane (average of the two) views. Endocardial tracing was used to measure ventricular volumes by area length method for CT and Simpson's method for echocardiography.

RESULTS

On MDCT, mean LV ejection fraction (LVEF) in 4-chamber, 2-chamber and biplane views were 58.4 +/- 12, 59.3 +/- 12 and 59.7 +/- 12% respectively. On 2DSE, mean LVEF in 4-chamber, 2-chamber and biplane views were 58 +/- 14, 57 +/- 16 and 58 +/- 13% respectively. LVEF correlated best using the biplane views (r = 0.59 and P < 0.01) compared to 2-chamber (r = 0.57 and P < 0.01) and 4-chamber views (r = 0.32 and P = 0.02). Biplane measurement by these two techniques correlated well for LV volumes in both diastole (r = 0.69 and P < 0.01) and systole (r = 0.73 and P < 0.01), although MDCT consistently gave higher values.

CONCLUSIONS

MDCT can be a useful tool to measure LVEF while patients are undergoing CT coronary angiography.

Prognostic value of stress myocardial perfusion imaging in patients with mildly impaired systolic left ventricular function or left ventricular asynergy without chest pain but with suspected coronary artery disease

BACKGROUND

The prognostic value of myocardial perfusion imaging (MPI) was investigated in patients with mildly impaired left ventricular (LV) function who had no chest pain but were suspected to have coronary artery disease (CAD).

METHODS AND RESULTS

Consecutive patients (n=72, mean age =67) who had no chest pain but with mildly impaired systolic LV function (mean LV ejection fraction =52%) or LV asynergy and suspected to have CAD were followed up for 4.9 years after stress MPI. The follow-up time was censored at the occurrence of cardiac death, hospitalization for congestive heart failure (CHF), acute coronary syndromes (ACS), or revascularization. Images were scored using a 20-segment model and a 0-4 scale, and then the summed stress, rest, and difference scores (SDS) were calculated. During follow-up, there were 2 cases of cardiac death, 8 of hospitalization for CHF, 4 of ACS and 2 of revascularization. Cox regression demonstrated that SDS >or=4 was an excellent predictor of cardiac events in all patients (hazard ratio =4.2, p=0.01), and especially in diabetic patients (hazard ratio =28.4, p=0.01).

CONCLUSION

Stress MPI is useful for predicting cardiac events and may be performed in patients without chest pain if they have mildly impaired systolic LV function or LV asynergy.

Contribution of the sST elevation/T-wave normalization in Q-wave leads during routine, pre-discharge treadmill exercise test to patient management and risk stratification after acute myocardial infarction: a 2.5-year follow-up study

OBJECTIVES

This study investigated whether ST-segment elevation and T-wave normalization (TWN) in Q-wave leads on pre-discharge exercise electrocardiogram (ECG) can contribute to patient management after a recent myocardial infarction (MI).

BACKGROUND

The clinical relevance of these exercise ECG changes remains controversial despite accumulating evidence of their association with myocardial viability. Because discrepancies of previous studies may depend on patient selection, the value of these ST/T abnormalities in the thrombolytic era should be better defined.

METHODS

One-hundred one patients, age 58 +/- 11 years, with a recent, first Q-wave MI (57% thrombolyzed, ejection fraction 43 +/- 7%) underwent pre-discharge, submaximal treadmill testing followed, in the absence of severe ischemia, by dobutamine stress echocardiography, thallium-201 single photon emission computed tomography, and coronary angiography.

RESULTS

ST elevation at peak exercise, but not TWN, was associated with more severe infarctions as indicated by higher peak creatine kinase (p < 0.05) and with a greater number of scarred segments both on echocardiography (p < 0.05) and scintigraphy (p < 0.01). However, the incidence of myocardial viability and ischemia did not differ between groups with or without these ST/T changes. Anterior infarction location and >or=3 echocardiographically scarred segments were among the independent predictors of ST elevation at peak ergometric exercise. During follow-up (31 +/- 13 months), the rate of hard events was low (8%) and similar between the study groups.

CONCLUSIONS

In patients after acute Q-wave MI without severe ischemia according to clinical and standard ECG criteria, exercise-induced ST elevation, but not TWN, is associated with larger infarctions. The contribution of these ST/T abnormalities toward identifying patients with myocardial viability or ischemia and determining risk stratification is poor. In-hospital management of such patients based on routine clinical practice is sufficient for selection of a population with a relatively low long-term risk.

Angiographic and prognostic correlates of cardiac output by cardiopulmonary exercise testing in patients with anterior myocardial infarction

STUDY OBJECTIVE

To assess the diagnostic and prognostic value of cardiac output assessed by cardiopulmonary exercise testing in patients with anterior acute myocardial infarction (AMI) and left ventricular dysfunction.

PATIENTS AND SETTING

Forty-six patients with AMI (7 female patients; mean +/- SD age, 55 +/- 8 years; ejection fraction, 39 +/- 7%) underwent cardiopulmonary exercise testing and coronary angiography following hospital discharge.

MEASUREMENT AND RESULTS

Cardiac output was estimated from oxygen uptake (VO(2)) during exercise according to a method based on the linear regression between arteriovenous oxygen content difference and percent maximum VO(2). Angiograms were scored using Gensini and Duke "jeopardy" scores. Cardiac output at anaerobic threshold (COAT) < or = 7.3 L/min was the best cutoff value for identifying multivessel coronary artery disease (relative risk, 3.1). Angiographic scores were significantly higher in patients with COAT < 7.3 L/min as compared to those with COAT > 7.3 L/min (82 +/- 8 vs 53 +/- 7 and 6 +/- 2 vs 4 +/- 3, respectively; p < 0.05) and were inversely and significantly correlated to COAT. Conversely, no correlation was found with ECG changes. COAT, VO(2) at anaerobic threshold, and peak VO(2) were univariate prognostic indicators. However, using Cox's model, COAT was the only multivariate predictor of outcome (odds ratio, 0.28; 95% confidence interval [CI], 0.09 to 0.9). Moreover, COAT < 7.3 L/min was associated to an increased risk of further cardiac events (odds ratio, 5; 95% CI, 1.4 to 17) and provided a significant discrimination of survival for the combined end point of cardiac death, reinfarction, and clinically driven revascularization.

CONCLUSIONS

COAT is a safe and feasible tool providing additional diagnostic and prognostic information in patients with AMI.

Risk stratification after acute myocardial infarction in the reperfusion era

Historically, risk stratification for survivors of acute myocardial infarction (AMI) has centered on 3 principles: assessment of left ventricular function, detection of residual myocardial ischemia, and estimation of the risk for sudden cardiac death. Although these factors still have important prognostic implications for these patients, our ability to predict adverse cardiac events has significantly improved over the last several years. Recent studies have identified powerful predictors of adverse cardiac events available from the patient history, physical examination, initial electrocardiogram, and blood testing early in the evaluation of patients with AMI. Numerous studies performed in patients receiving early reperfusion therapy with either thrombolysis or primary angioplasty have emphasized the importance of a patent infarct related artery for long-term survival. The predictive value of a variety of noninvasive and invasive tests to predict myocardial electrical instability have been under active investigation in patients receiving early reperfusion therapy. The current understanding of the clinically important predictors of clinical outcomes in survivors of AMI is reviewed in this article.

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.

Prognostic value of predischarge exercise stress echocardiography after acute myocardial infarction

A predischarge exercise test was performed by 70 patients 7 +/- 4 days (mean +/- SD) after acute myocardial infarction (AMI) to determine the short- and long-term prognostic value of predischarge exercise stress echocardiography (Ex-Echo) compared with exercise stress electrocardiography (Ex-ECG). Two-dimensional echocardiograms were obtained at rest and immediately after exercise; a wall motion score index was obtained both at rest and immediately after exercise. Results of the Ex-Echo were positive in 27 patients (39%), whereas those of Ex-ECG were positive in 34 (49%). The wall motion index after exercise was lower in patients who died during follow-up (85 vs 98, p = 0.01) and in those with cardiac events, defined as death, nonfatal reinfarction, or revascularization (88 vs 98, p = 0.005). More patients with a positive Ex-Echo result had short-term cardiac events (within 2 weeks) than patients with a negative Ex-Echo (6 [22%] vs 2 [5%], p = 0.04). The same was true for long-term mortality (12 [44%] vs 3 [7%], p = 0.0002), reinfarctions (10 [37%] vs 4 [9%], p = 0.01), revascularization procedures (11 [41%] vs 7 [16%], p = 0.023), and cardiac events (22 [81%] vs 12 [28%], p < 0.0001). Survival time was shorter in patients with positive compared with negative Ex-Echo results (34% difference between groups, 95% confidence interval [CI] 10% to 58%, p = 0.002). The same applied for cumulative survival free from cardiac events (43%, p = 0.001, 95% CI 9% to 77%.(ABSTRACT TRUNCATED AT 250 WORDS)

Value of radionuclide rest and exercise left ventricular ejection fraction in assessing survival of patients after thrombolytic therapy for acute myocardial infarction: results of Thrombolysis in Myocardial Infarction (TIMI) phase II study. The TIMI Study Group

OBJECTIVES

This study sought to determine the prognostic value of rest and exercise left ventricular ejection fraction in patients receiving thrombolytic therapy as part of the Thrombolysis in Myocardial Infarction (TIMI) trial.

BACKGROUND

In the prethrombolytic era, ejection fraction at rest as well as during exercise was an important prognostic index in patients recovering from acute myocardial infarction. The prognostic value of these measurements in the thrombolytic era is not clear.

METHODS

As part of the TIMI II protocol, we obtained radionuclide left ventricular ejection fraction at rest and during symptom-limited submaximal supine exercise. Measurements were related to 1-year all-cause as well as cardiac mortality. In addition, the relation between ejection fraction obtained at rest and 1-year cardiac mortality in this study was compared with the relation established previously in the prethrombolytic era by the Multicenter Postinfarction Research Group.

RESULTS

A distinct relation was noted between left ventricular ejection fraction at rest and all-cause mortality. The highest mortality rate (9.9%) was noted in patients with an ejection fraction < 30%. Those not undergoing a study had a 1-year mortality rate of 6.2%. Peak exercise ejection fraction provided prognostic information similar to that of rest ejection fraction. Likewise, change in ejection fraction from rest to exercise did not appreciably improve prognostic impact.

CONCLUSIONS

Rest left ventricular ejection fraction is an important prognostic index in patients receiving thrombolytic therapy. Peak exercise ejection fraction and the change in ejection fraction from rest to exercise do not provide appreciable prognostic data beyond those obtained at rest. Patients unable to exercise or those not having a rest study have a poor prognosis. When compared with the Multicenter Postinfarction Research Group data, there was strong evidence of a difference in survival in the two studies. At any level of ejection fraction, mortality was lower in TIMI II patients than in patients in the prethrombolytic era.

Acute myocardial infarction. Then and now

Dramatic changes in the management of acute myocardial infarction (AMI) have occurred in the past decade. While previous management strategies were primarily supportive, current strategies focus on achieving and maintaining patency of the infarct-related artery restoring blood flow to jeopardized myocytes, preserving left ventricular function, and preventing recurrences and complications in addition to promoting healing. Restoration of blood flow can be achieved pharmacologically with thrombolytic agents or mechanically with percutaneous transluminal coronary angioplasty (PTCA). Early use of antiplatelet agents and anticoagulants helps maintain patency of the infarct-related arteries and prevents thromboembolic complications. Administration of beta-blockers and angiotensin enzyme inhibitors are more specific means of conserving myocardium and preserving ventricular function. Additionally, several strategies for preventing arrhythmias such as prophylactic lidocaine use and routine long-term suppression of premature ventricular contractions with antiarrhythmic drugs are no longer routinely advocated. Basically, in the era prior to the eighth decade of this century, the primary direction of the therapeutic strategy for AMI was to reduce the oxygen demands in the infarcted myocardium; whereas in the subsequent years, the emphasis shifts to improvement in oxygen delivery, via thrombolysis, PTCA, and coronary artery bypass graft surgery. These interventional changes, when added to greater sophistication in the use of drugs to reduce oxygen demands, resulted in significant lowering of myocardial mortality.

Strategies for prognostic assessment of uncomplicated first myocardial infarction: 5-year follow-up study

OBJECTIVES

Our aim was to use noninvasive studies early after infarction to assess medium-term prognosis in patients with a first uncomplicated myocardial infarction.

BACKGROUND

Although the use of early postinfarction assessment to gauge short-term prognosis in myocardial infarction is well established, there have been few comprehensive evaluations of noninvasive methods for assessing medium- and long-term prognosis.

METHODS

We prospectively studied 115 consecutive patients < 65 years old with a first acute uncomplicated myocardial infarction to evaluate the prognostic role of predischarge cardiac studies. These included submaximal exercise testing, thallium-201 scintigraphy, radionuclide exercise ventriculography, two-dimensional echocardiography, ambulatory electrocardiographic (Holter) monitoring and cardiac catheterization. All patients without complications were followed up > or = 5 years.

RESULTS

During the follow-up period, 78 patients (68%) developed complications, which were severe in 37 (32%). Exercise thallium-201 scintigraphy yielded the highest percentage (77%) for correctly classified patients. It also had the highest predictive value for complications (97%) and severe complications (92%) when it was used in association with exercise testing and radionuclide ventriculography. The addition of cardiac catheterization did not improve on the predictive power of noninvasive studies. Four decision trees (exercise testing + echocardiography, exercise testing + radionuclide ventriculography, thallium-201 + echocardiography, thallium-201 + radionuclide ventriculography) allowed stratification of all patients in a high, intermediate or low risk category. The combination of thallium-201 scintigraphy and radionuclide ventriculography yielded the best results (90% predictive value for complications if the outcome of both tests was positive), but there were no significant differences with the other models.

CONCLUSIONS

Any combination of a test detecting residual ischemia or functional capacity, or both (exercise testing or thallium-201 scintigraphy), and a test assessing ventricular function (echocardiography or radionuclide ventriculography) results in useful prognostic information in patients with an uncomplicated first acute myocardial infarction.

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.

Should all patients undergo cardiac catheterization after a myocardial infarction?

Between one half and two thirds of patients who survive an acute myocardial infarction (AMI) may be at low risk for future complications and hence can be managed with medical therapy. However, the remaining patients are prone to future complications, which by and large occur within the subsequent 3 months and include cardiac death, recurrent AMI, unstable angina, and congestive heart failure. Current available methods for risk stratification include a good clinical evaluation, rest and stress electrocardiograms (preferentially combined with radionuclide imaging), and possibly two-dimensional stress echocardiography. In patients unable to exercise, pharmacologic perfusion scintigraphy affords a powerful means to identify high-risk patients. Patients deemed to be at high risk should be referred for cardiac catheterization and myocardial revascularization. The practice of performing routine cardiac catheterization after an AMI has led to an over use of resources in the United States. Such a practice is not based on any scientific evidence of enhanced benefit. In fact, in other Western world countries where only selected patients are referred for cardiac catheterization, patient survival appears to be similar to that in the United States. In conclusion, most patients after AMI, whether treated with thrombolytic therapy or not, can be managed conservatively and risk stratified on the basis of noninvasive testing, after which patients deemed to be at high risk should undergo invasive evaluation.

Prognostic assessment in coronary artery disease: role of radionuclide angiography

Left ventricular function is one of the most important determinants, if not the most important determinant, of outcome in patients with coronary artery disease. The ability of radionuclide angiography to assess resting and exercise ejection fraction accurately and reproducibly has been shown to be a critical determinant of survival in large-scale studies of survivors of myocardial infarction, as well as patients with chronic stable angina. In addition, several centers have demonstrated that the exercise ejection fraction is an extremely valuable (and perhaps the most valuable) noninvasive parameter in predicting survival among patients with coronary artery disease. The prognostic insights gained from the exercise ejection fraction add incremental predictive information to the coronary anatomic information obtained from coronary arteriography, especially in patients with multivessel disease and those with left ventricular dysfunction at rest.

Predicting severe ischemic events after uncomplicated myocardial infarction by exercise testing and rest and exercise radionuclide ventriculography

BACKGROUND

In 183 patients with uncomplicated myocardial infarction, exercise-induced angina, ST segment depression, decrease in ejection fraction, or inadequate increase in systolic blood pressure and low exercise tolerance were significantly associated with 4-year incidence of hard ischemic events.

METHODS AND RESULTS

Only the onset of both ST segment depression and a decrease in left ventricular ejection fraction with exercise was an independent predictor. ST segment depression and decrease in left ventricular ejection fraction had low sensitivity (61% and 70%) and specificity (56% and 51%) for hard ischemic events, but specificity increased to 78% when both were present. During medical therapy, 22 of 53 patients with both ST segment depression and a decrease in left ventricular ejection fraction with exercise had an ischemic event (i.e., 48.1% 4-year probability on Kaplan-Meier analysis vs 19.2% in the remaining 130 patients [p < 0.0005]).

CONCLUSIONS

Even if no single variable, derived from exercise testing, is a highly sensitive and specific predictor, specificity increases to a clinically relevant level by combining ST segment depression and a decrease in left ventricular ejection fraction with exercise, and in this way patients with recent infarction may be selected for coronary arteriography.

Right ventricular ejection fraction during exercise in patients with recent myocardial infarction: effect of the interventricular septum

To investigate the effect of interventricular septum (IVS) on right ventricular function during exercise, radionuclide angiocardiography was performed in 50 patients with recent myocardial infarction. Twenty-five patients had involvement of IVS according to thallium uptake in IVS (group I), and 25 patients were free of IVS involvement (group II). Although there was no statistical difference between the two groups in right ventricular ejection fraction (EF) at rest (45% +/- 10% vs 48% +/- 8%), patients in group I had significantly lower left ventricular (LV) EF (40% +/- 11% vs 53% +/- 11%, p < 0.01) and larger LV end-diastolic volume (129 +/- 46 vs 106 +/- 31 ml, p < 0.05) than those in group II. All parameters increased significantly during exercise in both groups, but patients in group I had significantly lower exercise right ventricular EF (50% +/- 10% vs 56% +/- 9%, p < 0.05), LVEF (44% +/- 11% vs 56% +/- 13%, p < 0.01), and larger LV end-diastolic volume (155 +/- 44 vs 129 +/- 37 ml, p < 0.05) than those of group II. Significant correlations were observed between right ventricular EF and LV end-diastolic volume at rest and during exercise (r = -0.48, p < 0.05, and r = -0.68, p < 0.01, respectively) in group I, but right ventricular EF correlated with LVEF only at peak exercise (r = 0.65, p < 0.01). In contrast, right ventricular EF did not correlate with any variables at rest or during exercise in group II.(ABSTRACT TRUNCATED AT 250 WORDS)

Assessment of early post-infarction ischemia: correlation between ambulatory electrocardiographic monitoring and exercise treadmill testing

PURPOSE

Demand-related myocardial ischemia detected by treadmill testing is commonly used to identify high-risk patients after myocardial infarction (MI). Although ischemia detected by ambulatory electrocardiographic monitoring (AECG) has also been shown to predict poor outcome in some patient groups, the relationship between AECG-detected ischemic ST changes and post-MI treadmill ischemia is unknown.

PATIENTS AND METHODS

We screened 94 patients after MI with 24-hour AECG monitoring and a Naughton treadmill test. Forty-two patients were excluded because of left bundle branch block, left ventricular hypertrophy, abnormal baseline ST segments, or digoxin therapy. In the remaining 52 patients, AECG was performed 5.1 +/- 2.2 days after MI (mean +/- SD) and the treadmill test 8.4 +/- 2.2 days after MI. Each patient was taking the same drugs for both studies, had no interim revascularization procedures, and all studies were interpreted blindly.

RESULTS

The treadmill test (ETT) was positive for ST changes and/or thallium reperfusion defects in 19 of 52 patients (36%). The AECG was positive for ischemia (ST depression greater than 1 mm, for more than 1 minute) in 14 of 52 patients (27%) (Group I), with 9.9 +/- 8.2 ischemic episodes per patient lasting 13.5 +/- 7.5 minutes per episode. The AECG was negative for ischemia in the remaining 38 patients (73%) (Group II). The ETT and AECG correlation was as follows: 9 patients with AECG-detected ischemic ST changes had positive ETT results; 10 patients without AECG-detected ischemic ST changes had positive ETT results; 5 patients with AECG-detected ischemic ST changes had negative ETT results; and 28 patients without AECG-detected ischemic ST changes had negative ETT results (p < 0.02 by chi 2). The predictive accuracy of a positive AECG identifying a positive ETT was 65% (specificity 85%, sensitivity 47%), and the predictive accuracy of a negative AECG identifying a negative ETT was 74%. Group I patients were older than Group II patients (63.6 +/- 8.2 years versus 53.2 +/- 10.6 years p < 0.02), more commonly had painless ETT ischemia (43% versus 18% p = 0.08), and tended to have positive ETT results at a lower level of exercise (366 +/- 210 seconds versus 588 +/- 212 seconds, p = 0.04).

CONCLUSION

Ischemic ST changes as detected by AECG monitoring correlate significantly with post-MI treadmill test results with a high specificity, albeit a low sensitivity. In patients without baseline ST-segment abnormalities and limited exercise capability, AECG monitoring may be of limited use in identifying early post-MI ischemia.

[Clinical factors which influence the 1-year post-infarction prognosis]

Many clinical factors influence the 1-year prognosis in myocardial infarction (MI) patients. The most important clinical determinants are the left ventricular dysfunction, myocardial ischemia, and complex ventricular arrhythmias. Some authors have found an independent prognostic value of complex ventricular arrhythmias, while others consider that ventricular arrhythmias predict future cardiac events only if associated with low ejection fractions. Other factors that have 1-year prognostic value are the following: a previous MI, a history of angina at least 3 months preceding the infarct, postmyocardial angina, and the criteria that indicate to the practitioner whether MI patients are medically ineligible for stress testing. There still remain controversies in regard to the predictive value of certain variables such as the site, type, and extension of the MI, the presence of complex ventricular arrhythmias, exercise-induced hypotension, ST segment elevation, and the electrical provocation of dangerous arrhythmias.

Clinical risk assessment after first myocardial infarction--is additional noninvasive testing necessary?

In order to assess whether the outcome of MI can be predicted by clinical data alone or whether and how much noninvasive testing is necessary to predict cardiac events or death, 361 patients were prospectively evaluated and followed for up to five years. A recursive partitioning analysis indicated that high-risk patients can be identified clinically after MI with a high degree of accuracy; to separate low-risk patients who need no further investigation or therapy, however, one additional noninvasive test is necessary which allows quantification of myocardial damage as well as exercise-induced ischemia. Additional tests added little to this risk prediction, indicating that multiple noninvasive testing should not be performed.

Assessment of acute myocardial infarction by nuclear imaging techniques

In recent years, nuclear cardiology techniques have been successfully applied in patients with acute myocardial infarction. These scintigraphic measurements have provided important diagnostic, therapeutic, and prognostic information based on the extent of myocardial damage and the functional reserve of the left ventricle. In particular, in the thrombolytic era, myocardial perfusion imaging and radionuclide angiography have been shown to be valuable methods for studying the effects of reperfusion on the extent of myocardial damage. Nuclear magnetic resonance imaging, preferably with contrast enhancement, is one of the newly developed nuclear imaging techniques that have probably the greatest potential in accurately delineating myocardial infarct size and in evaluating left ventricular function. Radionuclide procedures, on the other hand, employ more biologically oriented tracers and are therefore capable of monitoring biochemical changes in the course of acute myocardial infarction.

Left ventricular function in myocardial infarction. Predictive value during negative low-level exercise three weeks postinfarction

To evaluate whether the response of left ventricular pump function during low-level exercise in the early postinfarction period can anticipate its change during the first year after acute myocardial infarction (MI), global and regional ejection fractions (EF) were investigated using radionuclide angiography in 52 consecutive patients with negative predischarge exercise test. The changes in left ventricular EF and regional EF of the noninfarcted area during the early exercise test had a good linear relation with the changes during the first year after MI (r = 0.86, p less than 0.001 and r = 0.81, p less than 0.001, respectively). Our results indicate that the mobilization of the Frank-Starling mechanism and myocardial contractility were the important factors related to the change of left ventricular EF, and that the changes of left ventricular EF during exercise in the patient with a negative predischarge exercise test can predict the direction of change (concordant rise or fall) during the first year after MI.

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.

Value of exercise stress test, radionuclide angiography and coronary angiography in predicting new coronary events in asymptomatic patients after a first episode of myocardial infarction

One-hundred-and-fifty-five consecutive symptom-free patients underwent maximal treadmill exercise testing, rest and stress radionuclide angiography at least two months after an uncomplicated acute myocardial infarction; of these, 90 underwent coronary angiography. All patients were followed-up for a mean of 32 +/- 13 months regarding the prediction of hard (death and reinfarction) and soft (angina and coronary surgery) coronary events. The specificity, sensitivity, positive and negative predictive value of exercise stress test were 47%, 76% and 41% for any coronary events; none of the patients who incurred a hard coronary event showed ischemia during electrocardiographic exercise tests. Sensitivity, specificity and positive predictive value for failure to increase the ejection fraction of at least 5% were 60%, 45% and 30% for any coronary event and 25%, 49% and 2% for any hard coronary event. The presence of multivessel disease at coronary angiography showed a sensitivity of 62% for any coronary event and of 67% for hard coronary events; specificities were 66% and 57%, and predictive values were 52% and 10%, respectively. It is concluded that electrocardiographic exercise testing, radionuclide angiography and coronary angiography are not helpful two months after an episode of uncomplicated myocardial infarction in order to identify patients who will suffer a new coronary event.

Assessment of global and regional left ventricular performance at rest and during exercise after thrombolytic therapy for acute myocardial infarction: results of the Thrombolysis in Myocardial Infarction (TIMI) II Study

Global and regional left ventricular performances were evaluated with equilibrium radionuclide angiocardiography in patients in the Thrombolysis in Myocardial Infarction (TIMI) II trial at the time of hospital discharge. Studies at rest were available in 1,162 (69%) of the invasive and 1,150 (69%) of the conservative strategy patients, and exercise studies in 1,133 (67%) of the invasive and 1,145 (69%) of the conservative patients. Repeat studies were performed at the time of 6-week follow-up. Global and regional ejection fraction at rest were both comparable in patients assigned to each of the treatment strategies. However, at the time of hospital discharge patients in the invasive strategy had normal exercise responses more frequently (29.7 vs 25.8% p = 0.01), greater peak exercise LV ejection fraction (54.8 +/- 13.8% vs 53.1 +/- 14.1%, p = 0.004), greater exercise--rest change in LV ejection fraction (3.7 +/- 6.7% vs 2.7 +/- 7.2%, p less than 0.001) and greater peak exercise infarct zone regional ejection fraction (53.2 +/- 31.1% vs 50.3 +/- 33.0%, p less than 0.001) than patients assigned to the conservative strategy. At 6-week follow-up these differences between treatment strategies were no longer evident. When data were restricted to those collected at comparable work loads, similar differences in hospital discharge exercise performance between invasive vs conservative strategy patients were observed. Thus, there is a small transient difference in exercise global and regional LV performance associated with an invasive as opposed to conservative strategy after thrombolytic therapy. These differences are noted at the time of hospital discharge but not at 6 weeks, and are unlikely to confer clinical benefit.

Uncomplicated first myocardial infarction: strategy for comprehensive prognostic studies

To evaluate the prognostic role of combined cardiac studies (submaximal exercise test, thallium-201 scintigraphy, radionuclide exercise ventriculography, two-dimensional echocardiography, Holter monitoring and cardiac catheterization) in patients with a first acute myocardial infarction without complications during hospital admission, 115 consecutive patients aged less than 65 years were prospectively evaluated. The studies were carried out before hospital discharge and the patients were then clinically followed up for 12 months. During the follow-up period, 69 patients (60%) developed complications, which were severe in 23 (20%). Half of all complications and 70% of severe complications developed during the 1st follow-up month. Logistic regression analysis disclosed that the combination of studies with the highest predictive power for complications (probability of complications 99%) and severe complications (probability of severe complications 95%) was the association of exercise test + thallium-201 + echocardiogram. Four decision models (exercise test + echocardiography, exercise test + radionuclide ventriculography, thallium-201 scintigraphy + echocardiography, thallium-201 scintigraphy + radionuclide ventriculography) allowed the stratification of all patients in a particular risk category (high, intermediate or low). The best decision model was the association of thallium-201 scintigraphy + radionuclide ventriculography (probability of complications if both tests were positive 84%; probability of absence of severe complications if both tests were negative 88%), but there were no significant differences with the other models. Any association of a test detecting residual ischemia or functional capacity, or both (exercise test or thallium-201) and a test assessing ventricular function (echocardiography or radionuclide ventriculography) results in significant prognostic information in patients with an uncomplicated first acute myocardial infarction. Additional cardiac catheterization does not improve the predictive power of noninvasive studies, which should ideally be performed before hospital discharge because most complications develop during the 1st follow-up month.

Incremental prognostic accuracy of clinical, radionuclide and hemodynamic data in acute myocardial infarction

A logical sequence of testing in evaluating prognosis early in acute myocardial infarction (AMI) would be to use clinical data first, then add noninvasive data and finally add invasive data. The incremental prognostic information concerning 1-year survival obtained from such a sequence in 107 patients with AMI was studied using logistic regression and receiver-operating characteristic curves. Cardiac mortality was 24% at 1 year. Clinical data obtained soon after admission (prior myocardial infarction, heart rate, blood pressure, age) were 78 +/- 5% accurate in the prediction of 1-year survival. The addition of radionuclide-estimated left ventricular ejection fraction or invasive hemodynamic data to the clinical model at this time improved prognostic accuracy to 84 +/- 5% (p = 0.05) and 87 +/- 4% (p = 0.007), respectively. The further addition of invasive data to the model containing clinical and left ventricular ejection fraction data provided a further increment in prognostic accuracy to 89 +/- 4%, whereas no significant increase in accuracy was seen on addition of left ventricular ejection fraction to the model containing clinical and invasive data. It is concluded that clinical data provide important prognostic information concerning late survival early in the course of AMI. This may be improved by the logical application of noninvasive and invasive studies at this time.

Trends in use of coronary angiography in subacute phase of myocardial infarction

BACKGROUND

Most patients do not undergo acute reperfusion after myocardial infarction, and which of these patients should undergo coronary angiography is still debated.

METHODS AND RESULTS

We analyzed the 1-year clinical outcomes and rates of coronary angiography performed as late as 60 days after myocardial infarction in 3,804 patients admitted between 1979 and 1988 and followed in six different centers. Patients less than 75 years old were classified into low-, medium-, and high-risk groups using a multivariate analysis of historical and clinical variables gathered during the first 8 hospital days. Patients who underwent early reperfusion (17%, all after 1984) were analyzed separately. To analyze time trends, patients were compared before and after mid-1984. Mortalities from day 9 through 1 year were similar for the two time periods in the low- (3.3% versus 2.5%) and medium-risk (7.4% versus 5.6%) groups, but mortality was lower for the high-risk group after 1984 (31.6% versus 20.0%). The proportion of patients undergoing coronary angiography increased dramatically in each group after 1984 (low risk, 18% versus 48%; medium risk, 23% versus 49%; high risk, 10% versus 32%, before and after 1984, respectively). Furthermore, a large percentage of patients (more than 40%) in the low-risk group did not have at least one of the indications for coronary angiography recently recommended by a joint task force. Among patients undergoing coronary angiography, the proportion of patients with three-vessel coronary artery disease decreased after 1984, whereas the proportion undergoing mechanical revascularization in the year after infarction increased in all risk groups.

CONCLUSIONS

Despite the recent development of noninvasive techniques with high sensitivity for detecting high-risk patients after myocardial infarction, coronary angiography is being performed increasingly in all patients, including those determined to be at low risk for complications based on clinical data. The economic consequences of such a trend could be considerable, and its impact requires careful analysis.