Comparison of clinical and treadmill variables for the prediction of outcome after myocardial infarction

Prognostic Importance of Previous Myocardial Infarction in Patients Receiving Thrombolytic Therapy for Acute Infarction

This study evaluated the prognostic significance of reinfarction location by considering the previous site or type of myocardial infarction (MI) among 1601 patients with a history of previous MI who took part in the International (non-Italian) tPA/STK trial and/or the Israeli GUSTO study population. These patients were accordingly divided and hospital mortality was compared by six location groups as follows: acute inferior with previous inferior (8.1% hospital mortality), acute inferior with previous anterior (12.8%), acute anterior with previous inferior (13.3%), acute anterior with previous anterior (11.1%), acute inferior with previous non-Q-wave MI (7.6%), and acute anterior with previous non-Q-wave MI (11.2%) (p = 0.17 for comparison between the six groups). Hospital mortality tended to increase among patients with an anterior reinfarction compared with those with an inferior one (12.1% vs. 9.5%, p = 0.12). Among patients with a reinfarction at a different ECG location from the previous event, mortality tended to be higher compared with patients with two MIs at the same location (13.1% vs. 9.7%, p = 0.07). Recurrent MI following a previous Q-wave MI did not cause a higher mortality compared with a previous non-Q-wave type of MI (11.5% vs. 9.5%, p = 0.24). Among patients sustaining reinfarction, overall mortality did not differ between STK- and tPA-treated patients (11.0% vs. 11.4%, p = NS). In conclusion, the current study identified trends for higher mortality rates in patients with anterior compared with inferior reinfarction, with remote compared with the same ECG location of the two infarctions but not following a previous non-Q-wave compared with Q-wave MI. However, no particular combination of successive MIs location was significantly associated with a higher risk for hospital mortality.

Exercise echocardiography. Principles, methods, and clinical use

Stress echocardiography is composed of a family of examinations in which various forms of cardiovascular stress are combined with echocardiographic imaging to assist in the diagnosis of coronary artery disease. Exercise cardiography has evolved over the past 20 years into a routinely available clinical tool employed in both university and community hospital settings. This article discusses advantages and disadvantages of using exercise echocardiography.

[Is the exercise test performed after myocardial infarct really useful in improving prognosis? Arguments contra]

Exercise testing is considered to play a major role in risk stratification after myocardial infarction. With the aim of improving prognosis, an exercise test should be able to identify patients at higher risk of coronary events. In this sense, its major limitation is a low positive predictive value, especially in patients who have been treated with thrombolytic agents. This fact limits its clinical value in the decision making process in individual patients. Finally, the decision to revascularize with angioplasty or surgery when only a positive exercise test result is taken into account, has not been proven to prolong life in these patients. All these considerations should make us think about some clinical attitudes that are taken for granted.

Comparison of maximum versus submaximum exercise testing in providing prognostic information after acute myocardial infarction and/or coronary artery bypass grafting

Exercise testing after acute myocardial infarction (AMI) provides prognostic information. In many studies submaximum exercise tests performed until a given work load, metabolic equivalents (METs) level, or heart rate were used or patients discontinued the exercise test prematurely because of symptoms. We showed recently that peak oxygen uptake during maximum exercise provides independent prognostic information in patients with coronary artery disease. It is, however, not known whether maximum exercise testing is superior in predicting mortality than testing until a target level. Second, it is unclear which target end point best classifies patients at increased risk. Therefore, the independent relation between mortality and indexes of, respectively, maximum and submaximum exercise capacity, were analyzed in 527 patients, who were tested until exhaustion. To express submaximum exercise capacity dichotomous variables (the ability to reach a target METs level or not), and a continuous variable relative to maximum exercise capacity (the ventilatory anaerobic threshold) were used. After adjustment for significant covariates, peak oxygen uptake was significantly related to all-cause and cardiovascular mortality. The target level of 5 METs and the ventilatory anaerobic threshold, when expressed in absolute workload, were related to mortality when unadjusted, but after adjustment for age and other confounders significancy was lost. In multiple Cox regression analysis, the prognostic power of peak oxygen uptake remained significant when 5 METs or the anaerobic threshold were forced into the equations. When analyzing the relation of various METs levels with mortality, the 7 METs level was independently related to all-cause and cardiovascular mortality and yielded the highest diagnostic accuracy. We conclude that maximum exercise testing is more potent in predicting mortality than the ability to reach a predetermined level of exercise, such as the commonly used 5 METs level or the anaerobic threshold. Otherwise, the use of a higher target level of 7 METs is recommended.

Prognostic value of dobutamine echocardiography early after uncomplicated acute myocardial infarction: a comparison with exercise electrocardiography

OBJECTIVES

This study sought to assess the relative prognostic power of dobutamine echocardiography and exercise electrocardiography after acute myocardial infarction.

BACKGROUND

The prognostic value of dobutamine echocardiography early after acute myocardial infarction has not yet been reported.

METHODS

One hundred seventy-eight patients (mean age 58 +/- 9 years) with a first uncomplicated acute myocardial infarction underwent predischarge dobutamine echocardiography (5 to 40 micrograms/kg body weight per min, plus atropine if needed) and symptom-limited bicycle exercise electrocardiography and were followed up for 17 +/- 13 months. Stress-induced dyssynergy and ST segment depression > 1 mm were considered criteria of positivity for dobutamine echocardiography and exercise electrocardiography, respectively.

RESULTS

Dobutamine echocardiography was positive in 83 patients and exercise electrocardiography in 60. At follow-up there were 5 deaths, 6 nonfatal myocardial infarctions (11 hard events) and 20 cases of unstable angina. Dobutamine echocardiography and exercise electrocardiography had similar negative predictive values both for all events (88% and 86%, respectively) and for hard events (98% and 95%, respectively). The hard events rate was significantly higher in patients with positive rather than negative dobutamine echocardiography (relative risk [RR] 5.15, 95% confidence interval [CI] 1.14 to 23.16), although there was no difference between patients with positive and negative exercise electrocardiograms. When Cox analysis was performed, dobutamine echocardiography had an independent prognostic value both for all events (RR 2.88, 95% CI 1.37 to 6.08) and for hard events (RR 6.56, 95% CI 1.42 to 30.46).

CONCLUSIONS

After uncomplicated acute myocardial infarction, dobutamine echocardiography and exercise electrocardiography have a similar high negative predictive value for both all events and hard events only. Positive dobutamine echocardiography, but not positive exercise electrocardiography, identifies a group of patients at higher risk of subsequent cardiac events.

Prognostic importance of myocardial ischemia detected by ambulatory monitoring early after acute myocardial infarction

BACKGROUND

After an acute myocardial infarction, it is important to determine the risk of a subsequent coronary event. We studied the prognostic value of myocardial ischemia detected by ambulatory electrocardiographic (ECG) monitoring in patients who had recently had an acute myocardial infarction.

METHODS

Five to seven days after acute myocardial infarction, 406 patients underwent 48-hour ambulatory ECG monitoring, with submaximal exercise testing before discharge and measurement of the left ventricular ejection fraction within 28 days after infarction. Death, nonfatal myocardial infarction, and admission to the hospital because of unstable angina were the principal end points recorded during the one-year follow-up period.

RESULTS

The overall incidence of myocardial ischemia detected by ambulatory ECG monitoring was 23.4 percent. The mortality rates at one year were 11.6 percent among the patients with ischemia and 3.9 percent among those without ischemia (P = 0.009); 3.9 percent among the patients with a positive exercise test, 3.0 percent among those with a negative exercise test, and 16.4 percent among those in whom an exercise test was not performed (P < 0.001); and 3.6 percent among the patients with an ejection fraction greater than 50 percent, 3.5 percent among those with an ejection fraction between 35 and 50 percent, and 18.2 percent among those with an ejection fraction below 35 percent (P = 0.001). Using multiple logistic regression, we found that no diagnostic test performed after myocardial infarction provided additional prognostic information beyond that provided by the standard clinical variables used to predict the risk of death. When nonfatal myocardial infarction and admission to the hospital because of unstable angina were also included as outcome variables, ambulatory monitoring for ischemia was the only test that contributed significantly to the model. For the patients with ischemia detected by ambulatory monitoring, as compared with those who did not have evidence of ischemia, the odds ratio was 2.3 (95 percent confidence interval, 1.2 to 4.5) for death or nonfatal myocardial infarction (P = 0.009) and 2.8 (95 percent confidence interval, 1.6 to 4.8) for death, nonfatal myocardial infarction, or admission to the hospital because of unstable angina (P < 0.001).

CONCLUSIONS

Myocardial ischemia detected by ambulatory ECG monitoring is common early after acute myocardial infarction and provides prognostic information beyond that available from standard clinical information.

Methodologic sources of inconsistent prognoses for post-acute myocardial infarction

PURPOSE

To investigate basic methodologic problems that could explain inconsistent and contradictory results for predictor variables in studies of prognosis after myocardial infarction (MI).

MATERIALS AND METHODS

Studies on postinfarct prognosis published in English between 1979 and 1991 were identified with a MEDLINE literature search. The key words used for the computer search were: "prognosis" and "myocardial infarction" in the title and "mortality" or "survival" or "outcome" in the title or abstract. Reference lists in the reports captured by the search were examined for pertinent articles, and additional articles were sought in the index pages of two prominent journals. To be included in the analysis, a study had to fulfill the following eligibility criteria: a cohort study or randomized, controlled trial; sample size > or = 50 patients; a clear identification of the time when follow-up began, after the acute phase of MI and either before or at hospital discharge; follow-up for a minimum of 6 months or median/mean of 1 year; and multivariable analysis for intervals no longer than 2 years after the MI. Eight methodologic standards addressing sources of major problems were established and applied to each study.

RESULTS

Of 766 reports identified, 111 fulfilled the eligibility criteria. The median number of standards fulfilled was 3, the highest 6. The proportions of studies complying with each of the 8 methodologic standards were: (1) inception cohort, 60%; (2) total death as an unequivocal outcome, 54%; (3) verification of cause-specific deaths (in 62 studies analyzing cardiac death), 37%; (4) analysis of crucial variables describing baseline severity, 13%; (5) indication of quantitative scope of the spectrum of baseline severity, 20%; (6) reproducible classification of candidate predictor variables, 40%; (7) adequate identification of quantitative importance of and boundaries for statistically significant predictor variables, 39%; and (8) evaluation of impact of treatment on predictor variables, 13%.

CONCLUSIONS

The results show that studies on postinfarct prognosis have frequently disregarded basic methodologic principles. Suitable adherence to these principles in future research will allow improved interpretation of results and can reduce inconsistent findings, while improving the applicability of the identified predictors.

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.

Prognosis of patients with left ventricular dysfunction, with and without viable myocardium after myocardial infarction. Relative efficacy of medical therapy and revascularization

BACKGROUND

The uptake of F-18 deoxyglucose into dysfunction segments after myocardial infarction identifies metabolically active (FDG+) or inactive (FDG-) myocardium. Although patients with FDG+ segments have been found to be at risk for adverse events, the prognostic significance of viable myocardium in relation to other influences on postinfarction prognosis, including revascularization, remain ill defined. The purpose of this study was to investigate the relative prognostic significance of FDG+ tissue and to establish whether myocardial revascularization in patients with viable tissue attenuates the risk of adverse outcome.

METHODS AND RESULTS

One hundred thirty-seven patients with left ventricular dysfunction and resting perfusion defects after myocardial infarction underwent positron emission tomography with both dipyridamole stress Rb-82 perfusion imaging and FDG imaging. After the exclusion of 4 patients proceeding to transplantation, 2 with uninterpretable scans and 2 lost to follow-up, 129 patients were followed clinically for 17 +/- 9 months. Four groups were defined: patients with FDG+ dysfunctional myocardium who were revascularized (n = 49) or treated medically (n = 21) and those with FDG- segments who were revascularized (n = 19) or treated medically (n = 40). The groups of patients with FDG+ or FDG- findings, with and without revascularization, did not differ with respect to known determinants of postinfarction prognosis: age, left ventricular ejection fraction, or the prevalence of multivessel disease. Nonfatal ischemic events occurred in 48% of medically treated FDG+ patients compared with 8% of revascularized patients with FDG+ tissue (P < .001) and 5% of patients with FDG- myocardium (P < .001). Thirteen patients died from cardiac causes; 11 (85%) had a left ventricular ejection fraction of < 30%, and these patients were evenly distributed between FDG+ and FDG- groups. Using Cox's proportional hazards model, only the presence of FDG+ myocardium (odds ratio, 12.9; P < .001) and the absence of revascularization (odds ratio, 5.8; P = .002) independently predicted ischemic events, while only age (P = .02) and ejection fraction (P < .001) but not the presence of viable myocardium were predictive of death.

CONCLUSIONS

Residual viable myocardium after myocardial infarction may act as an unstable substrate for further events unless it is revascularized. Despite this association, age and left ventricular dysfunction remained the strongest predictors of cardiac death after myocardial infarction in these patients with a spectrum of left ventricular dysfunction.

Predictors of nonfatal reinfarction in survivors of myocardial infarction after thrombolysis. Results of the Gruppo Italiano per lo Studio della Sopravvivenza nell'Infarto Miocardico (GISSI-2) Data Base

OBJECTIVES

This study was designed to reassess the prediction of recurrent nonfatal myocardial infarction in patients recovering from acute myocardial infarction after thrombolysis.

BACKGROUND

Recurrent nonfatal myocardial infarction is a strong and independent predictor of subsequent mortality. Current knowledge of risk factors for nonfatal reinfarction is still largely based on data gathered before the advent of thrombolysis. Thus, this prospective study was planned to identify harbinger of nonfatal reinfarction in the postinfarction patients of the multicenter Grouppo Italiano per lo Studio della Sopravvivenza nell'Infarto Miocardico (GISSI-2) trial.

METHODS

Predictors of nonfatal reinfarction at 6 months were analyzed by multivariate technique (Cox model) in 8,907 GISSI-2 survivors of myocardial infarction with clinical follow-up, relying on a set of prespecified variables reflecting residual ischemia, left ventricular failure or dysfunction, complex ventricular arrhythmias, comorbidity as well as demographic and historical factors.

RESULTS

The postdischarge to 6-month incidence rate of nonfatal reinfarction was 2.5%. Independent predictors of nonfatal reinfarction were cardiac ineligibility for exercise test (relative risk 2.97, 95% confidence interval [CI] 1.98 to 4.45), previous myocardial infarction (relative risk 1.70, 95% CI 1.22 to 2.36) and angina at follow-up (relative risk 1.50, 95% CI 1.10 to 2.04). On further multivariate analysis, performed in 6,580 patients with both echocardiographic and electrocardiographic monitoring data available, a history of angina emerged as an additional risk predictor (relative risk 1.58, 95% CI 1.10 to 2.25).

CONCLUSIONS

The 6-month incidence of nonfatal reinfarction is rather low in survivors of myocardial infarction after thrombolysis. Cardiac ineligibility for exercise testing and a history of coronary artery disease are risk predictors. Recurrent nonfatal infarction is not predictable by qualitative variables reflecting residual ischemia, except by postdischarge angina. Prediction of nonfatal reinfarction appears less accurate than prediction of mortality, as almost 50% of reinfarctions occur in patients without any of the identified risk factors.

Predictors and long-term prognostic significance of recurrent infarction in the year after a first myocardial infarction. SPRINT Study Group

This study was undertaken to examine whether clinical factors predict reinfarction within 1 year of a first acute myocardial infarction (AMI) and to quantify the subsequent influence of reinfarction on long-term mortality. Data from 3,695 patients with a first AMI included in the Secondary Prevention Reinfarction Israeli Nifedipine Trial Registry were analyzed. The 1-year reinfarction incidence was 6.0% (220 of 3,695) and in-hospital mortality during reinfarction was 31%. Patients with reinfarction were older (63.0 vs 60.8 years) at entry. The independent clinical predictors for 1-year reinfarction were (adjusted relative odds): peripheral vascular disease (2.12), anterior location of the first AMI (1.62), angina before the first AMI (1.53), congestive heart failure on admission (1.34), diabetes (1.33), systemic hypertension (1.28) and age increment (1.13). One-year reinfarction rate increased from 4.0% in patients with 0 or 1 risk factor to 23.3% in patients with 5 to 6 risk factors (p < 0.0001). Patients with reinfarction had significantly increased 1- and 5-year mortality compared with those who had no reinfarction (11.8 vs 5.3% and 40.1 vs 20.3%, respectively, p < 0.001). Recurrent AMI within 1 year was the most powerful predictor of long-term (mean 5.5 years) total mortality (adjusted relative risk = 4.76).

Early exercise testing after acute myocardial infarction in the elderly: clinical evaluation and prognostic significance

Early exercise testing (EET) after acute myocardial infarction (MI) is a well-established means of detecting patients at high risk for subsequent cardiac events. However, the value of this test is not well documented in elderly patients. We evaluated the clinical and prognostic significance of EET in 188 patients, aged 70 years or more, 14 +/- 3 days after an uncomplicated acute MI. The mean follow-up period was 3.6 years (range 1 to 6 years) in 95% of the patients. The total mortality rate was 13.5% (24/178) and the cardiac-related mortality rate was 7.8% (14/178), with 64% of the deaths occurring in the first 3 years. There were no complications during EET. The following parameters measured during EET on a bicycle ergometer were predictive of subsequent cardiac death: an increase in systolic blood pressure of less than 30 mm Hg (p < 0.001), an increase in the double product of less than 12,500 mm Hg.beats/min (p < 0.001), a maximal load less than 60 W (p < 0.001), and a total duration of exercise less than 5 minutes (p < 0.001). The combination of these four parameters increased the predictive value of the test (p < 0.0001). ST segment depression and ventricular arrhythmias during exercise were not correlated with the incidence of subsequent cardiac death, but the degree of ST segment depression was directly and significantly (p < 0.0001) associated with the incidence of subsequent nonlethal cardiac events (coronary bypass surgery, coronary angioplasty, reinfarction, or unstable angina).(ABSTRACT TRUNCATED AT 250 WORDS)

Risk stratification by early exercise testing after an episode of unstable coronary artery disease. The RISC Study Group

After stabilization of symptoms by medication a predischarge exercise test was performed in 855 men admitted with suspected unstable angina (54%) or non-Q-wave myocardial infarction (46%). Multiple logistic regression analysis demonstrated that the number of leads with ST-depression at exercise, low maximal work load, increasing age and ST-elevation in electrocardiogram at rest had independent prognostic value concerning the risk of myocardial infarction or death during the following year. Therefore a combination of extension of ST-depression and peak work load was used to define 'high and low risk response' at the exercise test. After 1 year the mortality in patients with 'high risk' compared to 'low risk' exercise response was 3.6% and 0% (P < 0.001) and the risk of either myocardial infarction or death was 15.4% and 3.9% (P < 0.0001), respectively. ST-depression, occurrence of angina and low peak load at exercise were independent predictors of future severe angina. After 1 year 29.5% of patients with any of these indicators at exercise had incapacitating symptoms that necessitated referral for coronary angiography compared to 4.8% in the group without these findings (P < 0.0001). The predictive value of the exercise test remained high in subgroups based on inclusion diagnosis, age or findings in electrocardiogram at rest and independently of treatment with beta-blockade, other antianginal medication or aspirin at the time of the exercise test.

Impact of treatment strategy on predischarge exercise test in the Thrombolysis in Myocardial Infarction (TIMI) II Trial

Predischarge supine bicycle ergometry was used to assess persistent myocardial ischemia in postinfarction patients who received thrombolytic therapy and were randomized to an invasive versus conservative strategy in the Thrombolysis in Myocardial Infarction (TIMI) II trial. The frequency of ischemic responses in both strategies, and the 1-year prognostic importance of the different exercise test outcomes were examined. At 14 days, the percentage of patients with any adverse outcome (including death, presence of exercise-induced ST-segment depression, or inability to perform the exercise test) was 33.7% of 1,681 randomly assigned to the invasive strategy compared with 34.6% of 1,658 randomly assigned to the conservative strategy (p = 0.57). The 1-year mortality was greater in patients who did not perform the predischarge exercise test (7.7%) than in those who did (1.8%) (p < 0.001); the former were older, and a greater proportion were women, had a more frequent history of myocardial infarction, and more extensive coronary artery disease (p < 0.01 for each comparison). The 1-year mortality in patients with exercise-induced ST-segment depression or chest pain was only 1.4% (3 of 22) among those randomly assigned to the conservative strategy where coronary angiography and revascularization were recommended if the test result was abnormal (relative risk compared with those without ST-segment depression or chest pain 0.6; 99% confidence interval 0.1 to 2.9).(ABSTRACT TRUNCATED AT 250 WORDS)

Exercise-provoked ST-segment depression and prognosis in patients recovering from acute myocardial infarction. Significance and pitfalls

The importance of maximal versus submaximal exercise testing and the significance of heart failure on the prognostic value of exercise-provoked ST-segment depression > or = 0.1 mV was studied in 143 patients recovering from acute myocardial infarction. Patients were exercise tested prior to discharge and follow up lasted for up to 18 months (mean 17 months). End-point was first major event (i.e. first non-fatal reinfarction or death). A symptom-limited exercise test was superior to a heart-rate-limited test in detecting ST-segment depressions (27% vs. 20%: P < 0.5), and patients with ST-segment depression at lower heart rates did not have an increased risk of subsequent events compared with patients with ST-segment depression at higher heart rates (14% vs. 27%; NS). Heart failure surpassed ST-segment depression as a risk predictor (34% vs. 18%). Based on a meta-analysis including 13 studies (1987 patients) exercise-provoked ST-segment depression possessed an increased risk of subsequent major events (P < 0.0001; risk ratio = 1.90; 95% confidence limits 1.43,2.51). Thus, ST-segment depression provoked by a symptom-limited test selects patients with an increased risk of subsequent major events. In patients with a history of heart failure exercise-provoked ST-segment depression is of limited value.

Prognostic value of changes in R-wave amplitude during exercise testing after a first acute myocardial infarction

To investigate the prognostic value of exercise-induced changes in R-wave amplitude and their relation to other exercise and angiographic variables, 303 consecutive patients who underwent maximal exercise testing and coronary angiography within 2 months of a first acute myocardial infarction were studied. R-wave amplitude at peak exercise increased or was unchanged in 159 patients (57.4%) and decreased in 118 (42.6%). Increased R-wave amplitude was significantly related to underlying 3-vessel disease (p = 0.0001), the extent of ST-segment depression on exercise (p = 0.0001), and the time to 1 mm ST depression (p less than 0.05). Follow-up information was available in 285 patients (86.4%) at a mean of 4 +/- 1.8 years. Death from cardiac causes occurred in 25 patients (9%); 18 (6.5%) developed recurrent myocardial infarction, and 32 (11.6%) developed angina. Variables with a predictive value for cardiac death were maximal exercise heart rate (p = 0.0005), occurrence of exercise-related supraventricular arrythmia (p = 0.02), and number of diseased vessels (p = 0.02). R-wave changes had no predictive value. No variable had a predictive value for recurrent infarction. Maximal exercise heart rate (p = 0.02) and increased R-wave amplitude (p = 0.0001) were significantly related to the occurrence of angina at follow up. Exercise-related R-wave increases were associated with the presence of angina at follow-up, but had no predictive value for cardiac death or recurrent infarction; their association with subsequent angina appears to reflect an association with more severe underlying coronary disease.

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.

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

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

Factors associated with recurrent myocardial infarction within one year after acute myocardial infarction

In a large population of patients (n = 3666) who were discharged from the hospital after acute myocardial infarction and followed up for 1 year, factors associated with recurrent nonfatal (n = 171) or fatal (n = 74) infarction were identified. Also, the effects of combining various end points (recurrent nonfatal or fatal infarction and other cardiac death) in multivariate analyses, a practice common in many small studies that evaluate the predictive-value of various treatments or special tests, was examined. In univariate analyses, patients with nonfatal recurrent infarction did not differ with respect to age or gender from infarct-free survivors, but they more often had a history of previous myocardial infarction, congestive heart failure, angina pectoris, and diabetes; more severe pulmonary congestion was present on chest x-ray during the admission, and a non-Q wave index infarction was more frequent. Patients with either a fatal or nonfatal recurrent infarction had more angina pectoris during follow-up (55% to 60%) compared with 27% in event-free survivors and 31% in patients who died of other cardiac causes in whom this factor could be assessed before death. In multivariate analyses, historical and clinical prognostic factors were ranked differently for fatal or nonfatal reinfarction and other cardiac causes of death; angina pectoris at follow-up was highly related to recurrent infarction (fatal or nonfatal), along with a history of diabetes, and a non-Q wave index infarction. These factors were not independently related to other causes of cardiac death.(ABSTRACT TRUNCATED AT 250 WORDS)

Prognostic use of a QRS scoring system after hospital discharge for initial acute myocardial infarction in the Framingham cohort

Myocardial infarct size is an important risk factor for survival after acute myocardial infarction (AMI). The purpose of this study was to determine the prognostic value of myocardial infarct size, as estimated by the Selvester 54-criteria/32-point QRS scoring system, in the Framingham cohort. During the first 30 years of the Framingham Heart Study, a total of 384 participants developed an AMI requiring hospitalization; from this group, 243 patients met the following inclusion criteria: (1) no electrocardiographic changes due to a previous infarction, (2) survival greater than 3 days after discharge from the AMI hospitalization and (3) no electrocardiographic evidence of conduction disturbances or ventricular hypertrophy at the time of their final in-hospital electrocardiogram. Univariate and multivariate analyses were performed to test the association of the QRS score, and other associated risk factors, with time until coronary heart disease-related death. QRS score was found to be significantly associated with outcome (p = 0.03), as was the systolic blood pressure before infarction (p greater than 0.001). Both univariate and multivariate analysis showed that a history of systolic hypertension was the variable most strongly associated with coronary heart disease-related death. Thus, identification of AMI survivors at high risk for subsequent mortality can be improved by routine blood pressure measurement before AMI, and QRS scoring of the electrocardiogram taken at hospital discharge.

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

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

The prognostic value of right atrial pacing after acute myocardial infarction

We performed right atrial pacing in 90 consecutive patients 10 to 30 days (mean 16.8 days) after acute myocardial infarction. Right atrial pacing was normal in 28 patients, depression of the ST segment occurred in 27 patients, systolic blood pressure fell below control values in 20 patients and, in 15 patients, right atrial pacing was non-diagnostic. Follow-up was from 12 to 28 months (mean = 17.3). Global mortality was 11.1%, with none of the patients with normal tests dying, 11% of those with ST depression, 30% of those with induced hypotension (P less than 0.01) and 7.1% of those in whom pacing was non-diagnostic. Patients with high clinical risk at discharge in Peel Class III-IV, showed 41.2% mortality during the period of follow-up. None of those had shown normal responses to pacing, but those dying included 50% of the patients with ST depression and 66.7% of those in whom right atrial pacing induced hypotension. Development of new angina during the period of follow-up was more frequent among the patients with ST depression (33.3%) (P less than 0.001). Thus, our results showed that right atrial pacing was useful in predicting mortality after acute myocardial infarction. In patients at high risk, we observed that a fall of systolic blood pressure was the best predictor of mortality.

Diastolic time during low-level exercise in the late phase of hospitalization for acute myocardial infarction

To evaluate DT during a low-level exercise test, the relation between DT and heart rate was studied by ear densitography in the late phase of hospitalization for acute MI. None of the patients had an ischemic electrocardiographic response. The patients were divided into two groups: group 1 was comprised of nine patients with a resting left ventricular end-diastolic volume of 140 ml or more, and group 2 was comprised of nine patients with a left ventricular end-diastolic volume less than 140 ml. The QS2 and heart rate had an linear inverse relation during exercise, and DT and heart rate had an nonlinear inverse relation (DT = e(7.27-0.0166 x heart rate) and DT = e(7.11-0.0142 x heart rate) for groups 1 and 2, respectively). Significant prolongation of the QS2 with consequent shortening of DT (p less than 0.05) was observed in group 1. Thus, in addition to a larger decrease in DT with a small change in heart rate, particularly during low-level exercise, patients with increased left ventricular end-diastolic volume have a potential for initiating subendocardial ischemia which results in further prolongation of systole and, hence, greater abbreviation of DT.

Does the rest electrocardiogram after myocardial infarction determine the predictive value of exercise-induced ST depression? A 2 year follow-up study in a veteran population

The failure of exercise-induced ST segment depression to consistently predict prognosis in patients after myocardial infarction could be a result of population differences and the rest electrocardiogram (ECG). These hypotheses were tested by studying 198 veterans who survived a myocardial infarction, underwent a submaximal predischarge treadmill exercise test and were followed up for cardiac events for 2 years. During the 2 years, 29 deaths, 19 reinfarctions and 28 revascularization procedures were documented. The prevalence of death or reinfarction was two times higher in patients who had exercise-induced ST depression than in patients who did not. However, in the 55 patients without Q waves, the risk increased to 11 times for an abnormal ST response. These findings suggest that exercise-induced ST depression only predicts high risk in patients after myocardial infarction whose ECG at rest does not exhibit Q waves and that differences in the prevalence of rest ECG patterns are the most likely explanation for the failure of agreement among prior studies.

Exercise testing after myocardial infarction: relative values of the low level predischarge and the postdischarge exercise test

This study was undertaken to compare the relative values of the low level predischarge exercise test and the postdischarge (6 weeks) symptom-limited test in 518 consecutive patients admitted with an acute myocardial infarction. Of the patients who did not develop significant ST segment depression or angina during the predischarge test, the symptom-limited test also remained negative in 91.5 and 91.9% of the patients, respectively. Similar results were obtained with ST segment elevation and the systolic blood pressure response during the two exercise tests with only 2.1 and 11.4% changing from normal to abnormal, respectively. Discriminant function analysis was done to predict the occurrence of coronary events (unstable angina, reinfarction, cardiac failure, cardiac death) with use of the data from the exercise tests together with other clinical and investigational data. The jackknife method correctly classified 71.9 and 71.4% of the patients with the data from the predischarge exercise test and symptom-limited test, respectively. Combining the data from the two tests improved the overall predictive accuracy to only 75.0%. It is concluded that the routine performance of a symptom-limited test 6 to 8 weeks after infarction does not reveal any significant additional information in those patients who have undergone a predischarge low level exercise test. Thus the 6 to 8 week test should be restricted to selected patients after myocardial infarction.

Exercise testing: uses and limitations considering recent studies

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

Physician perception of exercise electrocardiography as a prognostic test after acute myocardial infarction

To determine how physicians interpret exercise electrocardiography with respect to prognosis after acute myocardial infarction (AMI), 29 cardiologists (all board certified) were presented a case history of a 50-year-old man with an uncomplicated AMI and asked to estimate the patient's risk of dying over the next year, the sensitivity and specificity of exercise electrocardiography with respect to 1-year mortality, and the patient's risk of dying given a positive and a negative test result. Each set of physician estimates did not differ from those derived from a review of the medical literature (difference not significant for each). Risk after the test was also calculated using the Bayes' theorem. Calculated versus estimated risks were compared after a negative (7 +/- 9 vs 11 +/- 11%) and a positive (27 +/- 22 vs 17 +/- 15%, differences not significant) test result. Estimated risks were more accurate for a negative result than for a positive one (89 +/- 10 vs 83 +/- 12%, p less than 0.001). Given a positive test result, 57% of the physicians recommended coronary angiography. However, their estimates of risk (30 +/- 23%) were not significantly different from the estimates of those physicians (14%) who recommended additional noninvasive testing (19 +/- 4%) or those (29%) who recommended medical therapy (28 +/- 26%) (difference not significant). Thus, cardiologists accurately estimated prognosis following AMI, but they were less accurate in assessing high risk than low risk, and their management decisions correlated poorly with their risk assessments.

Occurrence, characteristics and prognostic significance of early postacute myocardial infarction angina pectoris

To determine the incidence, clinical characteristics and prognostic significance of early spontaneous angina after acute myocardial infarction (AMI), the database involving the 867 participants of the Multicenter Post-AMI Program, who were followed for 1 to 4 years after AMI, was analyzed. Two hundred eighty-six patients (33%) had in-hospital postinfarction angina. During a mean follow-up of 31 months, patients with postinfarction angina were more frequently (p less than 0.001) hospitalized for cardiac causes and underwent coronary artery bypass graft surgery; however, their cardiac mortality rates at 1 year (8.4%) and at 4 years (14.3%) were not significantly different from those among patients without postinfarction angina (7.1 and 12.9%, respectively). The only anginal characteristic found to be associated with increased subsequent cardiac mortality (17.9% at 1 year, 39.2% at total follow-up) was high frequency angina (greater than or equal to 1 daily episodes). High frequency angina occurred in a small subset of 28 patients (3.2% of the study population, 9.8% of patients with postinfarction angina). Clinical variables representing higher grades of mechanical dysfunction and electrical instability after infarction were significantly more common among patients with high frequency angina than among those with low frequency angina. Cox survivorship analysis revealed that high frequency angina made a significant contribution to the risk of post-AMI cardiac death (hazard ratio 2.5, p = 0.01), which was independent of the effect of predischarge reduced radionuclide ejection fraction and Holter-recorded frequent or repetitive ventricular premature complexes.(ABSTRACT TRUNCATED AT 250 WORDS)

Which exercise test variables are of prognostic importance post-myocardial infarction?

The prognostic value of parameters noted on pre-discharge exercise testing was assessed in 300 survivors of acute myocardial infarction. Exercise testing was performed at a mean of 9 days post-infarction. Each patient's data were studied for the presence of ST-segment depression or elevation greater than or equal to 0.1 mV in any of the 12 leads recorded, angina pectoris, exertional hypotension and duration of exercise. The patients were followed for a mean of 12 months and the incidence of death, reinfarction, angina pectoris, heart failure and coronary revascularization procedures was noted. All variables studied, other than the presence of exercise-induced ST-segment elevation, were significantly associated with the occurrence of subsequent cardiac events (P less than 0.001). Exercise-induced ST-segment depression identified 80% of patients who developed complications and was significantly more sensitive than any of the other variables as a prognostic marker (P less than 0.05). The finding of angina pectoris, an abnormal blood pressure response or a limited exercise tolerance in association with exercise-induced ST-segment depression heightened the prognostic implications of this variable.

Exercise training after anterior Q wave myocardial infarction: importance of regional left ventricular function and topography

To determine whether the extent of left ventricular dysfunction and the degree of shape distortion can predict outcome in survivors of moderate-sized anterior Q wave myocardial infarction who are undergoing exercise training, these variables were measured by two-dimensional echocardiography before and after 12 weeks of a low level exercise training program starting 15 weeks after infarction in 13 patients (7 in group 1 and 6 in group 2) and 12 weeks apart in 24 matched control patients without training. By the end of training, the functional class score had increased in group 2 (from 2.25 to 2.67, p less than 0.005) but had not changed in group 1. Further discrimination of groups 1 and 2 was provided by an initial asynergy (akinesia or dyskinesia, or both) less than 18% or greater than or equal to 18%. Compared with group 1, group 2 had greater initial asynergy (32 versus 6%, p less than 0.001), expansion index (asynergic/normal endocardial segment length: 1.8 versus 1.6, p less than 0.025) and peak shape distortion index (12.2 versus 1.0 mm, p less than 0.005) but lower ejection fraction (43 versus 59%, p less than 0.05) and thinning ratio (asynergic/normal wall thickness: 0.61 versus 0.74, p less than 0.05). These variables did not change with training in group 1. However, in group 2, training caused significant increase in asynergy (from 32 to 40%, p less than 0.05), expansion index (from 1.8 to 2.0, p less than 0.01) and peak shape distortion (from 12.2 to 20.9 mm, p less than 0.05) associated with a decrease in thinning ratio (from 0.61 to 0.51, p less than 0.001) and ejection fraction (from 43 to 30%, p less than 0.005). Initial values for these variables were similar for corresponding control groups but did not change over the 12 weeks. Thus, patients with greater than or equal to 18% left ventricular asynergy on the initial echocardiogram showed more shape distortion, expansion and thinning before exercise training and developed further functional and topographic deterioration with training.

Predictors of non-fatal ischemic events after myocardial infarction

We characterize predictors of reinfarction and angina in 403 consecutive men aged 60 years or less who underwent heart catheterization within one month (18 +/- 6 days) after a qualifying myocardial infarction. Angiography showed obstructive lesions (greater than or equal to 50% diameter reduction) in 380 patients. One-, two- and three-vessel disease was found in 143 (36%), 139 (35%) and 98 (29%) patients, respectively. After 57 months of follow-up there were 60 deaths (12%), 41 patients (10%) sustained a new infarction and 210 (52%) had angina. Cox regression analysis selected the number of diseased vessels as the only independent 'predictor of reinfarction; independent predictors of angina were the number of diseased vessels and a history of angina prior to the qualifying infarction. Risk stratification showed the probability of reinfarction at 6 years to be significantly lower (P less than 0.001) in patients with one-vessel disease (12%) than in those with two- (30%) and three-vessel disease (37%). Similarly the probability of angina was also lower (P less than 0.001) in patients with one-vessel disease (51%) as compared to those with two- (72%) and three-(74%) vessel involvement. Thus multi-vessel disease is the main predictor of new non-fatal ischemic events after myocardial infarction.

Influence of long-term metoprolol treatment on early and late exercise test performance after acute myocardial infarction

The effect of therapy on exercise performance during a 3-year follow-up after acute myocardial infarction (AMI) was evaluated in a double-blind randomized comparison between 154 patients given metoprolol (100 mg twice daily) and 147 patients given placebo. Exercise tests were performed 1.5, 6, 12, 24 and 36 months after AMI. Maximal accomplished workloads were similar in the 2 groups throughout follow-up. Maximal heart rate was significantly higher in the placebo-treated group throughout the study (p less than 0.001). At the 6-week test more patients in the placebo group terminated exercise due to angina pectoris (40 vs 25%, p less than 0.05) and showed exercise-induced ST-depressions (38 vs 27%, p = 0.05) compared with the metoprolol group. Exercise-induced ventricular arrhythmias were significantly more common in the placebo group during the initial 6 months. Death, another AMI or both were significantly reduced by metoprolol treatment in patients with exercise-induced ST depression greater than or equal to 1 mm at the 6-week test. In a multiple logistic regression analysis maximal accomplished workload at 6 weeks (p less than 0.026), male sex (relative risk [rr] = 3.57, p = 0.016), previous AMI (rr = 3.07, p = 0.001), therapy with placebo (rr = 2.14, p = 0.007) and left ventricular failure (rr = 2.04, p = 0.023) were shown to carry independent prognostic information as well as exercise-induced ST-depression (greater than or equal to 1 mm) in placebo-treated patients (rr = 2.70, p = 0.01).

Death after acute myocardial infarction: interrelation between left ventricular dysfunction, arrhythmias and ischemia

Patients who survive an acute myocardial infarction face an increased risk of sudden death for approximately 6 months after hospital discharge; their prognosis is determined by the severity of their coronary arteriosclerosis and the degree of left ventricular dysfunction. Frequent ventricular premature complexes and evidence of ischemia either spontaneously or on treadmill are also markers for early morbidity and mortality in patients who are discharged from the hospital after acute myocardial infarction. The degree of left ventricular dysfunction is the strongest predictor of mortality; patients who have both left ventricular dysfunction, frequent premature ventricular beats and evidence of ischemia are at the highest risk of mortality after hospital discharge. It appears likely that all 3 of these risk factors interact and that therapy to reduce morbidity and mortality after myocardial infarction should aim at the amelioration of each of these risk factors. A model for the interaction of these risk factors is proposed and an approach to treatment for patients at high risk of mortality after hospital discharge after myocardial infarction is suggested.

Risk stratification after acute myocardial infarction by means of exercise two-dimensional echocardiography

To determine whether exercise two-dimensional echocardiography contributes to the prognostic information provided by exercise testing in patients recovering from acute myocardial infarction, 40 patients were prospectively studied by means of pre- and postexercise echocardiography 10 to 21 days after myocardial infarction. Patients were followed for 6 to 10 months or until one of the following clinical end points occurred: death, recurrent myocardial infarction, unstable angina, or coronary artery bypass grafting. Results of treadmill exercise tests were negative in 13 of 20 patients with good clinical outcome (65% specificity) and positive in 11 of 20 patients with poor clinical outcome (55% sensitivity). The resting echocardiogram was abnormal in 37 of 40 patients. The exercise echocardiogram was negative in 19 of 20 patients with good clinical outcome (95% specificity) and positive in 16 of 20 patients with poor clinical outcome (80% sensitivity). We conclude that exercise echocardiography is more sensitive and specific than treadmill exercise testing for predicting the occurrence of subsequent cardiac events after acute myocardial infarction.

Application of meta-analysis using an electronic spread sheet to exercise testing in patients after myocardial infarction

Decision analysis is being applied to medical practice in order to achieve cost efficacy in health care delivery. Critical to this process is establishing the diagnostic and prognostic accuracy of medical tests and the effectiveness of interventions. Meta-analysis is an approach that applies statistical methods to groups of studies in order to extract consensus results. Electronic spreadsheets facilitate meta-analysis with their ability to store, sort, graph, and mathematically manipulate both the methodologic approaches and clinical findings of seemingly disparate studies. As an example, this application is demonstrated with an analysis of studies that were performed to evaluate the prognostic value of exercise testing in patients recovering from a myocardial infarction. The following conclusions were reached: (1) patients excluded from exercise testing have the highest mortality; (2) only subsets of patients have been tested resulting in highly selected patient samples that make findings difficult to generalize; (3) of the five exercise test responses, only an abnormal systolic blood pressure response and a poor exercise capacity predicted risk more frequently than by chance; (4) submaximal or predischarge testing has greater predictive power than postdischarge or maximal testing; and (5) exercise-induced ST segment depression only appears to be predictive of increased risk in patients with inferior-posterior myocardial infarctions. This approach to combining studies is important since even careful analysis of a single study cannot elucidate all of the complex interactions and selective biases that have occurred. However, comparison of many heterogeneous studies is at best an arduous and time-consuming task. This approach to using electronic spreadsheets to collate and analyze multiple studies facilitates recognition of the population characteristics, clinical factors, and methodologic considerations that affect outcome and allows the quick inclusion of additional studies for re-analysis and interpretation.

Cost-effectiveness analysis of patient management alternatives after uncomplicated myocardial infarction: a model

Quantitative decision analyses provide a means whereby the effectiveness, in terms of patient outcome, and costs of diverse clinical approaches to the care of patients with cardiovascular disease can be made explicit and understandable. Increasingly, the profession is being required to justify the costs of clinical care to society, government and third party payers. Such justifications can be effectively presented when structured in decision analytic format. To demonstrate the utility of decision analysis and its extension--cost-effectiveness analysis--as a technique for presenting the rationale for clinical practices and technology utilization, the Cardiovascular Norms Committee of the American College of Cardiology sponsored a model cost-effectiveness analysis. Alternative management options, 6 month mortality and costs for the post-myocardial infarction patient were compared. The options included exercise electrocardiography, exercise thallium scintigraphy and coronary angiography, followed by coronary artery bypass surgery for patients with left main coronary disease only or patients with left main disease, three vessel disease or single or double vessel disease and a significant amount of myocardium in jeopardy. Within the constraints of the model, proceeding directly to angiography for risk stratification was the most effective approach, lowering expected mortality from 8% to approximately 3%. The marginal costs for this strategy, however, were high. The most cost-effective approach was to screen patients initially with exercise electrocardiography.

Prognostic significance of ventricular ectopic activity in survivors of acute myocardial infarction

Twenty-four hour ambulatory electrocardiography was performed on 3,290 survivors of acute myocardial infarction participating in the Beta-Blocker Heart Attack Trial (BHAT). History of myocardial infarction before the qualifying event, congestive heart failure and age were independently associated with the frequency and complexity of ventricular premature beats. Of the 1,640 patients randomized to placebo therapy, 163 died (76 suffered sudden death) during a 25 month average follow-up period. Ventricular ectopic activity was an independent predictor of total mortality after taking into consideration 16 other prognostic factors describing past history, risk factors, physical examination and laboratory investigations. Seven categoric definitions of ventricular ectopic activity predicted mortality, with similar odds ratios ranging from 2.27 to 2.69. A reciprocal relation of the sensitivity and specificity of each definition in predicting mortality was observed. Three clinical criteria (ST depression, cardiomegaly and prior infarction) allowed stratification of patients into four subsets with respective mortality rates of 35.5% (three criteria present), 19.0% (two criteria), 11.5% (one criterion) and 4.7% (none). Presence of ventricular ectopic activity (greater than or equal to 10 ventricular premature beats/h or pairs, ventricular tachycardia or multiform complexes) was associated with higher mortality rates in all four risk strata. The relative risk was higher (3.86) in the lowest risk stratum (mortality 2.4% without and 9.1% with ventricular ectopic activity). Thus, in survivors of acute myocardial infarction, ventricular ectopic activity was more pronounced in patients with prior myocardial infarction and congestive heart failure. It predicted mortality independently of other factors. Although mortality ratios were similar for all seven arrhythmia definitions, a reciprocal relation between sensitivity and specificity of the definitions in predicting mortality existed; ventricular ectopic activity was associated with increased mortality in all risk strata, but with a higher risk ratio in the numerically larger, low risk subset.

Relative prognostic value of rest thallium-201 imaging, radionuclide ventriculography and 24 hour ambulatory electrocardiographic monitoring after acute myocardial infarction

Rest thallium-201 scintigraphy, radionuclide ventriculography and 24 hour Holter monitoring are acceptable methods to assess myocardial necrosis, performance and electrical instability. This study examined the relative value of the three tests, when obtained a mean of 7 days after acute myocardial infarction, in predicting 1 year mortality in 93 patients. Planar thallium-201 images were obtained in three projections and were scored on a scale of 0 to 4 in 15 segments (normal score = 60). Patients were classified as having high risk test results as follows: thallium score less than or equal to 45 (33 patients), left ventricular ejection fraction less than or equal to 40% (51 patients) and complex ventricular arrhythmias on Holter monitoring (36 patients). During the follow-up of 6.4 +/- 3.4 months (mean +/- SD), 15 patients died of cardiac causes. All three tests were important predictors of survival by univariate Cox survival analysis; the thallium score, however, was the only important predictor by multivariate analysis. The predictive power of the thallium score was comparable with that of combined ejection fraction and Holter monitoring (chi-square = 21 versus chi-square = 22). Thus, rest thallium-201 imaging performed before hospital discharge provides important prognostic information in survivors of acute myocardial infarction which is comparable with that provided by left ventricular ejection fraction and Holter monitoring. Patients with a lower thallium score (large perfusion defects) are at high risk of cardiac death during the first year after infarction.

Usefulness of low-level exercise testing early after acute myocardial infarction in patients taking beta-blocking agents

The value of low-level exercise testing early after acute myocardial infarction (AMI) in 207 patients taking beta-blocking drugs was evaluated in a multicenter study of prognosis after AMI. After stratifying patients according to the absence of significant rales upon admission or pulmonary congestion on the admitting chest x-ray, the results of the exercise test (ability to complete the 9-minute protocol) permitted a large cohort (108 patients, 52% of exercising patients) with no deaths from cardiac causes in the year after AMI to be identified. The results suggest that even in patients taking beta-blocking agents, low-level exercise testing together with clinical stratification has value in identifying a large group of patients with a good prognosis after AMI.

Significance of abnormal blood pressure response during exercise-induced myocardial dysfunction after recent acute myocardial infarction

The relation between exercise left ventricular ejection fraction and blood pressure (BP) responses after an acute myocardial infarction (AMI) was investigated. Twenty-eight to 37 days after an uncomplicated AMI, 224 consecutive patients underwent exercise radionuclide angiography in the 40 degrees semisupine position. In 180 patients (group A, 80%), BP increased more than 5 mm Hg every stage; in 44 patients, BP responses were abnormal; in 33 (group B, 15%), BP did not increase during 2 stages; in 11 (group C, 5%), it decreased more than 5 mm Hg after an initial increase. Ejection fraction did not differ significantly among the 3 groups at rest (51 +/- 13 in group A, 50 +/- 18 in group B, 47 +/- 13 in group C [difference not significant]) or at peak exercise (51 +/- 16% in group A, 46 +/- 19% in group B, and 43 +/- 16% in group C, [difference not significant]). Exercise-induced left ventricular failure or hemodynamic decompensation occurred in 22 patients. In these patients, ejection fraction at rest was 44 +/- 19% and decreased to 35 +/- 16% (p less than 0.05) with exercise. Only 9 of these patients (41%) had abnormal BP responses, with the other 13 (59%) showing a normal BP responses. The The 35 patients with abnormal BP responses in the absence of hemodynamic decompensation were asymptomatic, terminating exercise because of fatigue. The ejection fraction at rest and during exercise in these patients was similar to that in patients with normal BP responses.(ABSTRACT TRUNCATED AT 250 WORDS)

Prognostic value of predischarge 12 lead electrocardiogram after myocardial infarction compared with other routine clinical variables

The prognostic value of QRS score (Selvester), ST depression, ST elevation, extrasystoles, P terminal force in V1, and QTc derived from the predischarge 12 lead electrocardiogram was assessed after myocardial infarction in 474 patients without intraventricular conduction defects, ventricular hypertrophy, or atrial fibrillation. The usefulness of these results in risk assessment was compared with that of other clinical data. During follow up 45 patients died. Logistic regression analysis showed that QRS score, ST depression, and QTc were independently predictive of cardiac mortality. When multivariate analysis was applied to clinical and electrocardiographic data together, however, the 12 lead electrocardiogram did not provide independent information additional to that provided by other routine clinical findings and laboratory tests such as a history of previous myocardial infarction, clinical signs of persistent heart failure, indication for digitalis or antiarrhythmic drugs at discharge, and enlarged heart on chest x ray. In conclusion, the electrocardiogram has important prognostic value; however, it is not powerful enough to further improve the risk assessment of post-infarction patients.

Prediction of 1-year outcome after complicated and uncomplicated myocardial infarction: Bayesian analysis of predischarge exercise test results in 300 patients

After myocardial infarction (MI), the additive prognostic value of exercise variables to clinical variables has been questioned. The merits of a symptom-limited predischarge exercise test were therefore evaluated in clinically defined subgroups of patients. Exercise tests were consecutively performed by 208 survivors of uncomplicated MI (no heart failure, postinfarction angina, recurrent infarction, or late arrhythmias) and by 92 survivors of complicated MI. After uncomplicated MI (1-year mortality rate 4%), an achieved workload greater than 70% of age-predicted maximum identified 145 patients at very low risk (predictive value for survival 98%). After complicated MI (1-year mortality rate 13%), an exaggerated heart rate response was the best predictor of outcome, but had low (92%) predictive value of survival at 155 bpm. It is concluded that stress testing has only limited value after complicated MI. After uncomplicated MI, exercise variables are extremely helpful in identifying patients at very low risk in whom further investigations are not warranted.

Prognostic significance of the treadmill exercise test performance 6 months after myocardial infarction

A submaximal treadmill exercise test performed before hospital discharge after an uncomplicated myocardial infarction is often utilized to estimate prognosis and guide management, but there is little experience with a maximal exercise test performed 6 months after infarction to identify prognosis later in the convalescent period. The performance characteristics during an exercise test 6 months after myocardial infarction were related to the development of death, recurrent nonfatal myocardial infarction and coronary artery bypass surgery in the subsequent 12 months (that is, 6 to 18 months after infarction) in 473 patients. Mortality was significantly greater in patients who exhibited any of the following: inability to perform the exercise test because of cardiac limitations, the development of ST segment elevation of 1 mm or greater during the exercise test, an inadequate blood pressure response during exercise, the development of any ventricular premature depolarizations during exercise or the recovery period and inability to exercise beyond stage I of the modified Bruce protocol. By utilizing a combination of four high risk prognostic features from the exercise test, it was possible to stratify patients in terms of risk of mortality, from 1% if none of these features were present to 17% if three or four were present. Recurrent nonfatal myocardial infarction was predicted by an inability to perform the exercise test because of cardiac limitations, but not by any characteristics of exercise test performance. Coronary artery bypass surgery was associated with the development of ST segment depression of 1 mm or greater during the exercise test. Although clinical evidence of angina and heart failure 6 months after infarction was predictive of subsequent mortality among all survivors, among the low risk group without severely limiting cardiac disease, the exercise test provided unique prognostic information not available from clinical assessment alone. Therefore, a maximal exercise test performed 6 months after myocardial infarction is a valuable, noninvasive tool to evaluate prognosis. It provides information that is independent of and additive to clinical evaluation performed at the same time.

Prognostic information from early post-infarction exercise testing

Early post-myocardial infarction exercise testing has proved surprisingly safe. S-T elevations portended a bad prognosis as did also marked S-T segment depressions, especially if combined with premature ventricular contractions or short duration of exercise. A poor prognosis was also seen if, at low workloads, blood pressure could not reach 130 mm Hg, the heart rate did not rise above 130 beats per minute, or if there was angina. Complex arrhythmias were only of prognostic value as an independent variable with ambulatory monitoring. Negative findings were of more predictive value than positive results and have important therapeutic implications.

Relative value of clinical variables, bicycle ergometry, rest radionuclide ventriculography and 24 hour ambulatory electrocardiographic monitoring at discharge to predict 1 year survival after myocardial infarction

The relative value of predischarge clinical variables, bicycle ergometry, radionuclide ventriculography and 24 hour ambulatory electrocardiographic monitoring for predicting survival during the first year in 351 hospital survivors of acute myocardial infarction was assessed. Discriminant function analysis showed that in patients eligible for stress testing the extent of blood pressure increase during exercise slightly improved the predictive accuracy beyond that of simple clinical variables (history of previous myocardial infarction, persistent heart failure after the acute phase of infarction and use of digitalis at discharge), whereas radionuclide ventriculography and 24 hour electrocardiographic monitoring did not. The predictive value for mortality was 12% with clinical variables alone and 15% with the stress test added. Radionuclide ventriculography and 24 hour electrocardiographic monitoring were slightly additive to clinical information in the whole group of patients independent of the eligibility for stress testing (predictive value for mortality 24% with clinical variables alone and 26% with radionuclide ejection fraction and 24 hour electrocardiographic monitoring added). It is concluded that the appropriate use of simple clinical variables and stress testing is sufficient for risk stratification in postinfarction patients, whereas radionuclide ventriculography and 24 hour electrocardiographic monitoring should be limited to patients not eligible for stress testing.