Role of exercise testing early after myocardial infarction in identifying candidates for coronary surgery

Post-myocardial infarction exercise testing: clinical significance of a left ventricular function index and ventricular arrhythmias. A prospective study

A predischarge exercise test was performed in a prospective series of 187 patients, less than 70 years old, with acute myocardial infarction. A survival analysis confirmed previous retrospective findings of a significantly increased long-term mortality in patients with a low increase in the pressure-rate-product (PRP) and/or with major exercise-induced arrhythmias. ST segment depression was without prognostic significance. By a graduated, quantitative re-evaluation of the significance of exercise-induced ventricular arrhythmias, an appropriate, significantly discriminating cutoff point for the frequency of solitary ventricular premature beats (VPBs) was found at two or more VPBs/min. Repetitive VPBs had an equal significance. The probability of 4.5-year survival in patients with these arrhythmias and a low increase in PRP was 0.49 vs. 0.85 in patients with less frequent arrhythmias and with a high increase in PRP (p less than 10(-6)).

Detection of multivessel disease post myocardial infarction using an exercise-induced QRS score

OBJECTIVE

The aim of this study was to investigate the ability of Athens QRS score values to detect stenoses in other coronary arteries than the obstructed ones (which caused the myocardial infarction [MI]) in patients with a history of MI.

METHODS

We studied 125 patients (93 males and 32 females, mean age 54 +/- 7 years [range 45-68 years]) with a history of MI (46 patients with anterior MI, 54 patients with inferior MI, 25 patients with lateral MI). All patients underwent treadmill exercise testing and coronary arteriography.

RESULTS

Athens QRS score values were inversely related to the extent of CAD: -0.5 +/- 0.3 mm for patients with 1-VD (obstructed vessel), -3.4 +/- 2.2 mm for patients with 2-VD (obstructed vessel and stenosis in another vessel), and -5 +/- 1.8 mm for patients with 3-VD (obstructed vessel and stenoses in two more vessels). The ROC curves for the detection of multivessel disease showed that the area under the curve for QRS score values < -3 mm is significantly higher than the curve for ST-segment depression > or = 1 mm (0.948 vs 0.792, P < 0.001).

CONCLUSIONS

Values of the Athens QRS score less than -3 may distinguish single- from multivessel coronary artery disease in patients with a history of MI.

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 myocardial perfusion imaging: state of the art and new developments

Although the prognostic value of myocardial perfusion imaging is now well established, new data have continued to expand its role in the management of patients. This review addresses the current state-of-the-art and new developments in the use of myocardial perfusion imaging for determining cardiac risk and integrating such information into patient care.

Prognostic significance of maximal exercise testing after myocardial infarction treated with thrombolytic agents: the GISSI-2 data-base. Gruppo Italiano per lo Studio della Sopravvivenza Nell'Infarto

Exercise testing helped in diagnosing postinfarction patients in the prethrombolytic era. Over the past decade acute myocardial infarction treatment has changed because of new thrombolytic therapies and consequently, the value of exercise testing is under debate. The GISSI-2 database allowed us to reevaluate the prognostic role of exercise testing in thrombolysed patients. The exercise test was performed in 6296 patients, on average 28 days after randomisation. The test was not performed in 3923 patients because of contraindications. The test was judged positive for residual ischaemia in 26% of the patients, negative in 38%, and non-diagnostic in 36%. Among the patients with a positive stress test result, 33% had symptoms, whereas 67% had silent myocardial ischaemia. The mortality rate was 7.1% among patients who did not have an exercise test and 1.7% [correction of 7.1%] for those with a positive test, 0.9% for those who had a negative test, and 1.3% for those who did not have a diagnostic test. In the adjusted analysis, symptomatic induced ischaemia, submaximal positive result, low work capacity, and abnormal systolic blood pressure were independent predictors of 6-month mortality (relative risks [RR] 2.54, 95% CI 1.27-5.08, 2.28, 1.17-4.45, 2.05, 1.23-3.42, and 1.86, 1.05-3.31, respectively). However, when these factors were tested simultaneously, only symptomatic induced ischaemia and low work capacity were confirmed as independent predictors of mortality (RR Cox 2.07, 95% CI 1.02-4.23 and 1.78, 1.06-2.99, respectively). Patients with a normal exercise response have an excellent medium-term prognosis and do not need further investigation. However, more evaluation should be devoted to the patients who cannot undergo exercise testing, because the potential to influence outcome appears to be much greater.

Prognostic significance of transient myocardial ischaemia after first acute myocardial infarction: five year follow up study

OBJECTIVE

To assess the five year prognostic significance of transient myocardial ischaemia on ambulatory monitoring after a first acute myocardial infarction, and to compare the diagnostic and long term prognostic value of ambulatory ST segment monitoring, maximal exercise testing, and echocardiography in patients with documented ischaemic heart disease.

DESIGN

Prospective study.

SETTING

Cardiology department of a teaching hospital.

PATIENTS

123 consecutive men aged under 70 who were able to perform predischarge maximal exercise testing.

INTERVENTIONS

Echocardiography two days before discharge (left ventricular ejection fraction), maximal bicycle ergometric testing one day before discharge (ST segment depression, angina, blood pressure, heart rate), and ambulatory ST segment monitoring (transient myocardial ischaemia) started at hospital discharge a mean of 11 (SD 5) days after infarction.

MAIN OUTCOME MEASURES

Relation of ambulatory ST segment depression, exercise test variables, and left ventricular ejection fraction to subsequent objective (cardiac death or myocardial infarction) or subjective (need for coronary revascularisation) events.

RESULTS

23 of the 123 patients had episodes of transient ST segment depression, of which 98% were silent. Over a mean of 5 (range 4 to 6) years of follow up, patients with ambulatory ischaemia were no more likely to have objective end points than patients without ischaemic episodes. If, however, subjective events were included an association between transient ST segment depression and an adverse long term outcome was found (Kaplan-Meier analysis; P = 0.004). The presence of exercise induced angina identified a similar proportion of patients with a poor prognosis (Kaplan-Meier analysis; P < 0.004). Both exertional angina and ambulatory ST segment depression had high specificity but poor sensitivity. The presence of exercise induced ST segment depression was of no value in predicting combined cardiac events. Indeed, patients without exertional ST segment depression were at increased risk of future objective end points (Kaplan-Meier analysis; P < 0.0045). These findings may be explained in part by a higher prevalence of left ventricular dysfunction in patients without ischaemic changes in the exercise electrocardiogram (P < 0.05).

CONCLUSION

There seem to be limited reasons to perform ambulatory ST segment monitoring in survivors of a first myocardial infarction who can perform exercise tests before discharge. Patients at high risk of future myocardial infarction or death from cardiac causes are not identified. Ambulatory monitoring and exertional angina distinguish a small subset of patients who will develop severe angina pectoris demanding coronary revascularisation during follow up. Patients without exercise induced ST segment depression comprise a high risk subgroup in terms of subsequent objective end points. The role of ambulatory ST segment monitoring performed in unselected patients immediately after infarction when risk is maximal remains to be clarified.

Management of patients after their first myocardial infarction

In the past 20 years there has been a steady improvement in the short term prognosis of patients with myocardial infarction, following the introduction of beta blockers, thrombolysis, and aspirin. Patients treated with thrombolytic drugs have a lower overall mortality after myocardial infarction but remain at risk of non-fatal reinfarction or death, and in one study almost half of all survivors of acute myocardial infarction died or suffered a further ischaemic event within three years. It is therefore important to have a strategy to identify patients at high risk, to reduce the subsequent development of cardiac failure and mortality, and to have effective measures for secondary prevention to reduce the incidence of reinfarction as well as to promote rehabilitation.

Prognostic significance of peak exercise capacity in patients with coronary artery disease

OBJECTIVES

The aim of this study was to investigate the prognostic significance of peak oxygen uptake in patients with coronary artery disease who had an exercise test that could be sustained to exhaustion without limiting symptoms.

BACKGROUND

Many studies have reported an inverse association between the level of exercise reached during a stress test and mortality or cardiovascular morbidity. These studies have used submaximal or symptom-limited exercise testing in patients with a recent myocardial infarction.

METHODS

Peak oxygen uptake was measured in male patients > or = 4 weeks after myocardial infarction (312 patients) or coronary artery surgery (215 patients) by use of a graded uninterrupted exercise test performed to exhaustion. Apart from peak oxygen uptake, several risk factors for cardiovascular disease, patient and exercise characteristics and drug treatment were considered in the Cox proportional hazards model.

RESULTS

During the total follow-up period of 3,213 patient-years, 53 patients died. Of these 53 patients, 33 died of cardiovascular causes. All-cause and cardiovascular mortality decreased with increasing peak oxygen uptake, even after adjustment for significant covariates. The relative hazard rates of 0.43 and 0.29 indicate that a hypothetic increase in peak oxygen uptake by 1 liter/min could be associated with decreases in all-cause and cardiovascular mortality of 57% and 71%, respectively.

CONCLUSIONS

Exercise capacity is an independent predictor for subsequent all-cause and cardiovascular mortality in patients able to perform an exercise test until exhaustion.

Comparison of symptom-limited and low level exercise tolerance tests early after myocardial infarction

OBJECTIVES

This study was conducted to determine the diagnostic yield and risks of a symptom-limited treadmill exercise test before hospital discharge.

BACKGROUND

Currently, predischarge low level and 6-week symptom-limited exercise treadmill tests are recommended for risk stratification after myocardial infarction. However, few data exist on the safety and value of a predischarge symptom-limited exercise test.

METHODS

We utilized a modified Bruce protocol starting at 1.7 mph and 0 grade with 3-min stages in 150 consecutive patients 6.4 +/- 3.1 days after myocardial infarction. Each exercise test was interpreted for duration, symptoms and ST segment changes at the low level (70% of predicted heart rate) and symptom-limited end point.

RESULTS

There were no complications related to the symptom-limited exercise tests. The test results were positive in only 23% of the patients at the low level end point, but were positive in 40% of the patients at the later symptom-limited end point (p < 0.001). During a mean follow-up period of 15 +/- 5 months in 138 patients (92%), 50 patients (36%) had a cardiac event. Of the patients with a cardiac event, significantly more (p < 0.001) had a positive exercise test at the symptom-limited end point (31 vs. 16 patients). Five patients with a negative and 14 patients with a nondiagnostic symptom-limited exercise test had an event.

CONCLUSIONS

In patients with uncomplicated myocardial infarction, we demonstrated the safety of an early symptom-limited treadmill exercise test. Symptom-limited exercise tests will identify more patients with inducible ischemia who are at risk of future cardiac events and who may benefit from early intervention.

First myocardial infarction in patients under 60 years old: the role of exercise tests and symptoms in deciding whom to catheterise

OBJECTIVE

To determine the role of exercise tests and assessment of angina in the detection of potentially threatening disease in young patients with infarcts.

DESIGN

Elective readmission of patients at a mean (SD) of 60 (30) days after acute myocardial infarction for assessment of angina, treadmill exercise tests, and cardiac catheterisation.

SETTING

Cardiology department of a teaching hospital.

PATIENTS

186 consecutive survivors, aged under 60 years and discharged from the coronary care unit after a first myocardial infarction.

MAIN OUTCOME MEASURES

Coronary arteriography, presence of angina, result of exercise tests, and referral for revascularisation.

RESULTS

31% of patients had either two vessel disease (with proximal left anterior descending involvement), three vessel disease, or left main stem disease. 49% of all patients had angina. Of the 173 patients who had an exercise test 34% had 1 mm and 24% had 2 mm of exercise induced ST depression. Thirty percent had no angina and a negative exercise test: after a mean (SD) follow up of 16 (4) months none of this symptom free sub-group had died, had experienced a further myocardial infarction, or had been referred for revascularisation. 79% of patients with either two vessel disease (with proximal left anterior descending involvement), three vessel disease, or left main stem disease had either angina or a 1 mm ST depression during the exercise test.

CONCLUSION

Patients without cardiac pain after myocardial infarction and without ST changes during an exercise do not need arteriography.

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)

Transient myocardial ischemia after a first acute myocardial infarction and its relation to clinical characteristics, predischarge exercise testing and cardiac events at one-year follow-up

The relation between early out-of-hospital ambulatory ST-segment monitoring, clinical characteristics, predischarge maximal exercise testing and cardiac events was determined in 123 consecutive men (age 55 +/- 8 years) with a first acute myocardial infarction (AMI). During 36 hours of ambulatory recording 11 +/- 5 days after AMI 23 patients (19%) had 123 ischemic episodes (group 1), whereas 100 patients demonstrated no ischemia (group 2). Exercise-induced ST-segment depression was more prevalent in group 1 (83%) than in group 2 (47%) (p < 0.005). Group 1 patients also had more severe ischemia as judged from a shorter exercise duration before significant ST-segment depression (5.5 +/- 2.4 vs 7.7 +/- 4.1 minutes; p < 0.03) and more pronounced ST-segment depression on exercise testing (4.1 +/- 2.6 vs 2.6 +/- 1.6 mm; p < 0.03). Furthermore, exercise test results revealed an impaired hemodynamic response in group 1 compared with group 2: systolic blood pressure at maximal work load 160 +/- 31 vs 176 +/- 28 mm Hg (p < 0.025) and systolic blood pressure increase during exercise 41 +/- 24 vs 56 +/- 22 mm Hg (p < 0.01). With-in 368 +/- 8 days of follow-up the frequency of cardiac events (cardiac death, nonfatal reinfarction, and severe angina including the need of revascularization) was 52% in group 1 compared with 22% in group 2 (p < 0.01). Exercise-induced ischemia did not predict an adverse outcome: event rate 30 vs 25% in patients without residual ischemia (p = NS).(ABSTRACT TRUNCATED AT 250 WORDS)

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.

Early exercise test in acute myocardial infarction treated with intravenous streptokinase

The aim of this study was to assess the value of the early exercise test (ET) in patients with acute myocardial infarction (AMI) treated with IV streptokinase (SK). The authors studied 70 patients with first AMI; 31 were treated with SK and 39 were not. Before discharge everyone was given early exercise up to 5-6 METs and catheterized within 22.9 +/- 7.2 days. There was no significant difference in the number of positive ETs between the two groups (11/31 and 14/39 respectively). There was significant difference in favor of: (1) the recanalization of the infarct-related artery in the SK group, (2) the negative ET in patients with recanalized vessels in both groups, (3) the positive ET in patients with multi-vessel coronary disease. It is concluded that the results of early ET in patients with AMI are related to the recanalization of the infarct-related artery and the coexistence of multi-vessel coronary artery disease, regardless of SK treatment. Patients with successful thrombolysis have negative ET more frequently.

Predischarge maximal exercise test identifies risk for cardiac death in patients with acute myocardial infarction

A maximal exercise test was performed in 54 patients with acute myocardial infarction (AMI) before discharge and in 49 age-matched control subjects. The long-term prognosis was assessed after an average follow-up of 7.6 years in AMI patients and 5.8 years in control subjects. The maximal work capacity and systolic blood pressure increase in AMI patients was 59% that of control subjects (p less than 0.001). Seventeen AMI patients had significant ST-segment shifts, 13 with ST depression and 4 with ST elevation. In AMI patients experiencing a cardiac death during follow-up the maximal work capacity and systolic blood pressure increase were significantly lower than in survivors and those who died from noncardiac reasons (p less than 0.01; p less than 0.05), with no difference between these groups in the number of patients with ST-segment shifts. The average maximal work capacity of control subjects was 143 watts. A maximal work capacity half this (less than or equal to 72 watts) predicted long-term mortality in AMI patients (p less than 0.001). In addition a low increase in systolic blood pressure (less than 30 mm Hg) also predicted long-term mortality (p less than 0.005), whereas ST shifts were of no significant value. In this study maximal work capacity turned out to be the best single exercise variable for identifying groups of AMI patients with very low and relative high risk of cardiac death. When all 3 exercise variables were combined, the predischarge maximal exercise test was of great value in identifying AMI patients at low risk for cardiac death (predictive value of a negative test: 95%).

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 soon after myocardial infarction: its relation to course and outcome at one year in patients aged less than 55 years

A consecutive series of 184 patients aged less than 55 years who had an acute myocardial infarction were enrolled in a study to examine outcome at one year. One hundred of these patients underwent a maximal exercise test six weeks after infarction to evaluate its ability to predict cardiac events. The in-hospital mortality for the series was 7.6% (14 deaths) and the one year mortality for the 170 survivors was 3.8% (seven deaths). During the exercise test 31 patients had angina and 21 had ST depression. During the one year follow up period 39 of 100 patients had angina on exertion, 15 patients underwent coronary artery surgery, three patients had a reinfarction, and one patient died. Angina during the exercise test but not ST segment depression during the exercise test predicted angina on exertion and the need for coronary artery surgery. In the year of follow up angina occurred during everyday exertion in 25 (81%) (95% confidence interval 62 to 92%) of the 31 patients who developed angina during the exercise test and in only 14 (20%) (95% confidence interval 12 to 32%) of 69 patients who did not, and coronary artery surgery was performed in 11 (35%) (95% confidence interval 19 to 54%) of the 31 patients with angina during the exercise test and only four (6%) (95% confidence interval 2 to 15%) of 69 patients without angina. The outcome after myocardial infarction in patients aged less than 55 years was good and the occurrence of angina, but not ST segment depression, during a maximal exercise test six weeks after infarction was an indication for further investigation.

Relative power of clinical, exercise test, and angiographic variables in predicting clinical outcome after myocardial infarction: the Newham and Tower Hamlets study

The interrelations of clinical, exercise test, and angiographic variables and their relative values in predicting specific clinical outcomes after myocardial infarction have not been fully established. Of 302 consecutive stable survivors of infarction, 262 performed a predischarge submaximal exercise test. In the first year after infarction patients with a "positive" exercise test were 13 times more likely to die, 2.8 times more likely to have an ischaemic event, and 2.3 times more likely to develop left ventricular failure than patients with negative tests. Patients with positive exercise tests underwent cardiac catheterization. Features of the history, 12 lead electrocardiogram, in-hospital clinical course, exercise test, and left ventricular and coronary angiograms that predicted these clinical end points were identified by univariate analysis. Then multivariable analysis was used to assess the relative powers of all variables in predicting end points. Certain features of the exercise test remained independent predictors of future ischaemic events and the development of overt left ventricular failure, but clinical and angiographic variables were more powerful predictors of mortality. Because the exercise test is also used to select patients for angiography, however, the results of this study strongly support the use of early submaximal exercise testing after 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)

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.

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.

Prognostic stratification of patients after myocardial infarction

An attempt was made to stratify risk of subsequent cardiac events in post-infarct patients according to a combination of the results of clinical assessment, routine diagnostic investigations, and pre-discharge exercise testing in 350 consecutive patients who were followed up for one year. Patients were classified prospectively on the basis of the extent of myocardial damage as assessed by peak enzyme release, reciprocal change on the electrocardiogram at the time of myocardial infarction, Norris prognostic index, ability to perform a pre-discharge exercise test (and test result), and ability to tolerate beta adrenergic blockade on discharge. Of the 50 patients with contraindications to pre-discharge exercise testing, 26% died or had reinfarctions compared with 9% of the 300 exercised patients; the 24 non-exercised patients with evidence of extensive myocardial damage or reciprocal changes on the electrocardiogram were particularly at risk. Similarly, among the 300 exercised patients, extensive myocardial damage, reciprocal change on the electrocardiogram, and ST depression on exercise testing were the major risk markers in that each identified at least 75% of the patients who had subsequent cardiac events. The 63 exercised patients who had all three of these major risk markers constituted a high risk group: 18 (29%) died or had reinfarction. Of the remaining 237 patients, only 9 (4%) had cardiac events. The 35 high risk patients with exercise induced angina pectoris or clinical contraindications to beta blockade were particularly at risk; 15 (43%) died or had reinfarction. This approach to risk stratification identified a small cohort of high risk patients in a large population of myocardial infarction survivors; it also identified a large group with a very low risk of subsequent cardiac events.

Accurate detection of triple vessel disease in patients with exercise induced ST segment depression after infarction

The severity of coronary artery disease is an important determinant of prognosis after acute myocardial infarction. The ability of a symptom limited exercise test to predict the presence of triple vessel disease was assessed in 221 patients three weeks after infarction. Coronary angiography was performed in patients with exercise induced ST segment depression. The presence of ST segment depression alone was poorly indicative of triple vessel disease; however, some specific features of ST segment changes on exercise were of predictive value. Downsloping ST segment configuration alone or horizontal ST segment depression associated with an early onset and a late recovery time after exercise correctly identified 30 (90%) of 33 patients with triple vessel disease whereas it incorrectly identified only 6 (15%) of 39 patients with single and double vessel disease. An abnormal blood pressure response was also predictive. In patients with ST segment depression after infarction triple vessel disease can be detected accurately by a combination of the electrocardiographic and haemodynamic variables attained on exercise.

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.

Exercise testing early after myocardial infarction: historic perspective and current uses

Exercise testing performed earlier than six weeks post-MI is accepted as "standard" medical practice. Although both heart rate-limited and symptom-limited exercise protocols are used with nearly equal frequency, the latter appears more valuable because the prognostic yield is greater without sacrificing patient safety. Treadmill or cycle ergometers are the preferred modes of testing because of higher exercise work loads imposed and increased sensitivity and specificity of results. The physiologic exercise responses to graded work loads among these acute MI survivors include a mean maximal heart rate range of 118 to 136 beats/min, a peak systolic blood pressure between 137 and 170 mmHg, a mean peak double product from 16,000 to 22,400, and a mean maximal work load between 4.8 and 7.0 METS. Exercise findings which are most clinically useful are greater than 1 mm ST segment depression from rest level, presence of angina pectoris during exercise, decrease in systolic blood pressure with increasing work, presence of complex or frequent VEBs, and exercise tolerance less than 4 METS. These exercise findings identify, in recent post-MI survivors, groups of patients that have significantly different estimated future cardiac morbidity and mortality rates. The most consistent indices of multi-vessel coronary heart disease are ST segment depression, angina pectoris, and poor exercise tolerance. The most important role of stress testing in this period post-MI is identification of individuals who urgently need evaluation for coronary bypass surgery. In addition to risk stratification, exercise testing provides valuable information regarding exercise prescription for cardiac rehabilitation, direct psychologic benefit for resuming an active lifestyle, and motivation for exercise participation. Although safety of the early post-MI stress test has not been systematically studied, reports from individual studies indicated low morbidity and mortality. Attesting to this is the frequency with which it is performed as a routine office procedure. Finally, there has been a growing use of this procedure not only among cardiologists but also among internists and family practice physicians.

Low-level exercise testing after myocardial infarction. A useful guide to management

Low-level exercise testing after acute myocardial infarction can be safely performed in the early recovery period before hospital discharge. It is a clinically useful procedure and has the following benefits. It identifies patients at high risk for recurrent acute coronary events within one year after acute myocardial infarction, permits evaluation of the effectiveness of drug therapy before hospital discharge, allows selection of patients for early coronary arteriography, and provides guidelines for activity in the immediate postinfarction period.

Post-infarction exercise testing in patients under 55 years. Relation between ischaemic abnormalities and the extent of coronary artery disease

Previous studies have suggested that the early post-infarction exercise test is useful in predicting the extent of coronary artery disease. The results of a heart rate limited exercise test three weeks after infarction and a symptom limited exercise test six weeks after infarction obtained by both standard lead electrocardiograms and 16 lead precordial maps were compared in 100 consecutive survivors of acute myocardial infarction under 55 years of age. Exercise tests were defined as being positive on the basis of angina, ST segment depression greater than or equal to 1 mm in any electrocardiogram lead, or exertional hypotension. Multivessel disease, that is two or three vessel disease, was present in 60 patients, and three vessel disease in 22 patients. The sensitivity, specificity, and predictive value for multivessel disease of the three week test were 38%, 83%, and 76% respectively; and results for the six week test were 55%, 75%, and 77% respectively. Only 32% of patients with three vessel disease were identified at the three week test, and 59% at the six week test. Significantly more patients with multivessel and three vessel disease were identified by the symptom limited six week test. Precordial mapping offered no advantages over the standard 12 lead electrocardiogram in either the identification of patients with multivessel disease or the prediction of the distribution of coronary artery disease. Angina pectoris during the exercise test at six weeks was the single most useful predictor of multivessel disease. Multivessel disease was found in 27 (87%) of the 31 patients with angina with or without ST depression during the test at six weeks compared with 33 (48%) of the 69 patients who did not have angina during the test at six weeks. Exercise testing in the early post-infarction period in patients under 55 years of age is of limited value in predicting the extent of coronary artery disease. It is, therefore, unreasonable to use such exercise tests to select patients for coronary arteriography after myocardial infarction. None the less angina pectoris occurring during a symptom limited exercise test six weeks after infarction is a strong predictor of multivessel disease, and coronary arteriography is recommended in these patients.

Stress testing predischarge and six weeks after myocardial infarction to compare submaximal and maximal exercise predischarge and to assess the reproducibility of induced abnormalities

Submaximal and maximal treadmill exercise tests were performed predischarge in 64 patients after acute myocardial infarction to assess the relative yield of residual ischaemic abnormalities. The reproducibility of individual abnormalities resulting from maximal stress tests performed predischarge and 6 weeks after infarction was also assessed in 55 of these patients. Compared with predischarge submaximal exercise testing, a maximal exercise test identified a significantly greater number of patients with residual myocardial ischaemia (26 vs. 15, P less than 0.05) and this was associated with a significantly longer average maximal exercise duration (P less than 0.001), and a higher rate-pressure product (P less than 0.001). Among the 55 patients who had maximal stress tests both predischarge and 6 weeks after infarction, there was a significant lack of reproducibility in the occurrence of exercise induced angina (P less than 0.01) and an abnormal blood pressure response (P less than 0.02). In contrast, exercise induced ST segment depression and elevation and ventricular arrhythmias were relatively reproducible. More patients had an ischaemic test result (ST depression or angina) at the later test compared to the predischarge test (33 vs. 25 patients) but this increase was not statistically significant. There were, however, significant increases at the later test in mean maximal exercise duration (P less than 0.001). mean maximal heart rate (P less than 0.001) and heart rate-systolic blood pressure double product (P less than 0.001). The majority of patients who had a cardiac event in the period between the two tests had a predischarge test abnormality. We conclude that a significantly greater number of patients with residual reversible myocardial ischaemia after infarction will be identified by symptom limited exercise testing compared with a submaximal predischarge test. Because ST depression and elevation appear reproducible, patients who develop these abnormalities during a predischarge test do not, for prognostic reasons, need retesting 6 weeks after infarction. Exercise induced angina pectoris and an abnormal blood pressure response, however, are highly variable and in these patients a repeat test may be useful.

Prediction of mortality during the first year after acute myocardial infarction from clinical variables and stress test at hospital discharge

The predictive value of a predischarge symptom-limited stress test was studied in 405 consecutive survivors of acute myocardial infarction (AMI). Three hundred patients performed bicycle ergometry; 105 could not perform it. Among these latter 105 patients, the stress test was contraindicated in 43 because of angina or heart failure and in 62 because of noncardiac limitations. One-year survival was 44% in the "cardiac-limited" group (19 of 43) and 92% in the "non-cardiac-limited" group (57 of 62). One-year survival among the patients who performed an exercise test at discharge was 93% (280 out of 300). The best stress test predictor of mortality by univariate analysis was the extent of blood pressure (BP) increase: 42 +/- 24 mm Hg in 280 survivors vs 21 +/- 14 mm Hg in 20 nonsurvivors (p less than 0.001). Among the 212 patients in whom BP increased 30 mm Hg or more, mortality was 3% (n = 6), while it was 16% (n = 14) among the 88 patients in whom BP increased less than 30 mm Hg. Angina, ST changes and arrhythmias were not as predictive. Stepwise discriminant function analysis showed inadequate BP increase to be an independent predictor of mortality. A high-risk group can be identified at discharge on clinical grounds in patients unable to perform a stress test, whereas intermediate- and low-risk groups can be identified by the extent of BP increase during exercise.

Low-level exercise testing after myocardial infarction: usefulness in enhancing clinical risk stratification

Of 866 patients enrolled in our multicenter study, 667 performed a low-level exercise test early after myocardial infarction, most before discharge. Excluding seven patients who died before the test could be considered, there was a 14% 1 year cardiac mortality in 192 patients who did not take the test (150 for medical and 42 for logistic reasons) compared with 5% in those who did (p less than .0001). Of those who took the test, 12% subsequently underwent bypass grafts surgery compared with 14% of those who did not (p greater than .05). Decreased mortality in the year after the infarction in those taking the test was associated with an increase in blood pressure to 110 mm Hg or higher (3% vs 18%; p less than .001), ability to complete the 9 min test (3% vs 8%; p less than .01), and the absence of couplets (4% vs 13%; p less than .05) or any ventricular ectopic depolarizations (4% vs 7%, p less than .05) before, during, or after exercise. Achievement of a blood pressure of 110 mm Hg or higher during exercise in patients with no evidence of pulmonary congestion on the chest x-ray identified a group of 454 patients (70% of those taking the test) with a 1 year cardiac mortality of 1% compared with 13% in the remaining patients (p less than .0001). Logistic models showed that the exercise test contributed independent prognostic information for cardiac death, new infarction, and bypass surgery. Results of low-level exercise testing before hospital discharge combined with clinical features of the infarction can effectively identify patients at low risk for subsequent cardiac mortality.