Detection of residual jeopardized myocardium 3 weeks after myocardial infarction by exercise testing with thallium-201 myocardial scintigraphy

[Risk stratification after acute myocardial infarction]

In recent years, the characteristics of patients who suffer acute myocardial infarction without complications during hospitalization have changed. In addition, the range of non-invasive studies available for evaluating left ventricular systolic function, residual myocardial ischemia, and myocardial viability in these patients has improved. Left ventricular systolic function and residual ischemia should be evaluated in all patients before release. The non-invasive technique used (exercise test, echocardiography, nuclear cardiology, magnetic resonance imaging) depends on availability, experience, and results at each institution. Coronary arteriography should be performed in patients with significant ischemia or severe left ventricular systolic dysfunction in non-invasive studies. In these cases coronary angiography must be performed to determine if coronary arteries are suitable for revascularization before performing a test of myocardial viability.

Prognostic assessment of uncomplicated first myocardial infarction by exercise echocardiography and Tc-99m tetrofosmin gated SPECT

BACKGROUND

We evaluate the prognostic value of stress echo and gated single photon emission computed tomography (SPECT) after a first uncomplicated acute myocardial infarction.

METHODS AND RESULTS

We used predischarge maximal subjective exercise echocardiography and gated SPECT with technetium 99m tetrofosmin to prospectively study 103 patients younger than 70 years with a first acute myocardial infarction. During a 12-month follow-up period, 2 patients died, 9 had heart failure, and 29 had ischemic complications (4 reinfarction and 25 angina). Predictive variables for heart failure in multivariate analysis were ejection fraction evaluated by echocardiography (odds ratio [OR] 8.5, P =.016) or by gated SPECT (OR 10.7, P =.009). Predictive variables for ischemic complications in multivariate analysis were less than 5 metabolic equivalents (METS) in exercise test (OR 5.2, P =.007) and greater than 15% ischemic extent in the polar map (OR 3.6, P =.04) of SPECT.

CONCLUSIONS

Exercise echocardiography and Tc-99m tetrofosmin gated SPECT were predictive for heart failure, but exercise SPECT was the only test with predictive power for ischemic complications.

Risk stratification after acute myocardial infarction in the reperfusion era

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

Usefulness of dual SPECT with Tc-99m pyrophosphate and Tl-201 to predict further events after acute myocardial infarction with single-vessel coronary artery disease

PURPOSE

This study was undertaken to determine whether the findings of dual SPECT with Tc-99m pyrophosphate (PYP) and Tl-201 were predictive of further cardiac events after acute myocardial infarction.

METHODS

The authors evaluated 88 patients with acute myocardial infarction who underwent dual SPECT for single-vessel coronary artery disease.

RESULTS

Twenty-nine patients showed overlapping of Tc-99m PYP and Tl-201 in the same location (overlap-positive group), and 59 patients had no overlap (overlap-negative group). In patients in the overlap-positive group, the incidence of subsequent events was significantly higher than in patients in the overlap-negative group (P < 0.001). In the overlap-positive group, the number of overlap segments in patients with further events was significantly greater than that in patients without further events (P < 0.005).

CONCLUSIONS

Areas with overlapping of Tc-99m PYP and Tl-201 may contain jeopardized myocardium. These results suggest that patients who have a Tc-99m PYP and Tl-201 overlap-negative scan are a low risk group, whereas patients who have more overlapping segments may require catheterization and revascularization. Thus simultaneous SPECT imaging with Tc-99m PYP and Tl-201 might be useful to identify patients with greater ischemic risk after acute myocardial infarction.

Dual radionuclide single-photon emission computed tomography in the prediction of further ischemic risk after acute myocardial infarction

To evaluate whether the findings of dual single-photon emission computed tomography (SPECT) with technetium-99m pyrophosphate (Tc-99m PPi) and thallium-201 were predictive of further cardiac events in their hospital course, we studied 130 patients recovering from acute myocardial infarction (AMI). Fifty-four patients showed overlapping of Tc-99m PPi and thallium-201 in the same location (overlap positive group), and 76 patients had no overlap (overlap negative group). Of the 130 patients, 36 (28%) had a cardiac event. In patients in the overlap positive group, the incidence of subsequent events was significantly higher than in patients in the overlap negative group (44% versus 16%; p < 0.001). In the overlap positive group, the Tc-99m PPi uptake score and the number of overlap segments in patients with further events was significantly higher than those in patients without further events (10.2 +/- 5.1 versus 6.4 +/- 4.1, p < 0.005 and 5.2 +/- 2.0 versus 3.3 +/- 1.3, p < 0.001, respectively). These results suggest that patients who have a Tc-99m PPi and thallium-201 overlap negative scan can be candidates for early hospital discharge. In contrast, patients who have a greater number of overlap segments may require early catheterization and revascularization, so that simultaneous SPECT imaging Tc-99m PPi and thallium-201 might be useful for identifying patients with further ischemic risk after AMI in their hospital course.

Diastolic time during exercise-induced myocardial ischemia in patients with myocardial infarction

The relation between diastolic time and myocardial perfusion defect redistribution of the infarct-related region was studied during upright bicycle exercise with thallium-201 scintigraphy in 37 patients with recent anterior myocardial infarction. In addition to the higher incidence of residual stenosis of the infarct-related artery, a disproportionate shortening of diastolic time in patients with myocardial perfusion defect redistribution permitted further reduction of subendocardial blood flow during exercise.

Value of thallium-201 imaging in detecting adverse cardiac events after myocardial infarction and thrombolysis: a follow up of 100 consecutive patients

OBJECTIVE

To determine the prognostic role of thallium-201 imaging compared with that of exercise electrocardiography in patients with acute myocardial infarction treated by thrombolysis.

DESIGN

Patients who remained free of adverse cardiac events six weeks after myocardial infarction had stress and rest 201TI imaging and exercise electrocardiography and were followed up for 8-32 months. Adverse cardiac events (death, reinfarction, unstable angina, and congestive heart failure) were documented.

SETTING

Large district general hospital, Middlesex.

SUBJECTS

100 consecutive male and female patients who were stable six weeks after thrombolysis for myocardial infarction.

MAIN OUTCOME MEASURES

Prediction of occurrence of adverse cardiac events after myocardial infarction by exercise cardiography and 201TI myocardial perfusion imaging.

RESULTS

Reversible ischaemia on 201TI imaging predicted adverse cardiac events in 33 out of 37 patients with such events during follow up (hazard ratio 8.1 (95% confidence interval 2.7 to 23.8), P < 0.001). Exercise electrocardiography showed reversible ischaemia in 33 patients, of whom 13 had subsequent events, and failed to predict events in 24 patients (hazard ratio 1.1 (0.56 to 2.2), P = 0.8).

CONCLUSION

201TI imaging is a sensitive predictor of subsequent adverse cardiac events in patients who have received thrombolysis after acute myocardial infarction, whereas exercise electrocardiography fails to predict outcome.

Usefulness of transesophageal atrial pacing combined with two-dimensional echocardiography (echo-pacing) in predicting the presence and site of residual jeopardized myocardium after uncomplicated acute myocardial infarction

The usefulness of transesophageal atrial pacing combined with 2-dimensional echocardiography (echo-pacing) in predicting the presence and site of jeopardized myocardium, defined as areas of myocardium perfused by a vessel with a stenosis > or = 75% or by a collateral circulation if the supplying vessel was occluded, was evaluated in 31 patients with uncomplicated acute myocardial infarction who underwent coronary angiography. All 5 patients without jeopardized myocardium had a negative test, whereas 24 of 26 with jeopardized muscle had a positive test (sensitivity 92%; specificity 100%). To identify the site of jeopardized myocardium, tests that were positive for development of new asynergies were analyzed further, distinguishing those positive in the infarct or remote zone. Seven of 8 patients with new asynergies in the remote zone had areas of jeopardized myocardium outside the territory of distribution of the infarct-related vessel, whereas only 2 of 12 with new asynergies in the infarct zone had areas of jeopardized myocardium outside that territory (p < 0.01), correctly predicting the site of jeopardized myocardium in 17 of 20 cases. In conclusion, echo-pacing is useful for detecting the presence and site of jeopardized myocardium after an acute myocardial infarction.

Postexercise changes of the QTc interval in patients with recent myocardial infarction

A lack of the QTc ratio decrease at maximal exercise is considered as an index of exercise-induced ischemia in patients with coronary artery disease. The authors studied 51 patients with recent myocardial infarction in order to evaluate the QTc changes with exercise in assessing the presence of remaining ischemic myocardium. All patients were submitted to exercise stress tests, coronary angiographies, and exercise thallium 201 scintigraphies within 3-5 months of the myocardial infarction. Of the patients studied, 18 showed one-vessel disease and 33 showed multivessel disease. All vessels were classified as patent or occluded. In all patients with reversible thallium 201 defects both at distance and in the infarct zone, the QTc interval following exercise either showed a prolongation or no change from the resting electrocardiogram. In patients with only fixed perfusion defects, the QTc shortened at the end of the test. This study showed a low sensitivity and specificity for inducible ST-segment depression compared with the delayed redistribution on the postexercise thallium 201 scintigram. QTc variations at the end of exercise electrocardiograms are valuable as a noninvasive, low-cost identification of residual ischemic myocardium in patients after myocardial infarction.

Dose and test for dipyridamole infusion and cardiac imaging early after uncomplicated acute myocardial infarction

To evaluate the relation of the dose of intravenous dipyridamole on results of thallium and echocardiographic testing, the results of standard- (0.56 mg/kg/4 minutes) versus high- (0.84 mg/kg/10 minutes) dose dipyridamole were obtained 9 +/- 3 days after uncomplicated acute myocardial infarction in 57 patients. New wall motion abnormalities were compared with redistribution of thallium imaging and results of discharge coronary angiography. The sensitivity of thallium in predicting the presence of multivessel coronary artery disease was significantly (p < 0.01) higher (85%) than echocardiography (53%) and was unaffected by the dose. However the sensitivity of echocardiography was better with the higher dose (53 vs 14%). Minor adverse effects occurred in 34 patients (59%) after receiving the high dose and only in 4 patients (7%) after the standard dose (p < 0.001). Thus, thallium-201 scintigraphy during standard-dose dipyridamole infusion is more effective than high-dose dipyridamole echocardiographic testing in safely identifying patients who could benefit from early invasive evaluation and therapy.

Cardiac imaging after acute myocardial infarction. Identification of patients at continued risk

Diagnostic imaging performed early in the course of acute myocardial infarction provides anatomic and functional information that is useful in assessing patients at risk for future cardiac events and premature death. Early identification of left ventricular dysfunction or complications of myocardial infarction allows appropriate and timely management of high-risk patients and early transfer of stable patients from the intensive care environment. Noninvasive predischarge functional imaging to unmask patients with jeopardized myocardium identifies high-risk patients who may need invasive studies and surgical or interventional treatment. Postdischarge risk stratification with diagnostic imaging provides vital prognostic information in high- and low-risk patients, allowing for appropriate allocation of medical resources.

Influence of exercise intensity on the presence, distribution, and size of thallium-201 defects

The effects of two levels of exercise intensity on the size and location of thallium-201 defects were compared in 22 patients with known ischemic coronary artery disease. A symptom-limited incremental exercise test was performed followed (greater than 48 hours) by submaximal steady-state exercise at 70% of the peak heart rate achieved during the incremental test. Planar thallium-201 myocardial scans obtained after each protocol were analyzed by means of both visual qualitative and computerized quantitative methods. After incremental exercise all patients exhibited reversible thallium-201 defects, and submaximal exercise still resulted in reversible defects in 20 (91%) patients. However, the size of the ischemic area and the degree of ischemia were significantly reduced by both qualitative and quantitative criteria after submaximal exercise. Therefore interpretation of thallium-201 scans with regard to severity of disease and prognosis should take into account exercise intensity.

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.

Noninvasive and invasive testing after myocardial infarction

Recurrent myocardial ischemia, moderate to marked depression of left ventricular systolic function, and late-occurring or recurrent cardiac arrhythmia indicate increased risk for patients with acute myocardial infarction. Some patients, on the basis of high risk and/or unsuccessful response, will be early candidates for early aggressive diagnostic and therapeutic procedures. Others will have clinical indicators of increased risk during hospitalization that warrant diagnostic coronary arteriographic assessment before discharge. Still other patients with low risk clinical characteristics can be further stratified by predischarge or early postdischarge stress testing for myocardial ischemia, left ventricular functional reserve, and/or likely occurrence of arrhythmias. Some stratified to low risk patients will be treated only with secondary prevention measures. Others at higher risk will undergo more aggressive evaluation and subsequent medical or surgical therapy.

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

BACKGROUND

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

METHODS AND RESULTS

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

CONCLUSIONS

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

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.

Prognostic value of predischarge low-level exercise thallium testing after thrombolytic treatment of acute myocardial infarction

Low-level exercise thallium testing is useful in identifying the high-risk patient after acute myocardial infarction (AMI). To determine whether this use also applies to patients after thrombolytic treatment of AMI, 64 patients who underwent early thrombolytic therapy for AMI and 107 patients without acute intervention were evaluated. The ability of both the electrocardiogram and thallium tests to predict future events was compared in both groups. After a mean follow-up of 374 days, there were 25 and 32% of cardiac events in the 2 groups, respectively, with versus without acute intervention. These included death, another AMI, coronary artery bypass grafting or angioplasty with 75% of the events occurring in the 3 months after the first infarction. The only significant predictors of outcome were left ventricular cavity dilatation in the intervention group and ST-segment depression and increased lung uptake in the nonintervention group. The sensitivity of exercise thallium was 55% in the intervention group and 81% in the nonintervention group (p less than 0.05). Therefore, in patients having thrombolytic therapy for AMI, nearly half the events after discharge are not predicted by predischarge low-level exercise thallium testing. The relatively weak correlation of outcome with unmasking ischemia in the laboratory before discharge may be due to an unstable coronary lesion or rapid progression of disease after the test. Tests considered useful for prognostication after AMI may not necessarily have a similar value if there has been an acute intervention, such as thrombolytic therapy.

Value of thallium-201 reinjection after delayed SPECT imaging for predicting reversible ischemia after coronary artery bypass grafting

The reinjection of a small dose (40 MBq) of thallium-201 after stress and delayed imaging often shows new redistribution in the regions with persistent defect. To assess whether these segments may represent reversible ischemia, reinjection thallium-201 single-photon emission computed tomography (SPECT) was performed after stress and 3-hour delayed imaging in 24 patients before coronary artery bypass grafting (CABG). The left ventricular myocardium was divided into 5 myocardial segments and regional wall motion was scored on a scale from 0 (normal) to 4 (dyskinesia). Thallium-201 findings were compared with improvement in regional perfusion and wall motion 1 to 2 months after CABG. The reinjection imaging identified new redistribution in 15 of 32 persistent defects (47%) on the 3-hour delayed images. In the study of stress and delayed SPECT imaging, the improvement in perfusion was observed in 34 of 43 segments (79%) exhibiting redistribution and 15 of 32 (47%) segments without redistribution (p less than 0.01). The reinjection SPECT identified new redistribution in 12 of the 15 improved segments that were not detected on the delayed images. Similarly, the improvement in wall motion was observed in 23 of 31 segments (74%) exhibiting redistribution and 14 of 30 segments (47%) without redistribution on the delayed images (p less than 0.05). The reinjection identified new redistribution in 10 of the 14 improved segments that were undetected on the delayed images. The predictive values for improvement in perfusion and wall motion by the reinjection imaging were significantly higher (92 and 89%) than those by the delayed imaging (69 and 62%, respectively, p less than 0.05 each).(ABSTRACT TRUNCATED AT 250 WORDS)

Quantitative exercise thallium-201 rotational tomography for evaluation of patients with prior myocardial infarction

The utility of stress-redistribution thallium-201 myocardial perfusion single-photon emission computed tomography (SPECT) in patients with a prior single myocardial infarction was studied in 66 patients who were tested by both SPECT and coronary angiography. SPECT was quantified by comparing the patients' circumferential count profiles to a previously established normal data base and by plotting the results onto a polar coordinate map that localized defects to the 3 major coronary artery territories. The pattern of reversibility of the quantitatively detected defects was assessed by consensus visual analysis. SPECT thallium-201 detected myocardial infarction in 62 of 66 patients (sensitivity = 94%). Sixty-five percent of the infarct zones showed some reversibility at 4-hour imaging which corresponded with angiographic evidence of flow to the infarct zones in 95.5% of cases. Late (18 to 24 hours) imaging, done in 26 patients, showed complete or partial reversibility of 29% of infarct zone segments which were nonreversible on 4-hour images. To improve specificity for detection of disease in coronary arteries supplying the non-infarct territories, new quantitative criteria were developed that took into consideration contiguity of defects with the infarct zone. Accuracy for detection of patients with multivessel coronary disease by quantitative thallium-201 SPECT was 86%, which was significantly higher than those of the clinical response to exercise (48%), the exercise electrocardiographic response (56%) or their combination (65%).(ABSTRACT TRUNCATED AT 250 WORDS)

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

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

Exercise thallium-201 scintigraphy in the localization of myocardial ischaemia

We performed a retrospective study in order to study the ability of thallium-201 exercise scintigraphy to detect and to localize coronary artery perfusion defects (in comparison with a recent coronary angiogram). We studied 81 patients (67 males); their average age was 52.3 years (men 50.5 and women 54.1 years). They performed a pulse-conducted cycle exercise test, and 2 min before end of exercise 75 MBq of thallium-201 was infused intravenously, and tomographic images were reconstructed by using a Siemens-Rota SPECT gamma camera immediately and 4 h after exercise. The thallium-201 uptake defects were attributed to different coronary arteries, and the results were compared with a coronary angiogram made afterwards in 48 patients. The groups of one-, two- and three-vessel disease were 27, 21, and 21 patients, and only 12 patients did not have significant (over 50%) stenoses. The latter had the highest ejection fraction and working capacity. Sensitivity of thallium-201 exercise scintigraphy was 65%, whereas that of exercise ECG was 41% in patients with a low ejection fraction, while in the whole material the sensitivity of thallium-201 scintigraphy was 91% and that of exercise ECG was 54%. A stenosis in the right coronary artery was best localized by the thallium-201 scintigram (86% correctly); a stenosis in the left anterior descending artery was localized correctly in 75% of the cases, but a stenosis in left circumflex artery was localized correctly only in 44%. We conclude that exercise thallium-201 scintigraphy is a useful method not only in detecting but also in localizing coronary artery disease.

High dose dipyridamole echocardiography early after uncomplicated acute myocardial infarction: correlation with exercise testing and coronary angiography

The feasibility, safety and usefulness of dipyridamole echocardiography (two-dimensional echocardiography and 12 lead electrocardiographic monitoring during dipyridamole infusion, up to 0.84 mg/kg over 10 min) were evaluated in 94 asymptomatic patients 8 to 10 days after uncomplicated acute myocardial infarction. The results were compared with those of symptom-limited treadmill exercise testing and correlated with coronary angiography. Two mechanical patterns of positivity of dipyridamole echocardiography could be identified: 1) a new wall motion abnormality confined to the infarct zone or to the adjacent segments (24 patients), and 2) transient remote asynergy (33 patients). The success rate in recording adequate images during dipyridamole infusion was 100%. Interobserver agreement concerning diagnosis occurred in 89 (93%) of 94 patients. Dipyridamole echocardiography was well tolerated; no complication was observed during or after the test. Seventy-three patients underwent coronary angiography within 6 weeks after acute myocardial infarction. Transient remote asynergy on echocardiography was present in 27 of 40 patients with multivessel disease and in none of 33 patients without multivessel disease. Results of treadmill exercise testing were positive in 28 patients with multivessel disease and 8 patients without multivessel disease. Thus, the sensitivity of dipyridamole-induced transient remote asynergy was 68% compared with 52% for treadmill testing (p less than 0.05); specificity was 100% and 72%, respectively (p less than 0.005). The overall accuracy of dipyridamole echocardiography (81%) was higher than that of dipyridamole stress electrocardiography (63%) or exercise electrocardiography (60%) (p less than 0.02). It is concluded that dipyridamole echocardiography is a useful, feasible and inexpensive nonexercise-dependent test for detecting the extent of coronary artery disease early after acute myocardial infarction.

Risk stratification in patients with first non-Q wave infarction: limited value of the early low level exercise test after uncomplicated infarcts. The Multicenter Post-Infarction Research Group

Risk stratification using clinical and historical variables plus early low level exercise testing was performed in 141 patients with a first non-Q wave myocardial infarction. The 111 patients who performed the exercise test had a 3.6% cardiac mortality rate in the first year compared with 13.3% in the 30 patients who could not exercise (p = 0.063), and a 1 year incidence rate of recurrent cardiac events (cardiac death or recurrent nonfatal myocardial infarction) of 10.8% compared with 23.3% (p = 0.127). Patients who developed ischemia (ST depression or angina) during the test had an increased incidence of cardiac events in the year after the infarction (odds ratio greater than 3, p less than 0.05). When patients were subgrouped by the presence or absence of pulmonary congestion, the discriminatory value of the exercise test was seen to reside primarily in the cohort with pulmonary congestion. For example, ST depression during exercise in this group identified patients with a 71% incidence of cardiac events in the year after the infarction compared with 5.3% for those without ST depression (odds ratio 45, p = 0.002). In the patients without pulmonary congestion, the exercise test had no discriminatory value. It is concluded that early low level exercise testing has a limited role after an uncomplicated non-Q wave infarction, but is useful in patients with clinical markers of higher risk.

Quantification of myocardial infarction during coronary occlusion and myocardial salvage after reperfusion using cardiac imaging with technetium-99m hexakis 2-methoxyisobutyl isonitrile

Myocardial imaging with technetium-99m hexakis 2-methoxyisobutyl isonitrile was investigated as a means to assess myocardial infarct size during coronary occlusion and to quantify the extent of salvaged myocardium after coronary occlusion followed by reperfusion. Open chest dogs underwent either a permanent coronary artery occlusion (Group 1, n = 16) or a 2 h occlusion followed by reperfusion (Group 2, n = 15). Animals in both groups were killed 48 h after occlusion. During coronary occlusion, 23 of the 25 dogs that survived the coronary occlusions had abnormal myocardial scintigrams. The scintigraphic perfusion defect size correlated well with the pathologic infarct size (r = 0.85 and 0.95 by planar and tomographic imaging, respectively). The planar scintigraphic defect size, but not the tomographic defect size, overestimated the pathologic size. The planar scintigraphic defect size observed during coronary occlusion was markedly reduced 48 h after reperfusion (24.8 +/- 12.8% to 10.6 +/- 9.7% of the left ventricle, p less than 0.003). The uptake of technetium-99m hexakis 2-methoxyisobutyl isonitrile in the ischemic myocardium increased significantly 48 h after reperfusion (p less than 0.003) and correlated with the increase in regional myocardial blood flow, as assessed by radioactive microspheres (r = 0.83, p less than 0.01). Thus, myocardial imaging with technetium-99m hexakis 2-methoxyisobutyl isonitrile allows reliable demonstration of the presence of acute infarction, estimation of infarct size and quantification of the extent of salvaged myocardium after coronary reperfusion.

Prognostic cardiac catheterization variables in survivors of acute myocardial infarction: a five year prospective study

The prognostic variables from predischarge coronary angiography and left ventriculography in survivors of acute myocardial infarction during the years 1974 to 1978 were evaluated in 143 patients (less than or equal to 66 years of age) with documented myocardial infarction who were then followed up prospectively for 5 years. One half of the study population had triple vessel coronary disease (greater than or equal to 50% stenosis). However, only 7% of patients had severely depressed left ventricular function with an ejection fraction less than or equal to 29%. Evaluation of the contribution of many clinical and angiographic variables to a first cardiac event (death, nonfatal reinfarction or coronary artery bypass surgery) was considered with Kaplan-Meier actuarial curves and multivariate Cox's hazard function analysis. A risk segment was defined as an area of contracting myocardium supplied by a coronary artery with a greater than 50% stenosis. Multivariate analysis demonstrated that right plus left anterior descending coronary artery stenoses (p less than 0.01), ejection fraction (p less than 0.01) and the presence of risk segments (p less than 0.05) were significant predictors of outcome. Furthermore, on separate multivariate analyses, the angiographic variables added significantly to the clinical variables to predict cardiac events over 5 years of follow-up. Therefore, in survivors of acute myocardial infarction who undergo cardiac catheterization, additive prognostic information is obtained that can be used to stratify risk over 5 years.

Acute myocardial infarction associated with single vessel coronary artery disease: an analysis of clinical outcome and the prognostic importance of vessel patency and residual ischemic myocardium

The long-term outcome and the significance of residual ischemic myocardium, as assessed by predischarge exercise thallium scintigraphy and vessel patency, were studied in 97 patients with single vessel coronary artery disease by angiography 12 +/- 4 days after uncomplicated myocardial infarction. During a mean follow-up period of 39 +/- 17 months, no patients died, 6 (6%) had a recurrent nonfatal infarction and 25 (26%) experienced rapidly progressive angina requiring hospitalization. Although neither exercise-induced angina nor ST segment depression was predictive of a recurrent cardiac event, the mean number of infarct zone scan segments showing thallium redistribution (1.0 +/- 1.0 versus 0.5 +/- 0.8, p = 0.01) and the percent of patients with infarct zone redistribution (61 versus 39%, p = 0.05) were greater in those patients who experienced a late ischemic event. Kaplan-Meier analysis demonstrated a lower event-free survival rate in patients with redistribution (n = 45) than in those without redistribution (n = 52) (p = 0.019). Although no patient received immediate thrombolytic therapy, the infarct-related vessel was angiographically patent in 40 patients (41%). Vessel patency did not influence event-free survival, although a patent vessel, as compared with an occluded vessel, was associated with a greater prevalence of non-Q wave infarction (58 versus 21%, p less than 0.001), fewer persistent infarct zone thallium defects (1.2 +/- 1.1 versus 2.0 +/- 1.2, p = 0.001), more reversible infarct zone thallium defects (1.0 +/- 1.0 versus 0.5 +/- 0.9, p = 0.02) and a trend toward a higher left ventricular ejection fraction (53 +/- 10% versus 49 +/- 12%, p = 0.07). In summary, uncomplicated myocardial infarction in patients with single vessel coronary artery disease is associated with a very low incidence of subsequent death and reinfarction. The presence of infarct zone thallium redistribution, compared with its absence, is predictive of a higher cardiac event rate. These data should be considered when recommending prophylactic percutaneous transluminal angioplasty after uncomplicated myocardial infarction in asymptomatic patients with single vessel coronary disease. On the basis of these results, future randomized trials designed to evaluate the therapeutic efficacy of revascularization in asymptomatic postinfarction patients with single vessel disease should limit enrollment to those patients with residual ischemia located within the infarct zone.

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.

Percutaneous transluminal coronary angioplasty in patients with prior myocardial infarction: angioplasty at a distance from the prior infarct zone

Patients undergoing coronary angioplasty who have had a prior transmural myocardial infarction in the distribution of a contralateral coronary artery are considered a high-risk group because of potentially severe left ventricular dysfunction if an ischemic complication occurs. The purpose of this study was to evaluate the safety and efficacy of coronary angioplasty in 28 patients with prior myocardial infarction remote from the artery undergoing dilatation. Prior myocardial infarction was defined by the presence of pathologic Q waves on ECG or segmental akinesis on ventriculography. Angioplasty was successful in 30 of 33 lesions (91%) and in 25 of 28 patients (89%). Mean stenosis diameter was reduced from 91% +/- 7% to 28% +/- 16%; mean translesional gradient after angioplasty was 6 +/- 5 mm Hg. No patient developed severe hemodynamic deterioration from transient coronary occlusion during balloon inflation or from an acute ischemic complication. Three patients underwent coronary artery bypass surgery after unsuccessful angioplasty. There were no new Q wave infarctions or deaths. The results of coronary angioplasty in patients with prior infarction were compared with those of 203 patients without prior remote infarction. Primary success and occurrence of major complications were comparable in both groups. At a mean follow-up of 12 +/- 6 months, 18 of the 25 patients (72%) who underwent initially successful dilatation have remained symptom free with angioplasty alone. Therefore, coronary angioplasty is a suitable therapeutic procedure in carefully selected patients with angina pectoris and prior myocardial infarction at a distance from the site of angioplasty.

Current review of exercise testing: application and interpretation

Exercise testing has changed dramatically in scope over the past 50 years. While initially used to assess functional capacity, it is now also utilized to detect the presence and severity of coronary artery disease (CAD), to evaluate postmyocardial infarction patients at risk for future cardiac events, to screen certain asymptomatic populations for CAD, and to evaluate dysrhythmias, peripheral vascular disease, and lung disease. Dynamic exercise in continuous multistage protocols is most popularly employed because of the more easily measured workload. The safety of exercise testing, its contraindications and termination end points are summarized. The sensitivity of exercise testing ranges between 60 and 70% while specificity has been reported between 85 and 90%. Both sensitivity and specificity are enhanced through use of radionuclide exercise thallium imaging and ventricular angiography.

Predicting the extent and location of coronary artery disease in acute myocardial infarction by echocardiography during dobutamine infusion

The feasibility, safety and usefulness of 2-dimensional echocardiography (2-D echo) during dobutamine infusion for identifying patients with multivessel coronary artery disease (CAD) after acute myocardial infarction (AMI) were evaluated in 30 patients 5 to 10 days after AMI. Patients underwent 2-D echo under basal conditions and during dobutamine infusion at each dose from 5 to a maximum of 40 micrograms/kg/min, limited multilead submaximal bicycle exercise testing and coronary and left ventricular angiography. Echocardiograms were analyzed independently by 2 observers. The test response was considered positive if abnormal wall motion and reduced myocardial thickening were observed during dobutamine infusion in vascular distributions other than the area of infarction identified during basal conditions. Exercise testing was considered positive when more than 1 mm of ST depression occurred 80 ms after the J point. Dobutamine stress testing was well tolerated; no complications and no significant arrhythmia were observed. Echocardiographic recordings were adequate in all patients during the entire test; the concordance in interpretation between the 2 observers was perfect for the prediction and location of ischemic segments during dobutamine infusion. In 15 of 17 patients without multivessel CAD, no asynergy was observed outside the infarct zone during dobutamine infusion (specificity 88%). In 11 of 13 patients with multivessel CAD, new wall motion abnormalities were identified in the segments corresponding to the arterial lesions diagnosed by angiography (sensitivity 85%).(ABSTRACT TRUNCATED AT 250 WORDS)

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.

Reversibility of cardiac wall-motion abnormalities predicted by positron tomography

Positron emission tomography (PET) can be used with nitrogen-13-ammonia (13NH3) to estimate regional myocardial blood flow, and with fluorine-18-deoxyglucose (18FDG) to measure exogenous glucose uptake by the myocardium. We used PET to predict whether preoperative abnormalities in left ventricular wall motion in 17 patients who underwent coronary-artery bypass surgery were reversible. The abnormalities were quantified by radionuclide or contrast angiography or both, before and after grafting. PET images were obtained preoperatively. Abnormal wall motion in regions in which PET images showed preserved glucose uptake was predicted to be reversible, whereas abnormal motion in regions with depressed glucose uptake was predicted to be irreversible. According to these criteria, abnormal contraction in 35 of 41 segments was correctly predicted to be reversible (85 percent predictive accuracy), and abnormal contraction in 4 of 26 regions was correctly predicted to be irreversible (92 percent predictive accuracy). In contrast, electrocardiograms showing pathological Q waves in the region of asynergy predicted irreversibility in only 43 percent of regions. We conclude that PET imaging with 13NH3 to assess blood flow and 18FDG to assess the metabolic viability of the myocardium is an accurate method of predicting potential reversibility of wall-motion abnormalities after surgical revascularization.

Limitations of premature ventricular complex morphology in the diagnosis of myocardial infarction

To determine the diagnostic value of Q-waves (greater than or equal to 0.04 seconds duration) in premature ventricular complexes (PVC's) for the presence of myocardial scar, we examined 12-lead electrocardiograms and multiple lead rhythm strips obtained before and after exercise at the time of thallium-201 myocardial imaging in 970 patients. PVC's were found in 233 patients, 112 of whom had fixed thallium-201 perfusion defects indicative of myocardial scar. PVC's occurring during exercise were excluded from the analysis. Twenty-one patients had Q-wave PVC's in one or more electrocardiographic leads. Of those, 14 patients (67%) had myocardial scar in the suggested location. Myocardial scar was more common among patients with Q-wave PVC's than in patients without (67% vs. 36%, p less than 0.01). However, only 6 of 13 patients (46%) with Q-wave PVC's but no diagnostic sinus beats actually had myocardial scar. The remaining seven patients had Q-wave PVC's, no myocardial scar, and no evidence of myocardial ischemia suggested by angina during exercise, exercise electrocardiogram or thallium-201 imaging. We conclude that although Q-wave PVC's indicate the presence of myocardial scar in 67% of patients, they yield little or no additional diagnostic information to that obtained from the sinus beats

Value and limitations of exercise radionuclide angiography for detecting myocardial ischemia in healed myocardial infarction

Exercise radionuclide angiography was performed in 65 normal subjects (group I), in 31 patients with exercise-induced transient thallium defects after acute myocardial infarction (AMI) (group II), and in 16 patients without exercise-induced transient thallium defects, angina or electrocardiographic changes after AMI (group III). Absolute left ventricular (LV) volumes were measured using a correction for attenuation in each patient. Similar peak heart rate-blood pressure products were achieved in groups II and III. Although the mean LV ejection fraction (EF) response to exercise in group III (increase of 0.11 +/- 0.10 units) closely resembled that of normal persons (increase of 0.14 +/- 0.09 units) and was significantly different from that of group II (decrease of 0.04 +/- 0.12), there was considerable individual variation. An abnormal EF response to exercise, defined as failure of EF to increase by at least 0.05 units, was found in 6 subjects (9%) in group I, 26 patients (84%) in group II, and 2 patients (13%) in group III. End-systolic volume failed to decrease in 10 subjects (15%) in group I, 25 patients (81%) in group II and 7 patients (44%) in group III. New regional wall motion abnormalities were found in no subject in group I, in 16 patients (52%) in group II and in only 1 patient (6%) in group III. Thus, although group responses of EF or end-systolic volume appeared to correlate with the presence or absence of ischemia, some patients with exercise-induced transient thallium defects after AMI responded normally to exercise radionuclide angiography stress testing and some patients without other evidence of exercise-induced ischemia after AMI responded to exercise radionuclide angiography testing abnormally.(ABSTRACT TRUNCATED AT 250 WORDS)

Submaximal exercise testing early after myocardial infarction. Difficulty of predicting coronary anatomy and left ventricular performance

Impaired left ventricular function and extensive coronary artery disease are important determinants of prognosis after acute myocardial infarction. The ability of clinical and predischarge submaximal exercise test variables to predict multivessel coronary artery disease and impaired left ventricular function was assessed in 62 survivors of acute myocardial infarction. Abnormal exercise blood pressure response and short exercise performance were predictors of multivessel disease, but exercise induced ST segment changes and clinical variables were not. Q wave infarction, high grade Killip classification, and exercise induced ST segment elevation predicted statistically significant impairment of resting left ventricular function, whereas other clinical and exercise test variables did not. Exercise induced ST segment changes were therefore of little value in detecting extensive coronary disease, although exercise induced ST elevation was an indicator of poor resting left ventricular function. Although abnormal exercise haemodynamics may detect extensive coronary artery disease, other physiological markers of reversible myocardial ischaemia are probably necessary to plan optimal management in these patients.

Ischemia at rest is independent of the extent of ventricular dysfunction and arrhythmias in patients with coronary artery disease

To assess the relation between myocardial ischemia, ventricular arrhythmias (VA), and left ventricular (LV) dysfunction, we evaluated 74 patients with coronary artery disease (CAD) using radionuclide angiography (to determine the resting ejection fraction [EF]), resting thallium-201 scintigraphy (to ascertain the extent of resting ischemia), and 24-hour Holter monitoring (to assess VA). Thirty patients had resting ischemia, 26 had resting EF less than 30%, and 27 had repetitive VA. Patients with and without ischemia had similar EFs (36 +/- 14 vs 38 +/- 14, p = NS). Further, patients with and without repetitive forms of VA had a similar number of resting ischemic segments (1.1 +/- 1.7 vs 1.1 +/- 2.2, p = NS). Patients with EFs less than 30 had more VA than patients with EFs greater than or equal to 30 (Holter class 4.3 +/- 2.3 vs 3.0 +/- 1.8, p less than 0.01) but a similar extent of ischemia (1.4 +/- 2.2 vs 1.0 +/- 1.7, p = NS). Thus, while patients with lower EFs have more repetitive forms of VA, ischemia at rest is independent of VA and EF. These data suggest that prognostic stratification of patients with CAD for intervention studies should include a separate consideration of ischemia.

Electrocardiographic ST-T wave patterns, extent of coronary artery disease, and left ventricular performance following non-Q-wave myocardial infarction

Subendocardial, nontransmural, or non-Q-wave myocardial infarction (NQM) carries a serious prognosis. Many previous studies of NQMI include only patients without new Q waves at the time of infarction. Since the site of transmural MI (by Q waves) has implications concerning extent of coronary disease (CAD) and left ventricular (LV) dysfunction, we wondered what the extent of CAD and LV dysfunction is among acute MI patients who have neither new nor old Q waves. Furthermore, we sought to determine whether ST-T wave patterns or resting LV ejection fraction (EF), alone or combined, could separate NQMI patients with significant CAD from those with normal or nearly normal coronaries. Therefore, we retrospectively examined angiographic and electrocardiographic data in 55 symptomatic patients with NQMI. ST-T wave patterns on admission were classified as either ischemic (transient ST elevation, persistent horizontal ST depression, or persistent deep T wave inversion) or nonspecific. Eleven patients (20%) had normal or nearly normal coronaries (N); ten patients (18%) had one, seven patients (13%) had two, and 19 patients (34%) had three vessel CAD; eight patients (15%) had left main (LM) disease. Six of the 11 N patients had ergonovine tests and all six were negative. Segmental LV wall motion abnormalities (WMA) were commonly observed; however, diffuse LVWMA were present only among patients with three vessel and LM disease. EF was below 0.50 in 48% of patients with three vessel or LM disease. Although ischemic ST-T wave patterns were more common (P less than 0.05) among patients with significant CAD than among N patients, neither the ST-T wave pattern nor EF, alone or in combination, allowed confident separation of N patients from significant CAD patients. We conclude 1) A large proportion of NQMI patients have LM disease, three vessel disease, or normal or nearly normal coronaries. 2) Despite the absence of Q waves, LV dysfunction is common and the degree of LV impairment is worse among patients with more extensive CAD. 3) NQMI patients who may have normal or nearly normal coronaries cannot be reliably separated from NQMI patients with significant CAD on the basis of ST-T wave patterns or resting LVEF. 4) Coronary angiography appears warranted to assess the extent of CAD in symptomatic NQMI patients.

Comparative predictive value of ST-segment depression or angina during early and repeat postinfarction exercise tests

To determine the relative value of electrocardiographic (ECG) ST-segment depression alone compared to angina alone for predicting multivessel coronary artery disease during early and repeat postinfarction exercise tests, we evaluated 93 postmyocardial infarction patients with modified treadmill exercise tests prior to hospital discharge (mean 14 +/- 2 days), and 36 of these 93 patients with repeat exercise tests at six weeks following infarction. It was concluded that angina alone or angina irrespective of the presence of ST-segment depression are better predictors of multivessel coronary artery disease than ECG ST-segment depression alone, and the persistence of ischemic abnormalities during repeat treadmill exercise tests following infarction is useful for confirming the presence of multivessel coronary artery disease.

Non-Q wave myocardial infarction. Pathophysiology and prognostic implications

Non-Q wave myocardial infarctions, also known as nontransmural myocardial infarctions or subendocardial myocardial infarctions, have been managed as "mild" coronary events in the past. Substantial evidence now requires modification of this approach. Because of their tendency to be associated with modest cardiac enzyme level elevations, non-Q wave infarcts often result in a favorable early or inhospital prognosis. However, their late complications include recurrent angina, transmural myocardial infarction, and sudden death. Previous myocardial infarction with residual myocardium "at risk" from recurrent ischemia probably bears responsibility for these late complications. Earlier identification of patients at risk and appropriate interventions may improve the long-term prognosis after nontransmural infarcts.