Prognostic usefulness of dobutamine-induced ST-segment elevation and T-wave normalization after uncomplicated acute myocardial infarction

Normalization of abnormal T-waves during stress testing does not identify patients with reversible perfusion defects

OBJECTIVE

To determine if T-wave normalization during exercise or dobutamine stress testing identified patients with myocardial ischemia as indicated by reversible perfusion defects.

METHODS

Exercise or dobutamine stress tests with perfusion scintigraphy were performed in 1,173 patients with abnormal T-waves on their baseline electrocardiograms. The results of perfusion scintigraphy were compared in patients with and without stress-induced T-wave normalization.

RESULTS

Only 33 of 270 patients with reversible perfusion defects (12.2%) had T-wave normalization during stress while 76.4% of 140 patients who had T-wave normalization during stress did not have a reversible perfusion defect. Results were similar for patients who did or did not reach 85% of their maximal predicted heart rate, for patients with and without Q-wave infarction on the baseline EKG and for patients who did or did not have ischemic ST-segment depression during stress.

CONCLUSIONS

T-wave normalization during stress testing has low sensitivity and poor positive predictive value for stress-induced reversible myocardial ischemia.

Predischarge exercise electrocardiogram and stress echocardiography can predict long-term clinically driven revascularization following acute myocardial infarction

BACKGROUND

Predischarge stress testing provides suboptimal prediction of spontaneous hard events following uncomplicated acute myocardial infarction (AMI).

HYPOTHESIS

This study was aimed at assessing whether soft cardiac ischemic events requiring late revascularization could be predicted more accurately.

METHODS

In all, 428 patients undergoing exercise electrocardiography (ECG) and stress echocardiography (SE, 345 dobutamine and 83 dypiridamole) within 15 days of uncomplicated AMI were followed up for 425 (range 20-2220) days. Soft ischemic events (effort angina>class II [Canadian Cardiovascular Society Classification] and unstable angina) driving late (>6 months) revascularization were regarded as endpoints.

RESULTS

A total of 58 events (29 effort and 29 unstable angina with subsequent 47 coronary artery bypass grafts and 11 percutaneous transluminal coronary angioplasties) occurred: 26 in patients with positive exercise ECG and 34 in patients with positive SE. Univariate predictors of revascularizations were positive exercise ECG (p = 0.0001), peak wall motion score index (WMSI) (p = 0.0009), low workload (p = 0.0018), rest WMSI (p = 0.02) and positive SE (p = 0.02). Cox multivariate analysis selected peak WMSI, positive exercise ECG, and low workload positive exercise ECG as independent predictors of late revascularizations.

CONCLUSIONS

Predischarge stress testing identifies the long-term occurrence of soft ischemic events driving late revascularization after uncomplicated AMI.

Early negative T waves and viable myocardium in patients with a first ST-elevation acute coronary syndrome

Deep negative T waves (NTW) are a frequent finding following acute ST-segment elevation coronary syndromes but its possible relation with the status of regional contractility remains unclear. We studied 52 patients with a first ST-elevation acute coronary syndrome with or without NTW in anterior leads (> or =3 mm in > or=3 leads) and assessed the ejection fraction and regional myocardial contractility by contrast left ventriculography at baseline and during a low-dose dobutamine test (10 microg/kg per minute). Ejection fraction and regional contractility tended to be more preserved in patients with NTW, but dobutamine increased regional contractility in the jeopardized area in most patients with or without NTW and the improvement was similar in those either with or without enzyme elevation. In conclusion, deep NTW after ST-elevation acute coronary syndromes tends to be associated with a more preserved myocardium but it is neither a sensitive nor a specific marker of viable myocardium.

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

OBJECTIVES

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

BACKGROUND

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

METHODS

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

RESULTS

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

CONCLUSIONS

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