Significance of transient ST-T segment changes during dobutamine testing in Q wave myocardial infarction

Pseudo-Normalization of the T-wave During Stress and Its Relationship With Myocardial Ischemia: Evaluation by Myocardial Perfusion Single Photon Emission Computed Tomography (SPECT)

Background The T-wave alterations are suggestive of ischemia, among them there is the pseudo-normalization (positivization of the T-wave, previously negative, during stress exercise). Myocardial single photon emission computed tomography (SPECT) at rest and stress is usually performed with Technetium 99 (Tc-99), which has high sensitivity and specificity for the detection of ischemic heart disease. In this study, we decided to investigate the patients who pseudo-normalized the T-wave in the stress test to correlate with the existence of ischemia diagnosed by myocardial perfusion study, specifically myocardial SPECT in perfusion and rest with Tc-99. Methodology T - wave pseudo-normalization patients who underwent a myocardial perfusion SPECT between January 2018 and June 2019 were included in this retrospective study. We analyzed 81 patients: 50 patients with pseudo-normalization of T-waves and 31 patients, as a control group, without pseudo-normalization. A descriptive analysis of the quantitative variables was performed using Student's t-test or Mann-Whitney U test, and for the qualitative variables, the χ2 test or Fisher's exact test was performed. Results The degree of ischemia according to the presence or absence of pseudo-normalization of the T-wave. The pseudo-normalization of the T-wave in the group without ischemia (48.4% vs. 36%), for the mild degree the proportions were the same (38.7% vs. 38%), the moderate degree it was slightly higher in the pseudo-normalization of the T-wave (9.7% vs. 18%) and severe (3.2% vs. 6%). Conclusions In this study, the relationship between pseudo-normalization of the T waveform and ischemia, predominantly moderate to severe, was demonstrated. However, it was not statistically significant due to the size of the sample studied.

Myocardial viability in patients with thrombolyzed myocardial infarction: is it assessable by predischarge exercise electrocardiography test?

BACKGROUND

Most studies concerning exercise electrocardiography (ECG) testing after acute myocardial infarction (AMI) were carried out in the prethrombolytic era. ST-segment elevation in the infarction area during exercise has usually been interpreted as indicating the presence of dyskinesia as a result of extensive left ventricle damage.

HYPOTHESIS

This study was undertaken to evaluate the contributions of exercise-induced ST-segment elevation and T-wave pseudonormalization to the assessment of myocardial viability in patients with thrombolyzed myocardial infarction (MI), compared with low-dose dobutamine echocardiography.

METHODS

The study comprised 52 consecutive patients with AMI treated with thrombolysis. All patients underwent low-dose dobutamine echocardiography and symptom-limited exercise testing before discharge.

RESULTS

Nineteen patients showed ST-segment elevation (Group 1), 9 showed isolated T-wave pseudonormalization (Group 2), and 24 patients did not exhibit either of these ST-T segment changes (Group 3). Low-dose dobutamine echocardiography revealed evidence of viability in 16 patients (84%) in Group I (p = 0.01), 5 (56%) in Group 2 (p = NS), and 11 patients (46%) in Group 3 (p = NS).

CONCLUSION

Exercise-induced ST-segment elevation may contribute to the evaluation of myocardial viability in patients with AMI treated with thrombolysis. However, in the absence of exercise-induced ST-segment elevation, further noninvasive studies might be indicated to assess myocardial viability.

Exercise-induced ST-segment elevation in patients with a recent acute myocardial infarction treated by primary percutaneous coronary intervention

OBJECTIVES

To get insight in the mechanism of exercise-induced ST-segment elevation (STE) in patients with Q/QS waves at the electrocardiogram (ECG).

METHODS

We performed exercise stress test in 13 patients with anterior acute myocardial infarction treated by successful primary percutaneous coronary intervention (PCI).

RESULTS

Compared to rest, an additional STE > or = 1 mm in one or more precordial ECG leads during exercise occurred in nine patients (69%), in the absence of symptoms.

CONCLUSIONS

In acute myocardial infarction (MI) patients, treated by primary PCI and showing optimal coronary blood flow restoration at angiography, STE can still be induced by exercise in Q/QS wave ECG leads. This finding lends further support to the theory that exercise-induced STE in this clinical context is unlikely to represent by itself transient myocardial ischemia or viability.

Prognostic significance of ST-segment elevation during dobutamine stress echocardiography

BACKGROUND

Limited data are available concerning the significance of ST-segment elevation during dobutamine stress echocardiography (DSE). The purpose of this study was to assess the prognostic significance of new ST-segment elevation during DSE and its relationship to angiographic severity of coronary artery disease (CAD).

METHODS

From 4240 consecutive patients who had DSE, we identified 134 (3%) patients with new stress-induced ST-segment elevation > or =1 mm in at least two contiguous electrocardiographic leads. Significant CAD was considered as > or =50% diameter obstruction by angiography. Follow-up was obtained for cardiac events.

RESULTS

Age was 69 +/- 10 years; 84 (63%) were men. ST-segment elevation developed in the anterior leads in 55 (41%), inferior leads in 100 (75%), and lateral leads in 54 (40%); 56 (42%) had ST elevation in more than one region. Dobutamine stress echocardiography was abnormal in all patients; 115 (86%) had ischemia. Coronary angiography was obtained in 69 (51%) patients. Stenosis was > or =70% diameter in 68 (99%) patients and multivessel in 53 (77%). Follow-up (2.6 +/- 2.8 years) was obtained in all 134 patients. Events occurred in 103 (77%) patients, including death in 53, coronary revascularization in 33, myocardial infarction in 12, and unstable angina in 5. Event-free survival was 55% at 2 years, 38% at 4 years, and 28% at 5 years.

CONCLUSIONS

Patients with stress-induced ST-segment elevation during DSE commonly have severe CAD and are at high risk for events during follow-up. These patients should be considered for coronary angiography.

Significance of exercise-induced ST segment elevation in Q leads in patients with a recent myocardial infarction and an open infarct-related artery

AIMS

The significance of exercise-induced ST segment elevation in Q leads in patients with a recent myocardial infarction and without significant residual stenosis in the infarct-related artery has not been defined. We aimed to elucidate the role of myocardial perfusion and viability in this scenario.

METHODS AND RESULTS

Sixty-six patients with a first myocardial infarction, single-vessel disease and an open artery were studied. Myocardial perfusion was assessed with angiographic blush, intracoronary myocardial contrast echocardiography and magnetic resonance. Myocardial viability was quantified by means of magnetic resonance (transmural extent of necrosis). Exercise-induced ST elevation in Q leads was observed only in 13 cases (20%); 53 patients (80%) did not show this finding. The group with ST elevation had fewer cases with normal perfusion: Blush 3 (15% vs. 74%, p=0.001), myocardial contrast echocardiography score >0.75 (8% vs. 81%, p=0.001) and magnetic resonance score >0.75 (31% vs. 68%, p=0.03). Similarly, myocardial viability (necrosis <50%) was less frequent in patients with ST elevation (8% vs. 72%, p=0.001).

CONCLUSION

In patients with a first myocardial infarction and without residual ischemia, exercise-induced ST segment elevation in Q leads is an uncommon finding and it is related to a more damaged coronary microcirculation and to less viable myocardium.

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.

Relationship between T-wave normalization on exercise ECG and myocardial functional recovery in patients with acute myocardial infarction

BACKGROUND

Several studies suggested that T-wave normalization (TWN) in exercise ECG indicates the presence of viable myocardium. But the clinical implication of this phenomenon in patients with acute myocardial infarction who received proper revascularization therapy was not determined. Precisely the aim of this study was to investigate the relationship between TWN in exercise ECG and myocardial functional recovery after acute myocardial infarction.

METHODS

We studied 30 acute myocardial infarction patients with negative T waves in infarct related electrocardiographic leads and who had received successful revascularization therapy. Exercise ECG was performed 10-14 days after infarct onset using Naughton protocol. Patients were divided into 2 groups according to presence (group I; n = 14) or not (group II; n = 16) of TWN in exercise ECG. Exercise parameters and coronary angiographic findings were compared between groups. Baseline and follow-up (mean 11 months) regional and global left ventricular function was analyzed by echocardiography.

RESULTS

Exercise parameters were similar between groups. There was no difference in baseline ejection fraction and wall motion score between group I and II (EF; 56 +/- 12% vs 52 +/- 11%, p = ns. WMS; 21 +/- 3 vs 23 +/- 4, p = ns) and it was improved at the tenth month by similar magnitude (group I/group II, EF% change = 12 +/- 12% vs 7 +/- 6%, p = ns, WMS% change = 6 +/- 6% vs 7 +/- 5%, p = ns). The finding of no relation between TWN and functional recovery was observed also when the patients were analysed according to infarct location and presence or absence of Q-waves.

CONCLUSION

As the exercise-induced TWN in patients with acute myocardial infarction was not related with better functional recovery of dysfunctional regional wall motion and ejection fraction, TWN does not appear to be an indicator of myocardial viability.

Significance of both negative T waves and stress-induced normalization of the repolarization phase in infarcted patients: a positron-emission-tomography assessment of regulation of myocardial blood flow and viability of myocardium

BACKGROUND

The clinical correlation of stress-induced normalization of previously negative T waves (NNTW) to regulation of regional myocardial blood flow (MBF) and tissue viability is still being debated.

OBJECTIVE

To clarify its meaning.

METHODS

We studied 25 patients, who had previously suffered anterior myocardial infarction and for whom negative T waves were recorded on baseline electrocardiographic precordial leads, by means of positron emission tomography. We obtained MBF in the infarcted myocardial regions under resting conditions for all patients, during infusion of dipyridamole (17 patients) and dobutamine (20 patients), using [13N]-ammonia as a flow tracer.

RESULTS

During stress tests, 13 patients exhibited NNTW (group 1) whereas the remaining 12 presented persistent negative T waves (group 2). NNTW was observed in 18 stress studies (for 10 and eight patients during administration of dobutamine and dipyridamole, respectively) whereas persistent negative T waves occurred 19 times (for 10 patients during infusion of dobutamine and nine patients during administration of dipyridamole). A complete concordance of the modifications of the repolarization phase was observed for patients who were subjected both to dipyridamole and to dobutamine studies. Furthermore, we assessed viability of myocardium in 20 of 25 patients using [18F]-fluorodeoxyglucose. For the remaining five patients not subjected to metabolic imaging, a coronary reserve of 1.65 was considered a cut-off of viability. Resting MBF for patients in groups 1 and 2 were similar (0.53 +/- 0.20 versus 0.47 +/- 0.17 ml/min per g, respectively, NS) whereas during pharmacological stress, MBF of patients in group 1 was significantly higher than that for patients in group 2 (0.99 +/- 0.41 versus 0.56 +/- 0.26 ml/min per g, respectively, P < 0.0001). Coronary vasodilating capability, expressed as stress/resting MBF ratio, turned out to be 1.88 +/- 0.49 and 1.16 +/- 0.37 for patients in groups 1 and 2, respectively (P < 0.0001). We observed no difference in mean exercise work load (9.6 +/- 2.80 versus 8.46 +/- 2.18 min, NS) and rate- pressure product (24230 +/- 6425 versus 24207 +/- 8146 mmHg beats/ min, NS) at peak for the two categories of patients. All 13 patients in group 1 (100%) had viable myocardium in the anterior infarcted areas whereas only one of 12 patients in group 2 did (9%, P< 0.0001 versus group 1). Finally, a subanalysis for the specific pharmacological agent used was performed and it gave similar results.

CONCLUSION

Regardless of the specific stress test able to elicit the electrocardiographic sign, infarcted dysfunctional areas with stress-induced NNTW were demonstrated to have a higher coronary vasodilating capability and a greater probability of viability of myocardium than had persistent negative T wave regions. Therefore, detection of NNTW appears to be a cheap first-line method for the identification both of a better preserved coronary microcirculatory function and of the persistence of viability of myocardium in the infarcted areas.

Exercise versus dobutamine-induced ST elevation in the infarct-related electrocardiographic leads: clinical significance and correlation with functional recovery

BACKGROUND

The clinical significance of stress-induced ST elevation early after acute myocardial infarction and its relation to functional recovery remain controversial. The aims of this study were (1) to determine the incidence of ST elevation during dobutamine and exercise tests and (2) to assess the relative accuracy of exercise and dobutamine ST elevation for predicting functional recovery after acute myocardial infarction.

METHODS AND RESULTS

We investigated 52 patients who underwent supine exercise (from 25 W to maximal charge) and dobutamine (from 5 to 40 microg/kg per minute and up to 1 mg atropine) stress electrocardiography in the same position. ST elevation was defined as new or worsening at >1 mm, 80 ms after J point. Echocardiography and quantitative angiography were available in all patients before hospital discharge. The follow-up resting echocardiogram was recorded 30 +/- 6 days after the acute event. ST elevation developed during 30 (58%) dobutamine and 24 (46%) exercise tests. The sum of ST elevation was higher during dobutamine testing (7.7 +/- 3.8 mm) than during exercise (5.5 +/- 2.5 mm) (P =.03). A low peak creatine kinase level was the single independent predictor of dobutamine-induced ST elevation. Functional improvement occurred in 35 patients. Two independent predictors of functional recovery were selected from multivariate analysis: dobutamine ST elevation (chi(2) = 9.1; P =.0026) and low peak creatine kinase level (chi(2) = 5.1; P =.025). When dobutamine ST elevation was not included in multivariate analysis, exercise-induced ST elevation emerged as an independent predictor of functional recovery (chi(2) = 5.0; P =.023). Significant linear correlation was found between the sum of ST elevation at peak dobutamine stress and the extent of functional recovery (r = 0.87; P <.0001). In contrast, no correlation was observed with exercise ST elevation (r = 0.06; P = not significant).

CONCLUSIONS

Stress-induced ST elevation is an ancillary sign of viable myocardium that can recover. The sum of ST elevation at peak dobutamine stress correlates with the extent of functional recovery.

ST-segment elevation on Q-leads during exercise in patients with ST-segment elevation at rest after myocardial infarction

INTRODUCTION

ST-segment elevation on Q-leads after an acute myocardial infarction is related to a greater infarct size. The meaning of a further exercise-induced ST-segment elevation in these patients has not been analyzed.

METHOD

Thirty-six patients with ST-segment elevation on Q-leads were studied after a first acute myocardial infarction. Exercise testing and cardiac catheterization were performed at the first week. Left ventricular volumes (ml/m(2)); the extent of abnormal wall motion (AWM: chords); contractile reserve (AWM improvement with low dose dobutamine) and coronary patency in the culprit artery were analyzed. Cardiac catheterization was repeated at the sixth month in 20 patients; systolic recovery (AWM improvement), left ventricular volumes and coronary patency were again evaluated.

RESULTS

Patients with exercise-induced ST-segment elevation in two or more Q-leads (n=21) showed lesser contractile reserve (6+/-6 vs. 12+/-7 chords, P=0.01) than patients without exercise-induced ST-segment elevation (n=13). AWM (F=8.1) and absence of exercise-induced ST-segment elevation (F=9.5; positive predictive value: 80%; negative predictive value: 68%) were the only independent predictors of contractile reserve. Nevertheless, this electrocardiographic sign was not related to left ventricular volumes, coronary patency or systolic function and it did not predicted late systolic recovery.

CONCLUSIONS

In patients with baseline ST-segment elevation on Q-leads an exercise-induced ST-segment elevation is independently related to a lesser contractile reserve but not to the evolution of volumes or regional dysfunction during the first 6 months post-infarction. Therefore, the clinical value of this sign seems to be limited to the non-invasive detection of myocardial viability during the early post-infarction phase.

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

We followed 229 consecutive patients exhibiting negative T waves on infarct-related electrocardiographic leads; these patients underwent dobutamine stress echocardiography within 10 days after a first uncomplicated acute myocardial infarction. T-wave normalization, but not ST-segment elevation, recognized patients at higher risk of cardiac events and optimized the prognostic accuracy of both myocardial viability and ischemia, to which it was correlated and became an independent predictor in cases of subdiagnostic stress echocardiography.

Significance of spontaneous normalization of negative T waves in infarct-related leads during healing of anterior wall acute myocardial infarction

This study was conducted to elucidate the significance of spontaneous normalization of negative T waves in infarct-related leads during the chronic phase of anterior wall acute myocardial infarction. Results of this study indicate that patients with spontaneous normalization of negative T waves in infarct-related leads between 1 and 6 months after anterior wall acute myocardial infarction have smaller infarct size, decreased left ventricular dysfunction, and greater improvement in left ventricular wall motion in the infarct area, suggesting that T-wave normalization represents functional recovery of viable myocardium in the infarct area.

Relation between exercise and dobutamine stress-induced wall motion abnormalities and severity and location of stenosis in single-vessel coronary artery disease

BACKGROUND

Quantitative coronary angiography has been shown to allow accurate assessment of coronary stenosis. Exercise and dobutamine stress echocardiography both are established methods for assessing the functional importance of coronary stenosis. The relation, however, between exercise and dobutamine stress-induced wall motion abnormalities and the severity and location of stenosis remains controversial.

METHODS AND RESULTS

Thirty patients with single-vessel coronary artery disease with >/=50% minimal luminal reduction and stable angina participated in the study. Severity of coronary artery stenosis was assessed by means of computed angiography. During peak exercise echocardiography 23 patients had wall motion abnormalities and 7 did not. A positive test result was associated with severity of stenosis >/=80% for 65% of stenoses (P <.05 versus severity of stenosis <80%) and with a proximal location of 94% of stenoses (P <.01 versus middle and distal stenoses). A significant correlation was found between area of stenosis and difference in wall motion score between rest and peak exercise (r = 0.53, P <.01). The proportion of positive exercise stress was greater among stenoses with severity <80% (62% versus 46% dobutamine stress, P <.05). During dobutamine stress echocardiography 18 patients had wall motion abnormalities and 12 patients did not. A positive test result was associated with severity of stenosis >/=80% in 72% of stenoses (P <.05 versus severity of stenosis <80%) and with a proximal location in 81% of stenoses (P <.01 versus middle and distal stenoses). A weak correlation was found between area of stenosis and difference in wall motion score between rest and peak dobutamine stress (r = 0.37, P <.05).

CONCLUSIONS

Among patients with single-vessel coronary artery disease, positive stress echocardiographic test results usually are associated with proximal >/=80% stenosis. Patients with <80% stenoses are more likely to have a positive exercise stress test result than a positive dobutamine stress test result.

Significance of T-wave changes during early dobutamine stress echocardiography in patients with Q-wave acute myocardial infarction

The relation between T-wave changes and regional contraction during dobutamine stress echocardiography at low (5 to 10 microg/kg/min) and high (20 to 40 microg/kg/min) doses in 43 consecutive patients, early (7+/-2 days) after first recent Q-wave acute myocardial infarction has been evaluated. T-wave changes detected in > or =2 infarct-related electrocardiographic leads during dobutamine infusion were defined as follow: (1) negative T waves becoming positive, (2) positive T waves becoming upright > or =2 mm, and (3) negative T waves becoming upright > or =2 mm from baseline. Wall motion score index (WMSI) was defined as the sum of the echocardiographic scores of 16 segments divided by total segments considered at baseline, and at low and peak doses of dobutamine. Patients were classified according to the absence or presence of dobutamine T-wave changes. Those without T-wave changes had a significantly higher WMSI at rest (1.68+/-0.23 vs 1.50+/-0.21; p <0.05) and at peak (1.77+/-0.34 vs 1.51+/-.30 p <0.05) of dobutamine stress testing, without higher incidence of viability, homozonal, and heterozonal ischemia and chest pain. The angiographic patterns were similar between groups. Regression analysis showed a significant correlation between WMSI and T-wave amplitude at baseline (R = 0.38, p = 0.01) and at peak dobutamine stress testing (R = 0.50, p = 0.0006). The sensitivity sensitivity, specificity, and accuracy of T-wave changes to detect myocardial viability were 0.27, 0.84, and 0.70, respectively. The sensitivity, specificity, and accuracy of T-wave changes to detect homozonal ischemia were 0.76, 0.27, and 0.46, respectively. In conclusion, dobutamine-induced T-wave changes are associated with a greater extent of wall motion abnormalities both at rest and at peak stress echocardiography, but they are of little value in predicting myocardial viability when analyzed early after myocardial infarction.

Significance of dobutamine-induced ST-segment evaluation and T-wave pseudonormalization in patients with Q-wave myocardial infarction: simultaneous evaluation by dobutamine stress echocardiography and thallium-201 SPECT

The clinical significance of stress-induced ST-segment elevation and T-wave pseudonormalization in infarct-related leads is still controversial. Therefore, we conducted the present study to assess this issue using simultaneous dobutamine stress echocardiography (DSE) and thallium-201 single-photon emission computed tomography. A total of 119 patients with Q-wave myocardial infarction were enrolled in this study. There were 58 patients with (group I) and 61 patients without (group II) dobutamine-induced ST-T changes. Left ventricular ejection fraction was 43 +/- 13% in group I and 49 +/- 14% in group II (p <0.05). The baseline, low-, and peak-dose global wall motion scores were similar between these 2 groups (26.2 +/- 6.1 vs 26.2 +/- 6.3 [p = NS]; 24.1 +/- 5.3 vs 23.5 +/- 5.7 [p = NS]; 26.4 +/- 5.7 vs 26.7 +/- 6.1 [p = NS]). The sensitivity, specificity, and accuracy of these ST-T changes for detecting residual myocardial viability and ischemia documented by DSE in all patients were 50%, 53%, and 51% (for viability), and 47%, 48%, and 47% (for ischemia), respectively. The sensitivity, specificity, and accuracy of these ST-T changes for detecting a reversible perfusion defect documented by thallium-201 single-photon emission computed tomography were 51%, 54%, and 52%, respectively. In conclusion, dobutamine-induced ST elevation and/or T-wave pseudonormalization is associated with poor resting left ventricular function. These ST-T changes are not associated with residual myocardial ischemia and viability in the infarct area. Therefore, these electrocardiographic changes alone cannot be reliably considered as distinctive markers in formulating the therapeutic strategy of coronary intervention.

ST-segment elevation on Q leads at rest and during exercise: relation with myocardial viability and left ventricular remodeling within the first 6 months after infarction

BACKGROUND

Resting ST-segment elevation on Q leads after an acute myocardial infarction has been related to a greater infarct size. Otherwise, the relation between exercise-induced ST-segment elevation and myocardial viability is controversial. We investigated the relation between ST-segment elevation on Q leads at rest and during exercise and regional dysfunction and its evolution, contractile reserve, left ventricular dilation, and coronary patency.

METHODS AND RESULTS

Exercise testing and cardiac catheterization were performed at the first week after infarction in 51 patients. The study group was divided according to the existence (in 2 or more Q leads; n = 36) or not (n = 15) of resting ST-segment elevation and according to the existence (n = 28) or not (n = 23) of exercise-induced ST-segment elevation. Left ventricular end-diastolic and end-systolic volumes (mL/m2), regional wall motion (SD/chord), contractile reserve (wall motion percentage improvement with low-dose dobutamine), and coronary patency in the culprit artery were analyzed. Cardiac catheterization was repeated at the sixth month in 35 patients; systolic recovery (wall motion percentage improvement), left ventricular volumes, and coronary patency were again evaluated. Patients with resting ST-segment elevation showed poorer wall motion (2.1 +/- 0.8 SD/chord vs 1.2 +/- 1 SD/chord, P =.002), lesser contractile reserve (17% [0% to 39%] vs 41% [4% to 92%], P =.04), greater end-systolic volume (32 +/- 15 mL/m2 vs 23 +/- 11 mL/m2, P =.04), and higher percentage of occlusion (36% vs 7%, P =.04) than did patients without ST-segment elevation. Likewise, patients with exercise-induced ST-segment elevation showed lesser contractile reserve (8% [0% to 40%] vs 35% [12% to 86%], P =.03) than did patients without exercise-induced ST-segment elevation. The only independent predictors of contractile reserve were wall motion <2 SD/chord (odds ratio [OR] 7.1, confidence interval [CI] 6.3 to 7.9, P =.01) and the absence of exercise-induced ST-segment elevation (OR 5.7, CI 4.9 to 6.5, P =. 02). There were no significant differences between patients with and those without ST-segment elevation (at rest or during exercise) in systolic recovery or left ventricular volumes at the sixth month.

CONCLUSIONS

ST-segment elevation on Q leads at rest is related to a poorer systolic function (more severe regional dysfunction, greater end-systolic volume, and less response to dobutamine). ST-segment elevation during exercise is independently related to a lesser contractile reserve. ST-segment elevation (at rest or during exercise) is not related to the evolution of volumes or regional dysfunction during the first 6 months after infarction.

Reciprocal ST-segment depression associated with exercise-induced ST-segment elevation indicates residual viability after myocardial infarction

OBJECTIVES

We evaluated the clinical significance of reciprocal ST-segment depression associated with exercise-induced ST-segment elevation for detecting residual viability within the infarcted area.

BACKGROUND

Although the relation between residual viability and exercise-induced ST-segment elevation has been described, there are no reports focusing on the relation between myocardial viability and reciprocal ST-segment depression associated with exercise-induced ST-segment elevation.

METHODS

We evaluated regional blood flow and glucose utilization using N-13 ammonia (NH3) and F-18 fluorodeoxyglucose (FDG) positron emission tomography (PET) in 30 patients with a previous Q-wave myocardial infarction (anterior in 15, inferior in 15). All subjects had single-vessel disease and had exercise-induced ST-segment elevations (> or =1 mm) in electrocardiographic leads.

RESULTS

Reciprocal ST-segment depression (> or =1 mm) was present in 16 patients (Group A; anterior in 6, inferior in 10) but not in the remaining 14 patients (Group B). The degree of exercise-induced ST-segment elevation (1.8+/-0.2 vs. 2.0+/-0.2 mm) and the time from the onset of infarction to the study (75+/-49 vs. 74+/-52 days) did not differ between groups. There were no significant differences between groups in the severity of left ventricular dysfunction and the residual luminal narrowing in the infarct-related artery (45+/-21 vs. 48+/-25%). The presence and site of infarction were confirmed by NH3-PET in all patients. FDG-PET demonstrated residual tissue viability within infarct-related area in all patients in Group A and in 3 (21%) of 14 patients in Group B (p < 0.01). The sensitivity, specificity and accuracy of reciprocal ST-segment depression associated with exercise-induced ST-segment elevation for detecting residual viability were 84%, 100% and 90%, respectively.

CONCLUSIONS

The occurrence of reciprocal ST-segment depression associated with exercise-induced ST segment elevation in patients with a previous Q-wave infarction who had single-vessel disease indicates residual tissue viability within the infarct-related area.

ST-segment elevation during dobutamine stress testing predicts functional recovery after acute myocardial infarction

OBJECTIVES

The aims of this study were (1) to assess the relation between ST-segment elevation and wall motion response occurring during dobutamine testing and (2) to evaluate the usefulness of stress-induced ST-segment elevation for predicting functional recovery after acute myocardial infarction.

BACKGROUND

Clinical significance of stress-induced ST-segment elevation after acute myocardial infarction remains controversial. According to previous studies, it may reflect a larger infarcted area, depressed left ventricular function, left ventricular aneurysm, stress-induced dyskinesia, residual myocardial ischemia, or viability in the affected region. Whether transient ST-segment elevation occurring during dobutamine testing may predict functional recovery is unknown.

METHODS AND RESULTS

We studied 38 patients who underwent dobutamine stress testing early (5 +/- 2 days) after a first acute myocardial infarction. Dobutamine was infused at increasing doses from 5 to a maximum of 40 microg/kg per minute, with the addition of up to 1 mg of atropine if the target rate could not be reached by dobutamine alone. Twelve-lead electrocardiography and cross-sectional echocardiography were continuously monitored throughout the test. Dobutamine-induced ST-segment elevation was defined as a new or worsening >/=1 mm elevation, 80 ms after J point, in >/=2 infarct-related leads. Quantitative angiography was available in all patients before hospital discharge. Follow-up resting echocardiography was recorded in all patients 12 to 18 months after the acute event. ST-segment elevation was observed in 20 of the 38 patients. There were no significant differences between patients with and those without dobutamine-induced ST-segment elevation in age, site of infarction, peak level of total creatine kinase enzyme, and use of thrombolytic therapy, angioplasty, or both. Persistent akinesis without change during dobutamine stress testing was more frequently observed in patients without ST elevation (P <. 05). A biphasic response during dobutamine testing was more frequently observed in patients with ST-segment elevation (P =.01). Multivariate analysis selected 2 independent variables associated with ST-segment elevation: a biphasic response during dobutamine stress (chi-square = 7.3; P =.007) and the minimal lumen diameter of the infarct-related vessel at quantitative angiography (chi-square = 5.5; P <.02). Functional recovery was demonstrated in 26 patients. Sensitivity of ST-segment elevation for the prediction of functional recovery was 69%, specificity 83%, positive predictive value 90%, and accuracy 74%. Two independent variables predicting functional recovery were selected: dobutamine-induced ST-segment elevation (chi-square = 9.1; P =.003) and a biphasic response during stress (chi-square = 6.15; P =.013).

CONCLUSIONS

Dobutamine-induced ST-segment elevation in the infarct-related leads is an ancillary sign of viable myocardium in jeopardy. It has a high specificity and an acceptable sensitivity for the prediction of functional recovery after acute myocardial infarction.

Echocardiographic studies of dobutamine-induced ST-segment elevation before and after coronary artery bypass grafting in patients with old Q-wave myocardial infarction

There is a controversy regarding the functional significance of stress-induced ST-segment elevation (STE) in Q leads. However, the effect of revascularization on the induction of STE was not investigated. We studied 35 patients with old Q-wave myocardial infarction who underwent coronary artery bypass grafting (CABG) of the infarct-related artery with dobutamine (up to 40 microg/kg per minute) stress echocardiography before and 3 months after CABG. Ischemia was defined as new or worsened wall motion abnormalities. Functional recovery was defined as a reduction of regional wall motion score of 1 or more in 2 or more segments from the pre-CABG to post-CABG resting echocardiogram with the use of the 16-segment/5-grade score model. STE (>/=0.1 mV J-point elevation lasting 80 ms in >/=2 Q leads) occurred in 20 (57%) patients. There was no significant difference between patients with and those without STE before CABG with regard to the prevalence of peri-infarction ischemia (85% vs 80%) or index of improvement of regional function after CABG (0.26 +/- 0.26 vs 0.29 +/- 0.33). STE was reinduced to the same level in 4 patients after CABG, whereas 16 patients showed absent reinduction (8 patients) or reduced level (8 patients) of STE. Functional changes associated with absent reinduction or less STE after CABG were absence of reinduction of regional ischemia in 13 patients, improvement of resting regional function in 5 patients, and resection of scarred segments in 4 patients. Among the 4 patients with persistent dobutamine-induced STE, 1 patient had persistent ischemia and 2 showed worsening of resting regional function. Although dobutamine-induced STE in patients with old Q-wave infarction referred for CABG cannot identify patients with a higher prevalence of ischemia, the lack of reinduction of this pattern after CABG correlates with absent reinduction of ischemia in most of patients.

Significance of exercise-induced ST-segment elevation and T-wave pseudonormalization for improvement of function in healed Q-wave myocardial infarction

Exercise-induced ST-segment elevation and pseudonormalization of negative T waves (ST-T segment changes) in infarct leads indicate myocardial viability after Q-wave myocardial infarcts in some patients and may therefore identify patients who will benefit from revascularization. Global left ventricular ejection fraction and wall motion abnormalities of the left ventricle were analyzed in 34 patients with healed myocardial infarction (11 patients with ST-segment elevation, 3 patients with pseudonormalization of the negative T wave (group 1), and in 20 patients without ST-T segment changes during an exercise electrocardiogram (group 2)) before and 4 months after successful revascularization. Wall motion abnormality in the central infarct region at baseline was similar in both groups (-3.1 +/- 0.6 SD vs 3.0 +/- 0.8 SD; NS). At repeat angiography, wall motion abnormality improved significantly from -3.1 +/- 0.6 SD to -2.1 +/- 0.6 SD (p <0.01) in group 1 and was unchanged in group 2 (-3.0 +/- 0.8 SD vs -2.9 +/- 0.7 SD; NS). Similarly, ejection fraction at control angiography had increased from 54 +/- 14% to 66 +/- 12% (p <0.01) in group 1, but decreased from 56 +/- 9% to 55 +/- 9% in group 2 (NS). Exercise-induced ST-T segment changes yielded a sensitivity of 80% and a specificity of 89% to predict significant improvement of the left ventricular ejection fraction. Exercise-induced changes of the ST-T segment identify patients with a high probability of improvement of myocardial function after revascularization in patients with healed myocardial infarcts.

T wave normalization in infarct-related electrocardiographic leads during exercise testing for detection of residual viability: comparison with positron emission tomography

OBJECTIVES

We investigated the sensitivity and specificity of exercise-induced T wave normalization (TWN) in infarct-related electrocardiographic leads (IRLs) for detection of residual viability in the infarct area.

BACKGROUND

The meaning of exercise-induced TWN on IRLs is not yet well understood. Recent reports suggest that TWN during dobutamine echocardiography could indicate the presence of viable myocardium.

METHODS

We evaluated 40 consecutive patients with a recent acute myocardial infarction and negative T waves in at least two IRLs. All patients underwent exercise testing; positron emission tomography (PET) with nitrogen-13 ammonia and fluorine-18 fluorodeoxyglucose; and coronary angiography.

RESULTS

Twenty-four patients showed exercise-induced TWN: 18 at a work load < or =50 W (group la) and 6 at a work load > or =75 W (group 1b); 16 patients did not show TWN (group 2). On the PET study, viability in the infarct area was present in 17 patients (94%) from group la, in only 1 (16%) from group 1b and in 4 (25%) from group 2 (p < 0.0001). The sensitivity, specificity and diagnostic accuracy of exercise-induced TWN, in comparison with residual viability, were, respectively, 82%, 67%, 75% for TWN at every work load and 77%, 94%, 85% for TWN at a work load < or =50 W. Moreover, the sensitivity and diagnostic accuracy of TWN at the low work load were higher for anterior infarctions (87% and 88%, respectively).

CONCLUSIONS

Exercise-induced TWN on IRLs at low work loads is a sensitive and specific index for the presence of residual viability in the infarct area. Sensitivity and diagnostic accuracy of this sign are higher for anterior infarctions.

Relationship between normalization of negative T waves on exercise ECG and residual myocardial viability in patients with previous myocardial infarction and no post-infarction angina

The usefulness of normalization of negative T waves in exercise ECG was investigated as an index of myocardial viability in patients with previous myocardial infarction with no symptoms or ischemic ST-segment change during exercise test. A total of 39 patients, 20 with T-wave normalization (POS group) and 19 without T-wave normalization (NEG group) on exercise ECG. were studied. Myocardial viability was evaluated by thallium-201 single-photon emission computed tomography (SPECT) during exercise or at rest. We also assessed left ventricular ejection fraction (LVEF) by contrast ventriculography before (n=39) and after percutaneous transluminal coronary angioplasty (PTCA) (n=17). SPECT detected myocardial viability in 16 (80%) of the 20 patients in the POS group and in 4 (21%) of the 19 patients in the NEG group (p<0.01). LVEF increased after successful PTCA in the POS group (from 53+/-13% to 63+/-8%, p<0.025), but fell in the NEG group (from 57+/-10% to 51+/-8%). It is concluded that normalization of negative T waves on exercise ECG is a useful, simple index of myocardial viability in patients with previous myocardial infarction with no symptoms or ischemic ST-segment change during exercise testing.

Dobutamine-induced ST-segment elevation in patients with acute myocardial infarction and the role of myocardial ischemia, viability, and ventricular dyssynergy

We analyzed the relation between dobutamine-induced Q-wave ST-segment elevation and regional contraction during low (5 to 10 microg/kg/min) and high doses (20 to 40 microg/kg/min) of dobutamine in a series of 391 dobutamine echocardiographic tests performed 10 +/- 2 days after a first uncomplicated acute myocardial infarction (AMI). ST-segment elevation was defined as > or = 1 mm new or additional J-point elevation with a horizontal or upsloping ST segment lasting 80 ms. Wall motion score index at rest was derived using a 16 segment-4 grade score model. Patients with dobutamine-induced ST-segment elevation had a higher wall motion score index at rest (anterior wall AMI: 1.67 +/- 0.27 vs 1.43 +/- 0.30, p = 0.0001; inferior wall AMI: 1.44 +/- 0.27 vs 1.30 +/- 0.18, p = 0.0001) and similar incidence and extent of myocardial viability and homozonal ischemia in comparison with those without ST-segment elevation. The sensitivity, specificity, and accuracy of dobutamine-induced ST-segment elevation for detecting residual homozonal ischemia were 51%, 55%, and 54%, respectively, in patients with anterior wall AMI, and 42%, 68%, and 58%, respectively, in patients with inferior wall AMI. In conclusion, dobutamine-induced ST-segment elevation is not associated with higher incidence and extent of viable or jeopardized myocardium but rather to a greater extent of wall motion abnormalities at rest. Thus, this finding does not represent a clinically reliable discriminator for selecting patients for coronary angiography and possible revascularization procedures.

Relation between ST segment elevation during dobutamine stress test and myocardial viability after a recent myocardial infarction

OBJECTIVE

To assess the relation between ST segment elevation during the dobutamine stress test and late improvement of function after acute Q wave myocardial infarction.

PATIENTS AND DESIGN

70 patients were studied a mean (SD) 8 (3) days after acute myocardial infarction with high dose dobutamine-atropine stress echocardiography and a follow up echocardiogram at 85 (10) days. A score model based on 16 segments and four grades was used to assess left ventricular function. Functional improvement was defined as a reduction of wall motion score > or = 1 in > or = 1 segments at follow up.

INTERVENTION

Myocardial revascularisation was performed in 23 patients (33%) before follow up studies.

RESULTS

ST segment elevation occurred in 40 patients (57%). Late functional improvement occurred in 35 patients (50%). Functional improvement was more common in patients with ST segment elevation (68% v 30%, P < 0.005) and they had a higher mean (SD) number of improved segments at follow up (1.9 (2.2) v 0.5 (1.1), P < 0.005). The wall motion score index decreased between baseline and follow up in patients with ST segment elevation (1.54 (0.50) v 1.48 (0.43), P < 0.05) but not in patients without ST segment elevation (1.39 (0.60) v 1.45 (0.47)). The accuracy of ST segment elevation for the prediction of functional improvement was similar to that of low dose dobutamine echocardiography in patients with anterior infarction (80% v 83%) and in patients who underwent revascularisation (78% v 83% respectively).

CONCLUSION

In patients with a recent Q wave myocardial infarction, dobutamine-induced ST segment elevation is a valuable marker of myocardial viability particularly when the test is performed without or with suboptimal echocardiographic imaging.