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

Residual ST-segment elevation to predict long-term clinical and CMR-derived outcomes in STEMI

Residual ST-segment elevation after ST-segment elevation myocardial infarction (STEMI) has traditionally been considered a predictor of left ventricular (LV) dysfunction and ventricular aneurism. However, the implications in terms of long-term prognosis and cardiac magnetic resonance (CMR)-derived structural consequences are unclear. A total of 488 reperfused STEMI patients were prospectively included. The number of Q wave leads with residual ST-segment elevation > 1 mm (Q-STE) at pre-discharge ECG was assessed. LV ejection fraction (LVEF, %) and infarct size (IS, % of LV mass) were quantified in 319 patients at 6-month CMR. Major adverse cardiac events (MACE) were defined as all-cause death and/or re-admission for acute heart failure (HF), whichever occurred first. During a mean follow-up of 6.1 years, 92 MACE (18.9%), 39 deaths and 53 HF were recorded. After adjustment for baseline characteristics, Q-STE (per lead with > 1 mm) was independently associated with a higher risk of long-term MACE (HR 1.24 [1.07-1.44] per lead, p = 0.004), reduced (< 40%) LVEF (HR 1.36 [1.02-1.82] per lead, p = 0.04) and large (> 30% of LV mass) IS (HR 1.43 [1.11-1.85] per lead, p = 0.006) at 6-month CMR. Patients with Q-STE ≥ 2 leads (n = 172, 35.2%) displayed lower MACE-free survival, more depressed LVEF, and larger IS at 6-month CMR (p < 0.001 for all comparisons). Residual ST-segment elevation after STEMI represents a universally available tool that predicts worse long-term clinical and CMR-derived structural outcomes.

Dobutamine-induced myocardial ischemia and ST-segment elevation in collateral-dependent myocardium

In patients with obstructive coronary artery disease, electrocardiographic (ECG) ST-segment elevation (STE) is frequently seen during dobutamine stress echocardiography (DSE) in leads overlying previous transmural left ventricular (LV) myocardial infarction. The mechanism of occasional STE during DSE in LV region with inducible myocardial ischemia and no previous myocardial infarction has not been well delineated. We retrospectively identified 28 adults (age 51 to 83 years [69 ± 8]; 82% men) with STE (>1 mm at ≥80 ms after J point in ≥2 contiguous leads without pathologic Q waves) and inducible myocardial ischemia in the same territory during DSE. STE occurred in inferior (n = 16), inferolateral (n = 8), anterior (n = 1), lateral (n = 2), or anterolateral (n = 1) leads and was associated with ischemic symptoms in 17 patients (61%). Inducible LV wall motion abnormality developed in LV segments corresponding to ECG STE in all patients. Coronary arteriography (within 1 week of the index DSE) showed severe luminal narrowing in the major epicardial coronary artery supplying the region with DSE STE and ischemia (90% to 99% in 9 patients [32%] and 100% in 19 patients [68%]). The ischemic region was supplied by ipsilateral (n = 4 [14%]), contralateral (n = 21 [75%]), or both ipsilateral and contralateral (n = 3 [11%]) collateral branches. In conclusion, dobutamine-induced ECG STE in LV segments with normal baseline wall motion is a highly reliable marker of viable collateral-dependent myocardium.

Myocardial viability: what we knew and what is new

Some patients with chronic ischemic left ventricular dysfunction have shown significant improvements of contractility with favorable long-term prognosis after revascularization. Several imaging techniques are available for the assessment of viable myocardium, based on the detection of preserved perfusion, preserved glucose metabolism, intact cell membrane and mitochondria, and presence of contractile reserve. Nuclear cardiology techniques, dobutamine echocardiography and positron emission tomography are used to assess myocardial viability. In recent years, new advances have improved methods of detecting myocardial viability. This paper summarizes the pathophysiology, methods, and impact of detection of myocardial viability, concentrating on recent advances in such methods. We reviewed the literature using search engines MIDLINE, SCOUPS, and EMBASE from 1988 to February 2012. We used key words: myocardial viability, hibernation, stunning, and ischemic cardiomyopathy. Recent studies showed that the presence of viable myocardium was associated with a greater likelihood of survival in patients with coronary artery disease and LV dysfunction, but the assessment of myocardial viability did not identify patients with survival benefit from revascularization, as compared with medical therapy alone. This topic is still debatable and needs more evidence.

Analysis of the extension of Q-waves after infarction with body surface map: Relationship with infarct size

AIMS

We aimed to characterize the extension of Q-waves after a first ST-segment elevation myocardial infarction using body surface map (BSM) and its relationship with infarct size quantified with cardiovascular magnetic resonance imaging (CMR).

METHODS AND RESULTS

Thirty-five patients were studied 6 months after a first ST-segment elevation myocardial infarction (23 anterior, 12 inferior). All cases had single-vessel disease and an open artery. The extension of Q-waves was analyzed by means of a 64-lead BSM. Infarct size was quantified with CMR. Absence of Q-waves in BSM was observed in 5 patients (14%), 2 of whom (40%) had >1 segment with transmural necrosis. Absence of Q-waves in 12-lead ECG was observed in 8 patients (23%), 7 of whom (87%) had >1 segment with transmural necrosis. Patients with inferior infarctions (n=12, 34%) showed a larger number of Q-waves in BSM (18+/-7.1 leads) than patients with anterior infarctions (n=23, 66%; 3.7+/-3.6 leads; p<0.0001). When the study group was analysed as a whole, the total number of Q-waves detected in BSM did not correlate with the number of necrotic segments (r=0.15; p=0.4). In anterior infarctions, a number of Q-waves >median (2 leads) was related to a higher number of necrotic segments (5.1+/-2.4 vs. 2+/-2.2 segments; p=0.004). The same was observed in inferior infarctions (median 20 leads: 3.5+/-1.9 vs. 1.2+/-1.2 segments; p=0.03).

CONCLUSION

In a stable phase after a first ST-segment elevation myocardial infarction, absence of Q-waves does not mean non-transmural necrosis. Using BSM, extension of Q-waves is much higher in inferior infarctions; a separate analysis depending on infarct location is necessary. A major BSM-derived extension of Q-waves is related to larger infarct size both in anterior and in inferior infarctions.

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.

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

OBJECTIVE

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

Value of the electrocardiogram in predicting left ventricular enlargement and dysfunction after myocardial infarction

To identify electrocardiographic predictors of left ventricular enlargement or persistent dysfunction following a myocardial infarction. Baseline and predischarge 12-lead electrocardiograms (ECGs) from 272 patients with anterior myocardial infarction who were enrolled in the Healing and Early Afterload Reducing Therapy trial were evaluated and related to echocardiographic data obtained at baseline and day 90. ST-segment elevation, QRS score, and number of negative T waves were assessed at both time points. The majority of patients (87%; n = 237) received reperfusion therapy. Multivariate models were used to adjust for potential confounders, including maximal creatine kinase level and ejection fraction at baseline. None of the baseline electrocardiographic variables independently predicted ventricular enlargement or recovery of function. In contrast, the sum of ST- and maximum ST-segment elevation, and the number of leads with ST-segment elevation > or =1 mm in the predischarge ECG, were independent predictors of ventricular enlargement from baseline to day 90. Each lead with ST-segment elevation > or =1 mm was associated with 3.5 mL of ventricular enlargement (95% confidence interval [CI]: 1.6 to 5.5 mL; P <0.0001). Similarly, the sum of ST-segment elevation (odds ratio [OR] = 0.78; 95% CI: 0.69 to 0.89; P <0.0001), the maximum ST-segment elevation (OR = 0.25; 95% CI: 0.13 to 0.45; P <0.0001), and the number of leads with ST-segment elevation > or =1 mm (OR = 0.58; 95% CI: 0.45 to 0.74; P <0.0001) were independently associated with a lower likelihood of recovery of function at day 90. Predischarge ECG may be a useful tool for early identification of patients at risk of ventricular enlargement and persistent dysfunction following myocardial infarction.

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.

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.

[Determinants of contractile reserve in the infarction area. A quantitative study using dobutamine in contrast left ventriculography]

AIM

The aim of this study was to relate the contractile reserve in infarction segments to the dysfunction at rest and to the residual coronary stenosis.

METHODS

The study group consisted of 95 patients with a first myocardial infarction. Contrast left ventricular at baseline and after dobutamine infusion at 7.5 microg/kg/min and coronary angiograms were performed. The centerline method was used to quantify the extent of dysfunction (percentage of chords with dysfunction in the territory of the infarction artery) and its maximum severity (maximum units of standard deviation [SD] below the normal wall motion reference). Reduction of dysfunction extent with dobutamine was measured.

RESULTS

On increasing baseline dysfunction severity, both the magnitude of the response to dobutamine ( 2 SD 3 SD 4 SD +/- 5 SD [n = 15] = 9+/-13%, > 5 SD [n = 13] = 3+/-4%, p = 0,0001), and the number of patients with a significant (> or =15%) positive response ( 2 SD 3 SD 4 SD 5 SD = 0%, p<0,0001) decreased. There were no differences in dobutamine improvement among the subgroups with (n = 84) or without (n = 11) significant stenosis in the infarction artery (18+/-15 vs. 16 +/-18%), or between the subgroups with a patent (n = 76, 18+/-19%) or occluded (n = 19, 11+/-11%) artery.

CONCLUSIONS

Dobutamine response is related to dysfunction severity in the infarction area: when the severity is 5 (high negative response prevalence), dobutamine testing does not seem indicate. The existence of residual coronary stenosis does not attenuate contractile reserve at low dobutamine doses.

Wall motion of noninfarcted myocardium. Relationship to regional and global systolic function and to early and late left ventricular dilation

We studied the wall motion of the noninfarcted area and its role in left ventricular remodeling. The study group consisted of 43 patients with a first Q-wave acute myocardial infarction and single-vessel disease. Cardiac catheterization was performed at the first week, and was repeated six months later. Left ventricular volumes, wall motion at the infarcted and noninfarcted area, ejection fraction and infarction-related artery status were quantified. Hyperkinesia was only found at the first week in 22% of cases, and at the sixth month in 26% of cases. Wall motion at the noninfarcted area correlated with wall motion at the infarcted area (one week: r=0.53 p<0.0001; six months: r=0.52 p=0.01), ejection fraction (one week: r=0.69 p<0.0001; six months: r=0.56 p=0.006), end-diastolic volume (one week: r=-0.48 p=0.002; six months: r=-0.48 p=0.02) and end-systolic volume (one week: r=-0.70 p<0.0001; six months: r=-0.64 p=0.001). The improvement of the noninfarcted area (from the first week to the sixth month) was only related to basal (one week) wall motion in this area (r=-0.58 p=0.003). We conclude that after an intermediate-large infarction, most patients exhibit a normal or hypokinetic noninfarcted area. Patients with a more depressed infarcted area show poorer contractility at the noninfarcted area. area exhibit greater progressive improvement.