Performance of angiographic, electrocardiographic and MRI methods to assess the area at risk in acute myocardial infarction

Validation of contemporary electrocardiographic indices of area at risk and infarct size in acute ST elevation myocardial infarction (STEMI)

BACKGROUND

Electrocardiographic (ECG) methods to assess area at risk (AAR) and infarct size (IS) in patients with ST-elevation myocardial infarction (STEMI) have been previously established but not validated against contemporary benchmark Cardiac Magnetic Resonance (CMR) measures. We compared ECG-determined and CMR-determined measures for (a) AAR, (b) IS, and (c) myocardial salvage.

METHODS

Sixty patients with ECG evidence of STEMI and CMR imaging performed within 13 days were included. The ECG-determined (a) AAR scores (Aldrich and Wilkins), (b) IS (Selvester score), and (c) myocardial salvage (i.e. [AAR-IS] / AAR × 100%), were compared with CMR-determined measures.

RESULTS

Compared with CMR-determined AAR, both the Wilkins & Aldrich scores underestimated AAR, although the Wilkins (r = 0.72, p < 0.001) showed a better correlation than the Aldrich (r = 0.54, p < 0.001). Bland-Altman analysis revealed a bias of 2.6% (95% limits of agreement: 18.5%, -13.3%) for the Wilkins and 5.9% (95% limits of agreement: 25.6%, -13.8%) for the Aldrich. Estimation of IS was similar between the Selvester score and CMR, with good correlation (r = 0.77, p < 0.001) and agreement (fixed bias 0.4%, 95% limits of agreement 20.8%, -15.5%). However, ECG-determined myocardial salvage significantly underestimated CMR-determined myocardial salvage, with an inverse correlation (r = -0.33, p = 0.01).

CONCLUSIONS

The Wilkins score is superior to Aldrich score as an ECG-AAR index, Selvester score is a reasonable ECG estimate of infarct size, though ECG derived myocardial salvage does not have enough accuracy to be used in the clinical setting; it may be an inexpensive surrogate for myocardial salvage in large research studies. Further validation and prognostic studies are required.

Cardiac MRI Endpoints in Myocardial Infarction Experimental and Clinical Trials: JACC Scientific Expert Panel

After a reperfused myocardial infarction (MI), dynamic tissue changes occur (edema, inflammation, microvascular obstruction, hemorrhage, cardiomyocyte necrosis, and ultimately replacement by fibrosis). The extension and magnitude of these changes contribute to long-term prognosis after MI. Cardiac magnetic resonance (CMR) is the gold-standard technique for noninvasive myocardial tissue characterization. CMR is also the preferred methodology for the identification of potential benefits associated with new cardioprotective strategies both in experimental and clinical trials. However, there is a wide heterogeneity in CMR methodologies used in experimental and clinical trials, including time of post-MI scan, acquisition protocols, and, more importantly, selection of endpoints. There is a need for standardization of these methodologies to improve the translation into a real clinical benefit. The main objective of this scientific expert panel consensus document is to provide recommendations for CMR endpoint selection in experimental and clinical trials based on pathophysiology and its association with hard outcomes.

Unexpected High Incidence of Coronary Vasoconstriction in the Reduction of Microvascular Injury Using Sonolysis (ROMIUS) Trial

High-mechanical-index ultrasound and intravenous microbubbles might prove beneficial in treating microvascular obstruction caused by microthrombi after primary percutaneous coronary intervention for ST-segment elevation myocardial infarction (STEMI). Experiments in animals have revealed that longer-pulse-duration ultrasound is associated with an improvement in microvascular recovery. This trial tested long-pulse-duration, high-mechanical-index ultrasound in STEMI patients. Non-randomly assigned, non-blinded patients were included in this phase 2 trial. The primary endpoint was any side effect possibly related to the ultrasound treatment. The study was aborted after six patients were included; three patients experienced coronary vasoconstriction of the culprit artery, unresponsive to nitroglycerin. Therefore, coronary artery diameter was measured in five pigs. Coronary artery diameters distal to the injury site decreased after application of ultrasound, after balloon injury plus thrombus injection (from 1.89 ± 0.24 mm before to 1.78 ± 0.17 after ultrasound, p = 0.05). Long-pulse-duration ultrasound might cause coronary vasoconstriction distal to the culprit vessel location.

No benefit of additional treatment with exenatide in patients with an acute myocardial infarction

OBJECTIVES

This double blinded, placebo controlled randomized clinical trial studies the effect of exenatide on myocardial infarct size. The glucagon-like peptide-1 receptor agonist exenatide has possible cardioprotective properties during reperfusion after primary percutaneous coronary intervention for ST-segment elevation myocardial infarction.

METHODS

191 patients were randomly assigned to intravenous exenatide or placebo initiated prior to percutaneous coronary intervention using 10μg/h for 30min followed by 0.84μg/h for 72h. Patients with a previous myocardial infarction, Trombolysis in Myocardial Infarction flow 2 or 3, multi-vessel disease, or diabetes were excluded. Magnetic resonance imaging (MRI) was performed to determine infarct size, area at risk (AAR) (using T2-weighted hyperintensity (T2W) and late enhancement endocardial surface area (ESA)). The primary endpoint was of 4-month final infarct size, corrected for the AAR measured in the acute phase using MRI.

RESULTS

After exclusion, 91 patients (age 57.4±10.1years, 76% male) completed the protocol. There were no baseline differences between groups. No difference was found in infarct size corrected for the AAR in the exenatide group compared to the placebo group (37.1±18.8 vs. 39.3±20.1%, p=0.662). There was also no difference in infarct size (18.8±13.2 vs. 18.8±11.3% of left ventricular mass, p=0.965). No major adverse cardiac events occurred during the in-hospital phase.

CONCLUSION

Exenatide did not reduce myocardial infarct size expressed as a percentage of AAR in ST elevated myocardial infarction patients successfully treated with percutaneous coronary intervention.

Comparison of Outcome of Patients With ST-Segment Elevation Myocardial Infarction and Complete Versus Incomplete ST-Resolution Before Primary Percutaneous Coronary Intervention

Some patients presenting with ST-segment elevation myocardial infarction (STEMI) have complete ST resolution in the electrocardiogram, which may be clinical useful in the triage of patients with STEMI. However, the importance of complete ST resolution in these patients remains uncertain. Thus, the purpose was to describe the prognosis of patients with complete ST resolution before primary percutaneous coronary intervention (PCI). Continuous ST monitoring from arrival until 90 minutes after PCI was performed in 933 patients with STEMI. Complete ST resolution was defined as no residual significant ST elevations before intervention. The patients were followed clinically for 5.5 years (range 0 to 6.8 years). Infarct size and myocardial salvage were assessed in a subgroup of patients (n = 221) by cardiovascular magnetic resonance. Complete ST resolution was observed in 24% of the patients, who had a higher incidence of Thrombolysis In Myocardial Infarction grade 2/3 flow before intervention (64% vs 24%), smaller infarct size (6% vs 11%), and higher myocardial salvage index (0.82 vs 0.69; all p <0.001) compared with patients with continuous ST elevations. Complete ST resolution was associated with a significantly lower rate of the composite end point of all-cause death and admission for heart failure (14% vs 22%; p = 0.006) although it only tended to be an independent predictor in a multivariate analysis (hazard ratio 0.69, 95% CI 0.49 to 1.06; p = 0.09). In conclusion, compared to patients without incomplete ST resolution, patients with STEMI and complete ST resolution before primary PCI have a higher incidence of normalized epicardial flow before PCI, a larger myocardial salvage and smaller infarct size after the procedure and presumably improved long-term outcome compared with incomplete ST resolution.

Remote ischemic conditioning reduces myocardial infarct size and edema in patients with ST-segment elevation myocardial infarction

OBJECTIVES

This study aimed to determine whether remote ischemic conditioning (RIC) initiated prior to primary percutaneous coronary intervention (PPCI) could reduce myocardial infarct (MI) size in patients presenting with ST-segment elevation myocardial infarction.

BACKGROUND

RIC, using transient limb ischemia and reperfusion, can protect the heart against acute ischemia-reperfusion injury. Whether RIC can reduce MI size, assessed by cardiac magnetic resonance (CMR), is unknown.

METHODS

We randomly assigned 197 ST-segment elevation myocardial infarction patients with TIMI (Thrombolysis In Myocardial Infarction) flow grade 0 to receive RIC (four 5-min cycles of upper arm cuff inflation/deflation) or control (uninflated cuff placed on upper arm for 40 min) protocols prior to PPCI. The primary study endpoint was MI size, measured by CMR in 83 subjects on days 3 to 6 after admission.

RESULTS

RIC reduced MI size by 27%, when compared with the MI size of control subjects (18.0 ± 10% [n = 40] vs. 24.5 ± 12.0% [n = 43]; p = 0.009). At 24 h, high-sensitivity troponin T was lower with RIC (2,296 ± 263 ng/l [n = 89] vs. 2,736 ± 325 ng/l [n = 84]; p = 0.037). RIC also reduced the extent of myocardial edema measured by T2-mapping CMR (28.5 ± 9.0% vs. 35.1 ± 10.0%; p = 0.003) and lowered mean T2 values (68.7 ± 5.8 ms vs. 73.1 ± 6.1 ms; p = 0.001), precluding the use of CMR edema imaging to correctly estimate the area at risk. Using CMR-independent coronary angiography jeopardy scores to estimate the area at risk, RIC, when compared with the control protocol, was found to significantly improve the myocardial salvage index (0.42 ± 0.29 vs. 0.28 ± 0.29; p = 0.03).

CONCLUSIONS

This randomized study demonstrated that in ST-segment elevation myocardial infarction patients treated by PPCI, RIC, initiated prior to PPCI, reduced MI size, increased myocardial salvage, and reduced myocardial edema.

Correlation of electrocardiogram and regional cardiac magnetic resonance imaging findings in ST-elevation myocardial infarction: a literature review

BACKGROUND

Patients with acute ST-elevation myocardial infarction (STEMI) benefit substantially from emergent coronary reperfusion. The principal mechanism is to open the occluded coronary artery to minimize myocardial injury. Thus the size of the area at risk is a critical determinant of the patient outcome, although other factors, such as reperfusion injury, have major impact on the final infarct size. Acute coronary occlusion almost immediately induces metabolic changes within the myocardium, which can be assessed with both the electrocardiogram (ECG) and cardiac magnetic resonance (CMR) imaging.

METHODS

The 12-lead ECG is the principal diagnostic method to detect and risk-stratify acute STEMI. However, to achieve a correct diagnosis, it is paramount to compare different ECG parameters with golden standards in imaging, such as CMR. In this review, we discuss aspects of ECG and CMR in the assessment of acute regional ischemic changes in the myocardium using the 17 segment model of the left ventricle presented by American Heart Association (AHA), and their relation to coronary artery anatomy.

RESULTS

Using the 17 segment model of AHA, the segments 12 and 16 remain controversial. There is an important overlap in myocardial blood supply at the antero-lateral region between LAD and LCx territories concerning these two segments.

CONCLUSION

No all-encompassing correlation can be found between ECG and CMR findings in acute ischemia with respect to coronary anatomy.

Relation of ST-segment elevation before and after percutaneous transluminal coronary angioplasty to left ventricular area at risk, myocardial infarct size, and systolic function

Electrocardiography is an excellent tool for decision making in patients with ST elevation myocardial infarction (STEMI). However, little is known on the correlation between its dynamic changes during primary percutaneous coronary intervention (PCI) and the anatomic information provided by cardiovascular magnetic resonance. The study aimed to assess the predictive value of dynamic ST-segment changes before and after PCI on myocardial area at risk (AAR), infarct size, and left ventricular function in patients with STEMI. Eighty-five consecutive patients with a first STEMI were included. An electrocardiogram was recorded before and after PCI at 1, 24, 48, 72, and 120 hours. Sum of ST elevation (sumSTE), the number of STE, and STE resolution (resSTE) were determined. Complete resSTE was defined as ≥70% resolution, and patients were classified into 3 groups: group 1 (resSTE 1 hour after PCI) n = 39; group 2 (resSTE 120 hour after PCI) n = 27; and group 3, without resSTE (n = 19). Cardiovascular magnetic resonance was performed during hospitalization and at 6 months. Left ventricular volumes, ejection fraction, AAR, infarct size, myocardial salvage index, and microvascular obstruction were determined. Before PCI, the number of STE and sumSTE were best associated with AAR (p <0.001). After PCI, lack of resSTE (group 3) was associated with larger infarct size, MVO, and lower myocardial salvage index. However, sumSTE at 120 hours after PCI best discriminated patients with larger infarct size, ventricular volumes, and lower ejection fraction during hospitalization and at follow-up. In conclusion, admission sumSTE best correlates with AAR, whereas sumSTE at 120 hours rather than early resSTE best correlates with infarct size and left ventricular volumes during hospitalization and at 6 months.

Correlating both Aldrich and Hellemond score with cardiac magnetic resonance imaging endocardial surface area calculations in the estimation of the area at risk. Electrocardiography scores and endocardial surface area calculations: do they correlate?

INTRODUCTION

Having a bedside tool such as the ECG to assess the myocardial area at risk in a patient presenting with an ST-elevation myocardial infarction would be of great value to the clinician because this could give an insight in the efficiency of intervention therapy and the left ventricular rest function.

MATERIALS AND METHODS

From the MAST database (n=106), we included 84 patients, all meeting the STEMI criteria, with a first anterior and/or inferior STEMI. From the admission ECG the Aldrich and Selvester scores were measured and the combined Hellemond score was calculated and correlated with the Cardiac Magnetic Resonance (CMR) estimated endocardial surface area (ESA) using the Spearman coefficient.

RESULTS

The correlation between the Aldrich score was r=0.55 (p-value<0.0001) and Hellemond score r=0.45 (p-value<0.0001) with ESA. After exclusion of lateral involvement the correlation increased to 0.62 (p-value<0.0001) for the Aldrich and to 0.49 (p-value<0.0001) for the Hellemond score.

CONCLUSION

The additional ECG estimation of infarcted myocardium does not improve the ECG estimation of ischemic myocardium to CMR-based ESA estimation of the myocardial area at risk. The Aldrich score could be improved for STEMIs with lateral involvement.