The ST injury vector: electrocardiogram-based estimation of location and extent of myocardial ischemia

Extent of Myocardium at Risk for Left Anterior Descending Artery, Right Coronary Artery, and Left Circumflex Artery Occlusion Depicted by Contrast-Enhanced Steady State Free Precession and T2-Weighted Short Tau Inversion Recovery Magnetic Resonance Imaging

Background—

Contrast-enhanced steady state free precession (CE-SSFP) and T2-weighted short tau inversion recovery (T2-STIR) have been clinically validated to estimate myocardium at risk (MaR) by cardiovascular magnetic resonance while using myocardial perfusion single-photon emission computed tomography as reference standard. Myocardial perfusion single-photon emission computed tomography has been used to describe the coronary perfusion territories during myocardial ischemia. Compared with myocardial perfusion single-photon emission computed tomography, cardiovascular magnetic resonance offers superior image quality and practical advantages. Therefore, the aim was to describe the main coronary perfusion territories using CE-SSFP and T2-STIR cardiovascular magnetic resonance data in patients after acute ST-segment–elevation myocardial infarction.

Methods and Results—

CE-SSFP and T2-STIR data from 2 recent multicenter trials, CHILL-MI and MITOCARE (n=215), were used to assess MaR. Angiography was used to determine culprit vessel. Of 215 patients, 39% had left anterior descending artery occlusion, 49% had right coronary artery occlusion, and 12% had left circumflex artery occlusion. Mean extent of MaR using CE-SSFP was 44±10% for left anterior descending artery, 31±7% for right coronary artery, and 30±9% for left circumflex artery. Using T2-STIR, MaR was 44±9% for left anterior descending artery, 30±8% for right coronary artery, and 30±12% for left circumflex artery. MaR was visualized in polar plots, and expected overlap was found between right coronary artery and left circumflex artery. Detailed regional data are presented for use in software algorithms as a priori information on the extent of MaR.

Conclusions—

For the first time, cardiovascular magnetic resonance has been used to show the main coronary perfusion territories using CE-SSFP and T2-STIR. The good agreement between CE-SSFP and T2-STIR from this study and myocardial perfusion single-photon emission computed tomography from previous studies indicates that these 3 methods depict MaR accurately in individual patients and at a group level.

Clinical Trial Registration—

URL: http://www.clinicaltrials.gov . Unique identifiers: NCT01379261 and NCT01374321.

Electrocardiographic prediction of lateral involvement in acute non-anterior wall myocardial infarction

PURPOSE

Recent research has established that a tall R-wave in V1 indicates lateral wall involvement in non-anterior wall myocardial infarction (MI). The objective of this study was to assess the value of the admission electrocardiogram (ECG) to predict R-waves and consequently lateral wall damage in the late phase of non-anterior MI.

METHODS

ECGs of 69 patients were analyzed. ST-segment changes in representative leads for lateral wall infarction such as V1, V2, V6 and I were correlated with the extent of QRS-wave changes in V1 and V6.

RESULTS

ST-segment elevation in V6 showed correlations with R/S ratio in V1 (r=0.802, B=0.440, P=<0.001) and with the depth of Q-waves in V6 (r=0.671, B=0.441, P=0.007). This correlation was higher in a small subgroup where the left circumflex branch (Cx) was the culprit vessel (r=0.888, B=1.469 and P=0.018). ST-segment depression in lead I correlated with the height of R and the surface of R in V1 (height times width of R) (r=0.542, B=-0.150, P=0.005 and r=0.538, B=-0.153, P=0.005 respectively), especially in the subgroup without proximal occlusions of RCA (r=0.711 and r=0.699). ST-segment depression in lead I also predicted Q-waves in V6 (r=0.538, B=0.114, P=0.006). ST-segment changes in V2 showed no significant correlation with either R- or Q-wave measurements.

CONCLUSIONS

ST-segment elevation in V6 in the acute phase of non-anterior MI predicts lateral involvement as expressed by the R/S ratio in V1 in the post reperfusion phase. A subgroup with Cx occlusion showed especially strong correlations, although the size of the group was small. In lead I ST-segment depression is correlated to height and surface of R in V1 and Q-waves in V6.

Assessment of the ST segment deviation area as a potential physiological marker of the acute myocardial infarction

The purpose of this article is to present the assessment of the ST segment deviation area as a feature estimated from electrocardiographic signals to improve the current quantitative measures, which have low correlation with standard measures, such as biomarkers. In total 20 subjects were involved in the study. They were classified into two distinct groups (anterior and inferior) related to the localization of the acute myocardial infarction (AMI). The area of the ST segment was calculated by using customized software developed in Matlab®. From the analysis of this parameter it may be possible to correlate the ST deviation area with the necrosis risk area on myocardial tissue. The correlation between the ST area estimates were compared with Aldrich score, which uses the height of the J point instead of the area. It was calculated the correlation between the ST area, the Aldrich score and biomarkers of myocardial injury in patients. A Spearman correlation coefficient of 0.58 was estimated when comparing Aldrich score and the biomarkers for inferior AMI. The coefficient was 0.99 when correlating the biomarkers to the ST area. Therefore, this feature is a potential physiological marker of inferior AMI. The possibility of estimating the necrosis extent by means of electrocardiographic analysis allows for the reduction of cost and time since there may be no requirement for additional laboratorial exams, consequently improving the treatment efficacy and the prognosis of patients affected by acute myocardial infarction.

Automated discrimination of proximal right coronary artery occlusion from middle-to-distal right coronary artery occlusion and left circumflex occlusion in ST-elevation myocardial infarction

BACKGROUND

Classifying the location of an occlusion in the culprit artery during ST-elevation myocardial infarction (STEMI) is important for risk stratification to optimize treatment. We developed a new logistic regression (LR) algorithm for 3-group classification of occlusion location as proximal right coronary artery (RCA), middle-to-distal RCA or left circumflex (LCx) coronary artery with inferior myocardial infarction. We compared the performance of the new LR algorithm with the recently introduced decision tree classifier of Fiol et al (Ann Noninvasive Electrocardiol. 2004;4:383-388) in the classification of the same 3 categories.

METHODS

The new algorithm was developed on a set of electrocardiograms from an emergency department setting (n = 64) and tested on a different set from a prehospital setting (n = 68). All patients met the current STEMI criteria with angiographic confirmation of culprit artery and occlusion location. Using LR, 4 ST-segment deviation features were chosen by forward stepwise selection. Final LR coefficients were obtained by averaging more than 200 bootstrap iterations on the training set. In addition, a separate 4-feature classifier was designed adding ST features of V4R and V8, only available in the training set.

RESULTS

The LR algorithm classified proximal RCA occlusion vs combined LCx occlusion and middle-to-distal RCA occlusion, with a sensitivity of 76% and specificity of 81% as compared with 71% and 62% for the Fiol classifier. The difference in specificity was statistically significant. The LR classifier trained with additional ST features of V4R and V8, but still limited to 4, improved the overall agreement in the training set from 65% to 70%.

CONCLUSION

Discrimination of proximal RCA lesion location from LCx or middle-to-distal RCA using the new LR classifier shows improvement over decision tree–type classification criteria. Automated identification of proximal RCA occlusion could speed up the risk stratification of patients with STEMI. The addition of leads V4R and V8 should further improve the automated classification of the occlusion site in RCA and LCx.