Consideration of QRS complex in addition to ST segment abnormalities in the estimation of the 'risk region' during acute inferior myocardial infarction

Background: The myocardial area at risk (MaR) has been estimated in patients with acute myocardial infarction (AMI) by using ST segment based ECG methods. However, as the process from ischemia to infarction progresses, the ST segment deviation is typically replaced by QRS abnormalities, causing a falsely low estimation of the total MaR if determined by using ST segment based methods. A previous study showed the value of the consideration of the abnormalities in the QRS complex, in addition to those in the ST segment estimating the total MaR for patients with anterior AMI. The purpose of this study was to investigate the same method for patients with inferior AMI.

Methods: Thirty-two patients with acute inferior ST elevation myocardial infarction received (99m)Tc-Sestamibi before percutaneous coronary intervention. SPECT was performed within 2 hours after treatment and was used as a gold standard for the estimation of the total MaR. The ECG recorded at admission in the hospital was used for the ECG estimates of the total MaR. This included a ST segment estimation of the ischemic component of the total MaR (Aldrich score) and an estimation of the infarcted component of the total MaR in the acute phase of AMI by QRS abnormalities (Selvester score). These scores were added for the combined ECG score.

Results: The ischemic component of the total MaR estimated by the Aldrich score alone no statistically significant correlation with SPECT (r=0.17, p=0.36). The infarcted component of the total MaR estimated by the Selvester score showed a significant correlation with SPECT (r=0.55, p=0.001). When the Aldrich and Selvester scores were combined, the correlation with SPECT improved (r=0.58, p<0.001). Both the Aldrich and Selvester score alone underestimated the mean MaR measured by SPECT (respectively p=0.007 and p<0.0001). There was no statistically significant difference between the mean MaR estimated by the sum of Aldrich and Selvester and the MaR measured by SPECT (p=0.636).

Conclusion: The estimation of the total MaR was more accurate by taking both ST deviation and QRS abnormalities in account than by using either method alone. A new ECG method to determine the total MaR during acute coronary occlusion should consider both its ischemic and infarcted components.