ST depression in lead V,_4 can also be a manifestation of a posterior AMI. As reported by Boden et al, in 40 percent of patients with ischemic chest pain, ST segment depression in lead is due to posterior AMI. This localization of AMI should be suspected if the ST segment depression is horizontal and the T waves are positive. Occasionally, however, the T waves can be biphasic or negative. Patients with posterior MI have a higher CK-MB enzymes than those with anterior NQMI.
T Wave Inversion: The third ECG manifestation of NQMI is T wave inversion. As in other NQMI, the ECG changes should persist for 24 to 48 hours and the diagnosis confirmed by non-ECG methods. According to Granborg et al, only 23 percent of patients with ischemic chest pain and isolated T wave inversion develop AMI. buy diabetes drugs
What is the clinical significance of various ECG patterns in AMI? First, there are important differences between NQMI and QMI. In general, patients with NQMI are usually older, have a higher incidence of previous myocardial infarction, and history of congestive heart failure, as well as having more residual ischemia, lower inhospital mortality, smaller infarct size, and similar or even worse long-term prognosis.