Diagnosing transient regional myocardial ischaemia (TRMI) in patients presenting to the Emergency Department (ED) with acute chest pain is a challenge. The 12 lead ECG has established limitations and Troponin, though sensitive, is less reliable when used within 12 hours of symptom onset. The PRIME ECG Delta map is derived from 80 electrode electrocardiographic surface maps acquired (a) during chest pain and (b) when pain resolves. ST segment differences between scans are then displayed as colour changes on a torso map. In addition, the Ischaemic Burden (IB) - an index of the total extent of myocardial ischaemia -may be derived from the Delta Map.
Objectives: In a cohort presenting with cardiac-sounding chest pain: 1.To compare the sensitivity and specificity of the PRIME Delta map and the 12 lead ECG for the diagnosis of TRMI using coronary angiography as a diagnostic gold standard. 2. To evaluate whether the IB is a valuable diagnostic tool and examine its relationship with Troponin.
Methods: 80 lead ECGs were acquired for subjects with suspected TRMI when in pain and once pain free and a Delta Map derived. The IB was calculated as the sum of ST segment shift across all 80 electrodes. Subjects then underwent coronary angiography as clinically appropriate.
Results: For 51 adults studied, the PRIME Delta Map was more sensitive for the detection of TRMI than the 12 lead ECG 93% vs. 81%, p 0.04. The Delta map was also more specific for TRMI 57% vs. 29%, p= 0.03.The Delta map was superior to the 12 lead particularly for detecting lateral and posterior regions of TRMI 100 % detection vs. 75%, p= 0.02. The IB correlated with peak Troponin (r= 0.52, p= 0.0001) and was significantly higher in patients with STEMI compared to NSTEMI. ROC curve evaluation of the IB showed it was an accurate measure of myocardial ischaemia with Area Under the Curve of 0.6 (95% CI 0.38 – 0.84)
Conclusion: The PRIME ECG Delta map is a near patient, rapid, accurate and intuitive method for detecting TRMI and is superior to the 12 lead ECG. The IB derived from the Delta map might be a useful early surrogate for Troponin in patients with suspected TRMI. Used together, the Delta Map and IB could potentially facilitate more rapid identification and appropriate treatment in patients with coronary artery disease.
Myocardial ischaemia in patients with coronary endothelial dysfunction: insights from body surface ECG mapping and implications for invasive evaluation of chronic chest pain
