Delineation of QRS offset by instantaneous changes in ECG vector angle can improve detection of acute inferior myocardial infarctions

- We developed a new method for QRS offset location based on angular velocity (AV) changes around the QRS loop.
- The method was reliable and reproducible in healthy individuals.
- QRS offset point preceded the J point by > 10 ms in 32% of patients with inferior AMI, but in only 4.6% of apparently healthy individuals.
- QRS offset point precedence (ΔAV) coincided with diagnostic ST elevation in only a minority of patients with recent inferior AMI.
- The use of ΔAV precedence as a complement to conventional determination of ST elevation increased the sensitivity for detecting inferior AMIs from 23 to 42%.

We developed an automated new method for determining QRS offset, based on angular velocity (AV) changes around the QRS loop, and compared the method's performance to that of manual and more established automated methods for determining QRS offset in both healthy subjects and patients with acute myocardial infarction (AMI). Specifically, using Frank leads reconstructed from standard 12-lead ECGs, we determined AV in the direction of change raised to the 4th power, d(t). We found that the d(t)-determined AV transition (ΔAV) nearly coincided with manually determined QRS offset in healthy subjects, and in 27 patients with anterior AMI. However, in 31 patients with inferior AMI, ΔAV typically preceded that of QRS offset determined by the established automated methods, and by more than 10 ms in 32% of cases. While this “ΔAV precedence” coincided with diagnostic ST elevation in only a minority of patients with recent inferior AMI, the use of ΔAV precedence as a complement to traditional determination of ST elevation increased the sensitivity for detecting inferior AMIs from 23 to 42%.

125