The increasing availability of wearable electrocardiography (ECG) devices enables the continuous monitoring of individual ECG alterations. This could be beneficial for patients suffering from acute ischemia but with non-standard ECG findings that do not fit to the subject-independent and absolute thresholds defined in clinical guidelines.
In this work, we evaluate the inter-patient magnitude of individual ECG alterations during ischemia. The freely available STAFF III database provides 12-lead ECG recordings of patients before, during, and after elective percutaneous coronary intervention (PCI), where a coronary vessel is widened with a balloon inflation. We compute individual alterations of ST-interval and T-wave amplitudes w.r.t. QRS amplitude over time for each patient and lead. We demonstrate that determining relative ST-interval/T-wave amplitudes and deriving individual alterations over time is feasible in standard and non-standard ECG recordings.
To demonstrate clinical relevance, we use the features for differentiating N=54 STAFF III patients with atherosclerotic plaque in either the right coronary artery (RCA) or left ascending artery (LAD). Results show significant differences in 5 leads for ST-interval alterations and 3 leads for T-wave alterations, which are also suggested by clinical guidelines for ischemia detection. Furthermore, state-of-the-art ECG assessment is performed in the classic 10 seconds snapshot interval of a 12 lead-ECG recording. Our additional time information could possibly reveal a characteristic dynamic in ischemic ECG recorded over a period of time in serial ECGs. Our results indicate that this novel feature could further contribute to individual diagnosis of ischemic states.
Clinical relevance— 40% of patients who suffer a myocardial infarction can currently not be diagnosed using existing guidelines. Assessing individual alterations w.r.t. QRS amplitude and extracting features over time in serial recordings could eventually close the gap in ECG evaluation of patients presenting with pre-existing heart conditions and non-standard ECGs.