Detection and quantification of acute myocardial ischemia by morphologic evaluation of QRS changes by an angle-based method

Objective: In acute myocardial ischemia changes within the QRS complex can add valuable information to that from the repolarization phase. This study evaluates three angles obtained from the main slopes of the R-wave within the QRS complex to assess acute myocardial ischemia. Methods: The QRS angles, denoted by OR (R-wave angle), OU (up-stroke angle) and OD (downstroke angle), were evaluated in 12-lead electrocardiogram (ECG) recordings of 79 patients before and during coronary occlusion by elective percutaneous coronary intervention (PCI). In a subset of 38 patients, ischemia was quantified by myocardial scintigraphy. Results: At baseline the QRS angles presented low variations. During occlusion, OU and OD developed a fast and abrupt change, whereas OR showed a smaller and gradual change. There were significant correlations between both maximal and sum of positive change in OR and ischemia: r = 0.67; p b 0.001 and r = 0.78; p b 0.001, for extent, and r = 0.60; p b 0.001 and r = 0.73; p b 0.001, for severity, respectively. Prediction of extent and severity of ischemia increased by 50% by adding OR changes to ST-segment changes, for LCX occlusions, whereas increased by 12.1% and 24.6% for LAD and RCA occlusions, respectively. No significant correlation was seen between OU and OD angles and ischemia. Conclusions: Evaluation of QRS angles from the standard 12-lead ECG represents a sensitive marker for detection of acute myocardial ischemia, whereas, OR changes can be used for prediction of its extent and severity.