The Initial Electrocardiographic Pattern in Acute Myocardial Infarction

Clinical and electrocardiographic variables associated with increased risk of ventricular septal defect in acute anterior myocardial infarction

It is unknown whether the risk factors associated with the development of ventricular septal defect (VSD) after acute myocardial infarction (MI) remain the same when thrombolytic therapy is used, nor have specific electrocardiographic patterns of acute MI associated with the development of VSD been identified. Our study population included patients with an anterior MI enrolled in the GUSTO-I study. Baseline clinical data were collected prospectively for all patients. Patients in whom VSD was suspected by the local investigators at each site were evaluated retrospectively. Baseline clinical and electrocardiographic variables were compared between 2 groups: 10,847 patients without VSD (99.6%) and 48 patients with confirmed VSD (0.4%). Multivariate analysis showed the following clinical variables to be independent predictors of VSD: age (odds ratio [OR] 2.19, 95% confidence intervals [CI] 1.62 to 2.98; p <0.001), female gender (OR 5.07, 95% CI 2.70 to 9.98; p <0.001), and lack of previous angina (OR 2.11, 95% CI 1.12 to 4.29; p = 0.021). Two electrocardiographic variables predicted acute VSD: the magnitude of ST deviation in lead III (OR 1.55, 95% CI 1.12 to 2.21; p = 0.007) and in lead V(2) (p <0.001). However, the relation between the ST amplitude in lead V(2) and the risk for VSD was nonlinear. In patients with anterior MI who underwent thrombolysis, the risk factors for VSD were age, female gender, and lack of previous angina. Previous infarction was not a risk factor. Less ST-segment depression in lead III was a predictor of VSD.

Automatic detection of ST-T complex changes on the ECG using filtered RMS difference series: application to ambulatory ischemia monitoring

A new detector is presented which finds changes in the repolarization phase (ST-T complex) of the cardiac cycle. It operates by applying a detection algorithm to the filtered root mean square (rms) series of differences between the beat segment (ST segment or ST-T complex) and an average pattern segment. The detector has been validated using the European ST-T database, which contains ST-T complex episodes manually annotated by cardiologists, resulting in sensitivity/positive predictivity of 85/86%, and 85/76%, for ST segment deviations and ST-T complex changes, respectively. The proposed detector has a performance similar to those which have a more complicated structure. The detector has the advantage of finding both ST segment deviations and entire ST-T complex changes thereby providing a wider characterization of the potential ischemic events. A post-processing stage, based on a cross-correlation analysis for the episodes in the rms series, is presented. With this stage subclinical events with repetitive pattern were found in around 20% of the recordings and improved the performance to 90/85%, and 89/76%, for ST segment and ST-T complex changes, respectively.

Temporal evolution of traditional versus transformed ECG-based indexes in patients with induced myocardial ischemia

The time course of changes in the electrocardiogram as a result of myocardial ischemia induced during prolonged coronary angioplasty has been studied. We have analyzed the electrocardiogram evolution during the occlusion in terms of the Ischemic Changes Sensor, which is a parameter that describes the capacity of different indexes to detect induced changes. Traditional indexes at specific time locations (ST level, T wave amplitude and position, and durations of QT interval and QRS complex) and global indexes (based on the Karhunen-Loève transform as applied to the QRS complex, ST-T complex, ST segment and T wave) have been considered. The global indexes better detected ischemic changes than the traditional indexes. The most sensitive were the index for the ST-T complex (89%) in the Karhunen-Loève transform-derived group and for the ST level (61%) in the traditional group. Changes in the ventricular repolarization period usually appeared earlier (77% of patients) than changes in the depolarization period (23% of patients). A similar percentage of patients exhibited the earliest ischemic changes in the T wave (41%) and in the ST segment (36%). The evolution of the Ischemic Changes Sensor parameters showed that the majority (60%) of the total changes occurred during the first minute of occlusion. The results suggest that the use of global electrocardiogram indexes better reflect ischemic changes than do traditional indexes, such as the ST segment deviation.

Identification of the occluded artery in patients with myocardial ischemia induced by prolonged percutaneous transluminal coronary angioplasty using traditional vs transformed ECG-based indexes

We have studied the spatial properties of ischemic changes as induced by prolonged angioplasty and how the changes are related to different ECG indexes. Indexes based on measurements at specific points in time (ST level at J + 60 ms point, maximal T wave amplitude and position, QT interval, and QRS duration) and global indexes (based on the Karhunen-Loève transform and applied to the QRS complex, ST-T complex, ST segment, and T wave), considering both repolarization and depolarization information, were analyzed. The changes during the occlusion period of the different indexes were used as variables in a multivariate discriminant analysis to determine which indexes showed the best discrimination of the three major occlusion sites (corresponding to LAD, RCA, and LCX coronary arteries). Occlusions in LCX artery were the most difficult to classify. With three local indexes (ST60 level measured in lead V3, T wave amplitude in I, and ST60 in III) it was possible to correctly classify 76% of patients by the occlusion site, and with three KLT-derived indexes (first-order KLT index for ST-T complex in I and for QRS in leads V3 and I) 83% of correct classification was obtained. Using six indexes for local and KLT-derived indexes the correct classification was increased to 85 and 90% of patients, respectively. The use of different ECG indexes (from different intervals) on quasiorthogonal leads permitted the identification of the occluded artery in patients undergoing PTCA and may be extended to more general use.