Conference Paper

A vectorial approach for evaluation of depolarization changes during acute myocardial ischemia

Commun. Technol. Group, Univ. of Zaragoza, Zaragoza, Spain
Conference: Computing in Cardiology, 2010
Source: IEEE Xplore

ABSTRACT In the present study we evaluated the upslope (IUS), downslope (IDS) and terminal slope (ITS) of the QRS complex in both standard and derived ECG leads obtained from spatial QRS loops, either by the vectorcardiogram (VCG) or by principal component analysis (PCA), in 79 patients undergoing prolonged, elective percutaneous coronary intervention (PCI). For each patient, the slope indices IUS, IDS and ITS were evaluated in the PCI recording as well as in a control recording acquired before the PCI procedure, and relative factors of change during PCI were calculated. We showed that IUS and IDS computed over VCG and PCA leads present higher sensitivity to the ischemia-induced changes than the same indices evaluated over the standard 12-lead ECG. Mean relative factors of change were 10.5 and 12.4 for IUS and IDS in PCA, and 7.87 and 13.7, respectively, in VCG, representing an increase in sensitivity of up to 103% for IUS and 46% for IDS compared to measurements obtained in lead V3. We conclude that evaluation of slope indices in leads derived from QRS loops significantly increases their potential value for detection of acute myocardial ischemia.

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    ABSTRACT: In clinical practice ST elevation is used in the ECG to detect myocardial infarction. Additional information from the depolarization phase (QRS complex) can improve diagnosis and risk stratification of the patient. In this paper we present a study of the upward (IUS\mathcal{I}_{\rm US}) and downward (IDS\mathcal{I}_{\rm DS}) slopes of the QRS complex as an alternative for detecting and quantifying ischemia induced depolarization changes. From ECG recordings both in a resting state (control recordings) and during PCI-induced transmural ischemia, we develop a method for quantification of IUS\mathcal{I}_{\rm US} and IDS\mathcal{I}_{\rm DS} that incorporates dynamic ECG normalization so as to improve sensitivity in the detection of ischemia induced changes. We show that IUS\mathcal{I}_{\rm US} and IDS\mathcal{I}_{\rm DS} present high stability at resting state, thus providing a stable reference for ischemia characterization. In PCI recordings we show that IUS\mathcal{I}_{\rm US} and IDS\mathcal{I}_{\rm DS} present maximum relative factors of change of 6.01 and 9.31, respectively, with respect to their own variability at control. We also show that the timing for the occurrence of significant changes in IUS\mathcal{I}_{\rm US} and IDS\mathcal{I}_{\rm DS} varies with lead, ranging from 30 s to 2 min after initiation of coronary occlusion. We conclude that QRS slopes offer a robust tool for evaluating depolarization changes during myocardial ischemia.
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    ABSTRACT: In this work we studied dynamic changes of ventricular depolarization loop evolution based on the Singular Value Decomposition (SVD) technique of 80 patients that underwent Percutaneous Transluminal Coronary Angioplasty (PTCA). The 8 independent ECG leads are subjected to SVD technique and are used to construct a new representation of QRS-SVD loops. In order to analyze the variations of QRS-SVD loops before, during and after PTCA, we proposed the following parameters: Maximum Module of the Depolarization Vector, Planar Area, Maximum Distance between Centroid and the Loop, Angle between the S1S2 plane and the Optimum Plane and Ratio between the Area and Perimeter. The results indicated that the parameters proposed show significant statistics differences during and after PTCA procedure vs. control. We concluded that the variations in the QRS-SVD loop before, during and after PTCA at ventricular depolarization can be described correctly through the proposed parameters.
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    ABSTRACT: 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.
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