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All authors read and approved the final manuscript. His research interests include intelligent systems control, computational intelligence, robust control, and quality engineering. Yenming J. Chen received his Ph. We thank the anonymous reviewers and editors for their careful reading of our manuscript and their many insightful comments and suggestions.
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Reprints and Permissions. Tang, WH. Retrieving hidden atrial repolarization waves from standard surface ECGs. BioMed Eng OnLine 17, Download citation.
Published : 06 November Anyone you share the following link with will be able to read this content:. Sorry, a shareable link is not currently available for this article. Provided by the Springer Nature SharedIt content-sharing initiative. Skip to main content. Search all BMC articles Search. Download PDF. Volume 17 Supplement 2. Abstract Background This study estimates atrial repolarization activities Ta waves , which are typically hidden most of the time from body surface electrocardiography when diagnosing cardiovascular diseases.
Methods We obtain TMPs in the atrial part of the myocardium which reflects the correct excitation sequence starting from the atrium to the end of the apex.
Conclusions This extraction makes many diseases, such as acute atrial infarction or arrhythmia, become easily diagnosed. Background Atrial repolarization waves Ta waves are equally important as ventricular repolarization waves T waves and can exhibit significant potential as an effective biomarker for clinic diagnosis [ 1 , 2 ].
Methods As mentioned earlier, the extraction of P waves should be conducted at the electric current level in myocardial sources. Inverse problem We first consider the forward problem from equivalent current—dipole sources to body surface potentials. Geometries of heart and torso. Full size image. Discussions The error caused by spatial digitization may overwhelm other sources of error terms because of the resolution limitation in mesh grids.
Conclusions In this study, we consider only signals in the standard lead ECG measurement. References 1. In fact, the shape changes depending on which recording electrodes are being used. The shape also changes when there is abnormal conduction of electrical impulses within the ventricles.
The isoelectric period ST segment following the QRS and ending at the beginning of the T wave is the time at which both ventricles are completely depolarized. This segment roughly corresponds to the plateau phase of the ventricular action potentials.
The ST segment is very important in the diagnosis of ventricular ischemia or hypoxia because under those conditions, the ST segment can become either depressed or elevated. The T wave represents ventricular repolarization. Generally, the T wave exhibits a positive deflection. The reason for this is that the last cells to depolarize in the ventricles are the first to repolarize. This occurs because the last cells to depolarize are located in the subepicardial region of the ventricles and these cells have shorter action potentials than found in the subendocardial regions of the ventricular wall.
So, although the depolarization of the subepicardial cells occurs after the subendocardial cells, the subepicardial cells undergo phase 3 repolarization before the subendocardial cells. Therefore, repolarization waves generally are oriented opposite of depolarization waves green versus red arrows in figure , and repolarization waves moving away from a postive recording electrode produce a positive voltage.
The T wave is longer in duration than the QRS complex that represents depolarization. The longer duration occurs because conduction of the repolarization wave is slower than the wave of depolarization.
The reason for this is that the repolarization wave does not utilize the high-velocity bundle branch and purkinje system, and therefore primarily relies on cell-to-cell conduction.
Sometimes a small positive U wave may be seen following the T wave not shown in figure at top of page. This wave represents the last remnants of ventricular repolarization. Inverted T waves or prominent U waves indicates underlying pathology or conditions affecting repolarization. The second wave is the QRS complex. Typically this complex has a series of 3 deflections that reflect the current associated with right and left ventricular depolarization.
By convention the first deflection in the complex, if it is negative, is called a Q wave. The first positive deflection in the complex is called an R wave.
A negative deflection after an R wave is called an S wave. Some QRS complexes do not have all three deflections.
But irrespective of the number of waves present, they are all QRS complexes:. NB: The first wave of the last complex is a negative deflection. Therefore, it qualifies to be called a Q wave. Since all QRS complexes have an R wave, there must be one in this example as well, although it may be so small that it is not visible. A negative deflection following an R wave is an S wave.
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