A study of Laplacian surface maps from moments of activation to detect cardiovascular disease

Date of Award




Degree Name

Doctor of Philosophy (Ph.D.)


Biomedical Engineering

First Committee Member

Peter P. Tarjan, Committee Chair


The main objective of this research was to construct isochronal contour maps of activation from directly obtained multichannel surface Laplacian electrograms from human subjects. The Laplacian is the second spatial derivative of the ECG. The contour maps are based on the Moment of Activation (MOA), the instant the dipole that represents the depolarization wavefront crosses the vector normal to the active sensor's surface of the heart at specific sites near the sensor. Detection of the MOA is not a trivial task, especially in the presence of noise and from sites relatively distant from the heart.Four types of MOA detection techniques were evaluated: (1) The simple delay from the peak of Lead II QRS (L2R) to the LECG peak (MOA1); (2) Cross-correlation of the L2 and LECG (MOA2); (3) Cross correlation of the L2 ECG derivative and the LECG (MOA3); and (4) The delay from the L2R to the steepest zero crossing of the LECG (MOA4).Five types of filtering techniques to improve the signal to noise ratio (SNR) were tested: (1) Butterworth Bandpass; (2) Wiener Class III; (3) Alternative Wiener Class III; (4) Ensemble Averaging; (5) Artifact Rejection.Contour maps of isochrones (equal MOA time contour lines) were constructed both for single and the average heartbeat, using interpolation, to obtain maps that may be utilized in cardiac diagnosis. Isochronal maps were also generated for atrial flutter activity. Subjects with congestive heart failure who were treated with biventricular pacing were mapped with and without pacing. During pacing two early activation regions are present as expected due to two pacing locations. Atrial activity was detected and it correlated with the calculated output of an atrial activity computer simulation. Further studies must be conducted to determine the diagnostic potential of such patterns based on a larger number of subjects and with a greater number of simultaneous LECG recordings.


Engineering, Biomedical; Health Sciences, Medicine and Surgery

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