Noninvasive ECG Imaging of Electrophysiologically Abnormal Substrates in Infarcted Hearts

Abstract

Background-Myocardial infarction and subsequent remodeling create substrates with altered electrophysiological (EP) properties that are highly arrhythmogenic. Existing ECG methods cannot always detect the existence of such substrates nor provide any detailed information about their EP characteristics. A noninvasive method with such capabilities is greatly needed for identifying patients at risk of arrhythmias and for guidance and evaluation of therapy. Recently, we developed a noninvasive ECG imaging modality that can reconstruct epicardial EP information from body surface potentials. We extended its application to hearts with structural disease and examined its ability to detect and characterize abnormal EP substrates. Methods and Results-Epicardial potentials were recorded with a 490-electrode sock from an open-chest dog. Recordings were obtained from a normal heart and from the same heart 2 hours after left anterior descending coronary artery occlusion and ethanol injection to create an infarct. Body surface potentials were generated from these epicardial potentials in a human torso model. Realistic geometry errors and measurement noise were added to the torso data, which were then used to noninvasively reconstruct epicardial potentials and electrograms (EGMs), with excellent accuracy. EP characteristics associated with the infarct substrate were reconstructed, including (1) a negative region over the infarct, (2) EGMs with large predominant negative deflections (eg, Q-wave EGMs), (3) Q-wave EGMs with superimposed RS deflections reflecting local activation of surviving myocardium within the infarct border zone, (4) reduced magnitudes of EGM negative derivatives, and (5) negative QRS integrals of EGMs over the infarct. Conclusions-ECG imaging can noninvasively detect and map abnormal EP substrates associated with infarction and structural heart disease. (Circulation. 2000;101:533-540.)

Imaging Dispersion of Myocardial Repolarization, II

“…We do so using noninvasive ECG imaging (ECGI) methods developed in our laboratory 8 -11 and recently applied to reconstruct activation during reentrant arrhythmias. 12,13 The results demonstrate the feasibility of the approach in terms of its ability to noninvasively detect and locate substrates with high dispersion of repolarization in the heart.…”

“…As in previous studies, [12][13][14] recorded potentials were placed on a digitized 3D canine heart model and aligned on the basis of the positions of coronary arteries. The heart was then placed in the correct anatomic position inside a computer model of the human torso that contained lungs, spine, sternum, and skeletal muscle.…”

Imaging Dispersion of Myocardial Repolarization, I

“…As in previous studies, 17,18 recorded epicardial potentials were placed on a digitized 3D canine heart model and aligned on the basis of the positions of the coronary arteries. The heart model was placed in its anatomic position within a computer model of a human torso with lungs, spine, sternum, and skeletal muscle.…”

“…Recent developments of a noninvasive imaging modality for cardiac electrophysiology (ECG imaging), 26 however, have demonstrated that epicardial potentials and electrograms can be reconstructed with good accuracy over the entire epicardial surface in normal hearts 19,26,27 and in the presence of arrhythmogenic substrates associated with myocardial infarction. 17,18 Application of ECG imaging during repolarization to noninvasively reconstruct epicardial potentials and associated measures of dispersion, such as ARI and epicardial QRST integral maps, could provide detailed information on repolarization abnormalities. Such information could then be used to noninvasively identify patients at risk for developing arrhythmias, obtain more specific diagnosis of repolarization disorders, and monitor the effects of therapies that modify repolarization (eg, antiarrhythmic agents with class III action).…”

Accuracy of Quadratic Versus Linear Interpolation in Noninvasive Electrocardiographic Imaging (ECGI)

“…ECGI was validated extensively in canine-heart experiments during normal sinus rhythm (SR), 17 ventricular pacing 18,19 and reentrant ventricular tachycardia (VT) in infarcted hearts. [4][5][6] It was also shown to image cardiac repolarization and its spatial dispersion. 16 Recently, ECGI was also applied in human subjects, demonstrating its ability to image normal activation and repolarization, locate initiation sites during right and left ventricular pacing, image the conduction abnormality associated with right bundle branch block (RBBB) and image the right-atrial reentry circuit during typical atrial flutter.…”