Imaging Dispersion of Myocardial Repolarization, I

Burnes, John E.; Ghanem, Raja N.; Waldo, Albert L.; Rudy, Yoram

doi:10.1161/hc3601.094276

Cited by 49 publications

(25 citation statements)

References 39 publications

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“…Abnormally high dispersion can be associated with genetic disorders, such as the long-QT syndrome, 2,17,18 or with substrate remodeling, such as occurs during infarction 1 or cardiomyopathies. 19 The companion article 7 established the principle that dispersion of repolarization is faithfully reflected in epicardial electrophysiological measures but not in noninvasive ECG measures on the body surface (eg, QT dispersion). Here, we evaluate the ability to noninvasively reconstruct epicardial regions with increased dispersion and to obtain a measure of its severity.…”

Section: Discussionmentioning

confidence: 99%

“…Details of the experimental procedure are presented in the companion article. 7 Briefly, localized epicardial warming to 42°C and cooling to 28°C were used to induce regions of shortened and prolonged repolarization, respectively. Four different protocols were studied during right atrial pacing: control, localized left ventricular (LV) warming, localized LV cooling, and adjacent LV warming and cooling.…”

Section: Experimental Methodsmentioning

confidence: 99%

“…Attempts to do so noninvasively with body-surface ECG indices (eg, QT dispersion 3 ) have met with only partial success and suffer from lack of consistency. 4 -6 As shown in the companion article, 7 the inconsistency results from a fundamental property of the spread of the cardiac electrical field within the torso. Such a spread does not preserve spatial relationships, and the potential measured at a given body-surface point (ECG electrode) reflects potentials over the entire heart.…”

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Imaging Dispersion of Myocardial Repolarization, II

et al. 2001

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Background-Dispersion of myocardial repolarization supports the development and maintenance of life-threatening arrhythmias. Current noninvasive approaches for detecting substrates with increased dispersion based on ECG measures (eg, QT dispersion) have shown limited success and inconsistencies. The companion article shows that, in contrast, epicardial potentials and derived measures reflect local dispersion of repolarization. Here, using a recently developed ECG imaging method, we evaluate the feasibility of noninvasive reconstruction of such epicardial measures from body-surface ECG data. Methods and Results-Epicardial potentials were recorded with a 224-electrode sock from an open-chest dog during control, regional warming, cooling, and simultaneous adjacent warming and cooling to induce localized changes in myocardial repolarization and regions of increased dispersion. Body-surface potentials were generated from these epicardial potentials in a human torso model. Realistic geometric errors and measurement noise were added to the torso data, which were then used to noninvasively reconstruct epicardial measures of repolarization dispersion (activation recovery intervals [ARIs] and QRST integrals). Repolarization properties were accurately depicted by ECG imaging, including (1) shortened ARIs and increased QRST integrals over the warmed region, (2) prolonged ARIs and decreased QRST integrals over the cooled region, and (3) high gradients of ARIs and QRST integrals over the adjacent warmed and cooled regions. Conclusions-ECG imaging can reconstruct repolarization properties accurately and localize areas of increased dispersion of repolarization in the heart noninvasively. Its clinical significance lies in the possibility of noninvasive risk stratification and in guidance and evaluation of therapy.

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Section: Discussionmentioning

confidence: 99%

Section: Experimental Methodsmentioning

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Imaging Dispersion of Myocardial Repolarization, II

et al. 2001

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“…TCRT values close to one indicate no orientation difference between the dipoles, values ϳ0 correspond to 90°differences and values close to Ϫ1 correspond to the very opposite direction. Negative values of TCRT are usually found in cardiac disease with nonlocalized pathologies, e.g., in hypertrophic cardiomyopathy and ischemic heart disease (1, 26, 46) when T waves are more likely to be inverted (6).…”

Section: Physiological and Technical Considerationsmentioning

confidence: 99%

Ventricular gradient and nondipolar repolarization components increase at higher heart rate

Smetana

Batchvarov

Hnatkova

et al. 2004

American Journal of Physiology-Heart and Circulatory Physiology

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.-Differences in action potential duration reflect differences in ion channel properties. These properties also determine rate dependence of action potential duration, and transmural dispersion was confirmed experimentally to increase with cycle length. While several electrocardiographic indexes characterizing repolarization abnormalities have been proposed, studies of their heart rate dependence are missing. This study therefore investigated rate relationship of two repolarization descriptors, namely, the so-called total cosine of the QRS-T angle (TCRT), proposed to characterize global repolarization heterogeneity, and the so-called relative T wave residuum (TWR), linked to regional repolarization dispersion. During 24-h holter recordings in 60 healthy subjects (27 males), a 12-lead ECG was obtained every 30 s. RR intervals, QT intervals, and TCRT and TWR were calculated in each ECG and averaged over RR interval bins ranging from 550 to 1,150 ms in 10-ms steps. Women had uniformly greater TCRT and TWR values than men did over the entire range of investigated RR intervals. Whereas the TCRT in both sexes showed marked rate dependence with higher values at long RR intervals (550 vs. 1,150 ms: women, 0.46 Ϯ 0.31 vs. 0.76 Ϯ 0.18, P ϭ 9 ϫ 10 Ϫ7 ; men, 0.08 Ϯ 0.45 vs. 0.49 Ϯ 0.35, P ϭ 9 ϫ 10 Ϫ8 ), the rate dependence of TWR was more marked in women than in men, showing higher values at shorter RR intervals (550 ms vs. 1,150 ms: women: 0.29 Ϯ 0.14% vs. 0.08 Ϯ 0.06%, P ϭ 2 ϫ 10 Ϫ8 ; men: 0.14 Ϯ 0.12% vs. 0.04 Ϯ 0.02%, P ϭ 2 ϫ 10 Ϫ15 ). This suggests that both global and regional repolarization heterogeneity are increased at faster heart rates. Whereas in women at all heart rates the sequence of repolarization more closely replicates the sequence of depolarization, localized repolarization is more heterogeneous than in men especially at fast heart rates. repolarization heterogeneity; electrocardiogram; rate dependence; gender difference ACTION POTENTIAL DURATION (APD) differs not only between myocytes of different ventricular layers (35) but also between the cardiac apex and base (25), posterior and anterior endocardial surfaces (4), and right and left ventricle (8). This APD dispersion is potentially arrhytmogenic, especially when increased by ion channel mutations in congenital and druginduced long QT syndrome (3) or by abrupt changes in cycle length (17).Differences in APD reflect differences in ion channel properties (13,35). Because these properties also determine the rate dependence of APD (13,35,42), heart rate likely influences APD dispersion across the heart. However, experimental studies confirmed significant increase with cycle length prolongation for transmural dispersion (35) that was linked to the occurrence of torsades de pointes and QT interval prolongation at slow heart rates (3). Electrocardiographic investigations of heart rate dependence of other facets of repolarization heterogeneity are missing.Several electrocardiographic indexes have recently been proposed to characterize repolarization abnormalit...

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“…QT dispersion has been used to characterize myocardial repolarization, but recent studies showed that QT dispersion is unrelated, 28,29 so further study will be required to identify the clinical importance and electrophysiological role of QT dispersion.…”

Section: Discussionmentioning

confidence: 99%

Opening of KATP Channel Attenuates the Increase in QT Dispersion Produced by the First Balloon Inflation During Coronary Angioplasty.

Ashikaga

Nishizaki

Arita

et al. 2002

Circ J

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ethal ventricular arrhythmias, which occur more frequently at the first balloon inflation than with subsequent procedures, occur in 1.5-4.4% of patients undergoing percutaneous transluminal coronary angioplasty (PTCA). [1][2][3][4][5][6] Moreover, these arrhythmias develop more often with PTCA of the left anterior descending coronary artery (LAD). 6 Increased QT dispersion is an useful marker of lethal ventricular arrhythmias, 6 but the mechanism and prevention of the lethal ventricular arrhythmias complicating PTCA have not been elucidated.A previous study reported that repeated coronary occlusions during PTCA reduces the occurrence of ventricular arrhythmias, 7 and these phenomenon have been attributed to ischemic preconditioning through the opening of the KATP channel. Tomai et al demonstrated that ischemic preconditioning during PTCA was prevented by glibenclamide, a selective KATP channel blocker, 8 and Garrat et al demonstrated an increased mortality rate in diabetic patients given sulfonylurea during PTCA. 9 Cole et al demonstrated in guinea pigs that blockade of the KATP channel with glibenclamide worsened the electrical and mechanical

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Imaging Dispersion of Myocardial Repolarization, I

Cited by 49 publications

References 39 publications

Imaging Dispersion of Myocardial Repolarization, II

Imaging Dispersion of Myocardial Repolarization, II

Ventricular gradient and nondipolar repolarization components increase at higher heart rate

Opening of KATP Channel Attenuates the Increase in QT Dispersion Produced by the First Balloon Inflation During Coronary Angioplasty.

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