Fundamental Differences in Electrophysiologic and Electroanatomic Substrate Between Ischemic Cardiomyopathy Patients With and Without Clinical Ventricular Tachycardia
Haris M. Haqqani, MBBS,
Jonathan M. Kalman, MBBS, PhD*,
Kurt C. Roberts-Thomson, MBBS, PhD,
Richard N. Balasubramaniam, MB, ChB, PhD,
Raphael Rosso, MD,
Richard L. Snowdon, MBBS, MD,
Paul B. Sparks, MBBS, PhD,
Jitendra K. Vohra, MD and
Joseph B. Morton, MBBS, PhD
Department of Cardiology, Royal Melbourne Hospital and the Department of Medicine, University of Melbourne, Melbourne, Australia
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Figure 1 Electroanatomic Mapping Data
(A) shows an example of typical isopotential maps seen in both groups. Bipolar voltages <0.5 mV (VLZ) are depicted in red, with normal myocardium (>1.5 mV) represented by purple. The map on the left is from a 58-year-old man with severe ICM (EF 18%) after a large anterior MI 9 years earlier with no clinical arrhythmias. The VLZ accounts for only 9% of the LV surface area. A 67-year-old man with similarly severe ICM and spontaneous SMVT 13 years after anterior MI is shown on the right. A large confluent anteroapical VLZ accounting for 44% of the LV surface is present. The mean proportionate low-voltage areas are shown in B, with markedly larger VLZ and TLZ in Group 2. The mean signal amplitudes in these regions were significantly higher in the control patients (C). EF = ejection fraction; ICM = ischemic cardiomyopathy; LAO = left anterior oblique; LV = left ventricular; MI = myocardial infarction; SMVT = sustained monomorphic ventricular tachycardia; TLZ = total low-voltage zone; VLZ = very low-voltage zone.
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Figure 2 Electrogram Prevalence and Density
The right anterior oblique projections of the 2 patients from Figure 1 are shown in A with scar-related electrograms annotated as follows: fractionated potentials (FP) in light blue, isolated potentials (IP) in white, and very late potentials (VLP) in gray. In the SMVT patient at the bottom of the panel, FPs were found around the VLZ border; IP and VLP were found deeper inside the VLZ. In the control patient, there is an extreme paucity of scar-related electrograms despite high-density point sampling in the smaller low-voltage zone. The global prevalence of scar-related electrograms was significantly greater in the SMVT group as shown in B. Fundamental differences in the composition and potential arrhythmogenicity of the abnormal substrate are suggested by the data in C, where Group 2 has a higher density of FP and VLP per unit low-voltage zone area. Abbreviations as in Figure 1.
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Figure 3 Putative Conducting Channels
An example of isopotential adjustment to show potential channels of higher regional voltage within the VLZ is shown in A in a 63-year-old woman with EF of 27% 8 years after inferior MI, and frequent SMVT. B shows a large area of confluent dense lateral scarring in a 67-year-old man with earlier inferolateral infarction, EF of 24%, and recurrent SMVT requiring ICD therapy. The left side shows an area of lateral very low voltage in the left anterior oblique projection. The right side displays a zone of voltage preservation adjacent to the mitral annulus. The marker tags represent points where VLPs were seen. One of the induced SMVTs in this patient exited from the superior mitral isthmus and was ablated here. All these channel types were less common in the control patients without SMVT. ICD = implantable cardioverter-defibrillator; VLP = very late potential; other abbreviations as in Figure 1.
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