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EXPEDITED PUBLICATION

Fundamental Differences in Electrophysiologic and Electroanatomic Substrate Between Ischemic Cardiomyopathy Patients With and Without Clinical Ventricular Tachycardia

Department of Cardiology, Royal Melbourne Hospital and the Department of Medicine, University of Melbourne, Melbourne, Australia

Manuscript received January 15, 2009; revised manuscript received March 30, 2009, accepted April 20, 2009.

^_* Reprint requests and correspondence: Prof. Jonathan M. Kalman, Department of Cardiology, Royal Melbourne Hospital, Grattan Street, Parkville, Victoria, Australia 3050 (Email: jon.kalman{at}mh.org.au).

Objectives: The aim of this study was to compare the electrophysiologic substrate in ischemic cardiomyopathy (ICM) patients with and without sustained monomorphic ventricular tachycardia (SMVT).

Background: Despite the universal presence of potentially arrhythmogenic left ventricular (LV) scarring, it is not clear why the majority of ICM patients never develop SMVT.

Methods: Detailed electroanatomic mapping of the LV endocardium was performed in 17 stable control ICM patients (16 males) without clinical SMVT. They were compared with 17 ICM patients (15 males) with spontaneous SMVT. Standard definitions of low-voltage zones and fractionated, isolated, and very late potentials were used.

Results: There were no significant baseline differences between the groups in terms of LV diameter, ejection fraction (27% vs. 28%), infarct territory, or time from infarction. However, control patients had smaller total low-voltage area 1.5 mv (30% of surface area vs. 55%, p < 0.001); smaller very low-voltage area <0.5 mv (7.3% vs. 29%, p < 0.001); higher mean voltage of low-voltage zones; fewer fractionated, isolated, and very late potentials with lower density of these scar-related electrograms per unit low-voltage area; and less SMVT inducibility. Potential conducting channels within dense scar and adjacent to the mitral annulus were more frequent in SMVT patients.

Conclusions: Compared with ICM patients with SMVT, an otherwise similar control group demonstrated markedly smaller endocardial low-voltage zones; lower scar-related electrogram density; and fewer conducting channels with faster conduction velocity. These findings may explain why some ICM patients develop SMVT and others do not.

Key Words: cardiomyopathy • tachycardia • myocardial infarction • electrophysiology

Abbreviations and Acronyms   EF = ejection fraction   ICD = implantable cardioverter-defibrillator   ICM = ischemic cardiomyopathy   ILZ = intermediate low-voltage zone   LV = left ventricle   MI = myocardial infarction   SMVT = sustained monomorphic ventricular tachycardia   TLZ = total low-voltage zone   VLZ = very low-voltage zone

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