title: Microvolt T wave alternans in human cardiac hypertrophy: electrical instability and abnormal myocardial arrangement.
abstract: BACKGROUND
  Although T wave alternans (TWA) is a promising risk marker for myocardial electrical instability, it remains unclear how the presence of TWA is related to myocardial damage.
  
  
  RESULTS
  TWA was measured in 28 patients with hypertrophic cardiomyopathy (HCM), 29 patients with hypertensive left ventricular hypertrophy (HLVH), and 15 normal volunteers using a CH2000 system. The amplitude of TWA (Valt) was measured at the lead with the maximum amplitude. Cardiac biopsy was performed in 12 HCM patients, who were divided into two groups (severe and mild) based on histologic findings of myocardial disarray and fibrosis. TWA was positive (Valt > 1.9 microV) in 61% of HCM and 31% of HLVH, despite a nearly identical left ventricular mass index (176 +/- 65 g/m2 vs 175 +/- 39 g/m2). Valt at heart rate = 110 beats/min was significantly greater in HCM with severe disarray and fibrosis than in HCM with mild disarray and in HLVH.
  
  
  CONCLUSIONS
  In HCM patients, a positive TWA test probably is related to abnormal myocardial arrangement (disarray) and/or fibrosis, and it may reflect electrical instability of the myocardium.
authors.affiliation: Division of Cardiovascular Medicine, Tohoku University Hospital, Sendai, Japan.
authors.forename: Y
authors.initials: Y
authors.lastname: Kon-No
authors.forename: J
authors.initials: J
authors.lastname: Watanabe
authors.forename: Y
authors.initials: Y
authors.lastname: Koseki
authors.forename: J
authors.initials: J
authors.lastname: Koyama
authors.forename: A
authors.initials: A
authors.lastname: Yamada
authors.forename: S
authors.initials: S
authors.lastname: Toda
authors.forename: T
authors.initials: T
authors.lastname: Shinozaki
authors.forename: M
authors.initials: M
authors.lastname: Fukuchi
authors.forename: M
authors.initials: M
authors.lastname: Miura
authors.forename: Y
authors.initials: Y
authors.lastname: Kagaya
authors.forename: K
authors.initials: K
authors.lastname: Shirato
mesh_terms: D000368:Aged; D006332:Cardiomegaly / Q000473:pathology* / Q000503:physiopathology*; D004562:Electrocardiography; D015716:Electrocardiography, Ambulatory; D004594:Electrophysiology; D005080:Exercise Test; D005260:Female; D005355:Fibrosis; D006339:Heart Rate; D006801:Humans; D006973:Hypertension / Q000150:complications; D017379:Hypertrophy, Left Ventricular / Q000209:etiology / Q000503:physiopathology; D008297:Male; D008875:Middle Aged; D009206:Myocardium / Q000473:pathology*; D012016:Reference Values