title: Dispersion of ventricular repolarization in the long QT syndrome.
abstract: To identify markers of dispersion of the ventricular repolarization in the idiopathic long QT syndrome, body surface potential maps were analyzed in 40 such patients (mean age +/- standard deviation 21 +/- 11 years) and in 30 healthy control subjects (mean age 24 +/- 7 years). In each subject, 117 chest leads were recorded and maps of the integral values of the QRST interval were calculated. A multipolar distribution of the values, a marker of gross electrical inequalities of repolarization, was found only in 4 patients. To detect minor regional disparities of ventricular recovery, all the ST-T waveforms were analyzed in each subject. The ST-T waves were represented by a discrete series of potential values. The "similarity index" was computed by applying a principal component analysis, which represents (in percent) to what extent 1 fundamental pattern of ST-T reproduces all the recorded waveforms. The mean value of the similarity index was significantly lower in patients with long QT syndrome than in control subjects (49 +/- 10 vs 77 +/- 8%, p less than 0.0001). A value less than 61% (corresponding to 2 standard deviations below the mean value for controls) was found in 35 of 40 patients and in only 1 control subject (sensitivity 87%, specificity 96%). Thus, the similarity index is a more sensitive marker than the multipolar distribution of QRST integral maps in revealing electrical disparities of the ventricular recovery times.(ABSTRACT TRUNCATED AT 250 WORDS)
authors.affiliation: Division of Cardiology, Istituto di Scienze Medico-Chirurgiche San Donato, Italy.
authors.forename: L
authors.initials: L
authors.lastname: De Ambroggi
authors.forename: M S
authors.initials: MS
authors.lastname: Negroni
authors.forename: E
authors.initials: E
authors.lastname: Monza
authors.forename: T
authors.initials: T
authors.lastname: Bertoni
authors.forename: P J
authors.initials: PJ
authors.lastname: Schwartz
mesh_terms: D000200:Action Potentials / Q000502:physiology; D000293:Adolescent; D000328:Adult; D002648:Child; D004562:Electrocardiography / Q000295:instrumentation / Q000379:methods; D004566:Electrodes; D005260:Female; D006801:Humans; D008133:Long QT Syndrome / Q000503:physiopathology*; D008297:Male; D008875:Middle Aged; D012680:Sensitivity and Specificity; D013909:Thorax; D013997:Time Factors; D016276:Ventricular Function / Q000502:physiology*