Showing papers by "Arthur J. Moss published in 1989"

Electrocardiographic quantitation of ventricular repolarization.

Abstract: Quantification of the electrocardiographic ventricular repolarization involving the T-U wave complex is usually performed with reference to the axis of the T wave and the QT interval duration. A novel quantitative approach to improve the description of ventricular repolarization was applied to the digitized electrocardiograms of 423 normal subjects. Six electrocardiographic repolarization characteristics were identified: duration, rate, area, symmetry, late phenomena, and interlead heterogeneity. A computer algorithm was designed to automatically interpret the electrocardiographic repolarization segment and measure 11 variables that quantified these repolarization characteristics. The application of redundancy-reduction techniques selected a final set of seven variables that were used in the statistical analysis. The QT interval, which was included in the initial group of variables, was replaced by the time interval between S wave offset and T wave maximum. All selected electrocardiographic variables were independent of age (r2 less than 0.11) and body surface area (r2 less than 0.03); all except the early duration variable were heart rate- and QT interval-independent (r2 less than 0.2, r2 less than 0.13, respectively; and most were uncorrelated to each other. A comparison of repolarization characteristics by gender revealed that repolarization duration was significantly more prolonged (p less than 0.0001) in women than in men. This multidimensional quantitative approach conveys a new and more complete description of the repolarization process and provides an electrocardiographic repolarization database in normal subjects as a reference standard for identifying patients with disordered repolarization.

The interaction between diltiazem and left ventricular function after myocardial infarction. Multicenter Diltiazem Post-Infarction Research Group.

Abstract: The interactions between diltiazem and three parameters of left ventricular function using cardiac death as the end point were investigated in 2,466 patients, aged 25-75 years, who were involved in the long-term diltiazem postinfarction trial. Indexes of left ventricular function included pulmonary congestion on chest x-ray, acute anterolateral Q wave myocardial infarction on electrocardiogram, and radionuclide ejection fraction. Pulmonary congestion and acute anterolateral infarction had significant (p less than 0.01) interactions with treatment allocation, and the third variable, ejection fraction, showed a similar trend (p less than 0.1). There was a diltiazem-related reduction in cardiac death (Cox hazard ratio, 0.76-0.86) for each of the parameters reflecting good ventricular function, and a significant diltiazem-related increase in cardiac death (Cox hazard ratio, 1.52-1.85) for each of the parameters associated with impaired function. Three-factor interactions highlighted the extremes of the favorable and adverse effects of diltiazem in subsets with unimpaired and impaired left ventricular function. These findings permit more appropriate selection of patients for the safe and effective administration of diltiazem to postinfarction patients.

Repolarization duration variability: a tool to quantify the autonomic balance at the ventricle

Abstract: In order to gain insight into the process of cardiac repolarization, the authors defined and studied the repolarization duration variability (RDV) on electrocardiograms. Spectrum techniques were used to evaluate the influence of the autonomic nervous system in the control of repolarization duration (RD). Coherence analysis was used to quantify common contributions between RDV and heart rate variability. The latter gave a reference of the sympathovagal balance. It was found that the autonomic nervous system acts tonically and directly to control RD. This action is mediated through both autonomic limbs. >