Quantitative assessment of eight different methods for synthesizing Frank VCGs from simultaneously recorded standard ECG leads.
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Electrocardiography↗
Biomedical subjects
J Fayn
Publications and source records attributed to J Fayn.
Methodology of ECG interpretation in the Lyon program.
To provide an in-depth interpretation of the spatial QRS-T contour, we established a set of vectorcardiographic parameters computed octant by octant. For each statement the criteria constitute a model which is closely related to pathophysiological patterns. The diagnostic strategy is of the heuristic type. For each diagnosis a table lists several criteria providing both specific and differential diagnostic information. Inter-table competition is handled by specific logic. The program classifies diagnoses according to the number of non-satisfied criteria. Three versions are available including 124, 51 and 7 diagnoses, respectively. The first, intended for interpretation of complex situations, has given satisfactory results in such situations. Rhythm analysis is performed from 8-second recordings. All functions--acquisition, quality control, choice of a dominant complex, wave recognition, parameter extraction, interpretation, editing, storage--are integrated into a mobile cart. A complementary program performs serial analysis of successive tracings. It highlights with great precision morphological changes in the spatial loops and interval variations.
Diagnosis, Computer-Assisted↗
CAVIAR: a serial ECG processing system for the comparative analysis of VCGs and their interpretation with auto-reference to the patient.
The authors present a new computer program for serial ECG analysis that allows a direct comparison of any couple of three-dimensional ECGs and quantitatively assesses the degree of evolution of the spatial loops as well as of their initial, central, or terminal sectors. Loops and sectors are superposed as best as possible, with the aim of overcoming tracing variability of nonpathological origin. As a result, optimal measures of evolution are computed and a tabular summary of measurements is dynamically configured with respect to the patient's history and is then printed. A multivariate classifier assigns each couple of tracings to one of four classes of evolution. Color graphic displays corresponding to several modes of representation may also be plotted.
Data Display↗
New methods of quantitative assessment of the extent and significance of serial ECG changes of the repolarization phase.
The authors present a method for optimally measuring variations in T wave shape and time intervals for the quantitative assessment of the significance of serial changes of the repolarization phase. The results, established on a healthy population, show the inadequacy of Bazett's formula, the constancy of maximum of T to the end of the T time interval, and good stability of the spatial T loops' morphotype. Residual intrasubject variability of corrected QT interval is mainly ascribable to physiologic, heart rate-independent changes in true onset of Q to a maximum of T time interval. The optimized mean quadratic deviation between two serial T loops is well correlated with changes in drug concentration.
Adult↗
Heterogeneous effect of quinidine on the ventricular depolarization process assessed by the spatial velocity electrocardiogram of the QRS complex. Preliminary report of a new investigative method.
The negative conduction effect of quinidine on each of the successive phases of the ventricular depolarization was investigated using an original noninvasive method: the spatial velocity electrocardiogram of the QRS complex (SVECG-QRS). We performed a randomized placebo-controlled trial in 10 healthy subjects with a single oral dose of quinidine (330 mg) or placebo. Electrocardiographic acquisition and processing (220 recordings for the complete trial) were performed using the Lyon vectorcardiographic program. For each SVECG-QRS curve, the position of seven specific points from A (onset of QRS) to G (end of QRS) were determined precisely. The six successive time intervals between these points (AB-FG) and five velocity values (B-F) were then calculated. The QRS complex was longer under quinidine than placebo (102.4 +/- 1.6 vs. 100.3 +/- 1.5 ms). The difference was at the periphery of statistical significance (p = 0.05), and this lack of statistical difference may be mainly due to the low serum levels of quinidine obtained at the peak of the concentration (1.46 +/- 0.4 mg/1). All six QRS time intervals were longer under quinidine, but only the BC interval was significantly different (9.3 +/- 1.1 vs. 18.8 +/- 1.1 ms; p < 0.05) suggesting a more pronounced negative conduction effect at the onset of ventricular depolarization. No significant modifications were observed for the velocity values. We conclude that (1) the negative conduction effect of quinidine is heterogeneous, but a further study with a higher dose of quinidine (concentration-dependent effect) is required to confirm this hypothesis and (2) the spatial velocity electrocardiogram of the QRS complex allows a detailed analysis of the ventricular conduction phases. The results of the measurement were found to be reproducible. This noninvasive tool could be used in clinical practice to assess effects of antiarrhythmic drugs on successive ventricular depolarization phases.
Administration, Oral↗