[primary] [ecg] [articles] [all entries]
New quantitative methods of ventricular repolarization analysis in
patients with left ventricular hypertrophy.
Ital Heart J 1(8):542-548, 2000
ABSTRACT
BACKGROUND: Left ventricular hypertrophy (LVH) is accompanied by specific
changes in ventricular electrophysiology which are potentially arrhythmogenic.
Nevertheless the electrocardiographic diagnostic signs for LVH have
a relatively low predictive power for arrhythmic events and sudden
death. We thought that other parameters derived from the surface
ECG not apparent at visual inspection might be detected by specific
analysis of electrocardiographic digital recordings. The purpose
of our work was to analyze the surface distribution of repolarization
potentials and search for subtle alterations not revealed by the
usual electrocardiographic processing which are likely to reflect
ventricular repolarization heterogeneity. METHODS: Body surface potential
maps were recorded from 62 chest leads in 16 patients with LVH due
to aortic stenosis and in 35 normal subjects. By applying a principal
component analysis of the ST-T waves we computed the similarity
index. The value of the similarity index is inversely proportional
to the variability of T wave morphology and a low value is considered
a marker of repolarization heterogeneity. RESULTS: The similarity
index was significantly lower in LVH patients than in normals both
in 62 leads (0.73 +/- 0.067 vs 0.77 +/- 0.044 p = 0.03) and in 12
unipolar leads (V1- V8 V3R VR VL VF) extracted from the map (0.77
+/- 0.075 vs 0.81 +/- 0.045 p = 0.03). Moreover we computed the
'late repolarization deviation index' which quantifies the instantaneous
variations of surface potential distribution from peak to end of
the T wave. This index was significantly higher in LVH patients than
in controls (in 62 leads 0.07 +/- 0.05 vs 0.028 +/- 0.016 p = 0.005;
in 12 leads 0.064 +/- 0.052 vs 0.024 +/- 0.020 p = 0.008). CONCLUSIONS:
The values of similarity index and of late repolarization deviation
index found in LVH patients suggest a higher than normal degree of
repolarization heterogeneity not detected by the usual electrocardiographic
analysis. Since both indices maintained statistical significance
when calculated on the 12 leads derived from our map lead system
they could be reliably computed from digital recordings of the 12
conventional leads.
[Medline]