Day-to-day variability of voltage measurements used in electrocardiographic criteria for left ventricular hypertrophy.
Academic Article
Overview
abstract
Although electrocardiographic (ECG) voltage can be used to estimate left ventricular mass, day-to-day variability of voltage combinations used for this purpose must be established before ECG changes are taken as evidence of progression or regression of hypertrophy. Accordingly, serial ECGs (mean 8 days apart), derived from 10 s samples digitized at 250 Hz, were examined in 78 patients with no intercurrent change in clinical status. The coefficient of variation was calculated as 1 SD of the difference between paired voltage measurements, divided by the average mean value. Coefficient of variation for single leads was 22.3% for SV1, 27.0% for RV5 or RV6, 27.1% for RaVL and 34.7% for SV3. Coefficient of variation was lower for voltage combinations than for individual lead measurements: 18.5% for Sokolow-Lyon voltage (SV1 + RV5 or RV6), 22.3% for Gubner-Ungerleider voltage (R1 + S3) and 24.8% for Cornell voltage (RaVL + SV3). Serial reclassification due to variation above and below standard criteria for left ventricular hypertrophy occurred in only 3% of patients for Sokolow-Lyon voltage and 4% of patients for Cornell voltage in this group. Minute to minute reproducibility of voltage was assessed with electrodes in place in a separate group of 26 patients, and the coefficient of variation was 2.6% for Sokolow-Lyon voltage, 5.9% for Gubner-Ungerleider voltage and 2.9% for Cornell voltage. These data indicate that serial variability of computer-measured ECG voltage combinations is high, due primarily to changes in lead placement and body position, but less than the variability of computer-measured voltage in individual leads.
