Article

Differences between QT and RR intervals in digital and digitized paper electrocardiograms: contribution of the printer, scanner, and digitization process.

Research Section, Quintiles ECG Services, Mumbai, India.
Journal of electrocardiology (impact factor: 1.08). 06/2008; 41(5):370-5. DOI:10.1016/j.jelectrocard.2008.02.026
Source: PubMed

ABSTRACT Prints of electrocardiograms (ECGs) are often sent to core laboratories, where they are scanned, converted to a digital format, and read on-screen. These ECGs may differ from the original ECG because of variability introduced by the printer, scanner, or digitization software.
Digital ECGs were recorded in 50 volunteers simultaneously using electrocardiographs from 2 different manufacturers. QT and RR intervals were measured on-screen on the digitized ECGs. To study the contribution of individual steps in the digitization process, differences in RR interval between 2 prints each of 50 digital ECGs, 2 scanned files of 50 prints, 2 digitized files from 50 scanned files, and 2 readings of 50 digitized ECGs (intrareader variability) were analyzed.
Repeatability coefficient for RR interval measurement was 18.5 milliseconds for machine 1 and 21 milliseconds for machine 2. Contributions of the printer were 6.5 milliseconds for machine 1 and 9.0 milliseconds for machine 2, digitization process was 5.5 milliseconds, and reader variability was 8.0 milliseconds. Variability of the scanner was negligible.
The printer and digitization process account for significant differences in interval measurements in digitized ECGs.

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Keywords

2 different manufacturers
 
2 prints
 
2 readings
 
2 scanned files
 
21 milliseconds
 
50 digital ECGs
 
50 digitized ECGs
 
50 prints
 
50 scanned files
 
50 volunteers
 
Digital ECGs
 
digital format
 
digitization process account
 
digitization software
 
digitized ECGs
 
intrareader variability
 
machine 1
 
machine 2. Contributions
 
reader variability
 
RR interval measurement
 

Pooja Hingorani