Determination of atrial fibrillation frequency using QRST-cancellation with QRS-scaling in standard electrocardiogram leads

Non-invasive assessment of the atrial cycle length can be obtained through QRST-cancellation algorithms. The main spectral component of the QRST-cancelled ECG gives an indication of the atrial cycle length. Due to QRS amplitude variations (eg caused by respiration) small residuals of QRS complexes can remain in the final ECG. We applied a QRST scaling algorithm to minimize these effects. Standard 12-lead ECG was recorded, simultaneous with both left (LA) and right (RA) intracardiac atrial electrograms. We applied a QRST-cancellation algorithm with automatic QRS-amplitude correction on both atrial fibrillation signals and atrial flutter signals. On average over all leads the percentual deviation between the intracardiac right atrial dominant frequency and the frequency measured on the standard ECG leads was 1.04% for atrial flutter and 2.16% for atrial fibrillation. For comparison with the LA fibrillation frequency, errors were slightly higher (flutter: 3.05%, fibrillation 2.31%). It is concluded that the QRST-cancellation algorithm with automatic QRS amplitude adjustment performs accurate on both atrial fibrillation signals and atrial flutter signals. These methods can have substantial clinical importance in monitoring non-invasively the atrial cycle length after interventional procedures or medication administration