Assessment of QT-RR intervals relation in patients with atrial fibrillation

QT-RR relation has been deeply investigated during sinus rhythm. However there are not established methods for the evaluation of QT-RR relation in patients with atrial fibrillation (AF). The aim of the present study was to assess the relation between QT and preceding RR intervals in ECG signal of patients with AF using different methods. We analysed data from 26 patients with persistent AF. A two-step procedure was used to detect T wave apex. In order to consider QT lag phenomenon during AF, the relation between RT and RR intervals was assessed by different methods, using from 1 to 5 preceding RR intervals. A linear regression was applied to compare the slopes. A slightly increase of the QT-RR slope was observed when a larger number of preceding RR intervals was considered (RT - RR₁ 0:030 ± 0:013, RT - RR_1-2 0:028 ± 0:012, n.s., RT - RR_1-3 0:033 ± 0:012, n.s., RT - RR_1-4 0:035 ± 0:016, p <0:0001, RT - RR_1-5 0:039 ± 0:018, p <0:0001, RT -RR_(1-5)m 0:048±0:022, p <0:0001, RT - RR₂ 0:000 ± 0:007, p <0:0001). The most significant variation was observed among the mean value of RT -RR₁ slope with the mean value of RT -RR_(1-5)m slope. Interestingly the RT-RR correlation was completely lost when only the second previous RR interval was considered.