Impact of the high-frequency cutoff of bandpass filtering on ECG quality and clinical interpretation: A comparison between 40 Hz and 150 Hz cutoff in a surgical preoperative adult outpatient population

• There is a large prevalence of deviations from the recommended cut-offs of ECG filtering.
• This study investigates the impact of 40 Hz high pass filtering compared to 150 Hz high pass filtering on ECGs perceived quality and clinical interpretation.
• We demonstrated that the 40 Hz high pass filtering does not affect ECG clinical interpretation, while allowing better quality of tracings.

BackgroundIn 1990 the American Heart Association (AHA) established a standard 0.05 to 150 Hz bandwidth for the routine recording of 12-lead electrocardiograms (ECGs). However, subsequent studies have indicated a very high prevalence of deviations from the recommended cutoffs.ObjectiveThis prospective observational study investigates the impact of 40 Hz compared to 150 Hz high-frequency cutoffs on ECG quality and clinical interpretation in a single-center surgical outpatient population.Methods1582 consecutive adult patients underwent two standard 12-lead ECG tracings using different high-frequency cutoffs (40 Hz and 150 Hz). Two blinded cardiologists randomly reviewed and interpreted the recordings according to pre-defined parameters (PR and ST segment, Q and T wave abnormalities). An arbitrary score, ranging from 1 to 3, was established to evaluate the perceived quality of the recordings and the non-interpretable ECGs were noted. The tracings were then matched to compare interpretations between 40 and 150 Hz filters.ResultsA 40 Hz high-frequency cutoff resulted in an increased rate of optimal quality ECGs compared to the 150 Hz cutoff (93.4% vs 54.6%; p < 0.001) and a lower rate of non-interpretable traces (0.25% vs 4.80%; p < 0.001). Analyzing the morphologic parameters, no significant differences between the filter settings were found, except for a higher incidence of the J-point elevation in the 40 Hz high-frequency cutoff (p = 0.007) and a higher incidence of left ventricular hypertrophy in the 150 Hz high-frequency cutoff (7.4% vs 5.4%, p < 0.001). The latter was noted only in ECGs with borderline QRS amplitudes (between 3.3 and 3.7 mV; p < 0.001).ConclusionDespite current recommendations, the large deviation from standard high-frequency cutoff in clinical practice does not seem to significantly affect ECG clinical interpretation and a 40 Hz high-frequency cutoff of the band-pass filtering may be acceptable in a low risk population, allowing for a better quality of tracings.