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The electrophysiological activity of the heart is recorded and presented in form of electrocardiogram (ECG). In 1998 the concept of P wave dispersion as the risk factor for atrial fibrillation (AF) recurrence was introduced. It was calculated as the difference between the longest and the shortest P wave. The aim of our study is to prove that the P wave dispersion is an artifact of low accuracy in P wave measurement. The study included 186 patients (78M 108F) aged 59.7 ± 12.9 years, undergoing various electrophysiological procedures. The P wave was measured twice: first, at the paper speed of 50 mm/s, enhancement 8× (standard – imprecise) and the second time at 200 mm/s, 64–256× (precise). The imprecise measurement method resulted in different duration of all P wave parameters in comparison with precise measurement. The difference between Δ P max and Δ P min indicated a higher value for the latter parameter. It was indicated that the imprecise P wave dispersion value correlated most significantly with the maximal P wave duration, which was measured in a similar way. In contrast with the imprecise measurement method, the minimal and maximal durations of the P waves, being measured accurately, were almost identical. Using precise methodology, the P wave dispersion reaches negligible values and tends to zero. The measurements of the P wave have to be precise to assure the highest scientific and medical sincerity. The highest clinical value is related to the P wave duration.

Background The P wave dispersion concept was created to describe the non-uniform atrial conduction as a separate AF factor. However the major assumptions of the theory are inconsistent with the main principle of electrocardiography, which assumes that 12 leads of ECG, recorded simultaneously, register the same events at the same time. The presence of dispersion suggests the presence of a P wave in one lead, while in the other one it has ended and no longer exists. This observation per se could be considered as a methodological artifact. Objective The major objective is to present that the P wave dispersion descends from imprecise measurements in various ECG leads. We intend to demonstrate that more accurate measurements make this parameter disappear. Methods Our study included 150 patients (89F, 61M) assessed using the electrophysiological system, which allowed to assess the sinus P waves. The P wave duration was measured by 3 independent researchers in all leads twice: 1. paper speed=50 mm/s, enhancement 16x (basic measurement) 2. paper speed=200 mm/s, enhancement 128–256x, simultaneously measuring the P wave dispersion. All measurements were repeated 3 times. Results The results are presented in Table 1 Conclusion 1. The P wave dispersion is the artifact of measurement. It is clear that after using much more accurate tools, the parameter disappears. 2. The P-wave dispersion is connected with Pmax, therefore may be apparently clinically useful but as a matter of fact, doesn't carry any meaning itself. 3.The significant P wave duration parameter should be a total atrial activation time, from the beginning of the earliest recorded P wave, till the end of the last Pwave recorded in any lead. Funding Acknowledgement Type of funding source: None

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Background: The ST segment is component of the QRS-T complex located between the QRS and the T wave. ST segment changes during tachycardia with narrow QRS mainly takes the form of ST segment depression. This phenomenon is often observed in young healthy people for whom an ischemic background is unlikely. Materials and methods: The study included 104 patients (71 women and 33 men) with paroxysmal narrow QRS complex tachycardia. In all patients electrophysiological study was performed and the diagnosis of atrioventricular nodal reentrant tachycardia was established. The arrhythmogenic substrate was then eliminated successfully by subsequent ablation using radiofrequency energy which confirmed the diagnosis, all patients had measured QRS components – QR, RS and RJ during the tachycardia and during the sinusrhythm. All of the measurements were done in lead V5. Results: The difference RJ-QR during tachycardia and sinus rhythm correlated negatively with tachycardia cycle length (R = 0.356, P = .001), first slowly, then rapidly reaching the cycle value of about 300 ms, then it decreases, stabilizing at the cycle level of about 270. By separating the RJ-QR in tachycardia and in the sinus rhythm from the tachycardia cycle, we can see that the correlation described in this point is largely due to the correlation between the heart rate and RJ-QR length in tachycardia. Conclusions: In patients with atrioventricular nodal reentrant tachycardia, there is a significant ST-segment depression during tachycardia episodes and the degree of this change is related to tachycardia cycle length. The most probable explanation of the ST-segment depression is the overlap of the QRS complex on the preceded T wave. This phenomenon is also influenced by some intrinsic properties of the individual electrocardiogram. It is possible to rule out ischemic origin of the presented ST segment change.