br Materials and methods Fifteen healthy adult men

Materials and methods Fifteen healthy adult men participated in this study. The left anterior chest area was subdivided into 15 regions based on 5 longitudinal points (from the second to the sixth intercostal spaces) and 3 lateral points (including the left sternal border, midclavicular line, and anterior axillary line) (Fig. 1). The R wave amplitude was recorded by identifying the center of the simulant bipolar electrodes in each area by rotating the electrodes to the vertical axis (A), horizontal axis (B), 45° to the left (C), and 45° to the right (D) (Fig. 1). In addition, there is a flap-electrode attached to the package of the Reveal DX (Fig. 2), and it is possible to measure the R wave amplitude using this electrode. However, the flap-electrode is single-use, and this trial required the measurement of many patterns; thus, the durability of the electrode was unknown. Thus, we used a normal disposable electrode with the same electrode spacing as the Reveal DX to measure the R wave amplitude in the present study (Fig. 3).
Results
Discussion This study aimed to investigate the optimal electrode position for ILR cell division cycle with a high R wave amplitude and no height variation, regardless of different body positions and electrode angles. In the present study, the R wave amplitude data collected from 15 participants at all body positions and electrode angles were assumed to be normally distributed. The mean (m) and the standard deviation (σ) were calculated, and the minimum amplitude value was estimated by subtracting twice the value of the standard deviation from the mean value (m−2σ). Fig. 7 shows an example of the actual R wave amplitude distribution attained in this study and the optimal normal distribution curve calculated by normal probability plotting. Furthermore, the mean and the standard deviation of the optimal normal distribution curve were calculated and m±σ and m±2σ are also shown in the graph. It was shown that 97.7% of the R wave amplitude (filled area) was greater than the estimated minimum amplitude value (m−2σ, in this case 0.144mV). Generally, the aforementioned statistics are used with the estimated minimum amplitude value calculated by subtracting 3σ from the mean value (i.e., 99.9% of the data is greater than this value). However, if this was followed in the present study, the electrode positions with an estimated minimum amplitude value greater than 0.3mV (manufacturer-recommended value) would not have existed. Hence, competitive exclusion study accepted m−2σ as the estimated minimum amplitude value. The amplitude data obtained from subjects in the supine position had an estimated minimum amplitude value greater than 0.3mV (although some areas fell slightly below this but within acceptable limits), with the only exception being the data gathered at the second intercostal space. Namely, when electrode positions were investigated in the supine position, all areas except for the second intercostal space reached acceptable amplitude values. Additionally, the R wave amplitude was inclined to increase with electrodes located either on the inferior intercostal space or closer to the sternum, while right 45° or vertical angles attained higher R wave amplitudes. Thus, if the region for implant was chosen based only on the height of the R wave amplitude in the supine position, the electrodes might be located in an area where amplitude varies as a result of changes to the body position; this in turn could lead to false diagnoses. In order to avoid this, the most reliable method for choosing an implant position was presumed to be investigation of the areas around the left sternal border of the fourth intercostal space, where the impact of body position was the smallest. R wave amplitude values should be greater than 0.3mV regardless of body position.
Conclusion If the location for ILR implant is chosen based only on the height of the R wave amplitude in the supine position, the electrodes could be located in an area where amplitude varies by changing body positions which could lead to false diagnoses. Although R wave amplitudes change depending on body positions, the minimum amplitude value was estimated to be greater than the manufacturer-recommended value of 0.3mV on the midclavicular line on the third intercostal space position 5, the left sternal border on the fourth intercostal space position 7, the midclavicular line on the fourth intercostal space position 8, and the left sternal border on the fifth intercostal space position 10, with electrodes positioned at a vertical angle (A), or on the left sternal border at positions 4 and 7 on the third and fourth intercostal spaces at a right 45° angle (D).