Letter to the Editor: Marino et al. Inappropriate mode switching clarified by using a chest radiograph

Abstract

To the Editor, I read with great interest the article by Marino et al. entitled “Inappropriate mode switching clarified by using a chest radiograph.” [1]. The authors have explained a case of dual-chamber pacemaker malfunction, caused by intermittent high-frequency noises. They claimed that this happened because of lead–lead interaction caused by excess slack of atrial and ventricular leads. In this case report, the authors did not explain the pacemaker parameters, such as the programmed lead sensation polarity (unipolar or bipolar), intrinsic R wave amplitude, and ventricular sensing threshold. With a close attention to the atrial and ventricular electrograms, it is clear that the noise is seen in both electrograms. The authors claimed that the noise is more prominent in the atrial channel than in the ventricular channel. However, this higher level of the noise in the atrial electrogram is due to automated gain, which increased the gain in the atrial channel. Thus, with the same gains, it seems that the noise amplitude will be the same, and changes in the amplitude in both the electrograms will be comparable at each moment. Replacement of the baseline with high-frequency signals, its simultaneity in both farfield electrograms, and no constant relation to the cardiac cycle are compatible with extra cardiac electromagnet interference. Myopotential oversensing is also presented with high-frequency noise, especially in widely spaced electrodes or unipolar electrograms, and can hence cause device malfunction, particularly when the sensing polarity is programed as unipolar. The effect of this interference may differ between atrial and ventricular electrograms, according to the distance from the sensing field of the electrodes. For excluding this possibility, it is better to look at the bipolar electrograms (recorded from closely spaced electrodes). Finally, as the authors have mentioned, some other possibilities, such as lead-connector problems, may present intermittently; however, the noise often saturates the amplifier range. Changes in the impedance may be documented during pocket manipulation [2]. Therefore, I recommend that the authors recheck the device settings such as sensing polarities and look for external electromagnetic interferences, as this is the most probable cause.