Based on the methodology used in previous studies the
Based on the methodology used in previous studies, the EGM source for the Wavelet algorithm has been nominally programmed as the Can-RV coil EGM . As the nominal EGM source includes the generator, myopotentials induced due to body motion or other muscle activity are likely to influence the arrhythmia detection system. Swerdlow et al. reported that exercise-induced myopotential interference combined with low-amplitude EGM on the Can-RV coil EGM source caused inappropriate detection of sinus tachycardia by the Wavelet-transform morphology algorithm . The WAVE study also showed that the Wavelet algorithm failed to discriminate 174 of the 885 true SVT episodes. Myopotential noise on the EGM source during SVT was detected in 0.5% of the 885 true SVT episodes, which resulted in approximately 2.3% of the 174 inappropriate detections . Furthermore, it Etonogestrel is reported that 10% of 304 inappropriate VT/VF detections of the 860 true SVT episodes were caused by myopotential noise in the Wavelet algorithm . Although myopotential interference has not been recognized as a major reason for inappropriate VT/VF detections during true SVT, it remains an important issue to be resolved, even after the widespread use of the Wavelet algorithm. In fact, the current case report clearly showed that myopotentials induced by an epileptic seizure caused inappropriate VT/VF detections, which in turn led to inappropriate ICD shock delivery.
Importantly, our report provides not only a possible limitation of the Wavelet algorithm, but one of the methods to resolve myopotential interference. In order to eliminate the effect of myopotentials derived from epileptic seizures, the nominal direction of EGM recording for the Wavelet—the Can-RV coil—needed to be changed. Wolber et al. reported that the EGM source composed of the SVC coil-RV coil has the same high detection rate as that of the Can-RV coil, and is also affected by body motion to a lesser extent . Using the same reasoning, we decided to change the EGM direction from the Can-RV coil to the SVC coil-RV coil, resulting in the prevention of inappropriate ICD shock delivery during subsequent epileptic seizures.
The RV tip-RV ring EGM, shown in Figs. 2A and 3A, plays an important role in the detection of RV lead fractures associated with high frequency noise, which may result in an inappropriate ICD shock. However, this can be avoided by a functional algorithm termed as “lead noise discrimination and alert” on the RV tip-RV ring EGM. The use of a similar algorithm for the Can-RV coil EGM could be effective for preventing inappropriate ICD shock due to epileptic seizures. Furthermore, the Wavelet algorithm has been nominally programmed only for the Can-RV coil EGM, and not for the RV tip-RV ring EGM. Therefore, programming the Wavelet algorithm for the RV tip-RV ring EGM could also potentially prevent inappropriate ICD shock delivery. This suggestion can be supported by the fact that no myopotential was observed on the RV tip-RV ring EGM in the present case.
Finally, the device interrogation data of the patient showed a number of SVT events without any myopotential noise (Figs. 1 and 2), indicating the occurrence of many attacks of AF without any seizures. These findings suggest that a pathological relationship between the occurrence of AF and epileptic seizure is unlikely.
Conflict of interest
Case report A 66-year-old man with a history of hypertension and symptomatic paroxysmal AF underwent extensive encircling PV isolation. However, after the initial successful PV isolation, he developed multiple episodes of paroxysmal AF after 3 months of blanking periods. Six months later, he underwent a second catheter ablation. After confirming electrical isolation of the 4PVs, intravenous isoproterenol (1.7 and 3.4µg/min) was administered. This provoked frequent APBs originating from the right atrium (Fig. 1). These APBs invariably initiated a sustained AF. Therefore, contact activation mapping using the CARTO system (Biosense Webster Inc, Diamond Bar, California, USA) could not be performed without frequent electrocardioversion. To avoid the initiation of AF, we administered nifekalant (0.2mg/kg bolus followed by continuous injection of 0.2mg/kg/h) in addition to isoproterenol. This resulted in the maintenance of frequent APB firing without the initiation of AF (Fig. 2), allowing completion of activation mapping of both the sinus beat and APB, which was located 14mm away from the sinus node at the right atrial free wall (Fig. 3). Radiofrequency ablation was delivered cautiously with an irrigated tip catheter at a power of 25W for 45s, which eliminated the APB. During the 6-month follow-up period, no AF recurrence or sinus node dysfunction was observed, and the patient was not taking any antiarrhythmic drugs.