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    • The patient has fared well without

    2019-05-04

    The patient has fared well, without any lead malfunctions, lead dislodgement, or inappropriate shocks. Follow-up echocardiography showed no aggravation of tricuspid regurgitation. Sufficiently high atrial and ventricular amplitudes (P-wave: 3.5mV and R-wave: 9.9mV) were confirmed during 18 months of follow-up.
    Discussion Because of significant progress in pediatric cardiac care, a growing number of patients with congenital GSK503 manufacturer disease survive well into adulthood [1,2]. The management of arrhythmia in adult patients with congenital heart disease represents an important issue for cardiologists [3–5]. Ebstein’s anomaly is characterized by apical displacement of the septal and posterior leaflets of the tricuspid valve. Approximately 25% of these patients have associated accessory pathways and are at risk of supraventricular tachycardia. Unless atrial fibrillation degenerates into ventricular fibrillation in patients with manifest accessory pathways, ventricular arrhythmia is a rare complication of Ebstein’s anomaly [6]. In a multicenter cohort study, ventricular arrhythmia occurred in only 1 of 77 young patients with Ebstein’s anomaly who received an ICD [7]. In our case, electroanatomical voltage mapping found a wide low amplitude area around the atrialized ventricle. Although ventricular tachyarrhythmia was not induced by programmed stimulation, this low voltage area may be associated with an arrhythmogenic region in this patient. Lacking a histological investigation, we could not specify the pathological mechanism underlying these electrophysiological changes. Implantation of the device in this patient was technically challenging because of the unusual orientation of the right ventricle. Electroanatomical mapping can be used to determine the exact intracardiac anatomy and confirm the amplitude of the cardiac chambers, especially in patients with complex cardiac anatomy [8,9]. In the present case, prior electroanatomical information was helpful in planning the transvenous procedure strategy. Therefore, we believe that electroanatomical mapping is a useful, minimally invasive strategy to be performed prior to the implantation of devices in patients with a complex cardiac anatomy. We selected the thinnest ICD device (TELIGEN 100 F111, Boston Scientific Inc.) because the size of the patient’s body was quite small, and her precordial subcutaneous fatty layer was assumed to be relatively thinner. The Guidant ICD lead (a shock lead) is an integrated bipolar system, and consequently, we should pay close attention to avoiding atrial oversensing, especially when deep insertion of the shock lead is impossible. Although we could not advance the lead into the apical site, probably because of an enlarged anterior leaflet of the tricuspid valve, atrial double sensing was never observed during the implantation procedures.
    Conflict of interest
    Introduction Diagnostic features implemented in implantable pacemakers have proven useful for clinical decision making. Specifically, monitoring of the atrial tachyarrhythmia (AT) burden by pacemaker diagnostics, for example, has been widely recognized as an important tool for therapy improvement. However, it may be difficult to set the atrial sensitivity for proper sensing during ATs at the time when the patients are in sinus rhythm. A low sensitivity setting may lead to true undersensing during ATs. Contrary, paradoxical atrial undersensing (PAUS), a rare phenomenon, is defined as atrial undersensing at a high programmed atrial sensitivity and with the return of normal atrial sensing at a lower programmed sensitivity during ATs [1]. Herein, we report a case of PAUS of atrial fibrillation (AF) associated with quiet timer blanking, and review the literature.
    Case report The patient is a 66-year-old man who had a Kappa dual-chamber pacemaker (Model KDR 921; Medtronic Inc., Minneapolis, MN, USA) implanted for advanced atrioventricular block in 2006. The atrial lead was Isoflex 1642T (St. Jude Medical, St. Paul, MN, USA) and the ventricular lead was Isoflex 1646T (St. Jude Medical). He had a history of myocardial infarction and paroxysmal AF. The pacemaker was programmed to the DDD mode with a lower rate of 60ppm, atrial sensitivity of 0.5mV, the Sensing Assurance function set to on, and an atrial high rate episode detection rate of 180ppm. More detailed programming information can be found in Table 1. Since the implantation of the pacemaker, the patient had been followed every 6 months. In July 2010, during a follow-up visit, AF was confirmed by the surface ECG and an atrial intracardiac electrogram (AEGM), as shown in Fig. 1A. Despite the detection of AF potentials with amplitudes of 5.6–8.0mV, the marker did not indicate a sense, and atrioventricular sequential pacing continued without mode switch operation. Since atrial sensitivity was set to 0.5mV, true undersensing was not thought to be a cause of this phenomenon and other causes were considered.