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    • A decreasing trend in CRT D implantation has been

    2019-05-18

    A decreasing trend in CRT-D implantation has been reported recently, based on the database from the National Inpatient Sample in the USA [20]. They found that advancing age and an increasing comorbidity burden were associated with a reduced likelihood of CRT-D, and speculated that the decline in CRT-D implantation may reflect the intersection of high-comorbidity patients and the expectation of reduced ICD benefit in this patient population [20]. We found some differences in the patient characteristics between CRT-D and CRT-P (Table 1). These included age, sex, LVEF, QRS duration, QT interval, hemoglobin, and history of NSVT, hypertension, and persistent AF. However, when these patients’ background data in recent years were compared to previous years, a significant difference was observed only in age and prior NSVT. Therefore, the decrease in CRT-D and the increase in CRT-P implantation may be closely associated with the advancing age of the population in recent years. The proportion of CRT-D implantations in primary prevention patients with a CRT device was 83% (2714 of 3269) in the present study. This was comparable to the 86% found in the USA [20], and was higher than the 69% reported in Europe (the CeRtiTuDe cohort study) [21]. Differences in the patients’ characteristics between CRT-D and CRT-P recipients were found by observational studies from Japan (JCDTR), Europe [21], and the USA [20]. For example, patients with AF were likely to receive CRT-P in Europe and the USA; however, this was not apparent in Japan. The etiology of the underlying nf-κb pathway diseases was one of the most striking differences. In Japan, the prevalence of ischemic heart disease was less than 30%, and it did not differ between the CRT-D and CRT-P population. In contrast, the ischemic etiology was 49.3% of CRT-D and 40.7% of CRT-P (CRT-D vs. CRT-P, P=0.003) in Europe [21], and 67.7% of CRT-D and 53.1% of CRT-P (CRT-D vs. CRT-P, P<0.001) in the USA [20]. Because there appear to be some modulator variables influencing the benefit of a defibrillator in CRT patients [18], differences in the choice of CRT devices and the patients’ backgrounds could affect the clinical outcome of heart failure patients requiring CRT. Further studies examining the prognosis of CRT patients are necessary to validate our choice among CRT devices in daily clinical practice in Japan.
    Conclusions
    Conflict of interest
    Acknowledgments
    Case report During the electrophysiologic study, retrograde conduction was central and decremental. Atrial pacing at 400ms:280ms reproducibly induced the clinical BCT. Fig. 1A shows that conduction switched from nodal (narrow QRS complexes with distinct His potential—solid blue arrow) to the atriofascicular pathway (LBBB-like complexes and interpolation of the His potential—dotted blue arrow) during Wenckebach-pacing maneuver. Fig. 1B shows that the IntellaTip MiFi ablation catheter was used to map the atriofascicular pathway potential in sinus rhythm. The 8-mm tip ablation catheter has three radially positioned, equally spaced mini-electrodes, 2mm from the tip. Bipolar recordings were made between these mini-electrodes: m1–2, m2–3, and m3–1. This enabled precise signal localization and clearer identification of the pathway potential than the conventional ablation distal bipolar recording (blue dotted box, Fig. 1B). The gains on the catheter mini-electrodes were 5000-fold greater, and those in the conventional distal pole of the ablation catheter were 10,000-fold greater. The pathway potential was located at the 7-o׳clock position on the tricuspid annulus. Radiofrequency ablation (RFA) at this site (60°C, 70W, and 120s) resulted in no pathway conduction and non-inducible BCT.
    Discussion Atriofascicular pathways consist of fibers arising from the right atrial free wall and insert at or adjacent to the distal right bundle. They usually only conduct in an anterograde manner, participating in the anterograde limb of an antidromic atrioventricular reciprocating tachycardia (AVRT) with LBBB-like morphology and decremental properties [1]. Standard therapy involves targeted RFA around the tricuspid annulus as nf-κb pathway guided by pathway potentials also known as Mahaim (M) potentials [2,3]. These M potentials can be as large as the His deflection or can be small and narrow with a low amplitude [4]. Furthermore, unintentional mechanical trauma by catheter manipulation can result in transient abolition of these potentials from a few minutes to a few hours [1,5]. These M potentials are also recorded only in close proximity to the atrial insertion site, and thus, accurate localization and ablation at this site result in successful abolition of this pathway [5–7]. Hence, ablation of these atriofascicular pathways can be challenging.