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  • Because our patient s native rhythm remained AV


    Because our patient׳s native rhythm remained 2:1 AV block with a narrow QRS, we attempted HBP as the first-line treatment based on the assumption that His-Purkinje conduction might be preserved. Another benefit of HBP in this patient with CKD is that the use of iodinated Z-DEVD-FMK media could be avoided. HBP using a deflectable lead delivery system was easily achieved with a fluoroscopic time of 8 minutes. Lustgarten et al. reported that HB pacing lead placement with this system was no more difficult and took less time to implant than placement of a LV lead [3]. Our patient is thought to be a super-responder to CRT by HBP although the form of HBP was nonselective. However, there seems to be no significant clinical difference between selective HBP (His-only capture) and nonselective HBP because both forms do not alter physiological impulse conduction and possibly maintain rapid and synchronous LV activation. Indeed, Catanzariti et al. reported that no difference was observed between the two forms of HBP at acute measures of dyssynchrony [4]. Most patients with PICM having a native narrow QRS have preserved His-Purkinje conduction, and therefore upgrading to HBP would be expected to restore physiological synchronous LV activation. Recently, Vijayaraman et al. demonstrated that His-Purkinje conduction could be normalized by permanent HBP in 76% of patients with infranodal AV block and a wide QRS complex, indicating intra-His block [5]. This finding suggests that many patients with PICM having a native wide QRS might have preserved distal His-Purkinje conduction, and permanent HBP at the distal HB (distal to the site of the block/delay) could restore physiological synchronous LV activation.
    Conflict of interest
    We read the article by Okumura et al. with great interest. The authors reported an ablation strategy applying manifest entrainment to treat adenosine triphosphate (ATP)-sensitive atrial tachycardia (AT) originating from the perinodal region. However, we have some concerns regarding the electrophysiological diagnosis of the tachycardia. The exclusion of atrioventricular nodal reentrant tachycardia (AVNRT) is essentially a prerequisite to diagnose AT. The authors excluded AVNRT based on the findings of atrioventricular dissociation during the ventricular pacing of tachycardia and a V–A–A–V activation sequence on ventricular induction of tachycardia. We do not believe Complexity these findings exclude the diagnosis of AVNRT. Recently, we reported a novel form of fast–slow (F/S) AVNRT incorporating a “superior” slow pathway located at the top of the Koch׳s triangle (sup-F/S-AVNRT) with electrophysiological characteristics that included a long RP interval, the earliest site of atrial activation near the His-bundle, ATP sensitivity, and the successful ablation site in the perinodal region, which were strikingly similar to those of the tachycardia in Okumura׳s study. Importantly, in some cases of sup-F/S-AVNRT, the finding was caused by ventriculoatrial block in the lower common pathway below the atrioventricular nodal reentry circuit and was satisfied because of double atrial responses using fast and superior slow pathways. Therefore, we wonder if the tachycardia in Okumura׳s study included sup-F/S-AVNRT. Furthermore, manifest entrainment was not specific to AT and was previously documented during atrial entrainment of AVNRT . Conflict of interest