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  • Introduction Dilated phase hypertrophic cardiomyopathy DHCM

    2019-04-18

    Introduction Dilated-phase hypertrophic cardiomyopathy (DHCM) is a rare subset of hypertrophic cardiomyopathy (HCM) [1]. Data available on sustained monomorphic ventricular tachycardia (SMVT) associated with DHCM is scarce. We report a rare case of SMVT caused by a large epicardial scar related to DHCM that mimicked ventricular tachycardia (VT) originating from the apical septum. The SMVT was resolved by catheter ablation. A detailed analysis of the electrophysiological findings is presented.
    Case report
    Discussion This report describes successful SMVT ablation in a patient with DHCM. Previous studies have described successful ablation of SMVT in patients with nondilated-phase HCM [2–5]. However, there are few reports describing SMVT associated with DHCM. Ueda et al. reported clinical and electrophysiological characteristics in patients with SMVT associated with DHCM [6]. The authors state that the SMVT circuits in DHCM patients are more likely to be located either at the basal septum or at the basal anterior to the anterolateral LV. However, in the present case, the VT was suspected to originate from the ventricular apical septum, based on surface ECG morphology. In addition, the QRS morphologies during entrainment pacing were almost identical for both ventricles, despite the long distance between the pacing sites. These findings suggest that both pacing points were close to the exit of the VT circuit. Thus, the reentry circuit was suspected to be located in the deep layer of the apical septum. However, we were not able to eliminate the circuits by the ablation of the earliest site of both ventricles or by bipolar ablation. Finally, epicardial ablation revealed that the critical isthmus spanned from the anterolateral wall to the exit site, which was also confirmed by entrainment. The location of the critical isthmus was consistent with the site described in a previous study [6]. A major concern in this Bindarit case was the long distance between the suspected exit based on the QRS morphology in the 12-lead ECG and the critical isthmus of the SMVT. This highlights the limitation of surface ECG, which only shows the exit site, in terms of identifying the reentrant circuit. Previous studies reported intramural or epicardial reentry circuits in some patients with HCM [2,3,6]. The extent of fibrosis is one of the important factors in an arrhythmic substrate, and delayed contrast-enhanced CMR provides information regarding the extent and distribution of fibrosis [7,8]. The extent of fibrosis may be significantly greater in DHCM patients than in individuals with nondilated-phase HCM. In the present case, CMR showed diffuse delayed enhancement in the LV septum and apical and lateral wall. The surface ECG morphology during sinus rhythm was unusual because of a large extent of DHCM-associated fibrosis. The VT circuit may have been surrounded by extensive scar tissue. Therefore, the 12-lead ECG in this case suggested that the exit of the VT circuit was located at a large distance from the critical isthmus. These arrhythmogenic lesions tend to be epicardial or deeply intramural rather than endocardial, which may explain the difficulty related to ablation in patients with DHCM. The 12-lead ECG is useful for predicting the origin of tachyarrhythmia [9]; however, its accuracy is low in patients with structural heart diseases [10]. The possibility of VT originating in the epicardium should be considered, even if its suspected origin is another ventricular site.
    Conflict of interest
    I have read with attention the case report by Kaya et al. entitled β€œIs it a typical crosstalk: Need for re-implantation?” The authors described atrial lead malfunction in a patient with a dual-chamber pacemaker. The right atrial lead tip was in close proximity to the tricuspid valve, but was it located in the ventricle or atrium? Pacing of the ventricle and the low sensitivity for detection of atrial activation suggest that the tip is located in the ventricle with far-field atrial activity sensation.