The subcutaneous implantable cardioverter defibrillator (SICD) is effective for sudden cardiac death prevention in patients with hypertrophic cardiomyopathy (HCM).¹ SICDs can be used in eligible patients without pacing indications to avoid the potential complications associated with intravascular lead placement. Preimplant ECG screening to evaluate QRS and T‐wave sensing is performed to decrease the risk of inappropriate shocks. With proper screening, oversensing in patients with HCM can be minimized despite significant left ventricular hypertrophy and repolarization abnormalities. Patients with left bundle‐branch block (LBBB) often fail preimplant screening.² Thus, patients with HCM who have undergone septal myectomy and develop iatrogenic conduction abnormalities are often not candidates for SICD implant. Similarly, there may be hesitancy of implanting SICD in patients with obstructive HCM who might ultimately require septal myectomy. In this regard, we have followed a cohort of patients with HCM and iatrogenic LBBB and SICD. The majority of these patients underwent myectomy after already having had SICD implantation, whereas others screened in for SICD despite the development of LBBB post myectomy. The potential risks associated with maintaining SICDs in this population remain uncertain.^{3, 4} Therefore, we believe it is timely to describe our experience to help guide strategies for the prevention of oversensing and inappropriate shocks in these patients.

This study was approved by the Tufts Health Sciences Institutional Review Board, and informed consent was not required. Data that support the findings of this study are available upon reasonable request. We describe 9 patients with HCM and SICD and septal myectomy (Figure [A]). Eight of the patients were male and mean±SD age at the time of myectomy was 42±14 years. SICDs were implanted between 2014 and 2021 and mean follow‐up was 44.1±29 months. All patients had dual zone programming with a conditional zone (mean 210±12 bpm) and a ventricular fibrillation zone (mean 235±12 bpm). SMART pass filter was enabled in second‐ and third‐generation SICDs (in 7 of the 9 patients). Seven of the patients (78%) were implanted with SICD beforemyectomy. The average time from SICD implant to myectomy was 20.7±13.6 months. All patients underwent successful preimplant screening for SICD, 2 with the automated screening tool and 7 with manual ECG screening before availability of the automated tool. One patient experienced an appropriate shock for ventricular fibrillation before myectomy.

A, Seven patients underwent myectomy following SICD. Two of them had TWOS with 1 IAS. No events noted after vector change. Two patients underwent SICD after myectomy. One of those had TWOS. No events noted after vector change. Electrograms in a single patient with SICD implanted after myectomy. A, SICD electrogram with TWOS 4 months after implantation. B, SICD electrograms with resolution of TWOS after sensing vector change. IAS indicates inappropriate shock; LBBB, left bundle‐branch block; SICD, subcutaneous implantable cardioverter defibrillator; and TWOS, T‐wave oversensing.

Post myectomy, all patients developed LBBB with QRS duration between 133 and 166 milliseconds (mean 146±9 milliseconds), and all patients were subsequently interrogated with morphology update and adjustment of sensing vectors as necessary. Three patients maintained the primary vector post myectomy, and 4 of the 7 patients had a change in sensing vector: 2 were reprogrammed from alternate to primary, 1 from primary to secondary, and 1 from primary to alternate. Notably, the patient reprogrammed from primary to secondary had required manipulation of the electrode during the surgery owing to the position of the electrode in relation to the sternotomy. T‐wave oversensing was observed in 2 patients, 1 of whom developed a drop in R wave amplitude while squatting with 2 inappropriate shocks 4 months after myectomy. The sensing vector was subsequently changed from primary to alternate with no further oversensing or inappropriate shocks for the last 7 years. To date, no patients have required explant of SICD with conversion to a transvenous system.

The remaining 2 patients underwent SICD implantation after myectomy, both of whom screened OK using the manual screening tool before implant. Neither patient has experienced appropriate or inappropriate shocks. One patient was noted to have T‐wave oversensing in the primary vector and underwent vector change to alternate with no oversensing for the last 5 years (Figure [B]). He recently presented for SICD generator replacement due to normal battery depletion. Interestingly, this provided us an opportunity to rescreen him using the external automated programmer screening tool, during which he failed screening in all 3 vectors (with ECG electrodes placed overlying his device and the subcutaneous electrode). Nevertheless, given that sensing was suitable after programming him in the alternate vector, generator change was performed and he continues with SICD implant without further events.

Our experience describes the largest series of the SICD after myectomy in patients who develop iatrogenic LBBB. Two previous case reports raised concern of SICD use in this unique subset of patients. In 1 case, T‐wave oversensing post myectomy resulted in inappropriate shock and subsequent change in sensing vector.³ The second case in a pediatric patient required explant of the SICD post myectomy due to unsuitability of any sensing vector with consequent implant of a transvenous system.⁴ In contrast, our experience suggests that maintenance of SICD in patients with HCM after the development of conduction abnormalities from septal myectomy might be feasible. Post myectomy, interrogation should include update of morphology templates and appropriate adjustment of sensing vectors. It is prudent to note that 3 patients (33%) in our cohort experienced T‐wave oversensing, which required vector adjustment. Remote monitoring and consistent follow‐up are critical in this population to capture oversensing early and intervene when necessary for development of T‐wave oversensing. Assessment of sensing with positional variation in all 3 vectors might also be of benefit when determining optimal programming.

Our data indicate that it is reasonable to maintain SICD in young patients with obstructive HCM who have undergone myectomy given the low rates of complications related to T‐wave oversensing and the clear long‐term benefits of avoiding transvenous systems. When deciding to maintain SICD therapy in this unique population, close monitoring and early intervention are critical to lower the risk of T‐wave oversensing and inappropriate shocks.

None.

None.

This article was sent to Kevin F. Kwaku, MD, PhD, Associate Editor, for review by expert referees, editorial decision, and final disposition.

For Sources of Funding and Disclosures, see page 3.

皮下植入式心脏复律除颤器（SICD）可有效预防肥厚型心肌病（HCM）患者的心源性猝死。¹ SICD 可用于符合条件且无起搏指征的患者，以避免与血管内导线放置相关的潜在并发症。进行植入前心电图筛查以评估 QRS 波和 T 波传感，以降低不当电击的风险。尽管存在明显的左心室肥厚和复极异常，但通过适当的筛查，可以最大限度地减少 HCM 患者的过度感觉。左束支传导阻滞 (LBBB) 患者常常无法进行植入前筛查。²因此，接受过间隔肌切除术并出现医源性传导异常的 HCM 患者通常不适合 SICD 植入。同样，对于最终可能需要间隔肌切除术的阻塞性 HCM 患者，植入 SICD 可能会犹豫不决。在这方面，我们追踪了一组患有 HCM 和医源性 LBBB 和 SICD 的患者。这些患者中的大多数在已经进行了 SICD 植入后接受了肌切除术，而其他患者尽管在肌切除术后出现了 LBBB，但仍进行了 SICD 筛查。在该人群中维持 SICD 相关的潜在风险仍不确定。^{3 , 4}因此，我们认为现在是时候描述我们的经验，以帮助指导预防这些患者过度感知和不适当电击的策略。

这项研究得到了塔夫茨健康科学机构审查委员会的批准，不需要知情同意。支持本研究结果的数据可根据合理要求提供。我们描述了 9 名患有 HCM 和 SICD 并接受间隔肌切除术的患者（图 [A]）。其中 8 名患者为男性，肌切除时的平均±标准差年龄为 42±14 岁。 SICD 于 2014 年至 2021 年间植入，平均随访时间为 44.1±29 个月。所有患者均接受双区编程，其中包括条件区（平均 210±12 bpm）和心室颤动区（平均 235±12 bpm）。在第二代和第三代 SICD 中启用了 SMART 通过滤波器（9 名患者中的 7 名）。其中 7 名患者 (78%) 在肌切除术前植入了 SICD。从SICD植入到肌切除术的平均时间为20.7±13.6个月。所有患者均成功进行了 SICD 植入前筛查，其中 2 名患者使用自动筛查工具，7 名患者在使用自动化工具之前进行了手动心电图筛查。一名患者在肌切除术前因心室颤动接受了适当的电击。

A，7 名患者在 SICD 后接受了肌切除术。其中两人拥有 TWOS 和 1 IAS。矢量改变后没有记录任何事件。两名患者在肌切除术后接受了 SICD。其中一个有两个。矢量改变后没有记录任何事件。一名在肌切除术后植入 SICD 的患者的电图。A，植入后 4 个月带有 TWOS 的 SICD 电图。B，感测矢量变化后分辨率为 TWOS 的 SICD 电图。 IAS 表示不适当的震动； LBBB，左束支传导阻滞； SICD，皮下植入式心脏复律除颤器； TWOS，T 波超感。

肌切除术后，所有患者均出现 LBBB，QRS 持续时间在 133 至 166 毫秒之间（平均 146±9 毫秒），随后对所有患者进行形态学更新和必要时传感向量调整的询问。 3 名患者在肌切除术后维持了主要向量，7 名患者中有 4 名的传感向量发生了变化：2 名患者从备用向量重新编程为主要向量，1 名患者从主要向量重新编程为次要向量，1 名患者从主要向量重新编程为备用向量。值得注意的是，由于电极相对于胸骨切开术的位置，从初级重新编程到次级的患者需要在手术期间操作电极。在 2 名患者中观察到 T 波过度敏感，其中 1 名患者在肌切除术后 4 个月下蹲时受到 2 次不适当的电击时出现 R 波振幅下降。随后，传感矢量从主要变为备用，在过去 7 年里没有出现进一步的过度传感或不适当的冲击。迄今为止，还没有患者需要将 SICD 外植体转换为经静脉系统。

其余 2 名患者在肌切除后接受 SICD 植入，两人在植入前均使用手动筛查工具筛查正常。两名患者都没有经历过适当或不适当的电击。一名患者被发现在主要向量中存在 T 波过度感知，并在过去 5 年里接受了向量改变以交替没有过度感知（图 [B]）。由于电池正常耗尽，他最近提出更换 SICD 发电机。有趣的是，这为我们提供了使用外部自动程序员筛选工具重新筛选他的机会，在此期间他未能通过所有 3 个向量的筛选（心电图电极放置在他的设备和皮下电极上方）。尽管如此，考虑到在将他编程到替代向量中之后感测是合适的，执行了生成器改变并且他继续进行SICD植入而没有进一步的事件。

我们的经验描述了发生医源性 LBBB 的患者在肌切除术后进行的最大规模的 SICD 系列。之前的两份病例报告引起了对这一独特患者亚群使用 SICD 的担忧。在 1 例病例中，肌切除术后 T 波过度感应导致不适当的电击和随后感应矢量的变化。³第二个病例是一名儿科患者，由于任何传感载体不适合随后植入经静脉系统，因此需要在肌切除术后取出 SICD。⁴相反，我们的经验表明，HCM 患者因间隔肌切除术出现传导异常后维持 SICD 可能是可行的。肌切除术后，询问应包括形态模板的更新和传感向量的适当调整。值得注意的是，我们队列中的 3 名患者 (33%) 经历了 T 波过度感知，这需要矢量调整。远程监测和一致的随访对于该人群尽早捕获过度感知并在必要时对 T 波过度感知进行干预至关重要。在确定最佳编程时，评估所有 3 个向量中位置变化的传感也可能有益。

我们的数据表明，考虑到与 T 波过度敏感相关的并发症发生率较低以及避免经静脉系统的明显长期益处，对于接受肌切除术的年轻阻塞性 HCM 患者维持 SICD 是合理的。当决定在这一独特人群中维持 SICD 治疗时，密切监测和早期干预对于降低 T 波过度感应和不适当电击的风险至关重要。

没有任何。

没有任何。

本文已发送给副主编 Kevin F. Kwaku，医学博士、博士，供专家审稿人审阅、编辑决定和最终处理。

有关资金来源和披露信息，请参阅第 3 页。