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    • The functional analysis of this V

    2019-04-30

    The functional analysis of this V1764fsX1786 mutation is shown in Fig. 3B; no current was observed, indicating severe loss-of-function. Although we did not investigate the mechanisms of this complete reduction in Na+ current in this mutation, Herfst et al [19]. reported a similar frameshift mutation of SCN5A (5280delG, A1711fsX1786) in a large cardiac conduction defect family, demonstrating that the A1711fsX1786 mutation results in the translation into non-function channel proteins that fail to reach the plasma membrane. Furthermore, Meregalli et al. showed that Na+ current reduction by frameshift or nonsense mutations is predicted to be a complete reduction of peak Na+ current associated with the severity of conduction slowing such as longer PR interval and more symptoms [20]. However, disease severity among mutation carriers is highly variable, and the sodium channel subunit β4 (SCN4B) may be one of the potential genetic modifiers of conduction and cardiac sodium channel disease [21]. Therefore, phenotype manifestation in the loss-of-function sodium channel mutations could interact with many factors such as age, sex, and other modifing genes and proteins. A further genetic study of patients or family members is important for diagnosis and risk stratification for conduction slowing leading to sudden cardiac death.
    Conclusion A significant phenotypic overlap was found between IVF and PCCD/Brugada syndrome in 2 probands with the V1764fsX1786, loss-of-function frameshift mutation of the cardiac Na+ channel gene SCN5A.
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    Conflict of interest
    Introduction The transseptal left atrial (LA) approach is a fundamental method for LA catheter ablation [1,2]. ST-segment elevation on electrocardiography (ECG) associated with transseptal puncture has been recognized as a rare complication [3–11]. Here, we describe a case of ventricular fibrillation (VF) following ampicillin sodium and ST-segment elevation shortly after transseptal puncture but before the radiofrequency energy application. Additionally, we reviewed the literature on ST-segment elevation associated with transseptal puncture.
    Discussion To clarify the cause of this rare complication, we must consider several mechanisms. Air or a thrombus coronary embolism should be considered as the etiology of ST-segment elevation and VF. However, we handled the sheaths carefully, especially after transseptal puncture, and we irrigated them continuously with heparinized saline as detailed in earlier reports [4,5,8]. Immediately after the intracoronary injection of ISDN, coronary angiography during ST-segment elevation revealed no significant stenosis, air embolism, or thromboembolism in the coronary arteries. This supports the fact that the etiology of ST-segment elevation was not caused by a thrombus coronary embolism. Only 1 case report of thromboembolism and ST-segment elevation during LA catheter ablation has been published [3]. Coronary angiography in this case revealed subtotal occlusion of the coronary artery irrespective of intravenous nitrate administration. In addition, normalization of the ST-segment elevation was observed after a few hours. On the other hand, in earlier reports of coronary vasospasms during LA catheter ablation, the ST-segment elevation resolved within 30min [4–8,10,11]. In our case, complete resolution of the ECG changes was confirmed after 6min. It is impossible to deny the possibility of transient air embolism-induced coronary vasospasm in our patient. Natale et al. observed a potentially life-threatening ST-segment elevation during pulmonary vein isolation using a through-the-balloon circumferential ultrasound ablation system in a catheter feasibility trial [11]. The authors attributed this effect to a coronary vasospasm triggered by an air embolism. This condition resolved spontaneously within 1min. Most coronary air embolisms induce ST-segment elevation in the right coronary artery because the origin of the right coronary artery is located more anteriorly to the heart than that of the left coronary artery. Indeed, in 14 of the 16 patients (87.5%) including our patient, the ST-segment elevation was confirmed in the inferior leads (Table 2).