Primary prevention of sudden cardiac death in a low-risk child with familial hypertrophic cardiomyopathy: the role of cardiac magnetic resonance imaging

Abstract

Sirs: The incidence of hypertrophic cardiomyopathy (HCM) is 0.2 %, and this condition is considered the most common genetic cardiovascular disease. In addition, HCM is one of the most common causes of sudden cardiac death (SCD) in young people [1]. An implantable cardioverter defibrillator (ICD) is a highly effective device for inhibiting ventricular tachyarrhythmias. It is generally agreed that the indications for an ICD strongly support the secondary prevention of SCD [2]. However, the indications for primary preventive ICD placement for SCD remain controversial. Recently, it has been shown that late gadolinium enhancement magnetic resonance imaging (LGE-MRI) can be used to evaluate myocardial fibrosis as an arrhythmic substrate [3, 4]. Here, we report a familial case of HCM in which we decided to place an ICD as primary prevention for SCD based on the LGE-MRI findings. The cases described are two brothers whose father and grandmother were diagnosed with HCM, and the elder brother of the father had a sudden death. Gene analysis was carried out in the father and the two brothers described here. An Ala63Val mutation in exon 2 of TPM1 gene, which encodes alpha tropomyosin, was found (Fig. 1a). The eldest brother in our two cases was 18 years old. He was diagnosed with HCM following medical screening at age 13. The interventricular septum diameter (IVSd) on echocardiography was 18.2 mm (Z-score was 8.5), which is far from the SCD risk criteria (over 30 mm) at age 18. LGE-MRI demonstrated diffuse contrast enhancement in the left ventricular myocardium. The extent of LGE was 8 % of the LV mass using previously reported methods [1] (Fig. 1b). The patient had been managed with mild limitation of physical activity. At the age of 18, he had syncope due to ventricular tachycardia (Fig. 1c) and was successfully resuscitated without any complications. Then, an ICD was implanted for secondary prevention of SCD. The youngest brother of the above-mentioned case was also diagnosed with HCM following medical screening at age 6. He has been managed by mild mobility limitation and treated by beta-blockers because a left ventricular outflow tract obstruction was detected by echocardiography. Though the extent of myocardial fibrosis using LGE-MRI was only 1 % of the LV mass at age 10, it markedly progressed to 16 % in 2 years (Fig. 1d). In addition, LGEMRI demonstrated a diffuse pattern of enhancement, similar to that observed in the elder brother. Because the presence of LGE was seen more strongly in the younger brother than in the elder brother, the younger brother was scheduled for the placement of a prophylactic ICD. The selection of patients for the primary prevention of SCD with an ICD has been predicated on the assessment of well-known five key risk factors, which were reported previously [2]. Recently, ACCF/AHA guidelines indicated primary prevention with the ICD a class IIa indication, based on the presence of one or more conventional key risk factors [5]. However, it is difficult to determine whether our case represents a form of primary prevention of SCD with an ICD because it was unclear whether the cause of sudden death in a family member was related to hypertrophic cardiomyopathy. In addition, there was no case of sudden death in a first-degree relative [2]. Recently, myocardial fibrosis detected by LGE-MRI was reported as a candidate for a new risk factor that may be able to predict SCD. Green et al. [6] mentioned that H. Yamazawa (&) A. Takeda K. Takei T. Furukawa Department of Pediatrics, Hokkaido University School of Medicine, North 15 West 7, Kitaku, Sapporo, Hokkaido 060-8638, Japan e-mail: h-yamazawa@umin.org