We would like to compliment Bos et al on their report on the role of a family history of sudden death in hypertrophic cardiomyopathy (HC). As cardiologists around the world still struggle to correctly estimate the risk for sudden death in their patients with hypertrophic cardiomyopathy, researchers continue to provide evidence that established risk factors (RFs) are associated with increased risk for sudden death. This report also shows how difficult it is to translate research results to one’s own patient. For example, we wonder how the investigators would treat an affected relative of 1 of their included patients who does not have any RF except a positive family history of sudden death. Would they implant an internal cardioverter-defibrillator (ICD) in every HC patient or mutation carrier with a positive family history? In our population, this is the case in almost 20% of patients, using a strict definition. In our opinion, the results of this study in HC patients with ICDs implanted for primary prevention cannot be directly translated to HC patients or mutation carrier without ICDs. We were glad to see that Bos et al mentioned some of the limitations associated with this: (1) the fact that their patients had ICDs implanted because they were thought to have a sufficient risk for sudden death, which suggests that they might have other risk modifiers; (2) the fact that the ICD discharge rate probably overestimates the sudden death rate; and (3) the fact that RF evaluation is often incomplete. With regard to this last limitation, we wonder if the number of patients with incomplete risk stratification is overrepresented in the group with appropriate ICD interventions.

In addition, Bos et al concluded that the ICD discharge rate in patients with 1 positive RF was not significantly different from that in patients with >1 positive RF. This conclusion is not directly supported by the presented data. The investigators’ Figure 2 shows no significant difference in ICD discharge rate among 4 groups (1 RF, only positive family history; 1 RF other than positive family history; >1 RF, including positive family history; and >1 RF without positive family history). To provide data to support this conclusion, one should however join the 2 groups with 1 RF and the 2 groups with >1 RF. We would like to know if the difference in ICD discharge rate between these 2 groups (1 RF vs >1 RF) would still be not significant.