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The challenge of diagnosing hypertrophic cardiomyopathy in patients of African descent
  1. Paolo Spirito1,
  2. Paolo Ferrazzi2
  1. 1Divisione di Cardiologia, Ente Ospedaliero Ospedali Galliera, Genoa, Italy
  2. 2Centro per la Cardiomiopatia Ipertrofica e le Cardiopatie Valvolari, Policlinico di Monza, Monza, Italy
  1. Correspondence to Dr Paolo Spirito, Divisione di Cardiologia, Ente Ospedaliero Ospedali Galliera, Via Volta 8, Genova 16128, Italy; paolo.spirito{at}galliera.it

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Hypertrophic cardiomyopathy (HCM) is the most common, as well as the most investigated, inherited cardiac disease and has been estimated to occur in 1 of every 500 persons, a prevalence based on many studies performed in thousands of subjects of different ethnicity, including minorities such as Native American Indians.1 ,2 Therefore, it is surprising how little is known of the impact of ethnicity on the clinical presentation and natural history of HCM in patients of African descent.3 ,4 A limited access of black patients to tertiary HCM referral institutions may explain their disproportionately low representation in large HCM study populations.3 ,5 This, in turn, translates into a marked paucity of literature on HCM in patients of African descent. A clear measure of this inadequate representation emerges from the contrast in the number of papers on HCM reported by PubMed in black patients compared with other ethnic groups (mainly white patients) in major cardiology journals, including: Circulation (since 1960), the Journal of the American College of Cardiology (since 1983), the American Journal of Cardiology (since 1961) and the European Heart Journal (since 1980). Of a total of 2697 papers on HCM published in these four journals, only 13 (0.5%) mentioned black patients in the title, and the great majority of these 13 papers were focused on black male athletes. It is time that we knew more about HCM in the black community.

The interesting paper by Sheikh et al6 in this issue of Heart compares the clinical presentation of HCM in 163 African/Afro-Caribbean patients (mean age 52 years) and 262 Caucasian patients (mean age 53 years), a welcome article on a seldom addressed issue. In this study, systemic arterial hypertension was twice as common in black compared with white patients (almost 60% vs about 30%). This high incidence of hypertension, a well-known clinical feature and major health problem in black communities,7 can make the diagnosis of HCM more difficult in black patients suspected of being affected, as the increase in left ventricular (LV) wall thickness due to HCM may be erroneously ascribed to systemic hypertension. This difficulty is augmented by the substantially higher LV mass and relative wall thickness in black compared with white patients with similar degrees of arterial hypertension, a well-documented clinical feature.8

In the study by Sheikh et al,6 findings on the phenotypic presentation of HCM were mainly based on echocardiographic measurements, as cardiac magnetic resonance was performed in a relatively small number of patients. At echocardiographic evaluation, mean LV maximal wall thickness, LV cavity dimension and left atrial dimension did not differ in blacks and whites. However, about 30% of black patients showed either apical or concentric LV hypertrophy compared with about 10% of white patients. A higher prevalence of apical hypertrophy in blacks compared with whites with HCM has also been reported in a smaller cohort of African-Americans by Sorensen et al.4 Such morphologic expressions of HCM, associated with a more frequent history of arterial hypertension, make the HCM diagnosis much more challenging in the black community. Of note, LV outflow obstruction in resting conditions, a feature strongly in support of a diagnosis of HCM, was significantly less common in black compared with white patients, that is, 8% versus 21% (p<0.001), a result that would appear to confirm recent observations.4 This finding could raise the doubt that HCM may have been overdiagnosed in some black patients with secondary LV hypertrophy included in the study, despite the rigorous additional clinical features used by Sheikh et al6 to support the diagnosis of HCM in uncertain cases. However, the possibility of an HCM misdiagnosis in some blacks, rather than casting doubt on the results of the study, further underscores the complexity of reaching a proper HCM diagnosis in black patients, as well as the need to know more about the clinical presentation and outcome of HCM in this large ethnic group.

There were no differences between the two study groups with regard to other important features of HCM, such as sudden death risk or genetic abnormalities. The overall sudden death risk profile, assessed either in terms of conventional risk factors or using the European Society of Cardiology risk stratification model, was similar in blacks and whites. About 50% of patients in the two groups underwent genetic screening. An HCM causing mutation was identified in about 55% of black and 50% of white patients, with a myosin-binding protein C gene mutation being identified in the majority of both groups (54% of blacks and 51% of whites). The study also addressed potential differences in the clinical course of HCM in black and white patients. Although no differences were identified in HCM-related deaths in the two study groups during follow-up, the number of events was too low to draw any important inference, with the exception of a possible role of systemic arterial hypertension in increasing the risk of overall cardiovascular events in both black and white patients with HCM.

In conclusion, as shown by Sheikh et al, apical or concentric LV hypertrophy is substantially more common in patients of African descent than Caucasian patients with HCM. This phenotypic expression may make the diagnosis of HCM a challenge in many black patients, particularly in view of the high prevalence of systemic arterial hypertension and secondary LV hypertrophy in this ethnic group. These important difficulties in the diagnosis of HCM in blacks, together with some alarming features of the clinical course of this disease, such as sudden cardiac death in the absence of previous symptoms, demonstrate the pressing need for further investigations that could guarantee a more accurate diagnosis and management of black patients who may be affected by HCM.

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Footnotes

  • Competing interests None declared.

  • Provenance and peer review Commissioned; internally peer reviewed.

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