CORRESPONDENCE: LETTERS TO THE EDITOR
Reply
Jens Mogensen, MD, PhD* and
William J. McKenna, MD
* Department of Cardiology, Skejby University Hospital, Brendstrupgaardsvej, 8200 Aarhus N, Denmark (Email: jens.mogensen{at}dadlnet.dk).
We thank Dr. Cheng for his interest in our work (1) and appreciate his comments. The prevalence of hypertrophic cardiomyopathy (HCM) appears similar among different racial groups. Population studies comprising more than 16,000 subjects from Japan, China, and the U.S. (Caucasian, African, and native Americans) have established that unexplained left ventricular (LV) wall thickness  15 mm occurs with a prevalence of about 0.2% (range 0.16% to 0.23%) (2–5). Recent genotype-phenotype studies have revealed that the disease expression of HCM is extremely heterogeneous and that many gene carriers present with electrocardiographic (ECG) abnormalities in the absence of LV hypertrophy on echocardiography. It is likely, therefore, that the true prevalence of HCM is well above 0.2% (1). Furthermore, the prevalence of HCM appeared to be similar in each of the screening studies despite considerable age differences in the study populations, which suggests that HCM may develop independent of age. This finding is in contrast to previous assumptions that HCM develops during adolescence and early adulthood. If this was the case, the prevalence would be age-dependent and expected to be high at young ages and low at older ages owing to increased mortality rates associated with HCM. Apparently, the number of individuals dying equals the number of individuals developing the condition at any age, resulting in a "steady-state" and age-independent prevalence of the condition.
The frequency of mutations in the gene for cardiac troponin I (TNNI3) has been reported in six larger studies (6–9). A total of 1,697 HCM patients have been investigated (range: 71 to 748 patients), with an average frequency of TNNI3 mutations of 2.7% (range 0.9% to 4.0%). The studies were conducted in patients in Great Britain, the U.S., France, China, Japan, Korea, and Germany. The modest differences in frequency of mutations are most likely explained by differences in sample sizes of patients and do not appear to be associated with race.
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References
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1. Mogensen J, Murphy RT, Kubo T, et al. Frequency and clinical expression of cardiac troponin I mutations in 748 consecutive families with hypertrophic cardiomyopathy J Am Coll Cardiol 2004;44:2315-2325.[Abstract/Free Full Text]
2. Hada Y, Sakamoto T, Amano K, et al. Prevalence of hypertrophic cardiomyopathy in a population of adult Japanese workers as detected by echocardiographic screening Am J Cardiol 1987;59:183-184.[CrossRef][Web of Science][Medline]
3. Zou Y, Song L, Wang Z, et al. Prevalence of idiopathic hypertrophic cardiomyopathy in Chinaa population-based echocardiographic analysis of 8,080 adults. Am J Med 2004;116:14-18.[CrossRef][Web of Science][Medline]
4. Maron BJ, Gardin JM, Flack JM, et al. Prevalence of hypertrophic cardiomyopathy in a general population of young adults: echocardiographic analysis of 4,111 subjects in the CARDIA study. Coronary Artery Risk Development in (Young) Adults Circulation 1995;92:785-789.[Abstract/Free Full Text]
5. Maron BJ, Spirito P, Roman MJ, et al. Prevalence of hypertrophic cardiomyopathy in a population-based sample of American Indians aged 51 to 77 years (the Strong Heart Study) Am J Cardiol 2004;93:1510-1514.[CrossRef][Web of Science][Medline]
6. Kimura A, Harada H, Park JE, et al. Mutations in the cardiac troponin I gene associated with hypertrophic cardiomyopathy Nat Genet 1997;16:379-382.[CrossRef][Web of Science][Medline]
7. Erdmann J, Daehmlow S, Wischke S, et al. Mutation spectrum in a large cohort of unrelated consecutive patients with hypertrophic cardiomyopathy Clin Genet 2003;64:339-349.[CrossRef][Web of Science][Medline]
8. Van Driest SL, Ellsworth EG, Ommen SR, Tajik AJ, Gersh BJ, Ackerman MJ. Prevalence and spectrum of thin-filament mutations in an outpatient referral population with hypertrophic cardiomyopathy Circulation 2003;108:445-451.[Abstract/Free Full Text]
9. Richard P, Charron P, Carrier L, et al. Hypertrophic cardiomyopathydistribution of disease genes, spectrum of mutations, and implications for a molecular diagnosis strategy. Circulation 2003;107:2227-2232.[Abstract/Free Full Text]
Related Article
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Frequency of Cardiac Troponin I Mutations in Families With Hypertrophic Cardiomyopathy in China
- Tsung O. Cheng
J. Am. Coll. Cardiol. 2005 46: 180-181.
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