Hypertrophic cardiomyopathy

Heritability in genetic heart disease: the role of genetic background

Background

Mutations in genes encoding ion channels or sarcomeric proteins are an important cause of hereditary cardiac disease. However, the severity of the resultant disease varies considerably even among those with an identical mutation. Such clinical variation is often thought to be explained largely by differences in genetic background or 'modifier genes'. We aimed to test the prediction that identical genetic backgrounds result in largely similar clinical expression of a cardiac disease causing mutation, by studying the clinical expression of mutations causing cardiac disease in monozygotic twins.

Methods

We compared first available clinical information on 46 monozygotic twin pairs and 59 control pairs that had either a hereditary cardiomyopathy or channelopathy.

Results

Despite limited power of this study, we found significant heritability for corrected QT interval (QTc) in long QT syndrome (LQTS). We could not detect significant heritability for structural traits, but found a significant environmental effect on thickness of the interventricular septum in hypertrophic cardiomyopathy.

Conclusions

Our study confirms previously found robust heritability for electrical traits like QTc in LQTS, and adds information on low or lacking heritability for structural traits in heritable cardiomyopathies. This may steer the search for genetic modifiers in heritable cardiac disease.

Asymmetric septal hypertrophy in childhood. Unreliability of histologic criteria for differentiation of obstructive and nonobstructive forms

Two cases of obstructive asymmetric septal hypertrophy with biventricular outflow obstruction in childhood are presented. Both patients were treated first with propranolol and later by ventriculoseptal myotomy-myectomy. The first patient died two and one-half years following surgery, and the second patient died in the immediate postoperative period. In the first patient the 690 gm. heart had an interventricular septum to posterior left ventricular wall ratio of 1.9, and in the second patient the ratio in the 460 gm. heart was 1.8. In both cases the posterobasal left ventricular free wall was rounded and hypertrophied, as has been reported grossly in obstructive asymmetric septal hypertrophy. However, in both cases, the bizarre disoriented cardiocytes typical of asymmetric septal hypertrophy were present in both ventricular free walls as well as in the interventricular septum, as has been reported in the nonobstructive variety. In these two cases, previously reported morphologic criteria for the differentiation of obstructive and nonobstructive disease are not considered reliable.

Histochemical, ultrastructural and structural changes in primary cardiomyopathy and in cobalt cardiomyopathy

Images

Hypertrophic cardiomyopathy with unusual features in a family

Images

Hypertrophic cardiomyopathy and mitral incompetence

Images