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Relation between QT duration and maximal wall thickness in familial hypertrophic cardiomyopathy
X Jouven1, A Hagege, P Charron
1Service de Cardiologie, Hôpital Européen Georges Pompidou, Paris, France. xavier.jouven@hop.egp.ap-hop-paris.fr
Insights
In familial hypertrophic cardiomyopathy, prolonged QT intervals are linked to left ventricular hypertrophy and specific gene mutations. Even without hypertrophy, genetic changes can cause longer QT duration, indicating mutation-specific effects.
Area of Science:
- Cardiology
- Genetics
- Electrophysiology
Background:
- QT abnormalities are observed in left ventricular hypertrophy (LVH) and hypertrophic cardiomyopathy (HCM).
- Understanding the relationship between LVH and QT interval is crucial in familial HCM.
Purpose of the Study:
- To investigate the association between left ventricular hypertrophy and QT interval prolongation.
- To determine the influence of specific gene mutations on QT duration in familial hypertrophic cardiomyopathy.
Main Methods:
- QT interval was measured in 206 genotyped adult subjects with familial hypertrophic cardiomyopathy.
- Subjects were categorized into genetically unaffected controls, affected with LVH (penetrants), and affected without LVH (non-penetrants).
- Families carried mutations in the beta myosin heavy chain (beta-MHC) or cardiac myosin binding protein C (MyBPC) genes.
Main Results:
- Significant QT interval increases (QTmax and QTmin) were observed in non-penetrants and penetrants compared to controls for both MyBPC and beta-MHC groups.
- In the MyBPC group, increased LVH correlated with QT interval prolongation.
- In the beta-MHC group, non-penetrants showed prolonged QTmax without LVH, similar to penetrants with LVH.
Conclusions:
- Genetically affected individuals with familial hypertrophic cardiomyopathy can exhibit prolonged QT duration even without LVH.
- QT interval prolongation is influenced by both the degree of LVH and the specific causative gene mutation.
- This suggests mutation-dependent mechanisms affecting cardiac repolarization in familial hypertrophic cardiomyopathy.
Background:
QT abnormalities have been reported in left ventricular hypertrophy and hypertrophic cardiomyopathy.
Objective:
To determine the relation between left ventricular hypertrophy and increased QT interval in familial hypertrophic cardiomyopathy.
Methods:
The QT interval was measured in 206 genotyped adult subjects with familial hypertrophic cardiomyopathy from 15 unrelated families carrying mutations in the beta myosin heavy chain (beta-MHC) gene (five families, n = 68) or the cardiac myosin binding protein C (MyBPC) gene (10 families, n = 138). Subjects were classified as genetically unaffected (controls, n = 112), affected with left ventricular hypertrophy (penetrants, n = 58), or affected without left ventricular hypertrophy (non-penetrants, n = 36).
Results:
There was a significant increase in QTmax and QTmin from controls to non-penetrants and penetrants for both the MyBPC group (p < or = 0.001 and p < or = 0.001, respectively) and the beta-MHC group (p < or = 0.001 and p < or = 0.001, respectively). In the MyBPC group, the increase in the QT interval could be explained by increased left ventricular hypertrophy. In the beta-MHC group, non-penetrants had a significantly longer QTmax than controls despite the absence of left ventricular hypertrophy, and a similar QT interval to penetrants despite a lesser degree of left ventricular hypertrophy.
Conclusions:
In familial hypertrophic cardiomyopathy, genetically affected subjects without left ventricular hypertrophy may have a prolonged QT duration, which depends not only on the degree of left ventricular hypertrophy, when present, but also on the causative mutation.