Abstract 3601: Atrial Fibrillation Develops more Frequently in Patients with Hypertrophic Cardiomyopathy with Mutations of Troponin Thin Filament Genes
Background: Atrial fibrillation (AF) is one of the major complications such as systemic embolization and heart failure seen in patients with hypertrophic cardiomyopathy (HCM). However, whether the age of appearance and frequency of AF depends on genotype remains unclear. Objectives: To compare the age of appearance and frequency of AF in HCM patients with different genotypes.
Method: Gene analyses of 345 consecutive and unrelated probands with HCM were performed and disease-causing genes were determined in 53 probands. The study population consisted of 239 subjects, including these probands and their family members. AF included chronic AF and paroxysmal AF which continued for more than 24 hours or required intervention such as cardioversion. The onset of AF was determined by the first ECG evidence retrospectively. Left atrial diameter and left ventricular fractional shortening were measured by echocardiogram. Results: AF was found in 20 individuals of 145 carriers (14%), while in 1 of 94 non-carriers (1%) (P=0.003), although there was no statistical difference in left atrial diameter and fractional shortening in carriers and non-carriers. Kaplan-Meier analysis revealed the onset of AF was earlier in subjects with mutations in the cardiac troponin T and troponin I genes than in those with mutations in the beta-myosin heavy chain and cardiac myosin-binding protein C genes (P<0.05). Left atrial diameter and farctional shortening were significantly associated with the onset of AF (p=0.011, 0.037, respectively), and the former was the most powerful determinant of AF. Left atrial diameter of the subjects with thin filament gene mutation increased with age more rapidly than those with thick filament gene mutation (0.26, 0.09 mm/year,respectively).
Conclusions: These results demonstrate that (1) AF is frequently found even in genotyped HCM, (2) the onset of AF with mutations of thin filaments is earlier than those of other components of the sarcomere. and that (3) impairment of the left atrium with mutations of thin filaments develops earlier. We suggest that detection of gene mutations is useful for predicting of AF in HCM.