RESUMO
Myotonic dystrophy type 2 (DM2) is caused by expansion of a (CCTG)n repeat in the cellular retroviral nucleic acid-binding protein (CNBP) gene. The sequence of the repeat is most commonly interrupted and is stably inherited in the general population. Although expanded alleles, premutation range and, in rare cases, also non-disease associated alleles containing uninterrupted CCTG tracts have been described, the threshold between these categories is poorly characterised. Here, we describe four families with members reporting neuromuscular complaints, in whom we identified altogether nine ambiguous CNBP alleles containing uninterrupted CCTG repeats in the range between 32 and 42 repeats. While these grey-zone alleles are most likely not pathogenic themselves, since other pathogenic mutations were identified and particular family structures did not support their pathogenic role, they were found to be unstable during intergenerational transmission. On the other hand, there was no observable general microsatellite instability in the genome of the carriers of these alleles. Our results further refine the division of CNBP CCTG repeat alleles into two major groups, i.e., interrupted and uninterrupted alleles. Both interrupted and uninterrupted alleles with up to approximately 30 CCTG repeats were shown to be generally stable during intergenerational transmission, while intergenerational as well as somatic instability seems to gradually increase in uninterrupted alleles with tract length growing above this threshold.
RESUMO
BACKGROUND: Data are scarce regarding left atrial (LA) adaptation to regular physical exercise. The aim of this study was to examine left ventricular (LV) and also LA morphologic and functional remodeling in elite athletes using three-dimensional (3D) echocardiography. METHODS: In this retrospective analysis, the study group consisted of 138 elite athletes (mean age, 20 ± 4 years; 62% men) and 50 sedentary control subjects. Electrocardiographically gated full-volume 3D data sets were obtained for offline analysis using dedicated software for 3D LA and LV measurements. Body surface area-indexed LA maximal volume (LAVmax) and LV end-diastolic volume were determined. LA total emptying fraction, LA passive and LA active emptying fraction, and LV global longitudinal strain were also calculated. Athletes also underwent cardiopulmonary exercise testing to determine peak oxygen uptake. RESULTS: Athletes demonstrated higher 3D LAVmax (32 ± 6 vs 26 ± 8 mL/m2) and indexed LV end-diastolic volume (85 ± 12 vs 62 ± 10 mL/m2) compared with control subjects (P < .001 for both). Functional measures of the left ventricle and left atrium, such as the absolute value of 3D LV global longitudinal strain (19 ± 2% vs 22 ± 2%), LA total emptying fraction (58 ± 6% vs 64 ± 6%), and active emptying fraction (24 ± 10% vs 32 ± 10%) were lower in athletes (P < .001 for all). Male athletes had higher indexed LV end-diastolic volume compared with female athletes (89 ± 13 vs 80 ± 8 mL/m2, P < .001), but LAVmax did not differ between genders (32 ± 6 vs 33 ± 5 mL/m2, P = .18). Besides heart rate, gender, and body surface area, 3D LAVmax, LV global longitudinal strain, and LA passive emptying fraction were independent predictors of peak oxygen uptake. CONCLUSIONS: Regular physical exercise results in marked LA and LV remodeling with considerable gender differences as explored by 3D echocardiography. In contrast with various cardiovascular diseases, more pronounced LA dilation and lower resting functional measures are associated with better exercise performance.