ABC | Volume 110, Nº6, June 2018

Original Article Reis et al Hypertrophic Cardiomyopathy Arq Bras Cardiol. 2018; 110(6):524-531 Table 1 – Major characteristics of the population Personal antecedents Arterial hypertension 74 (70.5%) Atrial fibrillation 34 (32.4%) Family history of sudden cardiac death 18 (17.1%) Type 2 diabetes mellitus 16 (15.2%) Previous syncope 14 (13.3%) Previous coronary artery disease 10 (9.4%) 12-lead electrocardiogram Criteria of LVH 69 (65.7%) Left anterior hemiblock 25 (23.8%) First-degree AVB 16 (15.2%) Complete right bundle-branch block 7 (6.7%) Complete left bundle-branch block 5 (4.8%) Transthoracic echocardiogram Septal HCM 72 (68.5%) Concentric HCM 17 (16.1%) Apical HCM 15 (14.3%) Obstructive HCM 43 (40.9%) LVEF ≤ 40% 4 (3.8%) Mitral regurgitation - Mild 55 (52.4%) - Moderate 16 (15.2%) - Severe 8 (7.6%) Exercise test Hypotensive response to exertion 4 (3.8%) Cardiac magnetic resonance LA area, cm 2 43.6 ± 69.2 LV mass, g 168.2 ± 58.9 Maximal thickness measured, mm 18.2 ± 5.7 LVEF, % 64.8 ± 11.8 Late enhancement 34 (32.1%) LVH: left ventricular hypertrophy; AVB: atrioventricular block; HCM: hypertrophic cardiomyopathy; LVEF: left ventricular ejection fraction; LA: left atrial; LV: left ventricular. Screening for sarcomere protein gene mutation ( MYL2 and MYL3 =myosin light chain 2 and 3; MYBPC3 =myosin-binding protein C; MYH7 = myosin heavy chain 7; TNNI3 = cardiac troponin I; TNNT2 = cardiac troponin T; TPM1 = tropomyosin alpha-1 chain) was conducted in 83 patients (79.0%), and screening for Anderson-Fabry disease, in 76 patients (72.4%). The screening for Anderson-Fabry disease in men was based on dried blood spot (DBS) testing to assess galactosidase A (GLA) activity. When GLA activity was reduced (<5%), a 10-mL blood sample was collected in an EDTA tube for further GLA gene sequencing at a medical genetic center. In women, GLA gene sequencing analysis was performed in an external laboratory to identify mutations. 17 One patient was diagnosed with that disease, being excluded from the study. Statistical analysis The numeric variables were expressed as means and standard deviations, and the categorical variables, as absolute and relative frequencies. Regarding the recommendations for ICD implantation in primary prevention, the comparison between the two guidelines was performed by use of the McNemar test. On the first analysis, we assumed that the 2014 ESC classification IIb does not usually recommend ICD implantation, therefore, that classification was grouped together with the recommendation level III. The potency of that test is 99.9%, considering: the significance level of 5%; sample size of 105; the 0.001 proportion of patients classified as III according to the 2011 guideline and as IIa according to the 2014 guideline; and the 0.28 proportion of patients classified as IIa according to the 2011 guideline and as IIb/III according to the 2014 guideline. Later, four groups of patients were defined as follows: patients classified as III according to both 2011 and 2014 guidelines; patients classified as IIa according to the 2011 guideline and as III according to the 2014 guideline; patients classified as IIa according to the 2011 guideline and as IIb according to the 2014 guideline; and patients classified as IIa according to both 2011 and 2014 guidelines. Because one of the assumptions to apply the chi-square test with asymptotic distribution was not met, those groups were compared regarding the percentage of ICD implantation by use of the exact chi-square test. It is worth noting that, given the size of the sample, its power was calculated, ensuring that the number of patients was sufficient to draw conclusions. The statistical analysis was performed by using the SPSS software, version 19.0.0.2®. The tests performed were bilateral, and the significance level of 5% (p < 0.05) was adopted. Results The study sample comprised 105 patients, 53% of whom were of the female sex, the mean age at the time of diagnosis being 58 ± 18 years. Table 1 shows the major characteristics of the population. The functional capacity on the initial assessment was as follows: 45 (42.8%) patients were asymptomatic (NYHA class I), 40 (38.1%) had mild symptoms (NYHA class II), and 9 (8.6%) had severe symptoms (NYHA classes III and IV). Obstruction of the LV outflow tract was present in approximately 40.9% of the patients, resulting in a gradient of 36 ± 36 mmHg. The echocardiographic measures were as follows: interventricular septum thickness, 17 ± 5 mm; posterior wall thickness, 11 ± 3 mm; left atrial diameter, 43 ± 7 mm. Table 1 shows the results of the exercise test and major continuous variables assessed on CMRI. The screening for mutations for HCMwas performed in 83 (79.0%) patients, 28 of whom (26.7%) had one mutation as follows: the MYBPC3 gene mutation in 20 patients (71.4%); the TNNT2 gene mutation in 3 (10.7%); the MYH7 gene mutation in 3 (10.7%); and the TPM1 gene mutation in 2 (7.1%) patients. 526