ABC | Volume 110, Nº6, June 2018

Original Article Reis et al Hypertrophic Cardiomyopathy Arq Bras Cardiol. 2018; 110(6):524-531 Complex ventricular dysrhythmia episodes were identified in 25 (23.8%) patients on 24-hour Holter. Regarding primary prevention, according to the 2011 ACCF/AHA recommendations, 38.1% of the patients had indication for ICD implantation (level of evidence class IIa). The device was implanted in 24 (22.9%) patients. It is worth noting that 6 patients refused the device implantation, and 10 patients did not undergo implantation because of their comorbidities. During the 6-year clinical follow-up, 1 patient received appropriate shock due to ventricular fibrillation (risk score for SCD due to HCM 1.71% - ICD usually not considered). In 25 (23.8%) patients, the ICD recorded ventricular tachycardia (VT) episodes and 3 inappropriate shocks. Ten (9.5%) patients died (6 patients due to heart failure, 1 patient due to ventricular fibrillation, and 3 patients due to neoplasm). According to the 2011 ACCF/AHA recommendations, 38.1% of the patients had indication for ICD implantation (level of evidence class IIa), while 61.9% did not (level of evidence class III) – Figure 1. According to the 2014 recommendations, the mean risk score for SCD due to HCM in the study population was 3.1±2.7%. Based on that value, the patients were stratified into three risk categories for ICD implantation: 81 (77.1%) patients had a score < 4% (ICD usually not considered – recommendation level III); 11 (10.5%) had a score between 4% and 6% (ICD can be considered – recommendation level IIb); and 13 (12.4%) had a score >6% (ICD should be considered – recommendation level IIa) – Figure 1. Grouping together the patients classified as 2014 ESC classes IIb and III, 13 (12.4%) patients had recommendation for ICD implantation for primary prevention, while 64 (61.0%) patients did not have that recommendation according to the 2011 and 2014 guidelines. According to the 2011, but not the 2014, guideline, 28 (26.7%) patients had recommendation for ICD implantation. Thus, in 77 (73.3%) patients, the classifications were concordant, but not in 26.7%. The discordant patients were in the same circumstance, that is, according to the 2011 guideline they had indication for ICD implantation for primary prevention, while, according to the 2014 guidelines, ICD implantation would not usually be considered. This is not random, because, of the 28 discordant patients, there were significantly more patients for implantation in 2011 and not in 2014, than vice-versa (p < 0.001 McNemar test). After that analysis, four groups of patients were defined, and, by using the exact chi-square test, the occurrence of dysrhythmic events during clinical follow-up was compared between groups – Figure 2. Regarding the patients classified as recommendation level III according to both guidelines, that is, no indication for ICD implantation, the device was implanted in 3 out of 64 patients. We observed that of the 61 patients who did not undergo ICD implantation, 3 (4.9%) had VT during follow-up. The 3 patients who underwent ICD implantation for primary prevention had no dysrhythmic event. The groups with and without ICD were compared regarding the percentages of events, but no statistical difference was found between them (p = 1.00) – Table 2. Regarding the group classified as level IIa in 2011 but level III in 2014, of 17 patients, 10 did not undergo ICD implantation, while 7 underwent ICD implantation for primary prevention. Of the 10 who did not undergo ICD implantation, 2 (20.0%) had VT. Of those who had an ICD implanted, 3 (42.9%) had ventricular dysrhythmia during follow-up. The groups with and without ICD were compared regarding the percentages of events, but no significant statistical difference was found between them (p = 0.59) – Table 2. In the group classified as level IIa in 2011 and IIb in 2014, despite the need for ICD implantation for primary prevention, the device was implanted in 4, but not in 7 patients. In both groups, all patients had dysrhythmic events (p = 1.00). The ICD implantation seems beneficial, but the sample is small – Table 2. Regarding the patients classified as recommendation level IIa according to both guidelines, that is, indication for ICD implantation for primary prevention, of the total of 13 patients, 3 did not undergo the procedure, while 10 did. Of the 3 patients not undergoing ICD implantation, Figure 1 – Comparison of risk stratification of SCD due to HCM according to the 2011 versus 2014 recommendations. 2011 ACCF/AHA 2014 ESC Recommendation class IIa Recommendation class III Recommendation class III Recommendation class IIa Recommendation class IIb 81.9% 38.1% 12.4% 10.5% 77.1% 527