ABC | Volume 112, Nº3, March 2019

Original Article Bittencourt et al Myocardial fibrosis in hypertrophic cardiomyopathy Arq Bras Cardiol. 2019; 112(3):281-289 Table 2 – Characteristics of the observational studies involving RMs of SD in HCM Author / year of publication Country N. of patients Age (years) % males Follow-up (months) Severe arrhythmic outcomes Elliott et al. 2006 17 UK ;1988-2002 917 43 60.4 61 54 Elliott et al. 2000 18 UK; 1988-1998 368 37 64.9 43.2 22 Gimeno et al. 2009 13 UK; 1988 – 2004 1380 42 61.8 54 NI Kofflard et al. 2003 19 Netherlands; 1970-1999 225 41 57.7 96 20 Kofflard et al. 1993 20 Netherlands; 1970-1990 113 38 53.09 87.6 9 Maron B et al. 2007 21 Multicentric; 1983-2005 383 41 62.9 44.4 51 Maron M et al. 2003 22 USA and Italy; 1983- 2001 1101 45 59.4 75.6 71 Michaelides et al. 2009 23 Greece; 1999-2001 81 42 70.3 63.6 8 Monserrat et al. 2003 12 UK; 1988-2000 531 39 60.8 70 32 Rubinshtein et al. 2010 24 USA; 2001-2007 424 55 59.1 43 8 Spirito et al. 2009 25 USA and Italy; 1983-2005 1511 46 61.3 67.2 74 Spirito et al. 2000 11 USA and Italy; 1983-1997 480 47 60 78 23 Syska et al. 2010 26 Poland; 1996-2006 78 36.4 47.4 55.2 13 Chan et al. 2014 14 USA and Italy: 2001-2010 1293 46 63 39.6 37 Spirito et al. 2014 27 Multicentric; 1990-2009 653 44.4 70.5 63.6 24 Magnusson et al. 2016 28 Sweden; 1995-2002 237 52 69.2 64.8 77 Klopotowski et al. 2015 29 Poland; 2008-2013 328 45 58.5 37 14 Mahony et al. 2014 30 Multicentric 3675 48 63.9 68.4 198 Debonmaire et al. 2015 31 Netherlands and Belgium 195 52 61 68.4 26 Ismail et al. 2014 32 UK; 2000-2011 711 55 70.4 42 22 O´Hanlon et al. 2010 33 UK; 2000-2006 217 53.2 70.5 37.2 12 RMs: risk markers; SD: sudden death; HCM: hypertrophic cardiomyopathy; UK: United Kingdom; USA: United States of America; NI: Not informed. Obviously, this has several effects, including economic burdening. Thus, knowing how to select the more important RMs is essential. Although primary prevention has been the object of research in several studies in the last decades, attempting to predict which patients with HCM have a higher risk of SD remains challenging. Therefore, systematic reviews and meta-analyses of such a controversial topic becomes important. The presence of the RMs studied here may define the need for ICD placement, considering that it is the only safe and effective tool in preventing SD. 36 Some RMs have been reported to be more relevant, such as family history of SD, which was highlighted in the study by Dimitrow et al., 10 however, its low positive predictive values is a limitation. In the event of syncope, it is only indicative of the risk when unexplained. Thus, all RMs have their limitations. Strategies using the sum of classic RMs were not feasible. In the multicenter registry performed by Maron et al. 8 in patients with HCM who were treated with ICD placement, it was observed that 35% who received an appropriate shock had only 1 RM. These data were reinforced by a recent meta‑analysis of patients with HCM and ICDwho had 1.8 RISK MARKERS for SD on average, with a rate of 3.3% appropriate shocks per year. We also emphasize that the analysis did not include studies that had myocardial fibrosis as an RM. Among the more recently studied markers aiming to establish correlations with an increased risk of SD in HCM, the most important was myocardial fibrosis. The mechanism suggested for this predisposition is that the presence of myocardial fibrosis could be a substrate for ventricular reentry areas. A classic study demonstrated that this finding correlates with the presence of NSVT in the 24-hour Holter monitoring. Shiozaki et al. 39 in a recent national experience with 26 patients with HCM and ICD, assessed myocardial fibrosis by another method, the contrast-enhanced computed tomography, and found a higher rate of appropriate shocks in patients who had a fibrosis mass ≥ 18 g. Most of the studies that evaluated myocardial fibrosis in this population used cardiac MRI, and these were the experiences we analyzed with the focus on outcomes associated with MS. Putting the results into context, this meta-analysis of observational studies reports a statistically significant association between myocardial fibrosis detected on cardiac MRI and outcomes equivalent to SD. Although we have assessed few articles, this is the most important finding in this study, showing the highest RR among all RMs studied with a very reliable CI. And even if the funnel plot has revealed discrete asymmetry suggesting a publication bias for myocardial fibrosis, it is important to note that the small number of articles does not allow one to conclude this assertion. 284