Cardioversor-desfibrilador na prevenção primária de morte súbita: para todos ou para poucos?

Abstract

The implantable cardioverter-defibrillators (ICD) have been used for more than two decades to prevent sudden death. Initially recommended for secondary prevention, currently their most common indication is the primary prevention.A recent US report showed that, of the 108,341 implants carried in 2006, 85,823 (79.2%) were for primary prevention and only 22,518 (20.8%) were for secondary prevention 1 . Several clinical trials have sought to define which patients ought to have this form of treatment. The most recent and largest of these trials is the "Sudden Cardiac Death in Heart Failure" (SCD-Heft) 2 , which followed 2,521 patients with CHF Functional Class II-III and EF <35% in 3 groups (placebo, amiodarone and ICD implant) for a mean follow-up of 45.5 months. This study showed a decrease in the total mortality of the group with ICD, with 23% decrease in the relative risk in the ICD group and no benefit with amiodarone use.Considering that these clinical trials were carried out basically in developed countries, in an environment that is different from the Brazilian one, the applicability of these data is frequently questioned. The present study 3 sought to validate the results for the Brazilian population by comparing the patients from the SCD-Heft to those that met the inclusion criteria of the SCD-Heft and were from a Heart Failure Outpatient Clinic of a hospital in our country. The comparison between the groups showed small differences: the percentage of ischemic patients is slightly higher (63 vs. 53%, p=0.05) and the use of digoxin is lower among the patients of the present study (35 vs. 70%; p<0.001). Regarding the digoxin, no alterations in mortality are expected with its use, which makes this possible confounding factor less important. The slightly higher percentage of ischemic patients might have significance in terms of mortality, as these patients usually present higher rates than the non-ischemic ones; however, that was not observed.The most important data from the point of view of alteration in mortality, such as ejection fraction and the use of beta-blockers and ACE inhibitors, are similar between the two studies. In the SCD-Heft, the benefit observed after the ICD implant occurred exclusively in patients with NYHA Functional Class II, which represented 70% of the total. This percentage was 67% in the present study, supporting the similarity between the populations. The conclusion that can be reached is that patients followed at the CHF outpatient clinic in our country are similar to the randomized ones in the SCD-Heft, indicating that the results of this clinical trial can be applied to our country.However, another much discussed issue regarding the implant of the ICD in our country is the cost-effectiveness. The authors of the present study suggest that this therapy is not regularly used due to the economic impact that it would generate in our health system. This discussion is not a recent one and it is also present in developed countries [4][5][6]