Results
One hundred patients were evaluated for CRT implantation, seven of them were excluded due to a LVEF higher than 35% prior the procedure. Of the remaining 93 patients, Chagas cardiomyopathy was the most prevalent cause of HF with 29 (31.2%) individuals, followed by idiopathic dilated cardiomyopathy with 28 (30.1%) patients. There was no lost of follow-up for the main outcome, with a mean duration of 1,0 (±0.6) year.
Patients upgraded from a right ventricular pacing (upgrade group) were 22 (23.7%), of those, 4 (18.2%) had previously an implantable cardioverter-defibrillator. Baseline demographic characteristics of groups upgrade and de novo are in Table 1. Chagas cardiomyopathy was more prevalent in the upgraded patients, with 16 (72.7%) vs 13 (18.3%), p<0.001. Other demographic, clinical characteristics and medical treatment for heart failure with evidence-based medical therapies were similar in both groups.
Only 6 (6.5%) patients underwent CRT implantation with non-LBBB (induced or spontaneous), five of whom had Chagas disease and a right bundle branch block (RBBB). Among patients with CC, 13 (44.8%) had induced LBBB, 11 (37.9%) had spontaneous LBBB and 5 (17.2%) had a RBBB.
Echocardiographic measurements at baseline and 6 months of follow-up were available in 78 (83.9%) patients. Both groups had an improvement in LVEF after 6 months of implantation, 22.3% (± 7.1) to 27.1% (± 9.5), p < 0.001, for upgrade and 24.4% (± 7.6) to 31.1% (±11.9), p < 0.001, for De novo CRT, but there was no difference of ΔLVEF improvement between the two groups, p = 0.246. Four (4.3%) patients had echocardiographic criteria for super-responder after CRT, 3 (4.2%) in De novo CRT group and 1 (4.5%) in the upgrade group, p = 0.999. No patient underwent heart transplantation during the study period.
There were four in-hospital deaths, all of them directly associated with the procedure and all from the upgraded group. In the follow-up, overall mortality occurred in 28 (30.1%) patients, with more frequent death in upgraded group when compared to De novo CRT implantation, 14 (63.6%) vs 14 (19.7%), p < 0.001 (log rank), figure 1. In the univariate analysis, Chagas cardiomyopathy and upgraded therapy were associated with overall mortality at follow-up, HR: 3.9, CI: 1.8-8,4, p = 0.001 and RR: 4.7, CI: 2.2-9.9, p < 0.001, respectively. In the multivariate model including both variables, and combined therapy with CRT-D, only upgraded therapy remained independently associated with the outcome, adjusted HR: 2.9, CI: 1.2-7,1, p=0.019), Table 2.