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.