Evaluation of mortality in bundle branch block patients from an electronic cohort: Clinical Outcomes in Digital Electrocardiography (CODE) study☆
Introduction
Bundle branch block has been associated with worse prognosis in cardiac disease, especially in heart failure [1]. Left bundle branch block (LBBB) is a known predictor of cardiac events in coronary heart disease [2], heart failure [3] and also in general population [4,5]. However, there are controversial data regarding right bundle branch block (RBBB), considered to be benign in asymptomatic healthy individuals [6]. Although, one study conducted in the general population showed that RBBB was associated with higher risk in all-cause and cardiovascular mortality [7]. For coronary heart disease and heart failure, the prognostic meaning of RBBB also has conflicted findings in the literature [5,8].
Most previous findings came from epidemiological studies or case series. More recently, large databases of digital electrocardiograms (ECG) were linked to mortality databases, what was called an electronic cohort. Big data provided from electronic cohorts with a large amount of information have more reliable and applicable results to the general population [9]. Our aim was to evaluate the overall and cardiovascular mortality in bundle branch block patients from a large electronic cohort composed by primary care patients.
Section snippets
Methods
We conducted an observational retrospective study using database of digital ECGs from the Telehealth Network of Minas Gerais (TNMG) [10]. This public Brazilian telehealth system has performed >4 million ECGs since its inception, in 2006, and is responsible for the ECG report of >900 municipalities in Brazil.
All ECGs performed by the TNMG from patients of at least 16 years-old from 2010 to 2017 were assessed. The majority of patients (79%) underwent routine ECG. Exams without valid tracings or
Results
From a dataset of 1,773,689 patients, 1,558,421(87.8%) primary care patients over 16 years old underwent a valid ECG recording during 2010 to 2017. We excluded 17,359(1.0%) patients that didn't have a valid QRS measure from the Glasgow program and 11,091(0.6%) patients from the control group that had QRS equal or above 120 ms and were not RBBB or LBBB. Therefore, 1,529,971(86.2%) were included (median age 52 [Q1:38; Q3:65] years; 40.2% were male). The prevalence of RBBB (2.42%) was higher than
Discussion
Our study showed that the presence of bundle branch block has prognostic significance in a very large population derived from primary care setting. Both RBBB and LBBB were independent risk factors for all-cause mortality. Female sex had increased risk of all-cause deaths in patients with RBBB. LBBB, but not RBBB, was associated with increased risk of cardiovascular mortality.
The prevalence of RBBB and LBBB was significantly higher in this sample than in others studies conducted in the general
Conclusions
LBBB and RBBB increased the risk of all-cause mortality in patients of Brazilian primary care centers. Women with RBBB had higher risk of all-causes deaths than men. LBBB, and not RBBB, was associated with increased risk of cardiovascular mortality.
Acknowledgements
We acknowledge work of the cardiologists from the TNMG, who performed all ECG analyses.
Funding
This study was supported by grants from IATS/CNPq and FAPEMIG, Brazil. A.L.R. was supported in part by CNPq (Bolsa de produtividade em pesquisa, 309073/2011-1) and FAPEMIG (Programa Pesquisador Mineiro, PPM-00161-13). LGSS and MPFF received scholarships from CAPES and CNPq through IATS – Instituto de Avaliação de Tecnologias em Saúde.
Conflict of interest
None declared.
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The authors take responsibility for all aspects of the reliability and freedom from bias of the data presented and their discussed interpretation.