The results of studies evaluating the prognostic impact of LBBB on all-cause mortality in subjects without known CV disease are also somewhat conflicting (Haataja et al., 2015 Imanishi et al., 2006 Schneider, Thomas, Kreger, McNamara, & Kannel, 1979), and even the standard electrocardiographic (ECG) criteria for LBBB have been challenged (Strauss, Selvester, & Wagner, 2011). Some authors showed that RBBB was associated with increased all-cause mortality, while other investigators found no effect on outcome (Bussink et al., 2013 Haataja et al., 2015). In subjects with IVCDs without other evidence of cardiac disease (isolated bundle branch block), published reports show conflicting results. Both right (RBBB) and left bundle branch blocks (LBBB) are associated with adverse outcome in subjects with overt cardiovascular disease (CV Wang et al., 2008 Zhang et al., 2012). The clinical significance of various intraventricular conduction delays (IVCD) depends on the type of the conduction disorder and on the studied patient population. The prognostic impact of LBBB and NSIVCD was affected by the definition of the conduction disorder. Other IVCDs had no significant impact on prognosis. In a population study with long-term follow-up, NSIVCD and Minnesota definition of LBBB were independently associated with CV mortality. The presence of R-R’ pattern was not associated with any adverse outcome. While right bundle branch block, left anterior fascicular block and incomplete bundle branch blocks were associated with seemingly higher mortality, this was no longer the case after adjustment for age and sex. Subjects with NSIVCD were associated with twofold to threefold increase in CV mortality depending on the definition. After controlling for known clinical risk factors, the hazard ratio for CV death, compared with individuals without IVCD, was 1.55 for the Minnesota definition of LBBB (95% confidence interval 1.04–2.31, p = .032) and 1.27 (95% confidence interval 0.80–2.02, p = .308) for the Strauss’ definition of LBBB. Resultsĭuring 16.5 years’ follow-up, 1,309 of the 6,299 subjects (20.8%) died and of these 655 (10.4%) were cardiovascular (CV) deaths. For left bundle branch block (LBBB) and non-specific IVCD (NSIVCD), two different definitions were used. We studied long-term prognostic impact and the association with comorbidities of eight IVCDs in a random sample of 6,299 Finnish subjects (2,857 men and 3,442 women, mean age 52.8, SD 14.9 years) aged 30 or over who participated in the health examination including 12-lead ECG. Previous population studies have presented conflicting results regarding the prognostic impact of intraventricular conduction delays (IVCD).
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