Prognostic implications of intraventricular conduction delays in a general population: the Health 2000 Survey

All-cause mortality due to conduction abnormalities in the United States: sex, racial, and geographic variations from 1999 to 2022

BACKGROUND

Mortality related to conduction abnormalities in the US population is not well-documented. Population-based stratification approaches can improve public health policies and targeted strategies.

OBJECTIVE

To evaluate all-cause mortality related to conduction abnormalities in the US population METHODS: The CDC WONDER database was utilized to calculate the Age-Adjusted Mortality Rate (AAMR) per 100,000 individuals above 35 years old related to conduction abnormalities between 1999 and 2022.

RESULTS

A total of 207,861 deaths were attributed to conduction abnormalities throughout the study period with 56,186 of these deaths occurring between 2020 and 2022. All-cause mortality related to conduction abnormalities has increased during the past decade with an exponential growth in 2020-2021 (COVID-19 era; Annual Percent Change (APC) of 16.6% per year). Although the mortality rates decreased in 2022, they remained elevated compared to 2019-2020. Throughout the past two decades, males consistently exhibited higher mortality rates than females, with the rate in 2022 being 1.5 times higher (AAMR 11.4 vs 7.0 per 100,000). Non-Hispanic Black patients experienced a significantly higher mortality rate compared to non-Hispanic White individuals in the study period (AAMR 13.7 vs. 8.6 per 100,000 in 2022). In the past two decades, mortality has been persistently higher in rural and small-medium-sized metro areas than in large metro urban areas.

CONCLUSIONS

Mortality rates related to conduction abnormalities have increased over the past decade, and persistent disparities have been observed. These data suggest that continued innovative outreach approaches and engagement with under-represented populations remain essential.

Association between cardiac conduction block and cardiovascular disease and all-cause mortality: The kailuan study

BACKGROUND

Although bundle branch block and atrioventricular block are recognized to be association with cardiovascular disease (CVD) and mortality, the relationship between cardiac conduction block (CCB) and both CVD and all-cause mortality has yet to be explored.

AIMS

To explore the relationship between CCB and CVD and all-cause mortality.

METHODS AND RESULTS

We included 145,805 subjects (mean age 49.7 years, 81.2% males) from the kailuan study. CCB was diagnosed through a 12‑lead electrocardiograph (ECG). Mortality and CVD events were ascertained through multiple sources, including a municipal social insurance institution, hospital records, death certificates, and regular active follow-ups. After a mean follow-up of 12.5 years, 18,301 cases developed all-cause mortality. After excluding 4443 subjects with CVD presence at baseline, 13,208 cases of CVD occurred among the 141,362 study subjects during follow-up. Compared with non-CCB group, the cumulative incidence of CVD and all-cause mortality for CCB group was 18.38% VS 12.14% and 33.45% VS 14.18%, respectively. The multivariable-adjusted hazard ratios (HRs) with 95% confidence intervals (CIs) with CCB group were 1.25(1.17-1.34) for CVD, and 1.31(1.25-1.38) for all-cause mortality. Additionally, there were generally stronger associations for CCB with all-cause mortality and CVD in younger participants compared with their older counterparts (Ps-interaction <0.001).

CONCLUSION

CCB can increase the risk of CVD and all-cause mortality in the general population. Our findings highlight the importance of strategies for preventing CCB to reduce the risk of CVD and mortality.

Cardiac resynchronization therapy for patients with heart failure and nonspecific intraventricular conduction delay

The efficacy of cardiac resynchronization therapy (CRT) in heart failure patients with left bundle branch block (LBBB) is well established with Class I or IIa recommendation according to 2021 ESC Guidelines on cardiac pacing and CRT, whereas non-LBBB morphology is less recommended. There is insufficient evidence that proves patients with NICD could benefit from CRT. As patients with NICD are characterized by heterogeneity, the effect of CRT on these patients is still controversial. Although the proportion of NICD in the population is lower than that of LBBB patients, it is still worth investigating the effects of CRT on patients with NICD in an era of His-Purkinje conduction system pacing (HPCSP).

Impact of Baseline Right Bundle Branch Block on Outcomes After Pulmonary Vein Isolation in Patients With Atrial Fibrillation

Right bundle branch block (RBBB) is one of the most frequent alterations of the electrocardiogram. Several studies have shown that RBBB is a risk factor of cardiovascular diseases. However, the clinical outcomes after pulmonary vein isolation (PVI) in patients with RBBB remain unclear. We enrolled consecutive atrial fibrillation (AF) patients who underwent PVI from the Osaka Rosai Atrial Fibrillation (ORAF) registry. We excluded patients with other wide QRS morphologies (left bundle branch block, ventricular pacing, and unclassified intraventricular conduction disturbances) and divided them into 2 groups: RBBB (QRS duration ≥120msec) and No-RBBB (QRS duration <120) groups. We compared the incidence of late recurrence of AF and/or atrial tachycardia (AT) (LRAF) between the 2 groups using a propensity score-matched analysis and evaluated the risk of LRAF using Cox regression model. We finally analyzed 671 consecutive AF patients. The RBBB group consisted of 50 patients (7.5%) and the No-RBBB group of 621 patients. Median follow-up duration was 734 [496, 1,049] days. Hypertension and diabetes mellitus were significantly higher in RBBB group than No-RBBB group. Among the 46 matched patients pairs, Kaplan-Meier analysis demonstrated that RBBB group had a significantly greater risk of LRAF than the No-RBBB group (p = 0.046). The Cox regression model revealed significantly higher risks of LRAF (HR, 2.30; 95% CI, 1.00 to 5.33; p=0.044) in RBBB group compared with No-RBBB group. Non-PV AF triggers were significantly higher in RBBB group than No-RBBB group (p = 0.048). In conclusion, RBBB can be an important predictor of LRAF after PVI.

Relation of intraventricular conduction delay to risk of new-onset heart failure and structural heart disease in the general population

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Subjects with high-risk of developing heart failure ought to be identified.

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Non-specific IVCD and LBBB were associated with risk of new-onset heart failure.

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LBBB also carried a risk of novel structural heart disease in 15-year follow-up.

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Their presence should alert clinician even in subjects free of any known heart disease.

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Right bundle branch block and other blocks were not associated with increased risk.

Background

Intraventricular conduction delays (IVCDs) are hallmarks of heart failure (HF) and structural heart disease (SHD) but their prognostic value for HF and SHD is unclear.

Methods

Relation of eight IVCDs and the incidence of first-time HF or SHD was studied in a nationally representative random sample of 6080 Finnish subjects aged ≥ 30 years (mean age 52.1, SD 14.5 years) who participated in the health examination including 12-lead ECG.

Results

During 16.5 years’ follow up, half of the subjects with left bundle branch block (LBBB) and one third of the subjects with non-specific IVCD developed HF. After controlling for known clinical risk factors the hazard ratio (HR) for new-onset HF for LBBB was 3.29 (95% confidence interval 1.93–5.63, P < 0.001) and 3.53 for non-specific IVCD (1.65–7.55, P = 0.001). In corresponding analysis, LBBB predicted SHD with HR 2.60 (1.21–5.62, P = 0.015). Excluding subjects with history of heart disease, including coronary heart disease, did not have impact on results. Right bundle branch block and other IVCDs displayed no relation to endpoints.

Conclusion

LBBB and non-specific IVCD were associated with more than three-fold risk of new-onset HF. Furthermore, LBBB was associated with novel SHD. Their presence should alert clinician even in subjects free from any known heart disease.

Long-term outcome of pre-specified ECG patterns in acute coronary syndrome

BACKGROUND

Long-term outcome of real-life acute coronary syndrome (ACS) patients with selected ECG patterns is not well known.

PURPOSE

To survey the 10-year outcome of pre-specified ECG patterns in ACS patients admitted to a university hospital.

METHODS

A total of 1184 consecutive acute coronary syndrome patients in 2002-2003 were included and followed up for 10 years. The patients were classified into nine pre-specified ECG categories: 1) ST elevation; 2) pathological Q waves without ST elevation; 3) left bundle branch block (LBBB); 4) right bundle branch block (RBBB) 5) left ventricular hypertrophy (LVH) without ST elevation except in leads aVR and/or V₁; 6) global ischemia ECG (ST depression ≥0.5 mm in 6 leads, maximally in leads V_4-5 with inverted T waves and ST elevation ≥0.5 mm in lead aVR); 7) other ST depression and/or T wave inversion; 8) other findings and 9) normal ECG.

RESULTS

Any abnormality in the ECG, especially Q waves, LBBB, LVH and global ischemia, had negative effect on outcome. In age- and gender adjusted Cox regression analysis, pathological Q waves (HR 2.28, 95%CI 1.20-4.32, p = .012), LBBB (HR 3.25, 95%CI 1.65-6.40, p = .001), LVH (HR 2.53, 95%CI 1.29-4.97, p = .007), global ischemia (HR 2.22, 95%CI 1.14-4.31, p = .019) and the combined group of other findings (HR 3.01, 95%CI 1.56-6.09, p = .001) were independently associated with worse outcome.

CONCLUSIONS

During long-term follow-up of ACS patients, LBBB, ECG-LVH, global ischemia, and Q waves were associated with worse outcome than a normal ECG, RBBB, ST elevation or ST depression with or without associated T-wave inversion. LBBB was associated with the highest mortality rates.

Long-term outcome of intraventricular conduction delays in the general population

Background

Previous population studies have presented conflicting results regarding the prognostic impact of intraventricular conduction delays (IVCD).

Methods

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. For left bundle branch block (LBBB) and non‐specific IVCD (NSIVCD), two different definitions were used.

Results

During 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. 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. Subjects with NSIVCD were associated with twofold to threefold increase in CV mortality depending on the definition. 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. The presence of R‐R’ pattern was not associated with any adverse outcome.

Conclusions

In a population study with long‐term follow‐up, NSIVCD and Minnesota definition of LBBB were independently associated with CV mortality. Other IVCDs had no significant impact on prognosis. The prognostic impact of LBBB and NSIVCD was affected by the definition of the conduction disorder.

Nonspecific intraventricular conduction delay is associated with future occurrence of atrial fibrillation in patients with structurally normal heart

BACKGROUND

We aimed to elucidate the long-term prognosis of nonspecific intraventricular conduction delay (NIVCD) in patients with structurally normal heart.

METHODS

We included 107,838 patients (age, 52.1 ± 15.5 years; men, 46.8%) who underwent electrocardiography in outpatient clinics or medical checkup (unmatched cohort). NIVCD was defined as QRS duration ≥110 ms without meeting the criteria for bundle branch block. Patients with structurally normal heart and sinus rhythm were assigned to the NIVCD and normal QRS groups according to propensity score with matching variables of age, sex, hypertension, and diabetes (matched cohort 1), and additional PR interval (matched cohort 2). Baseline characteristics, electrocardiographic parameters, and clinical outcomes were compared in the unmatched cohort and the matched cohort.

RESULTS

In the unmatched cohort, the frequencies of male sex and preexisting atrial fibrillation were significantly higher in the NIVCD group than in the normal QRS group. In matched cohort 1 (n = 690), the NIVCD group exhibited significant slower sinus rate and longer PR interval than the normal QRS group. In matched cohort 2 (n = 598), the cumulative incidence of atrial fibrillation was significantly higher in the NIVCD group than in the normal QRS group during a follow-up period of 8.8 ± 2.9 years. NIVCD significantly increased the risk for AF (hazard ratio, 2.571; 95% confidence interval, 1.074-6.156; p = 0.034).

CONCLUSIONS

It is suggested that NIVCD may be associated with future occurrence of atrial fibrillation in patients with structurally normal heart and sinus rhythm.

Evaluation of mortality in bundle branch block patients from an electronic cohort: Clinical Outcomes in Digital Electrocardiography (CODE) study

BACKGROUND

Left bundle branch block is recognized as a marker of higher risk of death, but the prognostic value of the right bundle branch block in the general population is still controversial. Our aim is to evaluate the risk of overall and cardiovascular mortality in patients with right (RBBB) and left bundle branch block (LBBB) in a large electronic cohort of Brazilian patients.

METHODS

This observational retrospective study was developed with the database of digital ECGs from Telehealth Network of Minas Gerais, Brazil (TNMG). All ECGs performed from 2010 to 2017 in primary care patients over 16 years old were assessed. The electronic cohort was obtained by linking data from ECG exams (name, sex, date of birth, city of residence) and those from national mortality information system, using standard probabilistic linkage methods (FRIL: Fine-grained record linkage software, v.2.1.5, Atlanta, GA). Only the first ECG of each patient was considered. Clinical data were self-reported, and ECGs were interpreted manually by cardiologists and automatically by the Glasgow University Interpreter software. Hazard ratio (HR) for mortality was estimated using Cox regression.

RESULTS

From a dataset of 1,773,689 patients, 1,558,421 primary care patients over 16 years old underwent a valid ECG recording during 2010 to 2017. We excluded 17,359 patients that didn't have a valid QRS measure from the Glasgow program and 11,091 patients from the control group that had QRS equal or above 120 ms and were not RBBB or LBBB. Therefore, 1,529,971 were included (median age 52 [Q1:38; Q3:65] years; 40.2% were male). In a mean follow-up of 3.7 years, the overall mortality rate was 3.34%. RBBB was more frequent (2.42%) than LBBB (1.32%). In multivariate analysis, adjusting for sex, age and comorbidities, both patients with RBBB (HR 1.32; CI 95% 1.27-1.37) and LBBB (HR 1.69; CI 95% 1.62-1.76) had higher risk of overall mortality. Women with RBBB had an increased risk of all-cause death compared to men (p < 0.001). Cardiovascular mortality was higher in patients with LBBB (HR 1.77; CI 95% 1.55-2.01), but not for RBBB.

CONCLUSIONS

Patients with RBBB and LBBB had higher risk of overall mortality. Women with RBBB had more risk of all-cause death than men. LBBB was associated with higher risk of cardiovascular mortality.

Right bundle branch block: Prevalence, incidence, and cardiovascular morbidity and mortality in the general population

Background: Right bundle branch block (RBBB) is among the most common electrocardiographic abnormalities. Objectives: To establish the prevalence and incidence of RBBB in the general population without cardiovascular events (CVE) and whether RBBB increases cardiovascular morbidity and mortality compared with patients with a normal electrocardiogram (ECG). Methods: A historical study of two cohorts including 2981 patients from 29 primary health centres without baseline CVE. Cox (for CVE) and logistic (for cardiovascular factors) regression was used to assess their association with RBBB. Results: Of the patients (58% women; mean age 65.9), 92.2% had a normal ECG, 4.6% incomplete RBBB (iRBBB) and 3.2% complete RBBB (cRBBB). Mean follow-up was five years. Factors associated with appearance of cRBBB were male sex (HR = 3.8; 95%CI: 2.4-6.1) and age (HR = 1.05 per year; 95%CI: 1.03-1.08). In a univariate analysis, cRBBB was associated with an increase in all-cause mortality but only bifascicular block (BFB) was significant after adjusting for confounders. cRBBB tended to increase CVE but the results were not statistically significant. Presence of iRBBB was not associated with adverse outcomes. Patients with iRBBB who progressed to cRBBB showed a higher incidence of heart failure and chronic kidney disease. Conclusion: In this general population cohort with no CV disease, 8% had RBBB, with a higher prevalence among men and elderly patients. Although all-cause mortality and CVE tended to increase in the presence of cRBBB, only BFB showed a statistically significant association with cRBBB. Patients with iRBBB who progressed to cRBBB had a higher incidence of CVE. We detected no effect of iRBBB on morbidity and mortality.

Familial Clustering of Cardiac Conduction Defects and Pacemaker Insertion

BACKGROUND

The etiopathogenesis of electrocardiographic bundle branch and atrioventricular blocks is not fully understood. We investigated familial clustering of cardiac conduction defects and pacemaker insertion in the FHS (Framingham Heart Study). Additionally, we assessed familial clustering of pacemaker insertion in the Danish general population.

METHODS

In FHS, we used multivariable-adjusted logistic regression models to investigate the association of parental atrioventricular block (PR interval, ≥0.2 s), complete bundle branch block (QRS, ≥0.12 s), or pacemaker insertion with the occurrence of cardiac conduction abnormalities in their offspring. The Danish nationwide administrative registries were interrogated to assess the relations of parental pacemaker insertion with offspring pacemaker insertion.

RESULTS

In FHS (n=371 cases with first-degree atrioventricular block, complete bundle branch block, or pacemaker insertion, and 1471 age- and sex-matched controls), individuals with at least 1 affected parent with a conduction defect had a 1.65-fold odds (odds ratio, 95% CI, 1.32-2.07) for manifesting an atrioventricular block and a 1.62-fold odds (95% CI, 1.08-2.42) for developing a complete bundle branch block. If at least 1 parent had any electrocardiographic conduction defect or pacemaker insertion, the offspring had a 1.62-fold odds (95% CI, 1.31-2.00) for experiencing any of these conditions. In Denmark (n=2 824 199 individuals; 5397 incident pacemaker implantations), individuals with at least 1 first-degree relative with history of pacemaker insertion had a multivariable-adjusted 1.68-fold (incidence rate ratio, 95% CI, 1.49-1.89) risk of undergoing a pacemaker insertion. If the affected relative was ≤45 years of age, the incidence rate ratio was markedly increased to 51.0 (95% CI, 32.7-79.9).

CONCLUSIONS

Cardiac conduction blocks and risk for pacemaker insertion cluster within families. A family history of conduction system disturbance or pacemaker insertion should trigger increased awareness of a similar propensity in other family members, especially so when the conduction system disease occurs at a younger age.

Diagnosis of right bundle branch block: a concordance study

BACKGROUND

Right bundle branch block is one of the most common electrocardiographic abnormalities. Most cases of right bundle branch block are detected in asymptomatic patients in primary care, so a correct interpretation of electrocardiograms (ECGs) at this level is necessary. The objective of this research is to determine the degree of concordance in the diagnosis of incomplete and complete right bundle branch block between four primary care researchers and a cardiologist.

METHODS

The research design is a retrospective cohort study of patients over 18 years of ages of patients over 18 years of ages who underwent an ECG for any reason and were diagnosed with right bundle branch block by their physician. The physicians participating, 4 primary care researchers and a cardiologist were specialized in interpreting electrocardiographic records. The diagnosis of incomplete and complete right bundle branch block was recorded and other secondary variables were analysed. In case of diagnostic discordance between the researchers, the ECGs were reviewed by an expert cardiologist, who interpreted them, established the diagnosis and analysed the possible causes for the discrepancy.

RESULTS

We studied 160 patients diagnosed with right bundle branch block by their general practise. The patients had a mean age of 64.8 years and 54% of them were men. The concordance in the diagnosis of incomplete right bundle branch block showed a Fleiss' kappa index (k) of 0.71 among the five researchers and of 0.85 among only the primary care researchers. The k for complete right bundle branch block was 0.93 among the five researchers and 0.96 among only the primary care researchers.

CONCLUSION

The interobserver agreement in the diagnosis of right bundle branch block performed by physicians specialized in ECG interpretation (primary care physicians and a cardiologist) was very good. The variability was greater for the diagnosis of incomplete right bundle branch block.

Cardiac Resynchronization Therapy in Preserved to Mildly Reduced Systolic Function

Cardiac resynchronization therapy has been proven to be clearly beneficial for patients with heart failure, a prolonged QRS duration, and a left ventricular ejection fraction ≤35%. Ejection fraction cutoff, however, is arbitrary and very likely excludes many patients who could benefit from cardiac resynchronization. This article describes the major detrimental effects of left bundle branch block and summarizes the data regarding the potential beneficial effects of cardiac resynchronization in patients with a left ventricular ejection fraction greater than 35%.

Right bundle branch block and cardiovascular morbidity and mortality in healthy patients

The clinical significance of a right bundle branch block (RBBB) in an asymptomatic adult without evidence of cardiovascular disease is controversial. To establish the relationship between the appearance of the RBBB and the increase of cardiovascular morbidity and mortality in healthy patients, we have carried out a literature review of documents available until September 2017 through a systematic search on the Pubmed database, Cochrane library and a manual search of the mentioned literature and related articles. From the 29 articles included in the study sample, eight showed mortality and 16 morbidity outcomes. An increase of risk of death is observed is eight articles and an increase of cardiovascular events is observed in 11 articles. The most recent publications suggest that the appearance of an RBBB in healthy individuals should not be underestimated, thus further studies are needed to analyse the type of follow-up that should be carried out in these patients.

Prognostic Significance and Clinical Utility of Intraventricular Conduction Delays on the Preoperative Electrocardiogram

The prognostic significance of the preoperative electrocardiogram (ECG), particularly intraventricular conduction delays (IVCDs), on postoperative outcomes among patients undergoing noncardiac surgery is uncertain. In a retrospective cohort, we evaluated the risk associated with preoperative IVCDs on in-hospital death and postoperative myocardial infarction (POMI). The 152,479 patients who underwent noncardiac surgery were categorized by preoperative electrocardiographic findings: normal (36.1%), left bundle branch block (LBBB, 1.2%), right bundle branch block (2.9%), nonspecific IVCD (3.3%), and any other ECG abnormality (56.5%). The primary and secondary outcomes were postoperative in-hospital mortality and POMI, respectively. In multivariable-adjusted models, compared with normal ECGs, each electrocardiographic abnormality category was associated with increased risk of postoperative death: LBBB odds ratio (OR) 1.89 (95% confidence interval [CI] 1.35 to 2.65), right bundle branch block OR 1.73 (95% CI 1.33 to 2.24), nonspecific IVCD OR 1.95 (95% CI 1.53 to 2.48), and other abnormal ECG OR 1.94 (95% CI 1.68 to 2.25). ECGs with conduction delays did not confer increased risk of postoperative death compared with other ECG abnormalities. Moreover, receiver operating characteristic analysis of models incorporating demographic and co-morbidity data demonstrated marginal additive benefit of any electrocardiographic data. Risk of POMI was not significantly increased among ECGs with conduction delays compared with both normal and other abnormal ECGs. In conclusion, patients with intraventricular conduction disease, including LBBB, on preoperative ECG are not at greater risk of postoperative in-hospital death or POMI compared with patients with other ECG abnormalities. Furthermore, any preoperative electrocardiographic abnormalities, including intraventricular delays, provide marginal clinical utility beyond demographic and clinical history for predicting postoperative in-hospital death or POMI.

Electrocardiogram QRS duration and associations with telomere length: A cross-sectional analysis in Australian rural diabetic and non-diabetic population

Prolonged electrocardiogram QRS durations are often present in aging populations. Shorter telomere length is considered a biomarker of cellular aging. Decreased telomere length has been associated with coronary artery risk, and ventricular remodeling. However, the association between telomeres and cardiac conduction abnormalities, such as increased QRS duration are not well understood. A retrospective cross-sectional population was obtained from the CSU Diabetes Screening Research Initiative database where 273 participants had both ECG-derived QRS duration and DNA to permit leukocyte telomere length (LTL) determination. Telomere length was determined using the monochrome multiplex quantitative PCR method to measure mean relative LTL. Resting 12-lead electrocardiograms were obtained from each subject using a Welch Allyn PC-Based ECG system. Relative LTL was moderately negatively associated with QRS duration in type 2 diabetes mellitus (T2DM) patients (R²=0.055), compared to controls (R²=0.010). In general linear models with no adjustments a significant interaction between QRS duration and LTL is observed for a combined population of T2DM and non-diabetics. When we compared T2DM to non-diabetics, we found that T2DM increased the effect size for relative LTL on QRS duration in comparison to controls. Hence, for each 0.1 unit of relative LTL attrition, QRS duration in T2DM patients increased by 3.24ms (95% CI, -63.00 to -1.84), compared to 1.65ms in controls (95% CI, -40.44 to 7.40). In summary we have observed an association between LTL in a rural aging mixed population of T2DM and non-diabetes. We have observed an unadjusted association between QRS duration and LTL in T2DM. We noted that the control group demonstrated no such association. This highlights the complexity of T2DM when exploring disease phenotype-telomere interactions.

Cardiovascular outcomes in patients with intraventricular conduction blocks: A sixteen-year follow-up in a state-wide database

BACKGROUND

To assess the adverse clinical effects of left anterior hemiblock alone or in combination with right bundle branch block and of complete left bundle branch block in comparison with isolated right bundle branch block and the relationship of these effects with altered mechanoelectric factors resulting in left ventricular dysfunction.

METHODS

In a 16-year follow-up study using a statewide database, we studied the occurrence of mortal and morbid cardiovascular (CV) events among patients without apparent ischemic heart disease who had left anterior hemiblock (LAHB, n=4273, right bundle branch block (RBBB) with LAHB (BFBB, n=1857) and left bundle branch block (LBBB, n=9484 compared to isolated RBBB (n=25288).

RESULTS

After adjustment for demographics, co-morbidities and insurance, LAHB was associated with a significant excess risk of all-cause death (HR 1.134, 95% CI 1.061-1.213, p=0.0002) and CV death (HR 1.329, 95% CI 1.174-1.501, p<0.0001). BFBB was associated with excess HF (HR 1.190, 95% CI 1.048-1.351, p<0.0071), all-cause death (HR 1.440, 95% CI 1.045-1.252, p=0.0036) and CV death (HR 1.210, 95% CI 1.020-1.436, p<0.0001). LBBB was associated with an excess risk of MR (HR 1.307, 95% CI 1.116-1.530, p<0.0009), HF 1.177, 95% CI1.097-1.263, p<0.0001) and CV death (HR 1.220, 95% CI 1.106-1.345, p<0.0001).

CONCLUSIONS

In patients without apparent ischemic heart disease, the presence of LAHB alone or in combination with RBBB imparts increased risk of CV and all-cause death compared to isolated RBBB. BFBB is also associated with an increased risk of HF.

A Three-Decade Survival Analysis of Intraventricular Conduction Delay in Adults Without Ischemic Heart Disease

BACKGROUND

The prognosis of an incidental finding of intraventricular conduction delay in individuals without ischemic heart disease is debatable. Intraventricular conduction delay presents electrocardiographically as bundle branch block or nonspecific intraventricular conduction delay. We aimed to assess the long-term survival of an incidental intraventricular conduction delay finding in a cohort of individuals without ischemic heart disease, followed up for 3 decades.

METHODS

A randomized stratified cohort of the adult Israeli population underwent medical examinations and electrocardiography between 1976 and 1982. Patients with ischemic heart disease were excluded, and the cohort was followed for all-cause mortality for a median of 30.4 years. Major intraventricular conduction delay was defined as having complete bundle branch block or nonspecific intraventricular conduction delay, and minor intraventricular conduction delay was defined as having incomplete bundle branch block. Cox proportional hazard model was performed, comparing individuals by electrocardiogram finding, adjusting for demographic, clinical, and electrocardiographic variables.

RESULTS

Of 2465 subjects, 2385 (96.8%) were without intraventricular conduction delay, 38 (1.5%) had minor intraventricular conduction delay, and 42 (1.7%) had major intraventricular conduction delay. All-cause mortality rates were higher among minor and major intraventricular conduction delay groups (57.9% and 66.7%, P = .43 and P = .04, respectively) compared with no intraventricular conduction delay (52.1%). By controlling for sex, age, and body mass index, intraventricular conduction delay was not associated with all-cause mortality: hazard ratios, 0.82 (95% confidence interval, 0.52-1.25) and 1.06 (95% confidence interval, 0.72-1.54) for minor and major intraventricular conduction delay, respectively.

CONCLUSIONS

Intraventricular conduction delay was not found to be an independent risk factor for all-cause mortality in individuals without ischemic heart disease.

Association between Progressive Intraventricular Conduction Disturbance and Cardiovascular Events

Background

Prolonged QRS duration on electrocardiogram (ECG) has been known as a poor prognostic marker. However, little is known about association between progressive intraventricular conduction disturbance and cardiovascular prognosis.

Methods

From among a database containing 359,737 12-lead ECG recordings, patients whose QRS duration progressively increased from <120 msec to ≥120 msec were selected using software. The prognosis of patients was searched by medical record. The primary endpoint was defined as heart failure hospitalization. The secondary endpoint was heart failure hospitalization, device implantation, or cardiovascular death.

Results

A total of 143 patients (100 males; age, 58.9±11.1 years) were enrolled in this study. QRS duration increased by 46.4±13.8 msec, manifesting right bundle branch block (RBBB) in 99 (69.2%) patients and non-RBBB (i.e., left bundle branch block, RBBB with left anterior hemiblock, or nonspecific intraventricular conduction disturbance) in 44 (30.8%). During the follow-up (mean, 16.6±5.3 years), 44 (30.3%), 15 (10.3%), and 6 (4.1%) patients resulted in heart failure hospitalization, device implantation, and cardiovascular death, respectively. Multivariate Cox proportional hazards models revealed that 1) the temporal increase in QRS duration was associated with the primary endpoint (hazard ratio [HR] 1.98; 95% confidence interval [CI] 1.05–3.80; p = 0.04) and the secondary endpoint (HR 2.79; 95% CI 1.55–5.00; p = 0.0001) and 2) the development of non-RBBB was associated with the primary endpoint (HR 3.02; 95% CI 1.59–5.73; p = 0.0001) and the secondary endpoint (HR 2.82; 95% CI 1.57–5.09; p = 0.001).

Conclusion

The temporal increase in QRS duration and the development of non-RBBB patterns were independently associated with adverse cardiovascular prognosis.

The Prognostic Significance of Right Bundle Branch Block: A Meta-analysis of Prospective Cohort Studies

BACKGROUND

The prognostic significance of right bundle branch block (RBBB) is inconsistent across studies. We aimed to assess the association between RBBB (in general population and patients with heart disease) and risk of all-cause mortality, cardiac death, acute myocardial infarction (MI), and heart failure (HF).

HYPOTHESIS

RBBB may be associated with increased risk of death.

METHODS

PubMed, EMBASE, and the Cochrane Library up to February 2015 were searched for prospective cohort studies that reported RBBB at baseline and all-cause mortality, cardiac death, MI, and HF at follow-up. A meta-analysis of published data was undertaken primarily by means of fixed-effects models.

RESULTS

Nineteen cohort studies including 201 437 participants were included with a mean follow-up period ranging from 1 to 246 months. For general population with RBBB, the pooled adjusted hazard ratio (HR) for all-cause mortality was 1.17 (95% confidence interval [CI]: 1.03-1.33) compared with no BBB. General population with RBBB had an increased risk of cardiac death (HR: 1.43, 95% CI: 1.17-1.74). For patients with RBBB and acute MI, the pooled risk ratio was 2.31 (95% CI: 2.13-2.49) for in-hospital mortality, 2.85 (95% CI: 2.46-3.30) for 30-day mortality, and 1.96 (95% CI: 1.59-2.42) for longer-term mortality. For acute HF patients, the pooled risk ratio of all-cause mortality was 1.11 (95% CI: 1.06-1.16), and for chronic HF patients it was 1.75 (95% CI: 1.38-2.22).

CONCLUSIONS

Right bundle branch block is associated with an increased risk of mortality in general population and patients with heart disease.