Discordant vs. concordant left bundle branch block: A potential clinical significance

Outcomes with T-wave discordance of left bundle branch block and preserved or mildly reduced ejection fraction

AIMS

Left bundle branch block (LBBB) is associated with an increased risk of adverse outcomes for patients with heart failure. The prognosis of LBBB in patients with a preserved ejection fraction (EF) remains controversial. This study investigated the predictive value of T-wave discordance for the prognosis of patients with LBBB and preserved or mildly reduced EF.

METHODS AND RESULTS

We enrolled 707 patients with complete LBBB and left ventricular (LV) EF ≥ 40% observed using electrocardiograms (ECGs) and echocardiograms between January 2010 and December 2018. Their serial ECGs were reviewed during the follow-up period. The T-wave pattern was classified as discordant LBBB (dLBBB) or concordant LBBB (cLBBB) according to the 12-lead ECG T-wave morphology. The primary outcome was the composite of cardiovascular death or hospitalization for heart failure during a median follow-up period of 3.1 years. A multivariable Cox regression analysis was used to evaluate the independent predictors of the primary outcome. Patients with dLBBB had more comorbidities, a higher heart rate, a longer QRS and QTc duration, a larger LV end-systolic volume and left atrial dimension, a lower LVEF, and a higher mitral E/A ratio and E/e', compared with those with cLBBB. Older age [hazard ratio (HR) = 1.023, 95% confidence interval (CI) = 1.001-1.046, P = 0.023], history of heart failure (HR = 2.440, 95% CI = 1.524-3.905, P = 0.001), chronic kidney disease (HR = 1.917, 95% CI = 1.182-3.110, P = 0.008), larger LV end-systolic volume (HR = 1.046, 95% CI = 1.017-1.075, P = 0.002), lower LVEF (HR = 0.916, 95% CI = 0.885-0.948, P = 0.001), and presence of dLBBB (HR = 1.63, 95% CI = 1.011-2.628, P = 0.032) were independent predictors of the primary outcome in patients with LBBB and LVEF ≥ 40%. The discordant or concordant T-wave morphology of LBBB could transform from one subtype to the other in up to 23% of the study population during the follow-up period, and individuals with persistent or transformed dLBBB faced an increased risk of cardiovascular death or non-fatal heart failure hospitalization.

CONCLUSIONS

In patients with LBBB and EF ≥ 40%, dLBBB serves as an independent predictor of a higher risk of cardiovascular death or non-fatal heart failure hospitalization.

Comparison of Quantitative Perfusion and Function Parameters of Gated-SPECT Myocardial Perfusion Imaging in Patients With Concordant and Discordant Left Bundle-Branch Block

BACKGROUND

Patients with left bundle-branch block (LBBB) can be classified to discordant LBBB (dLBBB) and concordant LBBB (cLBBB) according to T-wave orientation in lateral leads. This classification indicates different functional left ventricular (LV) parameters with worse prognosis in dLBBB patients. However, there are no data regarding the impact of this classification on perfusion status of the left ventricle. The aim of this study is to evaluate and compare the SPECT myocardial perfusion imaging (MPI) findings of LV perfusion and function between dLBBB and cLBBB patients.

METHODS

All patients who were referred for SPECT MPI during an 11 months' period were evaluated. Patients with evidence of LBBB on standard baseline 12-lead ECG were included, and their demographic, medical history, and imaging data were recorded. Quantitative perfusion and function parameters of LV included summed stress score, summed rest score, summed difference score, total perfusion deficit (TPD) at both phases with delta TPD, ejection fraction, end-diastolic volume, end-systolic volume, summed motion score, summed thickening score, phase SD, and phase histogram bandwidth. All baseline ECGs were further assessed by a cardiologist to categorize patients as the cLBBB or dLBBB group according to concordance of the T wave with QRS complex in lateral leads.

RESULTS

Finally, 97 patients with 46 cLBBB and 51 dLBBB cases were included. Baseline characteristics and cardiovascular risk factors including diabetes mellitus, hypertension, hyperlipidemia, history of coronary artery disease (CAD), family history of CAD, and smoking were not significantly different between the 2 groups. However, summed stress score (12.2 vs 6.7), summed difference score (4.0 vs 2.6), stress TPD (11.0 vs 6.4), and delta TPD (4.8 vs 3.9) were significantly higher in dLBBB patients. In addition, functional parameters were also significantly worse in dLBBB patients with lower ejection fraction and higher end-diastolic volume, end-systolic volume, summed motion score, and summed thickening score in these patients. Mean phase SD and phase histogram bandwidth were also significantly higher in dLBBB patients.

CONCLUSIONS

This study revealed that LBBB patients with discordant T wave in lateral leads have significantly higher ischemic scores and worse functional parameters with more dyssynchrony in gated SPECT MPI.

Re-evaluating the electro-vectorcardiographic criteria for left bundle branch block

The criteria for left bundle branch block have gained growing interest in the last few years. In this overview, we discuss diagnostic and prognostic aspects of different criteria. It was already shown that stricter criteria, including longer QRS duration and slurring/notching of the QRS, better identify responders to cardiac resynchronization therapy. We also include aspects of ST/T concordance and discordance and vectorcardiography, which could further improve in the fine-tuning of the left bundle branch criteria.

Association between T-wave discordance and the development of heart failure in left bundle branch block patients: Results from the Copenhagen ECG study

BACKGROUND

In left bundle branch block (LBBB), discrepancies between depolarization and repolarization of the heart can be assessed by similar direction (concordant) or opposite direction (discordant) of the lateral T-waves compared to the direction of the QRS complex and by the QRS-T angle. We examined the association between discordant T-waves and high QRS-T angles for heart failure development in primary care LBBB patients.

METHODS

Between 2001 and 2011, we identified 2540 patients from primary care with LBBB without overt heart failure. We examined the development of heart failure in relation to two ECG measures: (1) LBBB as either discordant (two or three monophasic T-waves in the opposite direction of the QRS complex in leads I, V5 or V6) or concordant, and (2) the frontal plane QRS-T angle in quartile groups.

RESULTS

In total, 244 of 913 patients (26.7%) with discordant LBBB developed heart failure compared to 302 of 1627 patients (16.7%) with concordant LBBB. Multivariable Cox regression comparing discordant with concordant LBBB showed a hazard ratio (HR) of 2.58 (95% Confidence interval [CI] 1.71-3.89) for heart failure development within 30 days of follow-up and a HR of 1.45 (95%CI 1.19-1.77) after 30 days. For QRS-T angle, comparing the highest quartile (160°-180°) with the lowest quartile (0°-110°) we found a HR of 2.25 (95%CI 1.26-4.02) within 30 days and a HR of 1.67 (95%CI 1.25-2.23) after 30 days.

CONCLUSION

T-wave discordance in lateral ECG leads and a high QRS-T angle are associated with heart failure development in primary care LBBB patients.