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

Electrical Resynchronization and Clinical Outcomes During Long-Term Follow-Up in Intraventricular Conduction Delay Patients Applied Left Bundle Branch Pacing-Optimized Cardiac Resynchronization Therapy

BACKGROUND

Left bundle branch-optimized cardiac resynchronization therapy (LOT-CRT) has shown encouraging results for QRS duration reduction and heart function improvement. However, the feasibility and efficacy of LOT-CRT have not been well established in intraventricular conduction delay patients. This study aims to assess and compare the efficacy and clinical outcome of CRT based on left bundle branch pacing, combined with coronary sinus left ventricular pacing (LOT-CRT) with CRT via biventricular pacing (BiV-CRT) in intraventricular conduction delay patients indicated for CRT.

METHODS

Consecutive patients with intraventricular conduction delay and CRT indications were assigned nonrandomized to LOT-CRT (n=30) or BiV-CRT (n=55). Addition of the left bundle branch pacing (or coronary venous) lead was at the discretion of the implanting physician guided by suboptimal paced QRS complex and on clinical grounds. Echocardiographic parameters and clinical characteristics were accessed at baseline and during 2-years' follow-up.

RESULTS

Success rate for LOT-CRT and BiV-CRT was 96.8% and 96.4%. LOT-CRT had greater reduction of QRS duration compared with BiV-CRT (42.7±17.4 ms versus 21.9±21.5 ms; P<0.001). Higher left ventricular ejection fraction was also achieved in LOT-CRT than BiV-CRT at 6-month (36.7±9.8% versus 30.5±6.4%; P<0.05), 12-month (34.8±7.6% versus 30.3±6.2%; P<0.05), 18-month (36.3±7.9% versus 28.1±6.6%; P<0.005), and 24-month follow-up (37±9.5% versus 30.5±7%; P<0.05). Adverse clinical outcomes including heart failure rehospitalization and mortality were lower in LOT-CRT group for 24 months follow-up (hazard ratio, 0.33; P=0.035).

CONCLUSIONS

LOT-CRT improves ventricular electrical synchrony and may provide greater clinical outcomes as compared with BiV-CRT in intraventricular conduction delay patients. These findings need further evaluation in future randomized controlled trials.

Association Between Intensive vs Standard Blood Pressure Control and Incident Left Ventricular Conduction Disease: A Post Hoc Analysis of the SPRINT Randomized Clinical Trial

Importance

Left ventricular conduction disease predicts heart failure and death, and the only strategies to mitigate its effects involve implantation of a permanent pacemaker. There are currently no proven preventive strategies for this common condition.

Objective

To determine the association between targeting intensive blood pressure (BP) control and the risk of developing left ventricular conduction disease.

Design, Setting, and Participants

This was a post hoc analysis of the 2-arm multicenter Systolic Blood Pressure Intervention Trial (SPRINT), which recruited participants from 102 sites in the US and Puerto Rico and was conducted from November 2010 until August 2015. Adults 50 years and older with hypertension and at least 1 other cardiovascular risk factor were included. Participants with baseline left ventricular conduction disease, ventricular pacing, or ventricular pre-excitation were excluded for the current analysis. Data were analyzed from November 2021 to November 2022.

Intervention

Participants were randomly assigned to a systolic BP target of less than 140 mm Hg (standard treatment group) or less than 120 mm Hg (intensive treatment group).

Main Outcome

The primary outcome was incident left ventricular conduction disease, including any fascicular or left bundle-branch block, assessed by serial electrocardiography. Incident right bundle-branch block was examined as a negative control.

Results

Among 3918 participants randomized to standard treatment and 3956 to intensive treatment (mean [SD] age, 67.6 [9.2] years; 2815 [36%] female) monitored for a median [IQR] 3.5 (0.02-5.2) years, 203 developed left ventricular conduction disease. Older age (hazard ratio per 10-year increase [HR], 1.42; 95% CI, 1.21-1.67; P < .001), male sex (HR, 2.31; 95% CI, 1.63-3.32; P < .001), and cardiovascular disease (HR, 1.46; 95% CI, 1.06-2.00; P = .02) were associated with a higher risk of left ventricular conduction disease. Assignment to intensive treatment was associated with a 26% lower risk of left ventricular conduction disease (HR, 0.74; 95% CI, 0.56-0.98; P = .04). These results persisted when incident ventricular pacing was included in the outcome and when considering all-cause death as a competing risk. In contrast, no association between randomization assignment and right bundle-branch block was observed (HR, 0.95; 95% CI, 0.71-1.27; P = .75).

Conclusions and Relevance

In this study, targeting intensive BP control was associated with lower risk of left ventricular conduction disease in a randomized clinical trial, suggesting that clinically relevant conduction disease may be preventable.

Trial Registration

ClinicalTrials.gov Identifier: NCT01206062.

Electrocardiographic Predictors of Atrial Fibrillation

BACKGROUND

Atrial fibrillation (AF) is the most common pathological arrhythmia, and its complications lead to significant morbidity and mortality. However, patients with AF can often go undetected, especially if they are asymptomatic or have a low burden of paroxysms. Identification of those at high risk of AF development may help refine screening and management strategies.

METHODS

PubMed and Embase databases were systematically searched for studies looking at electrocardiographic predictors of AF from inception to August 2021.

RESULTS

A total of 115 studies were reported which examined a combination of atrial and ventricular parameters that could be electrocardiographic predictors of AF. Atrial predictors include conduction parameters, such as the PR interval, p-wave index and dispersion, and partial interatrial or advanced interatrial block, or morphological parameters, such as p-wave axis, amplitude and terminal force. Ventricular predictors include abnormalities in QRS amplitude, morphology or duration, QT interval duration, r-wave progression and ST segment, i.e., t-wave abnormalities.

CONCLUSIONS

There has been significant interest in electrocardiographic prediction of AF, especially in populations at high risk of atrial AF, such as those with an embolic stroke of undetermined source. This review highlights the breadth of possible predictive parameters, and possible pathological bases for the predictive role of each parameter are proposed.

The Relationship of Conduction Disorder and Prognosis in Patients with Acute Coronary Syndrome

OBJECTIVE

Conduction disorders with a widened QRS are associated with poor prognosis in patients with acute coronary syndrome (ACS). Conduction disorders include left bundle branch block (LBBB), right bundle branch block (RBBB), and nonspecific intraventricular conduction delay (NICD). Previous studies did not have conflicting results regarding the type of bundle branch block (BBB) with the worst prognosis, and few studies have focused on the prognosis of patients with NICD.

METHODS

Patients with ACS were enrolled between January 2005 and December 2019, and their medical history (International Classification of Diseases codes) was obtained from the Chang Gung Research Database. Age, sex, comorbidities, left ventricular ejection fraction (LVEF), and drug use were compared between the patients with and without conduction disorders. The following clinical outcomes were compared between patients with and without conduction disorders: heart failure (HF) hospitalization, cardiovascular (CV) mortality, and all-cause mortality. After propensity score matching, the Kaplan-Meier curve analysis for HF hospitalization, CV mortality, and all-cause mortality were compared among patients with LBBB, RBBB, and NICD.

RESULTS

This study enrolled a total of 33970 participants and involved 3392 and 30578 patients with and without conduction disorders, respectively. Older age and a higher prevalence of comorbidities were noted in patients with conduction disorders. Lower mean LVEF was exhibited in the patients with conduction disorders (with vs. without; 44.64 ± 20.73% vs. 49.85 ± 20.63%; p < 0.001). During the 3-year follow-up period, higher incidences of HF hospitalization (21.55% vs. 17.51%; p < 0.001), CV mortality (17.98% vs. 12.14%; p < 0.001), and all-cause mortality (38.86% vs. 31.15%; p < 0.001) were noted in the patients with conduction disorder. After ACS events, 10.0% of patients presented with conduction disorders, with LBBB in 3.3%, RBBB in 6.0%, and NICD in 0.7%. The lowest mean of LVEF was presented in the patients with NICD (LBBB vs. RBBB vs. NICD; 41.00 ± 19.47% vs. 47.73 ± 20.82% vs. 34.57 ± 20.02%; p < 0.001). Among the three groups, the highest incidence of HF hospitalization was noted in patients with LBBB after propensity score matching. The lowest incidence of CV and all-cause mortality was observed in patients with RBBB. After adjustment of age, gender, comorbidities, medication, and mean LVEF, those with LBBB had the highest hazard ratio for major adverse cardiovascular events (MACEs) of 1.113 (p=0.029; 95% CI = 1.013-1.266).

CONCLUSIONS

In the ACS population, patients with conduction delay had a poor prognosis due to a higher prevalence of comorbidities and lower mean LVEF. Among the patients with LBBB, RBBB, and NICD, those with LBBB and NICD had a higher incidence of HF hospitalization, CV mortality, and all-cause mortality. Patients with NICD had the lowest mean LVEF compared to those with LBBB and RBBB. Patients with LBBB had a significantly highest HR of MACE.