Clinical and Prognostic Significance of Idiopathic Left Bundle-Branch Block in Young Adults

The QRS frontal plane axis changes during left bundle branch block after transcatheter aortic valve replacement

BACKGROUND AND AIMS

Left bundle branch block (LBBB) is common after transcatheter aortic valve replacement (TAVR) and associated with a left or normal QRS axis. We aim to assess the QRS frontal plane axis shift changes during LBBB after TAVR and determine if the risk of procedure-related high degree atrioventricular block (AVB) is affected by QRS axis shift changes.

METHODS AND RESULTS

In a retrospective single-center study of 720 consecutive patients who underwent TAVR, 141 (19.6%) with normal baseline QRS duration developed a new LBBB after TAVR and constituted the study group. Most patients (59.6%) were females and the mean age of the cohort was 81.2 ± 6 years.

RESULTS

As compared with the baseline QRS axis before TAVR, the occurrence of LBBB was associated with a leftward QRS axis shift (by 40 ± 28.3°) in 73% of the study patients and a rightward (by 18.6 ± 19.4°) or no change in QRS axis in 25.6% and 1.4% of the study patients, respectively. A left QRS axis (-30°) was observed in 14.9% and 38.3% of the study patients before and after TAVR, respectively. The group of patients exhibiting a rightward or no QRS axis shift had a greater incidence of high degree AVB than the group of patients exhibiting a leftward QRS axis shift (18.4% vs. 6.8%, p = .056).

CONCLUSION

Although post TAVR-LBBB is associated with a leftward QRS axis shift in most patients, a non-negligible proportion of patients (27%) exhibited a rightward or no QRS axis shift. The latter group tend to have a higher risk of developing high degree AVB.

Myocardial work and energy loss of left ventricle obtained by pressure-strain loop and vector flow mapping: a new perspective on idiopathic left bundle branch block

Background

To date, no research has been conducted on the electrical activity and mechanical dyssynchrony of idiopathic left bundle branch block (iLBBB) with normal left ventricular ejection fraction (LVEF). This study sought to assess the left ventricular summation of energy loss (EL-SUM) and average energy loss (EL-AVE) using vector flow mapping as well as myocardial work using pressure-strain loop (PSL) in patients with iLBBB and normal LVEF.

Methods

We prospectively recruited 35 patients with iLBBB and 35 control participants with normal LVEF. Echocardiography was performed. Conventional echocardiographic parameters, myocardial work, and energy loss (i.e., the EL-SUM and EL-AVE) were calculated.

Results

In relation to global myocardial work, compared to the control participants, the iLBBB patients showed decreased global longitudinal strain (GLS; -15.32%±2.58% vs. -18.27%±2.12%; P=0.001), a decreased global work index (GWI; 1,428.24±338.18 vs. 1,964.87±264.16 mmHg%; P<0.001), decreased global work efficiency (GWE) (84.48±5.19 vs. 91.73±5.31 mmHg%; P<0.001), and significantly increased global waste work (GWW; 341.60±132.62 vs. 161.80±106.81 mmHg%; P<0.001). In relation to the regional index, the iLBBB patients had a significantly reduced basal anteroseptal segment (879.15±370.50 vs. 1,746.38±154.44 mmHg%; P<0.001), basal inferoseptal segment (1,111.42±389.04 vs. 1,677.25±223.10 mmHg%; P<0.001), mid-anteroseptal segment (1,097.54±394.83 vs. 1,815.06±291.22 mmHg%; P<0.001), mid-inferoseptal segment (1,012.54±353.33 vs. 1,880.88±254.39 mmHg%; P<0.001), apical anterior segment (1,592.42±366.64 vs. 1,910.00±170.27 mmHg%; P=0.001), apical lateral segment (1,481.62±342.95 vs. 1,817.19±227.55 mmHg%; P=0.001), apical septal segment (1,437.65±428.22 vs. 1,852.25±275.19 mmHg%; P=0.001), and apex (1,542.62±342.89 vs. 1,907.06±197.94 mmHg%; P<0.001). The iLBBB patients had increased EL-AVE and EL-SUM during the late-diastole, isovolumic-systole, and rapid-ejection periods [EL-AVE in T2: 28.3 (8.7, 49.0) vs. 6.8 (5.4, 9.4) J/(s·m³); P=0.029]; [EL-AVE in T3: 24.7 (13.0, 46.8) vs. 7.2 (5.4, 10.8) J/(s·m³), P<0.001]; [EL-AVE in T4: 18.3 (12.0, 27.6) vs. 7.7 (4.1, 11.6) J/(s·m³), P=0.002]; [EL-SUM in T2: 8.3 (2.2, 14.5) vs. 2.1 (1.6, 3.2) J/(s·m), P=0.049]; [EL-SUM in T3: 7.6 (4.0, 14.5) vs. 2.2 (1.7, 3.3) J/(s·m), P<0.001]; [EL-SUM in T4: 5.3 (3.6, 9.7) vs. 2.2 (1.4, 3.0) J/(s·m), P=0.004].

Conclusions

The GWI and GWE were reduced in patients with iLBBB, especially in the septum and apex. The EL-SUM and EL-AVE were higher in patients with iLBBB during the late-diastole, isovolumic-systole, and rapid-ejection periods. EL and PSL reflect the LV hemodynamics of patients with iLBBB.

Short-Coupled Idiopathic Ventricular Fibrillation: A Literature Review With Extended Follow-Up

Idiopathic ventricular fibrillation is responsible for approximately 10% of cases of aborted cardiac arrest. Recent studies have shown that short-coupled ventricular premature complexes are present at the onset of idiopathic ventricular fibrillation in 6.6%-17% of patients. The present review provided information on 86 patients with short-coupled malignant ventricular arrhythmias that were reported as case reports or small patient series during the last 70 years. In 75% of the 81 cases published during the last 40 years, extended information and follow-up (from 2.63 ± 4.5 to 10.67 ± 7.8 years; P < 0.001, between the original publication to the latest update) could be obtained from the authors. The review shows that short-coupled malignant ventricular arrhythmias occurred almost equally in males and females, at the mean age of 40 years. A tendency for later occurrence of the arrhythmia by 4 years was observed in females. A prior history of syncope was noted in 45.3% of the patients, whereas arrhythmic storm occurred in 42% at presentation. The most common mode of revelation of short-coupled malignant ventricular arrhythmias was syncope (53.5%), followed by aborted cardiac arrest (26.7%) and recurrent arrhythmic event after prior implantable-cardioverter defibrillator implantation for idiopathic ventricular fibrillation (17.4%). For the first time, short-coupled malignant arrhythmias exhibiting "not-so-short" coupling intervals (≥350 ms) were found in a significant proportion of patients (17.4%). During long-term follow-up, quinidine yielded a slightly higher success rate in arrhythmia control than ablation. Larger studies are necessary to assess the best strategy for the management of this potentially lethal arrhythmia.