Rate-related Left Bundle Branch Block Research Articles

Antidromic AVRT with changing His activation. What is the mechanism?

We present a case of antidromic AVRT involving an atriofascicular pathway in a patient with an atretic coronary sinus os. This patient had left ventricular dysfunction with rate-related left bundle branch block aberrancy in sinus rhythm. In the electrophysiology lab, there was VA dissociation for a few beats during antidromic tachycardia. The possible mechanisms that could explain this intracardiac finding are discussed.

PO-01-044 THEOPHYLLINE FOR TREATMENT OF PAINFUL LEFT BUNDLE BRANCH BLOCK

Painful left bundle branch block (LBBB) is characterized by chest pain in setting of transient LBBB, in the absence of ischemia. Management has focused on pharmacological suppression of the sinus rate to prevent LBBB, or invasive therapy with permanent pacing. To determine the feasibility of using oral theophylline for treatment of painful LBBB. N/A A 71-year-old man presented for evaluation of exertional left-sided chest pain that resolved with rest. 12-lead electrocardiogram (ECG) showed sinus bradycardia at 54 bpm. Transthoracic echocardiogram was normal and coronary angiography showed non-obstructive coronary artery disease. Symptoms persisted despite treatment for microvascular angina with beta-blockers and ranolazine. Heart rate and ECG monitoring using an Apple watch demonstrated reproducible symptoms when heart rate increased above 80 bpm and resolution with decrease in heart rate below this threshold. Electrophysiology study demonstrated rate-related left bundle branch block and concurrent onset of symptoms with atrial pacing at a cycle length of 550 ms (∼109 bpm) (Panel A) and prompt resolution of symptoms with narrowing of QRS at lower pacing rates. Transient right bundle branch block was intentionally induced with catheter manipulation (Panel B) and atrial pacing produced 1:1 conduction down the left bundle with right bundle branch block up to 113 bpm with no symptoms and then to 2:1 block above the His (Panel C). Isoproterenol infusion allowed for atrial pacing up to 127 bpm without evidence of LBBB (Panel D). The patient was then discharged on theophylline 100 mg bid, which has a similar chronotropic and dromotropic effect as isoproterenol. He reported significant improvement in functional status with no recurrence in symptomatic LBBB. We report the first case of successful treatment of painful LBBB with oral theophylline. The mechanism may be improvement in conduction in damaged fibers to the left bundle. Theophylline should be considered in patients with painful LBBB in whom sinus node suppression has been unsuccessful and invasive management with permanent pacemaker is not desired.

B-PO05-156 ASSOCIATION AND PREDICTORS OF CARDIOMYOPATHY IN RATE-RELATED LEFT BUNDLE BRANCH BLOCK

Left bundle branch block (LBBB) has been identified as an independent cause of non-ischemic cardiomyopathy. Rate-related LBBB is an infrequent finding on stress tests (0.5% incidence) and has been associated with a higher all-cause mortality. However, the progression of rate-related LBBB to cardiomyopathy has not been well studied. We conducted a retrospective chart review to assess the characteristics of patients with rate-related LBBB and predictors of cardiomyopathy in this population. We identified all patients with LBBB during stress testing at our tertiary hospital from 2008-2020. Further we included those who developed rate-related LBBB and had transthoracic echocardiography (TTE) to assess their left ventricular ejection fraction (LVEF). Patients with right bundle branch block, resting LBBB, stress QRS<120 milliseconds, no TTE and ischemic cardiomyopathy were excluded. A total of 694 patients had LBBB on stress testing. Among these, 34 patients developed rate-related LBBB and met entry criteria. Females comprised 64.7%. Treadmill, dobutamine and vasodilator stress tests were performed in 23 (68%), 5 (15%) and 6 (17.6%) patients, respectively. Analysis of continuous variables showed moderate correlation (r=-0.4, p= 0.02) between LVEF and maximum stress QRS duration (maxQRS) and no significant correlation (r=0.3, p=0.08) with heart rate at which LBBB starts (HRstart). Patients with LVEF<40% had a wider maxQRS in rate-related LBBB than those with higher LVEF (157±11 vs 144±13, p=0.04). LBBB was noted earlier at a numerically lower mean HRstart in the LVEF<40% group but was not significantly different from the higher EF group (105±27 vs 116±28, p=0.45). Pre and post-stress QRS duration, sex, hypertension, coronary artery disease, beta blocker use and ACEi/ARB/ARNI use were not significant predictors of cardiomyopathy. Rate-related LBBB is not benign. Wider QRS duration during rate-related LBBB was associated with left ventricular dysfunction among these patients. Further prospective studies with larger sample size are needed to explore management options for patients with rate-related LBBB.

EXERCISE INDUCED LEFT BUNDLE BRANCH BLOCK RESULTING IN SEVERE MITRAL REGURGITATION

Exercise hemodynamic catheterization is helpful to evaluate exertional symptoms when noninvasive investigations fail to provide an explanation in non-ischemic cardiomyopathy. In this case, a rate-related left bundle branch block resulted in severe dynamic mitral regurgitation and acute increase in pulmonary capillary wedge pressure. Cardiac resynchronization therapy resolved her symptoms. (Level of Difficulty: Intermediate.).

Rate-related Left Bundle Branch Block Causing Cardiomyopathy

Background Rate-related left bundle branch block (LBBB) has not been well implicated as a cause of cardiomyopathy and its management remains controversial. Case presentation 52-year-old female presented with acute heart failure; EKG showed sinus tachycardia at 115 bpm with LBBB; an echocardiogram revealed left ventricle ejection fraction (LVEF) of 20%. Her cardiac catheterization showed no coronary disease, cardiac magnetic Resonance showed no late-gadolinium scaring or active inflammation. Heart Failure guideline directed medical therapy was started, including metoprolol succinate, Lisinopril and spironolactone. Follow-up echocardiogram at 4 months showed LVEF 25%. Clinical decision making Plan was to implant cardiac resynchronization therapy (CRT) with defibrillator (ICD); however, at time of implant, EKG showed sinus rhythm at 80 bpm with resolution of LBBB, hence, she underwent an ICD implantation instead. At 6 months, her symptoms improved and her LVEF noted to be 50%. We suspected rate-related LBBB as a cause for her cardiomyopathy. Serial EKGs while using her ICD atrial lead to pace at incremental rates, showed a predictable and reproducible LBBB at a ventricular rate of 110 bpm (Figure 1). ICD histogram showed her heart rate with current dose of metoprolol was predominantly under 110 bpm, which means minimal time in LBBB, which in turn likely resulted in resolution of cardiomyopathy. Conclusion Rate-related LBBB should be recognized as a potential cause of cardiomyopathy; management is to decrease the “time spent” in LBBB; if this is achieved by rate control alone, CRT can be avoided.

RATE-RELATED LEFT BUNDLE BRANCH BLOCK AND CARDIAC MEMORY IN A PATIENT WITHOUT ISCHEMIC HEART DISEASE

Cardiac memory (CM) is a phenomenon whereby reversible T-wave abnormalities on an electrocardiogram (ECG) arise due to a change in the direction of cardiac activation, which often happens with rate-related left bundle branch block (LBBB) or ventricular pacing and can mimic myocardial ischemia. We

Chest pain associated with rate-related left bundle branch block and cardiac memory mimicking ischemia

BackgroundIntermittent left bundle branch block (LBBB) has been linked to chest pain, and causes cardiac memory electrocardiographic (ECG) changes mimicking ischemia. PurposeTo present a case of chest pain with ECG abnormalities suggestive of ischemia, both likely caused by LBBB. CaseA 33-year-old hypertensive female evaluated for chest pain and LBBB by ECG was treated with lisinopril and metoprolol, and scheduled for stress testing. A 12-lead ECG performed prior to the stress test, due to recurrence of the chest pain the preceding night, showed resolution of the LBBB with a lower heart rate, and T-wave inversions in the precordial leads suggestive of ischemia. She developed chest pains with reappearance of LBBB during stress testing, which prompted cardiac catheterization. This revealed normal coronaries and left ventricular systolic function. The ECG abnormalities were in retrospect likely due to cardiac memory. Her chest pains may have been caused by the intermittent, rate-related LBBB, as control of her heart rate and blood pressure with metoprolol and lisinopril improved her symptoms on follow-up. ConclusionIntermittent LBBB causes chest pain and electrocardiographic abnormalities suggestive of ischemia in the absence of obstructive coronary disease. Certain clinical and electrocardiographic features may provide clues to a non-ischemic etiology.<Learning objective: In the absence of obstructive coronary disease, rate-related left bundle branch block is associated with chest pain described as local, non-radiating, with palpitations and walk-through phenomenon. It can also cause electrocardiographic (ECG) changes of cardiac memory, which mimic myocardial ischemia, but with T waves that are positive in lead aVL, positive or isoelectric in lead I, and more inverted in the precordial leads compared with lead III. These clinical and ECG features may provide clues to non-coronary etiology of chest pain.>

Acute Heart Failure Due to Transient Left Ventricular Dyssynchrony: Case Study

This case study describes an unusual cause of acute heart failure that resolved with early beta-blockade therapy. A 52-year-old woman who had acute heart failure with severe left ventricular systolic dysfunction and left bundle branch block was admitted to a university medical center. Contrast-enhanced magnetic resonance images of the heart did not show any evidence of myocardial infarction or myocarditis. Rate-related left bundle branch block and subsequent left ventricular dyssynchrony resulted in acute systolic dysfunction that resolved with beta-blockade therapy that allowed heart rate control and narrowing of the QRS complex. Of note, the use of inotropic agents would have dramatically worsened the cardiac condition.

New persistent and rate-related left bundle branch block in 116 apparently healthy males: correlation with coronary angiography and cardiac risk factors

New persistent and rate-related left bundle branch block in 116 apparently healthy males: correlation with coronary angiography and cardiac risk factors

Resolution of rate-related left bundle branch block after nitrate therapy

Resolution of rate-related left bundle branch block after nitrate therapy

Rate-related left bundle branch block as a cause of non-ischemic chest pain

A case is presented of rate-dependent left bundle branch block associated with chest pain in a patient with angiographically normal coronary arteries. Lactate extraction showed no evidence of myocardial ischemia. It appears that in this case, chest pain was associated with sudden ventricular asynergy rather than myocardial ischemia.

Initial ventricular activation in left-sided intraventricular conduction defects.

Nine patients with ECG evidence of rate-related left bundle branch block (LBBB) were studied using His bundle electrograms, electrograms from the right ventricular (RV) apex and vectorcardiograms recorded as heart rate was increased to produce LBBB. In five patients, when LBBB occurred, initially normal septal activation reversed and the HV intervals increased 10-30 msec, while the H-RVA interval did not change (group 1). Four patients had initially normal QRS duration (90-100 msec) but reversed septal activation (group 2). When LBBB developed there was no shift in either the HV interval or H-RVA interval. Only the QRS complex itself widened to distinguish these patients from group 1. These studies defined ventricular septal activation in normal conduction and in complete LBBB (group 1) and incomplete LBBB (group 2). The conduction patterns of group 1 and 2 patients are similar but are both markedly different from normal.

A Midsystolic Ejection Click

A patient of faintly marfanoid habitus with left venticular failure, aortic regurgitation, and rate-related left bundle-branch block was found to have a midsystolic click and echocardiographic findings suggestive of mitral valve prolapse; however, the click did not move earlier in systole in response to head-up tilt or atrial pacing. Cardiac catheterization and angiocardiographic studies revealed severe left ventricular dysfunction out of proportion to the moderate amount of aortic regurgitation observed on aortographic study. Mitral valve prolapse was not confirmed by left ventriculographic study. Intracardiac phonocardiographic and catheter-tip manometric studies identified the click as being aortic in origin, ejection in timing, and midsystolic, rather than early systolic, because of delayed aortic valve opening related to left ventricular dysfunction and delay in conduction.

Rate-Related Left Bundle Branch Block Secondary to Intra-His Block

A 67-year-old man who had chronic aortic valvular disease with first degree AV block and rate-related left bundle branch block on the surface electrocardiogram was studied by His bundle electrography. During conduction with narrow QRS complexes, the first degree block was AV nodal in origin. With spontaneous heart rate acceleration a QRS pattern of left bundle branch block emerged, and the His electrogram revealed split His potentials. This report adds strong support to the evolving concept that left bundle branch block, in some cases, actually may be secondary to block anatomically localized to the His bundle.

Bundle branch and ventricular activation in man: a study using catheter recordings of left and right bundle branch potentials.

His (H), right bundle branch (RB), and left bundle branch (LB) potentials were recorded by electrode catheters passed into the left and right ventricles in seven patients without conduction defects. In another three patients, H and LB were recorded. Initial ventricular activation was considered to coincide with the onset of the QRS (Q). The following intervals were measured in milliseconds: H-Q, LB-Q, RB-Q, H-LB, H-RB, and LB-RB. The average and range of these was as follows: H-Q 46 (39-54), LB-Q 27 (24-30), RB-Q 25 (20-27), H-LB 20 (14-28), H-RB 21 (15-29), and LB-RB 2 (1-10). LB-RB was 3 msec or less in six of seven patients. Coupled atrial pacing produced delays in H-RB without effect on H-LB and LB-Q. The production of incomplete and complete right bundle branch block was related to increase in the LB-RB interval. One patient developed left bundle branch block (LBBB) during coupled pacing with delay of LB while RB-Q remained unchanged. H-Q intervals were measured in three additional patients with rate related LBBB during both control and block. Prolongation of H-Q was less than 3 msec during LBBB. It is concluded that the proximal left and right bundle branches are usually activated simultaneously in man, and that block of either bundle without contralateral bundle delay does not significantly delay the onset of ventricular activation.