Left bundle branch block, an old-new entity

Assessment of myocardial strain patterns in patients with left bundle branch block using cardiac magnetic resonance

Recently, a classification with four types of septal longitudinal strain patterns was described using echocardiography, suggesting a pathophysiological continuum of left bundle branch block (LBBB)-induced left ventricle (LV) remodeling. The aim of this study was to assess the feasibility of classifying these strain patterns using cardiovascular magnetic resonance (CMR), and to evaluate their association with LV remodeling and myocardial scar. Single center registry included LBBB patients with septal flash (SF) referred to CMR to assess the cause of LV systolic dysfunction. Semi-automated feature-tracking cardiac resonance (FT-CMR) was used to quantify myocardial strain and detect the four strain patterns. A total of 115 patients were studied (age 66 ± 11 years, 57% men, 28% with ischemic heart disease). In longitudinal strain analysis, 23 patients (20%) were classified in stage LBBB-1, 37 (32.1%) in LBBB-2, 25 (21.7%) in LBBB-3, and 30 (26%) in LBBB-4. Patients at higher stages had more prominent septal flash, higher LV volumes, lower LV ejection fraction, and lower absolute strain values (p < 0.05 for all). Late gadolinium enhancement (LGE) was found in 55% of the patients (n = 63). No differences were found between the strain patterns regarding the presence, distribution or location of LGE. Among patients with LBBB, there was a good association between strain patterns assessed by FT-CMR analysis and the degree of LV remodeling and LV dysfunction. This association seems to be independent from the presence and distribution of LGE.

A personalized real-time virtual model of whole heart electrophysiology

Computer models capable of representing the intrinsic personal electrophysiology (EP) of the heart in silico are termed virtual heart technologies. When anatomy and EP are tailored to individual patients within the model, such technologies are promising clinical and industrial tools. Regardless of their vast potential, few virtual technologies simulating the entire organ-scale EP of all four-chambers of the heart have been reported and widespread clinical use is limited due to high computational costs and difficulty in validation. We thus report on the development of a novel virtual technology representing the electrophysiology of all four-chambers of the heart aiming to overcome these limitations. In our previous work, a model of ventricular EP embedded in a torso was constructed from clinical magnetic resonance image (MRI) data and personalized according to the measured 12 lead electrocardiogram (ECG) of a single subject under normal sinus rhythm. This model is then expanded upon to include whole heart EP and a detailed representation of the His-Purkinje system (HPS). To test the capacities of the personalized virtual heart technology to replicate standard clinical morphological ECG features under such conditions, bundle branch blocks within both the right and the left ventricles under two different conduction velocity settings are modeled alongside sinus rhythm. To ensure clinical viability, model generation was completely automated and simulations were performed using an efficient real-time cardiac EP simulator. Close correspondence between the measured and simulated 12 lead ECG was observed under normal sinus conditions and all simulated bundle branch blocks manifested relevant clinical morphological features.

Compelling new electrocardiographic markers for automatic diagnosis

BACKGROUND AND OBJECTIVE

The automatic diagnosis of heart diseases from the electrocardiogram (ECG) signal is crucial in clinical decision-making. However, the use of computer-based decision rules in clinical practice is still deficient, mainly due to their complexity and a lack of medical interpretation. The objetive of this research is to address these issues by providing valuable diagnostic rules that can be easily implemented in clinical practice. In this research, efficient diagnostic rules friendly in clinical practice are provided.

METHODS

In this paper, interesting parameters obtained from the ECG signals analysis are presented and two simple rules for automatic diagnosis of Bundle Branch Blocks are defined using new markers derived from the so-called FMM_ecg delineator. The main advantages of these markers are the good statistical properties and their clear interpretation in clinically meaningful terms.

RESULTS

High sensitivity and specificity values have been obtained using the proposed rules with data from more than 35,000 patients from well known benchmarking databases. In particular, to identify Complete Left Bundle Branch Blocks and differentiate this condition from subjects without heart diseases, sensitivity and specificity values ranging from 93% to 99% and from 96% to 99%, respectively. The new markers and the automatic diagnosis are easily available at https://fmmmodel.shinyapps.io/fmmEcg/, an app specifically developed for any given ECG signal.

CONCLUSIONS

The proposal is different from others in the literature and it is compelling for three main reasons. On the one hand, the markers have a concise electrocardiographic interpretation. On the other hand, the diagnosis rules have a very high accuracy. Finally, the markers can be provided by any device that registers the ECG signal and the automatic diagnosis is made straightforwardly, in contrast to the black-box and deep learning algorithms.

Cardiac hypertrophy and insulin therapy in a pre-term newborn: is there a relationship?

Background

Hypertrophic cardiomyopathy (HCM) in newborns is a rare condition with heterogeneous etiologies. While the relationship between hyperinsulinism and cardiac hypertrophy (CH) is known, hyperinsulinism has not been reported as cause of HCM.

Case presentation

We report the case of cardiac hypertrophy (CH) in an Extremely Low Birth Weight (ELBW) infant; this patient underwent insulin therapy after the onset of persistent hyperglycemia due to parenteral nutrition (PN), supporting the hypothesis of a role of iatrogenic hyperinsulinemia in the development of HCM.

Conclusions

The present case underlines the importance of a close cardiological follow-up in infants undergoing insulin infusion for an alteration in the glucose metabolism.

A Strain-Based Staging Classification of Left Bundle Branch Block-Induced Cardiac Remodeling

OBJECTIVES

This study speculated that longitudinal strain curves in left bundle branch block (LBBB) could be shaped by the degree of LBBB-induced cardiac remodeling.

BACKGROUND

LBBB independently affects left ventricular (LV) structure and function, but large individual variability may exist in LBBB-induced adverse remodeling.

METHODS

Consecutive patients with LBBB with septal flash (LBBB-SF) underwent thorough echocardiographic assessment, including speckle tracking-based strain analysis. Four major septal longitudinal strain patterns (LBBB-1 through LBBB-4) were discerned and staged on the basis of: 1) correlation analysis with echocardiographic indexes of cardiac remodeling, including the extent of SF; 2) strain pattern analysis in cardiac resynchronization therapy (CRT) super-responders; and 3) strain pattern analysis in patients with acute procedural-induced LBBB.

RESULTS

The study enrolled 237 patients with LBBB-SF (mean age: 67 ± 13 years; 57% men). LBBB-1 was observed in 60 (26%), LBBB-2 in 118 (50%), LBBB-3 in 29 (12%), and LBBB-4 in 26 (11%) patients. Patients at higher LBBB stages had larger end-diastolic volumes, lower LV ejection fractions, longer QRS duration, increased mechanical dyssynchrony, and more prominent SF compared with less advanced stages (p < 0.001 for all). Among CRT super-responders (n = 30; mean age: 63 ± 10 years), an inverse transition from stages LBBB-3 and -4 (pre-implant) to stages LBBB-1 and -2 (pace-off, median follow-up of 66 months [interquartile range: 32 to 78 months]) was observed (p < 0.001). Patients with acute LBBB (n = 27; mean age: 83 ± 5.1 years) only presented with a stage LBBB-1 (72%) or -2 pattern (24%).

CONCLUSIONS

The proposed classification suggests a pathophysiological continuum of LBBB-induced LV remodeling and may be valuable to assess the attribution of LBBB to the extent of LV remodeling and dysfunction.

Effects of Mechanical Dyssynchrony on Coronary Flow: Insights From a Computational Model of Coupled Coronary Perfusion With Systemic Circulation

Mechanical dyssynchrony affects left ventricular (LV) mechanics and coronary perfusion. Due to the confounding effects of their bi-directional interactions, the mechanisms behind these changes are difficult to isolate from experimental and clinical studies alone. Here, we develop and calibrate a closed-loop computational model that couples the systemic circulation, LV mechanics, and coronary perfusion. The model is applied to simulate the impact of mechanical dyssynchrony on coronary flow in the left anterior descending artery (LAD) and left circumflex artery (LCX) territories caused by regional alterations in perfusion pressure and intramyocardial pressure (IMP). We also investigate the effects of regional coronary flow alterations on regional LV contractility in mechanical dyssynchrony based on prescribed contractility-flow relationships without considering autoregulation. The model predicts that LCX and LAD flows are reduced by 7.2%, and increased by 17.1%, respectively, in mechanical dyssynchrony with a systolic dyssynchrony index of 10% when the LAD's IMP is synchronous with the arterial pressure. The LAD flow is reduced by 11.6% only when its IMP is delayed with respect to the arterial pressure by 0.07 s. When contractility is sensitive to coronary flow, mechanical dyssynchrony can affect global LV mechanics, IMPs and contractility that in turn, further affect the coronary flow in a feedback loop that results in a substantial reduction of dP_LV/dt, indicative of ischemia. Taken together, these findings imply that regional IMPs play a significant role in affecting regional coronary flows in mechanical dyssynchrony and the changes in regional coronary flow may produce ischemia when contractility is sensitive to the changes in coronary flow.

Differentiation between left bundle branch block (LBBB) preceded dilated cardiomyopathy and dilated cardiomyopathy preceded LBBB by cardiac magnetic resonance imaging

BACKGROUND

Dilated cardiomyopathy (DCM) may be a result of or the cause of left bundle branch block (LBBB) in patients with DCM and LBBB. It is almost impossible from the history alone to know which came first in clinical work.

METHODS

Patients with LBBB and DCM who had cardiac magnetic resonance (CMR) examination were analyzed. Occurrence sequence of DCM and LBBB was determined by chart reviewing. Diastolic lateral/septal wall thickness ratio (DLSWTR) and lateral wall thickening (LWT) were compared between patients with different time sequences. Response to CRT was analyzed according to medical history and CMR manifestation.

RESULTS

Sixty-three patients were divided into two groups by cluster analysis. DLSWTR and LWT were significantly higher in group 1 (preserved lateral wall thickness and function), compared to those in group 2 (reduced lateral wall thickness and function) (1.06 ± 0.13 vs. 0.8 ± 0.12, 34.57 ± 11.48% vs. 11.18 ± 5.56%, respectively, both P < .001). Occurrence sequence was clear in 14 patients and further analyzed. In group 1, seven patients were clearly having no evidence of DCM when LBBB was first diagnosed (defined as LBBB-precede-DCM) and in group 2, seven patients did not have LBBB when DCM was diagnosed (defined as DCM-precede-LBBB). Among 10 patients who received CRT therapy, all seven patients in group 1 responded well whereas none of three patients in group 2 responded well.

CONCLUSIONS

Occurrence sequence of DCM and LBBB can be discriminated by CMR. Preserved lateral wall morphology and function in CMR suggested LBBB preceded to DCM. Such features may be predictors of good response to CRT.

Clinical Presentations and Outcomes in Patients Presenting With Acute Cardiac Events and Right Bundle Branch Block

We conducted a retrospective analysis of 50 974 patients admitted with acute cardiac events with and without right bundle branch block (RBBB) over 23 years. Compared to non-RBBB, patients with RBBB (n = 386; 0.8%) were 3 years older ( P = .001), more likely to present with breathlessness rather than chest pain ( P = .001), and had more diabetes mellitus ( P = .001). Patients with RBBB had significantly higher cardiac enzymes ( P = .001); however, there were no significant differences in the presentation with ST-segment elevation myocardial infarction (24.6% vs 22.2%), non-ST-segment elevation myocardial infarction (23.7% vs 22.4%), and unstable angina (51.7% vs 55.4%). Patients with RBBB were more likely to have congestive heart failure (CHF; 9.6% vs 3.2%, P = .001), cardiogenic shock (10.6% vs 1.7%, P = .001), and ventricular tachyarrhythmias (7.3% vs 2.2%, P = .001). Left ventricular ejection fraction and hospital length of stay were comparable between the groups. All-cause mortality was 5 times greater in patients with RBBB (21% vs 4.2%, P = .001). Right bundle branch block was independent predictor of mortality (adjusted odd ratio 5.14; 95% confidence interval: 3.90-6.70). Subanalysis comparing normal QRS, RBBB, and left BBB showed that RBBB was associated with the worst outcomes except for CHF. Although RBBB presents in only about 1% of patients with cardiac disease, it was found to be an independent predictor of hospital mortality.

Rate and Predictors of Permanent Pacemaker Implantation After Transcatheter Aortic Valve Implantation: Current Status

Transcather aortic valve implantation (TAVI) has become a safe and indispensable treatment option for patients with severe symptomatic aortic stenosis who are at high surgical risk. Recently, outcomes after TAVI have improved significantly and TAVI has emerged as a qualified alternative to surgical aortic valve replacement in the treatment of intermediate risk patients and greater adoption of this procedure is to be expected in a wider patients population, including younger patients and low surgical risk patients. However since the aortic valve has close spatial proximity to the conduction system, conduction anomalies are frequently observed in TAVI. In this article, we aim to review the key aspects of pathophysiology, current incidence, predictors and clinical association of conduction anomalies following TAVI.

Prognostic utility of electrocardiograms in patients with hypertension older than 65 years. The PAFRES study

OBJECTIVE

Left ventricular hypertrophy is the most common marker of target organ damage in arterial hypertension. Electrocardiograms are typically performed to identify left ventricular hypertrophy. The aim of this study was to analyse the prognostic utility of other electrocardiographic abnormalities in patients with arterial hypertension, beyond ventricular hypertrophy.

MATERIALS AND METHODS

The study included 1003 patients older than 65years with arterial hypertension. We recorded risk factors, previous cardiovascular history and medical treatment and analysed various electrocardiographic abnormalities including the Sokolow-Lyon index, the Cornell index, ventricular overload and branch blocks. The study conducted a 2-year follow-up, recording the major cardiovascular events (mortality, myocardial infarction, stroke and hospitalisation for heart failure).

RESULTS

The study population's mean age was 72.9±5.8years, 47.5% of whom were men. During the follow-up, 13.9% of the patients experienced a major cardiovascular event. These patients were older, more often smokers and engaged in less physical exercise, without presenting differences in the antihypertensive therapy or blood pressure control. The ventricular overload pattern (HR: 1.93; 95%CI: 1.160-3.196; P=.011) and the complete left bundle branch block (HR: 2.27; 95%CI: 1.040-4.956; P=.040) behaved as independent electrocardiographic predictors of major cardiovascular events; however, left ventricular hypertrophy using the Sokolow and/or Cornell index did not behave as such.

CONCLUSIONS

For patients with hypertension, the presence in the baseline electrocardiogram of complete left bundle branch block or a pattern of ventricular overload identifies a population at increased cardiovascular risk.

Does 'super-responder' patients to cardiac resynchronization therapy still have indications for neuro-hormonal antagonists? Evidence from long-term follow-up in a single center

Background

Whether cardiac resynchronization therapy super-responders (CRT-SRs) still have indications for neuro-hormonal antagonists or not remains uninvestigated.

Methods

We reviewed clinical data from 376 patients who underwent CRT implantation in Fuwai Hospital from 2009 to 2015 and followed up to 2017. CRT-SRs were defined by an improvement of the New York Heart Association functional class and left ventricular ejection fraction to ≥ 50% in absolute values at 6-month follow-up. All CRT-SRs were assigned into two groups on the basis of whether persistently receiving neuro-hormonal antagonists (NHA) (defined as angiotensin-converting enzyme inhibitors/angiotensin receptor blockers and β-blockers) after 6-month follow-up and then we compared long-term outcome.

Results

A total of 60 patients met criteria for super-response. One of thirteen (7.7%) CRT-SRs without NHA had all-cause death, which also occurred in 2 of 47 (4.3%) in CRT-SRs with NHA (P = 0.526). However, 3 of 13 (23.1%) CRT-SRs without NHA had heart failure (HF) hospitalization, 1 of 47 (2.1%) CRT-SRs with NHA had this endpoint (P = 0.040). Besides, subgroup analysis indicated that, for ischemic etiology group, CRT-SRs receiving NHA had considerably lower incidence of HF hospitalization than those without NHA (0 vs. 75%, P = 0.014), which was not observed in non-ischemic etiology group (2.6% vs. 0, P = 1.000) during long-term follow-up.

Conclusions

Our study found that for ischemic etiology, compared with CRT-SRs with NHA, CRT-SRs without NHA were associated with a higher risk of HF hospitalization. However, for non-ischemic etiology, we found that CRT-SRs with NHA or without NHA at follow-up were associated with similar outcomes, which needed further investigation by prospective trials.

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.

Predictive Value of Septal Flash for Reduction of Left Ventricular Systolic Function as Reflected by Global Longitudinal Strain Using Echocardiography in Patients With Isolated Complete Left Bundle-Branch Block

BACKGROUND

Septal leftward motion followed by a counter motion during early systole is known as septal flash (SF) in patients with isolated complete left bundle-branch block (cLBBB). This study aimed to determine the predictive value of SF for reduction of left ventricular (LV) global systolic function using 2D speckle-tracking echocardiography (2D STE) in cLBBB patients.Methods and Results:The study group of 41 patients with isolated cLBBB and preserved LV ejection fraction and 41 age- and sex-matched control subjects were studied. The presence of SF and LV global longitudinal strain (GLS) were defined and measured using 2D STE. Multivariate logistic regression analysis identified the presence of SF as an independent factor predicting LV GLS >-20% in isolated cLBBB patients (odds ratio, 1.38; 95% confidence interval, 1.10-1.72; P=0.005). LV GLS in cLBBB patients with SF further decreased over time, whereas LV GLS did not decrease in patients without SF. The presence of SF was shown to be an independent factor predicting the reduction of LV global systolic function (relative reduction in LV GLS >15% from baseline to 2-year follow-up) (odds ratio, 1.27; 95% confidence interval, 1.06-1.50; P=0.008).

CONCLUSIONS

Assessment of SF by 2D STE may be an easy and effective method of predicting the reduction in LV global systolic function in isolated cLBBB patients.

Effect of septal flash on right ventricular systolic function in left bundle-branch block patients with preserved left ventricular ejection fraction

A leftward motion of the ventricular septum prior to ejection, known as the septal flash (SF), is frequently observed in patients with left bundle-branch block (LBBB). We investigated whether the abnormal motion of the ventricular septum affects right ventricle (RV) contractile performance in LBBB patients with preserved left ventricular ejection fraction (LVEF). Forty-four patients with complete LBBB were selected using standard 12-lead electrocardiograms (ECGs), with 30 healthy individuals serving as controls. According to the presence of SF, patients with LBBB were allocated to two subgroups: those with SF (LBBB-SF, n = 24) and those without SF (LBBB-NSF, n = 20). RV longitudinal strain (LS) decreased in LBBB patients with preserved LVEF compared to control subjects (p = 0.002). And RV LS decreased significantly in LBBB-SF patients compared to NSF-LBBB patients (p = 0.04). RV LS correlated negatively with involved septal myocardial segments of SF (r = −0.36, p = 0.02), but did not correlate with the magnitude of SF. RV contractile performance deceased in LBBB patients with preserved LVEF. SF, particularly the extent of this phenomenon, may further affect RV contractile performance.

Left ventricular twist was decreased in isolated left bundle branch block with preserved ejection fraction

OBJECTIVE

Left ventricular (LV) rotation and twist play an important role in LV contraction and relaxation. Left bundle branch block (LBBB) deteriorates both diastolic and systolic functions. We evaluated the LV twist in patients with LBBB and preserved ejection fraction (EF) (>50%) to determine twist as a potential marker for subtle myocardial dysfunction.

METHODS

This observational cross-sectional study included 34 LBBB patients with preserved EF who were free from ischemic and valvular disease (Group 1) and 36 healthy controls (Group 2). All patients underwent 2-D Doppler and 2-D speckle tracking echocardiography. LV apical, basal rotation, and twist were evaluated in both groups and compared accordingly. In addition, subjects were dichotomized considering the median twist value of the study population. Binary logistic regression analysis was performed to determine the independent variables associated with inframedian twist.

RESULTS

Baseline clinical characteristics were similar in LBBB patients and controls. Mean apical rotation (2.5°±1.9° vs. 4.4°±2.9°; p=0.002), basal rotation (-2.9°±2.3° vs. -4.1°±2.7°; p=0.05), and twist (5.4°±3° vs. 8.6°±3.3°; p<0.001) were decreased in group 1. Parameters related to intra- and interventricular mechanical dyssynchrony, such as longitudinal left ventricular dyssynchrony index (LVdys) and preejection interval of LV, interventricular mechanical delay (IVMD), and left posterior wall contractions (SPMWD) were significantly higher in the LBBB group. The median twist value of the studied population was 6.65°. Binary logistic regression analysis showed that only presence of LBBB was independently associated with inframedian twist (OR=6.250; 95% CI: 2.215-17.632; p<0.001).

CONCLUSION

The LBBB might have induced the reduction of LV twist by diminishing the LV rotation before inducing a prominent effect on the left ventricular ejection fraction (LVEF). Therefore, twist may be considered as a marker for subtle LV dysfunction in LBBB with substantially normal EF.

Rate-Dependent Left Bundle Branch Block in an Ambulatory Surgery Patient: A Case Report

A 52-year-old woman, ASA II (American Society of Anesthesia classification II) scheduled for cholecystectomy in an ambulatory center, exhibited a wide-complex tachycardia with ectopy on the monitor after induction with propofol and succinylcholine. Blood pressure remained stable; amiodarone was administered for presumed ventricular tachycardia. A 12-lead electrocardiogram (ECG) showed a new left bundle branch block (LBBB) at 98 beats per minute (bpm), which resolved when the heart rate slowed. Surgery was postponed, and both the LBBB and ectopy recurred frequently during the next 24 hours in the intensive care unit, particularly at heart rates >90 bpm. Troponins were normal, and the patient was diagnosed with a rate-dependent LBBB and cleared for surgery.

Pathophysiology, incidence and predictors of conduction disturbances during Transcatheter Aortic Valve Implantation

INTRODUCTION

Over the past decade, transcatheter aortic valve implantation (TAVI) has evolved rapidly toward an extremely reproducible, safe and effective procedure, with a marked reduction of its related complications. However, the occurrence of conduction disturbances and the need for permanent pacemaker implantation (PPI) after TAVI remains a concern. Areas covered: In this article review, we will go through the mechanisms involved in conduction disturbances after TAVI, and we will discuss the key aspects of pathophysiology, incidence and predictors of conduction disturbances following Transcatheter Aortic Valve Implantation. The evaluation of patient's valve anatomy and the selection of the most appropriate prosthesis have been proposed as a valuable options to reduce the incidence of conductions disturbances. Moreover, in recent times, a great number of new TAVI devices, so-called 'second-generation devices', have been introduced to address the limitations of the first-generation devices, including conduction disturbance, with scarce results. Expert commentary: Conduction disturbances after TAVI are increasingly recognized as an important issue in TAVI complications. Further characterization of the procedural- and patient-related factors that contribute to the development of conduction abnormalities will help to improve prosthesis designs and patient selection, making TAVI even more safer.

[Intermittent left bundle branch block - reversal to normal conduction during general anesthesia]

BACKGROUND AND OBJECTIVES

Transient changes in intraoperative cardiac conduction are uncommon. Rare cases of the development or remission of complete left bundle branch block under general and locoregional anesthesia associated with myocardial ischemia, hypertension, tachycardia, and drugs have been reported. Complete left bundle branch block is an important clinical manifestation in some chronic hypertensive patients, which may also be a sign of coronary artery disease, aortic valve disease, or underlying cardiomyopathy. Although usually permanent, it can occur intermittently depending on heart rate (when heart rate exceeds a certain critical value).

CASE REPORT

This is a case of complete left bundle branch block recorded in the preoperative period of urgent surgery that reverted to normal intraoperative conduction under general anesthesia after a decrease in heart rate. It resurfaced, intermittently and in a heart-rate-dependent manner, in the early postoperative period, eventually reverting to normal conduction in a sustained manner during semi-intensive unit monitoring. The test to identify markers of cardiac muscle necrosis was negative. Pain due to the emergency surgical condition and in the early postoperative period may have been the cause of the increase in heart rate up to the critical value, causing blockage.

CONCLUSIONS

Although the development or remission of this blockade under anesthesia is uncommon, the anesthesiologist should be alert to the possibility of its occurrence. It may be benign; however, the correct diagnosis is very important. The electrocardiographic manifestations may mask or be confused with myocardial ischemia, factors that are especially important in a patient under general anesthesia unable to report the characteristic symptoms of ischemia.

Genetic variation at the human connexin 43 locus but not at the connexin 40 locus is associated with left bundle branch block

Background

Bundle branch block (BBB) has been regarded as a disease of the conduction system, but occurs in mice lacking connexin 40 (expressed in atria, proximal conduction system) or connexin 43 (expressed in Purkinje cells, cardiomyocytes).

Objective

The aim of this paper is to explore whether BBB is heritable, and whether polymorphisms at connexin 40 and connexin 43 loci are associated with BBB.

Methods

To assess BBB heritability, we screened descendants of men with BBB in the population cohort ‘The Study of Men Born 1913’. DNA samples from 80-year-old men with extreme QRS-duration phenotypes were used to search for polymorphisms at connexin 40 and 43 loci. Associations between identified polymorphisms and BBB were evaluated in an independent cohort (INTERGENE).

Results

Seventy-seven men from ‘The Study of Men Born 1913’ with BBB had 116 descendants. Among the 76 participating descendants, 2 sons (6.4%) had BBB at 54 years of age. At the same age, 0.9% of men born in 1913 had BBB. We identified 6 single nucleotide polymorphisms (SNPs) in connexin 40 and 1 polymorphism in connexin 43. In the INTERGENE cohort, the connexin 43 polymorphism was associated with left BBB (LBBB) (4 of 35 LBBB vs 16 of 232 without BBB, χ²=7.4, p=0.03), but not with right BBB (RBBB) or overall BBB. None of the connexin 40 SNPs or haplotypes were associated with LBBB or RBBB.

Conclusions

These findings indicate that conduction by connexin 43 within the ventricular muscle distal to the specialised conduction system may be important for LBBB development.

Left Bundle Branch Block in Acute Cardiac Events: Insights From a 23-Year Registry

Between 1991 and 2013, we evaluated the demographics, presentations, and final diagnosis of patients hospitalized with acute cardiac events and left bundle branch block (LBBB). Of 50 992 patients, 768 (1.5%) had LBBB. Compared with non-LBBB patients, patients with LBBB were mostly older, female, diabetic, and had hypertension and chronic kidney failure (CKF; P < .001 for all). Dyspnea (P < .001) and dizziness (P = .037) were more frequent in patients with LBBB. The most frequent cause of admission with LBBB was congestive heart failure (CHF; 54.2%), followed by ST-elevation myocardial infarction (STEMI; 13.3%), valvular heart disease (9.4%), unstable angina (8.3%) and Non-STEMI (7.7%). On multivariate analysis, CKF (odds ratio [OR]: 2.02, 95% confidence interval [CI]: 1.09-3.70) and LBBB (OR: 2.96, 95% CI: 2.01-4.42) were predictors of in-hospital mortality in the entire study population. Further analysis of patients with LBBB showed that CKF (OR: 2.93, 95% CI: 1.40-6.12) was the only predictor of in-hospital mortality. Regardless the presenting symptoms, CHF was the final diagnosis in most cases with LBBB.

Bedside clinical and ultrasound-based approaches to the management of hemodynamic instability--part I: focus on the clinical approach: continuing professional development

Shock is defined as a situation where oxygen transport is inadequate to meet the body's oxygen demand. An understanding of the mechanism(s) of reduced cardiac output, a determinant of oxygen transport, is crucial in order to initiate appropriate therapy to manage shock. Combining the concept of venous return with the ventricular pressure-volume relationship is a useful method to appreciate the complex circulatory physiology of shock. Clues from the patient's history, physical examination, and key laboratory tests, along with the careful inspection of hemodynamic, electrocardiographic and respiratory waveforms can help with the identification of the etiology and mechanism(s) of shock. Following verification of the arterial pressure, general resuscitation can begin, and more specific treatment can be undertaken to manage shock. If the patient is unresponsive to these measures, bedside ultrasound can then be performed to ascertain more detail regarding the mechanism(s) and etiology of shock.

PURPOSE

To develop an approach to the management of the hemodynamically unstable patient.

PRINCIPAL FINDING

Not applicable.

CONCLUSION

Not applicable.

QRS duration in left bundle branch block does not affect left ventricular twisting in chronic systolic heart failure

PURPOSE

Left ventricular (LV) torsion is an important parameter of LV performance and can be influenced by several factors. Aim of this investigation was to evaluate whether QRS prolongation in left bundle branch block (LBBB) may influence global LV twist and twisting/untwisting rate in chronic systolic heart failure (HF) patients.

METHODS

We prospectively evaluated 30 healthy subjects (control group) and 100 chronic HF patients with severely impaired LV systolic function (ejection fraction ≤ 35%). Patients were divided into three groups according to QRS duration: A: QRS < 120 ms (n 49), B: 120 ≤ QRS ≤ 150 ms (n 28) and C: QRS > 150 ms (n 23). Patients in groups B and C presented LBBB. All subjects underwent standard trans-thoracic echocardiography and two-dimensional speckle-tracking echocardiography evaluation. Categorical variables were compared by the chi-square or the Fisher's exact test. Continuous variables were compared using the ANOVA test. Correlations between variables were analysed with linear regression.

RESULTS

Control subjects presented higher torsion parameters, when compared with patients in any HF group. Among the three HF groups, no differences were detected in global twist (4.79 ± 3.54, 3.8 ± 3.0 and 4.15 ± 3.14 degrees, respectively), twist rate max (44.81 ± 25.03, 37.94 ± 19.09 and 37.61 ± 24.49 degrees s(-1), respectively) and untwist rate max (-36.31 ± 30.89, -27.68 ± 34.67 and -39.62 ± 26.27 degrees s(-1), respectively) (P>0.05 for all). At linear regression analysis, there was no relation between QRS duration and any torsion parameter (P>0.05 for all).

CONCLUSIONS

In patients with chronic severe systolic heart failure, QRS duration and LBBB morphology do not affect LV twisting and untwisting.

Variations of QRS Morphology in Patients with Dilated Cardiomyopathy; Clinical and Prognostic Implications

The QRS represents the simultaneous activation of the right and left ventricles, although most of the QRS waveform is derived from the larger left ventricular musculature. Although normal QRS duration is <100 millisecond (ms), its duration and shape are quite variable from patient to patient in idiopathic dilated cardiomyopathy (IDCM). Prolongation of QRS occurs in 14% to 47% of heart failure (HF) patients. Left bundle branch block (LBBB) is far more common than right bundle branch block (RBBB). Dyssynchronous left ventricular activation due to LBBB and other intraventricular conduction blocks provides the rationale for the use of cardiac resynchronization therapy with biventricular pacing in patients with IDCM. Fragmented QRS (fQRS) is a marker of depolarization abnormality and present in significant number of the patients with IDCM and narrow QRS complexes. It is associated with arrhythmic events and intraventricular dyssynchrony. The purpose of this manuscript is to present an overview on some clinical, echocardiographic and prognostic implications of various QRS morphologies in patients with IDCM.

Exercise-induced left bundle branch block: an infrequent phenomenon: Report of two cases

Exercise-induced left bundle branch block (EI-LBBB) is infrequent phenomenon. We present two patients with angina pectoris who developed EI-LBBB during exercise tolerance test. The first patient with typical angina pectoris had significant obstructive coronary artery disease (CAD) requiring percutaneous coronary intervention of multiple lesions including placement of drug eluting stents. The second patient had atypical chest pain without signs of CAD at all. EI-LBBB occurred at a heart rate of 80 bpm and 141 bpm in the first and second patient, respectively. EI-LBBB remained visible through the test till the recovery period in the first patient at a heart rate of 83 bpm and disappeared at 96 bpm in the second patient. Both patients with this infrequent phenomenon are discussed and the literature is reviewed.