Long-term outcomes of left bundle branch block in high-risk survivors of acute myocardial infarction: The VALIANT experience

Incidence and prognosis of cardiac conduction system diseases in hypertension: the STEP trial

Patients with cardiac conduction system diseases (CSD) may have increased incidence and mortality of cardiovascular events. Here we report a post hoc analysis of the Strategy of Blood Pressure Intervention in the Elderly Hypertensive Patients (STEP) randomized clinical trial (ClinicalTrials.gov number, NCT03015311) concerning the effect of intensive blood pressure (BP) control on the incidence of new-onset CSD and the prognostic implications of preexisting or new-onset CSD. The incidence of new-onset CSD was similar in the intensive (n = 205, 6.42%) and standard (n = 188, 5.94%) treatment arms. Participants with preexisting CSD had a higher risk for acute decompensated heart failure. Increased age, male sex and increased body mass index were independently associated with increased risk for new-onset CSD. Our results suggest that intensive BP control may not reduce the incidence of new-onset CSD compared with standard BP control.

Association Between New-Onset Type 2 Diabetes and Cardiac Conduction Diseases: A Prospective Cohort Study

BACKGROUND

Cardiac conduction diseases can lead to life-threatening outcomes. However, the evidence on risk factors for conduction disease that is needed to underpin prevention strategies is limited. The present study aimed to determine the association between type 2 diabetes and cardiac conduction diseases.

METHODS AND RESULTS

This study included 101 080 participants free of prevalent diabetes and cardiac conduction diseases at baseline from the Kailuan Study. All participants were monitored biennially until December 31, 2020. During follow-up, 14 397 participants were diagnosed as having type 2 diabetes. For each case subject, 1 control subject was randomly selected, matched for age (±1 year) and sex. The final analysis comprised 10 744 case-control pairs. Cox regression models with age as the underlying time scale were used. During a median follow-up of 5.46 years, 571 incident events occurred, including 164 atrioventricular blocks, 414 bundle-branch blocks (BBBs), 274 right BBBs, and 210 left BBBs. After adjustment for potential confounders, participants with type 2 diabetes diagnosed had greater relative risks for most outcomes relative to controls, with hazard ratios of 1.42 (95% CI, 1.18-1.67) for conduction diseases, 1.40 (95% CI, 1.00-1.96) for atrioventricular blocks, 1.43 (95% CI, 1.16-1.75) for BBBs, and 1.69 (95% CI, 1.15-2.49) for left BBBs. In contrast, no association between diabetes and right BBB was observed.

CONCLUSIONS

In this study, participants with type 2 diabetes are at an increased risk of cardiac conduction disease but not associated with the development of right BBB.

Evolution of Pacemakers and Implantable Cardioverter Defibrillators (ICDs) in Cardiology

Pacemakers and implantable cardioverter defibrillators (ICDs) have revolutionized cardiology by providing life-saving interventions for patients with cardiac rhythm disturbances. Pacing the heart is an effective treatment for people suffering from bradycardia caused by sinus node dysfunction or atrioventricular (AV) block, and electronic pacing has saved countless lives since its introduction into clinical practice. AV synchronization is the typical cycle of atrial depolarization and contraction followed by ventricular depolarization and contraction. The continuation of this cycle leads to appropriate ventricular filling and cardiac output. By contrast, the failure of the cycle results in AV asynchrony, which may result in heart failure. Cardiac resynchronization treatment (CRT) involves using customized pacemakers with or without implantable cardioverter defibrillators and tries to resynchronize the failing heart by enhancing myocardial contraction without increasing energy consumption. This review delves into the extensive journey of pacemakers and ICDs in the field of cardiology. It highlights the transformative impact of these devices on patient care and quality of life, emphasizing technological advancements, clinical applications, and prospects. This comprehensive review aims to provide insights into the dynamic landscape of cardiac rhythm management.

Device treatment of heart failure

Background: The incidence of heart failure (HF) is rapidly increasing, introducing a significant burden and challenges in clinical practice. Non-pharmacological cardiac device therapy has been established as an essential component of optimal HF management, particularly for the prevention of sudden cardiac death and the improvement of HF symptoms, left ventricular (LV) systolic function, quality of life, and eventually survival.Current Concepts: Cardiac resynchronization therapy (CRT) can correct atrioventricular or inter/intraventricular dyssynchrony, thereby improving LV systolic function. Recently, the concept of CRT is being expanded, including His bundle (HB), HB-optimized LV, left bundle branch (LBB), and LBB optimized LV pacing CRTs. Newly introduced CRT approaches by stimulating the cardiac conduction system are expected to correct dyssynchrony better and consequently exhibit better CRT outcomes than the conventional biventricular pacing CRT. The current versions of implantable cardioverter-defibrillators (ICDs) or CRT devices can continuously monitor multiple biosignals. CRT/ICD can calculate a single index by combining these multiple bio-signal data for early detection of HF aggravation. Recently, subcutaneous and transvenous ICDs showed comparable safety and efficacy in HF patients. In drug-refractory HF patients without LV dyssynchrony, cardiac contractility modulation therapy provides some promising results.Discussion and Conclusion: Recent technological advancements have improved the efficacy and safety of cardiac device therapy. Therefore, cardiac device therapy should be used more actively to manage HF patients better.

Challenges and Controversies in the Management of ACS in Elderly Patients

PURPOSE OF REVIEW

Elderly patients presenting with acute coronary syndrome (ACS) represent a challenging patient population. A high index of suspicion is needed for their diagnosis, as they are less likely to present with typical anginal symptoms compared to their younger counterparts.

RECENT FINDINGS

Disrupted coronary plaques with superimposed thrombosis are the predominant pathophysiology of ACS; however, an increased proportion of calcified nodules is encountered in elderly patients. Emergent reperfusion and revascularization remain the mainstay treatment for ST-elevation myocardial infarction or cardiogenic shock. In elderly patients with NSTE-ACS, a routine invasive strategy is generally superior to an ischemia-guided strategy, and the safety of an early invasive strategy has also been recently demonstrated. When treating elderly ACS patients with antiplatelet and antithrombotic therapies, close attention to co-morbidities, frailty and the balance of ischemia-bleeding risk should be undertaken, and medication doses should be carefully adjusted. Overall, elderly patients with ACS remain undertreated with evidence-based therapies, experience worse outcomes, and represent an opportunity for enhancing and mitigating healthcare disparities.

Cardiac Resynchronization Therapy in Preserved to Mildly Reduced Systolic Function

Cardiac resynchronization therapy has been proven to be clearly beneficial for patients with heart failure, a prolonged QRS duration, and a left ventricular ejection fraction ≤35%. Ejection fraction cutoff, however, is arbitrary and very likely excludes many patients who could benefit from cardiac resynchronization. This article describes the major detrimental effects of left bundle branch block and summarizes the data regarding the potential beneficial effects of cardiac resynchronization in patients with a left ventricular ejection fraction greater than 35%.

Prevalence of Intraventricular Conduction Disturbances in a Large French Population

BACKGROUND

Recommendations for the interpretation of electrocardiogram have been published in 2009. The aim of this study was to define the prevalence of intraventricular conduction disturbances (ICoDs) in a large population, using these recommendations.

METHODS

From 01/31/1996 to 09/22/2010, an electrocardiogram was performed at each visit for all aircrew members examined for fitness assessment in an aeromedical center. The prevalence of left bundle branch block (LBBB), right bundle branch block (RBBB), incomplete LBBB, incomplete RBBB, nonspecific intraventricular disturbance (NIVCD), left anterior fascicular block (LAFB), and left posterior fascicular block (LPFB) was measured and compared by age and gender.

RESULTS

The global prevalence of ICoD was 3.09% in our population of 69,186 patients. The most frequent types of ventricular blocks were IRBBB (1.25%) and LAFB (1.10%), whereas RBBB (0.46%), LBBB (0.08%), ILBBB (0.03%), NIVCD (0.05%), and LPFB (0.13%) were rare findings. ICoDs are more frequent for males and older age groups (P < 0.001).

DISCUSSION

Our results are comparable to studies concerning low cardiovascular risks populations. The association between ICoD and cardiovascular diseases needs to be studied in this population.

Ionic bases for electrical remodeling of the canine cardiac ventricle

Emerging evidence suggests that ventricular electrical remodeling (VER) is triggered by regional myocardial strain via mechanoelectrical feedback mechanisms; however, the ionic mechanisms underlying strain-induced VER are poorly understood. To determine its ionic basis, VER induced by altered electrical activation in dogs undergoing left ventricular pacing (n = 6) were compared with unpaced controls (n = 4). Action potential (AP) durations (APDs), ionic currents, and Ca(2+) transients were measured from canine epicardial myocytes isolated from early-activated (low strain) and late-activated (high strain) left ventricular regions. VER in the early-activated region was characterized by minimal APD prolongation, but marked attenuation of the AP phase 1 notch attributed to reduced transient outward K(+) current. In contrast, VER in the late-activated region was characterized by significant APD prolongation. Despite marked APD prolongation, there was surprisingly minimal change in ion channel densities but a twofold increase in diastolic Ca(2+). Computer simulations demonstrated that changes in sarcolemmal ion channel density could only account for attenuation of the AP notch observed in the early-activated region but failed to account for APD remodeling in the late-activated region. Furthermore, these simulations identified that cytosolic Ca(2+) accounted for APD prolongation in the late-activated region by enhancing forward-mode Na(+)/Ca(2+) exchanger activity, corroborated by increased Na(+)/Ca(2+) exchanger protein expression. Finally, assessment of skinned fibers after VER identified altered myofilament Ca(2+) sensitivity in late-activated regions to be associated with increased diastolic levels of Ca(2+). In conclusion, we identified two distinct ionic mechanisms that underlie VER: 1) strain-independent changes in early-activated regions due to remodeling of sarcolemmal ion channels with no changes in Ca(2+) handling and 2) a novel and unexpected mechanism for strain-induced VER in late-activated regions in the canine arising from remodeling of sarcomeric Ca(2+) handling rather than sarcolemmal ion channels.

Implications of left bundle branch block in patient treatment

Left bundle branch block (LBBB) causes an abnormal pattern of cardiac activation and affects regional myocardial function. Although recognition of LBBB on the surface electrocardiogram is straightforward, dissecting its effect on patient treatment and outcome can be more challenging. The altered pattern of cardiac activation in LBBB causes electrical and mechanical ventricular dyssynchrony, influences ischemia detection on the surface electrocardiogram, and affects stress testing and imaging modalities dependent on wall motion and thickening. Restoration of synchrony by biventricular pacing can improve symptoms and longevity in carefully selected patients. The diagnostic, prognostic, and therapeutic implications of LBBB across this spectrum are discussed in this review.

Thermal strain imaging: a review

Thermal strain imaging (TSI) or temporal strain imaging is an ultrasound application that exploits the temperature dependence of sound speed to create thermal (temporal) strain images. This article provides an overview of the field of TSI for biomedical applications that have appeared in the literature over the past several years. Basic theory in thermal strain is introduced. Two major energy sources appropriate for clinical applications are discussed. Promising biomedical applications are presented throughout the paper, including non-invasive thermometry and tissue characterization. We present some of the limitations and complications of the method. The paper concludes with a discussion of competing technologies.

QRS prolongation in patients with acute coronary syndromes

BACKGROUND

QRS prolongation with or without bundle branch block (BBB) has been associated with adverse outcome in myocardial infarction; we examined the relationship between QRS duration and outcome in a broad spectrum of patients with acute coronary syndrome (ACS).

METHOD AND RESULTS

Core laboratory evaluation of the presenting electrocardiogram in Canadian ACS Registry patients (n = 5,003) showed 4,289 (85.7%) had QRS <120 milliseconds, 202 (4.0%) patients had QRS > or =120 milliseconds without BBB, 262 (5.2%) had left BBB (LBBB), and 250 (5.0%) had right BBB. Compared to patients with QRS <120 milliseconds, patients with QRS > or =120 milliseconds without BBB had higher in-hospital (3.5% vs 1.9%, odds ratio [OR] 1.87, 95% CI 0.85-4.09, P = .12) and 1-year mortality (14.9% vs 7.7%, OR 2.10, 95% CI 1.38-3.18, P = .001). In-hospital and 1-year mortality was significantly higher in patients with BBB (eg, LBBB compared with QRS <120 milliseconds) (5.0% vs 1.9%, OR 2.71, 95% CI 1.49-4.94, P = .001, and 23.8% vs 7.7%, OR 3.74, 95% CI 2.72-5.13, P < .001). Analyzed as a continuous variable and after adjustment for validated prognosticators, QRS duration was an independent predictor of 1-year death (OR 1.11, 95% CI 1.06-1.16, P < .001) and death/myocardial infarction (OR 1.06, 95% CI 1.02-1.11, P = .003). However, when using clinically applicable QRS duration evaluation, only LBBB was an independent predictor of 1-year mortality (OR 1.93, 95% CI 1.28-2.90, P = .002).

CONCLUSIONS

In patients presenting with a broad spectrum of suspected ACS, QRS prolongation-particularly in the setting of LBBB-is an independent predictor of in-hospital and 1-year mortality.

Left bundle branch block as an electrocardiographic pattern at presentation of patients with Tako-tsubo cardiomyopathy

BACKGROUND

Tako-tsubo cardiomyopathy (TTC) is a recently described clinical condition that may mimic acute myocardial infarction. The presence or new onset of left bundle branch block (LBBB) is associated with adverse outcome in patients with acute myocardial infarction.

OBJECTIVE

We sought to assess the incidence, clinical profile, and outcome of patients with TTC and LBBB at presentation.

METHODS AND RESULTS

From July 2003 to December 2006, 84 consecutive patients met the diagnostic criteria for TTC. LBBB was present in eight (9%) patients at presentation. Patients with LBBB tended to be older (77 +/- 11 years versus 72 +/- 10 years; P=0.186), and with a more frequent, but not statistically significant, history of hypertension (75 versus 53%; P=0.227), and chronic renal failure (25 versus 8%, P=0.117). Moreover, patients with LBBB showed a higher peak creatine kinase-MB value (76 +/- 32 U/I versus 21 +/- 31 U/I; P=0.005), and a lower, but not significantly, baseline left ventricular ejection fraction (30 +/- 13% versus 36 +/- 9%; P=0.107), as compared with patients without LBBB. Follow-up length was 12 +/- 10 months. The mortality rate was higher in patients with LBBB as compared with those without (25 and 3%; P=0.005). However, at Cox analysis the only independent predictor of death was age (P=0.042).

CONCLUSION

LBBB was documented at presentation in 9% of TTC patients. At long-term follow-up, TTC patients with LBBB showed increased unadjusted mortality. However, when adjusted for age, baseline characteristics, and concomitant diseases, LBBB did not appear to be an independent predictor of poor outcome in patients with TTC.