2018 ACC/AHA/HRS guideline on the evaluation and management of patients with bradycardia and cardiac conduction delay: Executive summary: A Report of the American College of Cardiology/American Heart Association Task Force on Clinical Practice Guidelines, and the Heart Rhythm Society

Blood Pressure Control and Incident Left-Ventricular Conduction Disease

PURPOSE OF REVIEW

Cardiac conduction disease, a harbinger of pacemaker implantation, heart failure, and death, is commonly regarded as immutable. However, emerging research suggests it may be a target for upstream prevention strategies such as blood pressure management. This review summarizes recent evidence regarding blood pressure control and the development of conduction disease.

RECENT FINDINGS

Recent observational studies link hypertension to both prevalent and incident conduction disease. In randomized trials, intensive blood pressure control among hypertensive individuals reduced the incidence of left-ventricular conduction abnormalities in the form of fascicular- and left bundle branch blocks, while treatment with lisinopril independent of blood pressure control appeared to reduce conduction disease risk. Understanding factors that influence conduction system disease development may help inform novel primary prevention strategies. Recent evidence suggests that treatment of hypertension may play a key role in the prevention of conduction disease.

2023 HRS/APHRS/LAHRS guideline on cardiac physiologic pacing for the avoidance and mitigation of heart failure

Cardiac physiologic pacing (CPP), encompassing cardiac resynchronization therapy (CRT) and conduction system pacing (CSP), has emerged as a pacing therapy strategy that may mitigate or prevent the development of heart failure (HF) in patients with ventricular dyssynchrony or pacing-induced cardiomyopathy. This clinical practice guideline is intended to provide guidance on indications for CRT for HF therapy and CPP in patients with pacemaker indications or HF, patient selection, pre-procedure evaluation and preparation, implant procedure management, follow-up evaluation and optimization of CPP response, and use in pediatric populations. Gaps in knowledge, pointing to new directions for future research, are also identified.

Shared Decision Making and Cardioneuroablation Allow Discontinuation of Permanent Pacing in Patients with Vagally Mediated Bradycardia

BACKGROUND

Safe discontinuation of pacemaker therapy for vagally mediated bradycardia is a dilemma. The aim of the study was to present the outcomes of a proposed diagnostic and therapeutic process aimed at discontinuing or not restoring pacemaker therapy (PPM) in patients with vagally mediated bradycardia.

METHODS

The study group consisted of two subgroups of patients with suspected vagally mediated bradycardia who were considered to have PPM discontinued or not to restore their PPM if cardioneuroablation (CNA) would successfully treat their bradycardia. A group of 3 patients had just their pacemaker explanted but reimplantation was suggested, and 17 patients had preexisting pacemakers implanted. An invasive electrophysiology study was performed. If EPS was negative, extracardiac vagal nerve stimulation (ECVS) was performed. Then, patients with positive ECVS received CNA. Patients with an implanted pacemaker had it programmed to pace at the lowest possible rate. After the observational period and control EPS including ECVS, redo-CNA was performed if pauses were induced. The decision to explant the pacemaker was obtained based on shared decision making (SDM).

RESULTS

After initial clinical and electrophysiological evaluation, 17 patients were deemed eligible for CNA (which was then performed). During the observational period after the initial CNA, all 17 patients were clinically asymptomatic. The subsequent invasive evaluation with ECVS resulted in pause induction in seven (41%) patients, and these patients underwent redo-CNA. Then, SDM resulted in the discontinuation of pacemaker therapy or a decision to not perform pacemaker reimplantation in all the patients after CAN. The pacemaker was explanted in 12 patients post-CNA, while in 2 patients explantation was postponed. During a median follow-up of 18 (IQR: 8-22) months, recurrent syncope did not occur in the CNA recipients.

CONCLUSIONS

Pacemaker therapy in patients with vagally mediated bradycardia could be discontinued safely after CNA.

2023 HRS/APHRS/LAHRS guideline on cardiac physiologic pacing for the avoidance and mitigation of heart failure

Cardiac physiologic pacing (CPP), encompassing cardiac resynchronization therapy (CRT) and conduction system pacing (CSP), has emerged as a pacing therapy strategy that may mitigate or prevent the development of heart failure (HF) in patients with ventricular dyssynchrony or pacing-induced cardiomyopathy. This clinical practice guideline is intended to provide guidance on indications for CRT for HF therapy and CPP in patients with pacemaker indications or HF, patient selection, pre-procedure evaluation and preparation, implant procedure management, follow-up evaluation and optimization of CPP response, and use in pediatric populations. Gaps in knowledge, pointing to new directions for future research, are also identified.

Lithium-Induced Bradycardia and Cardiomyopathy in a Patient With Bipolar Disorder and Paranoid Schizophrenia

Lithium is primarily known to cause neurological and gastrointestinal side effects, however, cardiac effects have been rarely reported. We present a unique case of lithium cardiotoxicity causing bradyarrhythmia and cardiomyopathy. A 68-year-old man with a history of paranoid schizophrenia and bipolar disorder presented with altered mental status. On examination, the patient was lethargic, afebrile, with dry oral mucosa, and a regular pulse of 42 bpm. Labs revealed acute kidney injury and elevated lithium levels. Electrocardiogram (ECG) revealed a junctional escape rhythm with a right bundle morphology. Lithium toxicity was strongly suspected in the setting of raised serum lithium levels, decreased oral intake and acute kidney injury. The patient was found to have lithium-induced junctional bradycardia. Transvenous pacing was not indicated as the patient responded to fluids and atropine and had no severe hemodynamic compromise. As his serum lithium levels decreased, the bradycardia gradually improved. His echocardiogram revealed moderate left ventricular systolic dysfunction. Workup of cardiomyopathies was negative: no obstructive coronary artery disease; viral panel, and autoimmune markers were unremarkable. Thus, his cardiomyopathy was attributed to lithium toxicity. Lithium cardiotoxicity may manifest as arrhythmias and/or cardiomyopathy. Clinicians should have a high index of suspicion for lithium cardiotoxicity due to the narrow therapeutic range of lithium.

The Association of QRS Duration with Risk of Adverse Outcomes in Sex- and Race- Based Subgroups: The Dallas Heart Study

Introduction

We explored sex and race differences in the prognostic implications of QRS prolongation among healthy adults.

Methods

Participants from the Dallas Heart Study (DHS) free of cardiovascular (CV) disease who underwent ECG testing and cMRI evaluation were included. Multivariable linear regression was used to examine the cross-sectional association of QRS duration with left ventricular (LV) mass, LV ejection fraction (LVEF), and LV end diastolic volume (LVEDV). Association of QRS duration with risk of MACE was evaluated using Cox models. Interaction testing was performed between QRS duration and sex/race respectively for each outcome of interest. QRS duration was log transformed.

Results

The study included 2,785 participants. Longer QRS duration was associated with higher LV mass, lower LVEF, and higher LVEDV, independent of CV risk factors ([β: 0.21, P<0.001], [β: - 0.13, P<0.001], [β: 0.22, P<0.001] respectively). Men with longer QRS duration were more likely to have higher LV mass and higher LVEDV compared to women (P-int=0.012, P-int=0.01, respectively). Black participants with longer QRS duration were more likely to have higher LV mass as compared to White participants (P-int<0.001). In Cox analysis, QRS prolongation was associated with higher risk of MACE in women (HR = 6.66 [95% CI: 2.32, 19.1]) but not men. This association was attenuated after adjustment for CV risk factors, with a trend toward significance (HR = 2.45 [95% CI: 0.94, 6.39]). Longer QRS duration was not associated with risk of MACE in Black or White participants in the adjusted models. No interaction between sex/race and QRS duration for risk of MACE was observed.

Discussion

In healthy adults, QRS duration is differentially associated with abnormalities in LV structure and function. These findings inform the use of QRS duration in identifying subgroups at risk for CV disease, and caution against using QRS duration cut offs uniformly for clinical decision making.

What is known?

QRS prolongation in healthy adults is associated with higher risk of death, cardiovascular disease, and left ventricular hypertrophy.

What the study adds?

QRS prolongation may reflect a higher degree of underlying LV hypertrophy in Blacks compared to Whites. Longer QRS interval may reflect higher risk of adverse cardiac events, driven by prevalent cardiovascular risk factors.

Graphic Abstract

Risk of underlying left ventricular hypertrophy in demographic groups based on QRS prolongation.

Multi-modality imaging to guide the implantation of cardiac electronic devices in heart failure: is the sum greater than the individual components?

Heart failure is a clinical syndrome with an increasing prevalence and incidence worldwide that impacts patients' quality of life, morbidity, and mortality. Implantable cardioverter-defibrillator and cardiac resynchronization therapy are pillars of managing patients with HF and reduced left ventricular ejection fraction. Despite the advances in cardiac imaging, the assessment of patients needing cardiac implantable electronic devices relies essentially on the measure of left ventricular ejection fraction. However, multi-modality imaging can provide important information concerning the aetiology of heart failure, the extent and localization of myocardial scar, and the pathophysiological mechanisms of left ventricular conduction delay. This paper aims to highlight the main novelties and progress in the field of multi-modality imaging to identify patients who will benefit from cardiac resynchronization therapy and/or implantable cardioverter-defibrillator. We also want to underscore the boundaries that prevent the application of imaging-derived parameters to patients who will benefit from cardiac implantable electronic devices and orient the choice of the device. Finally, we aim at providing some reflections for future research in this field.

Trends in research on sick sinus syndrome: A bibliometric analysis from 2000 to 2022

Sick sinus syndrome (SSS) is a refractory arrhythmia disease caused by the pathological changes of sinoatrial node and its adjacent tissues. 2,251 publications related to SSS were retrieved from Web of Science database from 2000 to 2022 and analyzed by using VOS viewer and CiteSpace software. The results showed the United States dominated the field, followed by Japan, Germany, and China. SSS was closely related to risk factors such as atrial fibrillation and aging. Sick sinus syndrome, atrial fibrillation and sinus node dysfunction were the top three keywords that had the strongest correlation with the study. Pacemaker implantation, differentiation and mutation are research hotspots currently. Clinical studies on SSS found that sick sinus syndrome, atrial fibrillation, and pacemakers were the top three keywords that had the largest nodes and the highest frequency. In the field of basic applied research and basic research, atrial fibrillation and pacemaker cells were the focus of research. In conclusion, bibliometric analysis provided valuable information for the prevention, treatment and future research trends of SSS.

The Interplay of PR Interval and AV Pacing Delays Used for Cardiac Resynchronization Therapy in Heart Failure Patients: Association with Clinical Response in a Retrospective Analysis of a Large Observational Study

Background. Cardiac resynchronization therapy (CRT) is a treatment for heart failure (HF) patients with prolonged QRS and impaired left ventricular (LV) systolic function. We aim to evaluate how the baseline PR interval is associated with outcomes (all-cause death or HF hospitalizations) and LV reverse remodeling (>15% relative reduction in LV end-systolic volume). Methods. Among 2224 patients with CRT defibrillators, 1718 (77.2%) had a device programmed at out-of-the-box settings (sensed AV delay: 100 ms and paced AV delay: 130 ms). Results. In this cohort of 1718 patients (78.7% men, mean age 66 years, 71.6% in NYHA class III/IV, LVEF = 27 ± 6%), echocardiographic assessment at 6-month follow-up showed that LV reverse remodeling was not constant as a function of the PR interval; in detail, it occurred in 56.4% of all patients but was more frequent (76.6%) in patients with a PR interval of 160 ms. In a median follow-up of 20 months, the endpoint of death or HF hospitalizations occurred in 304/1718 (17.7%) patients; in the multivariable regression analysis it was significantly less frequent when the PR interval was between 150 and 170 ms (hazard ratio = 0.79, 95% confidence interval (CI): 0.63−0.99, p = 0.046). The same PR range was associated with higher probability of CRT response (odds ratio = 2.51, 95% CI: 1.41−4.47, p = 0.002). Conclusions. In a large population of CRT patients, with fixed AV pacing delays, specific PR intervals are associated with significant benefits in terms of LV reverse remodeling and lower morbidity. These observational data suggest the importance of optimizing pacing programming as a function of the PR interval to maximize CRT response and patient outcome.

Left-bundle branch pacing as bail-out strategy after failed coronary sinus lead placement for cardiac resynchronization: a case report

Background

Cardiac resynchronization therapy (CRT) by implantation of an endocardial coronary sinus (CS) pacing lead is an established heart failure therapy. The recent European Society of Cardiology (ESC) guidelines on cardiac pacing and CRT recommend conduction system pacing (CSP) as a potential bail-out therapy in patients with previously unsuccessful CS-lead implantation. We present a case in which unsuccessful implantation of a CS pacing and ineffective QRS correction by His-bundle pacing (HBP) was overcome by left-bundle branch pacing (LBBP) to achieve cardiac resynchronization.

Case summary

The patient had to undergo revision of a CS lead for CRT due to rising pacing thresholds and pacing impedance. CS-lead implantation was omitted by a stenotic posterolateral CS branch. HBP did not lead to adequate QRS correction. The patient underwent successful LBB lead implantation as bail-out therapy. After LBBP lead implantation electrocardiographic and echocardiographic parameters were evident of effective CRT.

Discussion

Conduction system pacing may be an alternative to CS pacing for CRT in heart failure patients, which is endorsed by the current European guidelines. LBBP may overcome limitations of HBP and provide an alternative to other strategies such as surgical implantation of epicardial left-ventricular pacing leads. Further studies are needed to fully clarify the role of LBBP for heart failure treatment.

Comparison of the Acute Effects of Different Pacing Sites on Cardiac Synchrony and Contraction Using Speckle-Tracking Echocardiography

Background: Cardiac pacing in patients with bradyarrhythmia may employ variable pacing sites, which may have different effects on cardiac function. Left bundle branch pacing (LBBP) is a new physiological pacing modality, and the acute outcomes on cardiac mechanical synchrony during LBBP remain uncertain. We evaluated the acute effects of four pacing sites on cardiac synchrony and contraction using speckle-tracking echocardiography, and comparisons among four different pacing sites were rare.

Methods: We enrolled 21 patients with atrioventricular block or sick sinus syndrome who each sequentially underwent acute pacing protocols, including right ventricular apical pacing (RVAP), right ventricular outflow tract pacing (RVOP), His bundle pacing (HBP), and left bundle branch pacing (LBBP). Electrocardiograms and echocardiograms were recorded at baseline and during pacing. The interventricular mechanical delay (IVMD), the standard deviation of the times to longitudinal peak strain during 17 segments (PSD), and the Yu index were used to evaluate ventricular mechanical synchrony. Layer-specific strain was computed using two-dimensional speckle tracking technique to provide in-depth details about ventricular synchrony and function.

Results: Left ventricular ejection fraction (LVEF) and tricuspid annulus plane systolic excursion (TAPSE) were significantly decreased during RVAP and RVOP but were not significantly different during HBP and LBBP compared with baseline. RVAP and RVOP significantly prolonged QRS duration, whereas HBP and LBBP showed non-significant effects. IVMD and PSD were significantly increased during RVAP but were not significantly different during RVOP, HBP, or LBBP. LBBP resulted in a significant improvement in the IVMD and Yu index compared with RVAP. No significant differences in mechanical synchrony were found between HBP and LBBP.

Conclusion: Among these pacing modalities, RVAP has a negative acute impact on cardiac synchrony and contraction. HBP and LBBP best preserve physiological cardiac synchrony and function.

Basic surface electrocardiogram interpretation for the pharmacist

PURPOSE

The electrocardiogram (ECG) is an invaluable tool for clinicians that provides important information about a patient's heart. As clinical pharmacists play an ever-increasing role in cardiovascular care, ECG interpretation is an important skill with which to become familiar.

SUMMARY

The ECG provides information on both electrical and biomechanical aspects of the heart. Electrical information such as the rhythm, rate, and axis of the electrical activity can all be provided by the ECG. Biomechanical information about the heart, such as the presence of ventricular hypertrophy and repolarization changes that may be associated with ischemia or myocardial injury, can also easily be gleaned from the ECG. Furthermore, the ECG plays a central role in both the diagnosis and treatment of common clinical conditions such as atrial fibrillation, ischemic heart disease, and QT interval prolongation.

CONCLUSION

The ECG is one of the most commonly performed diagnostic tests, and clinicians should become familiar with its basic interpretation.

Fracture of an epicardial left ventricular lead implanted at open-heart surgery in anticipation of future need for cardiac resynchronization therapy

Epicardial left ventricular leads can be implanted at open-heart surgery for cardiac resynchronization therapy. We report a 2-year-old fractured epicardial left ventricular lead detected at generator implant. It highlights the importance of good surgical implant technique and of rigorous lead evaluation for signs of impending failure at generator implant.

Optimal dose of pretreated-dexmedetomidine in fentanyl-induced cough suppression: a prospective randomized controlled trial

BACKGROUND

To investigate the optimal dose of pretreated-dexmedetomidine in fentanyl-induced cough (FIC) suppression.

METHODS

Patients of 180 undergoing elective surgery with general anesthesia, aged 18-65 years, BMI 18.5-30 kg/m2, ASA I or II, were equally randomized into four groups (n = 45) to receive intravenous pretreatment of dexmedetomidine with 0 (group 1), 0.3 (group 2), 0.6 (group 3) and 0.9 (group 4) mcg/kg over 10 mins, respectively. After the pretreatment, all patients were given a 5-s intravenous injection of fentanyl 4 mcg/kg. The symptoms of irritating cough including the severity and onset time were recorded for 1 min after fentanyl injection. General anesthesia induction was completed with midazolam, propofol and cisatracurium, then endotracheal tube or laryngeal mask was inserted and connected to an anesthesia machine. MAP, HR and SpO2 at the beginning of pretreatment (T0), 3 min (T1), 6 min (T2), 9 min (T3) and 12 min (T4) after the beginning of pretreatment were recorded. Side effects of dexmedetomidine, such as bradycardia, hypertension, hypotension, and respiratory depression were also recorded during the course.

RESULTS

Totally 168 patients completed the study. The incidences of cough were 52.4, 42.9, 11.9, and 14.3% in groups 1, 2, 3, and 4, respectively, with no significant differences between groups 1 and 2 (P > 0.05) and between groups 3 and 4 (P > 0.05). The incidence and severity of cough in groups 3 and 4 were significantly lower than those in groups 1 and 2 (P < 0.05). Compared to T0, HR at T2 (P < 0.05), T3 (P < 0.01), and T4 (P < 0.01) decreased significantly and MAP at T4 decreased significantly (P < 0.05) in group 4. Bradycardia occurred in 1 case and respiratory depression occurred in 1 case in group 4. Compared to group 1, the onset time of cough in the other 3 groups were delayed significantly (P < 0.05).

CONCLUSION

Pretreated dexmedetomidine 0.6 mcg/kg blous intravenous infusion over 10 mins could reduce FIC effectively without side effects.

TRIAL REGISTRATION

This study was registered in ClinicalTrials.gov (NCT03126422), April 13, 2017.