Atrioventricular block secondary to transient causes and long-term recurrence after an index event.

BACKGROUND: Atrioventricular block (AVB) secondary to transient causes can recover with its correction. However, studies assessing predictors of recovery and long-term recurrence are lacking. METHODS: Patients with advanced or complete AVB who had a reversible cause admitted in a single expert center were retrospectively studied. Patients with AVB secondary to acute coronary syndromes were excluded from analysis. RESULTS: In a population of 162 patients, the main factors associated with recovery of rhythm without a permanent pacemaker (PPM) implantation were the presence of chronic kidney disease (CKD) on dialysis (OR 7.6; CI 95% 1.2-47.5 (p = .03)); greater serum potassium levels (OR 2.3; CI 95% 1.28-4.0 (p < .01)), higher dosage of bradycardic drugs (OR 2.2; CI 95% 1.13-4.4 (p = .02)), the association between different bradycardic drugs (OR 9.0; CI 95% 2.02-40.3 (p < .01)) and between drug therapy and hyperkaliemia (OR 5.2; CI 95% 1.8-15.1 (p < .01)). There was an overall high burden of conductions abnormalities which did not correlate with recovery of rhythm (OR 0.5; CI 95% 0.19-1.5 (p = .23)). In 29 patients (17.9%) there was a correction of the AVB. During a maximum follow-up of 130 months, 24 patients (82.8%) had a recurrence which warranted a PPM. In the overall cohort only five patients (3%) had sustained recovery of rhythm. CONCLUSIONS: Recovery of AVB was mainly observed with higher doses of drug therapy, higher serum potassium levels or a combination of factors and regardless of baseline conduction abnormalities. The high rate of recurrence during follow-up warrants a close follow-up or PPM implantation at index admission.

Arrhythmias and laboratory abnormalities after an electrical accident: a single-center, retrospective study of 333 cases.

BACKGROUND: Even though electrical injuries are common in the emergency room, guidelines, consensus, and general recommendations for the management of these patients do not exist in Europe. Documented cases of delayed arrhythmias are rare and their connection with electrical injury has not been fully confirmed. We also use cardio-specific markers for the risk stratification of myocardial injury, but there is no significant study referring to their utility in this clinical situation. These reasons led us to retrospectively analyze all cases of electrical injuries over 23 years to determine the prevalence of cardiac arrhythmias (mainly malignant arrhythmias and delayed arrhythmias). METHODS: We retrospectively searched all patients admitted to the University Hospital in Pilsen, CZ, with a diagnosis of electric injury (ICD diagnostic code T754) from 1997 to 2020. The hospital´s information system was used to research the injury; data were drawn from patient medical records. RESULTS: We identified 333 cases of electrical injury in our hospital. Men accounted for about two-thirds, and women one-third. Children accounted for about one-third of cases. Most were low-voltage injuries (< 1000 V, 91.6%). All participants had an initial ECG, and 77.5% of patients had continuous ECG monitoring, usually lasting 24 h. Cardiac arrhythmias were noticed in 39 patients (11.7%). The most frequent arrhythmias were: ventricular fibrillation, sinus tachycardia, bradycardia and arrhythmia, atrial fibrillation, and supraventricular tachycardia. The ECG showed cardiac conduction abnormalities in 28 patients (8.1%), and ten patients (3%) had supraventricular or ventricular extrasystoles. In ten cases (3%), we found changes in ST segments and T waves on the initial ECG. Thirty-one patients (9.3%) suffered a loss of consciousness and 50 patients (15.02%) reported paresthesia. The most frequent ion disbalances were hypokalemia (18%) and hypocalcemia (3.3%). Patients with an ion disbalance had significantly more arrhythmias and newly diagnosed cardiac conduction abnormalities. Troponin levels (cTnI or hs-cTnT) were measured in 258 cases (77.48%) and found to be elevated above the 99th percentile in 19 cases (5.7%). Almost one-third of patients had burns of various degrees of seriousness, and 41 patients (12.3%) had concomitant traumatic injuries. Eleven patients underwent pre-hospital resuscitation, three died in the hospital, and another died as result of intracranial hemorrhage. CONCLUSION: All malignant arrhythmias occurred immediately after the electrical injury, delayed life-threatening arrhythmias were not observed, and no predictive factors of malignant arrhythmias were found. While elevations of cardiac troponins were observed sporadically, they did not appear helpful for risk stratification. In patients with arrhythmias, ion disbalance may be more critical. We concluded that asymptomatic, uninjured adult and pediatric patients with normal initial ECG findings do not need continuous ECG monitoring and may be discharged home. Recommendations for high-risk patients and patients with mild ECG abnormalities at admission are less obvious.

Effect of acute CORticosteroids on conduction defects after Transcatheter Aortic Valve Implantation: the CORTAVI study.

AIMS: Conduction abnormalities, requiring a permanent pacemaker (PPM), are the most common electrical complications after transcatheter aortic valve implantation (TAVI). The exact mechanism for conduction system defects is not yet clear. The local inflammatory process and edema are thought to play a role in the development of electrical disorders. Corticosteroids are effective anti-inflammatory and antiedematous agents. We aim to investigate the potential protective effect of corticosteroids on conduction defects after TAVI. METHODS: This is a retrospective study of a single center. We analyzed 96 patients treated with TAVI. Thirty-two patients received oral prednisone 50 mg for 5 days after the procedure. This population was compared with the control group. All patients were followed up after 2 years. RESULTS: Of the 96 patients included, 32 (34%) were exposed to glucocorticoids after TAVI. No differences in age, preexisting right bundle branch block or left bundle branch block, or valve type were seen among patients exposed to glucocorticoids versus those who were unexposed. We observed no significant differences between the two groups in the overall frequency of new PPM implantations during hospitalization (12% vs. 17%, P  = 0.76). The incidence of atrioventricular block (AVB) (STx 9% vs. non-STx 9%, P  = 0.89), right bundle branch block (STx 6% vs. non-STx 11%, P  = 0.71), and left bundle branch block (STx 34% vs. non-STx 31%, P  = 0.9) was not significantly different between the STx and non-STx groups. At 2 years after TAVI, none of the patients had implanted PPM or had severe arrhythmias documented by 24-h Holter ECG or cardiac examination. CONCLUSION: Oral prednisone treatment does not appear to significantly reduce the incidence of AVB requiring acute PPM implantation after TAVI.

Conduction Disturbance After Transcatheter Aortic Valve Implantation With Self- or Balloon-Expandable Valve According to the Implantation Depth.

Membranous septum (MS) length, in conjunction with implantation depth (ID), is known as a determinant of conduction disturbance (CD) after transcatheter aortic valve implantation (TAVI). However, its impact might be dissimilar among valve types because each valve has a different platform. This study sought to investigate the different impacts of ID and MS length on the new-onset CD between ACURATE neo and SAPIEN 3. This study included patients without a previous permanent pacemaker implantation who underwent TAVI with ACURATE neo and SAPIEN 3 and divided them into 2 groups based on the ID according to MS length (deep and shallow implantation group). Deep implantation was defined as transcatheter heart valve implantation deeper than MS length. The primary endpoint was new-onset CD (new permanent pacemaker implantation or new-onset complete left bundle branch block). A total of 688 patients (deep implantation: n = 373, shallow implantation: n = 315) were identified as a study cohort. New-onset CD developed more frequently in the deep implantation group (16.6% vs 7.0%; p = 0.0001). Deep implantation was revealed as a predictor of new-onset CD. Moreover, deep implantation was significantly associated with new-onset CD after SAPIEN 3 implantation but not after ACURATE neo. Among patients with MS shorter than 2 mm, ACURATE neo was superior in terms of avoiding new-onset CD. In conclusion, the deep implantation was associated with new-onset CD after TAVI with SAPIEN 3 but not with ACURATE neo. These results may impact device selection in patients with a preexisting high risk of CD.

Novel p.Asp27Glu ACTA1 variant features congenital myopathy with finger flexor weakness, cardiomyopathy, and cardiac conduction defects.

Pathogenic variants in the skeletal muscle α-actin 1 gene (ACTA1) cause a spectrum of myopathies with clinical and myopathological diversity. Clinical presentations occur from the prenatal period to adulthood, commonly with proximal-predominant weakness and rarely preferential distal weakness. Myopathological findings are wide-ranging, with nemaline rods being most frequent. Associated cardiomyopathy is rare and conduction defects are not reported. We describe a family with congenital myopathy with prominent finger flexor weakness and cardiomyopathy with cardiac conduction defects. The proband, a 48-year-old Caucasian male, his 73-year-old mother, 41-year-old sister, and 19-year-old nephew presented with prominent finger flexor weakness on a background of neonatal hypotonia and delayed motor milestones. All had progressive cardiomyopathy with systolic dysfunction and/or left ventricular dilation. The proband and sister had intraventricular conduction delay and left anterior fascicular block, respectively. The mother had atrial fibrillation. Muscle biopsy in the proband and sister demonstrated congenital fiber-type disproportion and rare nemaline rods in the proband. A novel dominant variant in ACTA1 (c.81C>A, p.Asp27Glu) segregated within the family. This family expands the genotypic and phenotypic spectrum of ACTA1-related myopathy, highlighting preferential finger flexor involvement with cardiomyopathy and conduction disease. We emphasize early and ongoing cardiac surveillance in ACTA1-related myopathy.

Pacing induced cardiomyopathy: recognition and management.

Right ventricle (RV) apex continues to remain as the standard pacing site in the ventricle due to ease of implantation, procedural safety and lack of convincing evidence of better clinical outcomes from non-apical pacing sites. Electrical dyssynchrony resulting in abnormal ventricular activation and mechanical dyssynchrony resulting in abnormal ventricular contraction during RV pacing can result in adverse LV remodelling predisposing some patients for recurrent heart failure (HF) hospitalisation, atrial arrhythmias and increased mortality. While there are significant variations in the definition of pacing induced cardiomyopathy (PIC), combining both echocardiographic and clinical features, the most acceptable definition for PIC would be left ventricular ejection fraction (LVEF) of <50%, absolute decline of LVEF by ≥10% and/or new-onset HF symptoms or atrial fibrillation (AF) after pacemaker implantation. Based on the definitions used, the prevalence of PIC varies between 6% and 25% with overall pooled prevalence of 12%. While most patients undergoing RV pacing do not develop PIC, male sex, chronic kidney disease, previous myocardial infarction, pre-existing AF, baseline LVEF, native QRS duration, RV pacing burden, and paced QRS duration are the factors associated with increased risk for PIC. While conduction system pacing (CSP) using His bundle pacing and left bundle branch pacing appear to reduce the risk for PIC compared with RV pacing, both biventricular pacing and CSP may be used to effectively reverse PIC.

Brugada Syndrome: 30 Years of Scientific Ventures. / Síndrome de Brugada: 30 Anos de Aventura Científica.

Thirty years ago, a distinctly new clinical-electrocardiographic syndrome was described, today known as Brugada Syndrome (BrS). Typical treatment for this type of syndrome is electrocardiography with ST-segment elevation in the direct precordial derivations. The clinical presentation of the disease is highly variable: the patients can remain completely asymptomatic, but they can also develop episodes of syncope, atrial fibrillation (AF), sinus node dysfunction (SNF), conduction disorders, asystole, and ventricular fibrillation (VF). This disease is caused by mutations in the genes responsible for the potential action of cardiac cells. The most commonly involved gene is SCN5A, which controls the structure and function of the heart's sodium channel. The description of this new syndrome has shown highly positive implications in all fields of medicine.

Trinta anos atrás, uma nova síndrome clínico-eletrocardiográfica distinta foi descrita, agora conhecida como síndrome de Brugada (SBr). Típico para essa síndrome é o eletrocardiograma com supradesnivelamento do segmento ST nas derivações precordiais direitas. A apresentação clínica da doença é altamente variável: os pacientes podem permanecer completamente assintomáticos, mas também podem desenvolver episódios de síncope, fibrilação atrial (FA), síndrome do nódulo sinusal (SNS), distúrbios de condução, assistolia e fibrilação ventricular (FV). A doença é causada por mutações nos genes responsáveis pelo potencial de ação das células do coração. O gene mais frequentemente envolvido é o SCN5A, que controla a estrutura e função do canal de sódio cardíaco. A descrição dessa nova síndrome teve implicações muito positivas em todos os campos da medicina.

Role of genetic testing in young patients with idiopathic atrioventricular conduction disease.

AIMS: To investigate the role of genetic testing in patients with idiopathic atrioventricular conduction disease requiring pacemaker (PM) implantation before the age of 50 years. METHODS AND RESULTS: All consecutive PM implantations in Southern Switzerland between 2010 and 2019 were evaluated. Inclusion criteria were: (i) age at the time of PM implantation: < 50 years; (ii) atrioventricular block (AVB) of unknown aetiology. Study population was investigated by ajmaline challenge and echocardiographic assessment over time. Genetic testing was performed using next-generation sequencing panel, containing 174 genes associated to inherited cardiac diseases, and Sanger sequencing confirmation of suspected variants with clinical implication. Of 2510 patients who underwent PM implantation, 15 (0.6%) were young adults (median age: 44 years, male predominance) presenting with advanced AVB of unknown origin. The average incidence of idiopathic AVB computed over the 2010-2019 time window was 0.7 per 100 000 persons per year (95% CI 0.4-1.2). Most of patients (67%) presented with specific genetic findings (pathogenic variant) or variants of uncertain significance (VUS). A pathogenic variant of PKP2 gene was found in one patient (6.7%) with no overt structural cardiac abnormalities. A VUS of TRPM4, MYBPC3, SCN5A, KCNE1, LMNA, GJA5 genes was found in other nine cases (60%). Of these, three unrelated patients (20%) presented the same heterozygous missense variant c.2531G > A p.(Gly844Asp) in TRPM4 gene. Diagnostic re-assessment over time led to a diagnosis of Brugada syndrome and long-QT syndrome in two patients (13%). No cardiac events occurred during a median follow-up of 72 months. CONCLUSION: Idiopathic AVB in adults younger than 50 years is a very rare condition with an incidence of 0.7 per 100 000 persons/year. Systematic investigations, including genetic testing and ajmaline challenge, can lead to the achievement of a specific diagnosis in up to 20% of patients. Heterozygous missense variant c.2531G > A p.(Gly844Asp) in TRPM4 gene was found in an additional 20% of unrelated patients, suggesting possible association of the variant with the disease.

Cardiac Emerinopathy: A Nonsyndromic Nuclear Envelopathy With Increased Risk of Thromboembolic Stroke Due to Progressive Atrial Standstill and Left Ventricular Noncompaction.

BACKGROUND: Mutations in the nuclear envelope genes encoding LMNA and EMD are responsible for Emery-Dreifuss muscular dystrophy. However, LMNA mutations often manifest dilated cardiomyopathy with conduction disturbance without obvious skeletal myopathic complications. On the contrary, the phenotypic spectrums of EMD mutations are less clear. Our aims were to determine the prevalence of nonsyndromic forms of emerinopathy, which may underlie genetically undefined isolated cardiac conduction disturbance, and the etiology of thromboembolic complications associated with EMD mutations. METHODS: Targeted exon sequencing was performed in 87 probands with familial sick sinus syndrome (n=36) and a progressive cardiac conduction defect (n=51). RESULTS: We identified 3 X-linked recessive EMD mutations (start-loss, splicing, missense) in families with cardiac conduction disease. All 3 probands shared a common clinical phenotype of progressive atrial arrhythmias that ultimately resulted in atrial standstill associated with left ventricular noncompaction (LVNC), but they lacked early contractures and progressive muscle wasting and weakness characteristic of Emery-Dreifuss muscular dystrophy. Because the association of LVNC with EMD has never been reported, we further genetically screened 102 LVNC patients and found a frameshift EMD mutation in a boy with progressive atrial standstill and LVNC without complications of muscular dystrophy. All 6 male EMD mutation carriers of 4 families underwent pacemaker or defibrillator implantation, whereas 2 female carriers were asymptomatic. Notably, a strong family history of stroke observed in these families was probably due to the increased risk of thromboembolism attributable to both atrial standstill and LVNC. CONCLUSIONS: Cardiac emerinopathy is a novel nonsyndromic X-linked progressive atrial standstill associated with LVNC and increased risk of thromboembolism.

Cardiac Conduction Disorders as Markers of Cardiac Events in Myotonic Dystrophy Type 1.

Background Myotonic dystrophy type 1 involves cardiac conduction disorders. Cardiac conduction disease can cause fatal arrhythmias or sudden death in patients with myotonic dystrophy type 1. Methods and Results This study enrolled 506 patients with myotonic dystrophy type 1 (aged ≥15 years; >50 cytosine-thymine-guanine repeats) and was treated in 9 Japanese hospitals for neuromuscular diseases from January 2006 to August 2016. We investigated genetic and clinical backgrounds including health care, activities of daily living, dietary intake, cardiac involvement, and respiratory involvement during follow-up. The cause of death or the occurrence of composite cardiac events (ie, ventricular arrhythmias, advanced atrioventricular blocks, and device implantations) were evaluated as significant outcomes. During a median follow-up period of 87 months (Q1-Q3, 37-138 months), 71 patients expired. In the univariate analysis, pacemaker implantations (hazard ratio [HR], 4.35; 95% CI, 1.22-15.50) were associated with sudden death. In contrast, PQ interval ≥240 ms, QRS duration ≥120 ms, nutrition, or respiratory failure were not associated with the incidence of sudden death. The multivariable analysis revealed that a PQ interval ≥240 ms (HR, 2.79; 95% CI, 1.9-7.19, P<0.05) or QRS duration ≥120 ms (HR, 9.41; 95% CI, 2.62-33.77, P < 0.01) were independent factors associated with a higher occurrence of cardiac events than those observed with a PQ interval <240 ms or QRS duration <120 ms; these cardiac conduction parameters were not related to sudden death. Conclusions Cardiac conduction disorders are independent markers associated with cardiac events. Further investigation on the prediction of occurrence of sudden death is warranted.

Purkinje system hyperexcitability and ventricular arrhythmia risk in type 3 long QT syndrome.

BACKGROUND: Gain-of-function variants in the SCN5A-encoded Nav1.5 sodium channel cause type 3 long QT syndrome (LQT3) and multifocal ectopic Purkinje-related premature contractions. Although the Purkinje system is uniquely sensitive to the action potential-prolonging effects of LQT3-causative variants, the existence of additional Purkinje phenotype(s) in LQT3 is unknown. OBJECTIVE: The purpose of this study was to determine the prevalence and clinical implications of frequent fascicular/Purkinje-related premature ventricular contractions (PVCs) and short-coupled ventricular arrhythmias (VAs), suggestive of Purkinje system hyperexcitability (PSH), in a single-center LQT3 cohort. METHODS: A retrospective analysis of 177 SCN5A-positive patients was performed to identify individuals with a LQT3 phenotype. Available electrocardiographic, electrophysiology study, device, and genetic data from 91 individuals with LQT3 were reviewed for evidence of presumed fascicular PVCs and short-coupled VAs. The relationship between PSH and ventricular fibrillation events was assessed by Kaplan-Meier and Cox regression analyses. RESULTS: Overall, 30 of 91 patients with LQT3 (33%) exhibited evidence of presumed PSH (fascicular PVCs 30 of 30 [100%]; short-coupled VAs 17 of 30 [56%]). Kaplan-Meier and Cox regression analyses demonstrated an increased risk of ventricular fibrillation events in individuals with LQT3 and PSH (log-rank, P < .03; hazard ratio 3.95; 95% confidence interval 1.15-15.7; P = .03). Interestingly, variants in the voltage-sensing domain regions of Nav1.5 were more frequently observed in patients with LQT3 and PSH than those without (19 of 30 [63%] vs 9 of 61 [15%]; P < .0001). CONCLUSION: This study demonstrates that a discernible Purkinje phenotype is present in one-third of LQT3 cases and increases the risk of potentially lethal VAs. Further study is needed to determine whether a distinct cellular electrophysiology phenotype underlies this phenomenon.

Reduced Na+ current in Purkinje fibers explains cardiac conduction defects and arrhythmias in Duchenne muscular dystrophy.

Cardiac arrhythmias significantly contribute to mortality in Duchenne muscular dystrophy (DMD), a degenerative muscle disease triggered by mutations in the gene encoding for the intracellular protein dystrophin. A major source for the arrhythmias in patients with DMD is impaired ventricular impulse conduction, which predisposes for ventricular asynchrony, decreased cardiac output, and the development of reentrant mechanisms. The reason for ventricular conduction impairments and the associated arrhythmias in the dystrophic heart has remained unidentified. In the present study, we explored the hypothesis that dystrophin-deficient cardiac Purkinje fibers have reduced Na+ currents (INa), which would represent a potential mechanism underlying slowed ventricular conduction in the dystrophic heart. Therefore, by using a Langendorff perfusion system, we isolated Purkinje fibers from the hearts of adult wild-type control and dystrophin-deficient mdx mice. Enhanced green fluorescent protein (eGFP) expression under control of the connexin 40 gene allowed us to discriminate Purkinje fibers from eGFP-negative ventricular working cardiomyocytes after cell isolation. Finally, we recorded INa from wild-type and dystrophic mdx Purkinje fibers for comparison by means of the whole cell patch clamp technique. We found substantially reduced INa densities in mdx compared with wild-type Purkinje fibers, suggesting that dystrophin deficiency diminishes INa. Because Na+ channels in the Purkinje fiber membrane represent key determinants of ventricular conduction velocity, we propose that reduced INa in Purkinje fibers at least partly explains impaired ventricular conduction and the associated arrhythmias in the dystrophic heart.NEW & NOTEWORTHY Dystrophic cardiac Purkinje fibers have abnormally reduced Na+ current densities. This explains impaired ventricular conduction in the dystrophic heart.

Pearson marrow-pancreas syndrome with cardiac conduction abnormality necessitating prophylactic pacemaker implantation.

Pearson marrow-pancreas syndrome (PS), an exceedingly rare mitochondrial disorder, involves multiple systems including hematologic system and pancreas. Other mitochondrial disorders have been associated with progressive infrahisian block but this has not yet been described as a major feature of PS. We report a 7-year-old girl with classical features of PS and cardiac conduction defect. Her electrocardiogram revealed QRS prolongation with right bundle and left anterior fascicular blocks. Follow-up Holter revealed bifascicular block, alternating left and right bundle branch blocks, supraventricular tachycardia (with alternating bundles), and suspicion for nonsustained ventricular tachycardia. She underwent successful transvenous single-chamber ventricular pacemaker.

Comparison of current German and European practice in cardiac resynchronization therapy: lessons from the ESC/EHRA/HFA CRT Survey II.

INTRODUCTION: The European CRT Survey II was introduced to offer insights into CRT implantation practice in Europe. We compared the national data from the participating German centres with that of the other European countries with regard to differences in patient selection, implant results, and initial properties. METHODS AND RESULTS: 11,088 patients were enrolled in 288 centres from 42 countries between 2015 and 2017. Of these, 675 (6.1%) were included in 17 centres in Germany. Patients from Germany were older, had more comorbidities and more symptoms of heart failure (HF) than patients from other European countries. There were no differences with regard to HF aetiology and guideline-directed medical treatment was overall well implemented. There was a high use of CRT in patients with atrial fibrillation, even higher in German patients. CRT was most often applied due to HF with wide QRS complex (class I recommendation) but with relatively higher frequency in Germany due to HF with primary indication for an implantable cardioverter-defibrillator (class IIb) or a pacemaker with expected pacing dependency (class I). The overall implant success rate was high with some differences in the implant procedure. The use of remote monitoring was lower in Germany. CONCLUSION: This analysis from the European CRT Survey II overall shows good guideline adherence, high implantation success and a low rate of complications in daily practice. There are some regional differences in baseline characteristics, CRT indication, and procedural aspects. The use of remote monitoring in Germany lags behind other European countries.

Pre-hospital management of patients with chest pain and/or dyspnoea of cardiac origin. A position paper of the Acute Cardiovascular Care Association (ACCA) of the ESC.

Chest pain and acute dyspnoea are frequent causes of emergency medical services activation. The pre-hospital management of these conditions is heterogeneous across different regions of the world and Europe, as a consequence of the variety of emergency medical services and absence of specific practical guidelines. This position paper focuses on the practical aspects of the pre-hospital treatment on board and transfer of patients taken in charge by emergency medical services for chest pain and dyspnoea of suspected cardiac aetiology after the initial assessment and diagnostic work-up. The objective of the paper is to provide guidance, based on evidence, where available, or on experts' opinions, for all emergency medical services' health providers involved in the pre-hospital management of acute cardiovascular care.

Effect of Left Ventricular Conduction Delay on All-Cause and Cardiovascular Mortality (from the PRECISION Trial).

The prognosis associated with prolonged intraventricular conduction on electrocardiogram (ECG) remains uncertain. We aimed to compare clinical outcomes of narrow versus prolonged intraventricular conduction on ECG stratified by QRS morphology and cardiovascular disease (CVD) status. A post-hoc analysis was performed of the randomized-control PRECISION trial. Patients with centrally adjudicated, nonpaced baseline ECGs were included. QRS duration was classified narrow (≤100 ms) versus prolonged (>100 ms) with additional categorization into left (LBBB) or right (RBBB) bundle branch block or nonspecific intraventricular conduction delay (IVCD). IVCD was subclassified if left ventricular conduction delay (LVCD) was present (L-IVCD) or absent (O-IVCD). The primary outcome was adjudicated all-cause and cardiovascular (CV) mortality. Of 24,081 patients randomized, 22,067 (92%) were included with follow-up 34 ± 13 months. Study patients were 63 ± 9 years, 64% female, 75% Caucasian, 23% with established CVD. The prevalence of QRS prolongation was 5.6% (1,240): 760 right bundle branch block (3.4%), 313 LBBB (1.4%), and 161 IVCD (0.7%), 95 subclassified L-IVCD (0.4%). After adjustment, LBBB and L-IVCD were similarly associated with increased all-cause (LBBB: 2.3 [1.4 to 3.8], p = 0.001; L-IVCD: 4.0 [2.1 to 7.9], p <0.001) and CV (LBBB: 3.6 [2.0 to 6.5], p <0.001; L-IVCD 3.6 [1.3 to 9.7], p = 0.001) mortality. The presence of LVCD (LBBB or L-IVCD) was associated with all-cause (2.8 [1.8 to 4.2], p <0.001) and CV (3.6 [2.2 to 6.1], p <0.001) mortality exceeding the observed risks of coronary artery disease, left ventricular hypertrophy, or diabetes. The LVCD hazard persisted across QRS durations (100 to 120 vs >120 ms) and CVD status. In conclusion, LVCD, whether LBBB or L-IVCD, was strongly associated with increased mortality in patients with and at-risk for CVD.

Molecular and genetic insights into progressive cardiac conduction disease.

Progressive cardiac conduction disease (PCCD) is often a primarily genetic disorder, with clinical and genetic overlaps with other inherited cardiac and metabolic diseases. A number of genes have been implicated in PCCD pathogenesis with or without structural heart disease or systemic manifestations. Precise genetic diagnosis contributes to risk stratification, better selection of specific therapy and allows familiar cascade screening. Cardiologists should be aware of the different phenotypes emerging from different gene-mutations and the potential risk of sudden cardiac death. Genetic forms of PCCD often overlap or coexist with other inherited heart diseases or manifest in the context of multisystem syndromes. Despite the significant advances in the knowledge of the genetic architecture of PCCD and overlapping diseases, in a measurable fraction of PCCD cases, including in familial clustering of disease, investigations of known cardiac disease-associated genes fail to reveal the underlying substrate, suggesting that new causal genes are yet to be discovered. Here, we provide insight into genetics and molecular mechanisms of PCCD and related diseases. We also highlight the phenotypic overlaps of PCCD with other inherited cardiac and metabolic diseases, present unmet challenges in clinical practice, and summarize the available therapeutic options for affected patients.