2017 AHA/ACC/HRS Guideline for Management of Patients With Ventricular Arrhythmias and the Prevention of Sudden Cardiac Death: A Report of the American College of Cardiology/American Heart Association Task Force on Clinical Practice Guidelines and the Heart Rhythm Society

Progress and challenges in the treatment of cardiac amyloidosis: a review of the literature

Cardiac amyloidosis is a restrictive cardiomyopathy determined by the accumulation of amyloid, which is represented by misfolded protein fragments in the cardiac extracellular space. The main classification of systemic amyloidosis is determined by the amyloid precursor proteins causing a very heterogeneous disease spectrum, but the main types of amyloidosis involving the heart are light chain (AL) and transthyretin amyloidosis (ATTR). AL, in which the amyloid precursor is represented by misfolded immunoglobulin light chains, can involve almost any system carrying the worst prognosis among amyloidosis patients. This has however dramatically improved in the last few years with the increased usage of the novel therapies such as proteasome inhibitors and haematopoietic cell transplantation, in the case of timely diagnosis and initiation of treatment. The treatment for AL is directed by the haematologist working closely with the cardiologist when there is a significant cardiac involvement. Transthyretin (TTR) is a protein that is produced by the liver and is involved in the transportation of thyroid hormones, especially thyroxine and retinol binding protein. ATTR results from the accumulation of transthyretin amyloid in the extracellular space of different organs and systems, especially the heart and the nervous system. Specific therapies for ATTR act at various levels of TTR, from synthesis to deposition: TTR tetramer stabilization, oligomer aggregation inhibition, genetic therapy, amyloid fibre degradation, antiserum amyloid P antibodies, and antiserum TTR antibodies. Treatment of systemic amyloidosis has dramatically evolved over the last few years in both AL and ATTR, improving disease prognosis. Moreover, recent studies revealed that timely treatment can lead to an improvement in clinical status and in a regression of amyloid myocardial infiltration showed by imaging, especially by cardiac magnetic resonance, in both AL and ATTR. However, treating cardiac amyloidosis is a complex task due to the frequent association between systemic congestion and low blood pressure, thrombo-embolic and haemorrhagic risk balance, patient frailty, and generally poor prognosis. The aim of this review is to describe the current state of knowledge regarding cardiac amyloidosis therapy in this constantly evolving field, classified as treatment of the cardiac complications of amyloidosis (heart failure, rhythm and conduction disturbances, and thrombo-embolic risk) and the disease-modifying therapy.

Predictors of Sudden Cardiac Arrest Among Patients With Post-Myocardial Infarction Ejection Fraction Greater Than 35

Background

Sudden cardiac arrest (SCA) risk increases after myocardial infarction (MI) in patients with a reduced ejection fraction (EF). However, the risk factors for SCA among patients with a post‐MI EF >35% remain poorly understood.

Methods and Results

Using the Optum de‐identified electronic health record data set from 2008 to 2017, we identified patients with an incident MI diagnosis and troponin elevation who had a post‐MI EF >35% and underwent coronary angiography. Primary outcome was SCA within 1 year post‐MI. The database was divided into derivation (70%) and validation (30%) cohorts by random selection. Cox proportional hazard regression was used to generate and validate a risk prediction model. Among 31 286 patients with an MI (median age 64.1; 39% female; 87% White), 499 experienced SCA within 1 year post‐MI (estimated probability 1.8%). Lack of revascularization at MI, post‐MI EF <50%, Black race, renal failure, chronic obstructive pulmonary disease, antiarrhythmic therapy, and absence of beta blocker therapy were independent predictors of SCA. A multivariable model consisting of these variables predicted SCA risk (C‐statistic 0.73). Based on this model, the estimated annual probability of SCA was 4.4% (95% CI, 3.9–4.9) in the highest quartile of risk versus 0.6% (95% CI, 0.4–0.8) in the lowest quartile.

Conclusions

Patients with a post‐MI EF >35% have a substantial annual risk of SCA. A risk model consisting of acute coronary revascularization, EF, race, renal failure, chronic obstructive pulmonary disease, antiarrhythmic therapy, and beta blocker therapy can identify patients with higher risk of SCA, who may benefit from further risk stratification and closer monitoring.

Calcium and Heart Failure: How Did We Get Here and Where Are We Going?

The occurrence and prevalence of heart failure remain high in the United States as well as globally. One person dies every 30 s from heart disease. Recognizing the importance of heart failure, clinicians and scientists have sought better therapeutic strategies and even cures for end-stage heart failure. This exploration has resulted in many failed clinical trials testing novel classes of pharmaceutical drugs and even gene therapy. As a result, along the way, there have been paradigm shifts toward and away from differing therapeutic approaches. The continued prevalence of death from heart failure, however, clearly demonstrates that the heart is not simply a pump and instead forces us to consider the complexity of simplicity in the pathophysiology of heart failure and reinforces the need to discover new therapeutic approaches.

Management of Congenital Long-QT Syndrome: Commentary From the Experts

While published guidelines are useful in the care of patients with long-QT syndrome, it can be difficult to decide how to apply the guidelines to individual patients, particularly those with intermediate risk. We explored the diversity of opinion among 24 clinicians with expertise in long-QT syndrome. Experts from various regions and institutions were presented with 4 challenging clinical scenarios and asked to provide commentary emphasizing why they would make their treatment recommendations. All 24 authors were asked to vote on case-specific questions so as to demonstrate the degree of consensus or divergence of opinion. Of 24 authors, 23 voted and 1 abstained. Details of voting results with commentary are presented. There was consensus on several key points, particularly on the importance of the diagnostic evaluation and of β-blocker use. There was diversity of opinion about the appropriate use of other therapeutic measures in intermediate-risk individuals. Significant gaps in knowledge were identified.

CMR-Based Risk Stratification of Sudden Cardiac Death and Use of Implantable Cardioverter-Defibrillator in Non-Ischemic Cardiomyopathy

Non-ischemic cardiomyopathy (NICM) is one of the most important entities for arrhythmias and sudden cardiac death (SCD). Previous studies suggest a lower benefit of implantable cardioverter–defibrillator (ICD) therapy in patients with NICM as compared to ischemic cardiomyopathy (ICM). Nevertheless, current guidelines do not differentiate between the two subgroups in recommending ICD implantation. Hence, risk stratification is required to determine the subgroup of patients with NICM who will likely benefit from ICD therapy. Various predictors have been proposed, among others genetic mutations, left-ventricular ejection fraction (LVEF), left-ventricular end-diastolic volume (LVEDD), and T-wave alternans (TWA). In addition to these parameters, cardiovascular magnetic resonance imaging (CMR) has the potential to further improve risk stratification. CMR allows the comprehensive analysis of cardiac function and myocardial tissue composition. A range of CMR parameters have been associated with SCD. Applicable examples include late gadolinium enhancement (LGE), T1 relaxation times, and myocardial strain. This review evaluates the epidemiological aspects of SCD in NICM, the role of CMR for risk stratification, and resulting indications for ICD implantation.

Ventricular tachycardia in patients undergoing 24-h Holter monitoring as preoperative evaluation for noncardiac surgery

The incidence of ventricular tachycardia (VT) in preoperative evaluation for noncardiac surgery in general hospitals has not been established. The aim of this study was to determine the incidence of VT, characteristics of patients with VT, characteristics of VT, and significance of VT in patients undergoing 24-h Holter monitoring as preoperative evaluation for noncardiac surgery. In 601 patients, VT was detected in 46 patients (7.7%). In patients with VT, left ventricular ejection fraction (LVEF) was lower (62.6 ± 9.3% vs. 66.6 ± 8.9%, p = 0.003), and B-type natriuretic peptide (BNP) was higher compared with patients without VT (median, 52.5 pg/mL vs. 32.8 pg/mL, p = 0.02). The maximum number of consecutive beats of VT was more frequent in the patients with LVEF < 50% than in the patients with LVEF ≥ 50% (median, 11.5 beats vs. 3.0 beats, p = 0.01). Forty patients (87%) underwent scheduled surgery without major complications.

Myocardial Fibrosis as a Predictor of Ventricular Arrhythmias in Patients With Non-ischemic Cardiomyopathy

BACKGROUND/AIM

The aim of the study was to assess the relationship between myocardial fibrosis characteristics (percentage, localization, heterogeneity), evaluated by a non-invasive method such as cardiac magnetic resonance (CMR), with the extrasystolic ventricular arrhythmia in patients with non-ischemic cardiomyopathy.

PATIENTS AND METHODS

The study prospectively included 173 consecutive patients who underwent electrocardiogram Holter monitoring, transthoracic echocardiography and CMR with late gadolinium enhancement (LGE).

RESULTS

In univariate analysis, both the presence (OR=1.05, 95% CI=1.01-1.09; p=0.015), the percentage of fibrosis >15% (p=0.018), the septum size, the fibrosis in either lateral or septal walls (p=0.004), as well as fibrosis in the midwall (p=0.019) were statistically significant higher in the group with extrasystolic arrhythmia. After adjustment, the percentage of fibrosis >15%, had higher odds of extra systolic arrhythmia [OR=3.78 (95% CI=1.52-10.62, p=0.007)].

CONCLUSION

The presence, percentage, and localisation of left ventricle myocardial fibrosis characterized by LGE-CMR was associated with ventricular arrhythmias.

Electrical Storm With Incessant Ventricular Tachycardia in a COVID-19 Patient: Review of Current Evidence

Coronavirus disease 2019 (COVID-19) is associated with various cardiovascular manifestations, including myocarditis, myocardial infarction, and arrhythmias. A prothrombotic state is the primary underlying pathogenic mechanism. While cardiac arrhythmias manifest more commonly amongst critically ill COVID-19 populations, ventricular arrhythmias have been reported only in few cases. This report describes a case of a 95-year-old African American man with COVID-19, who developed sustained monomorphic ventricular tachycardia, which progressed to an electrical storm. The case highlights the importance of high clinical suspicion, early recognition of electrical abnormalities in patients with active COVID-19 infection, and its ability to precipitate fatal ventricular arrhythmia. Also, we provide a literature review on the electrical storm in COVID-19 patients, highlighting the pathophysiologic mechanisms and the management of this deadly arrhythmia.

Noncompaction Cardiomyopathy-History and Current Knowledge for Clinical Practice

Noncompaction cardiomyopathy (NCCM) has gained increasing attention over the past twenty years, but in daily clinical practice NCCM is still rarely considered. So far, there are no generally accepted diagnostic criteria and some groups even refuse to acknowledge it as a distinct cardiomyopathy, and grade it as a variant of dilated cardiomyopathy or a morphological trait of different conditions. A wide range of morphological variants have been observed even in healthy persons, suggesting that pathologic remodeling and physiologic adaptation have to be differentiated in cases where this spongy myocardial pattern is encountered. Recent studies have uncovered numerous new pathogenetic and pathophysiologic aspects of this elusive cardiomyopathy, but a current summary and evaluation of clinical patient management are still lacking, especially to avoid mis- and overdiagnosis. Addressing this issue, this article provides an up to date overview of the current knowledge in classification, pathogenesis, pathophysiology, epidemiology, clinical manifestations and diagnostic evaluation, including genetic testing, treatment and prognosis of NCCM.

State-of-the-art narrative review: multimodality imaging in electrophysiology and cardiac device therapies

Cardiac electrophysiology procedures have evolved to provide improvement in morbidity and mortality for many patients. Cardiac resynchronization therapy (CRT), implantable cardioverter/defibrillator (ICD) placement and lead extraction procedures are proven procedures, associated with significant reductions in patient morbidity and mortality as well as improved quality of life. The applications and optimization of these therapies are an evolving field. The optimal use and outcomes of cardiac electrophysiology procedures require a multidisciplinary approach to patient selection, device selection, and procedural planning. Cardiac imaging using echocardiography plays a key role in selection of patients for CRT therapy, for guidance of left ventricular (LV) lead placement, and for optimization of atrioventricular pacing delays in patients with CRT. Cardiac computed tomography (CT) is an important tool in assessment of lead perforation, as well as assessing risk of lead extraction and procedural planning. Cardiac magnetic resonance imaging (MRI) is an important adjunct to transthoracic echocardiography for patient selection and risk stratification for defibrillator therapy for multiple disease states including ischemic cardiomyopathy, hypertrophic cardiomyopathy, cardiac sarcoidosis, and arrhythmogenic right ventricular cardiomyopathy (ARVC). Cardiac positron emission tomography (PET) is a useful adjunct to the diagnosis of device infections as well as inflammatory conditions including cardiac sarcoidosis. Our review attempts to summarize the contemporary roles of multimodality imaging in CRT therapy, ICD therapy and lead extraction therapy.

Expert consensus on acute management of ventricular arrhythmias - VT network Austria

The Arrhythmia Working Group of the Austrian Society of Cardiology (ÖKG) has set the goal of systematically structuring and organizing the acute care of patients with ventricular arrhythmias (VA), i.e. ventricular tachycardia (VT) or ventricular fibrillation (VF) in Austria. Within a consensus paper, national recommendations on the basic diagnostic work-up of VA (12-lead ECG, medical history, family history, laboratory analyses, echocardiography, search for reversible causes, ICD interrogation), as well as further medical treatment and therapeutic measures (indication of coronary angiography, ablation therapy) are established. Since acute ablation of VT is indicated in the current ESC guidelines as a class IB indication for scar-associated incessant VT or electrical storm (ES; ≥ 3 ICD therapies in 24 h) as well as for ischemic cardiomyopathy (iCMP) with recurrent ICD shocks, organizational measures must be taken to ensure that these guidelines can be implemented. Therefore, a VT network will be established covering all areas in Austria, consisting of primary and secondary VT centers. Organizational aspects of an acute VT network are defined and should subsequently be implemented by the participating hospitals. All electrophysiologic centers in Austria that deal with VT ablation are to be integrated into the network in the medium-term. Centers that co-operate in the network are divided into primary and secondary VT centers according to predefined criteria.

Cardiac sarcoidosis: Two case reports

The clinical presentation of cardiac sarcoidosis is variable. We report two cases of cardiac sarcoidosis to highlight the varied clinical presentations and diagnostic challenges in our setting, and encourage the consideration of sarcoidosis as a differential in unexplained arrhythmias and heart failure.

Diagnostic Impact of Repeated Expert Review & Long-Term Follow-Up in Determining Etiology of Idiopathic Cardiac Arrest

Background

Recognizing the etiology of sudden cardiac arrest (SCA) has an enormous impact on the management of victims and their immediate families. A significant proportion of SCA survivors with a structurally normal heart are not offered a diagnosis and there is no clear consensus on the type and duration of follow‐up. We aimed to assess the utility of a multidisciplinary approach in optimizing diagnosis of cardiac arrest etiology during follow‐up.

Methods and Results

We retrospectively assessed 327 consecutive SCA survivors (mean age 61.9±16.2 years, 80% men) who underwent secondary prevention implantable cardioverter defibrillators between May 2015 and November 2018. The initial diagnosis was recorded at the time of admission and follow‐up diagnosis was deduced from subsequent clinic records, investigations, and outcomes of multidisciplinary team meetings. Structural heart disease accounted for 282 (86%) of SCAs. Forty‐five (14%) patients had a structurally normal heart and underwent comprehensive testing and follow‐up (mean duration 93±52 weeks). On initial evaluation, 14/45 (31%) of these received a diagnosis, rising to 29/45 (64%) with serial reviews during follow‐up. Discussion in multidisciplinary team meetings and imaging reassessment accounted for 47% of new diagnoses. No additional diagnoses were made beyond 96 weeks. Nineteen (5.8%) fatalities occurred in the entire cohort, exclusively in patients with structural heart disease.

Conclusions

Systematic comprehensive testing combined with multidisciplinary expert team review of SCA survivors without structural heart disease improves the yield and time to diagnosis compared with previously published studies. This approach has positive implications in the management of SCA survivors and their families.

Does the Age of Sudden Cardiac Death in Family Members Matter in Brugada Syndrome?

Background Brugada syndrome is an inherited cardiac channelopathy associated with major arrhythmic events (MAEs). The presence of a positive family history of sudden cardiac death (SCD) as a risk predictor of MAE remains controversial. We aimed to examine the association between family history of SCD and MAEs stratified by age of SCD with a systematic review and meta-analysis. Methods and Results We searched the databases of MEDLINE and EMBASE from January 1992 to January 2020. Data from each study were combined using the random-effects model. Fitted metaregression was performed to evaluate the association between the age of SCD in families and the risk of MAE. Twenty-two studies from 2004 to 2019 were included in this meta-analysis involving 3386 patients with Brugada syndrome. The overall family history of SCD was not associated with increased risk of MAE in Brugada syndrome (pooled odds ratio [OR], 1.11; 95% CI, 0.82-1.51; P=0.489, I²=45.0%). However, a history of SCD in family members of age younger than 40 years of age did increase the risk of MAE by ≈2-fold (pooled OR, 2.03; 95% CI, 1.11-3.73; P=0.022, I²=0.0%). When stratified by the age of cut point at 50, 45, 40, and 35 years old, a history of SCD in younger family member was significantly associated with a higher risk of MAE (pooled OR, 0.49, 1.30, 1.51, and 2.97, respectively; P=0.046). Conclusions A history of SCD among family members of age younger than 40 years was associated with a higher risk of MAE.

Cardiac Resynchronization Therapy With or Without Defibrillation in Patients With Nonischemic Cardiomyopathy: A Systematic Review and Meta-Analysis

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The Defibrillation Conundrum: New Insights into the Mechanisms of Shock-Related Myocardial Injury Sustained from a Life-Saving Therapy

Implantable cardiac defibrillators (ICDs) are recommended to prevent the risk of sudden cardiac death. However, shocks are associated with an increased mortality with a dose response effect, and a strategy of reducing electrical therapy burden improves the prognosis of implanted patients. We review the mechanisms of defibrillation and its consequences, including cell damage, metabolic remodeling, calcium metabolism anomalies, and inflammatory and pro-fibrotic remodeling. Electrical shocks do save lives, but also promote myocardial stunning, heart failure, and pro-arrhythmic effects as seen in electrical storms. Limiting unnecessary implantations and therapies and proposing new methods of defibrillation in the future are recommended.

Funding of Studies Supporting IA Guideline Recommendations in Cardiovascular Medicine-A Systematic Review

Each guideline recommendation from the American Heart Association and the American College of Cardiology includes an indication of the level of supporting evidence and the associated strength of recommendation with “IA” recommendations representing those with the highest quality supporting evidence and the least amount of uncertainty for benefit. In this analysis, study type and funding sources were systematically tabulated across these IA guideline recommendations over the past 5 years. Nearly half of studies supporting IA guideline recommendations were randomized controlled trials (45%). Overall, about one third of studies supporting IA recommendations were publicly funded (34.9%) with slightly more funded through industry sources (43.5%). Funding sources varied based on the type of intervention being studied with randomized controlled trials of device, diagnostic, and pharmacological interventions reflecting predominantly industry‐funded studies. Over time, studies supporting IA cardiology guideline are funded by industry about twice as often as public sources. Thus, data of adequate quality to support cardiovascular guideline recommendations come from a variety of sources.

Plasma microrna expression profile for reduced ejection fraction in dilated cardiomyopathy

The left ventricular (LV) ejection fraction (EF) is key to prognosis in dilated cardiomyopathy (DCM). Circulating microRNAs have emerged as reliable biomarkers for heart diseases, included DCM. Clinicians need improved tools for greater clarification of DCM EF categorization, to identify high-risk patients. Thus, we investigated whether microRNA profiles can categorize DCM patients based on their EF. 179-differentially expressed circulating microRNAs were screened in two groups: (1) non-idiopathic DCM; (2) idiopathic DCM. Then, 26 microRNAs were identified and validated in the plasma of ischemic-DCM (n = 60), idiopathic-DCM (n = 55) and healthy individuals (n = 44). We identified fourteen microRNAs associated with echocardiographic variables that differentiated idiopathic DCM according to the EF degree. A predictive model of a three-microRNA (miR-130b-3p, miR-150-5p and miR-210-3p) combined with clinical variables (left bundle branch block, left ventricle end-systolic dimension, lower systolic blood pressure and smoking habit) was obtained for idiopathic DCM with a severely reduced-EF. The receiver operating characteristic curve analysis supported the discriminative potential of the diagnosis. Bioinformatics analysis revealed that miR-150-5p and miR-210-3p target genes might interact with each other with a high connectivity degree. In conclusion, our results revealed a three-microRNA signature combined with clinical variables that highly discriminate idiopathic DCM categorization. This is a potential novel prognostic biomarker with high clinical value.

Detecting Digoxin Toxicity by Artificial Intelligence-Assisted Electrocardiography

Although digoxin is important in heart rate control, the utilization of digoxin is declining due to its narrow therapeutic window. Misdiagnosis or delayed diagnosis of digoxin toxicity is common due to the lack of awareness and the time-consuming laboratory work that is involved. Electrocardiography (ECG) may be able to detect potential digoxin toxicity based on characteristic presentations. Our study attempted to develop a deep learning model to detect digoxin toxicity based on ECG manifestations. This study included 61 ECGs from patients with digoxin toxicity and 177,066 ECGs from patients in the emergency room from November 2011 to February 2019. The deep learning algorithm was trained using approximately 80% of ECGs. The other 20% of ECGs were used to validate the performance of the Artificial Intelligence (AI) system and to conduct a human-machine competition. Area under the receiver operating characteristic curve (AUC), sensitivity, and specificity were used to evaluate the performance of ECG interpretation between humans and our deep learning system. The AUCs of our deep learning system for identifying digoxin toxicity were 0.912 and 0.929 in the validation cohort and the human-machine competition, respectively, which reached 84.6% of sensitivity and 94.6% of specificity. Interestingly, the deep learning system using only lead I (AUC = 0.960) was not worse than using complete 12 leads (0.912). Stratified analysis showed that our deep learning system was more applicable to patients with heart failure (HF) and without atrial fibrillation (AF) than those without HF and with AF. Our ECG-based deep learning system provides a high-accuracy, economical, rapid, and accessible way to detect digoxin toxicity, which can be applied as a promising decision supportive system for diagnosing digoxin toxicity in clinical practice.

2021 ACC/AHA Key Data Elements and Definitions for Heart Failure: A Report of the American College of Cardiology/American Heart Association Task Force on Clinical Data Standards (Writing Committee to Develop Clinical Data Standards for Heart Failure)

Supplemental Digital Content is available in the text.

A Novel Model Based on Spatial and Morphological Domains to Predict the Origin of Premature Ventricular Contraction

Pace mapping is commonly used to locate the origin of ventricular arrhythmias, especially premature ventricular contraction (PVC). However, this technique relies on clinicians’ ability to rapidly interpret ECG data. To avoid time-consuming interpretation of ECG morphology, some automated algorithms or computational models have been explored to guide the ablation. Inspired by these studies, we propose a novel model based on spatial and morphological domains. The purpose of this study is to assess this model and compare it with three existing models. The data are available from the Experimental Data and Geometric Analysis Repository database in which three in vivo PVC patients are included. To measure the hit rate (A hit occurs when the predicted site is within 15 mm of the target) of different algorithms, 47 target sites are tested. Moreover, to evaluate the efficiency of different models in narrowing down the target range, 54 targets are verified. As a result, the proposed algorithm achieves the most hits (37/47) and fewest misses (9/47), and it narrows down the target range most, from 27.62 ± 3.47 mm to 10.72 ± 9.58 mm among 54 target sites. It is expected to be applied in the real-time prediction of the origin of ventricular activation to guide the clinician toward the target site.

Subepicardial aneurysm with free wall rupture and its successful surgical intervention: a case report

Background

Subepicardial aneurysm (SEA) is an uncommon but potentially fatal complication of acute myocardial infarction (MI) associated with an increased risk of free wall rupture (FWR) leading to sudden death. We describe a rare case of a silent myocardial infarction complicated by SEA and subsequent FWR, resulting in cardiac tamponade.

Case summary

A 68-year-old man with no previous chest symptoms presented with syncope. Cardiac computed tomography incidentally revealed a small aneurysmal cavity at the inferolateral wall of the left ventricle, which was overlooked on initial transthoracic echocardiography. Coronary angiography demonstrated a narrowed first obtuse marginal branch with coronary slow flow, suggesting that spontaneous recanalization of the occluded obtuse marginal branch induced SEA and subsequent FWR. The patient underwent an emergency left ventricular aneurysm repair. The post-operative course was uneventful, and the patient was discharged from the hospital on post-operative day 20.

Discussion

This case emphasizes the importance of prompt detection and surgical intervention for SEA. Subepicardial aneurysm should be suspected in patients with pericardial effusion and suspected MI. Cardiac computed tomography is not only useful in the detection of such cases but also facilitates the development of a successful surgical strategy.

Arrhythmias in Cardiac Sarcoidosis Bench to Bedside: A Case-Based Review

Cardiac sarcoidosis is a component of an often multiorgan granulomatous disease of still uncertain cause. It is being recognized with increasing frequency, mainly as the result of heightened awareness and new diagnostic tests, specifically cardiac magnetic resonance imaging and ¹⁸F-fluorodeoxyglucose positron emission tomography scans. The purpose of this case-based review is to highlight the potentially life-saving importance of making the early diagnosis of cardiac sarcoidosis using these new tools and to provide a framework for the optimal care of patients with this disease. We will review disease mechanisms as currently understood, associated arrhythmias including conduction abnormalities, and atrial and ventricular tachyarrhythmias, guideline-directed diagnostic criteria, screening of patients with extracardiac sarcoidosis, and the use of pacemakers and defibrillators in this setting. Treatment options, including those related to heart failure, and those which may help clarify disease mechanisms are included.

Premature ventricular contractions of the right ventricular outflow tract: is there an incipient underlying disease? New insights from a speckle tracking echocardiography study

Context

Premature ventricular contractions (PVCs) originating in the right ventricular outflow tract (RVOT) are traditionally considered idiopathic and benign. Echocardiographic conventional measurements are typically normal.

Aims

To assess whether right ventricle longitudinal strain, determined by two-dimensional speckle tracking echocardiography, differ between RVOT PVCs patients (treated with catheter ablation) and healthy controls.

Methods

We retrospectively selected patients with PVCs from the RVOT who underwent electrophysiological study and catheter ablation between 2016 and 2019. Patients with documented structural heart disease were excluded. Transthoracic echocardiography was performed and right ventricle global longitudinal strain (RV-GLS), free wall longitudinal strain (RVFW-LS) and left ventricle global longitudinal strain (LV-GLS) were determined as well as conventional ultrasound measurements of RV and LV function.

Results

We studied 21 patients with RVOT PVCs and 13 controls. Patients with PVCs from the RVOT had lower values of RV-GLS and RVFW-LS compared with the control group (−19.4% versus −22.5%, P = 0.015 and −22.1% versus −25.5, P = 0.041, respectively). They also had lower values of LV-GLS, although still within the normal range (−19.1% versus −20.9%, P = 0.047). Regarding RVOT PVCs patients only, RV-GLS and RVFW-LS had no correlation with the PVCs burden prior to catheter ablation and they did not differ between the patients in whom the catheter ablation was successful and those in whom it was not. RV-GLS also had a positive correlation with RVOT proximal diameter (r = 0.487, P = 0.025).

Conclusions

In this group of RVOT PVCs patients, we found worse RV longitudinal strain values (and therefore sub-clinical myocardial dysfunction) when compared to healthy controls.

Cardiac Imaging for Risk Assessment of Malignant Ventricular Arrhythmias in Patients With Mitral Valve Prolapse

Recent studies have described the occurrence of complex ventricular arrhythmias and sudden cardiac death among patients with mitral valve prolapse (MVP). The reported incidence rate of sudden cardiac death or ventricular tachycardia is about 1–1.5% among patients with MVP. Various imaging markers have been associated with this increased risk, including mitral annular disjunction, replacement fibrosis by late gadolinium enhancement, and mechanical dispersion. In this review, we briefly discuss how multimodality cardiac imaging can be applied to identify MVP patients with high risk of sudden cardiac death and complex ventricular arrhythmias.

Hyperhomocysteinemia and Cardiovascular Disease: Is the Adenosinergic System the Missing Link?

The influence of hyperhomocysteinemia (HHCy) on cardiovascular disease (CVD) remains unclear. HHCy is associated with inflammation and atherosclerosis, and it is an independent risk factor for CVD, stroke and myocardial infarction. However, homocysteine (HCy)-lowering therapy does not affect the inflammatory state of CVD patients, and it has little influence on cardiovascular risk. The HCy degradation product hydrogen sulfide (H2S) is a cardioprotector. Previous research proposed a positive role of H2S in the cardiovascular system, and we discuss some recent data suggesting that HHCy worsens CVD by increasing the production of H2S, which decreases the expression of adenosine A2A receptors on the surface of immune and cardiovascular cells to cause inflammation and ischemia, respectively.

Electrical Substrate Ablation for Refractory Ventricular Fibrillation: Results of the AVATAR Study

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Secondary Prevention of Potentially Life-Threatening Arrhythmia Using Implantable Cardioverter Defibrillators in Patients with Biopsy-Proven Viral Myocarditis and Preserved Ejection Fraction

BACKGROUND

Arrhythmia and sudden cardiac death (SCD) are known complications of acute viral myocarditis, regardless of ejection fraction (EF) at presentation. Whether such complications confer long-term risk is unknown, especially in those who present with preserved left ventricular (LV) function. No guidelines exist to the long-term reduction of arrhythmic death in such patients.

METHOD

In this retrospective study, we analyzed the long-term results of implantable cardioverter defibrillator (ICD) treatment in patients after an acute phase of myocarditis with life-threatening arrhythmia.

RESULTS

We identified 51 patients who had ICDs implanted following life-threatening arrhythmia presentation of confirmed acute viral myocarditis, despite preserved LVEF. Overall, 72.5% of patients had a clinical history of chest pain and viral infection with fever. Viral myocarditis was confirmed by cardiac magnetic resonance imaging (all had late enhancement) plus endomyocardial biopsies (most frequent were Epstein-Barr virus 29.4%, adenovirus 17.6%, and Coxsackie 17.6%), and 88.2% were discharged on anti-arrhythmic drugs. Overall, 12 patients (23.5%) required ICD intervention within the first 3 months, a further 7 patients (37.3% overall) between 3 and 12 months, and a further 12 patients (60.8% overall) until 58 months. During the follow-up, 3 of 51 patients (5.9%) died-deaths were due to cardiac events (n = 1), fatal infection (n = 1), and car accidents (n = 1). Of the 31 patients who had ventricular tachycardias after the acute phase of myocarditis, 11 needed radiofrequency ablation due to a high number of events or electrical storm. No baseline variables were identified that would serve as a basis for risk stratification.

CONCLUSION

Malignant arrhythmic events due to viral myocarditis are potential predictors of future SCD in patients not only with a reduced but also with a preserved EF.

Pathophysiology and Acute Management of Tachyarrhythmias in Pheochromocytoma: JACC Review Topic of the Week

Pheochromocytomas, arising from chromaffin cells, produce catecholamines, epinephrine and norepinephrine. The tumor biochemical phenotype is defined by which of these exerts the greatest influence on the cardiovascular system when released into circulation in high amounts. Action on the heart and vasculature can cause potentially lethal arrhythmias, often in the setting of comorbid blood pressure derangements. In a review of electrocardiograms obtained on pheochromocytoma patients (n = 650) treated at our institution over the last decade, severe and refractory sinus tachycardia, atrial fibrillation, and ventricular tachycardia were found to be the most common or life-threatening catecholamine-induced tachyarrhythmias. These arrhythmias, arising from catecholamine excess rather than from a primary electrophysiologic substrate, require special considerations for treatment and complication avoidance. Understanding the synthesis and release of catecholamines, the adrenoceptors catecholamines bind to, and the cardiac and vascular response to epinephrine and norepinephrine underlies optimal management in catecholamine-induced tachyarrhythmias.

Absence of shock therapy related to improper sensing of noise on the defibrillation test during subcutaneous implantable cardioverter-defibrillator implantation: a case report

Background 

Subcutaneous implantable cardioverter–defibrillator (S-ICD) represents an efficient alternative to transvenous ICD in patients who do not require pacing. The intraoperative defibrillation test (DFT) is recommended during S-ICD implantation to confirm appropriate sensing and successful 65-J termination of induced ventricular fibrillation (VF). However, few cases of oversensing of noise inhibiting therapies have been reported.

Case summary 

We report the case of a 50-year-old man who underwent S-ICD implantation for secondary prevention of sudden cardiac death. Immediately after S-ICD implantation, VF was induced using a 50-Hz burst; however, shock was not delivered owing to sustained noise on the electrogram in the primary vector. Therefore, an external rescue shock was needed at 150 J. We changed the sensing vector from primary to secondary and performed a second DFT. The S-ICD could deliver an appropriate shock and was able to successfully terminate VF without noise markers in the secondary vector. During the second DFT, one back-up pacing was delivered after the shock; the sensing vector then automatically switched from the secondary to the alternate vector. However, noise was observed in the alternate vector despite sinus rhythm restoration.

Discussion 

The present case demonstrated that noise was recorded in two different vectors during DFT, possibly supporting the hypothesis that the muscle spasm of the diaphragm induced by the 50-Hz burst causes oversensing of noise by the S-ICD.

Prognosis of Japanese Patients With Coronary Artery Disease Who Underwent Implantable Cardioverter Defibrillator Implantation - The JID-CAD Study

Background: There has been no large multicenter clinical trial on the prognosis of implantable cardioverter defibrillator (ICD) or cardiac resynchronization therapy with a defibrillator (CRT-D) in Japanese patients with coronary artery disease (CAD). The aim of the present study was to compare differences in the prognoses of Japanese patients with CAD between primary and secondary prevention, and to identify potential predictors of prognosis.

Methods and Results: We investigated 392 CAD patients (median age 69 years, 90% male) treated with ICD/CRT-D enrolled in the Japan Implantable Devices in CAD (JID-CAD) Registry. The primary endpoint was all-cause death, and the secondary endpoint was appropriate ICD therapies. Endpoints were assessed by dividing patients into primary prevention (n=165) and secondary prevention (n=227) groups. The mean (±SD) follow-up period was 2.1±0.9 years. The primary endpoint was similar in the 2 groups (P=0.350).

Conclusions: The mortality rate in Japanese patients with CAD who underwent ICD/CRT-D implantation as primary prevention was not lower than that of patients who underwent ICD/CRT-D implantation as secondary prevention, despite the lower cardiac function in the patients undergoing ICD/CRT-D implantation as primary prevention.

Factors and outcomes associated with improved left ventricular systolic function in patients with cardiomyopathy

BACKGROUND

Many patients in the Sudden Cardiac Death in Heart Failure Trial (SCD-HeFT) had a significant improvement (> 10%) in the left ventricular ejection fraction (LVEF) during the course of the study, but the factors and outcomes associated with such improvement are uncertain.

METHODS

We examined factors and rates of mortality, cause-specific mortality, and implantable cardioverter-defibrillator (ICD) shocks associated with improvement in LVEF by analyzing patients in the SCD-HeFT who were randomized to placebo or an ICD and who had an LVEF checked during follow-up.

RESULTS

During a median follow-up of 3.99 years, of 837 patients who had at least two follow-up LVEF measurements, 276 (33%) patients had > 10% improvement in LVEF and 561 (67%) patients had no significant change in LVEF. Factors significantly associated with LVEF improvement included female sex, white race, history of hypertension, a QRS duration < 120 ms, and beta-blocker use. Improvement in LVEF was associated with a significant improvement in survival. There was no significant association between improvement in LVEF and cause-specific death, but there was a significant association between improvement in LVEF and reduced risk of receiving appropriate ICD shocks.

CONCLUSIONS

About a third of patients in this analysis, who were randomized to placebo or an ICD in SCD-HeFT, had a significant improvement in LVEF during follow-up; improvement in LVEF was associated with improved survival but not with cause-specific death, and with decreased likelihood of receiving appropriate ICD shocks.

Frequent premature ventricular contractions. Association of burden and complexity with prognosis according to the presence of structural heart disease

INTRODUCTION

Premature ventricular contractions (PVC) have been associated with mortality and heart failure (HF) regardless the presence of structural heart disease (SHD). The aim of this study was assessing the impact of burden and complexity of PVCs on prognosis, according to presence of SHD.

METHODS

312 patients were retrospectively evaluated out of 1967 consecutive patients referred for 24-hr Holter at a single hospital, with a PVC count >1% of total beats. Two groups with and without SHD. PVC burden (PVC%), presence of complex forms, incidence of all-cause death, combined outcomes of all-cause death and cardiovascular hospitalizations, HF death and HF hospitalizations and, sudden death (SD) or hospitalizations due to ventricular arrhythmias (VA)were assessed.

RESULTS

Premature ventricular contraction burden was 2.7 (IQR: 1.6-6.7). SHD patients had more polymorphic PVCs, 77% versus 65%, p = .022, triplets and episodes of non-sustained ventricular tachycardia (NSVT): 44% versus 27%, p = .002; 30% versus 12%, p < .0001. In idiopathic patients, a PVC% in the third quartile was independently associated with all-cause mortality hazard ratio (HR) 2.288 (1.042-5.026) p = .039, but not in SHD. The complexity of the PVCs was not independently associated with outcomes in both groups. In SHD group, NSVT was associated with lower survival free from SD and VA hospitalizations, p = .028; after multivariable, there was a trend for a higher arrhythmic outcome with NSVT, HR 3.896 (0.903-16.81) p = .068.

CONCLUSION

Premature ventricular contractions in SHD showed more complex patterns. In idiopathic patients, a higher PVC count was associated with higher mortality but not is SHD patients. Complexity was not independently associated with worse prognosis.

The AED Project: Multiorganization Collaboration to Streamline Automatic External Defibrillator Data in Out-of-Hospital Cardiac Arrests

Background

In patients with out-of-hospital cardiac arrest (OHCA), automated external defibrillator (AED) devices contain valuable data about the patient’s initial rhythm. The retrieval process was previously without protocol, despite its critical role in the patient journey.

Methods

Through a Plan-Do-Study-Act model, the cardiology department at Royal Jubilee Hospital (Victoria, British Columbia, Canada) collaborated with provincial emergency health services (British Columbia Emergency Health Services) to cocreate a request process for data from AEDs used by first responders. British Columbia Fire Departments, which are under municipal oversight, required an alternate strategy. Educational presentations allowed for feedback and spread. Patients surviving OHCA and transfer to the regional cardiac centre were consecutively enrolled from November 2018 to April 2020. We evaluated the timeliness of AED information retrieval, and tracked the process to admission. A retrospective chart review informed specifics after admission. A survey to the Coronary Intensive Care Unit staff was used to assess clinical utility.

Results

Seventy-one consecutive patients were enrolled during the study period. Seven rhythm strips arrived with the patient, thus not affected by the initiative. From the remaining 64 cases, 80% (n = 51/64) were received within 48 hours, and 88% (n = 45/51) were received within 24 hours with a median of 1 hour. Eighteen Coronary Intensive Care Unit staff completed the survey; 81% reported AED data as “very useful” to clinical decision-making (n = 13/16). The AED rhythm strips provided insight into OHCA etiology (100%; n = 11/11), supported evidence for diagnoses (100%; n = 11/11), and reduced unnecessary testing (64%; n = 7/11).

Conclusions

Implementing an organized protocol allowed for timely access to AED data, which was directly integrated into clinical decision-making and positively affected hospital stay.

Congenital long QT syndrome and patent ductus arteriosus: A rare surgical scenario

Congenital long QT syndrome (LQTS) is a rare cardiac condition characterized by abnormality of either sodium or potassium ion channels resulting in prolongation of QT interval and thereby predisposing to life-threatening arrhythmia. Once the syndrome is diagnosed, measures should be taken to avoid sudden cardiac death. We present a rare case of LQTS associated with patent ductus arteriosus in a child, and a unique approach was used in managing both conditions.

Mechanotransduction and Adrenergic Stimulation in Arrhythmogenic Cardiomyopathy: An Overview of in vitro and in vivo Models

Arrhythmogenic Cardiomyopathy (AC) is a rare inherited heart disease, manifesting with progressive myocardium degeneration and dysfunction, and life-threatening arrhythmic events that lead to sudden cardiac death. Despite genetic determinants, most of AC patients admitted to hospital are athletes or very physically active people, implying the existence of other disease-causing factors. It is recognized that AC phenotypes are enhanced and triggered by strenuous physical activity, while excessive mechanical stretch and load, and repetitive adrenergic stimulation are mechanisms influencing disease penetrance. Different approaches have been undertaken to recapitulate and study both mechanotransduction and adrenergic signaling in AC, including the use of in vitro cellular and tissue models, and the development of in vivo models (particularly rodents but more recently also zebrafish). However, it remains challenging to reproduce mechanical load stimuli and physical activity in laboratory experimental settings. Thus, more work to drive the innovation of advanced AC models is needed to recapitulate these subtle physiological influences. Here, we review the state-of-the-art in this field both in clinical and laboratory-based modeling scenarios. Specific attention will be focused on highlighting gaps in the knowledge and how they may be resolved by utilizing novel research methodology.

Left Cardiac Sympathetic Denervation Monotherapy in Patients With Congenital Long QT Syndrome

Background:

Videoscopic left cardiac sympathetic denervation (LCSD) is an effective antifibrillatory, minimally invasive therapy for patients with potentially life-threatening arrhythmia syndromes like long QT syndrome (LQTS). Although initially used primarily for treatment intensification following documented LQTS-associated breakthrough cardiac events while on beta-blockers, LCSD as 1-time monotherapy for certain patients with LQTS requires further evaluation. We are presenting our early experience with LCSD monotherapy for carefully selected patients with LQTS.

Methods:

Among the 1400 patients evaluated and treated for LQTS, a retrospective review was performed on the 204 patients with LQTS who underwent LCSD at our institution since 2005 to identify the patients where the LCSD served as stand-alone, monotherapy. Clinical data on symptomatic status before diagnosis, clinical, and genetic diagnosis, and breakthrough cardiac events after diagnosis were analyzed to determine efficacy of LCSD monotherapy.

Result:

Overall, 64 of 204 patients (31%) were treated with LCSD alone (37 [58%] female, mean QTc 466±30 ms, 16 [25%] patients were symptomatic before diagnosis with a mean age at diagnosis 17.3±11.8 years, 5 had [8%] ≥1 breakthrough cardiac event after diagnosis, and mean age at LCSD was 21.1±11.4 years). The primary motivation for LCSD monotherapy was an unacceptable quality of life stemming from beta-blocker related side effects (ie, beta-blocker intolerance) in 56/64 patients (88%). The underlying LQTS genotype was LQT1 in 36 (56%) and LQT2 in 20 (31%). There were no significant LCSD-related surgical complications. With a mean follow-up of 2.7±2.4 years so far, only 3 patients have experienced a nonlethal, post-LCSD breakthrough cardiac event in 180 patient-years.

Conclusions:

LCSD may be a safe and effective stand-alone therapy for select patients who do not tolerate beta-blockers. However, LCSD is not curative and patient selection will be critical when potentially considering LCSD as monotherapy.

The Potential Benefit of Beta-Blockers for the Management of COVID-19 Protocol Therapy-Induced QT Prolongation: A Literature Review

The World Health Organization (WHO) officially announced coronavirus disease 2019 (COVID-19) as a pandemic in March 2020. Unfortunately, there are still no approved drugs for either the treatment or the prevention of COVID-19. Many studies have focused on repurposing established antimalarial therapies, especially those that showed prior efficacy against Severe Acute Respiratory Syndrome Coronavirus (SARS-CoV) and Middle East Respiratory Syndrome Coronavirus (MERS-CoV), such as chloroquine and hydroxychloroquine, against COVID-19 combined with azithromycin. These classes of drugs potentially induce prolongation of the QT interval, which might lead to lethal arrhythmia. Beta-blockers, as a β-adrenergic receptor (β-AR) antagonist, can prevent an increase in the sympathetic tone, which is the most important arrhythmia trigger. In this literature review, we aimed to find the effect of administering azithromycin, chloroquine, and hydroxychloroquine on cardiac rhythm disorders and our findings show that bisoprolol, as a cardio-selective beta-blocker, is effective for the management of the QT (i.e., the start of the Q wave to the end of the T wave) interval prolongation in COVID-19 patients.

Machine Learned Cellular Phenotypes in Cardiomyopathy Predict Sudden Death

RATIONALE

Susceptibility to VT/VF (ventricular tachycardia/fibrillation) is difficult to predict in patients with ischemic cardiomyopathy either by clinical tools or by attempting to translate cellular mechanisms to the bedside.

OBJECTIVE

To develop computational phenotypes of patients with ischemic cardiomyopathy, by training then interpreting machine learning of ventricular monophasic action potentials (MAPs) to reveal phenotypes that predict long-term outcomes.

METHODS AND RESULTS

We recorded 5706 ventricular MAPs in 42 patients with coronary artery disease and left ventricular ejection fraction ≤40% during steady-state pacing. Patients were randomly allocated to independent training and testing cohorts in a 70:30 ratio, repeated K=10-fold. Support vector machines and convolutional neural networks were trained to 2 end points: (1) sustained VT/VF or (2) mortality at 3 years. Support vector machines provided superior classification. For patient-level predictions, we computed personalized MAP scores as the proportion of MAP beats predicting each end point. Patient-level predictions in independent test cohorts yielded c-statistics of 0.90 for sustained VT/VF (95% CI, 0.76-1.00) and 0.91 for mortality (95% CI, 0.83-1.00) and were the most significant multivariate predictors. Interpreting trained support vector machine revealed MAP morphologies that, using in silico modeling, revealed higher L-type calcium current or sodium-calcium exchanger as predominant phenotypes for VT/VF.

CONCLUSIONS

Machine learning of action potential recordings in patients revealed novel phenotypes for long-term outcomes in ischemic cardiomyopathy. Such computational phenotypes provide an approach which may reveal cellular mechanisms for clinical outcomes and could be applied to other conditions.

Arrhythmic risk stratification in post-myocardial infarction patients with preserved ejection fraction: the PRESERVE EF study

Aims

Sudden cardiac death (SCD) annual incidence is 0.6–1% in post-myocardial infarction (MI) patients with left ventricular ejection fraction (LVEF)≥40%. No recommendations for implantable cardioverter-defibrillator (ICD) use exist in this population.

Methods and results

We introduced a combined non-invasive/invasive risk stratification approach in post-MI ischaemia-free patients, with LVEF ≥ 40%, in a multicentre, prospective, observational cohort study. Patients with at least one positive electrocardiographic non-invasive risk factor (NIRF): premature ventricular complexes, non-sustained ventricular tachycardia, late potentials, prolonged QTc, increased T-wave alternans, reduced heart rate variability, abnormal deceleration capacity with abnormal turbulence, were referred for programmed ventricular stimulation (PVS), with ICDs offered to those inducible. The primary endpoint was the occurrence of a major arrhythmic event (MAE), namely sustained ventricular tachycardia/fibrillation, appropriate ICD activation or SCD. We screened and included 575 consecutive patients (mean age 57 years, LVEF 50.8%). Of them, 204 (35.5%) had at least one positive NIRF. Forty-one of 152 patients undergoing PVS (27–7.1% of total sample) were inducible. Thirty-seven (90.2%) of them received an ICD. Mean follow-up was 32 months and no SCDs were observed, while 9 ICDs (1.57% of total screened population) were appropriately activated. None patient without NIRFs or with NIRFs but negative PVS met the primary endpoint. The algorithm yielded the following: sensitivity 100%, specificity 93.8%, positive predictive value 22%, and negative predictive value 100%.

Conclusion

The two-step approach of the PRESERVE EF study detects a subpopulation of post-MI patients with preserved LVEF at risk for MAEs that can be effectively addressed with an ICD.

Clinicaltrials.gov identifier

NCT02124018

Current challenges in sudden cardiac death prevention

Ischemic heart disease and non-ischemic dilated cardiomyopathy are the most common causes of arrhythmic sudden cardiac death (SCD). Implantable cardioverter defibrillator (ICD) therapy is the only strategy that proved to be effective in preventing SCD in high-risk individuals while the role of antiarrhythmic drugs is limited to symptoms relief. Current guidelines recommend selecting candidates to ICD implantation based on etiology, symptoms of heart failure (NYHA class), and severely depressed left ventricular ejection fraction, but these parameters are neither sensitive nor specific. The review addresses the mechanisms of SCD in patients with heart failure of either ischemic or non-ischemic etiology, risk stratification, and strategies for prevention of SCD in the clinical practice (including optimization of heart failure therapy, avoidance of triggering factors, antiarrhythmic drugs, ICD therapy, early resuscitation, and public access defibrillators).

Impact of Myocardial Bridge on Life‐Threatening Ventricular Arrhythmia in Patients With Implantable Cardioverter Defibrillator

Background

Myocardial bridge (MB), common anatomic variant, is generally considered benign, while previous studies have shown associations between MB and various cardiovascular pathologies. This study aimed to investigate for the first time possible impact of MB on long‐term outcomes in patients with implantable cardioverter defibrillator, focusing on life‐threatening ventricular arrhythmia (LTVA).

Methods and Results

This retrospective analysis included 140 patients with implantable cardioverter defibrillator implantation for primary (n=23) or secondary (n=117) prevention of sudden cardiac death. Angiographically apparent MB was identified on coronary angiography as systolic milking appearance with significant arterial compression. The primary end point was the first episode(s) of LTVA defined as appropriate implantable cardioverter defibrillator treatments (antitachyarrhythmia pacing and/or shock) or sudden cardiac death, assessed for a median of 4.5 (2.2–7.1) years. During the follow‐up period, LTVA occurred in 37.9% of patients. Angiographically apparent MB was present in 22.1% of patients; this group showed younger age, lower rates of coronary risk factors and ischemic cardiomyopathy, higher prevalence of vasospastic angina and greater left ventricular ejection fraction compared with those without. Despite its lower risk profiles above, Kaplan–Meier analysis revealed significantly lower event‐free rates in patients with versus without angiographically apparent MB. In multivariate analysis, presence of angiographically apparent MB was independently associated with LTVA (hazard ratio, 4.24; 95% CI, 2.39–7.55; P <0.0001).

Conclusions

Angiographically apparent MB was the independent determinant of LTVA in patients with implantable cardioverter defibrillator. Although further studies will need to confirm our findings, assessment of MB appears to enhance identification of high‐risk patients who may benefit from closer follow‐up and targeted therapies.