Sudden cardiac death in patients with nonischemic cardiomyopathy

Point-of-care Echocardiogram as the Key to Rapid Diagnosis of a Unique Presentation of Dyspnea: A Case Report

INTRODUCTION

Dyspnea is commonly evaluated in the emergency department (ED).The differential diagnosis is broad. Due to the large volume of dyspneic patients evaluated, emergency physicians (EP) will encounter uncommon diagnoses. Early, liberal application of point-of-care ultrasound (POCUS) may decrease diagnostic error and improve care for these patients.

CASE REPORT

We report a 48-year-old male presenting to the ED with cough and progressively worsening dyspnea for 11 months after multiple healthcare visits. Using POCUS, the EP was immediately able to diagnose a severe dilated cardiomyopathy (DCM) with left ventricular thrombus.

CONCLUSION

Given that non-ischemic DCM is one of the most common etiologies of heart failure, often presenting with respiratory symptoms, POCUS is key to rapid diagnosis and, along with modalities such as electrocardiography and chest radiograph, should be standard practice in the workup of dyspnea, regardless of age or comorbidities.

Myocardial fibrosis and the effect of primary prophylactic defibrillator implantation in patients with non-ischemic systolic heart failure-DANISH-MRI

AIMS

Patients with non-ischemic systolic heart failure have an increased risk of sudden cardiac death (SCD). Myocardial fibrosis, detected as late gadolinium enhancement (LGE) with cardiac magnetic resonance (CMR), has been shown to predict all-cause mortality. We hypothesized that LGE can identify patients with non-ischemic heart failure who will benefit from ICD implantation.

METHODS AND RESULTS

In this prospective observational sub-study of the Danish Study to Assess the Efficacy of ICDs in Patients with Nonischemic Systolic Heart Failure on Mortality (DANISH), 252 patients underwent CMR. LGE was quantified by the full width/half maximum method. The primary endpoint was all-cause mortality. LGE could be adequately assessed in 236 patients, median age was 61 years and median duration of heart failure was 14 months; there were 108 patients (46%) randomized to ICD. Median follow-up time was 5.3 years. Median left ventricular ejection fraction on CMR was 35%. In all, 50 patients died. LGE was present in 113 patients (48%). The presence of LGE was an independent predictor of all-cause mortality (HR 1.82; 95% CI 1.002-3.29; P = .049) after adjusting for known cardiovascular risk factors. ICD implantation did not impact all-cause mortality, for either patients with LGE (HR 1.18; 95% CI 0.59-2.38; P = .63), or for patients without LGE (HR 1.00; 95% CI 0.39-2.53; P = .99), (P for interaction =0.79).

CONCLUSION

In patients with non-ischemic systolic heart failure, LGE predicted all-cause mortality. However, in this cohort, LGE did not identify a group of patients who survived longer by receiving an ICD.

Risk stratification in hypertrophic cardiomyopathy

Sudden cardiac death (SCD) is the most devastating complication of hypertrophic cardiomyopathy (HCM). The greatest challenge in the management of HCM is identifying those at increased risk, since an implantable cardioverter-defibrillator (ICD) is a potentially life-saving therapy. We sought to summarize the available data on SCD in HCM and provide a clinical perspective on the current differing and somewhat conflicting data on risk stratification, with balanced guidance regarding rational clinical decision-making. Additionally, we sought to determine the status of the current implementation of guidelines compiled by HCM experts worldwide. The HCM Risk-SCD model helps improve the risk stratification of HCM patients for primary prevention of SCD by calculating an individual risk estimate that contributes to the clinical decision-making process. Improved risk stratification is important for decision-making before ICD implantation for the primary prevention of SCD.

Arrhythmias due to Inherited and Acquired Abnormalities of Ventricular Repolarization

Several acquired and congenital disease conditions and many cardiac and noncardiac drugs affect ventricular repolarization and increase susceptibility to ventricular arrhythmias. Abnormal ventricular repolarization can be reflected on the surface ECG by prolonged or shortened QT interval, early repolarization, and abnormal T-wave configuration. Reduced outward K+ currents and abnormal or increased sodium or calcium currents increase the vulnerability to ventricular arrhythmias. Multiple mechanisms give rise to ventricular arrhythmias in conditions of congenital or acquired abnormal ventricular repolarization. Ventricular arrhythmias associated with abnormalities of ventricular repolarization typically are rapid, usually polymorphic, ventricular tachycardia or torsades de pointes, often degenerating into ventricular fibrillation.

Sudden death mechanisms in nonischemic cardiomyopathies: Insights gleaned from clinical implantable cardioverter-defibrillator trials

Sudden cardiac death (SCD) represents a major cause of death among patients with heart failure. Although scar-based, macroreentrant ventricular tachycardia/ventricular fibrillation is the primary etiology for SCD among patients with ischemic cardiomyopathy, a more diverse set of mechanisms and substrates is likely at play for the diverse group of patients characterized by nonischemic dilated cardiomyopathy (NICM). These causes may include scar-based reentry, but also neurohormonal stimulation (sympathetic, parasympathetic, renin-angiotensin-aldosterone), inflammation, and nonarrhythmic processes occurring in the context of a genetic predisposition. In addition to basic and translational science, observations from large randomized clinical trials of implantable cardioverter-defibrillators (ICDs) can also offer insight and support for specific mechanisms of SCD in these patients. This review will discuss the background of SCD in NICM, its potential mechanisms based on experimental and theoretical models, and the evidence for these mechanisms that can be derived from clinical trials of ICD therapy.

Sudden Cardiac Death Substrate Imaged by Magnetic Resonance Imaging: From Investigational Tool to Clinical Applications

Sudden cardiac death (SCD) is a devastating event afflicting 350 000 Americans annually despite the availability of life-saving preventive therapy, the implantable cardioverter defibrillator. SCD prevention strategies are hampered by over-reliance on global left ventricular ejection fraction <35% as the most important criterion to determine implantable cardioverter defibrillator candidacy. Annually in the United States alone, this results in ≈130 000 implantable cardioverter defibrillator placements at a cost of >$3 billion but only a 5% incidence per year of appropriate firings. This approach further fails to identify individuals who experience the majority, as many as 80%, of SCD events, which occur in the setting of more preserved left ventricular ejection fraction. Better risk stratification is needed to improve care and should be guided by direct pathophysiologic markers of arrhythmic substrate, such as specific left ventricular structural abnormalities. There is an increasing body of literature to support the prognostic value of cardiac magnetic resonance imaging with late gadolinium enhancement in phenotyping the left ventricular to identify those at highest risk for SCD. Cardiac magnetic resonance has unparalleled tissue characterization ability and provides exquisite detail about myocardial structure and composition, abnormalities of which form the direct, pathophysiologic substrate for SCD. Here, we review the evolution and the current state of cardiac magnetic resonance for imaging the arrhythmic substrate, both as a research tool and for clinical applications.