Sudden cardiac death markers in non-ischemic cardiomyopathy

The causal effect of Alzheimer's disease and family history of Alzheimer's disease on non-ischemic cardiomyopathy and left ventricular structure and function: a Mendelian randomization study

Background

Previous studies have shown that Alzheimer's disease (AD) can cause myocardial damage. However, whether there is a causal association between AD and non-ischemic cardiomyopathy (NICM) remains unclear. Using a comprehensive two-sample Mendelian randomization (MR) method, we aimed to determine whether AD and family history of AD (FHAD) affect left ventricular (LV) structure and function and lead to NICM, including hypertrophic cardiomyopathy (HCM) and dilated cardiomyopathy (DCM).

Methods

The summary statistics for exposures [AD, paternal history of AD (PH-AD), and maternal history of AD (MH-AD)] and outcomes (NICM, HCM, DCM, and LV traits) were obtained from the large European genome-wide association studies. The causal effects were estimated using inverse variance weighted, MR-Egger, and weighted median methods. Sensitivity analyses were conducted, including Cochran's Q test, MR-Egger intercept test, MR pleiotropy residual sum and outlier, MR Steiger test, leave-one-out analysis, and the funnel plot.

Results

Genetically predicted AD was associated with a lower risk of NICM [odds ratio (OR) 0.9306, 95% confidence interval (CI) 0.8825-0.9813, p = 0.0078], DCM (OR 0.8666, 95% CI 0.7752-0.9689, p = 0.0119), and LV remodeling index (OR 0.9969, 95% CI 0.9940-0.9998, p = 0.0337). Moreover, genetically predicted PH-AD was associated with a decreased risk of NICM (OR 0.8924, 95% CI 0.8332-0.9557, p = 0.0011). MH-AD was also strongly associated with a decreased risk of NICM (OR 0.8958, 95% CI 0.8449-0.9498, p = 0.0002). Different methods of sensitivity analysis demonstrated the robustness of the results.

Conclusion

Our study revealed that AD and FHAD were associated with a decreased risk of NICM, providing a new genetic perspective on the pathogenesis of NICM.

Biomarkers to Predict Sudden Cardiac Death

Sudden cardiac death (SCD) is a common disorder and an unsolved issue for health care providers. Despite several risk factors for SCD, some cases experience SCD as an initial presentation of cardiovascular disease. Prediction of individuals at increased risk for SCD is important for implementing community-based approaches and individual-based therapies with high costs, such as implantable defibrillators. This chapter discusses the potential role of biomarkers in predicting SCD in different cardiovascular diseases.

Non-invasive markers for sudden cardiac death risk stratification in dilated cardiomyopathy

Dilated cardiomyopathy (DCM) is a common yet challenging cardiac disease. Great strides have been made in improving DCM prognosis due to heart failure but sudden cardiac death (SCD) due to ventricular arrhythmias remains significant and challenging to predict. High-risk patients can be effectively managed with implantable cardioverter defibrillators (ICDs) but because identification of what is high risk is very limited, many patients unnecessarily experience the morbidity associated with an ICD implant and many others are not identified and have preventable mortality. Current guidelines recommend use of left ventricular ejection fraction and New York Heart Association class as the main markers of risk stratification to identify patients who would be at higher risk of SCD. However, when analysing the data from the trials that these recommendations are based on, the number of patients in whom an ICD delivers appropriate therapy is modest. In order to improve the effectiveness of therapy with an ICD, the patients who are most likely to benefit need to be identified. This review article presents the evidence behind current guideline-directed SCD risk markers and then explores new potential imaging, electrophysiological and genetic risk markers for SCD in DCM.

Prophylactic use of the implantable cardioverter-defibrillator and its effect on the long-term survival, cardiovascular and sudden cardiac death in nonischemic cardiomyopathy patients-a systematic review and meta-analysis

Implantable cardioverter-defibrillator (ICD) has shown to reduce sudden cardiac death and overall mortality in patients with dilated cardiomyopathy. The recently published DANISH trial has shown conflicting outcomes on the long-term survival in patients with prophylactic implantation of ICD in Non-Ischemic Cardiomyopathy (NICM). Two independent reviewers searched MEDLINE, PUBMED, Ovid, CINAHL, clinicaltrials.gov , and Cochrane Registry for randomized control trials (RCT's) comparing ICD to medical treatment (MT). Six RCT's enrolling 3389 patients (ICD = 1554 and MT = 1835) were included for final analysis. The primary outcomes were mortality comparing ICD to MT, 231 vs 337 (OR = 0.74, CI = 0.62-0.90, p = 0.002, and I² = 0%) favoring ICD. On comparing to amiodarone only, there were 47 deaths in the ICD arm vs 71 deaths in amiodarone arm, (OR = 0.66, CI = 0.44-0.98, p = 0.04, I² 0%), to placebo and usual care only (excluding amiodarone); there were 225 deaths in ICD patients compared to 266 in the placebo and usual care arm, (OR = 0.73, CI = 0.59-0.92, p = 0.007, I² = 15%). The results of our analysis from these six RCTs clearly support the ongoing benefit of prophylactic ICD implantation and support current recommendations for ICD implantation in NICM patients. More RCT's at a larger scale are needed to further elucidate benefits of both ICD and CRT-D in this post PARADIGM era where MT is at a pinnacle in reducing morbidity and mortality in heart failure patients.