Tools for risk stratification of sudden cardiac death: A review of the literature in different patient populations

While various modalities to determine risk of sudden cardiac death (SCD) have been reported in clinical studies, currently reduced left ventricular ejection fraction remains the cornerstone of SCD risk stratification. However, the absolute burden of SCD is greatest amongst populations without known cardiac disease. In this review, we summarize the evidence behind current guidelines for implantable cardioverter defibrillator (ICD) use for the prevention of SCD in patients with ischemic heart disease (IHD). We also evaluate the evidence for risk stratification tools beyond clinical guidelines in the general population, patients with IHD, and patients with other known or suspected medical conditions.     

Mitral valve abnormalities in decedents of sudden cardiac death due to hypertrophic cardiomyopathy and idiopathic left ventricular hypertrophy

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心电图对急性心肌梗死高危猝死患者的预警作用研究

目的：探讨心电图联合临床危险因素在急性心肌梗死猝死高危患者中的预警作用。方法选择急性心肌梗死伴有恶性心律失常（室性心动过速、心室颤动）患者为恶性心律失常组（n=148）,急性心肌梗死不伴恶性心律失常患者为对照组（n=52）,测量患者的各心电指标,包括QRS时间、Q- T间期和Tp- e间期、J波、碎裂QRS波群,计算Q- Td及Tp- eC,记录左心室射血分数（LVEF）,并随访调查6个月内心脏性猝死的发生情况,比较两组上述指标。根据LVEF值将所有患者分为LVEF≤30%,30%＜LVEF≤40%,40%＜LVEF≤50%,LVEF＞50%,比较不同LVEF者室性心动过速/心室颤动、心脏性猝死发生情况。纳入常见的临床危险因素后,采用Logistic回归分析筛选恶性心律失常的预测因子。结果恶性心律失常组合并糖尿病者、QRS时间、Q- Td、Tp- e间期、Tp- eC、J波、碎裂QRS波群、BNP值和心脏性猝死的发生率均高于对照组（P＜0.05或0.01）,而LVEF值低于对照组（P＜0.01）。随着LVEF的降低,室性心动过速/心室颤动的发生率明显增高,其中30%＜LVEF≤40%所占比例最高（85.5%）。Logistic回归分析结果显示Tp- e间期、LVEF、J波是患者发生恶性心律失常的独立预测因子（r=0.72、0.62、0.49,OR=4.68、3.63、2.46）,Tp- e间期的相关性最强（r=0.72）,相对危险度最高（OR=4.68）。结论Tp- e间期、LVEF、J波是急性心肌梗死患者恶性心律失常发生的危险因素,Tp- e间期的预测价值最高,优于LVEF、J波。LVEF的降低与急性心肌梗死恶性心律失常的发生密切相关。     

Sudden cardiac death in patients with nonischemic cardiomyopathy

Sudden cardiac death (SCD) is an important cause of mortality worldwide. Although SCD is most often associated with coronary heart disease, the risk of SCD in patients without ischemic heart disease is well-established. Nonischemic cardiomyopathies, including idiopathic dilated cardiomyopathy, hypertrophic cardiomyopathy and arrhythmogenic right ventricular cardiomyopathy represent three unique disease entities that have been shown to be highly associated with SCD and ventricular arrhythmias. A variety of risk stratification tools have been investigated, although the optimal strategy remains unknown. Identification of the arrhythmogenic substrate and treatment of ventricular arrhythmias in these subgroups can be challenging. Herein, we aim to discuss the current understanding of the anatomic and electrophysiologic substrate underlying ventricular arrhythmias and highlight features that may be associated with a higher risk of SCD in these 3 conditions.     

心源性猝死危险因素分析

目的探讨和分析心源性猝的危险因素。方法收集和整理在我院2012年04月-2013年10月诊治时发生心源性猝死的心肌患者64例为研究对象,对上述收集对象的临床资料进行整理和分析。结果本组单因素分析显示自发性持续室速、心室颤动(心脏骤停)、晕阙、左室流出道梗阻、非持续性室速等因素为心肌疾病患者发生心源性猝死的危险因素;多因素Logistic分析发现自发性持续性室速、心室颤动、晕阙以及猝死家族史是发生心源性猝死的重要危险因素。结论心肌疾病患者发生心源性猝死的为危险因素呈现综合化、多样化,临床治疗中应给予针对性的预防或治疗,这对降低心肌疾病患者心源性猝死率有着积极的意义。     

Inducibility of life-threatening ventricular arrhythmias is related to maximum left ventricular thickness and clinical markers of sudden cardiac death in patients with hypertrophic cardiomyopathy attributable to the Asp175Asn mutation in the alpha-tropomyosin gene

We investigated inducibility of life-threatening arrhythmias with programmed ventricular stimulation (PVS) in relation to clinical markers of sudden cardiac death (SCD) in subjects with hypertrophic cardiomyopathy (HCM) attributable to the Asp175Asn mutation in the α-tropomyosin gene (TPM1-Asp175Asn). PVS was performed with up to three extrastimuli and distribution of markers of SCD was evaluated in 21 adult subjects with the TPM1-Asp175Asn. Sustained polymorphic ventricular tachycardia (VT) or ventricular fibrillation (VF) was induced in seven of 21 subjects (33%). Inducible subjects had more severe left ventricular hypertrophy (LVH) and an increased number of markers of SCD (family history of SCD, syncope or presyncope, fall in systolic blood pressure (BP) during exercise, documented non-sustained VT (NSVT), and marked LVH) compared to non-inducible subjects (IVS 2.4 ± 0.3 cm vs. 1.6 ± 0.5 cm, P < 0.001; and two to three vs. one to two markers of SCD, P = 0.007, respectively). In conclusion, in HCM attributable to the Asp175Asn mutation in the α-tropomyosin gene, life-threatening arrhythmias were induced in one third of the patients. Inducibility was associated with the maximum left ventricular (LV) thickness and the number of markers of SCD, suggesting that in HCM patients with an identical causative mutation, susceptibility to ventricular arrhythmias is related to the cardiomyopathic phenotype.     

Prevalence and mortality of patients with myocardial infarction and reduced left ventricular ejection fraction in a defined community: Relation to the second multicenter automatic defibrillator implantation trial

Objectives We compared characteristics and mortality of patients from a community population meeting enrollment criteria of the second Multicenter Automatic Defibrillator Implantation Trial (MADIT II) to those of the MADIT II subjects. Background MADIT II showed that implantable cardioverter-defibrillators (ICDs) reduce mortality in patients with myocardial infarction (MI) and low left ventricular ejection fraction (LVEF) ≤30%. Methods We used the resources of the Marshfield Epidemiologic Study Area (MESA), a well defined geographic region to identify MADIT II-type patients and determined outcomes during a 2-year follow-up period. Results Of 1,126 patients who survived an MI, 114 (10.1%) had an LVEF ≤30%, 30 had exclusions leaving 84 patients meeting MADIT II-eligibility with a prevalence of 1.95/1,000. Applied to the US population, there would be about 360,000 MADIT II eligible individuals. MESA patients were older and more likely to be women than their MADIT II counterparts. The cumulative probability of death at 2 years in MESA patients (22.7%) was similar to the MADIT II control group (22%), whereas the sudden cardiac death (SCD) rate was lower in MESA (2.6%) than in MADIT II control patients (12%). Conclusions Differences in demographics, clinical characteristics and risk of SCD in community patients could alter the effectiveness and cost-effectiveness of ICD therapy from results reported in clinical trials. Further research is urgently needed to determine if the evidence-base used to formulate practice guidelines should be generalized to all individuals who meet eligibility criteria for ICD therapy.     

Left ventricular systolic dysfunction, total mortality, and sudden death in patients with myocardial infarction treated with n-3 polyunsaturated fatty acids

BACKGROUND: Sudden death (SD) has a major impact on mortality (M) in patients with left ventricular systolic dysfunction (SyD). In GISSI-Prevenzione, treatment with n-3 polyunsaturated fatty acids (PUFA) reduced M and SD in post-MI patients, but their effect in patients with SyD is unknown. METHODS: 11,323 patients with prior MI and NYHA class < or = II were recruited. After excluding patients with no ejection fraction (EF) measurement (1684), and those with missing data (n=9), 9630 patients were available for analysis. Multivariate Cox regression adjusted models were fitted. RESULTS: Compared to patients with EF > 50%, SyD patients had higher M (12.3% vs. 6.0%) and SD (3.4% vs. 1.4%) rates. PUFA reduced M similarly in patients with (RR 0.76 (0.60-0.96) P=0.02) and without SyD (RR 0.81 (0.59-1.10) P=0.17) (heterogeneity tests P=0.55). In contrast, the effect on SD was markedly asymmetrical: PUFA produced a marked reduction (RR 0.42 (0.26-0.67) P=0.0003) of risk in SyD patients whereas the effect was less evident (RR 0.89 (0.41-1.69) P=0.71) in patients with EF > 50% (heterogeneity tests P=0.07). There was a significant increase in SD with worsening EF (P test for trend=0.02), the benefit on SD in patients with EF < or = 40% being 4-fold higher than in those with EF > 50%. CONCLUSIONS: Increasing SyD is associated with elevated risk of SD and with increasing benefit from PUFA. The effect of PUFA on SD reduction was greater in patients with SyD. Prospective trials testing the effect of PUFA in populations with SyD are required.     

Risk factors for sudden unexpected cardiac death in Tasmanian men

Abstract Background: Sudden unexpected cardiac death (SUCD) accounts for approximately 25% of deaths from ischaemic heart disease (IHD) but is relatively poorly understood because of the difficulties involved in researching aetiology. Clinical differences between instances of SUCD and those cases of acute chest pain that survive long enough to be proven as myocardial infarction but are eventually fatal might reflect differences in aetiology.
Aims: To determine the risk factors for sudden unexpected cardiac death in Tasmanian men.
Methods: A population-based case-control method was used with the study population, an estimated 125,225 men aged 25–74 years living in the island State of Tasmania, Australia. The case group of 102 men who had a SUCD was validated using necropsy reports, hospital records and information provided by the usual general practitioner. Cases were matched with 204 community controls. Spouses or partners of eligible subjects answered a detailed questionnaire. Multivariate odds ratios (ORs) for risk factors were calculated using stepwise analysis.
Results: Risk factors measured included: smoking habit, treated hypertension, hyper-cholesterolaemia, diabetes mellitus, family history of IHD, alcohol intake and exercise habits. Independent risk factors for SUCD were: history of diabetes mellitus (OR=4.2, 95% CI: 1.39, 12.81), current smoking status (OR=3.5, 95% CI: 1.80, 6.82), and family history of IHD (OR=2.6, 95% CI: 1.34, 4.92).
Conclusions: Some accepted risk factors for acute myocardial infarction (AMI) also predict sudden death in men with no history of coronary disease. Efforts to reduce smoking, the incidence of diabetes mellitus and mean blood pressure must be continued as SUCD is, by definition, untreatable but is potentially avoidable in many instances.     

Modern noninvasive risk stratification in primary prevention of sudden cardiac death

Objective  Since the publication of MADIT II and SCD-HeFT, an implantable cardioverter defibrillator (ICD) for primary prevention represents an established, guideline-implemented therapeutic strategy. Facing such an enormous amount of potential ICD recipients, the identification of an effective risk stratification remains crucial. Methods  This article reviews the tools of noninvasive risk stratification which are currently used and defines an optimal test configuration. This analysis focuses on the capacity of the tests regarding to the negative predictive value to reduce unneeded devices. Results  Presently, no marker exists in terms of risk stratification which qualifies itself as gold standard. However, encouraging results can be stated for microvolt T-wave alternans (mTWA) providing a high negative predictive value. An increased QT variability (QTv) and an impaired deceleration capacity are associated with an excellent positive predictive value. Currently, only mTWA and QTv seem to be suitable in ischemic and non-ischemic disease, but available data, especially in non-ischemic patients, are too small to provide clear recommendations. Conclusion  The most hopeful tools at hand in modern noninvasive risk evaluation of sudden cardiac death in primary prevention seem to be mTWA and QTv. These noninvasive methods provide the best negative predictive or positive predictive value of all known parameters, while a higher rate of complete coronary revascularizations in acute coronary syndromes might also reduce the number of fatal arrhythmic events and therefore complicate the invention of an ideal risk marker.     

Electrophysiologic testing guided risk stratification approach for sudden cardiac death beyond the left ventricular ejection fraction

Sudden cardiac death threats ischaemic and dilated cardiomyopathy patients. Anti- arrhythmic protection may be provided to these patients with implanted cardiac defibrillators(ICD), after an efficient risk stratification approach. The proposed risk stratifier of an impaired left ventricular ejection fraction has limited sensitivity meaning that a significant number of victims will remain undetectable by this risk stratification approach because they have a preserved left ventricular systolic function. Current risk stratification strategies focus on combinations of non invasive methods like T wave alternans, late potentials, heart rate turbulence, deceleration capacity and others, with invasive methods like the electrophysiologic study. In the presence of an electrically impaired substrate with formed post myocardial infarction fibrotic zones, programmed ventricular stimulation provides important prognostic information for the selection of the patients expected to benefit from an ICD implantation, while due to its high negative predictive value, patients at low risk level may also be detected. Clustering evidence from different research groups and electrophysiologic labs support an electrophysiologic testing guided risk stratification approach for sudden cardiac death.     

Cardiac index: A superior parameter of cardiac function than left ventricular ejection fraction in risk stratification of hypertrophic cardiomyopathy

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Wearable cardioverter defibrillator after cardiac surgery: Analysis of real-life data from patients at transient risk of sudden cardiac death

Background

Especially in the first 3 months after cardiac surgery, patients are at transient risk of sudden cardiac death (SCD). To close the gap between hospital discharge and the final implantable cardioverter-defibrillator (ICD) decision, guidelines recommend temporarily using a wearable cardioverter-defibrillator (WCD) to protect these patients from SCD. We investigated real-life data on the safety, effectiveness, and compliance of the WCD in this population.

Methods

Data for analysis were collected via the Zoll Patient Management Network (ZPM) from patients who underwent cardiac surgery and who were discharged with a WCD between 2018 and 2021 at the Cardiac Surgery Center of the University of Erlangen in Germany.

Results

The majority of the 55 patients were male (90.9%) and underwent a coronary artery bypass graft (80.0%). The number of patients with left ventricular ejection fraction (LVEF) >35% increased from 9.1% at the beginning of WCD use to 58.2% at the end of WCD use. Six ventricular tachycardia (VT) episodes occurred in four patients. The WCD appropriately defibrillated two patients with VT episodes. There were no inadequate shocks and no fatalities during the observation time. WCD wearing compliance was high, with a median wear time of 23.3 h/day.

Conclusion

This retrospective analysis in a single cardiac surgery center confirms prior data on the safety and effectiveness of the WCD in patients in post-surgery care in a real-life setting. The WCD successfully protected patients from SCD during life-threatening VT episodes. WCD wearing compliance was high.