Predicting the Future: Risk Stratification for Sudden Cardiac Death in Patients With Left Ventricular Dysfunction

Automated Detection of Sudden Cardiac Death by Discrete Wavelet Transform of Electrocardiogram Signal

Sudden cardiac death (SCD) results in millions of deaths annually; as it is a fatal heart abnormality, early prediction of SCD could save peoples’ lives to the greatest extent. Symmetry and asymmetry play an important role in many fields. Electrocardiograms (ECG) as a noninvasive process for acquiring the electrical activity of the heart, has both asymmetric and non-stationary characteristics; it is frequently employed to diagnose and evaluate the heart’s condition. In this work, we have detected SCD 14 min (separately for each one-minute interval) prior to its occurrence by analyzing ECG signals using discrete wavelet transform (DWT) and locality preserving projection (LPP). In the experiment, we have performed DWT on ECG signals to obtain coefficients, then LPP as a reduction methodology was used to cut down these obtained coefficients. Then, the acquired LPP features were ranked using various methods, including the T-test, Bhattacharyya, Wilcoxon, and entropy. At last, the highly ranked LPP features were subjected to decision tree, k-nearest neighbor (KNN), and support vector machine classifiers for distinguishing normal from SCD ECG signals. Our proposed technique has achieved a highest accuracy of 97.6% for the detection of SCD 14 min prior using the KNN classifier, compared to the existing works. Our proposed method is capable of predicting the people at risk of developing SCD 14 min before its onset, and, hence, clinicians would have enough time to provide treatment in intensive care units (ICU) for a subject at risk of SCD. Thus, this proposed technique as a useful tool can increase the survival rate of many cardiac patients.

ECG-Based Identification of Sudden Cardiac Death through Sparse Representations

Sudden Cardiac Death (SCD) is an unexpected sudden death due to a loss of heart function and represents more than 50% of the deaths from cardiovascular diseases. Since cardiovascular problems change the features in the electrical signal of the heart, if significant changes are found with respect to a reference signal (healthy), then it is possible to indicate in advance a possible SCD occurrence. This work proposes SCD identification using Electrocardiogram (ECG) signals and a sparse representation technique. Moreover, the use of fixed feature ranking is avoided by considering a dictionary as a flexible set of features where each sparse representation could be seen as a dynamic feature extraction process. In this way, the involved features may differ within the dictionary's margin of similarity, which is better-suited to the large number of variations that an ECG signal contains. The experiments were carried out using the ECG signals from the MIT/BIH-SCDH and the MIT/BIH-NSR databases. The results show that it is possible to achieve a detection 30 min before the SCD event occurs, reaching an an accuracy of 95.3% under the common scheme, and 80.5% under the proposed multi-class scheme, thus being suitable for detecting a SCD episode in advance.

Quantifying cardiac sympathetic denervation: first studies of 18F-fluorohydroxyphenethylguanidines in cardiomyopathy patients

PURPOSE

4-¹⁸F-Fluoro-m-hydroxyphenethylguanidine (¹⁸F-4F-MHPG) and 3-¹⁸F-fluoro-p-hydroxyphenethylguanidine (¹⁸F-3F-PHPG) were developed for quantifying regional cardiac sympathetic nerve density using tracer kinetic analysis. The aim of this study was to evaluate their performance in cardiomyopathy patients.

METHODS

Eight cardiomyopathy patients were scanned with ¹⁸F-4F-MHPG and ¹⁸F-3F-PHPG. Also, regional resting perfusion was assessed with ¹³N-ammonia. ¹⁸F-4F-MHPG and ¹⁸F-3F-PHPG kinetics were analyzed using the Patlak graphical method to obtain Patlak slopes K_p (mL/min/g) as measures of regional nerve density. Patlak slope polar maps were used to evaluate the pattern and extent of cardiac denervation. For comparison, "retention index" (RI) values (mL blood/min/mL tissue) were also calculated and used to assess denervation. Perfusion polar maps were used to estimate the extent of hypoperfusion.

RESULTS

Patlak analysis of ¹⁸F-4F-MHPG and ¹⁸F-3F-PHPG kinetics was successful in all subjects, demonstrating the robustness of this approach in cardiomyopathy patients. Substantial regional denervation was observed in all subjects, ranging from 25 to 74% of the left ventricle. Denervation zones were equal to or larger than the size of corresponding areas of hypoperfusion. The two tracers provided comparable metrics of regional nerve density and the extent of left ventricular denervation. ¹⁸F-4F-MHPG exhibited faster liver clearance than ¹⁸F-3F-PHPG, reducing spillover from the liver into the inferior wall. ¹⁸F-4F-MHPG was also metabolized more consistently in plasma, which may allow application of population-averaged metabolite corrections.

CONCLUSION

The advantages of ¹⁸F-4F-MHPG (more rapid liver clearance, more consistent metabolism in plasma) make it the better imaging agent to carry forward into future clinical studies in patients with cardiomyopathy.

TRIAL REGISTRATION

Registered at the ClinicalTrials.gov website (NCT02669563). URL: https://clinicaltrials.gov/ct2/show/NCT02669563.

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.

A time local subset feature selection for prediction of sudden cardiac death from ECG signal

Prediction of sudden cardiac death continues to gain universal attention as a promising approach to saving millions of lives threatened by sudden cardiac death (SCD). This study attempts to promote the literature from mere feature extraction analysis to developing strategies for manipulating the extracted features to target improvement of classification accuracy. To this end, a novel approach to local feature subset selection is applied using meticulous methodologies developed in previous studies of this team for extracting features from non-linear, time-frequency, and classical processes. We are therefore enabled to select features that differ from one another in each 1-min interval before the incident. Using the proposed algorithm, SCD can be predicted 12 min before the onset; thus, more propitious results are achieved. Additionally, through defining a utility function and employing statistical analysis, the alarm threshold has effectively been determined as 83%. Having selected the best combination of features, the two classes are classified using the multilayer perceptron (MLP) classifier. The most effective features would subsequently be discussed considering their prevalence in the rank-based selection. The results indicate the significant capacity of the proposed method for predicting SCD as well as selecting the appropriate processing method at any time before the incident. Graphical abstract ᅟ.

Pattern of late gadolinium enhancement predicts arrhythmic events in patients with non-ischemic cardiomyopathy

BACKGROUND

Left ventricular late gadolinium enhancement (LV-LGE) by cardiac magnetic resonance (CMR) imaging has been associated with adverse clinical outcomes in patients with non-ischemic cardiomyopathy (NICM). However, an association between the characteristics of the LGE and arrhythmic risk has not been demonstrated consistently. This study evaluated the impact of the LV-LGE characteristics on the arrhythmia risk in patients with NICM.

METHODS

This study enrolled 365 consecutive patients (54±15years) with NICM who underwent CMR imaging. All patients were monitored for the following outcomes: major arrhythmic events (MA), including sustained ventricular tachycardia, an appropriate implantable cardioverter-defibrillator intervention, ventricular fibrillation and sudden cardiac death.

RESULTS

During 44.3±36.4months of follow-up, 44 (12.1%) patients experienced MA. LV-LGE was observed in 40 (90.9%) and 221 (68.8%) patients with and without MA, respectively. LV-LGE was more frequently observed in the MA group (p=0.002). The age- and sex-adjusted hazard ratio (HR) of MA was increased in patients with LGE extent≥8% (HR 8.45, 95% confidence interval (CI) 2.91-24.6), and those with subendocardial (HR 6.98, 95% CI 1.74-28.0) and subepicardial LGE patterns (HR 7.2, 95% CI 1.61-35.6). In multivariable models adjusted for other clinical variables, only the subepicardial LGE pattern had 7.2 (95% CI, 1.61-32.6, p=0.01) time increase in the MA risk.

CONCLUSIONS

LV-LGE in patients with NICM is not uncommon. The subepicardial pattern of the LV-LGE was an independent predictor of MA, suggesting that specific patterns of the LV-LGE are closely related to the severity of arrhythmic events.

National Trends in the Use of Cardiac Resynchronization Therapy With or Without Implantable Cardioverter-Defibrillator

BACKGROUND

Candidates for cardiac resynchronization therapy (CRT) receive either a biventricular pacemaker or a biventricular pacemaker with an implantable cardioverter-defibrillator (CRT-D). Optimal device selection remains challenging because the benefit of implantable cardioverter-defibrillator therapy may not be uniform, particularly in patients at competing risk of nonsudden death.

METHODS AND RESULTS

In this serial cross-sectional study using the National Inpatient Sample database, we identified 311,086 admissions associated with CRT implant between 2006 to 2012. CRT-D was the most common device type (86.1%), including in patients ≥ 75 years of age with ≥ 5 Elixhauser comorbidities (75.5%). Multivariate predictors of CRT-D implant included demographic, clinical, and geographic factors: prior ventricular arrhythmia (rate ratio [RR], 1.14; 95% CI, 1.13-1.14), ischemic heart disease (RR, 1.11; 95% CI, 1.10-1.11), male sex (RR, 1.10; 95% CI, 1.09-1.10), black race (RR, 1.06; 95% CI: 1.04-1.07), and Northeast geographic region (RR, 1.06; 95% CI, 1.04-1.09). There was significant interhospital variation in the use of CRT-D (10-90 percentile range, 72.9%-98.0% CRT-D).

CONCLUSIONS

The majority of patients in this contemporary US cohort underwent implantation of CRT-D. Predictors of CRT-D implant included demographic, clinical, and geographic factors. In patient subgroups predicted to have an attenuated benefit from implantable cardioverter-defibrillator therapy (older adults with multiple comorbidities), CRT-D remained the dominant device type. An improved understanding of the determinants of device selection may aid in decision making and ultimately better align patient risk with device benefit at the time of CRT implantation.

Sympathetic nerve damage and restoration after ischemia-reperfusion injury as assessed by (11)C-hydroxyephedrine

PURPOSE

An altered state of the cardiac sympathetic nerves is an important prognostic factor in patients with coronary artery disease. The aim of this study was to investigate regional sympathetic nerve damage and restoration utilizing a rat model of myocardial transient ischemia and a catecholamine analog PET tracer, (11)C-hydroxyephedrine ((11)C-HED).

METHODS

Transient myocardial ischemia was induced by coronary occlusion for 20 min and reperfusion in male Wistar rats. Dual-tracer autoradiography was performed subacutely (7 days) and chronically (2 months) after ischemia, and in control rats without ischemia using (11)C-HED as a marker of sympathetic innervation and (201)TI for perfusion. Additional serial in vivo cardiac (11)C-HED and (18)F-FDG PET scans were performed in the subacute and chronic phases after ischemia.

RESULTS

After transient ischemia, the (11)C-HED uptake defect areas in both the subacute and chronic phases were clearly larger than the perfusion defect areas in the midventricular wall. The subacute (11)C-HED uptake defect showed a transmural pattern, whereas uptake recovered in the subepicardial portion in the chronic phase. Tyrosine hydroxylase antibody nerve staining confirmed regional denervation corresponding to areas of decreased (11)C-HED uptake. Serial in vivo PET imaging visualized reductions in the area of the (11)C-HED uptake defects in the chronic phase consistent with autoradiography and histology.

CONCLUSION

Higher susceptibility of sympathetic neurons compared to myocytes was confirmed by a larger (11)C-HED defect with a corresponding histologically identified region of denervation. Furthermore, partial reinnervation was observed in the chronic phase as shown by recovery of subepicardial (11)C-HED uptake.

[ICD therapy in the primary prevention of sudden cardiac death: Risk stratification and patient selection]

Without the concept of primary prevention of sudden cardiac death, therapy with implantable defibrillators would not have reached the current distribution and clinical importance. Most of the scientific evidence of the concept is based on clinical studies from 1996-2005. More than 75 % of all defibrillator implantations are currently indicated as primary prevention. Implantable converter-defibrillator (ICD) therapy in the primary prevention of sudden cardiac death was incorporated into scientific guidelines starting in 1998. The historical development of the indications for ICD therapy in the primary prevention of sudden cardiac death is presented, reflecting major results of controlled, randomized clinical studies and guideline discussions.

Fragmented QRS for the prediction of sudden cardiac death: a meta-analysis

AIMS

Risk stratification of sudden cardiac death (SCD) is challenging. Fragmented QRS (fQRS) is proposed as a non-invasive electrocardiogram marker associated with mortality and SCD. Results from individual studies including small numbers of patients are discrepant. We therefore performed a meta-analysis of studies evaluating fQRS as a risk stratification tool to predict all-cause mortality and SCD.

METHODS AND RESULTS

Electronic databases and bibliographies were systematically searched (1996-2014). Twelve studies (5009 patients) recruiting patients with coronary artery disease or non-ischaemic cardiomyopathy met our inclusion criteria. Fragmented QRS was associated with an all-cause mortality relative risk of 1.71 (CI 1.02-2.85) and a relative risk of SCD of 2.20 (CI 1.05-4.62). Subgroup analysis demonstrated greater mortality and SCD risk in those with left ventricular ejection fraction >35% and SCD risk in those with QRS duration <120 ms.

CONCLUSION

Fragmented QRS is associated with all-cause mortality and the occurrence of SCD and may be suited as a marker of SCD risk. The incremental benefit of fQRS should be assessed in a randomized, prospective setting.

Impact of the presence and amount of myocardial fibrosis by cardiac magnetic resonance on arrhythmic outcome and sudden cardiac death in nonischemic dilated cardiomyopathy

BACKGROUND

Current risk stratification for sudden cardiac death (SCD) in nonischemic dilated cardiomyopathy (NIDC) relies on left ventricular (LV) dysfunction, a poor marker of ventricular electrical instability. Contrast-enhanced cardiac magnetic resonance has the ability to accurately identify and quantify ventricular myocardial fibrosis (late gadolinium enhancement [LGE]).

OBJECTIVE

To evaluate the impact of the presence and amount of myocardial fibrosis on arrhythmogenic risk prediction in NIDC.

METHODS

One hundred thirty-seven consecutive patients with angiographically proven NIDC were enrolled for this study. All patients were followed up for a combined arrhythmic end point including sustained ventricular tachycardia (VT), appropriate implantable cardioverter-defibrillator (ICD) intervention, ventricular fibrillation (VF), and SCD.

RESULTS

LV-LGE was identified in 76 (55.5%) patients. During a median follow-up of 3 years, the combined arrhythmic end point occurred in 22 (16.1%) patients: 8 (5.8%) sustained VT, 9 (6.6%) appropriate ICD intervention, either against VF (n = 5; 3.6%) or VT (n = 4; 2.9%), 3 (2.2%) aborted SCD, and 2 (1.5%) died suddenly. Kaplan-Meier analysis revealed a significant correlation between the LV-LGE presence (not the amount and distribution) and malignant arrhythmic events (P < .001). In univariate Cox regression analysis, LV-LGE (hazard ratio [HR] 4.17; 95% confidence interval [CI] 1.56-11.2; P = .005) and left bundle branch block (HR 2.43; 95% CI 1.01-5.41; P = .048) were found to be associated with arrhythmias. In multivariable analysis, the presence of LGE was the only independent predictor of arrhythmias (HR 3.8; 95% CI 1.3-10.4; P = .01).

CONCLUSIONS

LV-LGE is a powerful and independent predictor of malignant arrhythmic prognosis, while its amount and distribution do not provide additional prognostic value. Contrast-enhanced cardiac magnetic resonance may contribute to identify candidates for ICD therapy not fulfilling the current criteria based on left ventricular ejection fraction.

Role of CMR imaging in risk stratification for sudden cardiac death

Left ventricular ejection fraction as determined by echocardiography has a limited sensitivity in predicting risk for sudden cardiac death (SCD). Subsequent efforts to improve cost-effectiveness of device implantation and identify a better risk-stratifying tool have been quite desirable. The presence of scar and myocardial tissue heterogeneity has been linked to ventricular arrhythmia, which is believed to be the major cause of SCD. Cardiac magnetic resonance is a noninvasive imaging modality that visualizes and quantifies scar, with growing evidence delineating its additive value in identifying patients at higher risk for SCD.

The clinical characteristics of sudden cardiac arrest in asymptomatic patients with congenital heart disease

Sudden cardiac arrest (SCA) is a major cause of death in patients with congenital heart disease (CHD). Systemic ventricular dysfunction is a reported risk factor for SCA. We retrospectively analyzed the medical records of 46 patients (age >6 years) who experienced SCA. The following underlying cardiac defects were observed: biventricular repair with affected subpulmonary right ventricle (n = 18, 39 %), biventricular repair with systemic right ventricle and Eisenmenger syndrome (n = 6 each, 13 %), Fontan circulation and unrepaired CHD (n = 5 each, 11 %), and others (n = 6, 13 %). Twenty-one patients (46 %) had no history of arrhythmias, and 21 of 43 (49 %) showed systemic ventricular ejection fraction >55 %. According to the New York Heart Association classification, 18 patients (39 %) were class I and 28 (61 %) were class II/III. SCA occurred at a younger age in class I (16 ± 5 years) than in the other classes (23 ± 10 years; P = 0.004). QRS duration was similar between the groups (136 ± 38 vs. 141 ± 50 ms; P not significant). Seven patients in class I (15 % of all SCAs) had no history of arrhythmias or features of hemodynamic abnormalities. The proportion of patients with biventricular repair and affected subpulmonary right ventricle was higher than that of patients with other defects, and the majority of SCA patients had more complicated defects than a simple repaired ventricular septal defect or an atrial septal defect. No symptoms of heart failure, history of arrhythmias, or features of hemodynamic abnormalities were observed in 15 % of the patients who experienced SCA. Prolonged QRS duration might be a predictor of SCA even in asymptomatic CHD patients. Prevention of SCA in CHD patients may require more detailed evaluation than is typically considered necessary.

Regional myocardial sympathetic denervation predicts the risk of sudden cardiac arrest in ischemic cardiomyopathy

OBJECTIVES

The PAREPET (Prediction of ARrhythmic Events with Positron Emission Tomography) study sought to test the hypothesis that quantifying inhomogeneity in myocardial sympathetic innervation could identify patients at highest risk for sudden cardiac arrest (SCA).

BACKGROUND

Left ventricular ejection fraction (LVEF) is the only parameter identifying patients at risk of SCA who benefit from an implantable cardiac defibrillator (ICD).

METHODS

We prospectively enrolled 204 subjects with ischemic cardiomyopathy (LVEF ≤35%) eligible for primary prevention ICDs. Positron emission tomography (PET) was used to quantify myocardial sympathetic denervation ((11)C-meta-hydroxyephedrine [(11)C-HED]), perfusion ((13)N-ammonia) and viability (insulin-stimulated (18)F-2-deoxyglucose). The primary endpoint was SCA defined as arrhythmic death or ICD discharge for ventricular fibrillation or ventricular tachycardia >240 beats/min.

RESULTS

After 4.1 years follow-up, cause-specific SCA was 16.2%. Infarct volume (22 ± 7% vs. 19 ± 9% of left ventricle [LV]) and LVEF (24 ± 8% vs. 28 ± 9%) were not predictors of SCA. In contrast, patients developing SCA had greater amounts of sympathetic denervation (33 ± 10% vs. 26 ± 11% of LV; p = 0.001) reflecting viable, denervated myocardium. The lower tertiles of sympathetic denervation had SCA rates of 1.2%/year and 2.2%/year, whereas the highest tertile had a rate of 6.7%/year. Multivariate predictors of SCA were PET sympathetic denervation, left ventricular end-diastolic volume index, creatinine, and no angiotensin inhibition. With optimized cut-points, the absence of all 4 risk factors identified low risk (44% of cohort; SCA <1%/year); whereas ≥2 factors identified high risk (20% of cohort; SCA ∼12%/year).

CONCLUSIONS

In ischemic cardiomyopathy, sympathetic denervation assessed using (11)C-HED PET predicts cause-specific mortality from SCA independently of LVEF and infarct volume. This may provide an improved approach for the identification of patients most likely to benefit from an ICD. (Prediction of ARrhythmic Events With Positron Emission Tomography [PAREPET]; NCT01400334).