Time domain analysis of the signal averaged electrocardiogram in patients with a conduction defect or a bundle branch block

Signal-averaged electrocardiography as a noninvasive tool for evaluating the ventricular substrate in patients with nonischemic cardiomyopathy: reassessment of an old tool

Introduction

Signal-averaged electrocardiography (SAECG) provides diagnostic and prognostic information regarding cardiac diseases. However, its value in other nonischemic cardiomyopathies (NICMs) remains unclear. This study aimed to investigate the role of SAECG in patients with NICM.

Methods and results

This retrospective study included consecutive patients with NICM who underwent SAECG, biventricular substrate mapping, and ablation for ventricular arrhythmia (VA). Patients with baseline ventricular conduction disturbances were excluded. Patients who fulfilled at least one SAECG criterion were categorized into Group 1, and the other patients were categorized into Group 2. Baseline and ventricular substrate characteristics were compared between the two groups. The study included 58 patients (39 men, mean age 50.4 ± 15.5 years), with 34 and 24 patients in Groups 1 and 2, respectively. Epicardial mapping was performed in eight (23.5%) and six patients (25.0%) in Groups 1 and 2 (p = 0.897), respectively. Patients in Group 1 had a more extensive right ventricular (RV) low-voltage zone (LVZ) and scar area than those in Group 2. Group 1 had a larger epicardial LVZ than Group 2. Epicardial late potentials were more frequent in Group 1 than in Group 2. There were more arrhythmogenic foci within the RV outflow tract in Group 1 than in Group 2. There was no significant difference in long-term VA recurrence.

Conclusion

In our NICM population, a positive SAECG was associated with a larger RV endocardial scar, epicardial scar/late potentials, and a higher incidence of arrhythmogenic foci in the RV outflow tract.

Noninvasive electrocardiographic risk factors for sudden cardiac death in dilated ca rdiomyopathy: is ambulatory electrocardiography still relevant?

Risk stratification for sudden cardiac death in dilated cardiomyopathy is a field of constant debate, and the currently proposed criteria have been widely questioned due to their low positive and negative predictive value. In this study, we conducted a systematic review of the literature utilizing the PubMed and Cochrane library platforms, in order to gain insight about dilated cardiomyopathy and its arrhythmic risk stratification utilizing noninvasive risk markers derived mainly from 24 h electrocardiographic monitoring. The obtained articles were reviewed in order to register the various electrocardiographic noninvasive risk factors used, their prevalence, and their prognostic significance in dilated cardiomyopathy. Premature ventricular complexes, nonsustained ventricular tachycardia, late potentials on Signal averaged electrocardiography, T wave alternans, heart rate variability and deceleration capacity of the heart rate, all have both some positive and negative predictive value to identify patients in higher likelihood for ventricular arrhythmias and sudden cardiac death. Corrected QT, QT dispersion, and turbulence slope-turbulence onset of heart rate have yet to establish a predictive correlation in the literature. Although ambulatory electrocardiographic monitoring is frequently used in clinical practice in DCM patients, no single risk marker can be used for the selection of patients at high-risk for malignant ventricular arrhythmic events and sudden cardiac death who could benefit from the implantation of a defibrillator. More studies are needed in order to establish a risk score or a combination of risk factors with the purpose of selecting high-risk patients for ICD implantation in the context of primary prevention.

Evaluation of the efficacy of signal-averaged electrocardiogram testing in the cardiac assessment of beta-thalassemia major patients

BACKGROUND

More than 70% of thalassemia's major mortality is due to the cardiac complications of this syndrome, mostly consequent to myocardial Iron overload; therefore, evaluation of such complications is of utmost importance. T2*MRI is used to assess hepatic and myocardial Iron load in thalassemia patients, which is not always available. Signal-Averaged Electrocardiography is a rather easy method of evaluating major thalassemia patients regarding their risk for sudden cardiac death.

METHODS AND MATERIALS

In this cross-sectional study, 48 patients with thalassemia major underwent evaluation with electrocardiography, signal-averaged electrocardiography, echocardiography, T2*MRI, and ferritin level. The association of the existence of ventricular late potentials in SAECG and other cardiac variables was evaluated. Moreover, the association between myocardial and hepatic Iron load and cardiac characteristics was assessed.

RESULTS

48 patients with a mean age of 30.31 ± 7.22 years old entered the study. 27 (56.3%) of the patients had ventricular late potentials, which were associated with myocardial dry Iron weight (P = 0.011). Nonspecific ST-T changes and premature atrial and ventricular contractions were seen more frequently in patients with late potentials (P = 0.002, 0.031, and 0.031, respectively). Patients with higher myocardial and hepatic Iron loads had longer QT_c in their 12-lead surface electrocardiograms.

CONCLUSION

Patients with ventricular late potentials assessed by SAECG had a higher myocardial Iron load. Higher myocardial Iron load is associated with higher cardiac complications in patients with beta-thalassemia major; therefore, SAECG can be used as a screening test for cardiac complications in beta-thalassemia major patients.

Impact of signal-averaged electrocardiography findings on appropriate shocks in prophylactic implantable cardioverter defibrillator patients with nonischemic systolic heart failure

BACKGROUND

Appropriate shock therapy is associated with subsequent all-cause death in heart failure (HF) patients who receive an implantable cardioverter defibrillator (ICD) for the primary prevention of sudden cardiac death. To evaluate the impact of signal-averaged electrocardiography (SAECG) findings on appropriate shocks in prophylactic ICD patients with nonischemic systolic HF.

METHODS

We studied 86 patients with nonischemic HF and a left ventricular ejection fraction ≤ 35% who underwent new ICD implantation for the primary prevention of sudden cardiac death. We excluded patients who had a previously implanted permanent pacemaker and patients who received cardiac resynchronization therapy with an ICD. SAECG was performed before implantation. Abnormal SAECG findings were defined if 2 of the following 3 conditions were identified: filtered QRS duration (fQRS) ≥ 114 ms, root-mean-square voltage during the last 40 ms of the fQRS (RMS 40) < 20 μV, and duration of the low-amplitude potentials < 40 μV (LAS 40) > 38 ms; additionally, patients with a QRS complex ≥ 120 ms who met both the RMS 40 and LAS 40 criteria were also considered to have abnormal SAECG findings. The primary outcome was the first occurrence of appropriate shock after implantation of the ICD. The secondary outcomes were the first occurrence of inappropriate shock and all-cause mortality.

RESULTS

Forty-two patients met the criteria for abnormal SAECG findings (49%). During a median follow-up period of 61 months, 17 patients (20%) died, 24 (28%) received appropriate shock therapy, and 19 (22%) received inappropriate shock therapy. There was a significantly higher incidence of appropriate shocks in patients with abnormal SAECG findings than in those with normal SAECG findings (log-rank test, p = 0.025). Multivariate analysis revealed that abnormal SAECG findings were independently associated with the occurrence of appropriate shock (hazard ratio 2.67, 95% confidential interval 1.14-6.26). However, abnormal SAECG findings were not related to inappropriate shock. There was no difference in the incidence of all-cause death between patients with abnormal and normal SAECG findings.

CONCLUSIONS

Our results suggest that abnormal SAECG findings are associated with a high probability of appropriate shocks in prophylactic ICD patients with nonischemic systolic HF.

Comparative Analysis of the Diagnostic Effectiveness of SATRO ECG in the Diagnosis of Ischemia Diagnosed in Myocardial Perfusion Scintigraphy Performed Using the SPECT Method

There is a great need for early diagnosis of ischemic heart disease (IHD), the most common cause of which is haemodynamic disorders caused mainly by obstructive atherosclerosis of the coronary arteries. The diagnosis of IHD is usually made with the use of functional tests, which include resting ECG (R) or examination of significant perfusion disorders during exercise using the SPECT method. Despite the fact that the ECG (R) test is commonly used in cardiological diagnostics, it has a limited diagnostic value, especially in people with a low probability of coronary artery disease (CAD). In order to increase the effectiveness of the ECG (R) examination, SATRO ECG software, based on the single fibres heart activity model (SFHAM), was used to evaluate the electrocardiograms. The introduction of new classifiers from the available medical data to the analysis made it possible to evaluate the diagnostic efficacy of SATRO ECG (TOT) in predicting significant perfusion disorders in the exercise SPECT (TOT 2). These disorders are most often caused by obstructive atherosclerosis of the coronary arteries, which is the main cause of CAD. The database of 316 patients (219 men and 97 women, aged 57 ± 10 years) was analyzed using resting and stress ECG, perfusion scintigraphy performed using the SPECT method, and SATRO ECG analysis. The diagnostic efficacy parameters of SATRO ECG (TOT) in predicting significant perfusion abnormalities in the exercise-induced SPECT (TOT 2) study were: sensitivity, 99%; specificity, 91%; concordance, 96%; and positive, 96%, and negative, 97%, predictive values. The Kappa–Cohen coefficient was 0.92, and the statistical significance coefficient was p < 0.001. These results indicate a statistically significant agreement in the diagnosis of IHD in both diagnostic methods used.

Noninvasive risk factors for the prediction of inducibility on programmed ventricular stimulation in post-myocardial infarction patients with an ejection fraction ≥40% at risk for sudden cardiac arrest: Insights from the PRESERVE-EF study

Background

In the PRESERVE‐EF study, a two‐step sudden cardiac death (SCD) risk stratification approach to detect post‐myocardial infarction (MI) patients with left ventricle ejection fraction (LVEF) ≥40% at risk for major arrhythmic events (MAEs) was used. Seven noninvasive risk factors (NIRFs) were extracted from a 24‐h ambulatory electrocardiography (AECG) and a 45‐min resting recording. Patients with at least one NIRF present were referred for invasive programmed ventricular stimulation (PVS) and inducible patients received an Implantable Cardioverter ‐ Defibrillator (ICD).

Methods

In the present study, we evaluated the performance of the NIRFs, as they were described in the PRESERVE‐EF study protocol, in predicting a positive PVS. In the PRESERVE‐EF study, 152 out of 575 patients underwent PVS and 41 of them were inducible. For the present analysis, data from these 152 patients were analyzed.

Results

Among the NIRFs examined, the presence of signal averaged ECG‐late potentials (SAECG‐LPs) ≥ 2/3 and non‐sustained ventricular tachycardia (NSVT) ≥1 eposode/24 h cutoff points were important predictors of a positive PVS study, demonstrating in the logistic regression analysis odds ratios 2.285 (p = .027) and 2.867 (p = .006), respectively. A simple risk score based on the above cutoff points in combination with LVEF < 50% presented high sensitivity but low specificity for a positive PVS.

Conclusion

Cutoff points of NSVT ≥ 1 episode/24 h and SAECG‐LPs ≥ 2/3 in combination with a LVEF < 50% were important predictors of inducibility. However, the final decision for an ICD implantation should be based on a positive PVS, which is irreplaceable in risk stratification.

Unexplained Syncope: The Importance of the Electrophysiology Study

Syncope of cardiac origin may be associated with an increased risk of sudden cardiac death if not treated in a timely and appropriate manner. The diagnostic approach of syncope imposes a significant economic burden on society. The investigation and elucidation of the pathogenetic mechanism of syncope are of great clinical importance, as both prognosis and appropriate therapeutic approaches depend on these factors. The responsible mechanism of presyncope or syncope can only be revealed through the patient history, baseline clinical examination and electrocardiogram. The percentage of patients who are diagnosed with these tests alone exceeds 50%. In patients with a history of organic or acquired heart disease or/and the presence of abnormal findings on the electrocardiogram, a further diagnostic electrophysiology inclusive approach should be followed to exclude life threatening arrhythmiological mechanism. However, if the patient does not suffer from underlying heart disease and does not show abnormal electrocardiographic findings in the electrocardiogram, then the probability in the electrophysiology study to find a responsible cause is small but not absent. The role of a two-step electrophysiology study inclusive risk stratification approach for the effective management of the former is thoroughly discussed in this review.

The clinical utility of procainamide-induced late potentials on the signal averaged ECG

BACKGROUND

Late potentials (LPs) identified on the signal averaged electrocardiogram (SAECG) are a marker for an increased risk of arrhythmias in Brugada syndrome (BrS). Procainamide is a sodium channel blocker used to diagnose BrS. The effects of Procainamide on the SAECG in those with BrS and the significance of Procainamide-induced LPs are unknown.

METHODS

Procainamide provocation was performed for suspected BrS with 12-lead and SAECG pre- and post-infusion. Filtered QRS duration (fQRSd), duration of low amplitude signals <40 μV (LAS40) and root-mean-square voltage in the terminal 40 ms (RMS40) were determined.

RESULTS

Data from 150 patients were included in the analysis (mean age 44.5 years, 109 males). Procainamide increased fQRSd (Pre 118.8 ± 10.5 ms, post 121.2 ± 10.2 ms, p < 0.001) and LAS40 (Pre 38.7 ± 9.8 ms, post 40.2 ± 10.5 ms, p = 0.005) and decreased RMS40 (Pre 24.6 ± 12 ms, post 22.8 ± 12 ms, p = 0.002). LPs were present in 68/150 (45%) at baseline. Fifteen patients with negative baseline SAECGs had LPs unmasked by Procainamide, but six patients had LPs at baseline that were no longer present following Procainamide. Comparing those with normal hearts (n = 48) to those with a final diagnosis of BrS (n = 38), Procainamide prolonged fQRSd to a greater extent in those with BrS. Comparing those with Procainamide-induced LPs to those with no LPs at any time did not highlight any aspect of phenotype and did not correlate with a history of ventricular arrhythmias.

CONCLUSIONS

Procainamide influences the SAECG, provoking LPs in a small proportion of patients. However, there is no evidence that Procainamide-induced LPs provide additional diagnostic information or aid risk stratification.

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

Arrhythmic risk stratification in heart failure mid-range ejection fraction patients with a non-invasive guiding to programmed ventricular stimulation two-step approach

BACKGROUND

Although some post myocardial infarction (post-MI) and dilated cardiomyopathy (DCM) patients with mid-range ejection fraction heart failure (HFmrEF/40%-49%) face an increased risk for arrhythmic sudden cardiac death (SCD), current guidelines do not recommend an implantable cardiac defibrilator (ICD). We risk stratified hospitalized HFmrEF patients for SCD with a combined non-invasive risk factors (NIRFs) guiding to programmed ventricular stimulation (PVS) two-step approach.

METHODS

Forty-eight patients (male = 83%, age = 64 ± 14 years, LVEF = 45 ± 5%, CAD = 69%, DCM = 31%) underwent a NIRFs screening first-step with electrocardiogram (ECG), SAECG, Echocardiography and 24-hour ambulatory ECG (AECG). Thirty-two patients with presence of one of three NIRFs (SAECG ≥ 2 positive criteria for late potentials, ventricular premature beats ≥ 240/24 hours, and non-sustained ventricular tachycardia [VT] episode ≥ 1/24 hours) were further investigated with PVS. Patients were classified as either low risk (Group 1, n = 16, NIRFs-), moderate risk (Group 2, n = 18, NIRFs+/PVS-), and high risk (Group 3, n = 14, NIRFs+/PVS+). All in Group 3 received an ICD.

RESULTS

After 41 ± 18 months, 9 of 48 patients, experienced the major arrhythmic event (MAE) endpoint (clinical VT/fibrillation = 3, appropriate ICD activation = 6). The endpoint occurred more frequently in Group 3 (7/14, 50%) than in Groups 1 and 2 (2/34, 5.8%). Logistic regression model adjusted for PVS, age, and LVEF revealed that PVS was an independent MAE predictor (OR: 21.152, 95% CI: 2.618-170.887, P = .004). Kaplan-Meier curves diverged significantly (log rank, P < .001) while PVS negative predictive value was 94%.

CONCLUSIONS

In hospitalized HFmrEF post-MI and DCM patients, a NIRFs guiding to PVS two-step approach efficiently detected the subgroup at increased risk for MAE.

Twelve-lead and signal-averaged electrocardiographic parameters among beta-thalassemia major patients

BACKGROUND

The majority of beta thalassemia major (β-TM) patients suffer from cardiac disease, while a significant proportion of them die suddenly. Twelve-lead and signal-averaged electrocardiography (SAECG) are simple, inexpensive, readily available tools for identifying an unfavorable arrhythmiological substrate by detecting the presence of arrhythmias, conduction abnormalities, and late potentials (LPs) in these patients.

METHODS

A total of 47 β-TM patients and 30 healthy controls were submitted to 12-lead and signal-averaged electrocardiography. Basic electrocardiographic parameters and prevalence of LPs were recorded. Basic echocardiographic parameters were estimated by transthoracic echocardiography. T2* was calculated by cardiac magnetic resonance imaging wherever available.

RESULTS

β-TM patients demonstrated a more prolonged PR interval (167.74 msec vs 147.07 msec) (P = .043), a higher prevalence of PR prolongation (21.05% vs 0%) (P = .013), and a higher prevalence of LPs (18/47, 38.3% vs 2/30, 6.7%) (P = .002) compared with controls. The prevalence of atrial fibrillation among b-TM patients was estimated at 10.64%. Patients had also greater E/e' ratio (8.35, SD = 2.2 vs 7, SD = 2.07) (P = .012) and LAVI (30.7 mL/m2, SD = 8.76 vs 24.6 mL/m2, SD = 6.57) (P = .002) than controls. Regression analysis showed that QTc and LAVI could correctly predict the presence of LPs in the 80.9% of the patients.

CONCLUSIONS

β-TM patients have a higher prevalence of a prolonged PR interval, atrial fibrillation, and LPs. Twelve-lead and SAECG performance was feasible in all subjects and constitutes a readily available tool for assessing myocardial electrophysiological alterations in this patient group.

Temporal changes of noninvasive electrocardiographic risk factors for sudden cardiac death in post-myocardial infarction patients with preserved ejection fraction: Insights from the PRESERVE-EF study

BACKGROUND

Several noninvasive risk factors (NIRFs) have been proposed for sudden cardiac death risk stratification in post-myocardial infarction (post-MI) patients with preserved ejection fraction (EF). However, it remains unclear if these factors change over time.

METHODS

We evaluated seven electrocardiographic NIRFs as they were described in the PRESERVE-EF trial in 80 post-MI patients with EF ≥ 40%, at least 40 days after revascularization and 1 year later.

RESULTS

Mean patient age was 56 ± 10 years, and 88% were men. Mean EF was 50 ± 5%. The prevalence of (a) positive late potentials (27.5% vs. 28.8%, p = .860), (b) >30 premature ventricular complexes/hour (8.8% vs. 11.3%, p = .598), (c) nonsustained ventricular tachycardia (8.8% vs. 5%, p = .349), (d) standard deviation of normal RR intervals <75 ms (3.8% vs. 3.8%, p = 1.000), (e) QTc derived from 24-hr electrocardiography >440 ms (men) or >450 ms (women) (17.5% vs. 17.5%, p = 1.000), (f) deceleration capacity ≤4.5 ms and heart rate turbulence onset ≥0% and slope ≤2.5 ms (2.5% vs. 3.8%. p = 1.000), and (g) ambulatory T-wave alternans ≥65 μV in two Holter channels (6.3% vs. 6.3%, p = 1.000) were similar between the two measurements. However, five patients (6.3%) without any NIRFs during the first assessment had at least one positive NIRF at the second assessment and six patients (7.5%) with at least one NIRF at baseline had no positive NIRFs at 1 year.

CONCLUSIONS

While the prevalence of the examined electrocardiographic NIRFs between the two examinations was similar on a population basis, some patients without NIRFs at baseline developed NIRFs at 1 year and vice versa, highlighting the need for risk factor reassessment during follow-up.

A novel signal-averaged electrocardiogram and an ambulatory-based signal-averaged electrocardiogram show strong correlations with conventional signal-averaged electrocardiogram in healthy subjects: A validation study

BACKGROUND

A novel signal-averaged electrocardiogram (SAECG) device and a novel ambulatory SAECG device are clinically available, but reference values have not been established. This study aimed to validate the novel SAECG and the novel ambulatory-based SAECG devices by comparison with the conventional SAECG device.

METHODS AND RESULTS

High-resolution SAECGs were recorded consecutively in 83 healthy volunteers using the 3 devices. A novel ambulatory SAECG device was used as real-time recording within 15 min for validation study (15 min ambulatory-based SAECG). We examined the concordance of positive results (at least 2/3 abnormal SAECG parameters) and negative results (0 or 1/3 abnormal parameters), as well as the correlations between SAECG parameters (filtered QRS duration [fQRS]); duration of low-amplitude signals < 40 μV in the terminal filtered QRS complex [LAS₄₀]; root mean square voltage of the terminal 40 ms of the filtered QRS complex [RMS₄₀]). Qualitative analysis showed excellent concordance among the novel SAECG, the 15 min ambulatory-based SAECG, and the conventional SAECG methods (novel SAECG vs. conventional SAECG = 94%; 15 min ambulatory-based SAECG vs. conventional SAECG = 91.6%; p = 0.755), while quantitative analysis indicated strong correlations between the novel SAECG and the conventional SAECG values for fQRS, LAS₄₀, and LnRMS₄₀ (r = 0.838-0.805, p < 0.0001, respectively). Strong correlations were also seen between 15 min ambulatory-based SAECG and conventional SAECG values for fQRS, LAS₄₀, and RMS₄₀ (r = 0.943-0.888, p < 0.0001, respectively). However, Bland-Altman quantitative analysis showed better agreement in fQRS and LnRMS₄₀ measured by the 15 min ambulatory-based SAECG and the conventional SAECG than those by the novel SAECG and the conventional SAECG (fQRS, Lin's rho_c = 0.923 vs. 0757; RMS₄₀, Lin's rho_c = 0.932 vs. 0.818, respectively).

CONCLUSION

In healthy subjects, the parameters of either the novel SAECG or the 15 min ambulatory-based SAECG and those of the conventional SAECG were strongly correlated. Relatively good agreements were observed among 3 SAECGs, especially better between the 15 min ambulatory-based SAECG and the conventional SAECG probably due to similar measurement system of 2 methods.

Signal-averaged electrocardiography: Past, present, and future

Signal-averaged electrocardiography records delayed depolarization of myocardial areas with slow conduction that can form the substrate for monomorphic ventricular tachycardia. This technique has been examined mostly in patients with coronary artery disease, but its use has been declined over the years. However, several lines of evidence, derived from hitherto clinical data in patients with healed myocardial infarction, indicate that signal-averaged electrocardiography remains a valuable tool in risk stratification, especially when incorporated into algorithms encompassing invasive and noninvasive indices. Such an approach can aid the more precise identification of candidates for device therapy, in the context of primary prevention of sudden cardiac death. This article reappraises the value of signal-averaged electrocardiography as a predictor of arrhythmic outcome in patients with ischemic heart disease and discusses potential future indications.

Arrhythmic risk stratification in heart failure: Time for the next step?

BACKGROUND

Primary prevention of sudden cardiac death by means of implantable cardioverter-defibrillators constitutes the holy grail of arrhythmology. However, current risk stratification algorithms lead to suboptimal outcomes, by both allocating ICDs to patients not deriving any meaningful survival benefit and withholding them from those erroneously considered as low-risk for arrhythmic mortality.

METHODS

In the present review article we will attempt to present shortcomings of contemporary guidelines regarding sudden death prevention in ischemic and dilated cardiomyopathy patients and present available data suggesting encouraging results following implementation of multifactorial approaches, by using multiple modalities, both noninvasive and invasive. Invasive electrophysiological testing, namely programmed ventricular stimulation, will be discussed in greater length to highlight both its potential usefulness and currently ongoing multicenter studies aiming to provide evidence necessary to make the next step in sudden death risk stratification.

RESULTS

Promising findings have been reported by multiple study groups regarding novel strategies for both negative selection of low and positive selection of relatively preserved ejection fraction patients as candidates for ICD implantation.

CONCLUSIONS

The era of ejection fraction as the sole risk stratifier for arrhythmic risk in heart failure appears to be drawing to an end, especially if current underway large studies validate previous findings.

Prevalence of late potentials on signal-averaged ECG in patients with psychiatric disorders

BACKGROUND

Sudden cardiac death (SCD) occurs three times more often in psychiatric patients than in the general population. QRS fragmentation (QRSfr) and signal-averaged electrocardiography (SAECG) are simple, inexpensive, readily available tools for detecting the presence of abnormal depolarization and late potentials (LPs) in these patients, a result of either the underlying disease or treatment.

METHODS

Frequency of LP detection by SAECG and QRSfr was studied in 52 psychiatric patients and compared with 30 healthy (without known structural heart disease or occurrence of ventricular arrhythmia) controls. Patients were then prospectively followed up and incidence of SCD was recorded.

RESULTS

LP prevalence was significantly higher in patients than in controls (16/52-31% vs 2/30-7%, p=0.012), while QRSfr was similar between these two groups (p=0.09). Of the LP presence criteria, the root mean square value at terminal 40msec of the QRS (RMS40) was significantly lower in patients (32μV, SD=19μV, vs 46μV, SD=32μV, p=0.015). Among patients, no differences were noted between the LP positive and negative groups regarding age, sex, number of medications, class of antipsychotics and defined daily doses. Mean follow-up was 46months (SD=11) and during it 3 patients suffered SCD. Although 2 SCD victims had both LPs and QRSfr concurrently present, neither of them, nor their simultaneous presence could definitely account for the events.

CONCLUSIONS

LP prevalence in psychiatric patients was significantly higher than in controls. SAECG performance was feasible in all cases and constitutes a readily available tool for assessing myocardial electrophysiological alterations in this patient group.

Deceleration Capacity of Heart Rate Predicts Arrhythmic and Total Mortality in Heart Failure Patients

BACKGROUND

Deceleration capacity (DC) of heart rate proved an independent mortality predictor in postmyocardial infarction patients. The original method (DCorig) may produce negative values (9% in our analyzed sample). We aimed to improve the method and to investigate if DC also predicts the arrhythmic mortality.

METHODS

Time series from 221 heart failure patients was analyzed with DCorig and a new variant, the DCsgn, in which decelerations are characterized based on windows of four consecutive beats and not on anchors. After 41.2 months, 69 patients experienced sudden cardiac death (SCD) surrogate end points, while 61 died.

RESULTS

(SCD+ vs SCD-group) DCorig: 3.7 ± 1.6 ms versus 4.6 ± 2.6 ms (P = 0.020) and DCsgn: 4.9 ± 1.7 ms versus 6.1 ± 2.2 ms (P < 0.001). After Cox regression (gender, age, left ventricular ejection fraction, filtered QRS, NSVT≥1/24h, VPBs≥240/24h, mean 24-h QTc, and each DC index added on the model separately), DCsgn (continuous) was an independent SCD predictor (hazard ratio [H.R.]: 0.742, 95% confidence intervals (C.I.): 0.631-0.871, P < 0.001). DCsgn ≤ 5.373 (dichotomous) presented 1.815 H.R. for SCD (95% C.I.: 1.080-3.049, P = 0.024), areas under curves (AUC)/receiver operator characteristic (ROC): 0.62 (DCorig) and 0.66 (DCsgn), P = 0.190 (chi-square). Results for deceased versus alive group: DCorig: 3.2 ± 2.0 ms versus 4.8 ± 2.4 ms (P < 0.001) and DCsgn: 4.6 ± 1.4 ms versus 6.2 ± 2.2 ms (P < 0.001). In Cox regression, DCsgn (continuous) presented H.R.: 0.686 (95% C.I. 0.546-0.862, P = 0.001) and DCsgn ≤ 5.373 (dichotomous) presented an H.R.: 2.443 for total mortality (TM) (95% C.I. 1.269-4.703, P = 0.008).

AUC/ROC

0.71 (DCorig) and 0.73 (DCsgn), P = 0.402.

CONCLUSIONS

DC predicts both SCD and TM. DCsgn avoids the negative values, improving the method in a nonstatistical important level.

Diagnosis of Rejection by Analyzing Ventricular Late Potentials in Heart Transplant Patients

Background

Heart transplant rejection originates slow and fragmented conduction. Signal-averaged ECG (SAECG) is a stratification method in the risk of rejection.

Objective

To develop a risk score for rejection, using SAECG variables.

Methods

We studied 28 transplant patients. First, we divided the sample into two groups based on the occurrence of acute rejection (5 with rejection and 23 without). In a second phase, we divided the sample considering the existence or not of rejection in at least one biopsy performed on the follow-up period (rejection pm1: 18 with rejection and 10 without).

Results

On conventional ECG, the presence of fibrosis was the only criterion associated with acute rejection (OR = 19; 95% CI = 1.65-218.47; p = 0.02). Considering the rejection pm1, an association was found with the SAECG variables, mainly with RMS40 (OR = 0.97; 95% CI = 0.87-0.99; p = 0.03) and LAS40 (OR = 1.06; 95% IC = 1.01-1.11; p = 0.03). We formulated a risk score including those variables, and evaluated its discriminative performance in our sample. The presence of fibrosis with increasing of LAS40 and decreasing of RMS40 showed a good ability to distinguish between patients with and without rejection (AUC = 0.82; p < 0.01), assuming a cutoff point of sensitivity = 83.3% and specificity = 60%.

Conclusion

The SAECG distinguished between patients with and without rejection. The usefulness of the proposed risk score must be demonstrated in larger follow-up studies.

New Imaging Technologies To Characterize Arrhythmic Substrate

The cornerstone of the new imaging technologies to treat complex arrhythmias is the electroanatomic (EAM) mapping. It is based on tissue characterization and in particular on determination of low potential region and dense scar definition. Recently, the identification of fractionated isolated late potentials increased the specificity of the information derived from EAM. In addition, non-invasive tools and their integration with EAM, such as cardiac magnetic resonance imaging and computed tomography scanning, have been shown to be helpful to characterize the arrhythmic substrate and to guide the mapping and the ablation. Finally, intracardiac echocardiography, known to be useful for several practical uses in the setting of electrophysiological procedures, it has been also demonstrated to provide important informations about the anatomical substrate and may have potential to identify areas of scarred myocardium.

Implantable cardioverter defibrillator therapy activation for high risk patients with relatively well preserved left ventricular ejection fraction. Does it really work?

BACKGROUND

Current guidelines for the primary prevention of sudden cardiac death have used a left ventricular ejection fraction (LVEF) ≤ 35% as a critical point to justify implantable cardioverter defibrillator (ICD) implantation in post myocardial infarction patients and in those with nonischemic dilated cardiomyopathy. We compared mortality and ICD activation rates among different ICD group recipients using a cut-off value for LVEF ≤ 35%.

METHODS

We followed up for a mean period of 41.1 months 495 ICD recipients (442 males, 65.6 years old, 68.9% post myocardial infarction patients, 422 with LVEF ≤ 35%). Prevention was considered primary in patients who fulfilled guidelines criteria or had inducible ventricular arrhythmia during programmed ventricular stimulation for patients with LVEF >35%.

RESULTS

Over the course of the trial, 84 of 495 patients died; 69 experienced cardiac death (6 sudden) and 15 non cardiac death. ICD recipients with LVEF ≤ 35% compared to those with preserved LVEF (mean LVEF=43%) had a greater incidence of total mortality (18% vs. 11%, log rank p=0.028) and cardiac death (15.4% vs. 5.5%, log rank p=0.005). There was no difference in the incidence for appropriate device therapy between patients with LVEF ≤ 35% and those with LVEF >35% (56.9% vs. 65.8%, log rank p=0.93). In the multivariate analysis the presence of advanced New York Heart Association stage predicted both total mortality (HR=2.69, 95% CI 1.771-4.086) and cardiac death (HR=3.437, 95% CI 2.163-5.463).

CONCLUSIONS

ICD therapy may protect heart failure patients at early stages from arrhythmic morbidity and mortality, based on an electrophysiology-guided risk stratification approach.

SAECG in exercise test for prediction of diabetic coronary artery disease

Signal averaged electrocardiogram (SAECG) is considered an important noninvasive indicator identifying patients at risk for ventricular arrhythmias. The aim of this study was to improve noninvasive prediction of CAD by integrating SAECG with the result of exercise tests in diabetic patients. Diabetic patients with stable angina pectoris underwent exercise testing and SAECG. Then a diagnostic score was derived that combined results of exercise testing and SAECG. A diagnostic score (0 to 2 points) was calculated by assigning 1 point for a positive exercise test result and 1 point for a positive SAECG. One hundred and seventy patients were included in the study. In patients with a score of 0, the likelihood of CAD is 18% whereas the likelihood of CAD is 95% in patients with a score of 2. Triple vessel CAD is present in 54%, 7% and only 1.5% of patients with score 2, 1 and 0 respectively. Therefore, patients with score 2 have a poor prognosis compared with score 1 or 0. A diagnostic score combining exercise testing and SAECG can distinguish patients with CAD from those without CAD with high accuracy in diabetic patients.

Usefulness of post-ventriculotomy signal averaged electrocardiograms in congenital heart disease

Signal-averaged electrocardiography is a sensitive and specific technique for detecting the slow conduction electrophysiologic substrates of reentrant monomorphic ventricular tachycardia. Although well established, the method has not been used for electrophysiologic assessment after right ventriculotomy for the intracardiac repair of congenital heart disease. This 8-year prospective study provided this assessment. Recordings were obtained from 242 post-ventriculotomy patients with congenital heart disease aged 16 to 72 years (139 males, 103 females). Because ventricular volume or pressure overload can prolong the QRS duration, 40 unoperated patients with hemodynamic overload served as controls. Orthogonal X, Y, and Z body surface electrodes were used to detect ventricular late potentials by permitting the examination of portions of the electrocardiogram otherwise obscured by noise and artifacts. Positive signal-averaged electrocardiographic (SAECG) results were based on established criteria derived from 3 time-domain variables calculated by an automated algorithm. Late potentials were detected in 151 of 242 patients (62%) and were significantly higher than controls (p = 0.0001). Radiofrequency ablation of an inducible slow conduction substrate rendered 20 of 23 positive post-ventriculotomy SAECG results negative, and surgical revision of the ventriculotomy scar rendered 19 of 19 positive SAECG results negative. In conclusion, negative SAECG results connote the absence of a reentrant substrate, and therefore, the absence of risk for reentrant monomorphic ventricular tachycardia, whereas positive SAECG results connote the presence of a slow conduction substrate and the potential risk for monomorphic ventricular tachycardia.

Implantable defibrillators: from the adult cardiac to the grown up congenital heart disease patient

The automatic implantable defibrillators (AID) are increasingly used for both secondary and primary prevention of sudden cardiac death (SCD) in high risk adult cardiac patients with sustained ventricular arrhythmias (SVA) and/or significant ventricular dysfunction. The corresponding experience with AIDs in pediatric and young adult population is limited suggesting at least the same benefit as in the adult population. With the growing number of adults with previous corrective surgery of complex congenital heart disease (CHD), a need to address the risk stratification process for SCD among these patients is becoming increasingly important. For the present time, the AIDs have been mostly utilized for the secondary prevention of SCD in those postoperative CHD adult patients with a history of SVA. Currently available data on how to assess the risk for SCD among such patients as well as implications about the potential to prevent SCD with an earlier use of AID in this growing population are presented and discussed.

Time course of appearance of markers of arrhythmia in patients with tetralogy of Fallot before and after surgery

Sudden death and ventricular tachycardia are known to occur late after correction of tetralogy of Fallot. Abnormal dispersion of the QT interval, ventricular late potentials, and prolongation of the QRS complex, alone or in combination, are useful markers of the risk for such complications. Our present prospective study investigates the time course of appearance of two markers, dispersion of QT and JT, and ventricular late potentials, before and after corrective surgery. Dispersion of QT and JT, and signal averaged electrocardiographic parameters, were determined sequentially in 20 patients before, a mean of 9 +/- 3 days after, and again 35 +/- 11 days post-operatively. Dispersion of QT was already abnormal before surgery in two-fifths of the patients, but increased markedly in the later post-operative period. Ventricular late potentials were absent before surgery and in the immediate post-operative period, but were found in one-fifth of patients 1 month later. We conclude that abnormal dispersion of QT is, to some extent, a fact of the natural history of tetralogy of Fallot, but is significantly amplified by surgery. Ventricular late potentials, on the other hand, are absent before surgery, but appear with some delay after the operation, probably as a result of scarring rather than the surgical incision itself. Long-term follow-up is needed to assess the significance of these findings.

Signal-averaged electrocardiogram in Ebstein's anomaly

We sought to establish pathogenetic links between electrophysiology, histopathology, and ventricular tachyarrhythmias in patients with Ebstein's anomaly. The atrialized right ventricle (ARV) is the site of mechanically inducible ventricular tachyarrhythmias, but relations between the arrhythmogenic substrate, the type of tachyarrhythmias, and the trigger(s) have not been established. This study comprised 23 patients (10 men and 13 women; aged 18 to 58 years; mean 32 +/- 3) who did not undergo surgery and 6 pre- and postoperative patients with Ebstein's anomaly, diagnosed by transthoracic and transesophageal echocardiography. Twenty-one patients had classic Ebstein's anomaly and 2 had mild forms. Signal-averaged electrocardiograms (SAECGs) identified slow conduction by using 3 time-domain variables calculated by an automated algorithm and inspected visually. Two variables were required to establish the presence of late potentials. SAECGs were repeated in 6 patients after surgical exclusion of the ARV. Five surgical specimens of the ARV and the true right atrium were examined histologically. Mathematic simulations were used to illustrate anchored and unanchored spiral/scroll waves. SAECGs were positive in 21 patients with classic Ebstein's anomaly and were negative postoperatively in the 6 so studied. The ARV was characterized histologically by clusters of cardiomyocytes isolated within a fibrous matrix. We hypothesize that SAECGs identify slow conduction residing in the ARV, and that excitation of this arrhythmogenic substrate provokes spiral/scroll waves that cannot anchor because clusters of cardiomyocytes are isolated within a fibrous matrix. The waves meander erratically as polymorphic ventricular tachycardia or break up into ventricular fibrillation.

Utility of SAECG in arrhythmogenic right ventricle dysplasia

BACKGROUND

Arrhythmogenic right ventricular dysplasia (ARVD) is characterized by progressive replacement of RV myocardium with fibro-adipose tissue thought to be responsible for the presence of late potentials (LP) detected by SAECG. The general consensus on the role of SAECG in the diagnosis and prognosis of patients with ARVD is lacking. The purpose of this systematic review was to better define the role of SAECG in ARVD.

METHODS

An extensive review of literature was done to specifically describe the prevalence of LP in ARVD and its determinants, explore the various options available to improve the diagnostic ability of SAECG, and provide recommendations for proper utilization of this technique.

RESULTS

LPs are frequent in ARVD (47-100%), and more prevalent in severe disease and in patients with documented spontaneous VT. SAECG is a useful test in following the characteristic evolutivity of the disease. 4-16% of normal family members of patients with ARVD also have abnormal SAECG results. Detection of LP in ARVD can be improved by employing a high-pass filter of 25 Hz and specifically looking for changes in the Z leads.

CONCLUSIONS

SAECG testing should be considered a standard part of the evaluation of patients with known or suspected ARVD. Further research is needed to confirm the value of SAECG testing in predicting arrhythmia risk and assessing the rate of disease progression, as well as to determine if greater prevalence of SAECG abnormalities in family members of patients with ARVD represents early detection of ARVD. The ongoing multidisciplinary study of right ventricular dysplasia will hopefully answer some of these questions.

Complete bundle branch block as an independent predictor of all-cause mortality: report of 7,073 patients referred for nuclear exercise testing

PURPOSE

Complete left bundle branch block is a well-established independent risk factor for mortality, but the prognostic importance of right bundle branch block is unclear. We determined whether left and right bundle branch block was associated with all-cause mortality risk after adjustment for potential confounders, including clinical, exercise, and nuclear scintigraphic variables.

SUBJECTS AND METHODS

We studied 7,073 adults who were referred for symptom-limited nuclear exercise testing. Patients with heart failure or pacemakers were excluded. The presence or absence of bundle branch block was determined from resting electrocardiograms. The main outcome measure was all-cause mortality during a mean of 6.7 years of follow-up.

RESULTS

One hundred ninety patients (3%) had complete right bundle branch block, and 150 (2%) had complete left bundle branch block. There were 825 deaths (12%). Mortality was greater in patients with complete right bundle branch block (24% [46 of 190]) or left bundle branch block (24% [36 of 150]) than in those without these findings (11% [779 of 6,883 and 789 of 6,923, respectively]; both P <0.0001). After adjustment for potential confounders, right bundle branch block was as strong an independent predictor of mortality (hazard ratio [HR] 1.5; 95% confidence interval [CI]: 1.1 to 2.1; P = 0.007) as left bundle branch block (HR 1.5; 95% CI: 1.0 to 2.0; P = 0.017). Incomplete right bundle branch block was not associated with mortality.

CONCLUSION

Complete right and left bundle branch block are independent predictors of all-cause mortality risk even after adjustment for exercise capacity, nuclear perfusion defects, and other risk factors.

Echocardiographic and signal averaged ECG indices associated with non-sustained ventricular tachycardia after repair of tetralogy of fallot

OBJECTIVE

To identify any possible association between different readily available non-invasive indices and potential malignant ventricular arrhythmias in patients with repaired tetralogy of Fallot.

DESIGN

27 consecutive patients, mean (SD) age 27.3 (11.7) years, were studied 15.7 (6.7) years after corrective surgery for tetralogy of Fallot, using 12 lead ECG, 24 hour Holter recordings, signal averaged ECG, and echocardiography. The following variables were measured: standard QRS duration, filtered QRS duration (fltQRS), low amplitude signal duration, and root mean square voltage of the last 40 ms of the fltQRS (RMS-40), as well as right ventricular systolic pressure, right ventricular ejection fraction, and the ratio of the maximum short axis diameters of the right and left ventricles (RD:LD).

RESULTS

All patients had right bundle branch block, with a mean QRS duration of 137.1 (14.9) ms. There were no patients with sustained arrhythmia. Five patients had runs of non-sustained ventricular tachycardia (group A) and the other 22 patients did not (group B). Univariate analysis showed that fltQRS and RD:LD ratio were significantly associated with non-sustained ventricular tachycardia. In addition, a fltQRS >/= 148 ms, low amplitude signal >/= 32.5 ms, RMS-40 </= 23 microV, and RD:LD ratio >/= 1.05 were cut off points with a high sensitivity for detecting patients with non-sustained ventricular tachycardia.

CONCLUSIONS

Abnormal signal averaged ECG and echocardiographic variables are associated with potentially malignant ventricular arrhythmias on the Holter recordings in asymptomatic patients with repaired tetralogy of Fallot.

The signal-averaged electrocardiogram is of limited value in patients with bundle branch block and dilated cardiomyopathy in predicting inducible ventricular tachycardia or death

An abnormal signal-averaged electrocardiogram (SAECG) has predictive value for arrhythmic events in patients with idiopathic dilated cardiomyopathy and a normal conduction. The purpose of this study was to investigate whether the presence of a complete bundle branch block (BBB) affects prognostic information of the SAECG. We prospectively obtained SAECGs in 128 patients with idiopathic dilated cardiomyopathy. Forty-three of them had BBB and 85 had a normal QRS duration. According to their clinical history and results of ventricular programmed stimulation, patients were divided into 4 groups: (1) group IA with BBB and ventricular tachycardia (VT) (n = 18); (2) group IB with BBB but without VT (n = 25); (3) group IIA without BBB but with VT (n = 40); (4) group IIB without BBB and without VT (n = 45). Patients were compared with 129 patients without heart disease and without VT. Fifty-seven of them had BBB (group III) and 72 had normal conduction (group IV). The filtered QRS duration was longer in group IB than in group III (175 +/- 21 vs 149 +/- 16 ms, p <0.001), and in group IIB than in group IV (111 +/- 19 vs 96 +/- 12 ms, p <0.05). QRS duration was similar in groups IA and IB (176 +/- 24 vs 175 +/- 21 ms) but longer in group IIA than in group IIB (131 +/- 24 vs 111 +/- 19 ms, p <0.001). The low-amplitude signal duration (LAS) and the root-mean-square voltage (RMS) of the last 40 ms of the filtered QRS did not differ between groups IB and III and IA and IB. LAS and RMS were, respectively, longer (44 +/- 20 vs 31 +/- 13 ms, p <0.01) and lower (21 +/- 20 vs 43 +/- 33 microV, p <0.001) in groups IIA and IIB. In groups IA and IB the combination of 2 of the 3 available criteria: QRS duration >170 ms, RMS <20 microV, LAS >45 ms lead up to the best overall statistical result, with a sensitivity and specificity of 78% and 56%, respectively. In groups IIA and IIB, using conventional late potential criteria, the sensitivity and specificity of the SAECG for VT detection were 65% and 73%, respectively. The risk of sudden death was not predicted by the SAECG, and total cardiac mortality was only dependent on left ventricular ejection fraction. In conclusion, QRS duration was prolonged in all of the patients with a dilated cardiomyopathy compared with those without heart disease. BBB did not change the sensitivity but decreased the specificity of the SAECG to predict any VT risk in dilated cardiomyopathy. The risk of sudden death and total cardiac mortality could not be predicted by the SAECG.