Prognostic value of an abnormal signal-averaged electrocardiogram in patients with nonischemic congestive cardiomyopathy

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.

Increasing averaging beats improves the test accuracy on Holter-based late potentials in patients with myocardial infarction

BACKGROUND

The prevalence of Holter-based late potentials (H-LPs) in cases of fatal cardiac events has increased. Although the noise level of H-LP is higher than that of conventional real-time late potential (LP) recording, a procedure to reduce the noise severity in H-LP by increasing the averaging beats has not been investigated.

METHODS

We enrolled 104 patients with post-myocardial infarction (MI) and 86 control participants. Among the patients, 30 reported sustained ventricular tachycardia (VT), and the remaining 74 had unrecorded VT. H-LPs were measured twice in all groups to evaluate the efficacy of increasing the averaging beats for H-LPs. Thereafter, the average of LP was calculated at 250 (default setting), 300, 400, 500, 600, 700, and 800 beats.

RESULTS

Across all three groups (MI-VT group, MI non-VT group, and control group), the noise levels significantly decreased in consonance with the increase in averaging beats. In the MI-VT group, the H-LP positive rate considerably increased with the increase in the averaging beats from 250 to 800 both at night and daytime. In the MI-VT group, the LP parameters significantly deteriorated, which led to a positive judgment corresponding to the increment of the averaged night and day beats. The H-LP positive rates were unchanged in the MI non-VT and control groups, while the LP parameters remained consistent, despite the increased averaging beats in the MI non-VT and control groups.

CONCLUSION

Increasing the calculated averaging beats in H-LPs can improve the sensitivity of predicting fatal cardiac events in patients with MI.

Diurnal Variation in and Optimal Time to Measure Holter-Based Late Potentials to Predict Lethal Arrhythmia after Myocardial Infarction

Background and Objectives: Holter-based late potentials (LPs) are useful for predicting lethal arrhythmias in organic cardiac diseases. Although Holter-based LPs exhibit diurnal variation, no studies have evaluated the optimal timing of LP measurement over 24 h for predicting lethal arrhythmia that leads to sudden cardiac death. Thus, this study aimed to validate the most effective timing for Holter-based LP testing and to explore factors influencing the diurnal variability in LP parameters. Materials and Methods: We retrospectively analyzed 126 patients with post-myocardial infarction (MI) status and 60 control participants who underwent high-resolution Holter electrocardiography. Among the 126 post-MI patients, 23 developed sustained ventricular tachycardia (VT) (the MI-VT group), while 103 did not (the MI-non-VT group) during the observation period. Holter-based LPs were measured at 0:00, 4:00, 8:00, 12:00, 16:00, and 20:00, and heart rate variability analysis was simultaneously performed to investigate factors influencing the diurnal variability in LP parameters. Results: Holter-based LP parameters showed diurnal variation with significant deterioration at night and improvement during the day. Assessment at the time with the longest duration of low-amplitude signals < 40 μV in the filtered QRS complex terminus (LAS40) gave the highest receiver operating characteristics curve (area under the curve, 0.659) and the highest odds ratio (3.75; 95% confidence interval, 1.45-9.71; p = 0.006) for predicting VT. In the multiple regression analysis, heart rate and noise were significant factors affecting the LP parameters in the MI-VT and control groups. In the non-VT group, the LP parameters were significantly influenced by noise and parasympathetic heart rate variability parameters, such as logpNN50. Conclusions: For Holter-based LP measurements, the test accuracy was higher when the LP was measured at the time of the highest or worst value of LAS40. Changes in autonomic nervous system activity, including heart rate, were factors influencing diurnal variability. Increased parasympathetic activity or bradycardia may exacerbate Holter-based LP parameters.

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.

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.

Fragmented QRS as a predictor of cardiac events in patients with cardiac sarcoidosis

BACKGROUND

Multiple spikes within the QRS complex, known as fragmented QRS (fQRS), are associated with the occurrences of ventricular arrhythmic events (VAEs) in patients with Brugada syndrome and hypertrophic cardiomyopathy. However, the association between fQRS and occurrence of VAEs in patients with cardiac sarcoidosis (CS) has not been elucidated.

METHODS

We evaluated the associations between fQRS and cardiac events including VAEs [non-sustained ventricular tachycardia (NSVT), sustained ventricular tachycardia (VT), and ventricular fibrillation (VF)], hospitalization for heart failure, and all-cause death in 68 patients with CS (30 patients with fQRS vs. 38 patients without fQRS) over a 5-year period.

RESULTS

Cardiac events occurred in 22 patients with fQRS and 18 patients without fQRS (73% vs. 47%, p=0.009). Of the cardiac events that occurred in CS patients, VAEs occurred more frequently in patients with fQRS than in patients without fQRS (VAEs: 70% vs. 45%, p=0.017; NSVT: 70% vs. 45%, p=0.010; VT: 43% vs. 18%, p=0.011, and VF: 6.7% vs. 2.6%, p=0.34), whereas there was no significant difference in hospitalization for heart failure or all-cause death between patients with and those without fQRS (hospitalization for heart failure: 6.7% vs. 5.3%, p=0.75; all-cause death: 6.7% vs. 5.3%, p=0.64). Multivariate analysis showed that fQRS in the baseline electrocardiogram was independently associated with VAEs (hazard ratio: 2.21, 95% confidence interval: 1.15-4.25, p=0.017).

CONCLUSION

fQRS is a predictor of VAEs in patients with CS.

Noninvasive prediction of late potentials in the signal-averaged ECG in patients with chronic Chagas disease

INTRODUCTION

Considering the importance of ventricular arrhythmias in the prediction of sudden cardiac death in chronic Chagas heart disease, the aim of the present study was to associate late potentials observed in the signal-averaged electrocardiogram (SAECG) with either non-sustained ventricular tachycardia in the 24-hour Holter monitoring or reduced left ventricular ejection fraction in the 2-dimension echocardiogram.

METHODS

This was a retrospective transversal study. The medical charts of 49 patients with chronic Chagas heart disease that underwent 24-hour Holter monitoring at our institution from September 2012 to December 2015 were reviewed. In the univariate analysis, variables associated with SAECG at a p value <0.05 were entered a multivariate stepwise logistic regression analysis through the model forward. A p value <0.05 was considered to have statistical significance.

RESULTS

In the univariate analysis, right bundle branch block, left atrial diameter, left ventricular systolic diameter, and left ventricular ejection fraction were associated with late potential in the SAECG. In the multivariate analysis, however, right bundle branch block and left atrial diameter were retained as independent predictors of late potentials in the SAECG.

CONCLUSIONS

Neither ventricular arrhythmias in the 24-Holter monitoring nor reduced left ventricular ejection fraction in the 2-D echocardiogram were associated with late potentials in the SAECG of patients with chronic Chagas heart disease.

Detection of cardiac involvement in pulmonary sarcoidosis using high-resolution Holter electrocardiogram

BACKGROUND

Early detection of cardiac involvement in patients with sarcoidosis is important but currently unresolved. The aim of this study was to elucidate the utility of frequency domain microvolt T-wave alternans (TWA), signal-averaged ECG (SAECG), and heart rate turbulence (HRT) using 24-hour Holter ECG for detecting cardiac involvement in patients with pulmonary sarcoidosis.

METHODS

This study consisted of consecutive 40 pulmonary sarcoidosis patients (11 males, 62 ± 13 years) who underwent 24-hour Holter monitoring with and without cardiac involvement. All patients underwent frequency domain TWA, SAECG, and HRT using 24-hour Holter monitoring. Patients with atrial fibrillation pacing or wide QRS electrocardiogram were excluded.

RESULTS

After 14 patients were excluded, a total of 26 patients (six males, 59 ± 14 years) were evaluated. Seven patients had cardiac involvement (cardiac sarcoidosis [CS] group). On the Holter SAECG, duration of low-amplitude signals <40 μV in the terminal filtered QRS complex (LAS40) was significantly higher, and root mean square voltage of the terminal 40 ms of the filtered QRS complex (RMS40) was significantly lower in the CS group compared with the non-CS group (LAS40: 61.4 ± 35.9 vs 37.6 ± 9.2 ms; P = .018, RMS40: 11.4 ± 10.3 vs 23.6 ± 13.2 ms; P = .023). Prevalence of positive late potential (LP) was also significantly higher in the CS group than that in the non-CS group (85.7% vs 31.5%; P = .026). The sensitivity, specificity, positive, and negative predictive values of LP for identifying patients with cardiac involvement were 85.7%, 68.4%, 50.0%, and 92.8%, respectively.

CONCLUSION

Holter SAECG may be useful for detecting cardiac involvement in patients with pulmonary sarcoidosis.

Detection of arrhythmogenic substrate within QRS complex in patients with cardiac sarcoidosis using wavelet-transformed ECG

Signal-averaged electrocardiography (SAECG) has been known to be useful for prediction of lethal ventricular arrhythmias (VA). However, this technique has limitations in patients with intraventricular conduction disturbance (IVCD), which is common in cardiac sarcoidosis (CS). Meanwhile, wavelet-transformed ECG (WTECG) has been reported to be useful for detecting arrhythmogenic substrate hidden within QRS complex. The objective of this study was to assess the utility of WTECG for detecting arrhythmogenic substrate in patients with CS. Forty-four CS patients including 18 patients with VA were retrospectively investigated. The parameters on the signal-averaged electrocardiography (SAECG) and the power of frequency components on WTECG were compared between VA group and non-VA group. Eighteen patients have VA (VT: n = 17, VF: n = 1). LP were detected in 17 in VA group and 24 in non-VA group. WTECG showed that high-frequency components (HFC; 80-150 Hz) were developed in VA group. Peak power value at 150 Hz (P150) was significantly higher in VA group than that in non-VA group (442.9 ± 160.2 vs 316.7 ± 100.8, p = 0.006). The receiver operating characteristic (ROC) curve analysis showed an optimal cutoff point of 336 of P150 for detecting patients with VA, with 82.4% sensitivity, 61.5% specificity, and area under the curve of 0.74 (95% confidence interval [CI] 0.59-0.89). WTECG may be useful for detecting CS patients who are prone to VA.

Primary prevention implantable cardioverter-defibrillator and opportunities for sudden cardiac death risk assessment in non-ischaemic cardiomyopathy

Sudden cardiac death (SCD) accounts for approximately one-third of all deaths among patients with non-ischaemic cardiomyopathy (NICM). Implantable cardioverter-defibrillator (ICD) therapy has been the primary intervention for managing individuals at high risk for SCD. However, individual ICD trials in the NICM population have failed to demonstrate a mortality benefit with prophylactic ICD implantation. Current guidelines recommend ICD implantation in NICM patients with symptomatic heart failure and a left ventricular ≤35% and are based on meta-analyses of multiple trials that span three decades and include the recent Danish Study to Assess the Efficacy of ICDs in Patients with Non-ischaemic Heart Failure on Mortality (DANISH) trial. These pooled analyses report a significant reduction in all-cause mortality with ICD implantation compared with medical therapy alone. In addition, each of these trials has demonstrated consistently a reduction in the risk of SCD compared with medical therapy alone. As a result, a refined approach of risk stratification that selects patients at the highest risk for SCD may lead to a significant improvement in ICD efficacy. In this clinical review, we first discuss the evolution of clinical trials that have evaluated ICDs in the NICM population. We then highlight some key markers of arrhythmia risk that hold promise in personalizing risk stratification for SCD.

Prognostic significance of ventricular late potentials in patients with pulmonary sarcoidosis

BACKGROUND

Early detection of cardiac involvement in sarcoidosis is difficult but essential to achieve optimal treatment. Signal-averaged electrocardiography (SAECG) can detect subtle cardiac electrical abnormalities termed late potentials (LPs) and would be useful for the early diagnosis of cardiac involvement.

OBJECTIVE

This study aims to investigate the prognostic significance of LP in patients with pulmonary sarcoidosis.

METHODS

We prospectively studied 74 patients with pulmonary sarcoidosis without overt electrocardiographic abnormalities. All participants underwent SAECG, cardiac echocardiography, and 24-hour ambulatory Holter monitoring. Serum angiotensin-converting enzyme and B-type natriuretic peptide levels were also evaluated. We followed these patients for the evaluation of incidence of cardiac events including cardiac death, arrhythmias, and heart failure requiring hospital admission.

RESULTS

Of the studied population, 29 patients (39.2%) had detectable LP. During a mean follow-up period of 9.8 years, 8 patients with LPs had cardiovascular events, including development of complete atrioventricular block (n = 4), ventricular tachycardia (n = 2), and heart failure (n = 2). Meanwhile, only 1 of 45 patients without LP developed cardiac event (heart failure). Multivariate analyses revealed that LPs were associated with an increased risk of developing cardiac events (hazard ratio 9.66; 95% confidence interval 1.20-78.01; P = .033) whereas age, sex, serum angiotensin-converting enzyme and B-type natriuretic peptide levels, number of premature ventricular contractions on 24-hour Holter monitoring, and echocardiographic parameters were not associated with subsequent cardiac events.

CONCLUSION

SAECG might possibly be useful for the early detection of cardiac sarcoidosis and, if independently validated, could eventually be considered as a screening test for further risk stratification.

Ventricular arrhythmias in nonischemic cardiomyopathy

Nonischemic cardiomyopathies (NICMs) are composed of variable disease entities, including primary and secondary cardiomyopathies. Determining the etiology of NICM provides pivotal roles of not only the understanding of the individual pathogenesis, but also the clinical management, such as risk stratification, pharmacological treatment, and intervention therapies. Despite the diverse causes of NICM, these cases mostly require clinical attention owing to progressive myocardial injury, resulting in ventricular dysfunction and heart failure. The interaction between the diseased ventricular substrates and systemic/neurophysiological factors contributes to the cornerstones responsible for ventricular arrhythmogenesis and sudden cardiac death (SCD). Prevention of SCD and diminishing ventricular tachyarrhythmias are the important mainstays for the management of NICM patients. Given the understanding of the abnormal ventricular substrates and advancement of navigation systems, radiofrequency catheter ablation (RFCA) has become an adjunctive or alternative strategy for NICM patients who experience drug-refractory ventricular tachycardias (VTs). Successful ablation can frequently be achieved at the expense of an epicardial intervention. A recent study has proven the survival benefits for NICM patients who are free from recurrent VTs after a successful RFCA, regardless of the New York Heart Association (NYHA) functional class status or left ventricular ejection fraction. Additionally, recent evidence has highlighted the better delineation of a diseased myocardium through the incorporation of cardiovascular magnetic resonance imaging (CMRI) and 3D mapping systems, which can facilitate the identification of critical ventricular arrhythmogenic substrates in NICM patients.

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.

Narrowing filtered QRS duration on signal-averaged electrocardiogram predicts outcomes in cardiac resynchronization therapy patients with nonischemic heart failure

BACKGROUND

To evaluate the impact of changes in the filtered QRS duration (fQRS) on signal-averaged electrocardiograms (SAECGs) from pre- to postimplantation on the clinical outcomes in nonischemic heart failure (HF) patients under cardiac resynchronization therapy (CRT).

METHODS

We studied 103 patients with nonischemic HF and sinus rhythm who underwent CRT implantation. SAECGs were obtained within 1 week before and 1 week after implantation and narrowing fQRS was defined as a decrease in fQRS from pre- to postimplantation. Echocardiography was performed before and 6 months after CRT implantation. The primary outcome was death from any cause. The secondary outcomes were hospitalization due to worsened HF and occurrence of ventricular tachyarrhythmias.

RESULTS

Of the 103 CRT patients, 53 (51%) showed narrowing fQRS. Left ventricular end-diastolic volume and end-systolic volume were significantly reduced (both p < .001), and the left ventricular ejection fraction was significantly increased (p < .001) after CRT in patients with narrowing fQRS, but not in patients with nonnarrowing fQRS. During a median follow-up period of 33 months, patients with narrowing fQRS exhibited better survival than patients with nonnarrowing fQRS (p = .007). A lower incidence of hospitalization due to worsened HF (p < .001) and a lower occurrence of ventricular tachyarrhythmias (p = .071) were obtained in patients with narrowing fQRS. After adjusting for confounding variables, narrowing fQRS was associated with a low risk of mortality (HR 0.27, p = .006).

CONCLUSION

Our results suggested that narrowing fQRS on SAECG after CRT implantation predicts LV reverse remodeling and long-term outcomes in nonischemic HF patients.

Management of Arrhythmias in Heart Failure

Heart failure patients are predisposed to develop arrhythmias. Supraventricular arrhythmias can exacerbate the heart failure symptoms by decreasing the effective cardiac output and their control require pharmacological, electrical, or catheter-based intervention. In the setting of atrial flutter or atrial fibrillation, anticoagulation becomes paramount to prevent systemic or cerebral embolism. Patients with heart failure are also prone to develop ventricular arrhythmias that can present a challenge to the managing clinician. The management strategy depends on the type of arrhythmia, the underlying structural heart disease, the severity of heart failure, and the range from optimization of heart failure therapy to catheter ablation. Patients with heart failure, irrespective of ejection fraction are at high risk for developing sudden cardiac death, however risk stratification is a clinical challenge and requires a multiparametric evaluation for identification of patients who should undergo implantation of a cardioverter defibrillator. Finally, patients with heart failure can also develop symptomatic bradycardia, caused by sinus node dysfunction or atrio-ventricular block. The treatment of bradycardia in these patients with pacing is usually straightforward but needs some specific issue.

Utility of High-Resolution Magnetocardiography to Predict Later Cardiac Events in Nonischemic Cardiomyopathy Patients With Normal QRS Duration

BACKGROUND

Nonischemic dilated cardiomyopathy (NIDCM) patients, even those with a narrow QRS, are at increased risk for major adverse cardiac events (MACE). We hypothesized that 64-channel magnetocardiography (MCG) would be useful to detect prognostic left intraventricular disorganized conduction (LiDC) by overcoming the limitations of fragmented QRS (fQRS, qualitative definitions, low specificity) and late potential (abnormality undetectable in earlier QRS).Methods and Results:We evaluated LiDC on MCG, defined as significant deviation from a global clockwise left ventricular (LV) activation pattern, and conventional noninvasive predictors of MACE, including fQRS and late potential, in 51 NIDCM patients with narrow QRS (LV ejection fraction, 22±7%; QRS duration, 99±11 ms). MACE was defined as cardiac death, lethal ventricular arrhythmias, or LV assist device (LVAD) implantation. LiDC was present in 22 patients. Baseline characteristics were comparable between patients with and without LiDC, except for the ratio of positive late potential. During a mean follow-up of 2.9 years, MACE developed in 16 NIDCM patients (3 cardiac deaths, 9 lethal ventricular arrhythmias, and 4 LVAD). MACE was more incident in patients with LiDC (13/22) than in those without (3/29, P<0.001). Multivariate analysis revealed LiDC, but not fQRS or late potential, as the strongest independent predictor of MACE (hazard ratio 4.28, 95% confidence interval 1.30-19.39, P=0.015).

CONCLUSIONS

MCG accurately depicts LiDC, a promising noninvasive predictor of MACE in patients with NIDCM and normal QRS.

Electrocardiographic predictors of mortality and sudden cardiac death in patients with end stage renal disease on hemodialysis

Patients with end stage renal disease (ESRD) on hemodialysis experience a high incidence of cardiovascular mortality, and sudden cardiac death (SCD) accounts for approximately 25% of all deaths in this patient population. Despite this high risk of SCD, many non-invasive SCD risk stratification tools that are frequently applied to other patient populations (such as those with prior myocardial infarction and reduced left ventricular systolic function) may be less useful markers of increased SCD risk in ESRD. Improved SCD risk stratification tools for use specifically in patients on hemodialysis are therefore necessary to optimally target use of primary prevention interventions aimed at decreasing SCD incidence. Electrocardiography is an effective, non-invasive SCD risk stratification tool in hemodialysis patients. This article reviews data supporting the association between various ECG parameters (QT interval, spatial QRS-T angle, signal averaged ECG, heart rate variability, and T-wave alternans) and mortality/SCD in the dialysis population. Despite the association between abnormal ECG parameters and SCD, it remains unclear if these abnormal parameters (such as prolonged QT interval) are mechanistically related to SCD and/or ventricular arrhythmias, or if they are simply markers for more severe cardiac disease, such as left ventricular hypertrophy, that may independently predispose to SCD. Current obstacles that impair widespread implementation of ECG risk stratification in the hemodialysis population are also discussed.

[Nonischemic dilated cardiomyopathy. Parameters of autonomic tone]

BACKGROUND

Nonischemic dilated cardiomyopathies (DCM) are the most common reason for heart failure in developed countries after ischemic disease. They often lead to device therapy. Left ventricular ejection fraction as a single parameter to identify patients at risk for sudden cardiac death revealed inconclusive data in patients with DCM.

METHODS

Autonomic tone, measured by classical and innovative parameters of heart rate variability (HRV), heart rate turbulence or baroreceptor reflex, was demonstrated to give valuable prognostic information especially in patients with ischemic disease and after acute myocardial infarction. In patients with DCM, classical parameters of HRV showed inhomogeneous data in a heterogeneous patient collective caused by unsystematic measurement of single parameters in various patient collectives.

RESULTS

Innovative parameters of HRV are promising in patients with DCM and showed prognostic relevance although patient numbers are limited and prospective data are missing. Further studies are needed in this field.

CONCLUSION

Despite the in part convincing evidence for the relevance of autonomic tone as a prognostic marker in patients with DCM, their evaluation is still not part of clinical routine. Additional parameters to estimate the risk of sudden cardiac death are urgently needed.

Multiple autonomic and repolarization investigation of sudden cardiac death in dilated cardiomyopathy and controls

BACKGROUND

Prophylactic defibrillator implantation is recommended in dilated, nonischemic heart disease and left ventricular ejection fraction of ≤0.30 to 0.35. Noninvasive testing should improve accuracy in decision making of prophylactic defibrillator implantation.

METHODS AND RESULTS

We enrolled 60 patients (median age, 57 years) with dilated cardiomyopathy and left ventricular ejection fraction ≤0.50, and 30 control subjects (median age, 59 years) with left ventricular ejection fraction >0.50. The protocol included an initial assessment, a second assessment after 3 years, and a final follow-up: pharmacological baroreflex testing (baroreceptor reflex sensitivity), short-term spectral analysis of heart rate variability (low frequency/high frequency), and long-term time domain analysis (SD of all normal-to-normal R-R intervals), exercise microvolt T wave alternans, and signal-averaged ECG, and corrected QT-time. The median follow-up was 7 years. End points were cardiac death, resuscitated cardiac arrest, and arrhythmic death. Cardiac death was observed in 21 patients. Resuscitated cardiac arrest and arrhythmic death caused by ventricular tachyarrhythmias ≥240 per minute was observed in 7 and 10 patients, respectively. In the single time point analysis, microvolt T wave alternans, baroreceptor reflex sensitivity, and SD of all normal-to-normal R-R intervals at initial testing added significant information regarding cardiac death. Microvolt T wave alternans added information on resuscitated cardiac arrest or arrhythmic death at multiple time points (P<0.001). False-negative microvolt T wave alternans results were seen in 8% of patients.

CONCLUSIONS

Noninvasive testing and left ventricular ejection fraction could not reliably identify patients with dilated cardiomyopathy at risk of fatal ventricular tachyarrhythmias. Therefore, the strategy to confine prophylactic implantable cardioverter-defibrillator implantation to patients with dilated cardiomyopathy and severely reduced LV function should be reconsidered.

Sudden cardiac death in heart failure

Sudden cardiac deaths account for 350,000 to 380,000 deaths in the United States annually. Implantable cardioverter-defibrillators have improved sudden death outcomes in patients with heart failure, but only a minority of patients with defibrillators receives appropriate therapy for ventricular arrhythmias. The risk prediction for sudden death and selection of patients for defibrillators is based largely on left ventricular ejection fraction and heart failure symptoms because there are no other risk stratification tools that can determine the individual patients who will derive the greatest benefit. There are several other pharmacologic strategies designed to prevent sudden death in patients with heart failure.

Conduction remodeling in human end-stage nonischemic left ventricular cardiomyopathy

BACKGROUND

Several arrhythmogenic mechanisms have been inferred from animal heart failure models. However, the translation of these hypotheses is difficult because of the lack of functional human data. We aimed to investigate the electrophysiological substrate for arrhythmia in human end-stage nonischemic cardiomyopathy.

METHODS AND RESULTS

We optically mapped the coronary-perfused left ventricular wedge preparations from human hearts with end-stage nonischemic cardiomyopathy (heart failure, n=10) and nonfailing hearts (NF, n=10). Molecular remodeling was studied with immunostaining, Western blotting, and histological analyses. Heart failure produced heterogeneous prolongation of action potential duration resulting in the decrease of transmural action potential duration dispersion (64 ± 12 ms versus 129 ± 15 ms in NF, P<0.005). In the failing hearts, transmural activation was significantly slowed from the endocardium (39 ± 3 cm/s versus 49 ± 2 cm/s in NF, P=0.008) to the epicardium (28 ± 3 cm/s versus 40 ± 2 cm/s in NF, P=0.008). Conduction slowing was likely due to connexin 43 (Cx43) downregulation, decreased colocalization of Cx43 with N-cadherin (40 ± 2% versus 52 ± 5% in NF, P=0.02), and an altered distribution of phosphorylated Cx43 isoforms by the upregulation of the dephosphorylated Cx43 in both the subendocardium and subepicardium layers. Failing hearts further demonstrated spatially discordant conduction velocity alternans which resulted in nonuniform propagation discontinuities and wave breaks conditioned by strands of increased interstitial fibrosis (fibrous tissue content in heart failure 16.4 ± 7.7 versus 9.9 ± 1.4% in NF, P=0.02).

CONCLUSIONS

Conduction disorder resulting from the anisotropic downregulation of Cx43 expression, the reduction of Cx43 phosphorylation, and increased fibrosis is likely to be a critical component of arrhythmogenic substrate in patients with nonischemic cardiomyopathy.

Sudden cardiac death risk stratification in patients with heart failure

The multiplicity of mechanisms contributing to arrhythmogenesis in patients with heart failure carries obvious implications for risk stratification. If patients having the propensity to develop arrhythmias by these different mechanisms are to be identified, tests must be devised that reveal the substrates or other factors that relate to each mechanism. In the absence of this, efforts to risk stratify patients are likely to be neither cost-effective nor accurate. This article reviews the current knowledge base of risk stratification for sudden death in patients with heart failure, while acknowledging several limitations in the studies examined.

Diagnostic utility of signal-averaged electrocardiography for detection of cardiac sarcoidosis

INTRODUCTION

Cardiac sarcoidosis (CS) occurs in up to 25% of patients with pulmonary involvement. Early diagnosis is critical because sudden death from ventricular arrhythmias can be the initial presentation. We sought to evaluate the diagnostic utility of signal-averaged ECG (SAECG) for detection of cardiac involvement of sarcoidosis.

METHODS

Subjects with biopsy proven sarcoidosis and symptoms suggestive of possible cardiac involvement were included in the cohort. Standard criteria for SAECG were used. Subjects were considered to have CS if they met criteria established by the Japanese Ministry of Health and Welfare modified to include cardiac MRI.

RESULTS

Of the 88 patients in the cohort 27 had evidence of CS independent of the SAECG results. The SAECG was abnormal in 14 of these 27 patients and 11 of the 61 of the subjects without cardiac involvement (P < 0.01). The sensitivity of SAECG detection of CS was 52% with a specificity of 82%. For the entire cohort, SAECG had a positive predictive value (PPV) of 0.56 and a negative predictive value (NPV) of 0.79. Within a subgroup of 67 patients with an unfiltered QRS duration of <100 ms, the specificity for diagnosing cardiac sarcoidosis improves to 100% with a reduced sensitivity of 36.8. Of the SAECG parameters, LAS40 was significantly associated with the diagnosis of cardiac sarcoidosis for the entire cohort (P < 0.01) and among the subgroup of patients with an unfiltered QRS duration of <100 ms (P < 0.01).

CONCLUSIONS

SAECG is a useful screening tool in the evaluation of sarcoidosis for detection of cardiac involvement.

New drugs vs. old concepts: a fresh look at antiarrhythmics

Common arrhythmias, particularly atrial fibrillation (AF) and ventricular tachycardia/fibrillation (VT/VF) are a major public health concern. Classic antiarrhythmic (AA) drugs for AF are of limited effectiveness, and pose the risk of life-threatening VT/VF. For VT/VF, implantable cardiac defibrillators appear to be the unique, yet unsatisfactory, solution. Very few AA drugs have been successful in the last few decades, due to safety concerns or limited benefits in comparison to existing therapy. The Vaughan-Williams classification (one drug for one molecular target) appears too restrictive in light of current knowledge of molecular and cellular mechanisms. New AA drugs such as atrial-specific and/or multichannel blockers, upstream therapy and anti-remodeling drugs, are emerging. We focus on the cellular mechanisms related to abnormal Na⁺ and Ca²⁺ handling in AF, heart failure, and inherited arrhythmias, and on novel strategies aimed at normalizing ionic homeostasis. Drugs that prevent excessive Na⁺ entry (ranolazine) and aberrant diastolic Ca²⁺ release via the ryanodine receptor RyR2 (rycals, dantrolene, and flecainide) exhibit very interesting antiarrhythmic properties. These drugs act by normalizing, rather than blocking, channel activity. Ranolazine preferentially blocks abnormal persistent (vs. normal peak) Na⁺ currents, with minimal effects on normal channel function (cell excitability, and conduction). A similar "normalization" concept also applies to RyR2 stabilizers, which only prevent aberrant opening and diastolic Ca²⁺ leakage in diseased tissues, with no effect on normal function during systole. The different mechanisms of action of AA drugs may increase the therapeutic options available for the safe treatment of arrhythmias in a wide variety of pathophysiological situations.

Prevalence of ventricular late potentials in patients with obstructive sleep apnea syndrome

BACKGROUND

It is known from various cardiac disorders that the presence of ventricular late potentials (VLP) in the signal-averaged electrocardiogram (ECG) is associated with an increased risk of sudden cardiac death.

HYPOTHESIS

In view of the increased cardiovascular mortality of patients with obstructive sleep apnea syndrome (OSAS), we assessed the prevalence of VLP in these patients.

METHODS

In all, 118 consecutive patients with polysomnographically verified OSAS were prospectively studied; 21 snorers without evidence of a sleep-related breathing disorder served as a control group. Signal-averaged ECG and 24-h Holter ECG were performed in all patients and controls, and left ventricular function was determined by radionuclide ventriculography in the OSAS group. Furthermore, patients and controls were followed for up to 45.5 months for arrhythmic events, syncopes, or sudden cardiac death.

RESULTS

An abnormal signal-averaged ECG was seen in seven patients (5.9%) and in one snorer (4.8%). Patients with and without VLP did not differ with respect to age, body mass index, left ventricular ejection fraction, or ectopic activity in the 24-h Holter ECG, but the former had significantly higher mean (standard deviation) apnea/hypopnea indices [55.4 (25.2)/h vs. 37.4 (22.6)/h; p < 0.05]. Of the 118 patients, 110 could be followed for 26.7 (7.9) months. During this period, two patients had syncopes and one patient had sudden cardiac death. The seven patients with VLP remained free of events during the follow-up period, as did the 21 snorers.

CONCLUSIONS

Patients with OSAS have a low prevalence of VLP in the signal-averaged ECG, not exceeding that in normal subjects. Moreover, abnormal signal-averaged ECGs do not appear to be useful as a prognostic marker.

Cytokines, interstitial collagen and ventricular remodelling in dilated cardiomyopathy

BACKGROUND

Dilated cardiomyopathy (DCM) is associated with myocardial fibrosis, and proinflammatory cytokines may play a role in this.

METHODS

N-terminal type I and III procollagen propeptides (PINP, PIIINP) and cross-linked telopeptide of type I collagen (ICTP) were measured from serum samples of 73 patients with DCM and 56 age and sex matched controls. Circulating cytokine levels were determined in DCM patients.

RESULTS

Serum levels of PINP and PIIINP were lower in patients than in controls (p<0.05 and p=0.001). In patients with DCM, the levels of PIIINP and ICTP correlated significantly with each other (p<0.01), and the proinflammatory cytokines, tumor necrosis factor alpha (TNF-alpha) and interleukin-6 (IL-6), correlated positively with ICTP (p<0.001, p<0.05), PIIINP/PINP ratio (p<0.05, p<0.01) and left atrial size (p<0.01, p<0.05). Presence of atrial fibrillation was associated with lower serum PINP level and higher PIIINP/PINP ratio (p<0.05).

CONCLUSIONS

Our results suggest that interstitial myocardial collagen metabolism is altered in DCM patients and regulated by proinflammatory cytokines. These changes in collagen metabolism are associated with presence of atrial fibrillation, but do not reflect left ventricular remodelling. Treatment with beta-blockers and inhibitors of the renin angiotensin aldosterone system seem to effectively inhibit overall type I and III collagen syntheses.

SCD in patients with cardiomyopathy: use of microvolt T-wave alternans and other noninvasive tests for risk stratification and prevention of SCD

Based on current guidelines, most electrophysiologists today are implanting cardioverter-defibrillators (ICDs) using a low left ventricular ejection fraction alone as the sole stratifier for the risk of sudden cardiac death. However, left ventricular ejection fraction is a better marker of total mortality than sudden death. As a result, this strategy is flawed because it exposes many patients to the risk and cost of ICD therapy without its benefits. Primary prevention trials based on this strategy show that the rate of appropriate ICD shocks is only 5% to 10% per year. We believe that the effectiveness of ICD therapy can be improved by the use, in addition to ejection fraction, of one or more of the noninvasive tests, which are reviewed in this article. Such tests are more adequate to evaluate the arrhythmogenic substrate of the patient than the left ventricular ejection fraction alone. Whether any of these tests can help us identify the patients at the lowest risk of sudden death, who could safely avoid ICD implant, remains to be determined.

A Prospective Study on the Risk-Stratification for Patients With Non-Sustained Ventricular Tachycardia Using a Novel Algorithm

BACKGROUND

The therapeutic strategy for non-sustained ventricular tachycardia (NSVT), considered as a risk-stratifier for sudden cardiac death (SCD), still remains undetermined.

METHODS AND RESULTS

In the present study 222 of 4,079 patients (5.4%) hospitalized with NSVT during 2002 to 2004 were prospectively evaluated using an algorithm for risk-stratification according to each type of structural heart disease. The algorithm comprises the left ventricular ejection fraction, signal-averaged electrocardiography, programmed ventricular stimulation and the family history of SCD. Of the 222 patients, 151 (68.0%) were successfully risk-stratified and 32 patients consequently received an implantable cardioverter defibrillator (ICD) (21.2%; algorithm-ICD group). The remaining 119 patients without an ICD (algorithm-observation group) were observed. During 27.7+/-11.4 months of follow-up, the patients in the algorithm-ICD group had a significantly higher prevalence of tachyarrhythmic events than did those in the algorithm-observation group (9/32 vs 1/119; p<0.05). In the algorithm-ICD group, 2, 1 and 6 patients experienced an SCD, aborted SCD and appropriate ICD intervention, respectively, while there was only 1 SCD in the algorithm-observation group.

CONCLUSIONS

The proposed algorithm for risk-stratification of patients with NSVT may be feasible for appropriate selection of high-risk patients and candidates for prophylactic ICD implantation.

Non-Invasive Detection of Latent Cardiac Conduction Abnormalities in Patients With Pulmonary Sarcoidosis Application of Signal Averaged Electrocardiogram

BACKGROUND

Electrocardiographic conduction abnormalities including development of atrioventricular block, bundle branch block or ventricular arrhythmias are characteristic manifestations of cardiac sarcoidosis (CS). The present study seeks to show the minute conduction abnormality by detection of late potentials (LP) on signal averaged electrocardiogram (SAECG).

METHODS AND RESULTS

Ten patients with CS, 52 patients with pulmonary sarcoidosis (PS) but no obvious cardiac manifestations and 52 normal controls were studied. All participants underwent SAECG to detect LP. In patients with CS (the CS group), LP were detected in 8 patients (80%). In 52 patients with PS, LP were detected in 25 patients (46.2%, PS-LP(+) group), comparing only 3 (5.8%) of normal controls (p<0.0001). The remaining 27 patients with PS with negative LP were classified in the PS-LP(-) group. In the CS group, premature ventricular contraction frequency on Holter's monitoring and plasma B-type natriuretic peptide concentrations were significantly higher than those in the PS group. However, no significant difference in these parameters between PS-LP(+) and PS-LP(-) groups were found.

CONCLUSIONS

In the PS patients without obvious cardiac manifestations, LP were detected as high as 46.2%, suggesting latent minute conduction abnormality. The higher incidence of LP in PS might be considered as an expression of latent myocardial fibrosis. Close follow-up is needed in these patients.

Does the abnormal signal-averaged electrocardiogram predict future appropriate therapy in patients with implantable cardioverter-defibrillators?

BACKGROUND

Several studies have documented the prognostic significance of the signal-averaged electrocardiogram (SAECG) both after myocardial infarction and nonischemic cardiomyopathy. However, whether the SAECG can identify patients with implantable cardioverter-defibrillator (ICD) who receive appropriate therapy has not been hitherto completely investigated.

METHODS

Between August 2002 and August 2004, 83 consecutive ICD patients who had had SAECGs recorded were enrolled in this study. All patients were followed up in the outpatient ICD clinic, and interrogated electrograms were collected.

RESULTS

Over 9.0 +/- 2.8 months of follow-up, 27 (32%) patients had appropriate ICD therapy for ventricular tachycardia or fibrillation; 15 (55.6%) patients had abnormal; and the remaining 12 (44.4%) had normal SAECGs. Of the 56 patients with no appropriate therapy, 27 (48.2%) and 29 (51.8%) patients had abnormal and normal SAECGs, respectively. There were no statistically significant differences between the 2 groups in SAECG findings (P = .41). A Cox regression analysis showed that the left ventricular ejection fraction was the only predictor of appropriate therapy (P = .02). Subgroup analysis of the patients with coronary artery disease and spontaneous monomorphic ventricular tachycardia indicated that left ventricular ejection fraction (P = .03) and abnormal SAECG (P = .02) were predictors of appropriate therapy.

CONCLUSIONS

Our data demonstrate that except for the subgroup of patients with coronary artery disease presenting with monomorphic ventricular tachycardia, the SAECG did not predict ventricular tachyarrhythmia recurrence and, hence, appropriate ICD therapy. Thus, SAECG findings should generally not be a factor in decision for ICD implantation.

Prognostic value of the QRS duration in patients with heart failure: a subgroup analysis from 24 centers of Val-HeFT

BACKGROUND

This study investigated whether QRS duration (QRS D) is a prognostic indicator in patients with heart failure (New York Heart Association [NYHA] classes II-IV).

METHODS AND RESULTS

This subgroup analysis included 248 patients with heart failure recruited in the German centers of the Valsartan Heart Failure Trial (Val-HeFT). Mean age was 60 years, mean NYHA class was 2.3, and mean left ventricular ejection fraction (EF) was 27.9%. Electrocardiograms were recorded and analyzed at the beginning of the study, at 2 weeks, 4 months, 1 year, and 2 years. The mean observation period for mortality was 25 months. Patients > or = 65 years and patients with an EF <20% had a significantly longer QRS D (P = .02; P = .0005). NYHA class, etiology of heart failure, therapy with angiotensin-converting enzyme inhibitors, amiodarone or beta-blockers, implanted defibrillator, and atrial fibrillation had no significant influence on QRS D. Total mortality was 9%: 14 patients died suddenly, 7 from heart failure, 2 from noncardiac causes. Kaplan-Meier plots show significantly different survival rates for patients with QRS D <120 ms, QRS D 120-159 ms, or QRS D > or = 160 ms (P = .0085). Multivariate analysis showed that QRS D was the only independent risk factor for all-cause mortality (P = .008). NYHA class, EF, atrial fibrillation, age, and gender failed to qualify as independent prognostic factors.

CONCLUSION

QRS duration in the surface electrocardiogram is an easily obtainable parameter with a significant prognostic impact in patients with congestive heart failure and a reduced EF. In this German subgroup of Val-HeFT patients, it was an independent predictor of all-cause mortality.

Conduction Abnormalities in Nonischemic Dilated Cardiomyopathy: Basic Mechanisms and Arrhythmic Consequences

Heart failure is associated with an increased risk of sudden death caused by ventricular tachyarrhythmias. The role of altered repolarization in the formation of arrhythmogenic substrates and triggers has been studied at multiple levels of integration, including molecular, cellular, tissue, and organ levels. Numerous studies have focused on conduction abnormalities in the context of ischemic heart disease and left ventricular dysfunction after myocardial infarction. However, ischemia alone, independent of left ventricular dysfunction, alters conduction by depressing membrane excitability and increasing tissue resistivity. In this review, we focus on the role of conduction abnormalities in the genesis of arrhythmias in nonischemic dilated cardiomyopathy and discuss their underlying cellular and molecular mechanisms, including changes in myocyte excitability, the extracellular matrix, and cell-to-cell coupling. We compare the nature of conduction slowing in ischemic and nonischemic heart failure and highlight the mechanistic differences between the two disease etiologies.

Standard Electrocardiographic and Signal-Averaged Electrocardiographic Changes in Congestive Heart Failure

A 54-year-old man with congestive heart failure and peripheral edema was monitored during treatment with serial electrocardiograms (ECGs) and two signal-averaged ECGs. Weights and a host of ECG parameters were monitored. ECGs recorded in the 5 years before his index admission were also considered in the quantitative ECG analysis. Amelioration of his peripheral edema was associated with reduction of his weight and increase in the QRS and P-wave amplitudes, and duration in QRS complexes and QT intervals in the ECGs, but unchanged signal-averaged ECGs. This case report provides insight into the mechanism of the change in QRS duration in ECGs during changing edematous states resulting from clinical deterioration or improved compensation in patients with congestive heart failure.

[Risk stratification in congestive heart failure]

Congestive heart failure remains a severe condition. Risk stratification is necessary to assess the prognosis and discuss the potential timing of heart transplant. Numerous criteria have been used, which may be combined to define prognostic scores which, however, are rarely used in routine. A few items, however, may be used to stratify the risk of mortality and sudden death.

Role of noninvasive studies in risk stratification for sudden cardiac death

Sudden cardiac death (SCD) is one of the leading causes of mortality in developing countries. To prevent SCD, it is crucial to have effective tools for identifying patients at risk, given that there are now effective devices and medications that can prevent SCD. Two noninvasive electrocardiographic tools have been approved by the Food and Drug Administration and are being used clinically for identifying patients at risk for SCD: the signal-averaged electrocardiogram (SAECG) and T-wave alternans (TWA). This article reviews each of these approaches and includes a discussion of the mechanisms and a summary of the clinical studies published to date.

Filtered QRS Duration on Signal-Averaged Electrocardiography Predicts Inducibility of Ventricular Tachycardia in Arrhythmogenic Right Ventricle Dysplasia

Treatment of arrhythmogenic right ventricular dysplasia (ARVD) is mostly based on the prevention of sudden cardiac death that results from arrhythmias. A clinical history suggestive of ARVD requires careful evaluation including electrophysiological study. The potential ability to identify those patients who will have inducible VT with electrophysiological study will enable better risk stratification and selection of vulnerable patients for electrophysiologically guided therapy. The purpose of the study was to evaluate the predictive ability of signal-averaged electrocardiography (SAECG) to predict inducibility of VT in patients with ARVD. The patient population consisted of 31 ARVD patients diagnosed with McKenna's criteria who underwent electrophysiological study. Electrophysiological study was considered positive if sustained monomorphic VT was induced. The sensitivity, specificity, and predictive accuracy of various SAECG criteria for inducibility of sustained monomorphic VT were also calculated. Twenty-one patients had inducible VT. The filtered QRS duration (fQRS), duration of signal <40 uV (LAS40), and root mean square voltage in the last 40 ms of QRS duration (RMS40) in ARVD patients induced versus noninduced were 122 +/- 21 and 103 +/- 8 ms (P=0.007), 45 +/- 20 and 28 +/- 14 ms (P=0.02), 19 +/- 19 and 32 +/- 22 uV (0.03), respectively. The ejection fractions were comparable in both groups. fQRS duration > or =110 ms had sensitivity of 91%, specificity of 90%, and a total predictive accuracy of 90% in predicting inducibility of VT in these patients. Filtered QRS duration on SAECG is predictive of electrophysiological study outcome in ARVD. Further studies will be needed to determine if SAECG results can predict the development of ventricular arrhythmias during follow-up.

Correlation of Connexin43 Expression and Late Ventricular Potentials in Nonischemic Dilated Cardiomyopathy

Nonischemic dilated cardiomyopathy (DCM) is associated with a high risk of sudden cardiac death. Signal-averaged electrocardiography (SAECG) is a useful clinical tool for detecting late ventricular potentials (LP). Gap junction alterations have recently been shown to be involved in the pathogenesis of ventricular arrhythmias in DCM; however, the possible relationship between gap junctional connexin43 (C x 43) expression and SAECG has not yet been evaluated. In the present study 16 patients (47+/-13 years) with DCM who had undergone SAECG testing were evaluated. In each patient, the expression of C x 43 proteins was qualitatively and quantitatively determined using immunoconfocal microscopy and right ventricular biopsy specimens. The level of expression of C x 43 protein was defined as the proportion of tissue area occupied by C x 43 (percent tissue area) in each test area. The abundance and distribution of the C x 43 signal was assessed in relation to LP. Late ventricular potentials were positive in 5 patients (LP (+) group) and negative in 11 patients (LP (-) group). The incidence of sustained ventricular tachycardia in the LP (+) group was higher than that in the LP (-) group (80% vs 18%, p=0.04). The percent tissue area of C x 43 in the LP (+) group was significantly lower than that in the LP (-) group (p=0.02). Furthermore, C x 43 protein in the LP (+) group was distributed more heterogeneously than that in the LP (-) group (p=0.001). The heterogeneous expression of C x 43 protein may contribute to impaired ventricular conduction, which may be related to the LP detected on SAECG.

Prevalence and incidence of arrhythmias and sudden death in heart failure

Patients with heart failure are prone to a variety of arrhythmias, symptomatic and asymptomatic, that are prognostically significant and have an important bearing on the management of these patients. However there are some inherent problems in assessing the frequency of these arrhythmias within a large patient population, due to a lack of uniformity in defining heart failure and the transient nature of these rhythms. Patients with heart failure commonly die suddenly. The causes of these deaths are difficult to ascertain accurately and are often presumed arrhythmic. With the advent of effective interventions to prevent sudden death, accurately defining the causal relationship between the arrhythmias and sudden death has assumed great importance to appropriately target therapy. Several attempts have been made to predict such deaths on the basis of non-invasive and invasive diagnostic investigations with variable success. In this article we review the incidence and prevalence of atrial and ventricular arrhythmias and sudden deaths in epidemiological studies, surveys and randomised control trials of patients with heart failure. We discuss the prognostic significance of these arrhythmias, the inherent problems in their diagnosis and whether their presence predicts the risk of sudden deaths and the mode of such deaths in the heart failure population. The role of various investigations in risk stratification of sudden death has also been discussed.

Occurrence of ventricular late potentials in patients with active acromegaly

OBJECTIVE

Patients with acromegaly have an increased risk of ventricular dysrhythmias and sudden death. Late potentials in a signal-averaged electrocardiogram (SAECG), a predictor of ventricular dysrhythmias, are frequently seen in patients after previous myocardial infarction, but little is known about the prevalence of late potentials in acromegaly. The aim of our study was to investigate the prevalence of late potentials in patients with acromegaly and their relation to the activity of the disease and to myocardial hypertrophy.

PATIENTS

The study included 48 patients with acromegaly [27 males, 21 females, mean age 52.3 +/- 14.2 years, 16 active disease, 32 cured or 'well controlled', under treatment with sandostatin analogues (12/32)] and 38 healthy volunteers as a control group.

RESULTS

Late potentials were detected in 9/16 (56%) patients with active acromegaly vs. 2/32 (6%) with cured/well controlled acromegaly (P = 0.001), defined as normal age-related IGF-1 levels and GH levels suppressible below 1 microg/l after an oral glucose load (75 g). Late potentials were not related to muscle mass index (127 +/- 35 active vs. 123 +/- 34 g/m2 cured/well controlled). The association of disease activity with the detection of late potentials was independent of age, gender, duration of the disease and body mass index. In comparison to the control group, the prevalence of late potentials was significantly higher in patients with acromegaly (23%) than in the control group (0%; P < 0.001).

CONCLUSIONS

Late potentials in the SAECG are frequently seen in active acromegaly and may represent an early and sensitive parameter to detect myocardial injury in acromegaly.