Standards for analysis of ventricular late potentials using high-resolution or signal-averaged electrocardiography: a statement by a task force committee of the European Society of Cardiology, the American Heart Association, and the American College of Cardiology

Ventricular Depolarization Abnormalities and Their Role in Cardiac Risk Stratification - A Narrative Review

Ventricular depolarization refers to the electrical activation and subsequent contraction of the ventricles, visible as the QRS complex on a 12-lead electrocardiogram (ECG). A well-organized and efficient depolarization is critical for cardiac function. Abnormalities in ventricular depolarization may indicate various pathologies and can be present in all leads if the condition is general, or in a subgroup of anatomically contiguous leads if the condition is limited to the corresponding anatomic location of the heart. Furthermore, the assessment of depolarization abnormalities on the ECG may either be identified visually or this may depend on further processing. In recent decades, assessment of depolarization abnormalities has received a lot of attention for cardiac risk stratification. This risk stratification aims to identify patients at high risk of adverse cardiac events, to tailor preventive or therapeutic interventions. In this review, we provide an oversight of different techniques for assessing abnormal ventricular depolarization and their value in diagnosing certain conditions, in risk stratification of adverse events, and in guiding therapeutic decisions. This includes QRS alterations directly corresponding to cardiac conditions, such as bundle branch blocks, or the presence of a delta wave, and also metrics aiming to qualitatively or quantitatively assess myocardial scarring, such as QRS (micro)fragmentation and QRS-scoring, and techniques assessing abnormal late depolarizations, such as signal-averaged ECG. While most established assessments of abnormal depolarization rely on human interpretation and are limited by visual detection, recently introduced analyses, such as QRS micro-fragmentation, aim to tackle these limitations. Besides eliminating bias, these automated analyses bypass the need for human interpretation, thereby paving the way for large population studies.

Correlation between Epsilon Wave and Late Potentials in Arrhythmogenic Right Ventricular Cardiomyopathy-Do Late Potentials Define the Epsilon Wave?

Introduction: Arrhythmogenic right ventricular cardiomyopathy (ARVC) is a genetic disorder characterised by progressive fibrosis predominantly of the right ventricular (RV) myocardium, resulting in life-threatening arrhythmias and heart failure. The diagnosis is challenging due to a wide spectrum of clinical symptoms. The important role of ECG was covered in the current diagnostic criteria. The role of the epsilon wave (EW) is still under discussion. Aim: The aim of the study was to examine a potential association between the EW and late ventricular potentials (LPs) in ARVC patients (pts). The correlation between RV dilatation or dysfunction and LPs/EW was also analysed. Methods: The ARVC group consisted of 81 pts (53 men, aged 20-78 years) fulfilling 2010 International Task Force Criteria. 12-lead ECG, LPs, Holter, and ECHO were performed in all pts. The presence of EW was analysed in ECG by 3 investigators. LPs were detected by signal-averaged ECG (SAECG). SAECG was considered positive for LPs when at least two of the three following criteria were met: (1) the filtered QRS duration (fQRS) ≥ 114 msec; (2) the duration of the final QRS fragment in which low-amplitude signals lower than 40 μV are recorded (LAS-40 > 38 msec); and (3) the root mean square amplitude of the last 40 milliseconds of the fQRS complex (RMS-40 < 20 μV). The results were compared with a reference group consisting of 53 patients with RV damage in the course of atrial septum defect (ASD) or Ebstein's Anomaly (EA). Results: In the ARVC group, a significant relationship was observed between the occurrence of EW and the presence of LPs. EW was more common in the LP+ than in the LP- patients (48.1% vs. 6.9%, p < 0001; OR 12.5; 95% CI [2.691-58.063]). In ARVC pts, RVOT > 36 mm, RVIT > 41 mm, and RV S' < 9 cm/s were observed significantly more often in the LPs+ than in the LPs- group (OR [95% CI]: 8.3 [2.9-1.5], 6.4 [2.2-19.0] and 3.6 [1.1-12.2], respectively). In the ARVC group, any of fQRS > 114 ms, LAS > 38 ms, and RMS < 20 μV were significantly more frequent in EW+ pts. In multivariate analysis, the independent factors of the EW were LAS-40 and RV S'. In the LPs- subgroup, RVOT > 36 mm was more frequent in ASD/EA than in ARVC (70.4% vs. 25%, p = 0.002). Similarly, in the LPs- subgroup, RVIT > 41 mm was encountered more frequently in ASD/EA than in ARVC (85.2% vs. 48.3%, p = 0.004). Conclusions: In ARVC, there is an association between EW and LPs, with both probably resulting from the same process of fibrofatty substitution of the RV myocardium. Although RV dilatation is common in ASD and EA, it does not correlate with LPs.

Association between the number of altered late potential criteria and increased arrhythmic risk in Brugada syndrome patients

BACKGROUND

Brugada syndrome (BrS) is associated with abnormal electrophysiological properties at right ventricular epicardium, consisting of fragmented electrograms extending well beyond QRS termination. We aimed to evaluate the utility of signal-averaged electrocardiogram (SA-ECG) for the noninvasive assessment of late potentials (LP) and risk stratification of BrS patients.

METHODS

A prospective, observational, single-center study of BrS patients is submitted to SA-ECG with the determination of the total filtered QRS duration (fQRS), root mean square voltage of the 40 ms terminal portion of the QRS (RMS40), and duration of the low-amplitude electric potential component of the terminal portion of the QRS (LAS40). LP were considered positive when above standard cut-offs: fQRS > 114 ms, RMS40 < 20 µV, and LAS40 > 38 ms. The rates of malignant arrhythmic events (MAEs), defined as sudden death or appropriate shocks, were compared in relation to clinical characteristics and SA-ECG findings.

RESULTS

A total of 106 BrS patients (mean age, 48 ± 12 years, 67.9% male) were studied, 49% with type-1 spontaneous pattern and 81% asymptomatic. During a median follow up of 4.7 years, 10 patients (7.1%) suffered MAEs, including 4 sudden deaths. The presence of LP was significantly associated with the arrhythmic risk, which increased with the number of altered LP criteria. In comparison to the patients who had none or 1 altered LP criterium, MAE risk was 4.7 times higher in those with 2 altered criteria and 9.4 times higher in those with 3 altered LP criteria.

CONCLUSIONS

SA-ECG may be a useful tool for risk stratification in BrS. The presence of 2 or 3 abnormal LP criteria could identify a subset of asymptomatic patients at high risk of arrhythmic events.

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.

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.

Electrophysiological features in acromegaly: re-thinking the arrhythmic risk?

BACKGROUND

Acromegaly is disease associated with a specific cardiomyopathy. Hitherto, it has been widely understood that acromegaly carries an increased risk of arrhythmia.

PURPOSE

In this review we show that evidences are limited to a small number of case-control studies that reported increased rates of premature ventricular beats (PVB) but no more significant arrhythmia. In contrast, there are several studies that have reported impaired preclinical markers of arrhythmia, including reduced heart rate variability, increased late potentials, QT interval dispersion, impaired heart rate recovery after physical exercise and left ventricular dysynchrony. Whilst these markers are associated with an adverse cardiovascular prognosis in the general population, they do not have a high independent positive predictive accuracy for arrhythmia. In acromegaly, case reports have described sudden cardiac death, ventricular tachyarrhythmia and advanced atrio-ventricular block that required implantation of a cardio-defibrillator or permanent pacemaker. Treatment with somatostatin analogues can reduce cardiac dysrhythmia in some cases by reducing heart rate, PVBs and QT interval. Pegvisomant reduces mean heart rate. Pasireotide is associated with QT prolongation. In the absence of good quality data on risk of arrhythmia in acromegaly, the majority of position statements and guidelines suggest routine 12-lead electrocardiography (ECG) and transthoracic echocardiography (TTE) in every patient at diagnosis and then follow up dependent on initial findings.

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.

Complexities in cardiovascular rhythmicity: perspectives on circadian normality, ageing and disease

Biological rhythms exist in organisms at all levels of complexity, in most organs and at myriad time scales. Our own biological rhythms are driven by energy emitted by the sun, interacting via our retinas with brain stem centres, which then send out complex messages designed to synchronize the behaviour of peripheral non-light sensing organs, to ensure optimal physiological responsiveness and performance of the organism based on the time of day. Peripheral organs themselves have autonomous rhythmic behaviours that can act independently from central nervous system control but is entrainable. Dysregulation of biological rhythms either through environment or disease has far-reaching consequences on health that we are only now beginning to appreciate. In this review, we focus on cardiovascular rhythms in health, with ageing and under disease conditions.

Qt Dispersion and Signal-Averaged Electrocardiogram in Hemodialysis and Capd Patients

Objective

The aim of this study was to compare QT dispersion (QTd) and signal-averaged electrocardiogram (SA-ECG) parameters that may predict risk of malignant arrhythmias in patients on hemodialysis (HD), on continuous ambulatory peritoneal dialysis (CAPD), and in controls.

Setting

Controlled cross-sectional study in a tertiary- care setting.

Patients

28 HD (M/F 18/10; mean age 32 ± 9 years), 29 CAPD (M/F 17/12; mean age 34 ± 10 years), and 29 healthy controls (M/F 17/12; mean age 32 ± 8 years) were included.

Interventions

On ECG, minimum (QTmin) and maximum (QTmax) QT duration and their difference (QTd) were measured. In SA-ECG, duration of filtered QRS, HFLA signals less than 40 μV, and RMS voltage (40 ms) were also measured.

Results

Higher serum Ca2+ and lower K+ levels were found in CAPD compared to HD. All QT parameters were increased in HD and CAPD compared to controls. QT dispersion was significantly prolonged in HD compared to CAPD. In HD, QTd was correlated with left ventricular (LV) mass index ( r = 0.53, p = 0.004), but not in CAPD ( r = -0.09, p = 0.63). QT dispersion was significantly prolonged in patients with LV hypertrophy compared to patients without hypertrophy on HD (68 ± 18 ms vs 49 ± 18 ms, p = 0.008). In the analysis of SA-ECG, 3 of the 28 (11%) HD and 2 of the 29 (7%) CAPD patients had abnormal late potentials. Patients on HD and CAPD had significantly higher filtered-QRS duration compared to controls (105 ± 15 ms and 104 ± 12 ms vs 95 ± 5 ms, respectively, p = 0.04). Patients with LV hypertrophy had higher filtered-QRS duration compared to patients without hypertrophy (109 ± 12 ms vs 95 ± 8 ms, p < 0.001).

Conclusion

Dialysis patients had prolonged QTd and increased filtered-QRS duration in SA-ECG compared to controls. Patients on HD had longer QTd than patients on CAPD. QTd has been correlated to LV mass index in HD, but not in CAPD. This difference might be due to the effect of different dialysis modalities on electrolytes, especially the higher serum Ca2+ levels.

Efficient Detection of Ventricular Late Potentials on ECG Signals Based on Wavelet Denoising and SVM Classification

The analysis of cardiac signals is still regarded as attractive by both the academic community and industry because it helps physicians in detecting abnormalities and improving the diagnosis and therapy of diseases. Electrocardiographic signal processing for detecting irregularities related to the occurrence of low-amplitude waveforms inside the cardiac signal has a considerable workload as cardiac signals are heavily contaminated by noise and other artifacts. This paper presents an effective approach for the detection of ventricular late potential occurrences which are considered as markers of sudden cardiac death risk. Three stages characterize the implemented method which performs a beat-to-beat processing of high-resolution electrocardiograms (HR-ECG). Fifteen lead HR-ECG signals are filtered and denoised for the improvement of signal-to-noise ratio. Five features were then extracted and used as inputs of a classifier based on a machine learning approach. For the performance evaluation of the proposed method, a HR-ECG database consisting of real ventricular late potential (VLP)-negative and semi-simulated VLP-positive patterns was used. Experimental results show that the implemented system reaches satisfactory performance in terms of sensitivity, specificity accuracy, and positive predictivity; in fact, the respective values equal to 98.33%, 98.36%, 98.35%, and 98.52% were achieved.

Risk Stratification for Sudden Cardiac Death After Myocardial Infarction

Sudden cardiac death (SCD) accounts for ∼50% of mortality after myocardial infarction (MI). Most SCDs result from ventricular tachyarrhythmias, and the tachycardias that precipitate cardiac arrest result from multiple mechanisms. As a result, it is highly unlikely that any single test will identify all patients at risk for SCD. Current guidelines for use of implantable cardioverter-defibrillators (ICDs) to prevent SCD are based primarily on measurement of left ventricular ejection fraction (LVEF). Although reduced LVEF is associated with increased total cardiac mortality after MI, the focus of current guidelines on LVEF omits ∼50% of patients who die suddenly. In addition, there is no evidence of a mechanistic link between reduced LVEF and arrhythmias. Thus, LVEF is neither sensitive nor specific as a tool for post-MI risk stratification. Newer tests to screen for predisposition to ventricular arrhythmias and SCD examine abnormalities of ventricular repolarization, autonomic nervous system function, and electrical heterogeneity. These tests, as well as older methods such as programmed stimulation, the signal-averaged electrocardiogram, and spontaneous ventricular ectopy, do not perform well in patients with LVEF ≤30%. Recent observational studies suggest, however, that these tests may have greater utility in patients with LVEF >30%. Because SCD results from multiple mechanisms, it is likely that combinations of risk factors will prove more precise for risk stratification. Prospective trials that evaluate the performance of risk stratification schema to determine ICD use are necessary for cost-effective reduction of the incidence of SCD after MI.

Marginal Component Analysis of ECG Signals for Beat-to-Beat Detection of Ventricular Late Potentials

Heart condition diagnosis based on electrocardiogram signal analysis is the basic method used in prevention of cardiovascular diseases, which are recognized as the leading cause of death globally. To anticipate the occurrence of ventricular arrhythmia, the detection of Ventricular Late Potentials (VLPs) is clinically worthwhile. VLPs are low-amplitude and high-frequency signals appearing at the end part of QRS complexes in the electrocardiogram, which can be considered as a robust feature for arrhythmia risk stratification in patients with cardiac diseases. This paper proposes a beat-to-beat VLP detection method based on the the marginal component analysis and investigates its performance taking into account different ratios between QRS and VLP power. After a denoising phase, performed adopting the singular vector decomposition technique, heartbeats characterized by VLP onsets are identified and extracted taking into account the vector magnitude of each high resolution ECG (HR-ECG) record. To evaluate the proposed method performance, a 15-lead HR-ECG database consisting of real VLP-negative and simulated VLP-positive patterns was used. The achieved results highlight the method validity for VLP detection.

Prevalence and long-term prognosis of patients with 'narrower than normal' QRS complexes

Aims

Very narrow QRS have been reported in sudden death survivors but prevalence and prognosis role of narrow QRS is unknown.

Methods and results

546 healthy men between 50 and 60 years (group 1) and 373 similar patients with coronary artery disease (368 men, group 2) underwent signal averaged ECG (SA-ECG) allowing precise measurement of QRS duration. All cause-mortality was determined after 18 ± 3 years follow-up. Mean QRS duration was 97 ± 13 ms in group 1 and 103 ± 16 ms in group 2. Tenth percentile was 84 ms in group 1 and 85 ms in group 2. All cause-mortality in group 1 was 10.4% (57/546): 6/85 in case of QRS <85 ms (7%) and 2/23 (9%) in case of QRS >120 ms (ns). HR for all-cause mortality was 0.75 (95% CI 0.32-1.76, P = 0.52) for QRS <85 ms and 0.86 (95% CI 0.21-3.53, P = 0.84) for QRS >120 ms. All cause mortality in group 2 was 29% (109/373): 7/44 in case of QRS <85 ms (16%) and 22/44 (50%) in case of QRS >120 ms (P = 0.002). HR for all-cause mortality was 0.65 (95% CI 0.29-1.45, P = 0.29) for QRS <85 ms and 1.73 (95% CI 1.02-2.94, P = 0.05) for QRS >120 ms.

Conclusion

QRS duration <80-85 ms can be observed in a significant proportion of middle-aged healthy males and in similar patients with ischemic heart disease. Narrow QRS were not linked to prognosis in any group.

The presence of late potentials after percutaneous coronary intervention for the treatment of acute coronary syndrome as a predictor for future significant cardiac events resulting in re-hospitalization

INTRODUCTION

We previously reported that LP positive patients after percutaneous coronary intervention (PCI) had higher rate of re-hospitalization in the small-scale study (135 patients). In this study, we evaluated correlation between LP and later cardiac events leading to re-hospitalization more extensively in greater population.

METHODS AND RESULTS

A 24-h high-resolution (HR) ambulatory electrocardiogram (ECG) was performed in 421 patients that received PCI for the treatment of acute coronary syndrome (ACS) within 30 days. Various baseline characteristics and post-PCI ECG parameters including LP were examined for correlation with later re-hospitalization. LP was evaluated based on 3 different conditions, i.e., the worst, mean and best values, from 24-h signal-averaged QRS wave data. During the post-PCI follow-up period (611 ± 489.0 days), 90 patients were re-hospitalized due to cardiac events. Multivariate analysis identified only positive LP based on the worst value as an independent predictor for re-hospitalization with OR 2.26. Most of re-hospitalization cases (>75%) were predominantly attributed to ischemic events. LP positive population had significantly higher incidences of ischemic events as well as overall re-hospitalization compared to LP negative population. The predictive power of LP was decreased when it was combined with other variables. The receiver operating characteristic analysis determined the LP cut-off values consistent with the LP positive criteria previously reported and standardized.

CONCLUSION

The presence of LP in the 24-h HR ambulatory ECG post-PCI was an independent predictor for a risk of re-hospitalization due to ischemic cardiac events in ACS patients.

Differential pacing from two sites to diagnose risk of ventricular arrhythmia and death

BACKGROUND

QRS abnormalities may not be apparent in sinus rhythm in electrically stable cardiomyopathy patients who can have quiescent but highly arrhythmogenic substrate. Here, we test the hypothesis that differential changes in QRS construction during right-ventricular apex pacing (RVP) as opposed to atrial pacing (AP) will identify latent substrate for ventricular arrhythmias (VA) and death.

METHODS

Forty patients with cardiomyopathy free of VA underwent baseline 114-electrode body-surface electrocardiogram during AP (100 beats per minute [bpm]) and RVP (100 and 120 bpm). The filtered-averaged QRS at each electrode was deconstructed into individual intra-QRS and post-QRS ventricular myopotentials (V_MP ). The primary outcome was VA or death. Prognostic accuracy of V_MP was validated using V1 to V6 leads in another prospective cohort of 44-cardiomyopathy patients.

RESULTS

Twenty-six patients were eligible for initial analysis. After 5 ± 2 years of follow-up, eight (31%) patients had VA (VA_Pos ) while rest were uneventful (VA_Neg ). During AP₁₀₀ , VA_Pos patients expressed more V_MP than VA_Neg patients (16 ± 1 vs 12 ± 1, P = 0.02). RVP₁₀₀ and RVP₁₂₀ in VA_Pos patients introduced an additional 5.5 ± 0.5 and 6.0 ± 0.5 V_MP (P < 0.0001 vs AP₁₀₀ ). The relative change with RVP₁₂₀ versus AP₁₀₀ in VA_Neg patients exceeded VA_Pos patients by 1.2 ± 0.5 V_MP (P = 0.03). Increment in V_MP count of <8 in lead-V5 with RVP₁₂₀ compared to AP₁₀₀ best predicted VA (area under curve 0.81, P = 0.01). In the validation cohort, primary outcome occurred in 13 (33%) patients. Native QRS features and AP₁₀₀ alone failed to predict primary outcome. Patients with increment in V_MP count of <8 in lead-V5 with RVP₁₂₀ versus AP₁₀₀ had 7.9-fold increased risk of primary outcome (95% confidence interval 1.01, 61.61; P = 0.049).

CONCLUSION

Cardiomyopathy patients at risk of VA or death perturb the QRS less than low-risk patients with differential pacing. This functional response may be useful to identify arrhythmogenic substrate.

T wave alternans extracted from 30-minute short resting Holter ECG recordings predicts mortality in heart failure

BACKGROUND

We extracted T Wave Alternans (TWA) from a 30 minute Short Resting Holter ECG (SRH ECG) in the supine position, as a Total Mortality (TM) predictor in Heart Failure (HF).

METHODS

Signals from 146 HF patients (LVEF = 33 ± 10%), were analyzed with Modified Moving Average method. After 42.1 months, 26 patients died.

RESULTS

(Deceased vs Living group): TWA:31 ± 18 μV vs 25 ± 13 μV(p = 0.05), LVEF:32 ± 10% vs 34 ± 9% (p = 0.5), Heart Rate:73 ± 11 bpm vs 69 ± 12 bpm (p = 0.2), SDNN/HRV:45 ± 42 ms vs 41 ± 29 ms (p = 0.4), QRS:123 ± 26 ms vs 119 ± 29 ms (p = 0.5).Cox regression model adjusted for TWA, LVEF and QRS, revealed that the TWA was an independent TM predictor (H.R.: 1.022, 95% C.I.: 0.999-1.046, p = 0.05).The TWA ≥ 42 μV demonstrated HR: 2.521, (95% C.I.: 0.982-6.472, p = 0.05).

CONCLUSIONS

In severely affected HF patients, TWA from a SRH ECG may be present even during slow resting heart rates and proved to be an important and independent TM predictor. The SRH ECG recording is an efficient and fast method for mortality risk evaluation in HF 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.

H558R, a common SCN5A polymorphism, modifies the clinical phenotype of Brugada syndrome by modulating DNA methylation of SCN5A promoters

BACKGROUND

A common SCN5A polymorphism H558R (c.1673 A > G, rs1805124) improves sodium channel activity in mutated channels and known to be a genetic modifier of Brugada syndrome patients (BrS). We investigated clinical manifestations and underlying mechanisms of H558R in BrS.

METHODS AND RESULTS

We genotyped H558R in 100 BrS (mean age 45 ± 14 years; 91 men) and 1875 controls (mean age 54 ± 18 years; 1546 men). We compared clinical parameters in BrS with and without H558R (H558R+ vs. H558R- group, N = 9 vs. 91). We also obtained right atrial sections from 30 patients during aortic aneurysm operations and compared SCN5A expression and methylation with or without H558R. H558R was less frequent in BrS than controls (9.0% vs. 19.2%, P = 0.028). The VF occurrence ratio was significantly lower (0% vs. 29.7%, P = 0.03) and spontaneous type 1 ECG was less observed in H558R+ than H558R- group (33.3% vs. 74.7%, P = 0.01). The SCN5A expression level was significantly higher and the methylation rate was significantly lower in sections with H558R (N = 10) than those without (0.98 ± 0.14 vs. 0.83 ± 0.19, P = 0.04; 0.7 ± 0.2% vs. 1.6 ± 0.1%, P = 0.004, respectively). In BrS with heterozygous H558R, the A allele mRNA expression was 1.38 fold higher than G allele expression.

CONCLUSION

The SCN5A polymorphism H558R may be a modifier that protects against VF occurrence in BrS. The H558R decreased the SCN5A promoter methylation and increased the expression level in cardiac tissue. An allelic expression imbalance in BrS with a heterozygous H558R may also contribute to the protective effects in heterozygous mutations.

Right ventricular systolic function and mechanical dispersion identify patients with arrhythmogenic right ventricular cardiomyopathy

PURPOSE

To assess right ventricular (RV) regional and global systolic function using feature tracking (FT) in patients with a definite diagnosis of arrhythmogenic right ventricular cardiomyopathy (ARVC) and to investigate if changes in strain amplitude and mechanical dispersion indicate a propensity for arrhythmia.

MATERIALS AND METHODS

Twenty-seven patients fulfilling Task Force Criteria for ARVC and 24 healthy volunteers underwent MR at 1·5 Tesla. Steady-state free precession cine of long-axis slices and a short-axis stack of the RV was acquired. Segmental longitudinal systolic strain amplitude and time-to-peak (TTP) strain were measured in the four- and two-chamber views of the RV.

RESULTS

Compared to controls, patients with ARVC had lower RV ejection fraction (RVEF), (53% vs 57%, P = 0·012) and lower longitudinal strain amplitude in the RV free wall (-20·6 vs -26·3%, P = 0·014) and in the basal part of the RV (-22·8 vs -31·7%, P<0·001). Mechanical dispersion, defined as the standard deviation (SD) of TTP of RV segments, was larger in patients with ARVC (48 ms [21-74] vs 35 ms [13-66 ms], P = 0·02). Patients with ventricular tachycardia (VT) or non-sustained VT had lower RVEF (46% vs 55%, P = 0·008), but did not have significantly lower RV strain amplitude (-19·5% vs 21·0%, P = 0·073) and no signs of mechanical dispersion (49 ms vs 48 ms, P = 0·861) compared to patients without arrhythmia.

CONCLUSION

ARVC patients had lower longitudinal absolute strain amplitude in basal RV segments and increased mechanical dispersion compared to healthy volunteers, but the presence of mechanical dispersion was not predictive of ventricular arrhythmia.

A Review of Automated Methods for Detection of Myocardial Ischemia and Infarction Using Electrocardiogram and Electronic Health Records

There is a growing body of research focusing on automatic detection of ischemia and myocardial infarction (MI) using computer algorithms. In clinical settings, ischemia and MI are diagnosed using electrocardiogram (ECG) recordings as well as medical context including patient symptoms, medical history, and risk factors-information that is often stored in the electronic health records. The ECG signal is inspected to identify changes in the morphology such as ST-segment deviation and T-wave changes. Some of the proposed methods compute similar features automatically while others use nonconventional features such as wavelet coefficients. This review provides an overview of the methods that have been proposed in this area, focusing on their historical evolution, the publicly available datasets that they have used to evaluate their performance, and the details of their algorithms for ECG and EHR analysis. The validation strategies that have been used to evaluate the performance of the proposed methods are also presented. Finally, the paper provides recommendations for future research to address the shortcomings of the currently existing methods and practical considerations to make the proposed technical solutions applicable in clinical practice.

Ventricular late potential in cardiac syndrome X compared to coronary artery disease

BACKGROUND

Although ventricular late potential (VLP) was extensively studied in risk stratification of myocardial infarction (MI) patients, comparable researches evaluating presence of VLP in MI-free coronary artery disease (CAD) and cardiac syndrome X (CSX) subjects are scarce. This study aimed to compare presence of VLP between CSX and CAD patients.

METHODS

Signal average ECG (SAECG) was performed to 49 patients with a history of typical cardiac pain before undergoing diagnostic coronary angiography (DCA) in Al-Shaab cardiac center, Khartoum, Sudan. QRS duration, duration of the terminal part of the QRS complex with amplitude less than 40 microvolts (LAS40) and the root mean square voltage of the terminal 40 milliseconds (RMS40) of the filtered QRS complex were identified for each patient. Presence of two or more of QRS duration > 120 ms, RMS40 > 38 ms and LAS40 < 20 μV was considered indicative of VLP. Associations between VLP and patients grouped according to DCA results were assessed using appropriate statistical tests.

RESULTS

VLP was present in 11.11% (3.63%-24.66%) and 15.38% (2.66%-42.23%) of patients with CAD and CSX respectively. Presence of VLP was comparable in patients with CAD and CSX (OR = 0.69, 95% CI = 0.11-6.05, P = 0.692), even after controlling for the possible variations in gender, age, body mass index (BMI), hypertension and diabetes mellitus in the studied groups.

CONCLUSION

Presence of VLP is comparable among CSX and CAD patients.

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.

Optimal weighted averaging of event related activity from acquisitions with artifacts

In several biomedical applications that require the signal processing of biological data, the starting procedure for noise reduction is the ensemble averaging of multiple repeated acquisitions (trials). This method is based on the assumption that each trial is composed of two additive components: (i) a time-locked activity related to some sensitive/stimulation phenomenon (ERA, Event Related Activity in the following) and (ii) a sum of several other non time-locked background activities. The averaging aims at estimating the ERA activity under very low Signal to Noise and Interference Ratio (SNIR). Although averaging is a well established tool, its performance can be improved in the presence of high-power disturbances (artifacts) by a trials classification and removal stage. In this paper we propose, model and evaluate a new approach that avoids trials removal, managing trials classified as artifact-free and artifact-prone with two different weights. Based on the model, a weights tuning is possible and through modeling and simulations we show that, when optimally configured, the proposed solution outperforms classical approaches.

A novel low-complexity post-processing algorithm for precise QRS localization

Precise localization of QRS complexes is an essential step in the analysis of small transient changes in instant heart rate and before signal averaging in QRS morphological analysis. Most localization algorithms reported in literature are either not robust to artifacts, depend on the sampling rate of the ECG recordings or are too computationally expensive for real-time applications, especially in low-power embedded devices. This paper proposes a localization algorithm based on the intersection of tangents fitted to the slopes of R waves detected by any QRS detector. Despite having a lower complexity, this algorithm achieves comparable trigger jitter to more complex localization methods without requiring the data to first be upsampled. It also achieves high localization precision regardless of which QRS detector is used as input. It is robust to clipping artifacts and to noise, achieving an average localization error below 2 ms and a trigger jitter below 1 ms on recordings where no additional artifacts were added, and below 8 ms for recordings where the signal was severely degraded. Finally, it increases the accuracy of template-based false positive rejection, allowing nearly all mock false positives added to a set of QRS detections to be removed at the cost of a very small decrease in sensitivity. The localization algorithm proposed is particularly well-suited for implementation in embedded, low-power devices for real-time applications.

A hybrid approach to the simultaneous eliminating of power-line interference and associated ringing artifacts in electrocardiograms

Background

The second-order, infinite impulse response notch filter is widely used to remove electrical power line noise in electrocardiograms (ECGs). However this filtering process often introduces spurious ringing artifacts in the vicinity of raw signal with sharp transitions. It is challenging to simultaneously remove these two types of noise without losing vital information about cardiac activities.

Objective

Our objective is to devise a method to remove the power-line interference without introducing artifacts nor losing vital information. To this end we have developed the "hybrid approach" involving two-sided filtration and multi-iterative approximation techniques. The two-sided filtration technique can suppress the interference but some cardiac components are lost. The lost information can be restored using multi-iterative approximation technique.

Results

For evaluation, four artificial data sets, each including 91 ECGs of different heart rates, were generated by a dynamical model. Four publicly-accessible sets of clinical data (MIT-BIH Arrhythmia, QT, PTB Diagnostic ECG, and T-Wave Alternans Challenge Databases) were also selected. Our new hybrid approach and the existing method were tested with these two types of signal under various pre-determined conditions. In contrast with the existing method, the hybrid approach can provide more than 27.40 dB and 37.77 dB reduction in signal distortion for 95% and 60% of artificial ECGs respectively; it can provide in excess of 11.78 dB and 17.48 dB reduction in distortion for 95% and 60% of these real records respectively.

Conclusions

Overall, a significant reduction in signal distortion is demonstrated. These test results indicate that the newly proposed approach outperforms the traditional method assessed on both the artificial and clinical ECGs and suggest it could be of practical use for clinicians in the future.

A method for ventricular late potentials detection using time-frequency representation and wavelet denoising

This study proposes a method for ventricular late potentials (VLPs) detection using time-frequency representation and wavelet denoising in high-resolution electrocardiography (HRECG). The analysis is performed both with the signal averaged electrocardiography (SAECG) and in real time. A comparison between the temporal and the time-frequency analysis is also reported. In the first analysis the standard parameters QRSd, LAS40, and RMS40 were used; in the second normalized energy in time-frequency domain was calculated. The algorithm was tested adding artificial VLPs to real ECGs.

[Diagnostic criteria for the Brugada syndrome: can they be improved?]

INTRODUCTION

Diagnosis of Brugada syndrome (BS) currently requires documentation of a characteristic repolarization pattern (type 1 Brugada ECG). Mutations in the SCN5A gene, which codes for sodium channel Na(v) 1.5, are found in 38% of familial cases of BS. Sodium current dysfunction negatively affects the cardiac fast response action potential, particularly in atrial and ventricular myocytes and in the fast-conducting Purkinje system.

OBJECTIVES

To detect carriers of SCN5A mutations without using the characteristic repolarization pattern (type 1 Brugada ECG).

METHODS

Of a total of 141 members of three different families including 55 carriers of two nonsense SCN5A mutations causing BS, all those aged over 16 (113 individuals, 42 carriers) were studied. The PR interval (PR) and QT dispersion (QTd) between leads V1 and V3 were measured on conventional ECG. Using signal-averaged ECG the total duration of the filtered QRS complex (fQRS), the root-mean-square (RMS40) and the low-amplitude signal (LAS) were measured. The following procedures were developed to detect carriers/To detect carriers the following procedures were developed: (1) a screening test (ScreenTest) with PS (PR+fQRS) > or = 250 (250ms is 80% of the theoretical maximum in healthy individuals); and (2) a diagnostic test (DiagTest) for the simultaneous fulfillment of four conditions: PS > or = 250 and QTd > or = 10 and LAS > 26 and RMS40 < or = 29 (the latter two cut-offs are approximately 70% of the theoretical maximum in healthy carriers).

RESULTS

Significant differences in PR, QTd, QRSf, RMS40 and LAS were found between carriers and non-carriers. The SCN5A gene was associated with all these variables, the strongest association being with PR. Both tests were applied to 63 family members (38 carriers). The ScreenTest was positive in 38 of 38 carriers, with eight false positives in 27 non-carriers (sensitivity [SE] = 100% and specificity [SP] = 66.67%). From ROC curve analysis a cut-off of PS = 252.5 shows SE = 100% and SP = 76% and a cut-off of PS = 260 shows SE=94.7% and SP = 84%. The DiagTest was positive in 36 of 38 carriers, with three false positives: SE = 94.74% and SP = 88.89%. From ROC curve analysis a multivariate logistic model identifies a cut-off with SE = 92% and SP = 92%. In the same group the SE and SP of the characteristic spontaneous repolarization pattern (type 1 Brugada ECG) to detect carriers were 52.4% and 97.2%, respectively, and the difference between the SE of the DiagTest and of the typical repolarization pattern is statistically significant.

CONCLUSIONS

The ScreenTest and DiagTest are more effective tools than the characteristic repolarization pattern to discriminate between carriers and non-carriers of these two nonsense SCN5A mutations. We suggest their use in first-degree relatives of Brugada patients when the results of genetic testing are not available, in a score of disease probability in individuals with idiopathic Brugada ECG, and in patients with arrhythmias or other Brugada-related symptoms presenting type 2 or type 3 Brugada ECG.

Use of electrocardiographic depolarization abnormalities for detection of stress-induced ischemia as defined by myocardial perfusion imaging

High-frequency mid-QRS (HFQRS) analysis was recently introduced as a tool for identification of stress-induced ischemia. The diagnostic performance of this electrocardiographic technique has not been determined in a large cohort of patients. This study compared the diagnostic performance of HFQRS analysis to conventional ST-segment analysis in detecting exercise-induced ischemia. The study included 996 patients (56 ± 10 years of age, 670 men) referred for exercise myocardial perfusion imaging (MPI), which served as the gold standard of ischemia. High-resolution electrocardiogram was used for computer analysis of HFQRS signals. Number of electrocardiographic leads with ≥50% decrease of HFQRS intensity (L(50%)) was used as an index of ischemia. Perfusion images were evaluated semiquantitatively. Receiver operating characteristic analysis demonstrated an L(50%) ≥3 as the criterion that yielded optimal sensitivity and specificity for diagnosing moderate/severe ischemia. Compared to ST-segment analysis HFQRS analysis was more sensitive (69% vs 39%, p <0.005) and more specific (86% vs 82%, p <0.05). L(50%) correlated with amount of MPI ischemia (R(2) = 0.75, p <0.0001). Multivariate logistic regression analysis demonstrated a significant incremental diagnostic value for the addition of HFQRS data to a model containing pretest and conventional exercise parameters. L(50%) was the best predictor of mild or moderate/severe MPI ischemia. In conclusion, computerized HFQRS analysis improved the diagnostic performance of conventional stress electrocardiogram in detecting exercise-induced ischemia. Thus, this technique might aid in the noninvasive evaluation of coronary artery disease.

The prevalence and the prognostic value of microvolt T-wave alternans in patients with hypertrophic cardiomyopathy

BACKGROUND

Nonsustained ventricular tachycardia (nVT) may have ominous implications for patients with hypertrophic cardiomyopathy (HCM). The microvolt T-wave alternans (TWA) has been proposed as a noninvasive tool-identifying patients at risk of sudden cardiac death and ventricular tachycardia/fibrillation (VT/VF). The aim of the study was to determine the significance of TWA in predicting nVT episodes and compare how other electrocardiographic parameters can predict the occurrence of nVT.

METHODS

The study group consisted of 88 patients with HCM. TWA was assessed during exercise test using the CH2000 system. All patients underwent Holter monitoring (HM) within 2-4 weeks before TWA test (preexercise HM1) and immediately after (postexercise HM2). During HM, we analyzed: arrhythmias, QT intervals, the presence of late ventricular potentials (LP), heart rate variability, heart rate turbulence.

RESULTS

Depending on TWA results, the patients were divided into two groups: TWA+; 46 patients (52.3%) with positive/indeterminate results, and TWA-; 42 patients (47.7%) with negative results. The nVT episodes were more frequent among TWA(+) both in HM1 and HM2. The presence of TWA increases the risk of postexercise nVT over twenty times (OR = 21.03). Moreover, in HM1, QTc and LP, and in HM2, again QTc and N-terminal precursor of brain natriuretic peptide proved to be significant predictors of nVT. The addition of TWA to the models did not improve the arrhythmia risk assessment.

CONCLUSIONS

Repolarization abnormality plays an important role in generating nVT in patients with HCM, but TWA does not specifically predict the risk of arrhythmic end point.

Evidence of altered cardiac electrophysiology following prolonged androgenic anabolic steroid use

The non-therapeutic use of androgenic anabolic steroids (AAS) is associated with sudden cardiac death. Despite this, there is no proposed mechanism by which this may occur. Signal-averaged ECG (SAECG) allows the assessment of cardiac electrical stability, reductions of which are a known risk factor for cardiac arrhythmias. The aim of the present study was to examine cardiac electrical stability using SAECG in a group (n = 15) of long-term AAS users (AAS use 21.3 ± 3.1 years) compared with a group (n = 15) of age-matched weight lifters (WL) and age-matched sedentary controls [C (n = 15)]. AS, WL and C underwent SAECG analysis at rest and following an acute bout of exercise to volitional exhaustion. SAECGs were analyzed using a 40 Hz filter and were averaged over 200 beats. Results indicate a non-significant trend for increased incidence of abnormal SAECG measures at rest in AS (P = 0.55). However, AS demonstrated a significantly higher incidence of abnormalities of SAECG following exercise than C or WL (P < 0.05). In conclusion, the higher incidence of abnormal SAECG measurements immediately post-exercise in the AAS group places them at a greater risk of sudden death. The present study provides a strong contraindication to the use of AAS.

Analysis of unpredictable components within QRS complex using a finite-impulse-response prediction model for the diagnosis of patients with ventricular tachycardia

This study proposes a finite-impulse-response (FIR) prediction model to analyze the unpredictable intra-QRS potentials (UIQP) for identifying ventricular tachycardia patients with high-risk ventricular arrhythmias. The simulation study shows that a QRS complex including abnormal intra-QRS potentials (AIQP) has a higher UIQP and UIQP-to-QRS ratio in comparison with one without AIQP. The clinical results demonstrate that the mean UIQP-to-QRS ratios of VT patients in leads X, Y and Z were significantly larger than those of the normal subjects, and the linear and logical combination of UIQP-to-QRS ratios and ventricular late potential parameters can enhance diagnosis performance for VT patients.

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.

QRS prolongation on the signal-averaged electrocardiogram versus ST-segment changes on the 12-lead electrocardiogram: which is the most sensitive electrocardiographic marker of myocardial ischemia?

BACKGROUND

ST-segment changes and QRS prolongation are electrocardiographic (ECG) markers of myocardial ischemia.

HYPOTHESIS

This study was undertaken to investigate the appearance of QRS duration changes with or without concomitant ST-segment changes during a typical anginal episode.

METHODS

For this purpose, 126 patients underwent 12-lead surface ECG and signal-averaged electrocardiogram (SAECG) during typical anginal pain as well as at the time the patient was asymptomatic. In both periods, QRS duration and ST-segment changes were evaluated. All patients underwent cardiac catheterization.

RESULTS

Of the 126 patients, 108 (86%) had coronary artery disease (CAD), whereas the remaining 18 (14%) patients had normal coronary arteriograms. During typical anginal pain, 75 of the 108 (70%) patients with CAD and 2 of the 18 (11%) patients with normal coronary arteriograms developed QRS prolongation, whereas 60 of the 108 (56%) patients with CAD and 2 of the 18 (11%) patients with normal coronary vessels developed ST-segment changes. Thus, the sensitivities of QRS prolongation measured by SAECG and of ST-segment changes on the surface ECG for the detection of myocardial ischemia were found to be 70 and 56%, respectively, (p < 0.01), whereas the specificities were both found to be 89% (p = NS).

CONCLUSIONS

During typical anginal pain, QRS prolongation on the SAECG is more sensitive than are ST-segment changes on the ECG for the detection of myocardial ischemia.

Arrhythmogenic right ventricular cardiomyopathy type 5 is a fully penetrant, lethal arrhythmic disorder caused by a missense mutation in the TMEM43 gene

Autosomal-dominant arrhythmogenic right ventricular cardiomyopathy/dysplasia (ARVC/D) causes sudden cardiac death and is characterized by clinical and genetic heterogeneity. Fifteen unrelated ARVC families with a disease-associated haplotype on chromosome 3p (ARVD5) were ascertained from a genetically isolated population. Identification of key recombination events reduced the disease region to a 2.36 Mb interval containing 20 annotated genes. Bidirectional resequencing showed one rare variant in transmembrane protein 43 (TMEM43 1073C-->T, S358L), was carried on all recombinant ARVD5 ancestral haplotypes from affected subjects and not found in population controls. The mutation occurs in a highly conserved transmembrane domain of TMEM43 and is predicted to be deleterious. Clinical outcomes in 257 affected and 151 unaffected subjects were compared, and penetrance was determined. We concluded that ARVC at locus ARVD5 is a lethal, fully penetrant, sex-influenced morbid disorder. Median life expectancy was 41 years in affected males compared to 71 years in affected females (relative risk 6.8, 95% CI 1.3-10.9). Heart failure was a late manifestation in survivors. Although little is known about the function of the TMEM43 gene, it contains a response element for PPAR gamma (an adipogenic transcription factor), which may explain the fibrofatty replacement of the myocardium, a characteristic pathological finding in ARVC.

Signal-averaged electrocardiogram may be a beneficial prognostic procedure in the postoperative follow-up tetralogy of fallot patients to determine the risk of ventricular arrhythmias

Early detection of arrhythmias after congenital heart disease surgery is important because it can help decrease morbidity and mortality. Standard electrocardiograms (ECGs) contain frequencies between 0.05 and 100 Hz, but higher frequencies are also present. Using high-resolution technology, the highest amplitudes of these high-frequency components within the QRS complex can be recorded and analyzed. We studied the relationship between ventricular late potentials, ventricular arrhythmias and right ventricular systolic pressure in 22 patients who underwent tetralogy of Fallot repair (mean follow-up, 40.1 +/- 33.5 months). Holter ECG monitoring and signal-averaged electrocardiograms (SAECGs) were performed. SAECG parameters studied included the duration of the filtered QRS, the duration of terminal QRS below 40 muV, and the root mean square amplitude of the terminal 40 msec. Cardiac catheterization was performed on 19 patients. Eighteen healthy volunteers were studied as a control. Ventricular arrhythmias were found in 13 patients; right ventricular systolic hypertension was found in 1 patient. No significant residual ventricular septal defects were detected. Eight patients had ventricular late potentials. Right ventricular systolic pressure did not differ significantly between patients with or without late potentials. There were significant differences between patients with ventricular arrhythmias and healthy volunteers; filtered QRS duration was significantly longer in patients with ventricular arrhythmias. SAECG may be beneficial in determining ventricular arrhythmia risk in tetralogy of Fallot patients postoperatively.