Low Amplitude Signal Duration Research Articles

Correlation between epsilon wave and late potentials in arrythmogenic right ventricular cardiomyopathy. Do late potentials define the epsilon wave?

Abstract 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 epsilon wave (EW) is still under discussion. Aim The aim of the study was to correlate the presence of EW with late ventricular potentials (LPs) in ARVC patients (pts). The correlation between RV dilatation /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, ECHO were performed in all pts. The presence of EW, defined as low-amplitude deflection observed between the end of the QRS complex and the onset of the T wave was analysed in ECG by 3 investigators. LPs were defined as low-amplitude, high-frequency waveforms at the end of the QRS complex on signal-averaged ECG (SAECG). SAECG was considered positive for LPs when at least two of the three following criteria were met: filtered QRS duration (fQRS) >114 ms, root-mean-square voltage in the terminal 40 ms (RMS 40) <20 uV, or low amplitude (<40 µV) signal (LAS 40) duration >38 ms. The results were compared with a reference group consisting of 53 pts with RV damage in the course of atrial septum defect (ASD) (29 pts, 8 men, aged 22-80 years) or Ebstein Anomaly (EA) (24 pts, 11 men, aged 23-55 years). 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 LP+ than in LP- patients (48.1% vs 6.9%, p<0001; OR 12.5). In ARVC a relationship was also found between the presence of LPs and increased RV inflow tract (RVIT) and RV outflow tract (RVOT) dimensions, as well as a reduced RV S' wave value. RVOT >36 mm, RVIT >41 mm and RV S’ <9 cm/s were observed significantly more often in the LPs+ than in LPs- group (OR: 8.3, 6.4 and 3.6, respectively). In the ARVC group, any of fQRS >114 ms, LAS >38 ms, and RMS <20 uV were significantly more frequent in EW+ pts. In multivariate analysis, the only independent factor of the EW was fQRS (OR: 1.043 [1.020-1.067], p<0.001; AUC: 0.852). 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, possibly due to a lower degree of fibrosis in ASD/EA compared to ARVC.

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.

PO-02-228 ASSOCIATION BETWEEN SIGNAL-AVERAGED ECG INDICES AND RV STRUCTURAL ABNORMALITIES IN PATIENTS WITH ARRHYTHMOGENIC RIGHT VENTRICULAR CARDIOMYOPATHY: INSIGHTS FROM NORDIC ARVC REGISTER

The value of signal-averaged ECG (SAECG) derived ventricular late potentials (LP) as a minor depolarization criterion of arrhythmogenic right ventricular cardiomyopathy (ARVC) has been debated. Another criterion from the same category, terminal activation duration (TAD>55 ms), is obtained from standard V1 ECG lead, which makes it easier for use. However little data exist regarding the relationship between structural right ventricular (RV) ARVC substrate, LP and TAD. We aimed to explore the association between structural and functional RV abnormalities assessed using cardiac magnetic resonance (CMR), SAECG parameters, and abnormal TAD. Patients with definite ARVC diagnosis or genotype-positive family members who were recruited in the Nordic ARVC Registry with SAECG and CMR were included (n=268, mean age 42±16 years, female 46%, probands 49%). RV end-diastolic volume index (RVEDVI), RV ejection fraction (RVEF), and late gadolinium enhancement (LGE) presence were assessed. RV was defined as enlarged if RVEDVI > 100 ml/m2 for men and 90 ml/m2 for women. RVEF was considered reduced if lower than 45%. SAECG components were assessed using TFC2010 definitions: filtered QRS duration (fQRSd)>114 ms, duration of terminal low-amplitude QRS signal below 40 μV (LAS40)> 38 ms and root-mean-square voltage of the terminal 40 ms (RMS40)< 20 μV. An abnormal value of any one or more of these indexes was considered as the presence of LP. We assessed sensitivity and specificity of the SAECG indexes and TAD for association with abnormal RVEF, LGE and/or RVEDVI. C-statistics was used to assess the association between each of SAECG parameters as continuous variables and RV abnormalities. All 3 SAECG indexes were significantly associated with RV structural abnormalities using c-statistics (Table), each of them characterized by higher specificity and lower sensitivity than LP. TAD demonstrated high specificity but poor sensitivity in prediction of RV structural abnormalities. LP had lower specificity, but much higher sensitivity for association with RV structural and functional abnormalities than TAD. In a large cohort of patients with definite ARVC or genotype-positive family members SAECG indexes appear to have lower specificity for detection of structural and functional RV abnormalities compared to TAD, however its sensitivity far exceeds the one of the TAD and supports SAECG value as an ECG indicator of RV substrate.

Incremental value of the signal-averaged ECG for diagnosing arrhythmogenic cardiomyopathy

Arrhythmogenic right ventricular cardiomyopathy (ARVC) is currently diagnosed using a combination of clinical features, imaging, electrocardiography, and genetic investigations. An abnormal signal-averaged electrocardiogram (SAECG) is defined as a minor diagnostic criterion by the 2010 Task Force Criteria, but doubts remain about the value of this investigation. We evaluated the utility of the SAECG in diagnosing ARVC using the Canadian Arrhythmogenic Right Ventricular Cardiomyopathy Registry, a population representative registry of probands with ARVC and relatives, less influenced by referral bias. Probands with ARVC and family members from the Canadian Arrhythmogenic Right Ventricular Cardiomyopathy Registry underwent phenotype review. SAECG parameters were compared individually and in combination between those with varying degrees of ARVC severity and healthy controls (family members of probands with ARVC and unexplained sudden death, free of evidence of cardiac disease). A total of 196 patients with ARVC and 205 controls were included (mean age 44 ± 15 years; 186 of 401 men [46%]). SAECG abnormalities were seen in 83 of 205 controls (40%), 33 of 68 patients with ARVC and mild disease (51%), and 31 of 42 with severe disease (74%). The SAECG associated strongly with imaging abnormalities (major: odds ratio 3.0, 95% confidence interval 1.3-6.9; minor: odds ratio 3.5, 95% confidence interval 0.7-16.5) but not with other aspects of phenotype. Patients carrying pathogenic variants but with minimal phenotype had similar SAECGs to healthy controls (filtered QRS duration 111.2 ± 11.2 ms vs 111 ± 7.6 ms, P = .93; duration of low amplitude signals < 40 μV 32.3 ± 8.9 ms vs 34.2 ± 7.2 ms, P= .32; root mean square of the terminal 40 ms of the filtered QRS complex 43.1 ± 25.2 ms vs 38.2 ± 20.2 ms, P = .38). The SAECG appears to be a surrogate marker for structural abnormalities seen on imaging in those with ARVC. Great caution is required in interpreting SAECG findings in those without other corroborating evidence of an ARVC phenotype.

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

Late potentials (LPs) identified on the signal averaged electrocardiogram (SAECG) are a marker for an increased risk of arrhythmias in Brugada syndrome (BrS). Procainamide is a sodium channel blocker used to diagnose BrS. The effects of Procainamide on the SAECG in those with BrS and the significance of Procainamide-induced LPs are unknown. Procainamide provocation was performed for suspected BrS with 12-lead and SAECG pre- and post-infusion. Filtered QRS duration (fQRSd), duration of low amplitude signals<40 μV (LAS40) and root-mean-square voltage in the terminal 40ms (RMS40) were determined. Data from 150 patients were included in the analysis (mean age 44.5 years, 109 males). Procainamide increased fQRSd (Pre 118.8±10.5ms, post 121.2±10.2ms, p<0.001) and LAS40 (Pre 38.7±9.8ms, post 40.2±10.5ms, p=0.005) and decreased RMS40 (Pre 24.6±12ms, post 22.8±12ms, p=0.002). LPs were present in 68/150 (45%) at baseline. Fifteen patients with negative baseline SAECGs had LPs unmasked by Procainamide, but six patients had LPs at baseline that were no longer present following Procainamide. Comparing those with normal hearts (n=48) to those with a final diagnosis of BrS (n=38), Procainamide prolonged fQRSd to a greater extent in those with BrS. Comparing those with Procainamide-induced LPs to those with no LPs at any time did not highlight any aspect of phenotype and did not correlate with a history of ventricular arrhythmias. Procainamide influences the SAECG, provoking LPs in a small proportion of patients. However, there is no evidence that Procainamide-induced LPs provide additional diagnostic information or aid risk stratification.

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

BackgroundEarly 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.MethodsThis 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.ResultsAfter 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.ConclusionHolter SAECG may be useful for detecting cardiac involvement in patients with pulmonary sarcoidosis.

P945What is the role of late-potentials determined by signal-averaged ECG in predicting flecainide provocative test in brugada pattern?

Abstract Introduction The sudden cardiac death risk in Brugada Syndrome (BrS) is higher in patients with spontaneous type 1 pattern. Brugada diagnosis is also established in patients with induced type 1 morphology after provocative test with intravenous administration with a sodium blocker channel. Nevertheless, this group of patients is known to be at a lower risk of SCD, and their risk stratification is still a matter of discussion. Late potentials (LP) detected on signal-averaged ECG (SAECG) on the RVOT have been previously proposed as a predictor factor for BrS, even though data is lacking on its value. Purpose To evaluate the association between positive LP (LMS40&amp;gt; 38ms) on SAECG with modified Brugada leads and a positive flecainide test in patients with non-type 1 BrS. Methods Retrospective single-center study of non-type 1 BrS patients referred for the performance of a flecainide provocative test. Patients presenting with spontaneous type 1 morphology were excluded from the study. Study of LP on SAECG with modified leads for Brugada were evaluated before administration of flecainide [2mg/kg (maximum150mg), for 10minutes] with determination of filtered QRS duration (fQRS), root mean square voltage of the last 40ms of the QRS complex (RMS40) and duration of low amplitude signals &amp;lt;40μV of the terminal QRS complex (LMS40). Results 126 patients (47.3 ± 14.1 years, 61.9% males) underwent study with LP SAECG and flecainide test. Among these patients, 7.9% were symptomatic and 16.7% had familiar history of BrS. Flecainide test was positive in 46.8% of patients. In patients with a positive flecainide test, 64.4% presented LMS40 &amp;gt; 38ms whereas LMS40 &amp;gt; 38ms was present in only 46% of those with a negative flecainide test (p = 0.031). The presence of positive LMS40 was a positive predictor for a positive flecainide test, associated with a two-fold increase likelihood in the induction of a Brugada pattern (OR: 2,12; IC95% 1,025-4,392; P = 0,043). There was no association between fQRS or RMS40 and a positive flecainide test (p = NS). fQRS &amp;gt; 114ms and RMS40 &amp;lt;20uV was present in 22% and 61% of patients with a positive flecainide test, respectively. Conclusion In patient with non-type 1 Brugada syndrome, LMS40 &amp;gt; 38ms in SAECG was a predictor for a positive flecainide test, suggesting that this finding could be helpful on the risk stratification of patients undergoing diagnostic study for Brugada syndrome. Abstract Figure. Effect of LMS 40 in flecainide test

Identification of malignant early repolarization pattern by late QRS activity in high‐resolution magnetocardiography

BackgroundThe early repolarization pattern (ERP) in electrocardiography (ECG) has been considered as a risk for ventricular fibrillation (VF), but effective methods for identification of malignant ERP are still required. We investigated whether high spatiotemporal resolution 64‐channel magnetocardiography (MCG) would enable distinction between benign and malignant ERPs.MethodsAmong all 2,636 subjects who received MCG in our facility, we identified 116 subjects (43 ± 18 years old, 54% male) with inferior and/or lateral ERP in ECG and without structural heart disease, including 13 survivors of VF (ERP‐VF(+)) and 103 with no history of VF (ERP‐VF(−)). We measured the following MCG parameters in a time‐domain waveform of relative current magnitude: (a) QRS duration (MCG‐QRSD), (b) root‐mean‐square of the last 40 ms (MCG‐RMS40), and (c) low amplitude (<10% of maximal) signal duration (MCG‐LAS).ResultsCompared to ERP‐VF(−), ERP‐VF(+) subjects presented a significantly longer MCG‐QRS (108 ± 24 vs. 91 ± 23 ms, p = .02) and lower MCG‐RMS40 (0.10 ± 0.08 vs. 0.25 ± 0.20, p = .01) but no difference in MCG‐LAS (38 ± 22 vs. 29 ± 23 ms, p = .17). MCG‐QRSD and MCG‐RMS40 showed significantly larger area under the ROC curve compared to J‐peak amplitude in ECG (0.72 and 0.71 vs. 0.50; p = .04 and 0.03). The sensitivity, specificity, and odds ratio for identifying VF(+) based on MCG‐QRSD ≥ 100 ms and MCG‐RMS40 ≤ 0.24 were 69%, 74%, and 6.33 (95% CI, 1.80–22.3), and 92%, 48%, and 10.9 (95% CI, 1.37–86.8), respectively.ConclusionMagnetocardiography is an effective tool to distinguish malignant and benign ERPs.

Ventricular late potentials and myocardial fibrosis in hypertrophic cardiomyopathy

AimsVentricular late potentials (VLPs) represent delayed conduction due in part to myocardial fibrosis. We sought to examine the relationship of signal-averaged electrocardiography findings with myocardial fibrosis as assessed by cardiac magnetic resonance (CMR) in patients with hypertrophic cardiomyopathy (HCM). MethodsThis study consisted of 41 HCM patients with sinus rhythm who had undergone risk assessment including CMR and signal-averaged electrocardiography such as VLPs, filtered QRS duration, low amplitude signal duration of the terminal filtered QRS below 40 μV (LAS), and root mean square voltage of the late 40 ms of the filtered QRS (RMS). The concordance rate between VLPs and myocardial fibrosis as assessed by CMR was examined. ResultsLate gadolinium enhancement (LGE) on CMR was detected in 13 patients, and VLPs were detected in 14. Filtered QRS duration, LAS, RMS, and VLPs were not associated with LGE. The results of LGE and VLPs were concordant in 26 patients, whereas 15 exhibited discordance. Patients with discordance had a higher maximum wall thickness (24.1 ± 4.0 mm versus 21.0 ± 5.9 mm, p < 0.05), higher LGE volume (2.3 ± 1.2 g/cm versus 0.0 ± 0.8 g/cm, p < 0.01), lower LGE volume/the total number of sites with LGE (1.5 ± 0.7 versus 3.1 ± 2.8, p < 0.01), and predominant LGE location of the interventricular septum and anterior wall (60% versus 8%, p < 0.01) than patients with concordance. ConclusionVLPs were not a reliable marker for the detection of myocardial fibrosis as assessed by LGE on CMR in our cohort of patients with HCM. Condensed abstractVentricular late potentials on signal-averaged electrocardiography represent delayed conduction due in part to myocardial fibrosis but were not an alternative to cardiac magnetic resonance for detecting myocardial fibrosis in patients with hypertrophic cardiomyopathy.

The Anatomical View on Mean QRS Axis

Ventricular late potentials (VLPs) represent delayed conduction due in part to myocardial fibrosis. We sought to examine the relationship of signal-averaged electrocardiography findings with myocardial fibrosis as assessed by cardiac magnetic resonance (CMR) in patients with hypertrophic cardiomyopathy (HCM).This study consisted of 41 HCM patients with sinus rhythm who had undergone risk assessment including CMR and signal-averaged electrocardiography such as VLPs, filtered QRS duration, low amplitude signal duration of the terminal filtered QRS below 40 μV (LAS), and root mean square voltage of the late 40 ms of the filtered QRS (RMS). The concordance rate between VLPs and myocardial fibrosis as assessed by CMR was examined.Late gadolinium enhancement (LGE) on CMR was detected in 13 patients, and VLPs were detected in 14. Filtered QRS duration, LAS, RMS, and VLPs were not associated with LGE. The results of LGE and VLPs were concordant in 26 patients, whereas 15 exhibited discordance. Patients with discordance had a higher maximum wall thickness (24.1 ± 4.0 mm versus 21.0 ± 5.9 mm, p < 0.05), higher LGE volume (2.3 ± 1.2 g/cm versus 0.0 ± 0.8 g/cm, p < 0.01), lower LGE volume/the total number of sites with LGE (1.5 ± 0.7 versus 3.1 ± 2.8, p < 0.01), and predominant LGE location of the interventricular septum and anterior wall (60% versus 8%, p < 0.01) than patients with concordance.VLPs were not a reliable marker for the detection of myocardial fibrosis as assessed by LGE on CMR in our cohort of patients with HCM.Ventricular late potentials on signal-averaged electrocardiography represent delayed conduction due in part to myocardial fibrosis but were not an alternative to cardiac magnetic resonance for detecting myocardial fibrosis in patients with hypertrophic cardiomyopathy.

Spatiotemporal Estimation of Activation Times in Cardiac Electrograms

Ventricular late potentials (VLPs) represent delayed conduction due in part to myocardial fibrosis. We sought to examine the relationship of signal-averaged electrocardiography findings with myocardial fibrosis as assessed by cardiac magnetic resonance (CMR) in patients with hypertrophic cardiomyopathy (HCM).This study consisted of 41 HCM patients with sinus rhythm who had undergone risk assessment including CMR and signal-averaged electrocardiography such as VLPs, filtered QRS duration, low amplitude signal duration of the terminal filtered QRS below 40 μV (LAS), and root mean square voltage of the late 40 ms of the filtered QRS (RMS). The concordance rate between VLPs and myocardial fibrosis as assessed by CMR was examined.Late gadolinium enhancement (LGE) on CMR was detected in 13 patients, and VLPs were detected in 14. Filtered QRS duration, LAS, RMS, and VLPs were not associated with LGE. The results of LGE and VLPs were concordant in 26 patients, whereas 15 exhibited discordance. Patients with discordance had a higher maximum wall thickness (24.1 ± 4.0 mm versus 21.0 ± 5.9 mm, p < 0.05), higher LGE volume (2.3 ± 1.2 g/cm versus 0.0 ± 0.8 g/cm, p < 0.01), lower LGE volume/the total number of sites with LGE (1.5 ± 0.7 versus 3.1 ± 2.8, p < 0.01), and predominant LGE location of the interventricular septum and anterior wall (60% versus 8%, p < 0.01) than patients with concordance.VLPs were not a reliable marker for the detection of myocardial fibrosis as assessed by LGE on CMR in our cohort of patients with HCM.Ventricular late potentials on signal-averaged electrocardiography represent delayed conduction due in part to myocardial fibrosis but were not an alternative to cardiac magnetic resonance for detecting myocardial fibrosis in patients with hypertrophic cardiomyopathy.

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

BackgroundA novel signal-averaged electrocardiogram (SAECG) device and a novel ambulatory SAECG device are clinically available, but reference values have not been established. This study aimed to validate the novel SAECG and the novel ambulatory-based SAECG devices by comparison with the conventional SAECG device. Methods and resultsHigh-resolution SAECGs were recorded consecutively in 83 healthy volunteers using the 3 devices. A novel ambulatory SAECG device was used as real-time recording within 15 min for validation study (15 min ambulatory-based SAECG). We examined the concordance of positive results (at least 2/3 abnormal SAECG parameters) and negative results (0 or 1/3 abnormal parameters), as well as the correlations between SAECG parameters (filtered QRS duration [fQRS]); duration of low-amplitude signals < 40 μV in the terminal filtered QRS complex [LAS40]; root mean square voltage of the terminal 40 ms of the filtered QRS complex [RMS40]).Qualitative analysis showed excellent concordance among the novel SAECG, the 15 min ambulatory-based SAECG, and the conventional SAECG methods (novel SAECG vs. conventional SAECG = 94%; 15 min ambulatory-based SAECG vs. conventional SAECG = 91.6%; p = 0.755), while quantitative analysis indicated strong correlations between the novel SAECG and the conventional SAECG values for fQRS, LAS40, and LnRMS40 (r = 0.838–0.805, p < 0.0001, respectively). Strong correlations were also seen between 15 min ambulatory-based SAECG and conventional SAECG values for fQRS, LAS40, and RMS40 (r = 0.943–0.888, p < 0.0001, respectively). However, Bland-Altman quantitative analysis showed better agreement in fQRS and LnRMS40 measured by the 15 min ambulatory-based SAECG and the conventional SAECG than those by the novel SAECG and the conventional SAECG (fQRS, Lin's rho_c = 0.923 vs. 0757; RMS40, Lin's rho_c = 0.932 vs. 0.818, respectively). ConclusionIn healthy subjects, the parameters of either the novel SAECG or the 15 min ambulatory-based SAECG and those of the conventional SAECG were strongly correlated. Relatively good agreements were observed among 3 SAECGs, especially better between the 15 min ambulatory-based SAECG and the conventional SAECG probably due to similar measurement system of 2 methods.

Relationship between echocardiographic right-ventricular dimensions and signal-averaged electrocardiogram abnormalities in endurance athletes.

Regular physical exercise results in physiological cardiovascular changes. Athletes may demonstrate electrocardiographic changes that can also be seen in certain cardiomyopathies such as arrhythmogenic right-ventricular cardiomyopathy (ARVC). The aim of this study was to assess the prevalence of one such electrocardiographic characteristic, the abnormal signal-averaged ECG (SAECG), and to assess the correlation between SAECG parameters and echocardiographic parameters in athletes participating in sporting disciplines with combined strength and endurance components. We evaluated 24 elite athletes and 27 amateur athletes participating in combined high dynamic and high static (HDHS) sports, using an ECG, SAECG, and a transthoracic echocardiogram. The SAECG was regarded as positive for late potentials if one out of three parameters was abnormal. Prolongation of the filtered QRS duration (fQRS) was present in all of the elite athletes, compared with 74.1% of the amateur athletes (P = 0.011). There was a low prevalence of abnormalities in the other two SAECG parameters [low-amplitude signal (LAS) duration and root-mean-square (RMS) voltage]. The percentage of elite athletes and amateur athletes with ≥2 abnormal SAECG parameters was 8.3 and 7.4% (P = 0.99), respectively. Most of the echocardiographic dimensions were significantly greater in the elite athlete group compared with the amateur athletes. There was a moderate positive correlation between the fQRS and right-ventricular dimensions. The majority of elite and amateur athletes participating in HDHS sports reveal a prolonged fQRS duration on the SAECG, and according to the 2010 Task Force criteria for the diagnosis of ARVC, these athletes therefore demonstrate late potentials. The extent of fQRS prolongation is positively correlated with RV dimensions. Therefore SAECG findings should be interpreted with caution in endurance athletes.

Time-domain signal-averaged electrocardiogram in healthy German Shepherd and Boxer dogs

Signal-averaged electrocardiogram (SAECG) identifies ventricular late potentials (LP), low-amplitude electrical signals that are markers of slow cardiac conduction in fibrous myocardium, consisting in a predictive factor for sudden death in dogs at risk of sustained ventricular tachycardia. The aim of this study was to establish reference values of SAECG for German Shepherd and Boxer dogs. SAECG was performed in 19 German Shepherd and 28 Boxer client-owned dogs, and parameters analyzed were QRSd (duration of filtered QRS), LAS&lt;40μV (duration of low-amplitude signals in terminal portion of filtered QRS) and RMS40 (root square of mean voltage over the last 40 milliseconds of filtered QRS), with two different filters (25-250 Hz and 40-250 Hz). Statistical analyses was achieved by T Student test (p&lt;0.05) to identify differences between the two groups and between the values obtained with the two filters. No statistical difference was found in SAECG variables between the two breeds with the two different filters (p&gt;0.05). Achieving normal values of SAECG in German Shepherd and Boxer dogs is important to further research late potentials in animals of these breeds with hereditary ventricular tachycardia or arrhythmogenic cardiomyopathy and identification of individuals at high risk of cardiac-related sudden death.

Efecto de la Reperfusión no Inmediata sobre los Potenciales Tardíos luego de Angioplastía de la Arteria Responsable del Infarto Oc1uída

Evidencias recientes sugieren que la reperfusión tardía de una arteria responsable del infarto (ARI) ocluída luego del infarto agudo del miocardio (IAM), puede reducir la frecuencia de eventos arrítmicos subsecuentes y muerte súbita. La reperfusión mecánica de una ARI ocluída, por medio de angioplastía coronaria transluminal percútanea (ACTP) de 48 horas a dos semanas después del IAM tiene una alta tasa de éxito y poca reestenosis sintomática. Se identificaron 20 pacientes (19 hombres y una mujer, con edades entre 32 y 77 años, con un primer IAM, electrocardiograma de alta resolución (ECG-AR) y una ARI ocluída). 14 pacientes presentaban potenciales tardíos (PT) positivos después del IAM. En 18 pacientes se realizó una ACTP exitosa de la arteria ocluida, de 6 a 32 días después del IAM. Se realizó ECG-AR de seguimiento de 1 a 8 días después. En el subgrupo de 12 pacientes con reperfusión exitosa y un ECG-AR anormal antes de la ACTP, 7 (58,3%) mostraron resolución de los PT en el seguimiento, la duración del QRS filtrado mostró una reducción significativa (112,1 ± 14,2 mseg a 96,7 ± 12,6 mseg, p=0,02), y hubó una tendencia a incrementar el voltaje y la duración de las señales de baja amplitud. En contraste 2 pacientes con PT positivos antes de la ACTP y reperfusión no exitosa, no presentaron cambios significativos en el ECG-AR. Por lo tanto, la reperfusión mecánica tardía del vaso responsable puede reducir la incidencia de anormalidades en ECG-AR en algunos pacientes con un primer IAM, queda por demostrar si esto mejoraría la supervivencia a largo plazo, por lo que deberá investigarse en un estudio más amplio.

Abstract 18904: Cardiac Arrhythmias During Long Duration Spaceflight

PURPOSE: Whether cardiac arrhythmias are increased during spaceflight has been a long standing question for the human space program. Few data are available from long duration flight. To evaluate the incidence of in-flight arrhythmias we studied 12 astronauts during 4-6 months on the International Space Station with high-fidelity Holter monitoring. We hypothesized that spaceflight does not increase the incidence of cardiac arrhythmias, and when arrhythmias are observed they represent a benign substrate. METHODS: Twelve astronauts (3 women) wore 48hr Holter monitors: two preflight; in-Flight Day (FD)-14, 30, 75, 135; 15 days prior to return; and immediately upon landing. Individuals recorded symptoms in a diary. Arrhythmia frequency was assessed blindly by an experienced electrophysiologist. RESULTS: Baseline data showed 125±359 (range 1-1262) supraventricular ectopic beats (SEB) per 48hr period, while in-flight recordings showed 320±1137 SEB (range 0-5405); ventricular ectopy (VEB) at baseline was 286±944 beats (range 0-3282) and 305±775 beats (range 0-3439) in-flight confirming the substantial inter-individual variability. SEB and VEB at baseline were 0.06±0.16% and 0.13 ± 0.42% of all beats respectively, while the 48hr Holter with the largest number of ectopic beats for each astronaut was 0.25±0.74% (p=0.284) and 0.24±0.51% (p=0.177) respectively, demonstrating no significant change in ambient ectopy. There were no sustained arrhythmias in flight; short runs of NSVT (all &lt;5 beats) were observed both pre and in-flight in some astronauts. Filtered QRS duration (baseline: 84.5±8.2; in-flight maximum: 90.5±12.1 msec, p&lt;0.001), and low amplitude signal duration (baseline: 23.2±6.4; in-flight maximum: 27.1±6.4 msec, p&lt;0.01) increased subtly, but remained within normal limits; root mean square voltage of the terminal 40 ms did not change (baseline: 62.5±34.3; in-flight maximum: 73.0±29.4 microV, p=0.19). T wave alternans was not present at any time. Analysis of QT variability and T wave morphology in the first 6 astronauts did not change. CONCLUSIONS: Baseline arrhythmias are quite variable between astronauts; data suggest that long duration spaceflight is not associated with changes in arrhythmia frequency or arrhythmic substrate.

Identification of High-Risk Brugada Syndrome Patients by Combined Analysis of Late Potential and T-Wave Amplitude Variability on Ambulatory Electrocardiograms

Risk stratification is important in the management of Brugada syndrome (BrS). Late potentials (LPs) and T-wave amplitude variability (TAV) in high-resolution ambulatory electrocardiography (ECG) were retrospectively investigated. One hundred and twenty-seven patients diagnosed with BrS on 12-lead ECG were classified into 3 groups: documented ventricular fibrillation (VF)/asystole (n=19), episodes of syncope alone (n=30), and asymptomatic (n=78). Healthy volunteers were enrolled as controls (n=25). In the BrS patients, LPs showed appreciable circadian periodicity; filtered QRS duration (fQRS) and duration of the terminal low-amplitude signal <40 μV (LAS40) increased, whereas root mean square voltage of the terminal 40 ms of the fQRS (RMS40) decreased at night compared with the day. TAV did not have such a circadian periodicity. LP-positive incidence (night-time) and peak TAV were as follows: VF/asystole>syncope/asymptomatic>control (P<0.001). VF/asystole was discriminated from control at a ratio of 81-84% by night-time LPs (fQRS >116 ms, LAS40 >35 ms, RMS40 <25 μV) or peak TAV (>54 μV); VF/asystole was discriminated from syncope/asymptomatic at a ratio of 60-69%, by night-time LPs (fQRS >122 ms, LAS40 >42 ms, RMS40 <18μV) or peak TAV (>58 μV). Combined analysis of LPs and peak TAV increased the discriminant ratio up to 93% and 77%, respectively. Analysis of both LPs and TAV (taking circadian periodicity into account) is useful in identification of high-risk BrS patients.

Comparison of Late Potentials for 24 Hours Between Brugada Syndrome and Arrhythmogenic Right Ventricular Cardiomyopathy Using a Novel Signal-Averaging System Based on Holter ECG

Late potentials (LP) detected with signal-averaged ECGs are known to be useful in identifying patients at risk of Brugada syndrome (BS) and arrhythmogenic right ventricular cardiomyopathy (ARVC). Because the pathophysiology is clearly different between these disorders, we clarified the LP characteristics of these disorders. This study included 15 BS and 12 ARVC patients and 20 healthy controls. All BS patients had characteristic ECG changes and symptomatic episodes. All ARVC patients had findings that were consistent with recent criteria. Three LP parameters (filtered QRS duration, root mean square voltage of the terminal 40 ms of the filtered QRS complex, and duration of low-amplitude signals [<40 µV] in the terminal, filtered QRS complex) were continuously measured for 24 hours using a novel Holter-based signal-averaged ECG system. The incidences of LP determination in BS (80%) and ARVC (91%) patients were higher than in healthy controls (5%; P<0.0001 in both) but did not differ between BS and ARVC patients. In BS patients, the dynamic changes of all LP parameters were observed, and they were pronounced at nighttime. On the contrary, these findings were not observed in ARVC patients. When the SD values of the 3 LP parameters (filtered QRS duration, root mean square voltage of the terminal 40 ms of the filtered QRS complex, and duration of low-amplitude signals [<40 µV] in the terminal, filtered QRS complex) over 24 hours were compared for the 2 patient groups, those values in BS patients were significantly greater than those in ARVC patients (P<0.0001 in all). LP characteristics detected by the Holter-based signal-averaged ECG system over 24 hours differ between BS and ARVC patients. Dynamic daily variations of LPs were seen only in BS patients. This may imply that mechanisms of lethal ventricular arrhythmia in BS may be more correlated with autonomic abnormality than that of ARVC.

Correlation Between Signal-Averaged ECG and the Histologic Evaluation of the Myocardial Substrate in Right Ventricular Outflow Tract Arrhythmias

The differential diagnosis between idiopathic and cardiomyopathy-related right ventricular outflow tract (RVOT) ventricular arrhythmias (VAs) is crucial. Signal-averaged ECG (SAECG) abnormalities are frequent in cardiomyopathy-related RVOT-VAs, although their pathophysiologic basis and diagnostic value in this setting are undefined. We tested the association between SAECG and the myocardial substrate underlying RVOT-VAs. Twenty-four consecutive patients (median age, 50 years [42-59]; 12 men) with RVOT-VAs (10 with frequent [>1000/24 hours] premature ventricular contractions, 14 with ventricular tachycardias) underwent SAECG with 40-Hz filtering and electroanatomic mapping (EAM) with EAM-guided biopsy for characterization of the RVOT-VAs substrate. A filtered averaged QRS (fQRS) was obtained and analyzed for fQRS duration, low amplitude signal duration<40 mV (LAS40), and root-mean-square voltage in the last 40 ms of the QRS (RMS40). Standard definition of EAM scar was used. EAM-guided biopsy diagnosed ARVC in 11 (46%), myocarditis in 8 (33%), and idiopathic RVOT-VAs in 5 (21%) patients. Patients with cardiomyopathy-related RVOT-VAs had ≥1 EAM scar (median, 2 [1-2]; all with RVOT scar). EAM of patients with idiopathic RVOT-VAs was normal. Patients with cardiomyopathy-related RVOT-VAs had significantly longer fQRS (106 ms [92-132] versus 83 ms [82-84], P=0.01) and LAS40 (39 ms [36-51] versus 19 ms [18-21], P=0.02), and lower RMS40 (18 µV [9-26] versus 33 µV [32-33], P=0.04). A significant linear correlation was found between the extension (cm2) of the RVOT scar and all 3 SAECG parameters (rs=0.76, P<0.001 for the fQRSd; rs=0.73, P<0.001 for the LAS40; and rs=-0.72, P<0.001 for the RMS40). Using the established 2 of 3 criteria (ie, late potentials), SAECG diagnosed cardiomyopathy-related RVOT-VAs with high positive (100%) but low negative (38%) predictive values and missed 7 of 9 (78%) patients with RVOT scar<8 cm2. In patients with RVOT-VAs, abnormal SAECG parameters reflect the presence of extensive cardiomyopathic involvement of the RVOT. However, a negative SAECG does not reliably rule out cardiomyopathy-related RVOT-VAs in the presence of a small RVOT scar.

HLA-B27 and an Electrocardiographic Peculiarity

Introduction: An increased cardiovascular mortality has been described in patients with spondyloarthropathies due to HLA-B27. Numerous cardiovascular afflictions are currently known to be associated with HLA-B27. These include aortic root dilation, aortic regurgitation, mitral regurgitation, myocarditis, heart failure, pericarditis, pericardial effusion, atrioventricular conduction block and more recently, the presence of J-waves. Materials and methods: 48 HLA-B27 positive patients (23 men and 25 women) were included in this observational study. A 12-lead electrocardiogram and a signal-averaged electrocardiogram was recorded in every patient in order to detect any possible J-waves and ventricular late potentials respectively. Results: 27 out of these 48 patients demonstrated a visible J-wave in the inferolateral leads. It was revealed that there is a likelihood ratio of 11.386 (p=0.00074) to demonstrate a visible J-wave if the duration of low-amplitude signals is less than 30 ms. Conclusion: HLA-B27 positive patients has a high incidence of inferolateral cardiac J-waves. There is a high probability of demonstrating such a J-wave on the 12-lead electrocardiogram if the duration of ventricular late potentials is less than 30 ms. The possible mechanisms of this electrocardiographic paradox is discussed.