Orthogonal Electrocardiogram Research Articles

Beat to beat P wavelet analysis in addition to standard P wave indices as correlates of left atrial extent of low voltage areas in patients with PAF undergoing catheter ablation

Abstract Funding Acknowledgements Type of funding sources: None. BACKROUND Left atrium (LA) fibrosis has been shown to be an important factor associated with atrial fibrillation recurrence after catheter ablation (CA). Morphological features of the P wave have been related to the extent of atrial fibrosis as identified with electroanatomic mapping (EAM) in patients with paroxysmal atrial fibrillation (PAF) undergoing catheter ablation (CA). The ability to assess, by means of non-invasive markers, the electroanatomical substrate of the LA and the likelihood of PAF recurrence after CA, could be very useful in PAF management, patient selection for CA and improving outcomes. Purpose In the current prospective cohort study we aimed at establishing a pathophysiological basis of beat-to-beat (B2B) P-wave morphological and wavelet analysis, showing that it is associated with areas of considerable fibrosis, as identified with EAM in patients with PAF. Methods 44 patients with symptomatic paroxysmal AF, diagnosed at least 6 months before, were enrolled. 12-lead electrocardiogram (ECG) recordings, as well as 12 min vectorcardiogram (VCG) recordings were obtained from all patients, while EAM of left atrium (LA) was performed in all patients before radiofrequency CA. B2B P-wave morphological and wavelet analysis was performed according to a methodology described in previous publications. Results The 35 patients who were valid for statistical analysis were divided into 2 groups: in Group A the total low-voltage (<0.5 mV in EAM) area was greater than the median value of 5.55% (large low-voltage area), while in Group B the total low-voltage area was <5.55% (small low-voltage area). From the correlation between standard P-wave indices derived from 12-lead ECG and low-voltage areas only P-wave duration was significantly different between the two groups. From orthogonal ECG parameters analysis X axis was the most representative of low-voltage areas. B2B P-wave analysis revealed 3 features which showed a statistically significant difference between the 2 groups and no collinearity (Table 1). Logistic regression analysis of the non correlated variables for the prediction of low-voltage areas is shown in Table 2. It seems that a longer distance between the P-wave peak and the P-wave end, as well as a more «flattened» P-wave (small area with long duration) is associated with larger low-voltage areas and consequently more extensive LA fibrosis. Conclusions In patients with PAF and no overt atrial myopathy, B2B wavelet analysis may be a useful non-invasive tool for the prediction of low-voltage areas, representing fibrosis in the LA. Further studies in larger cohorts of patients are needed in order to confirm these findings and enable the use of B2B wavelet analysis in clinical practice.

Beat-to-beat P-wave analysis outperforms conventional P-wave indices in identifying patients with a history of paroxysmal atrial fibrillation, during sinus rhythm

Abstract Introduction Atrial fibrillation (AF) is the most common arrhythmia and is associated with high risk of morbidity and mortality. In many patients, AF is of episodic character (paroxysmal AF – PAF), which makes the identification of these patients during sinus rhythm (SR) challenging. Purpose The aim of the present study is to compare the performance of beat-to-beat P-wave analysis with P-wave indices used as predictors of PAF, such as P-wave duration, area, voltage, axis, terminal force in V1, inter-atrial block or orthogonal type, in identifying patients with history of PAF during sinus rhythm. Methods Standard 12-lead ECG and 10-minute orthogonal ECG recordings were obtained from 40 consecutive patients with short history of PAF under no antiarrhythmic medication and 60 age- and sex- matched healthy controls. The P-waves on the 10-minute recordings were analyzed on a beat-to-beat basis and classified as belonging to a primary or secondary morphology according to previous study. Wavelet transform used to further analyze P-wave orthogonal signals of main morphology on a beat-to-beat basis. Results 38 out of 327 studied features were found to differ significantly among the two groups. These features were tested for their diagnostic ability and receiver operating characteristic curves were ploted. Only 3 of them performed adequetly, with an area under curve (AUC) above 0.65; Two of them came from morphology analysis (percentage of beats following main morphology in axis X and Y) and one from wavelet analysis (max energy in high frequency zone -Y axis). Among standard P-wave indices, P-wave area in lead II was the one with the highest AUC (0.64). Conclusion Novel indices derived from beat-to-beat analysis outperform stadard P-wave markers in identifying patients with PAF history during sinus rhythm. Funding Acknowledgement Type of funding sources: None. ROC curves of most significant featuresAUC characteristics of P-wave indices

Detection of T Wave Peak for Serial Comparisons of JTp Interval.

Electrocardiogram (ECG) studies of drug-induced prolongation of the interval between the J point and the peak of the T wave (JTp interval) distinguished QT prolonging drugs that predominantly block the delayed potassium rectifier current from those affecting multiple cardiac repolarisation ion channel currents. Since the peak of the T wave depends on ECG lead, a “global” T peak requires to combine ECG leads into one-dimensional signal in which the T wave peak can be measured. This study aimed at finding the optimum one-dimensional representation of 12-lead ECGs for the most stable JTp measurements. Seven different one-dimensional representations were investigated including the vector magnitude of the orthogonal XYZ transformation, root mean square of all 12 ECG leads, and the vector magnitude of the 3 dominant orthogonal leads derived by singular value decomposition. All representations were applied to the median waveforms of 660,657 separate 10-s 12-lead ECGs taken from repeated day-time Holter recordings in 523 healthy subjects aged 33.5 ± 8.4 years (254 women). The JTp measurements were compared with the QT intervals and with the intervals between the J point and the median point of the area under the T wave one-dimensional representation (JT50 intervals) by means of calculating the residuals of the subject-specific curvilinear regression models relating the measured interval to the hysteresis-corrected RR interval of the underlying heart rate. The residuals of the regression models (equal to the intra-subject standard deviations of individually heart rate corrected intervals) expressed intra-subject stability of interval measurements. For both the JTp intervals and the JT50 intervals, the curvilinear regression residuals of measurements derived from the orthogonal XYZ representation were marginally but statistically significantly lower compared to the other representations. Using the XYZ representation, the residuals of the QT/RR, JTp/RR and JT50/RR regressions were 5.6 ± 1.1 ms, 7.2 ± 2.2 ms, and 4.9 ± 1.2 ms, respectively (all statistically significantly different; p < 0.0001). The study concludes that the orthogonal XYZ ECG representation might be proposed for future investigations of JTp and JT50 intervals. If the ability of classifying QT prolonging drugs is further confirmed for the JT50 interval, it might be appropriate to replace the JTp interval since with JT50 it appears more stable.

Polyscore of Non-invasive Cardiac Risk Factors.

Non-invasive risk stratification of cardiac patients has been the subject of numerous studies. Most of these investigations either researched unique risk predictors or compared the predictive power of different predictors. Fewer studies suggested a combination of a small number of non-invasive indices to increase the accuracy of high-risk group selection. To advance non-invasive risk assessment of cardiac patients, we propose a combination score (termed the Polyscore) of seven different cardiac risk stratifiers that predominantly quantify autonomic cardiovascular control and regulation, namely the slope of heart rate turbulence, deceleration capacity of heart rate, non-invasively assessed baroreflex sensitivity, resting respiration frequency, expiration triggered sinus arrhythmia, post-ectopic potentiation of systolic blood pressure, and frequency of supraventricular and ventricular ectopic beats. These risk stratification tests have previously been researched and their dichotomies defining abnormal results have been derived from previous reports. The Polyscore combination was defined as the number of positive tests among these seven risk predictors, giving a numerical scale which ranges from 0 (all tests normal) to 7 (all tests abnormal). The Polyscore was tested in a population of 941 contemporarily treated survivors of acute myocardial infarction (median age 61 years, 182 females) of whom 72 (7.65%) died during a 5-year follow-up. In these patients, all the risk predictors combined in the Polyscore were assessed during in-hospital 30-min simultaneous non-invasive recordings of high-frequency orthogonal electrocardiogram, continuous blood pressure and respiration. Compared to Polyscore 0 stratum, the hazard ratios of mortality during follow-up increased almost exponentially in strata 1 through 7 (vs. stratus 0, the hazard ratios were 1.37, 1.96, 7.03, 15.0, 35.7, 48.2, and 114, in strata 1 to 7, respectively; p < 0.0001). This allowed selecting low-risk (Polyscore ≤ 2), intermediate risk (Polyscore 3 or 4) and high-risk (Polyscore ≥ 5) sub-groups of the population that differed greatly in the Kaplan–Meier probabilities of mortality during follow-up. Since the Polyscore was derived from recordings of only 30-min duration, it can be reasonably applied in different clinical situations including population-wide screening. We can therefore conclude that the Polyscore is a reasonable method for cardiac risk stratification that is ready for prospective validation in future independent studies.

Global Electrical Heterogeneity: Mechanisms and Clinical Significance.

This review summarizes recent findings and discusses a clinical significance of a vectorcardiographic (VCG) Global electrical heterogeneity (GEH). GEH concept is based on the concept of the spatial ventricular gradient (SVG), which is a global measure of the dispersion of total recovery time. We quantify GEH by measuring five features of the SVG vector (SVG magnitude, direction (azimuth and elevation), a scalar value, and spatial QRS-T angle) on orthogonal XYZ ECG. In analysis of more than 20,000 adults we showed that GEH is independently associated with sudden cardiac death (SCD) after adjustment for demographics, cardiovascular disease (time-updated incident non-fatal cardiovascular events [coronary heart disease, heart failure, stroke, atrial fibrillation, use of beta-blockers], and known risk factors [cholesterol, triglycerides, physical activity index, smoking, diabetes, obesity, hypertension, anti-hypertensive medications, creatinine, alcohol intake, left ventricular ejection fraction, and time-updated ECG metrics (heart rate, QTc, QRS duration, ECG-left ventricular hypertrophy, bundle branch block or interventricular conduction delay)]. This finding suggests that GEH represents an independent electrophysiological substrate of SCD.

Abstract MP081: Short-long-short Sequence of RR Intervals is Associated With Increased Risk of Sudden Cardiac Death: the Atherosclerosis Risk in Community Study

Introduction: A Short-long-short sequence of RR’ intervals frequently precedes ventricular tachyarrhythmia. However, an association of RR’ alternans with sudden cardiac death (SCD) in the general population has not been previously studied. Hypothesis: We hypothesized that RR’ alternans is associated with SCD. Methods: We analyzed baseline visit 10-second ECG in 14,250 participants of the Atherosclerosis Risk in Communities (ARIC) cohort (mean age 54.1±5.87y; 45% men; 74% white). Only normal sinus beats were included in the semi-automated analysis. Digital 12-lead ECG was transformed into orthogonal ECG, from which respiratory signal was derived. Joint symbolic analysis was used to assess increase or decrease in successive RR’ intervals and R-instant respiratory phases calculated using the Hilbert transform. Short-long-short or long-short-long RR’ sequence was defined as RR’ alternans. RR’ alternans occurring during respiratory phase transitions were not considered. SCD, non-SCD, and non-cardiac death served as competing outcomes. Three competing risks models were constructed. Model 1 was adjusted for age, sex, race, and study center. Model 2 was in addition adjusted for prevalent CVD. Model 3 was further adjusted for subclinical CVD, its risk factors, including traditional ECG predictors, and medications affecting SA or AV nodes. Results: Over median follow-up of 24.4 years, there were 497 SCDs (incidence 1.66 [95%CI 1.52-1.82], 742 non-sudden cardiac deaths (incidence 2.48 [95%CI 2.31-2.67], and 3,753 non-cardiac deaths (incidence 12.6 [95%CI 12.1-13.0]) per 1,000 person-years. RR alternans was present in 1,679(11.8%) participants. In competing risks analysis (Table) the presence of RR’ alternans, excluding those occurring due to respiratory phase changes, was independently associated with increased risk of SCD. Conclusion: In competing risks analysis the presence of RR’ alternans that are not due to respiratory phase transition is associated with SCD. Further study of RR’ alternans is warranted.

Optimal configuration of adhesive ECG patches suitable for long-term monitoring of a vectorcardiogram

The purpose of this study was to develop optimal configuration of adhesive ECG patches placement on the torso, which would provide the best agreement with the Frank orthogonal ECGs. Ten seconds of orthogonal ECG followed by 3–5min of ECGs using patches at 5 different locations simultaneously on the torso were recorded in 50 participants at rest in sitting position. Median beat was generated for each ECG and 3 patch ECGs that best correlate with orthogonal ECGs were selected for each participant. For agreement analysis, spatial QRS-T angle, spatial QRS and T vector characteristics, spatial ventricular gradient, roundness, thickness and planarity of vectorcardiographic (VCG) loops were measured. Key VCG parameters showed high agreement in Bland–Altman analysis (spatial QRS-T angle on 3-patch ECG vs. Frank ECG bias 0.3 (95% limits of agreement [−6.23;5.71 degrees]), Lin's concordance coefficient=0.996). In conclusion, newly developed orthogonal 3-patch ECG can be used for long-term VCG monitoring.

Reproducibility of Heart Rate Variability Characteristics Measured on Random 10-second ECG using Joint Symbolic Dynamics.

In this paper we employed joint symbolic dynamics (JSD) approach to study reproducibility of heart rate variability characteristics measured on 2 randomly selected 10-second segments within 3-minute resting orthogonal ECG in 170 healthy participants. First, the ECG R-peaks were detected using parabolic fitting. Second, the respiratory signal was derived from orthogonal ECG X-lead using QRS slopes. Third, time series of R-R intervals and respiratory phases (calculated using Hilbert transform), were transformed into tertiary symbol vectors based on their successive changes and words of length '3' were formed. Bland-Altman analysis was used to assess the agreement between measured log-transformed JSD characteristics of HRV, and their reproducibility. Traditional HRV measures such as RR' interval changes showed a very high reproducibility. However, agreement between two 10-second JSD indices of HRV was low. Interestingly, a significant decrease in low-high alterations of HRV dynamics measured using JSD was observed when respiratory phase transition intervals were excluded (10s: 4.7±9.4 vs. 24.8±21.0%, p<0.0001; 3min: 9.8±8.1 vs. 24.8±12.3%, p<0.0001).

Comparison of reproducibility of conventional and signal-averaged electrocardiography

Objective. The aim of our study was to compare the reproducibility of signal-averaged and conventional electrocardiogram (ECG). Design and methods. The study group included 20 young healthy volunteers (10 men and 10 women, aged 18–25 years) examined twice with one-week interval. Twelve-lead and Frank’s orthogonal system ECG recordings were acquired during 5 minutes using computerized ECG device at each examination; conventional and averaged ECG analyses were performed. Mathematical processing to get averaged ECG in each lead was performed using original program «HR ECG». The sum of P wave, PQ interval, and QRS durations and the sum of P, Q, R, S, T waves amplitudes (amplitudes) in lead I of 12‑lead ECG and in lead Y in Frank’s lead system and left ventricular hypertrophy (LVH) indices (Sokolow-Lyon, Cornell voltage, Cornell product) were used for the evaluation of reproducibility. Results. Variation coefficients of durations between two evaluations of conventional and signal-averaged ECG were 13,1 % versus 4,8 % (p < 0,01) for lead I and 16 % versus 4,8 % (p < 0,01) for lead Y, respectively. Variation coefficients of amplitudes between two examinations of conventional and signal-averaged ECG were 12,2 % versus 7,2 % (p < 0,01) for lead I and 10,3 % versus 6,7 % for lead Y (p < 0,05), respectively. Variation coefficients of Sokolow-Lyon index, Cornell voltage and Cornell product were 12,3; 16,9 и 12,8 % versus 8,0; 14,2 и 10,1 %, respectively (p < 0,05 for all variables). Conclusions . The reproducibility of the signalaveraged ECG is significantly higher than the conventional one for interval duration, wave amplitude, as well as for LVH indices. The use of this method in clinical practice will increase the reliability of individual evaluation of myocardial changes at single examination and during follow-up. In studies with ECG control it may contribute to the decrease in study duration or group size required to reach statistically significant differences.

Assessment of the infarct size with ST-elevation from high-resolution standard and orthogonal ECG leads

The high-resolution electrocardiography is known to be a useful tool for extraction and analysis of low-amplitude signal components. We found the high-resolution standard and synthesized orthogonal electrocardiography leads may be useful for precise evaluation of the zone of acute myocardial infarct necrosis. We found high-resolution electrocardiography may be useful for precise location of the site of the myocardial necrosis and assessment of the severity of impaired left-ventricle systolic function of patients with ST-elevation myocardial infarct (STEMI) in the acute phase. High-resolution (1 MHz) ECG from 4 groups were collected: healthy controls (13), patients with anterior (10), inferior STEMI (19) and 12 patients with infero-lateral AMI). The three orthogonal leads X, Y, Z were synthesized from the 12-standard leads by known transformation. The possibility for facilitated and fast performance of this examination in clinical conditions, including emergency, the lack of necessity of specially trained staff for carrying out the examination and interpretation of the results, as well as the very low prime cost, make this electrophysiological method very suitable for application in the routine clinical practice for qualitative and quantitative assessment of patients with acute coronary syndromes.

Discrimination of different myocardial infarction stages using wide band electrocardiogram

Abstract Most of usual electrocardiogram (ECG) signals normally keep the signal energy in the 0.05–100 Hz band, but higher frequencies containing valuable diagnostic information are also present in wide band (WB) ECG signals. Existing studies on computer-assisted myocardial infarction (MI) diagnosis are mostly based on the usual ECG signals, and the valuable diagnostic information has not been used sufficiently yet. Multivariable autoregressive coefficients were extracted from WB orthogonal ECG (OECG) signals for the classification purpose in this research. The data for the analysis were taken from Physikalisch Technische Bundesanstalt diagnostic ECG database including health control, MI in early stage and MI in acute stage. In order to further investigate the performance of WB ECG signals, standard ECG signals with a wide frequency band were utilized for the feature extraction and classification as the same way. The experimental results showed that the MI classification accuracy could be improved by introducing WB ECG signals and the features extracted from WB OECG signals with a frequency of 0–250 Hz would be the best efficient representation for discriminating different MI stages. The classifiable and efficient features can be extracted from WB OECG signals for the classification of MI stages with a high accuracy.

Assessment of Joint Interactions between Respiration and Baroreflex Activity using Joint Symbolic Dynamics in Heart Failure Patients.

In this paper we employed a novel approach based on joint symbolic dynamics (JSD) to study interaction between respiratory phase and baroreflex activity. Electrocardiogram (ECG) and blood pressure recordings from six participants with history of heart failure were included in this study. First, the ECG R-peaks and systolic blood pressure indices were detected using parabolic fitting. Second, the respiratory signal was derived from Frank orthogonal ECG leads using QRS slopes and R-wave angles. Third, time series of R-R intervals and systolic blood pressure (SBP) were extracted, and respiratory phases were obtained using the Hilbert transform. Subsequently, each series was transformed into binary symbol vectors based on their successive changes and words of length '2' were formed. Baroreflex patterns were studied using word combinations representing baroreflex activity for specific changes in respiratory phases. Baroreflex activity was significantly higher for alternating low-high/high-low heart rate and SBP during inspiration as compared to continuous increase or decrease in heart rate and SBP ([Formula: see text], wRP=11: 39.1±9.3% vs. [Formula: see text], wRP=11: 6.4±3.9%, p<0.0001).

Repolarization lability measured on 10-second ECG by spatial TT′ angle: Reproducibility and agreement with QT variability

BackgroundReproducibility of spatial TT′ angle on the 10-second ECG and its agreement with QT variability has not been previously studied. MethodsWe analyzed 2 randomly selected 10-second segments within 3-minute resting orthogonal ECG in 172 healthy IDEAL study participants (age 38.1±15.2years, 50% male, 94% white). Repolarization lability was measured by the QT variance (QTV), short-term QT variability (STV(QT)), and spatial TT′ angle. Bland–Altman analysis was used to assess the agreement between different log-transformed metrics of repolarization lability, and to assess the reproducibility. ResultsThe heart rate showed a very high reproducibility (bias 0.14%, Lin's rho_c=0.99). As expected, noise suppression by averaging improves reproducibility. Agreement between two 10-second LogQTV was poor (bias −0.04; 95% limits of agreement [−1.89; 1.81]), while LogSTV(QT) (0.04 [−1.01; 1.10]), and especially LogTT′ angle (−0.009 [−0.84; 0.82]) was better. ConclusionTT′ angle is a satisfactory reproducible metric of repolarization lability on the 10-second ECG.

Heart rate variability as predictor of atrial fibrillation in middle-aged population

ventricular overload severity in patients with pulmonary arterial hypertension (PAH). Methods: We examined 120 PAH patients (23% males; age (mean ± SE) 39.5 ± 1.2 years). 120 healthy subjects (32% males; age 33.6 ± 0.9 years) comprised the control group. Systolic pulmonary artery pressure (SPAP) was calculated using Doppler echocardiography. Moderate PAH was defined as SPAP between 30–50 mm Hg; severe PAH as SPAP N50 mm Hg. Digital orthogonal electrocardiograms were recorded. We studied the magnitude G (in ms) and spatial components Gx, Gy, Gz of the “recovery acceleration” vector (directed to the left, inferior, and anterior). Results: In 30 patients with moderate PAH G, Gx and Gz were lower as compared with the normal group, and G, Gx and Gy were greater as compared with 90 patients with severe PAH. When used for discriminating between the moderate PAH and the normal group, Gz had an area under the ROC curve of 0.83, SE 0.05. The threshold Gz b10 ms provided 77% sensitivity and 83% specificity. For discriminating moderate and severe PAH, Gy had an area under the ROC curve of 0.87, SE 0.04. The threshold Gy b25 ms provided 82% sensitivity and 90% specificity. Gx and Gy had moderate correlation with SPAP (r = −0.5; p b 0.01). Conclusion: The use of decartographic parameters of repolarization may be helpful not only for detection of right ventricular overload in patients with PAH, but also for the assessment of its severity.

ECG marker of adverse electrical remodeling post-myocardial infarction predicts outcomes in MADIT II study.

BackgroundPost-myocardial infarction (MI) structural remodeling is characterized by left ventricular dilatation, fibrosis, and hypertrophy of the non-infarcted myocardium.ObjectiveThe goal of our study was to quantify post-MI electrical remodeling by measuring the sum absolute QRST integral (SAI QRST). We hypothesized that adverse electrical remodeling predicts outcomes in MADIT II study participants.MethodsBaseline orthogonal ECGs of 750 MADIT II study participants (448 [59.7%] ICD arm) were analyzed. SAI QRST was measured as the arithmetic sum of absolute QRST integrals over all three orthogonal ECG leads. The primary endpoint was defined as sudden cardiac death (SCD) or sustained ventricular tachycardia (VT)/ventricular fibrillation (VF) with appropriate ICD therapies. All-cause mortality served as a secondary endpoint.ResultsAdverse electrical remodeling in post-MI patients was characterized by wide QRS, increased magnitudes of spatial QRS and T vectors, J-point deviation, and QTc prolongation. In multivariable Cox regression analysis after adjustment for age, QRS duration, atrial fibrillation, New York Heart Association heart failure class and blood urea nitrogen, SAI QRST predicted SCD/VT/VF (HR 1.33 per 100 mV*ms (95%CI 1.11–1.59); P = 0.002), and all-cause death (HR 1.27 per 100 mV*ms (95%CI 1.03–1.55), P = 0.022) in both arms. No interaction with therapy arm and bundle branch block (BBB) status was found.ConclusionsIn MADIT II patients, increased SAI QRST is associated with increased risk of sustained VT/VF with appropriate ICD therapies and all-cause death in both ICD and in conventional medical therapy arms, and in patients with and without BBB. Further studies of SAI QRST are warranted.

Increased Variability of Tpeak-Tend Area Predicts Sudden Cardiac Death in Competing Risk Analysis in Heart Failure Patients with Ejection Fraction above and below 35%

Background Repolarization lability precedes ventricular arrhythmias. However, in recent competing risk analysis QT variability index predicted non–sudden cardiac death (SCD) but did not predict SCD. Predictive values of other repolarization lability parameters have not been studied in competing risk analysis. Methods We analyzed 3 minutes of baseline resting orthogonal ECGs in sinus rhythm in 533 participants of the observational cohort heart failure (HF) study (mean age 63.1 ± 11.7; males 70.6%; left ventricular ejection fraction [LVEF] >35% in 254 [48%]). Repolarization lability was measured as the root mean square successive difference (rMSSD) of the area under the curve from T-peak to T-end series (TpTe Area rMSSD). Holter monitoring was performed to identify patients who presented frequent (>240 in 24 hours) ventricular premature beats and also nonsustained ventricular tachycardia (NSVT). SCD and non-SCD served as primary endpoints. Results During median follow-up of 3.7 years of, 116 patients died, 52 from SCD and 53 from non-SCD. In multivariate competing risk analyses after adjustment for EF, New York Heart Association HF class, NSVT, and frequent premature ventricular complexes on 24-hours Holter ECG, the highest Tpeak-Tend Area rMSSD quartile was associated with SCD [subhazard ratio: 1.79 (95% CI 1.05–3.06), P = .034] but did not predict non-SCD [subhazard ratio: 0.95 (95% CI 0.53-1.72), P = .875; Figure 1). No interaction between Tpeak-Tend Area rMSSD and LVEF was found. Conclusions Increased repolarization lability measured as Tpeak-Tend area variability predicts SCD but not non-SCD in HF across the continuum of LV dysfunction.

Patients with hypertrophic cardiomyopathy at risk for paroxysmal atrial fibrillation: advanced echocardiographic evaluation of the left atrium combined with non-invasive P-wave analysis

The maintenance of sinus rhythm is crucial for the functional capacity of patients with hypertrophic cardiomyopathy (HCM). Using a multimodality approach, we attempted to identify potential predictors of paroxysmal atrial fibrillation (PAF) in HCM patients. Thirty HCM patients (17 males, mean age 57.9 ± 13.6) with at least one documented PAF episode and 32 age- and sex-matched HCM control patients as well as 25 healthy volunteers were studied in sinus rhythm. Study subjects underwent 2D echocardiography including a colour Doppler myocardial imaging evaluation of the left atrium (LA). Additionally, an orthogonal electrocardiogram was acquired; P-wave duration, maximum, and mean energies were calculated for each subject at each orthogonal lead and the composite vector axis using the Morlet wavelet analysis. Compared with HCM controls, in HCM-PAF patients, LA antero-posterior diameter was significantly enlarged (LADAP: 46.1 ± 5.9 vs. 40.0 ± 4.7 mm, P < 0.001), peak strain rate of the LA lateral wall in the reservoir phase was significantly decreased (LAT peak SR-S: 1.93 ± 0.51 vs. 2.55 ± 0.83 s(-1), P < 0.01), and P-wave duration in the Z-lead was significantly prolonged (P-durZ: 106.9 ± 24.6 vs. 86.2 ± 14.3 ms, P < 0.001). Cut-off values and areas under the curve (AUCs) for individual parameters were 42.0 mm, 2.32 s(-1), and 98.8 ms and 0.81, 0.74, and 0.78, respectively. A multivariable model combining LADAP, LAT peak SR-S and P-durZ had an AUC of 0.90, a sensitivity of 0.87, and a specificity of 0.91 for identifying PAF patients. P-wave duration combined with LA antero-posterior diameter and myocardial deformation indices resulted in a higher power for discriminating HCM-PAF patients, when compared with individual parameters derived from either wavelet analysis or 2D echocardiography.

Comparison of Standard versus Orthogonal ECG Leads for T‐Wave Alternans Identification

T-wave alternans (TWA), an electrophysiologic phenomenon associated with ventricular arrhythmias, is usually detected from selected ECG leads. TWA amplitude measured in the 12-standard and the 3-orthogonal (vectorcardiographic) leads were compared here to identify which lead system yields a more adequate detection of TWA as a noninvasive marker for cardiac vulnerability to ventricular arrhythmias. Our adaptive match filter (AMF) was applied to exercise ECG tracings from 58 patients with an implanted cardiac defibrillator, 29 of which had ventricular tachycardia or fibrillation during follow-up (cases), while the remaining 29 were used as controls. Two kinds of TWA indexes were considered, the single-lead indexes, defined as the mean TWA amplitude over each lead (MTWAA), and lead-system indexes, defined as the mean and the maximum MTWAA values over the standard leads and over the orthogonal leads. Significantly (P < 0.05) higher TWA in the cases versus controls was identified only occasionally by the single-lead indexes (odds ratio: 1.0-9.9, sensitivity: 24-76%, specificity: 76-86%), and consistently by the lead-system indexes (odds ratio: 4.5-8.3, sensitivity: 57-72%, specificity: 76%). The latter indexes also showed a significant correlation (0.65-0.83) between standard and orthogonal leads. Hence, when using the AMF, TWA should be detected in all leads of a system to compute the lead-system indexes, which provide a more reliable TWA identification than single-lead indexes, and a better discrimination of patients at increased risk of cardiac instability. The standard and the orthogonal leads can be considered equivalent for TWA identification, so that TWA analysis can be limited to one-lead system.

Abstract 9375: Sum Absolute QRST Integral Predicts Low Risk of Ventricular Tachyarrhythmias and Sudden Cardiac Death In MADIT II Study

Introduction. The need to extend risk stratification beyond use of ejection fraction is well recognized. New ECG risk marker, sum absolute QRST integral (SAI QRST) was recently proposed and was shown to be associated with low risk of sustained ventricular tachycardia (VT)/ventricular fibrillation (VF) in patients with structural heart disease and primary prevention implantable cardioverter-defibrillators (ICDs). The objective of this study was to validate predictive value of SAI QRST in analysis of landmark ICD trial MADIT II. Methods. Baseline orthogonal ECGs were recorded at rest during sinus rhythm in 750 MADIT II study participants and analyzed by customized Matlab software. Absolute QRST integral was measured as the arithmetic sum of areas under the QRST curve, averaged during a 5-minute epoch. Then the sum magnitude of three orthogonal leads absolute QRST integral (SAI QRST) was calculated. Primary end-point for analysis was sustained VT/VF with appropriate ICD therapies (shock or antitachycardia pacing), or sudden cardiac death. Results. During 3.5 years of follow-up, 143 patients experienced sustained VT/VF with appropriate ICD therapies, or died suddenly. In univariate analysis lowest quartile of SAI QRST (&lt; 116 mV*ms) was associated with decreased risk of sustained VT/VF with appropriate ICD therapies or sudden cardiac death (Figure 1). In multivariate analysis after adjustment for blood urea nitrogen and New York Heart Association functional class, low quartile SAI QRST was associated with decreased risk of VT/VF or sudden cardiac death as compared to three higher SAI QRST quartiles (Hazard Ratio 0.64 ; 95% CI 0.42 - 0.99 ; p=0.045). Conclusion . In post-myocardial infarction patients with depressed ejection fraction the lowest quartile of SAI QRST is associated with lower risk of sustained ventricular tachyarrhythmias and sudden cardiac death than it is observed in patients with higher SAI QRST values. Further study of SAI QRST is warranted.

A new electrocardiogram marker to identify patients at low risk for ventricular tachyarrhythmias: sum magnitude of the absolute QRST integral

We proposed and tested a novel electrocardiogram marker of risk of ventricular arrhythmias (VAs). Digital orthogonal electrocardiograms were recorded at rest before implantable cardioverter-defibrillator (ICD) implantation in 508 participants of a primary prevention ICDs prospective cohort study (mean ± SD age, 60 ± 12 years; 377 male [74%]). The sum magnitude of the absolute QRST integral in 3 orthogonal leads (SAI QRST) was calculated. A derivation cohort of 128 patients was used to define a cutoff; a validation cohort (n = 380) was used to test a predictive value. During a mean follow-up of 18 months, 58 patients received appropriate ICD therapies. The SAI QRST was lower in patients with VA (105.2 ± 60.1 vs 138.4 ± 85.7 mV ms, P = .002). In the Cox proportional hazards analysis, patients with SAI QRST not exceeding 145 mV ms had about 4-fold higher risk of VA (hazard ratio, 3.6; 95% confidence interval, 1.96-6.71; P < .0001) and a 6-fold higher risk of monomorphic ventricular tachycardia (hazard ratio, 6.58; 95% confidence interval, 1.46-29.69; P = .014), whereas prediction of polymorphic ventricular tachycardia or ventricular fibrillation did not reach statistical significance. High SAI QRST is associated with low risk of sustained VA in patients with structural heart disease.