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Aims: Ventricular activation patterns can aid clinical decision-making directly by providing spatial information on cardiac electrical activation or indirectly through derived clinical indices. The aim of this work was to derive an atlas of the major modes of variation of ventricular activation from model-predicted 3D bi-ventricular activation time distributions and to relate these modes to corresponding vectorcardiograms (VCGs). We investigated how the resulting dimensionality reduction can improve and accelerate the estimation of activation patterns from surface electrogram measurements.Methods and Results: Atlases of activation time (AT) and VCGs were derived using principal component analysis on a dataset of simulated electrophysiology simulations computed on eight patient-specific bi-ventricular geometries. The atlases provided significant dimensionality reduction, and the modes of variation in the two atlases described similar features. Utility of the atlases was assessed by resolving clinical waveforms against them and the VCG atlas was able to accurately reconstruct the patient VCGs with fewer than 10 modes. A sensitivity analysis between the two atlases was performed by calculating a compact Jacobian. Finally, VCGs generated by varying AT atlas modes were compared with clinical VCGs to estimate patient-specific activation maps, and the resulting errors between the clinical and atlas-based VCGs were less than those from more computationally expensive method.Conclusion: Atlases of activation and VCGs represent a new method of identifying and relating the features of these high-dimensional signals that capture the major sources of variation between patients and may aid in identifying novel clinical indices of arrhythmia risk or therapeutic outcome. [ABSTRACT FROM AUTHOR]

Aims: Left ventricular activation delay due to left bundle branch block (LBBB) is an important determinant of the severity of dyssynchronous heart failure (DHF). We investigated whether patient-specific computational models constructed from non-invasive measurements can provide measures of baseline dyssynchrony and its reduction after CRT that may explain the degree of long-term reverse ventricular remodelling.Methods and Results: LV end-systolic volume reduction (ΔESVLV) measured by 2D trans-thoracic echocardiography in eight patients following 6 months of CRT was significantly (P < 0.05) greater in responders (26 ± 20%, n = 4) than non-responders (11 ± 16%, n = 4). LV reverse remodelling did not correlate with baseline QRS duration or its change after biventricular pacing, but did correlate with baseline LV endocardial activation measured by electroanatomic mapping (R2 = 0.71, P < 0.01). Patient-specific models of LBBB ventricular activation with parameters obtained by matching model-computed vectorcardiograms (VCG) to those derived from standard patient ECGs yielded LV endocardial activation times that correlated well with those measured from endocardial maps (R2 = 0.90). Model-computed 3D LV activation times correlated strongly with the reduction in LVESV (R2 = 0.93, P < 0.001). Computed decreases due to simulated CRT in the time delay between LV septal and lateral activation correlated strongly with ΔESVLV (R2 = 0.92, P < 0.001). Models also suggested that optimizing VV delays may improve resynchronization by this measure of activation delay.Conclusions: Patient-specific computational models constructed from non-invasive measurements can compute estimates of LV dyssynchrony and their changes after CRT that may be as good as or better than electroanatomic mapping for predicting long-term reverse remodelling. [ABSTRACT FROM AUTHOR]

Aims Previous studies have reported right bundle branch block in Brugada syndrome. Subsequent analysis of electrocardiograms (ECGs) found one-third of cases classified as right bundle branch block did not meet criteria of a wide final S wave in the left leads. We aimed to study the role of the vectorcardiogram to characterize Brugada type 1 ECG pattern. Methods and results Compare Frank-method vectorcardiogram in 11 patients with Brugada type 1 ECG pattern (BrS group) with vectorcardiogram of 20 healthy individuals with ECGs depicting incomplete right bundle branch block (IRBBB group) and 12 patients with complete right bundle branch block (CRBBB group). Initial 10–20 ms vector of the QRS loop in the horizontal plane (HP): BrS and IRBBB groups: Vector heading anterior and leftward. CRBBB group: Vector directed anterior and rightward. Conclusions Vectorcardiograms in patients with Brugada type 1 ECG pattern have distinctive characteristics compared with healthy individuals with incomplete and CRBBB. These differences relate to the spatial location of the end conduction delay (right superior and posterior quadrant in the BrS group) and the morphology, size, and velocity of inscription of afferent and efferent limbs of the T loop (circular, small, of symmetrical limbs) and with a 1:1 length/width ratio. [ABSTRACT FROM PUBLISHER]

Aims The aim of this study was to assess the prognostic importance of the spatial QRS-T angle for fatal and non-fatal cardiac events.Methods and results Electrocardiograms (ECGs) were recorded in 6134 men and women aged 55 years and over from the prospective population-based Rotterdam Study. Spatial QRS-T angles were categorized as normal, borderline or abnormal. Using Cox's proportional hazards model, abnormal angles showed increased hazard ratios of cardiac death (age-and sex-adjusted hazard ratio 5.2 (95% CI 4.0–6.8)), non-fatal cardiac events (2.2 (1.5–3.1)), sudden death (5.6 (3.7–8.5)) and total mortality (2.3 (2.0–2.7)). None of the classical cardiovascular and ECG predictors provided larger hazard ratios. After adjustment for these predictors, the association of abnormal spatial QRS-T angles with all fatal study endpoints remained strong, but the association with non-fatal cardiac events disappeared. Computation of Akaike's information criterion showed that the angle contributed significantly to the prediction of all fatal endpoints by classical cardiovascular and ECG predictors.Conclusion The spatial QRS-T angle is a strong and independent predictor of cardiac mortality in the elderly. It is stronger than any of the classical cardiovascular risk factors and ECG risk indicators and provides additional value to them in predicting fatal cardiac events. [ABSTRACT FROM PUBLISHER]

Some studies provide a link between the width of QRS complexes and late potentials occurring at the end of the QRS complex in signal-averaged recordings. The purpose of this study was to compare three methods of QRS duration measurement: the conventional 12 lead ECG. the Frank vectorcardiogram (VCG) and the signal-averaged electrocardiogram. The recordings were made at a similar time in 121 consecutive patients with the Cardionics PC-based system (ECG and VCG) and the ardionics high resolution ECG, based on methods described by Simson. Patients with bundle branch block were excluded. All patients had presented a myocardial infarction and were studied either for spontaneous ventricular arrhythmias or systematically 3 to 6 weeks after an acute myocardial infarction. The signal-averaged ECG and VCG QRS durations were similar in 41 patients without inducible ventricular arrhythmias and with normal signal-averaged ECG but were longer (<0·001) than the conventional ECG QRS duration. In 36 patients with spontaneous and inducible ventricular tachyarrhythmias, the QRS duration was significantly longer on signal-averaged ECG than on VCG (<0·05) and longer on VCG than on conventional ECG (<0·05). The QRS duration was also significantly (<0·001) longer with the three techniques in patients with spontaneous ventricular tachycardia (VT) than in patients without spontaneous and inducible VT. A QRS duration on VCG ≥ 110 ms and on conventional ECG ≥ 100 ms had a sensitivity of 93% and 77% and a specificity of 83% and 85% respectively for predicting an abnormal signal-averaged ECG. In conclusion, the measurement of QRS duration with the conventional ECG, VCG or the signal-averaged ECG could be a simple method to detect the patients with myocardial infarction prone to VT. [ABSTRACT FROM PUBLISHER]

Twelve patients with double-chambered right ventricles were investigated to determine the significance of the electrocardiogram and vectorcardiogram in the evaluation of this condition. Two subgroups of individuals having various forms of obstruction to right ventricular outflow with and without intracardiac shunting were utilized as controls. The electrocardiogram of patients with double-chambered right ventricle had a characteristic appearance identifiable as a right ventricular hypertrophy pattern seen best in the extreme right precordial leads VR–VR with tendency to normalization of pattern in V, which contrasted with the pattern in both control subgroups. The vectorcardiogram in all 8 cases of double-chambered right ventricle in which this study was performed exhibited homogeneity of loop appearance and direction best identifiable in the horizontal plane by a prominent terminal orientation of the loop rightward and posteriorly. Both control subgroups exhibited heterogeneity of loop conformation, significantly more initial right-anterior force and less rightposterior force than the double-chambered right ventricle group. The electro-vectorcardiographic findings with double-chambered right ventricle were predictable for this abnormality and appear to have significant diagnostic importance. [ABSTRACT FROM PUBLISHER]