G. Dakos

Left ventricular function in elite rowers in relation to training‐induced structural myocardial adaptation

To examine left ventricular (LV) function in elite young athletes in relation to structural adaptation to prolonged intense training. Conventional echocardiography and tissue Doppler imaging (TDI) were performed in 15 elite rowers and 12 sedentary matched controls. Rowers had increased LV mass index, septal (12 vs 10 mm, P<0.005) and posterior wall thicknesses (12 vs 9 mm, P<0.001) and increased relative wall thickness. Septal and lateral systolic velocities were enhanced in rowers (septal Sm=8.5 vs 6.3 cm/s, P<0.001; lateral Sm=11.4 vs 8.0 cm/s, P<0.005), representing a 35% and 42% increase, respectively. Similarly, septal and lateral early diastolic velocities were enhanced (septal Em=12.1 vs 9.5 cm/s, P<0.01; lateral Em=16.6 vs 11.6 cm/s, P<0.001), representing a 27% and 43% increase, respectively. Systolic and early diastolic TDI velocities of the lateral wall showed a positive correlation (r=0.65, P<0.01) in athletes indicating a parallel improvement of systolic and diastolic function, while LV stiffness was decreased [(E/Em)/(LV end‐diastolic diameter)=1.13 vs 1.57, P<0.005). Both systolic and diastolic LV function were improved in elite rowers, despite a pattern of concentric hypertrophy.

QRS analysis using wavelet transformation for the prediction of response to cardiac resynchronization therapy: a prospective pilot study.

BACKGROUND Wider QRS and left bundle branch block morphology are related to response to cardiac resynchronization therapy (CRT). A novel time-frequency analysis of the QRS complex may provide additional information in predicting response to CRT. METHODS Signal-averaged electrocardiograms were prospectively recorded, before CRT, in orthogonal leads and QRS decomposition in three frequency bands was performed using the Morlet wavelet transformation. RESULTS Thirty eight patients (age 65±10years, 31 males) were studied. CRT responders (n=28) had wider baseline QRS compared to non-responders and lower QRS energies in all frequency bands. The combination of QRS duration and mean energy in the high frequency band had the best predicting ability (AUC 0.833, 95%CI 0.705-0.962, p=0.002) followed by the maximum energy in the high frequency band (AUC 0.811, 95%CI 0.663-0.960, p=0.004). CONCLUSIONS Wavelet transformation of the QRS complex is useful in predicting response to CRT.

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

AIMS 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. METHODS AND RESULTS 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. CONCLUSION 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.

Practice patterns of cardiologists, general practitioners, and internists for managing supraventricular tachycardias in Greece

Objectives Supraventricular tachycardias (SVT) often lead to emergency room and primary care visits. Not only cardiologists, but also general practitioners (GPs) and internists are involved to an increasing extent in the acute and long-term management of SVT. We aimed to explore the differences between practice patterns of cardiologists and noncardiologists with regard to SVT management in Greece. Methods A cross-sectional questionnaire survey was conducted among 250 cardiologists and 250 GPs/internists from various areas across Greece. Results A response rate of 61.8% was obtained. Vagal maneuvers were the initial therapeutic approach for SVT termination; however, 22% of noncardiologists would rather start with an antiarrhythmic drug. Adenosine was the most popular drug for SVT termination, but the GPs/internists would use it less often than the cardiologists (67 vs. 86%, P<0.001). The GPs/internists would keep the patient for at least 24 h or more after SVT termination, while 48% of the cardiologists would discharge the patient within the first 3 h. Noncardiologists would more often suggest a 24-h Holter recording than the cardiologists (73 vs. 55%, P<0.005). With regard to the long-term management of SVT, the GPs/internists would prescribe antiarrhythmic drugs earlier than the cardiologists, and seem to be less familiar with the indications for the electrophysiological testing and ablation. Conclusion Significant differences in practice patterns exist in Greece with regard to SVT management between cardiologists and noncardiologists. The GPs/internists seem to rely more on antiarrhythmic drugs and tend to underestimate the role of ablation therapy for the long-term management of SVT.

Beat to beat wavelet variability in atrial fibrillation

Atrial fibrillation (AF) is a complex phenomenon, related with a multitude of factors, including the electrical properties of the atrial substrate. The purpose of this work is to present a method that highlights electrocardiographic differences between normal subjects and patients with paroxysmal AF episodes (PAF), potentially related with substrate differences. Vectorcardiography recordings are considered and, for each lead (X-Y-Z), on a beat by beat basis, a steady window before QRS, corresponding to the atrial activity, is analysed via continuous wavelet transform. Wavelet-based parameters are calculated and compared between the normal and AF group, with the beat to beat variation of wavelet energy as the most important feature showing a significantly higher variability in the AF group.

Analysis of atrial fibrillation after CABG using wavelets

In the present study, Wavelet analysis of P wave for the prediction of Atrial Fibrillation after CABG is evaluated. Continuous Wavelet Transform is applied to ECG and Mean/Max parameters are calculated within the P window for different frequency bands. Thus, 24 parameters are available, which, along with the 4 window lengths (corresponding to P wave length of X, Y, Z, V signals), make a pool of available parameters to be used for classification. Linear regression is used for the classification of the two groups and bootstrapping is applied in order to enhance statistical robustness. The features to be used in the regression model are selected from the pool of available parameters by use of an iterative procedure. The outcome of the feature selection procedure shows that X and Z-axis features as well as vector-magnitude features are the most important ones for the prediction of Atrial Fibrillation after CABG.

Two dimensional wavelet energy analysis on a beat to beat basis: Application to Atrial Fibrillation

Atrial Fibrillation (AF) is a condition in which heart rhythm is not associated with normal sinoatrial (SA) node pacemaker but it derives from different areas on the atrium, often from the area of Pulmonary veins (PVs) A way to eliminate the influence of PVs in the inducement of AF is the PVs isolation surgery. In this study, an effort is made towards investigating the morphology and dynamics of P-waves, when the potentially arrhythmogenic tissue in PVs is involved or isolated via ablation. For this reason, 20 patients who were subjected to PVs isolation were studied, via vectrorcardiography recordings obtained before and after the ablation. Wavelet energies for five frequency bands were analyzed, using a two dimensional representation. The proposed technique was applied for the analysis of wavelet energies in consecutive beats, and their correlation with the RR interval. Features for the evaluation of those plots were extracted, such as the axes of a fitted to the plot ellipse and the center of the mass. The statistical analysis demonstrated significant differences between the groups, which imply the modification of the atrial substrate concerning electrical conduction toward to a more stable condition.

Wavelet variability of SA node originated P waves in atrial fibrillation and in signals with ectopic beats

Atrial fibrillation (AF) is one of the most common cardiac arrhythmia [1]. Electrical properties of the atrial myocardium may be related to the appearance of this type of arrhythmia. However ectopic beats, occurring normally in healthy people, disturb cardiac rhythm. Those beats arise from fiber outside the region of SA node. With this work we aim at highlighting differences in the atrial activity between healthy subjects, healthy subjects presenting many ectopic events and patients with AF. The X-Y-Z leads of vectorcardiography recordings are considered. Wavelet-based parameters are extracted from a window which represents atrial activity originated from SA node and compared between signals of the three groups. Results show differences potentially related to the conduction system of the atrium between healthy people and people with AF, as well as between healthy people and people with ectopic events. No difference was found from the analysis of SA node beats between people with AF and healthy with ectopic events.

Cardiac arrest caused by torsades de pointes tachycardia after successful atrial flutter radiofrequency catheter ablation.

A 66-year-old woman underwent successful radiofrequency catheter ablation for long-lasting, drug refractory fast atrial flutter. Two days later she had a cardiac arrest due to torsades de pointes (TdP) tachycardia attributed to relative sinus bradycardia and QT interval prolongation. After successful resuscitation further episodes of TdP occurred, which were treated with temporary pacing. Because of concomitant systolic dysfunction due to ischemic and valvular heart disease she was finally treated with an implantable defibrillator. In conclusion we strongly advise prolonged monitoring for 2 or more days for patients with structural heart disease following successful catheter ablation for long lasting tachyarrhythmias.