[New energy sources for ablative methods]. / Nouvelles sources d'énergie dans les méthodes ablatives.

Radiofrequency current is the reference energy source for endocavitary ablation of arrhythmias. It is particularly well adapted for the ablation of focal arrhythmogenic substrates such as accessory pathways or foyers of automatism. Technological advances have made the lesions larger but the extension of the indications of percutaneous ablation to more complex substrates such as atrial fibrillation have justified the evaluation of alternative energies. The production of linear transmural lesions or deeper lesions which respect the parietal myocardial architecture and endocardial structure are a challenge for these energies. The capacity of functional mapping specific to cryogenics has provided this energy source with a clinical application for ablation of high risk structures whereas other energies, despite the chronicity of their experimental evaluation, are still at the stage of preliminary clinical trials with the sophisticated catheters in special indications.

[Arrhythmic cardiomyopathy]. / Cardiomyopathie rythmique.

Arrhythmic cardiomyopathy (ACM) is a clinical entity which can be reproduced in experimental models and which corresponds to all myocardial changes induced by chronic tachycardia. It may affect the atria and/or ventricles and, in this case, occur with all types of arrhythmia. Arrhythmia complicating a cardiomyopathy is the differential diagnosis of ventricular ACM. Nevertheless, the potential deleterious haemodynamic changes of any chronic arrhythmia may aggravate pre-existing ventricular dysfunction and, therefore, should always be considered. The development of ACM is usually progressive and depends on the heart rate, but there may also be a myocardial predisposition in certain cases. ACM is an association of haemodynamic, electrophysiological, metabolic and histological changes. Regression, which is the rule, starts in the first days following control of the ventricular rhythm but continues clinically over several months. The physiopathological mechanisms of ACM are multiple and include essentially abnormal cellular calcium concentrations. The treatment is optimally the restoration and maintenance of sinus rhythm, or at least control of the ventricular rate. Because of its curative effects, selective radiofrequency ablation of the arrhythmogenic substrate is the treatment of choice when this is localised. In chronic atrial fibrillation, when sinus rhythm cannot be maintained, the control of the ventricular response at rest and on exercise depends on pharmacological treatment, and, when ineffective, on radiofrequency modification of atrioventricular conduction with optimisation of the pacing mode.

[Validation of the measurement of cardiac output by acoustic quantification in patients with severe congestive heart failure]. / Validation de la mesure du débit cardiaque par la méthode de quantification acoustique chez le patient insuffisant cardiaque sévère.

The technique of acoustic quantification (AQ), because of its automatic detection of the contours, enables left ventricular volumes to be calculated in real time using the technique of disk summation. The objective of the study was to evaluate the reliability of cardiac output (CO) measurements obtained with AQ based on left ventricle volumes in patients with severe congestive heart failure. Seventeen patients, mean age 68 +/- 11 years, NYHA stage IV, in sinus rhythm and without significant valve regurgitation were enrolled prospectively. CO, measured simultaneously by 2-dimensional echocardiography (2DE), pulsed Doppler echocardiography (DOP) and AQ, was compared to the thermodilution technique (TD) data. CO, measured by AQ, was highly correlated with TD (r = 0.875; p < 0.001) with a small bias (-0.05 l/min). DOP and 2DE were also well correlated with TD (r = 0.835 and r = 0.701, respectively). Concerning ventricular volume measurement, AQ was well correlated with 2DE (for telediastolic, r = 0.892, and telesystolic volumes, r = 0.874). However, telesystolic (bias, +36.6 +/- 35 ml) and telediastolic volumes (bias, +35.6 +/- 35 ml) were overestimated. We conclude that AQ is a reliable technique, able to estimate CO precisely in patients with severe congestive heart failure. On the other hand, both telesystolic and telediastolic volumes were overestimated.

Biventricular pacing in severe heart failure patients reverses electromechanical dyssynchronization from apex to base.

Biventricular (BV) pacing is an emerging treatment for patients with severe dilated cardiomyopathy and ventricular asynchrony. Radionuclide angioscintigraphy has shown that BV can reduce activation delays between left (LV) and right ventricles (RV), but alterations of electromechanical asynchrony between the LV base and apex have not been previously described. Radionuclide angioscintigraphy with Tc99m red cell labeling was performed in 21 patients, 64 +/- 17 years of age, in NYHA functional Class III or IV, and with a mean QRS duration of 180 +/- 15 ms. Right (RVEF) and LV ejection fraction (LVEF), and the synchronization between LV apex and base (Tab) in the left lateral view, were measured by a phase analysis program (1) at baseline, (2) on day 8 after BV pacemaker implantation (D8), and (3) at 12-month follow-up in BV (M12). BV pacing reversed Tab from 42 +/- 47 ms at baseline to -57 +/- 75** on D8, and -37 +/- 76** on M12. LVEF increased from 17.8 +/- 6.3% to 19.9 +/- 8.3 on D8, and 24.2 +/- 10.8* on M12, and RVEF increased from 27.6 +/- 16% to 29.9 +/- 16 on D8 and 34.1 +/- 12.1* on M12 (*P < 0.05, **P < 0.001). A close correlation was found between early LV apex-to-base resynchronization induced by BV and late increase in LVEF (r = 0.59**). In parallel with its known interventricular resynchronization effect, BV pacing reverses the apex-to-base ventricular activation sequence, causing early contraction of the LV base followed by the apex. These changes persisted up to 12 months along with an improvement in LV systolic function.