Reflections on reentry and focal activity.

Initiation and maintenance of reentrant arrhythmias, such as ventricular tachycardia and fibrillation in the acute phase of myocardial ischemia, may be due to different mechanisms. The characteristics of circus movement reentry, both with and without involvement of an anatomic obstacle, are discussed. The concept of wavelength of a reentrant circuit as calculated by the product of refractory period and conduction velocity is emphasized.

"Torsade de pointes" tachycardia. Re-entry or focal activity?

Paroxysms of ventricular tachycardia in which the amplitude and the direction of QRS complexes change periodically are defined as "torsade de pointes" tachycardias. The mechanism of this atypical ventricular arrhythmia has not yet been elucidated. The aim of our study was to induce "torsade de pointes" tachycardia experimentally, in order to gain insight into its possible mechanism.

Therapeutic pacing in tachyarrhythmias by implanted pacemakers.

Termination of tachyarrhythmias by electrical stimulation has been demonstrated by clinical and experimental evidence. Implantable devices for repetitive use in long-term therapy are so far not readily available. Twelve patients with drug resistant ventricular (3) or supraventricular (accessory pathway (2), atrial flutter (3), junctional tachycardia (3), supraventricular tachycardia (1) tachyarrhythmias are reported in whom, after electrophysiological analysis of the individual tachycardia, a specially designed stimulation system was implanted.