Automatic methods for detection of tachyarrhythmias by antitachycardia devices

Electrical devices play an increasingly important role in the control of tachyarrhythmias. Antitachycardia pacing and automatic defibrillation have been severely limited by the poor specificity of tachycardia discrimination in commercially available devices. Although absolute heart rate has been the principal means of automatic diagnosis, several new detection algorithms and methods are being investigated. Multiple electrode timing comparison, signal processing and pattern recognition are employed in these newer techniques. Although each offers some improvement over present technology, none is capable of identifying all arrhythmias. The methods employing comparison of atrial and ventricular rates, without additional criteria, are unable to detect ventricular tachycardia in the presence of 1:1 retrograde conduction. Electrographic analysis techniques require very stable electrodes and may not tolerate normal morphologic variations. A combination of two or more approaches may ultimately be required. All techniques will require that certain critical variables be programmable to allow for individualization in each clinical situation. Software-controllable devices and those capable of sensing from both the atria and the ventricles will provide the sophistication necessary for the implementation of complex tachycardia detection algorithms. This report reviews automatic tachycardia detection techniques in current use and under investigation.