Classification of supraventricular tachycardias.

An ideal approach to classification of supraventricular arrhythmias would be based on exact knowledge of the pathophysiology and mechanism of the arrhythmia. Unfortunately, the mechanism may not be apparent from electrocardiographic data or indeed may not be known after extensive invasive and non-invasive studies. Difficulties are encountered in applying and extrapolating to patients criteria that are known to exist in experimental preparations. The traditional methods of classification have used electrocardiographic features and atrial rate. Although such classifications are simple, the criteria are arbitrary and electrocardiographically similar arrhythmias may have different mechanisms. A realistic classification must incorporate both electrocardiographic description and mechanism. The classification should be such that it can readily incorporate new knowledge in an additive way without completely restructuring the classification. A classification fulfilling these requirements would begin with electrocardiographic descriptors and end with mechanism, known or unknown. For example, a tachycardia may be characterized as supraventricular, atrial rate 300, 1:1 atrioventricular relation, with atrioventricular nodal reentry mechanism. It could then be qualified by further clinical descriptors such as incessant, paroxysmal or repetitive. With this approach, the initial descriptive category will always be constant and the mechanism known or unknown. As more data are obtained in future years, the "mechanism" segment of the descriptor may be added or revised.