A second zone of compensation during atrial premature stimulation: evidence for decremental conduction in the sinoatrial junction

The values and limitations of deductive analysis and electrophysiological testing in patients with sinoatrial arrhythmias

We reviewed the values and the limitations of deductive analysis and electrophysiological testing of sinoatrial arrhythmias (SAA). Both methods have a place in the evaluation of SAA and are complementary. Careful analysis of the surface ECG and the response of the sinus node to various tachyarrhythmias and to atrial premature beats can provide important information about the automaticity of the sinus node and sinoatrial and atriosinus conduction. Because of the sporadic nature of some SAA, the surface ECG sometimes must be supplemented by ambulatory ECG recording. This approach improves one's ability to analyze the underlying mechanism and it can also clarify the relation between the SAA and the patient's symptoms. Electrophysiological testing can be employed to reproduce certain SAA and to assess the effects of various drugs on sinus node function. This approach is superior to deductive analysis in the identification of some sinoatrial conduction abnormalities and sinus node reentry. Among the disadvantages of electrophysiological testing are its invasive character and the fact that normal electrophysiological results do not exclude sinus node dysfunction. A definitive clarification of the underlying mechanism of SAA requires direct recording of the sinus node electrogram.