Automated Assessment of Atrioventricular Conduction in the Heart

After a pacemaker impulse passes along the atrioventricular conducting pathway of the heart, that tissue resists subsequent conduction for a time interval known as the ``effective refractory period.´´ Effective refractory period (ERP) and transit time of conducted impulses vary in response to drug, hormonal and electrical influences and may be used as indicators of the immediate physiologic state of intracardiac conduction. The traditional manual technique for measurement of ERP and conduction time consists in repeatedly adjusting a pulse generator until conduction of a stimulus of minimum interval can be observed on a chart recorder or oscilloscope. In contrast to the slow, imprecise and tedious manual method, the automated system described here provides whole graphs of ERP and conduction times as functions of external pacing interval or intervals of induced premature beats with a minimum of operator intervention. Thus, atrioventricular conduction can be conveniently assessed by machine, while the human intellect is freed to dwell on the abstractions of interpreting results and controlling the overall measurement environment.