A quantitative description of normal AV nodal conduction curve in man

The AV nodal conduction curve generated by the atrial extrastimulus technique has been described only qualitatively in man, making clinical comparison of known normal curves with those of suspected AV nodal dysfunction difficult. Also, the effects of physiological and pharmacological interventions have not been quantifiable. In 50 patients with normal AV conduction as defined by normal AH (<130 ms), normal AV nodal effective and functional refractory periods (<380 and <500 ms), and absence of demonstrable dual AV nodal pathways, the authors found that conduction curves (at sinus rhythm or longest paced cycle length) can be described by an exponential equation of the form Δ = Ae(-Bx). In this equation, Δ is the increase in AV nodal conduction time of an extrastimulus compared to that of a regular beat and x is extrastimulus interval. The natural logarithm of this equation is linear in the semilogarithmic plane, thus permitting the constants A and B to be easily determined by a least squares regression analysis with a hand calculator.