Sensitivity and specificity of programmed atrial stimulation for induction of supraventricular tachycardias

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Abstract
The sensitivity and specificity of two programmed atrial stimulation protocols were studied in 92 consecutive patients undergoing electrophysiologic studies both with (35 patients) and without (57 patients) clinical supraventricular arrhythmias. Protocol I (P I) consisted of incremental atrial pacing to 2:1 atrioventricular (AV) block and a single atrial extrastimulus scanned by 10 ms decrements through diastole to the atrial effective refractory period at a single drive-cycle length. Protocol II (P II) included a second atrial extrastimulus scanned by 10 ms decrements through diastole at a single drive-cycle length with the first extrastimulus set 20 ms from the atrial effective refractory period. Rapid atrial pacing at cycle lengths of 350, 300, and 250 ms was then performed with PII. P I was employed in all patients while P II was studied in the final 48 patients only. Of the 35 patients with clinical atrial arrhythmias, 26 (74%) of their arrhythmias were induced with either P I (18/35; sensitivity = 51%) and/or P II (12/17; sensitivity = 71%). Of the 57 patients without clinical atrial arrhythmias (control group), atrial arrhythmias were induced in 11 (19%), 3 with PI (specificity 95%, 54/57) and 8 with P II (specificity 74%, 23/31). The sensitivity of P II was higher (71%), but its specificity was lower (74%) than P I (51% and 95%, respectively; p>0.05). The positive predictive value of P II was lower (60%) than that of P I (86%) (p>0.05), but the negative predictive value (82%) and predictive accuracy (73%) were comparable to those of P I (76% and 78%, respectively). In conclusion, protocol II (P II) including double extrastimuli and rapid atrial pacing can enhance sensitivity of programmed atrial stimulation in inducing atrial tachyarrhythmias, but results in lower specificity when compared to protocol I (P I).