[Non-invasive evaluation of the concealed anterograde Kent conduction in concealed WPW syndrome]

The diagnosis of concealed WPW syndrome (C-WPW) has only been made when a retrograde conduction through Kent bundle was confirmed during electrophysiological study (EPS). However, recent EPS suggested the concealed anterograde conduction through Kent bundle (CACK) during programmed electrical stimulation in C-WPW. If we could non-invasively detect an evidence of CACK during sinus rhythm (SR), it is very useful in making differential diagnosis in patients who complain paroxysms of tachycardia. High resolution ECG using signal averaging technique was recorded in 142 patients. 22 C-WPW (C), 20 AV nodal reentrant tachycardia (A), both diagnosed by EPS and 100 control subjects (N) who have no evidence of pre-excitation and no tachycardia episodes were compared. The duration of high frequency micropotentials which preceded further to the earliest upstroke of QRS complex of surface ECG (PPD) were measured. Results; (1) PPD was zero in most of N. (2) The mean PPDs were 0.97 +/- 2.08 msec (range: -4-8) in N, 1.55 +/- 2.50 msec (0-8) inA and 7.86 +/- 3.99 msec (0-19) in C, respectively (p < 0.001, C:N, C:A). (3) The rates of positive early potential, defined as 6 msec or more PPD; mean + 2SD of N, were 5/100 (5%) in N, 3/20 (15%) in A and 17/22 (77.3%) in C, respectively (p < 0.001, C:N, C:A). (4) In some of C, who showed long PPD, CACK was documented during EPS. The presence of high frequency micropotentials in C suggests that CACK may exist and produced small amounts of pre-excitation even during SR.(ABSTRACT TRUNCATED AT 250 WORDS)