PMC3004171_01
ECG during onset of paroxysmal tachycardia, it's difficult to classify its mechanism whether is AVRT or AVNRT. Abbreviations: AVRT=atrioventricular reentry tachycardia; AVNRT=atrioventricular nodal reentry tachycardia.
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Electrocardiogram (ECG) showed no abnormity under sinus rhythm; on paroxysmal tachycardia outburst [Figure 1], narrow QRS complex presenting together with heart rate (HR) 178/ min, interval from QRS wave to P wave (RP interval) was 120ms and RP interval < PR interval (interval from P wave to QRS wave).
Before ablation, right atrial programmed S1S2 at 500/280 ms induced a narrow QRS complex tachycardia, atrioventricular conduction prolonged only 15ms when S2 decreased from 290 ms to 280 ms, not accompanied by atrioventricular conduction jump phenomenon; and V and A did not interfused during tachycardia. The reentry started from slow retrograde conduction. These properties did not propose conventional AVNRT tachycardia. Abbreviations: PSVT=paroxysmal supraventricular tachycardia; CS1-4=coronary sinus electrograms from distal to proximal; ABL=electrogram recorded by ablating catheter; RVa=electrogram recorded by right ventricle apex catheter; ms (or msec)=millisecond; BPM=beats per second; V=ventricular wave; A=atrial wave; other abbreviations as in Figure 1.
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Intracardiac electrophysiological examination: right atrial programmed basic stimulus coupled with cycle length decreasing extrastimulus (S1S2) at 500/280ms induced a narrow QRS complex tachycardia, but it was not accompanied by atrioventricular conduction jump phenomena [Figure 2].
Tachycardia could not be terminated by ventricular premature beat; This did not propose the AVRT mechanism. Abbreviations as in Figure 1 and Figure 2.
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Tachycardia could not be terminated by ventricular premature beat [Figure 3].
After a certain time of ablation, under almost the same condition of right atrial programmed S1S2 at 550/270 ms as before ablation (500/280 ms), atrioventricular conduction jump phenomenon occurred (78ms prolonged), and the same paroxysmal tachycardia induced. This suggested that the reentry started from antegrade slow conduction.
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Subsequent repeated electrophysiological examination showed that under almost the same condition, right atrial programmed S1S2 at 550/270 ms induced atrioventricular conduction jump phenomenon, and the same paroxysmal tachycardia been induced [Figure 4].