6. AVNRT: Electrophysiological Aspects and Ablation Results

Objective Establish if the nodal conduction velocity is different if the impulse comes from the left atrium in relation to the right. Methods Twenty patients submitted to an electrophysiological study for different reasons were paced during sinus rhythm with an S1 series followed by six test stimuli emulating the beginning of a supraventricular tachycardia. Identical stimuli sets were given in the coronary sinus and the high right atrium. We then considered the Sx-Hx interval. Results The mean Sx-Hx interval stimulating the right atrium was 220 ±37, vs. 170 ±35 ms (p<0.0003) when the stimulus was in the coronary sinus, which represents a 29% difference. Effective (222 ±49 vs. 230 ±40 ms.) and functional (314 ±53 vs. 320±54 ms.) refractory periods were similar from both atria. Comparing conduction curves to find refractory periods, the S2-H2 interval pacing in the coronary sinus was 27.4% shorter than that from the high right atrium. Comparing anatomical distances in an anatomical piece, both distances were similar (65 ±5 mm). Conclusions Nodal conduction is significantly faster (30%) if the impulse comes from the left atrium compared to the right.